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Python News
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What's New in Python 3.10.5 final?
==================================

*Release date: 2022-06-06*

Core and Builtins
-----------------

- gh-issue-93418: Fixed an assert where an f-string has an equal sign '='
  following an expression, but there's no trailing brace. For example,
  f"{i=".

- gh-issue-91924: Fix ``__ltrace__`` debug feature if the stdout encoding is
  not UTF-8. Patch by Victor Stinner.

- gh-issue-93061: Backward jumps after ``async for`` loops are no longer
  given dubious line numbers.

- gh-issue-93065: Fix contextvars HAMT implementation to handle iteration
  over deep trees.

  The bug was discovered and fixed by Eli Libman. See
  `MagicStack/immutables#84
  <https://github.com/MagicStack/immutables/issues/84>`_ for more details.

- gh-issue-92311: Fixed a bug where setting ``frame.f_lineno`` to jump over
  a list comprehension could misbehave or crash.

- gh-issue-92112: Fix crash triggered by an evil custom ``mro()`` on a
  metaclass.

- gh-issue-92036: Fix a crash in subinterpreters related to the garbage
  collector. When a subinterpreter is deleted, untrack all objects tracked
  by its GC. To prevent a crash in deallocator functions expecting objects
  to be tracked by the GC, leak a strong reference to these objects on
  purpose, so they are never deleted and their deallocator functions are not
  called. Patch by Victor Stinner.

- gh-issue-91421: Fix a potential integer overflow in _Py_DecodeUTF8Ex.

- bpo-47212: Raise :exc:`IndentationError` instead of :exc:`SyntaxError` for
  a bare ``except`` with no following indent. Improve :exc:`SyntaxError`
  locations for an un-parenthesized generator used as arguments. Patch by
  Matthieu Dartiailh.

- bpo-47182: Fix a crash when using a named unicode character like
  ``"\N{digit nine}"`` after the main interpreter has been initialized a
  second time.

- bpo-46775: Some Windows system error codes(>= 10000) are now mapped into
  the correct errno and may now raise a subclass of :exc:`OSError`. Patch by
  Dong-hee Na.

- bpo-47117: Fix a crash if we fail to decode characters in interactive mode
  if the tokenizer buffers are uninitialized. Patch by Pablo Galindo.

- bpo-39829: Removed the ``__len__()`` call when initializing a list and
  moved initializing to ``list_extend``. Patch by Jeremiah Pascual.

- bpo-46962: Classes and functions that unconditionally declared their
  docstrings ignoring the `--without-doc-strings` compilation flag no longer
  do so.

  The classes affected are :class:`ctypes.UnionType`,
  :class:`pickle.PickleBuffer`, :class:`testcapi.RecursingInfinitelyError`,
  and :class:`types.GenericAlias`.

  The functions affected are 24 methods in :mod:`ctypes`.

  Patch by Oleg Iarygin.

- bpo-36819: Fix crashes in built-in encoders with error handlers that
  return position less or equal than the starting position of non-encodable
  characters.

Library
-------

- gh-issue-93156: Accessing the :attr:`pathlib.PurePath.parents` sequence of
  an absolute path using negative index values produced incorrect results.

- gh-issue-89973: Fix :exc:`re.error` raised in :mod:`fnmatch` if the
  pattern contains a character range with upper bound lower than lower bound
  (e.g. ``[c-a]``). Now such ranges are interpreted as empty ranges.

- gh-issue-93010: In a very special case, the email package tried to append
  the nonexistent ``InvalidHeaderError`` to the defect list. It should have
  been ``InvalidHeaderDefect``.

- gh-issue-92839: Fixed crash resulting from calling bisect.insort() or
  bisect.insort_left() with the key argument not equal to None.

- gh-issue-91581: :meth:`~datetime.datetime.utcfromtimestamp` no longer
  attempts to resolve ``fold`` in the pure Python implementation, since the
  fold is never 1 in UTC. In addition to being slightly faster in the common
  case, this also prevents some errors when the timestamp is close to
  :attr:`datetime.min <datetime.datetime.min>`.  Patch by Paul Ganssle.

- gh-issue-92530: Fix an issue that occurred after interrupting
  :func:`threading.Condition.notify`.

- gh-issue-92049: Forbid pickling constants ``re._constants.SUCCESS`` etc.
  Previously, pickling did not fail, but the result could not be unpickled.

- bpo-47029: Always close the read end of the pipe used by
  :class:`multiprocessing.Queue` *after* the last write of buffered data to
  the write end of the pipe to avoid :exc:`BrokenPipeError` at garbage
  collection and at :meth:`multiprocessing.Queue.close` calls. Patch by Géry
  Ogam.

- gh-issue-91401: Provide a fail-safe way to disable :mod:`subprocess` use
  of ``vfork()`` via a private ``subprocess._USE_VFORK`` attribute. While
  there is currently no known need for this, if you find a need please only
  set it to ``False``. File a CPython issue as to why you needed it and link
  to that from a comment in your code. This attribute is documented as a
  footnote in 3.11.

- gh-issue-91910: Add missing f prefix to f-strings in error messages from
  the :mod:`multiprocessing` and :mod:`asyncio` modules.

- gh-issue-91810: :class:`~xml.etree.ElementTree.ElementTree` method
  :meth:`~xml.etree.ElementTree.ElementTree.write` and function
  :func:`~xml.etree.ElementTree.tostring` now use the text file's encoding
  ("UTF-8" if not available) instead of locale encoding in XML declaration
  when ``encoding="unicode"`` is specified.

- gh-issue-91832: Add ``required`` attribute to :class:`argparse.Action`
  repr output.

- gh-issue-91734: Fix OSS audio support on Solaris.

- gh-issue-91700: Compilation of regular expression containing a conditional
  expression ``(?(group)...)`` now raises an appropriate :exc:`re.error` if
  the group number refers to not defined group. Previously an internal
  RuntimeError was raised.

- gh-issue-91676: Fix :class:`unittest.IsolatedAsyncioTestCase` to shutdown
  the per test event loop executor before returning from its ``run`` method
  so that a not yet stopped or garbage collected executor state does not
  persist beyond the test.

- gh-issue-90568: Parsing ``\N`` escapes of Unicode Named Character
  Sequences in a :mod:`regular expression <re>` raises now :exc:`re.error`
  instead of ``TypeError``.

- gh-issue-91595: Fix the comparison of character and integer inside
  :func:`Tools.gdb.libpython.write_repr`. Patch by Yu Liu.

- gh-issue-90622: Worker processes for
  :class:`concurrent.futures.ProcessPoolExecutor` are no longer spawned on
  demand (a feature added in 3.9) when the multiprocessing context start
  method is ``"fork"`` as that can lead to deadlocks in the child processes
  due to a fork happening while threads are running.

- gh-issue-91575: Update case-insensitive matching in the :mod:`re` module
  to the latest Unicode version.

- gh-issue-91581: Remove an unhandled error case in the C implementation of
  calls to :meth:`datetime.fromtimestamp <datetime.datetime.fromtimestamp>`
  with no time zone (i.e. getting a local time from an epoch timestamp).
  This should have no user-facing effect other than giving a possibly more
  accurate error message when called with timestamps that fall on
  10000-01-01 in the local time. Patch by Paul Ganssle.

- bpo-47260: Fix ``os.closerange()`` potentially being a no-op in a Linux
  seccomp sandbox.

- bpo-39064: :class:`zipfile.ZipFile` now raises :exc:`zipfile.BadZipFile`
  instead of ``ValueError`` when reading a corrupt zip file in which the
  central directory offset is negative.

- bpo-47151: When subprocess tries to use vfork, it now falls back to fork
  if vfork returns an error. This allows use in situations where vfork isn't
  allowed by the OS kernel.

- bpo-27929: Fix :meth:`asyncio.loop.sock_connect` to only resolve names for
  :const:`socket.AF_INET` or :const:`socket.AF_INET6` families. Resolution
  may not make sense for other families, like :const:`socket.AF_BLUETOOTH`
  and :const:`socket.AF_UNIX`.

- bpo-43323: Fix errors in the :mod:`email` module if the charset itself
  contains undecodable/unencodable characters.

- bpo-47101: :const:`hashlib.algorithms_available` now lists only algorithms
  that are provided by activated crypto providers on OpenSSL 3.0. Legacy
  algorithms are not listed unless the legacy provider has been loaded into
  the default OSSL context.

- bpo-46787: Fix :class:`concurrent.futures.ProcessPoolExecutor` exception
  memory leak

- bpo-45393: Fix the formatting for ``await x`` and ``not x`` in the
  operator precedence table when using the :func:`help` system.

- bpo-46415: Fix ipaddress.ip_{address,interface,network} raising TypeError
  instead of ValueError if given invalid tuple as address parameter.

- bpo-28249: Set :attr:`doctest.DocTest.lineno` to ``None`` when object does
  not have :attr:`__doc__`.

- bpo-45138: Fix a regression in the :mod:`sqlite3` trace callback where
  bound parameters were not expanded in the passed statement string. The
  regression was introduced in Python 3.10 by :issue:`40318`. Patch by
  Erlend E. Aasland.

- bpo-44493: Add missing terminated NUL in sockaddr_un's length

  This was potentially observable when using non-abstract AF_UNIX datagram
  sockets to processes written in another programming language.

- bpo-42627: Fix incorrect parsing of Windows registry proxy settings

- bpo-36073: Raise :exc:`~sqlite3.ProgrammingError` instead of segfaulting
  on recursive usage of cursors in :mod:`sqlite3` converters. Patch by
  Sergey Fedoseev.

Documentation
-------------

- gh-issue-86438: Clarify that :option:`-W` and :envvar:`PYTHONWARNINGS` are
  matched literally and case-insensitively, rather than as regular
  expressions, in :mod:`warnings`.

- gh-issue-92240: Added release dates for "What's New in Python 3.X" for
  3.0, 3.1, 3.2, 3.8 and 3.10

- gh-issue-91888: Add a new ``gh`` role to the documentation to link to
  GitHub issues.

- gh-issue-91783: Document security issues concerning the use of the
  function :meth:`shutil.unpack_archive`

- gh-issue-91547: Remove "Undocumented modules" page.

- bpo-44347: Clarify the meaning of *dirs_exist_ok*, a kwarg of
  :func:`shutil.copytree`.

- bpo-38668: Update the introduction to documentation for :mod:`os.path` to
  remove warnings that became irrelevant after the implementations of
  :pep:`383` and :pep:`529`.

- bpo-47138: Pin Jinja to a version compatible with Sphinx version 3.2.1.

- bpo-46962: All docstrings in code snippets are now wrapped into
  :func:`PyDoc_STR` to follow the guideline of `PEP 7's Documentation
  Strings paragraph
  <https://www.python.org/dev/peps/pep-0007/#documentation-strings>`_. Patch
  by Oleg Iarygin.

- bpo-26792: Improve the docstrings of :func:`runpy.run_module` and
  :func:`runpy.run_path`. Original patch by Andrew Brezovsky.

- bpo-40838: Document that :func:`inspect.getdoc`,
  :func:`inspect.getmodule`, and :func:`inspect.getsourcefile` might return
  ``None``.

- bpo-45790: Adjust inaccurate phrasing in
  :doc:`../extending/newtypes_tutorial` about the ``ob_base`` field and the
  macros used to access its contents.

- bpo-42340: Document that in some circumstances :exc:`KeyboardInterrupt`
  may cause the code to enter an inconsistent state. Provided a sample
  workaround to avoid it if needed.

- bpo-41233: Link the errnos referenced in ``Doc/library/exceptions.rst`` to
  their respective section in ``Doc/library/errno.rst``, and vice versa.
  Previously this was only done for EINTR and InterruptedError. Patch by Yan
  "yyyyyyyan" Orestes.

- bpo-38056: Overhaul the :ref:`error-handlers` documentation in
  :mod:`codecs`.

- bpo-13553: Document tkinter.Tk args.

Tests
-----

- gh-issue-92886: Fixing tests that fail when running with optimizations
  (``-O``) in ``test_imaplib.py``.

- gh-issue-92670: Skip
  ``test_shutil.TestCopy.test_copyfile_nonexistent_dir`` test on AIX as the
  test uses a trailing slash to force the OS consider the path as a
  directory, but on AIX the trailing slash has no effect and is considered
  as a file.

- gh-issue-91904: Fix initialization of
  :envvar:`PYTHONREGRTEST_UNICODE_GUARD` which prevented running regression
  tests on non-UTF-8 locale.

- gh-issue-91607: Fix ``test_concurrent_futures`` to test the correct
  multiprocessing start method context in several cases where the test logic
  mixed this up.

- bpo-47205: Skip test for :func:`~os.sched_getaffinity` and
  :func:`~os.sched_setaffinity` error case on FreeBSD.

- bpo-47104: Rewrite :func:`asyncio.to_thread` tests to use
  :class:`unittest.IsolatedAsyncioTestCase`.

- bpo-29890: Add tests for :class:`ipaddress.IPv4Interface` and
  :class:`ipaddress.IPv6Interface` construction with tuple arguments.
  Original patch and tests by louisom.

Build
-----

- bpo-47103: Windows ``PGInstrument`` builds now copy a required DLL into
  the output directory, making it easier to run the profile stage of a PGO
  build.

Windows
-------

- gh-issue-92984: Explicitly disable incremental linking for non-Debug
  builds

- bpo-47194: Update ``zlib`` to v1.2.12 to resolve CVE-2018-25032.

- bpo-46785: Fix race condition between :func:`os.stat` and unlinking a file
  on Windows, by using errors codes returned by ``FindFirstFileW()`` when
  appropriate in ``win32_xstat_impl``.

- bpo-40859: Update Windows build to use xz-5.2.5

Tools/Demos
-----------

- gh-issue-91583: Fix regression in the code generated by Argument Clinic
  for functions with the ``defining_class`` parameter.


What's New in Python 3.10.4 final?
==================================

*Release date: 2022-03-23*

Core and Builtins
-----------------

- bpo-46968: Check for the existence of the "sys/auxv.h" header in
  :mod:`faulthandler` to avoid compilation problems in systems where this
  header doesn't exist. Patch by Pablo Galindo

Library
-------

- bpo-23691: Protect the :func:`re.finditer` iterator from re-entering.

- bpo-42369: Fix thread safety of :meth:`zipfile._SharedFile.tell` to avoid
  a "zipfile.BadZipFile: Bad CRC-32 for file" exception when reading a
  :class:`ZipFile` from multiple threads.

- bpo-38256: Fix :func:`binascii.crc32` when it is compiled to use zlib'c
  crc32 to work properly on inputs 4+GiB in length instead of returning the
  wrong result. The workaround prior to this was to always feed the function
  data in increments smaller than 4GiB or to just call the zlib module
  function.

- bpo-39394: A warning about inline flags not at the start of the regular
  expression now contains the position of the flag.

- bpo-47061: Deprecate the various modules listed by :pep:`594`:

  aifc, asynchat, asyncore, audioop, cgi, cgitb, chunk, crypt, imghdr,
  msilib, nntplib, nis, ossaudiodev, pipes, smtpd, sndhdr, spwd, sunau,
  telnetlib, uu, xdrlib

- bpo-2604: Fix bug where doctests using globals would fail when run
  multiple times.

- bpo-45997: Fix :class:`asyncio.Semaphore` re-aquiring FIFO order.

- bpo-47022: The :mod:`asynchat`, :mod:`asyncore` and  :mod:`smtpd` modules
  have been deprecated since at least Python 3.6. Their documentation and
  deprecation warnings and have now been updated to note they will removed
  in Python 3.12 (:pep:`594`).

- bpo-46421: Fix a unittest issue where if the command was invoked as
  ``python -m unittest`` and the filename(s) began with a dot (.), a
  ``ValueError`` is returned.

- bpo-40296: Fix supporting generic aliases in :mod:`pydoc`.


What's New in Python 3.10.3 final?
==================================

*Release date: 2022-03-16*

Core and Builtins
-----------------

- bpo-46940: Avoid overriding :exc:`AttributeError` metadata information for
  nested attribute access calls. Patch by Pablo Galindo.

- bpo-46852: Rename the private undocumented ``float.__set_format__()``
  method to ``float.__setformat__()`` to fix a typo introduced in Python
  3.7. The method is only used by test_float. Patch by Victor Stinner.

- bpo-46794: Bump up the libexpat version into 2.4.6

- bpo-46820: Fix parsing a numeric literal immediately (without spaces)
  followed by "not in" keywords, like in ``1not in x``. Now the parser only
  emits a warning, not a syntax error.

- bpo-46762: Fix an assert failure in debug builds when a '<', '>', or '='
  is the last character in an f-string that's missing a closing right brace.

- bpo-46724: Make sure that all backwards jumps use the ``JUMP_ABSOLUTE``
  instruction, rather than ``JUMP_FORWARD`` with an argument of
  ``(2**32)+offset``.

- bpo-46732: Correct the docstring for the :meth:`__bool__` method. Patch by
  Jelle Zijlstra.

- bpo-46707: Avoid potential exponential backtracking when producing some
  syntax errors involving lots of brackets. Patch by Pablo Galindo.

- bpo-40479: Add a missing call to ``va_end()`` in
  ``Modules/_hashopenssl.c``.

- bpo-46615: When iterating over sets internally in ``setobject.c``, acquire
  strong references to the resulting items from the set.  This prevents
  crashes in corner-cases of various set operations where the set gets
  mutated.

- bpo-45773: Remove two invalid "peephole" optimizations from the bytecode
  compiler.

- bpo-43721: Fix docstrings of :attr:`~property.getter`,
  :attr:`~property.setter`, and :attr:`~property.deleter` to clarify that
  they create a new copy of the property.

- bpo-46503: Fix an assert when parsing some invalid \N escape sequences in
  f-strings.

- bpo-46417: Fix a race condition on setting a type ``__bases__`` attribute:
  the internal function ``add_subclass()`` now gets the
  ``PyTypeObject.tp_subclasses`` member after calling
  :c:func:`PyWeakref_NewRef` which can trigger a garbage collection which
  can indirectly modify ``PyTypeObject.tp_subclasses``. Patch by Victor
  Stinner.

- bpo-46383: Fix invalid signature of ``_zoneinfo``'s ``module_free``
  function to resolve a crash on wasm32-emscripten platform.

- bpo-46070: :c:func:`Py_EndInterpreter` now explicitly untracks all objects
  currently tracked by the GC. Previously, if an object was used later by
  another interpreter, calling :c:func:`PyObject_GC_UnTrack` on the object
  crashed if the previous or the next object of the :c:type:`PyGC_Head`
  structure became a dangling pointer. Patch by Victor Stinner.

- bpo-46339: Fix a crash in the parser when retrieving the error text for
  multi-line f-strings expressions that do not start in the first line of
  the string. Patch by Pablo Galindo

- bpo-46240: Correct the error message for unclosed parentheses when the
  tokenizer doesn't reach the end of the source when the error is reported.
  Patch by Pablo Galindo

- bpo-46091: Correctly calculate indentation levels for lines with
  whitespace character that are ended by line continuation characters. Patch
  by Pablo Galindo

Library
-------

- bpo-43253: Fix a crash when closing transports where the underlying socket
  handle is already invalid on the Proactor event loop.

- bpo-47004: Apply bugfixes from importlib_metadata 4.11.3, including bugfix
  for EntryPoint.extras, which was returning match objects and not the
  extras strings.

- bpo-46985: Upgrade pip wheel bundled with ensurepip (pip 22.0.4)

- bpo-46968: :mod:`faulthandler`: On Linux 5.14 and newer, dynamically
  determine size of signal handler stack size CPython allocates using
  ``getauxval(AT_MINSIGSTKSZ)``. This changes allows for Python extension's
  request to Linux kernel to use AMX_TILE instruction set on Sapphire Rapids
  Xeon processor to succeed, unblocking use of the ISA in frameworks.

- bpo-46955: Expose :class:`asyncio.base_events.Server` as
  :class:`asyncio.Server`. Patch by Stefan Zabka.

- bpo-23325: The :mod:`signal` module no longer assumes that
  :const:`~signal.SIG_IGN` and :const:`~signal.SIG_DFL` are small int
  singletons.

- bpo-46932: Update bundled libexpat to 2.4.7

- bpo-25707: Fixed a file leak in :func:`xml.etree.ElementTree.iterparse`
  when the iterator is not exhausted. Patch by Jacob Walls.

- bpo-44886: Inherit asyncio proactor datagram transport from
  :class:`asyncio.DatagramTransport`.

- bpo-46827: Support UDP sockets in  :meth:`asyncio.loop.sock_connect` for
  selector-based event loops.  Patch by Thomas Grainger.

- bpo-46811: Make test suite support Expat >=2.4.5

- bpo-46252: Raise :exc:`TypeError` if :class:`ssl.SSLSocket` is passed to
  transport-based APIs.

- bpo-46784: Fix libexpat symbols collisions with user dynamically loaded or
  statically linked libexpat in embedded Python.

- bpo-39327: :func:`shutil.rmtree` can now work with VirtualBox shared
  folders when running from the guest operating-system.

- bpo-46756: Fix a bug in
  :meth:`urllib.request.HTTPPasswordMgr.find_user_password` and
  :meth:`urllib.request.HTTPPasswordMgrWithPriorAuth.is_authenticated` which
  allowed to bypass authorization. For example, access to URI
  ``example.org/foobar`` was allowed if the user was authorized for URI
  ``example.org/foo``.

- bpo-46643: In :func:`typing.get_type_hints`, support evaluating
  stringified ``ParamSpecArgs`` and ``ParamSpecKwargs`` annotations. Patch
  by Gregory Beauregard.

- bpo-45863: When the :mod:`tarfile` module creates a pax format archive, it
  will put an integer representation of timestamps in the ustar header (if
  possible) for the benefit of older unarchivers, in addition to the
  existing full-precision timestamps in the pax extended header.

- bpo-46676: Make :data:`typing.ParamSpec` args and kwargs equal to
  themselves. Patch by Gregory Beauregard.

- bpo-46672: Fix ``NameError`` in :func:`asyncio.gather` when initial type
  check fails.

- bpo-46655: In :func:`typing.get_type_hints`, support evaluating bare
  stringified ``TypeAlias`` annotations. Patch by Gregory Beauregard.

- bpo-45948: Fixed a discrepancy in the C implementation of the
  :mod:`xml.etree.ElementTree` module. Now, instantiating an
  :class:`xml.etree.ElementTree.XMLParser` with a ``target=None`` keyword
  provides a default :class:`xml.etree.ElementTree.TreeBuilder` target as
  the Python implementation does.

- bpo-46521: Fix a bug in the :mod:`codeop` module that was incorrectly
  identifying invalid code involving string quotes as valid code.

- bpo-46581: Brings :class:`ParamSpec` propagation for :class:`GenericAlias`
  in line with :class:`Concatenate` (and others).

- bpo-46591: Make the IDLE doc URL on the About IDLE dialog clickable.

- bpo-46400: expat: Update libexpat from 2.4.1 to 2.4.4

- bpo-46487: Add the ``get_write_buffer_limits`` method to
  :class:`asyncio.transports.WriteTransport` and to the SSL transport.

- bpo-45173: Note the configparser deprecations will be removed in Python
  3.12.

- bpo-46539: In :func:`typing.get_type_hints`, support evaluating
  stringified ``ClassVar`` and ``Final`` annotations inside ``Annotated``.
  Patch by Gregory Beauregard.

- bpo-46491: Allow :data:`typing.Annotated` to wrap :data:`typing.Final` and
  :data:`typing.ClassVar`. Patch by Gregory Beauregard.

- bpo-46436: Fix command-line option ``-d``/``--directory`` in module
  :mod:`http.server` which is ignored when combined with command-line option
  ``--cgi``. Patch by Géry Ogam.

- bpo-41403: Make :meth:`mock.patch` raise a :exc:`TypeError` with a
  relevant error message on invalid arg. Previously it allowed a cryptic
  :exc:`AttributeError` to escape.

- bpo-46474: In ``importlib.metadata.EntryPoint.pattern``, avoid potential
  REDoS by limiting ambiguity in consecutive whitespace.

- bpo-46469: :mod:`asyncio` generic classes now return
  :class:`types.GenericAlias` in ``__class_getitem__`` instead of the same
  class.

- bpo-46434: :mod:`pdb` now gracefully handles ``help`` when :attr:`__doc__`
  is missing, for example when run with pregenerated optimized ``.pyc``
  files.

- bpo-46333: The :meth:`__eq__` and :meth:`__hash__` methods of
  :class:`typing.ForwardRef` now honor the ``module`` parameter of
  :class:`typing.ForwardRef`. Forward references from different modules are
  now differentiated.

- bpo-46246: Add missing ``__slots__`` to
  ``importlib.metadata.DeprecatedList``. Patch by Arie Bovenberg.

- bpo-46266: Improve day constants in :mod:`calendar`.

  Now all constants (`MONDAY` ... `SUNDAY`) are documented, tested, and
  added to ``__all__``.

- bpo-46232: The :mod:`ssl` module now handles certificates with bit strings
  in DN correctly.

- bpo-43118: Fix a bug in :func:`inspect.signature` that was causing it to
  fail on some subclasses of classes with a ``__text_signature__``
  referencing module globals. Patch by Weipeng Hong.

- bpo-26552: Fixed case where failing :func:`asyncio.ensure_future` did not
  close the coroutine. Patch by Kumar Aditya.

- bpo-21987: Fix an issue with :meth:`tarfile.TarFile.getmember` getting a
  directory name with a trailing slash.

- bpo-20392: Fix inconsistency with uppercase file extensions in
  :meth:`MimeTypes.guess_type`. Patch by Kumar Aditya.

- bpo-46080: Fix exception in argparse help text generation if a
  :class:`argparse.BooleanOptionalAction` argument's default is
  ``argparse.SUPPRESS`` and it has ``help`` specified.  Patch by Felix
  Fontein.

- bpo-44439: Fix ``.write()`` method of a member file in ``ZipFile``, when
  the input data is an object that supports the buffer protocol, the file
  length may be wrong.

- bpo-45703: When a namespace package is imported before another module from
  the same namespace is created/installed in a different :data:`sys.path`
  location while the program is running, calling the
  :func:`importlib.invalidate_caches` function will now also guarantee the
  new module is noticed.

- bpo-24959: Fix bug where :mod:`unittest` sometimes drops frames from
  tracebacks of exceptions raised in tests.

- bpo-44791: Fix substitution of :class:`~typing.ParamSpec` in
  :data:`~typing.Concatenate` with different parameter expressions.
  Substitution with a list of types returns now a tuple of types.
  Substitution with ``Concatenate`` returns now a ``Concatenate`` with
  concatenated lists of arguments.

- bpo-14156: argparse.FileType now supports an argument of '-' in binary
  mode, returning the .buffer attribute of sys.stdin/sys.stdout as
  appropriate. Modes including 'x' and 'a' are treated equivalently to 'w'
  when argument is '-'. Patch contributed by Josh Rosenberg

Documentation
-------------

- bpo-46463: Fixes :file:`escape4chm.py` script used when building the CHM
  documentation file

Tests
-----

- bpo-46913: Fix test_faulthandler.test_sigfpe() if Python is built with
  undefined behavior sanitizer (UBSAN): disable UBSAN on the
  faulthandler_sigfpe() function. Patch by Victor Stinner.

- bpo-46708: Prevent default asyncio event loop policy modification warning
  after ``test_asyncio`` execution.

- bpo-46678: The function ``make_legacy_pyc`` in
  ``Lib/test/support/import_helper.py`` no longer fails when
  ``PYTHONPYCACHEPREFIX`` is set to a directory on a different device from
  where tempfiles are stored.

- bpo-46616: Ensures ``test_importlib.test_windows`` cleans up registry keys
  after completion.

- bpo-44359: test_ftplib now silently ignores socket errors to prevent
  logging unhandled threading exceptions. Patch by Victor Stinner.

- bpo-46542: Fix a Python crash in test_lib2to3 when using Python built in
  debug mode: limit the recursion limit. Patch by Victor Stinner.

- bpo-46576: test_peg_generator now disables compiler optimization when
  testing compilation of its own C extensions to significantly speed up the
  testing on non-debug builds of CPython.

- bpo-46542: Fix ``test_json`` tests checking for :exc:`RecursionError`:
  modify these tests to use ``support.infinite_recursion()``. Patch by
  Victor Stinner.

- bpo-13886: Skip test_builtin PTY tests on non-ASCII characters if the
  readline module is loaded. The readline module changes input() behavior,
  but test_builtin is not intented to test the readline module. Patch by
  Victor Stinner.

Build
-----

- bpo-47032: Ensure Windows install builds fail correctly with a non-zero
  exit code when part of the build fails.

- bpo-47024: Update OpenSSL to 1.1.1n for macOS installers and all Windows
  builds.

- bpo-38472: Fix GCC detection in setup.py when cross-compiling. The C
  compiler is now run with LC_ALL=C. Previously, the detection failed with a
  German locale.

- bpo-46513: :program:`configure` no longer uses ``AC_C_CHAR_UNSIGNED``
  macro and ``pyconfig.h`` no longer defines reserved symbol
  ``__CHAR_UNSIGNED__``.

- bpo-45925: Update Windows installer to use SQLite 3.37.2.

Windows
-------

- bpo-44549: Update bzip2 to 1.0.8 in Windows builds to mitigate
  CVE-2016-3189 and CVE-2019-12900

- bpo-46948: Prevent CVE-2022-26488 by ensuring the Add to PATH option in
  the Windows installer uses the correct path when being repaired.

- bpo-46638: Ensures registry virtualization is consistently disabled. For
  3.10 and earlier, it remains enabled (some registry writes are protected),
  while for 3.11 and later it is disabled (registry modifications affect all
  applications).

macOS
-----

- bpo-45925: Update macOS installer to SQLite 3.37.2.

IDLE
----

- bpo-46630: Make query dialogs on Windows start with a cursor in the entry
  box.

- bpo-45296: Clarify close, quit, and exit in IDLE.  In the File menu,
  'Close' and 'Exit' are now 'Close Window' (the current one) and 'Exit' is
  now 'Exit IDLE' (by closing all windows).  In Shell, 'quit()' and 'exit()'
  mean 'close Shell'. If there are no other windows, this also exits IDLE.

- bpo-45447: Apply IDLE syntax highlighting to `.pyi` files. Patch by Alex
  Waygood and Terry Jan Reedy.

C API
-----

- bpo-46433: The internal function _PyType_GetModuleByDef now correctly
  handles inheritance patterns involving static types.

- bpo-14916: Fixed bug in the tokenizer that prevented
  ``PyRun_InteractiveOne`` from parsing from the provided FD.


What's New in Python 3.10.2 final?
==================================

*Release date: 2022-01-13*

Core and Builtins
-----------------

- bpo-46347: Fix memory leak in PyEval_EvalCodeEx.

- bpo-46289: ASDL declaration of ``FormattedValue`` has changed to reflect
  ``conversion`` field is not optional.

- bpo-46237: Fix the line number of tokenizer errors inside f-strings. Patch
  by Pablo Galindo.

- bpo-46006: Fix a regression when a type method like ``__init__()`` is
  modified in a subinterpreter. Fix a regression in
  ``_PyUnicode_EqualToASCIIId()`` and type ``update_slot()``. Revert the
  change which made the Unicode dictionary of interned strings compatible
  with subinterpreters: the internal interned dictionary is shared again by
  all interpreters. Patch by Victor Stinner.

- bpo-46085: Fix iterator cache mechanism of :class:`OrderedDict`.

- bpo-46110: Add a maximum recursion check to the PEG parser to avoid stack
  overflow. Patch by Pablo Galindo

- bpo-46054: Fix parser error when parsing non-utf8 characters in source
  files. Patch by Pablo Galindo.

- bpo-46042: Improve the location of the caret in :exc:`SyntaxError`
  exceptions emitted by the symbol table. Patch by Pablo Galindo.

- bpo-46025: Fix a crash in the :mod:`atexit` module involving functions
  that unregister themselves before raising exceptions. Patch by Pablo
  Galindo.

- bpo-46009: Restore behavior from 3.9 and earlier when sending non-None to
  newly started generator. In 3.9 this did not affect the state of the
  generator. In 3.10.0 and 3.10.1 ``gen_func().send(0)`` is equivalent to
  ``gen_func().throw(TypeError(...)`` which exhausts the generator. In
  3.10.2 onward, the behavior has been reverted to that of 3.9.

- bpo-46000: Improve compatibility of the :mod:`curses` module with NetBSD
  curses.

- bpo-46004: Fix the :exc:`SyntaxError` location for errors involving for
  loops with invalid targets. Patch by Pablo Galindo

- bpo-42918: Fix bug where the built-in :func:`compile` function did not
  always raise a :exc:`SyntaxError` when passed multiple statements in
  'single' mode. Patch by Weipeng Hong.

Library
-------

- bpo-40479: Fix :mod:`hashlib` *usedforsecurity* option to work correctly
  with OpenSSL 3.0.0 in FIPS mode.

- bpo-46070: Fix possible segfault when importing the :mod:`asyncio` module
  from different sub-interpreters in parallel. Patch by Erlend E. Aasland.

- bpo-46278: Reflect ``context`` argument in ``AbstractEventLoop.call_*()``
  methods. Loop implementations already support it.

- bpo-46239: Improve error message when importing
  :mod:`asyncio.windows_events` on non-Windows.

- bpo-20369: :func:`concurrent.futures.wait` no longer blocks forever when
  given duplicate Futures. Patch by Kumar Aditya.

- bpo-46105: Honor spec when generating requirement specs with urls and
  extras (importlib_metadata 4.8.3).

- bpo-26952: :mod:`argparse` raises :exc:`ValueError` with clear message
  when trying to render usage for an empty mutually-exclusive group.
  Previously it raised a cryptic :exc:`IndexError`.

- bpo-27718: Fix help for the :mod:`signal` module. Some functions (e.g.
  ``signal()`` and ``getsignal()``) were omitted.

- bpo-46032: The ``registry()`` method of :func:`functools.singledispatch`
  functions checks now the first argument or the first parameter annotation
  and raises a TypeError if it is not supported. Previously unsupported
  "types" were ignored (e.g. ``typing.List[int]``) or caused an error at
  calling time (e.g. ``list[int]``).

- bpo-46018: Ensure that :func:`math.expm1` does not raise on underflow.

- bpo-45755: :mod:`typing` generic aliases now reveal the class attributes
  of the original generic class when passed to ``dir()``. This was the
  behavior up to Python 3.6, but was changed in 3.7-3.9.

- bpo-13236: :class:`unittest.TextTestResult` and
  :class:`unittest.TextTestRunner` flush now the output stream more often.

- bpo-42378: Fixes the issue with log file being overwritten when
  :class:`logging.FileHandler` is used in :mod:`atexit` with *filemode* set
  to ``'w'``. Note this will cause the message in *atexit* not being logged
  if the log stream is already closed due to shutdown of logging.

Documentation
-------------

- bpo-46120: State that ``|`` is preferred for readability over ``Union`` in
  the :mod:`typing` docs.

- bpo-46040: Fix removal Python version for ``@asyncio.coroutine``, the
  correct value is 3.11.

- bpo-19737: Update the documentation for the :func:`globals` function.

- bpo-45840: Improve cross-references in the documentation for the data
  model.

Tests
-----

- bpo-46205: Fix hang in runtest_mp due to race condition

- bpo-46263: Fix test_capi on FreeBSD 14-dev: instruct jemalloc to not fill
  freed memory with junk byte.

- bpo-46150: Now ``fakename`` in
  ``test_pathlib.PosixPathTest.test_expanduser`` is checked to be
  non-existent.

- bpo-46129: Rewrite ``asyncio.locks`` tests with
  :class:`unittest.IsolatedAsyncioTestCase` usage.

- bpo-46114: Fix test case for OpenSSL 3.0.1 version. OpenSSL 3.0 uses
  ``0xMNN00PP0L``.

Build
-----

- bpo-46263: ``configure`` no longer sets ``MULTIARCH`` on FreeBSD
  platforms.

- bpo-46106: Updated OpenSSL to 1.1.1m in Windows builds, macOS installer
  builds, and CI. Patch by Kumar Aditya.

macOS
-----

- bpo-40477: The Python Launcher app for macOS now properly launches scripts
  and, if necessary, the Terminal app when running on recent macOS releases.

C API
-----

- bpo-46236: Fix a bug in :c:func:`PyFunction_GetAnnotations` that caused it
  to return a ``tuple`` instead of a ``dict``.


What's New in Python 3.10.1 final?
==================================

*Release date: 2021-12-06*

Core and Builtins
-----------------

- bpo-42268: Fail the configure step if the selected compiler doesn't
  support memory sanitizer. Patch by Pablo Galindo

- bpo-45727: Refine the custom syntax error that suggests that a comma may
  be missing to trigger only when the expressions are detected between
  parentheses or brackets. Patch by Pablo Galindo

- bpo-45614: Fix :mod:`traceback` display for exceptions with invalid module
  name.

- bpo-45848: Allow the parser to obtain error lines directly from encoded
  files. Patch by Pablo Galindo

- bpo-45826: Fixed a crash when calling ``.with_traceback(None)`` on
  ``NameError``. This occurs internally in
  ``unittest.TestCase.assertRaises()``.

- bpo-45822: Fixed a bug in the parser that was causing it to not respect
  :pep:`263` coding cookies when no flags are provided. Patch by Pablo
  Galindo

- bpo-45820: Fix a segfault when the parser fails without reading any input.
  Patch by Pablo Galindo

- bpo-42540: Fix crash when :func:`os.fork` is called with an active
  non-default memory allocator.

- bpo-45738: Fix computation of error location for invalid continuation
  characters in the parser. Patch by Pablo Galindo.

- bpo-45773: Fix a compiler hang when attempting to optimize certain jump
  patterns.

- bpo-45716: Improve the :exc:`SyntaxError` message when using ``True``,
  ``None`` or ``False`` as keywords in a function call. Patch by Pablo
  Galindo.

- bpo-45688: :data:`sys.stdlib_module_names` now contains the macOS-specific
  module :mod:`_scproxy`.

- bpo-30570: Fixed a crash in ``issubclass()`` from infinite recursion when
  searching pathological ``__bases__`` tuples.

- bpo-45521: Fix a bug in the obmalloc radix tree code.  On 64-bit machines,
  the bug causes the tree to hold 46-bits of virtual addresses, rather than
  the intended 48-bits.

- bpo-45494: Fix parser crash when reporting errors involving invalid
  continuation characters. Patch by Pablo Galindo.

- bpo-45408: Fix a crash in the parser when reporting tokenizer errors that
  occur at the same time unclosed parentheses are detected. Patch by Pablo
  Galindo.

- bpo-45385: Fix reference leak from descr_check. Patch by Dong-hee Na.

- bpo-45167: Fix deepcopying of :class:`types.GenericAlias` objects.

- bpo-44219: Release the GIL while performing ``isatty`` system calls on
  arbitrary file descriptors. In particular, this affects :func:`os.isatty`,
  :func:`os.device_encoding` and :class:`io.TextIOWrapper`. By extension,
  :func:`io.open` in text mode is also affected. This change solves a
  deadlock in :func:`os.isatty`. Patch by Vincent Michel in :issue:`44219`.

- bpo-44959: Added fallback to extension modules with '.sl' suffix on HP-UX

- bpo-44050: Extensions that indicate they use global state (by setting
  ``m_size`` to -1) can again be used in multiple interpreters. This reverts
  to behavior of Python 3.8.

- bpo-45121: Fix issue where ``Protocol.__init__`` raises ``RecursionError``
  when it's called directly or via ``super()``. Patch provided by Yurii
  Karabas.

- bpo-45083: When the interpreter renders an exception, its name now has a
  complete qualname. Previously only the class name was concatenated to the
  module name, which sometimes resulted in an incorrect full name being
  displayed.

  (This issue impacted only the C code exception rendering, the
  :mod:`traceback` module was using qualname already).

- bpo-45056: Compiler now removes trailing unused constants from co_consts.

Library
-------

- bpo-27946: Fix possible crash when getting an attribute of
  class:`xml.etree.ElementTree.Element` simultaneously with replacing the
  ``attrib`` dict.

- bpo-37658: Fix issue when on certain conditions ``asyncio.wait_for()`` may
  allow a coroutine to complete successfully, but fail to return the result,
  potentially causing memory leaks or other issues.

- bpo-44649: Handle dataclass(slots=True) with a field that has default a
  default value, but for which init=False.

- bpo-45803: Added missing kw_only parameter to
  dataclasses.make_dataclass().

- bpo-45831: :mod:`faulthandler` can now write ASCII-only strings (like
  filenames and function names) with a single write() syscall when dumping a
  traceback. It reduces the risk of getting an unreadable dump when two
  threads or two processes dump a traceback to the same file (like stderr)
  at the same time. Patch by Victor Stinner.

- bpo-41735: Fix thread lock in ``zlib.Decompress.flush()`` method before
  ``PyObject_GetBuffer``.

- bpo-45235: Reverted an argparse bugfix that caused regression in the
  handling of default arguments for subparsers.  This prevented leaf level
  arguments from taking precedence over root level arguments.

- bpo-45765: In importlib.metadata, fix distribution discovery for an empty
  path.

- bpo-45757: Fix bug where :mod:`dis` produced an incorrect oparg when
  :opcode:`EXTENDED_ARG` is followed by an opcode that does not use its
  argument.

- bpo-45644: In-place JSON file formatting using ``python3 -m json.tool
  infile infile`` now works correctly, previously it left the file empty.
  Patch by Chris Wesseling.

- bpo-45679: Fix caching of multi-value :data:`typing.Literal`.
  ``Literal[True, 2]`` is no longer equal to ``Literal[1, 2]``.

- bpo-45664: Fix :func:`types.resolve_bases` and :func:`types.new_class` for
  :class:`types.GenericAlias` instance as a base.

- bpo-45663: Fix :func:`dataclasses.is_dataclass` for dataclasses which are
  subclasses of :class:`types.GenericAlias`.

- bpo-45662: Fix the repr of :data:`dataclasses.InitVar` with a type alias
  to the built-in class, e.g. ``InitVar[list[int]]``.

- bpo-45438: Fix typing.Signature string representation for generic builtin
  types.

- bpo-45574: Fix warning about ``print_escape`` being unused.

- bpo-45581: :meth:`sqlite3.connect` now correctly raises :exc:`MemoryError`
  if the underlying SQLite API signals memory error. Patch by Erlend E.
  Aasland.

- bpo-45557: pprint.pprint() now handles underscore_numbers correctly.
  Previously it was always setting it to False.

- bpo-45515: Add references to :mod:`zoneinfo` in the :mod:`datetime`
  documentation, mostly replacing outdated references to ``dateutil.tz``.
  Change by Paul Ganssle.

- bpo-45475: Reverted optimization of iterating :class:`gzip.GzipFile`,
  :class:`bz2.BZ2File`, and :class:`lzma.LZMAFile` (see bpo-43787) because
  it caused regression when user iterate them without having reference of
  them. Patch by Inada Naoki.

- bpo-45428: Fix a regression in py_compile when reading filenames from
  standard input.

- bpo-45467: Fix incremental decoder and stream reader in the
  "raw-unicode-escape" codec. Previously they failed if the escape sequence
  was split.

- bpo-45461: Fix incremental decoder and stream reader in the
  "unicode-escape" codec. Previously they failed if the escape sequence was
  split.

- bpo-45239: Fixed :func:`email.utils.parsedate_tz` crashing with
  :exc:`UnboundLocalError` on certain invalid input instead of returning
  ``None``. Patch by Ben Hoyt.

- bpo-45249: Fix the behaviour of :func:`traceback.print_exc` when
  displaying the caret when the ``end_offset`` in the exception is set to 0.
  Patch by Pablo Galindo

- bpo-45416: Fix use of :class:`asyncio.Condition` with explicit
  :class:`asyncio.Lock` objects, which was a regression due to removal of
  explicit loop arguments. Patch by Joongi Kim.

- bpo-45419: Correct interfaces on DegenerateFiles.Path.

- bpo-44904: Fix bug in the :mod:`doctest` module that caused it to fail if
  a docstring included an example with a ``classmethod`` ``property``. Patch
  by Alex Waygood.

- bpo-45406: Make :func:`inspect.getmodule` catch ``FileNotFoundError``
  raised by :'func:`inspect.getabsfile`, and return ``None`` to indicate
  that the module could not be determined.

- bpo-45262: Prevent use-after-free in asyncio. Make sure the cached running
  loop holder gets cleared on dealloc to prevent use-after-free in
  get_running_loop

- bpo-45386: Make :mod:`xmlrpc.client` more robust to C runtimes where the
  underlying C ``strftime`` function results in a ``ValueError`` when
  testing for year formatting options.

- bpo-45371: Fix clang rpath issue in :mod:`distutils`. The UnixCCompiler
  now uses correct clang option to add a runtime library directory (rpath)
  to a shared library.

- bpo-20028: Improve error message of :class:`csv.Dialect` when
  initializing. Patch by Vajrasky Kok and Dong-hee Na.

- bpo-45343: Update bundled pip to 21.2.4 and setuptools to 58.1.0

- bpo-45329: Fix freed memory access in :class:`pyexpat.xmlparser` when
  building it with an installed expat library <= 2.2.0.

- bpo-41710: On Unix, if the ``sem_clockwait()`` function is available in
  the C library (glibc 2.30 and newer), the :meth:`threading.Lock.acquire`
  method now uses the monotonic clock (:data:`time.CLOCK_MONOTONIC`) for the
  timeout, rather than using the system clock (:data:`time.CLOCK_REALTIME`),
  to not be affected by system clock changes. Patch by Victor Stinner.

- bpo-45328: Fixed :class:`http.client.HTTPConnection` to work properly in
  OSs that don't support the ``TCP_NODELAY`` socket option.

- bpo-1596321: Fix the :func:`threading._shutdown` function when the
  :mod:`threading` module was imported first from a thread different than
  the main thread: no longer log an error at Python exit.

- bpo-45274: Fix a race condition in the :meth:`Thread.join()
  <threading.Thread.join>` method of the :mod:`threading` module. If the
  function is interrupted by a signal and the signal handler raises an
  exception, make sure that the thread remains in a consistent state to
  prevent a deadlock. Patch by Victor Stinner.

- bpo-45238: Fix :meth:`unittest.IsolatedAsyncioTestCase.debug`: it runs now
  asynchronous methods and callbacks.

- bpo-36674: :meth:`unittest.TestCase.debug` raises now a
  :class:`unittest.SkipTest` if the class or the test method are decorated
  with the skipping decorator.

- bpo-45235: Fix an issue where argparse would not preserve values in a
  provided namespace when using a subparser with defaults.

- bpo-45183: Have zipimport.zipimporter.find_spec() not raise an exception
  when the underlying zip file has been deleted and the internal cache has
  been reset via invalidate_cache().

- bpo-45234: Fixed a regression in :func:`~shutil.copyfile`,
  :func:`~shutil.copy`, :func:`~shutil.copy2` raising
  :exc:`FileNotFoundError` when source is a directory, which should raise
  :exc:`IsADirectoryError`

- bpo-45228: Fix stack buffer overflow in parsing J1939 network address.

- bpo-45192: Fix the ``tempfile._infer_return_type`` function so that the
  ``dir`` argument of the :mod:`tempfile` functions accepts an object
  implementing the ``os.PathLike`` protocol.

  Patch by Kyungmin Lee.

- bpo-42135: Fix typo: ``importlib.find_loader`` is really slated for
  removal in Python 3.12 not 3.10, like the others in PR 25169.

  Patch by Hugo van Kemenade.

- bpo-45160: When tracing a tkinter variable used by a ttk OptionMenu,
  callbacks are no longer made twice.

- bpo-35474: Calling :func:`mimetypes.guess_all_extensions` with
  ``strict=False`` no longer affects the result of the following call with
  ``strict=True``. Also, mutating the returned list no longer affects the
  global state.

- bpo-45166: :func:`typing.get_type_hints` now works with
  :data:`~typing.Final` wrapped in :class:`~typing.ForwardRef`.

- bpo-20499: Improve the speed and accuracy of statistics.pvariance().

- bpo-24444: Fixed an error raised in :mod:`argparse` help display when help
  for an option is set to 1+ blank spaces or when *choices* arg is an empty
  container.

- bpo-45021: Fix a potential deadlock at shutdown of forked children when
  using :mod:`concurrent.futures` module

- bpo-39039: tarfile.open raises :exc:`~tarfile.ReadError` when a zlib error
  occurs during file extraction.

- bpo-44594: Fix an edge case of :class:`ExitStack` and
  :class:`AsyncExitStack` exception chaining.  They will now match ``with``
  block behavior when ``__context__`` is explicitly set to ``None`` when the
  exception is in flight.

- bpo-44295: Ensure deprecation warning from
  :func:`assertDictContainsSubset` points at calling code - by Anthony
  Sottile.

- bpo-43498: Avoid a possible *"RuntimeError: dictionary changed size during
  iteration"* when adjusting the process count of
  :class:`ProcessPoolExecutor`.

Documentation
-------------

- bpo-45640: Properly marked-up grammar tokens in the documentation are now
  clickable and take you to the definition of a given piece of grammar.
  Patch by Arthur Milchior.

- bpo-45788: Link doc for sys.prefix to sysconfig doc on installation paths.

- bpo-45772: ``socket.socket`` documentation is corrected to a class from a
  function.

- bpo-45392: Update the docstring of the :class:`type` built-in to remove a
  redundant line and to mention keyword arguments for the constructor.

- bpo-45726: Improve documentation for :func:`functools.singledispatch` and
  :class:`functools.singledispatchmethod`.

- bpo-45680: Amend the docs on ``GenericAlias`` objects to clarify that
  non-container classes can also implement ``__class_getitem__``. Patch
  contributed by Alex Waygood.

- bpo-45655: Add a new "relevant PEPs" section to the top of the
  documentation for the ``typing`` module. Patch by Alex Waygood.

- bpo-45604: Add ``level`` argument to ``multiprocessing.log_to_stderr``
  function docs.

- bpo-45250: Update the documentation to note that CPython does not
  consistently require iterators to define ``__iter__``.

- bpo-45464: Mention in the documentation of :ref:`Built-in Exceptions
  <bltin-exceptions>` that inheriting from multiple exception types in a
  single subclass is not recommended due to possible memory layout
  incompatibility.

- bpo-45449: Add note about :pep:`585` in :mod:`collections.abc`.

- bpo-45516: Add protocol description to the
  :class:`importlib.abc.Traversable` documentation.

- bpo-20692: Add Programming FAQ entry explaining that int literal attribute
  access requires either a space after or parentheses around the literal.

- bpo-45216: Remove extra documentation listing methods in ``difflib``. It
  was rendering twice in pydoc and was outdated in some places.

- bpo-45024: :mod:`collections.abc` documentation has been expanded to
  explicitly cover how instance and subclass checks work, with additional
  doctest examples and an exhaustive list of ABCs which test membership
  purely by presence of the right :term:`special method`\s. Patch by Raymond
  Hettinger.

- bpo-25381: In the extending chapter of the extending doc, update a
  paragraph about the global variables containing exception information.

- bpo-43905: Expanded :func:`~dataclasses.astuple` and
  :func:`~dataclasses.asdict` docs, warning about deepcopy being applied and
  providing a workaround.

Tests
-----

- bpo-19460: Add new Test for
  :class:`email.mime.nonmultipart.MIMENonMultipart`.

- bpo-45835: Fix race condition in test_queue tests with multiple "feeder"
  threads.

- bpo-45678: Add tests for scenarios in which
  :class:`functools.singledispatchmethod` is stacked on top of a method that
  has already been wrapped by two other decorators. Patch by Alex Waygood.

- bpo-45578: Add tests for :func:`dis.distb`

- bpo-45678: Add tests to ensure that ``functools.singledispatchmethod``
  correctly wraps the attributes of the target function.

- bpo-45577: Add subtests for all ``pickle`` protocols in ``test_zoneinfo``.

- bpo-45566: Fix ``test_frozen_pickle`` in ``test_dataclasses`` to check all
  ``pickle`` versions.

- bpo-43592: :mod:`test.libregrtest` now raises the soft resource limit for
  the maximum number of file descriptors when the default is too low for our
  test suite as was often the case on macOS.

- bpo-39679: Add more test cases for `@functools.singledispatchmethod` when
  combined with `@classmethod` or `@staticmethod`.

- bpo-45400: Fix
  test_name_error_suggestions_do_not_trigger_for_too_many_locals() of
  test_exceptions if a directory name contains "a1" (like
  "Python-3.11.0a1"): use a stricter regular expression. Patch by Victor
  Stinner.

- bpo-40173: Fix :func:`test.support.import_helper.import_fresh_module`.

- bpo-45280: Add a test case for empty :class:`typing.NamedTuple`.

- bpo-45269: Cover case when invalid ``markers`` type is supplied to
  ``c_make_encoder``.

- bpo-45128: Fix ``test_multiprocessing_fork`` failure due to
  ``test_logging`` and ``sys.modules`` manipulation.

- bpo-45209: Fix ``UserWarning: resource_tracker`` warning in
  ``_test_multiprocessing._TestSharedMemory.test_shared_memory_cleaned_after_process_termination``

- bpo-45195: Fix test_readline.test_nonascii(): sometimes, the newline
  character is not written at the end, so don't expect it in the output.
  Patch by Victor Stinner.

- bpo-45156: Fixes infinite loop on :func:`unittest.mock.seal` of mocks
  created by :func:`~unittest.create_autospec`.

- bpo-45125: Improves pickling tests and docs of ``SharedMemory`` and
  ``SharableList`` objects.

- bpo-44860: Update ``test_sysconfig.test_user_similar()`` for the
  posix_user scheme: ``platlib`` doesn't use :data:`sys.platlibdir`. Patch
  by Victor Stinner.

- bpo-25130: Add calls of :func:`gc.collect` in tests to support PyPy.

Build
-----

- bpo-44035: CI now verifies that autoconf files have been regenerated with
  a current and unpatched autoconf package.

- bpo-33393: Update ``config.guess`` to 2021-06-03 and ``config.sub`` to
  2021-08-14. ``Makefile`` now has an ``update-config`` target to make
  updating more convenient.

- bpo-45866: ``make regen-all`` now produces the same output when run from a
  directory other than the source tree: when building Python out of the
  source tree. pegen now strips directory of the "generated by pygen from
  <FILENAME>" header Patch by Victor Stinner.

- bpo-41498: Python now compiles on platforms without ``sigset_t``. Several
  functions in :mod:`signal` are not available when ``sigset_t`` is missing.

  Based on patch by Roman Yurchak for pyodide.

- bpo-45881: ``setup.py`` now uses ``CC`` from environment first to discover
  multiarch and cross compile paths.

- bpo-43158: ``setup.py`` now uses values from configure script to build the
  ``_uuid`` extension module. Configure now detects util-linux's
  ``libuuid``, too.

- bpo-45571: ``Modules/Setup`` now use ``PY_CFLAGS_NODIST`` instead of
  ``PY_CFLAGS`` to compile shared modules.

- bpo-45561: Run smelly.py tool from $(srcdir).

- bpo-45532: Update :data:`sys.version` to use ``main`` as fallback
  information. Patch by Jeong YunWon.

- bpo-45536: The ``configure`` script now checks whether OpenSSL headers and
  libraries provide required APIs. Most common APIs are verified. The check
  detects outdated or missing OpenSSL. Failures do not stop configure.

- bpo-45221: Fixed regression in handling of ``LDFLAGS`` and ``CPPFLAGS``
  options where :meth:`argparse.parse_known_args` could interpret an option
  as one of the built-in command line argument, for example ``-h`` for help.

- bpo-45405: Prevent ``internal configure error`` when running ``configure``
  with recent versions of non-Apple clang.  Patch by David Bohman.

- bpo-45220: Avoid building with the Windows 11 SDK previews automatically.
  This may be overridden by setting the ``DefaultWindowsSDKVersion``
  environment variable before building.

- bpo-45067: The ncurses function extended_color_content was introduced in
  2017

  (https://invisible-island.net/ncurses/NEWS.html#index-t20170401).  The

  ncurses-devel package in CentOS 7 had a older version ncurses resulted in
  compilation error.  For compiling ncurses with extended color support, we
  verify the version of the ncurses library >= 20170401.

Windows
-------

- bpo-45901: When installed through the Microsoft Store and set as the
  default app for :file:`*.py` files, command line arguments will now be
  passed to Python when invoking a script without explicitly launching
  Python (that is, ``script.py args`` rather than ``python script.py
  args``).

- bpo-45616: Fix Python Launcher's ability to distinguish between versions
  3.1 and 3.10 when either one is explicitly requested.  Previously, 3.1
  would be used if 3.10 was requested but not installed, and 3.10 would be
  used if 3.1 was requested but 3.10 was installed.

- bpo-45732: Updates bundled Tcl/Tk to 8.6.12.

- bpo-45720: Internal reference to :file:`shlwapi.dll` was dropped to help
  improve startup time. This DLL will no longer be loaded at the start of
  every Python process.

- bpo-43652: Update Tcl/Tk to 8.6.11, actually this time. The previous
  update incorrectly included 8.6.10.

- bpo-45337: venv now warns when the created environment may need to be
  accessed at a different path, due to redirections, links or junctions. It
  also now correctly installs or upgrades components when the alternate path
  is required.

macOS
-----

- bpo-45732: Update python.org macOS installer to use Tcl/Tk 8.6.12.

- bpo-44828: Avoid tkinter file dialog failure on macOS 12 Monterey when
  using the Tk 8.6.11 provided by python.org macOS installers. Patch by Marc
  Culler of the Tk project.

- bpo-34602: When building CPython on macOS with ``./configure
  --with-undefined-behavior-sanitizer --with-pydebug``, the stack size is
  now quadrupled to allow for the entire test suite to pass.

IDLE
----

- bpo-45495: Add context keywords 'case' and 'match' to completions list.

- bpo-45296: On Windows, change exit/quit message to suggest Ctrl-D, which
  works, instead of <Ctrl-Z Return>, which does not work in IDLE.

- bpo-45193: Make completion boxes appear on Ubuntu again.

Tools/Demos
-----------

- bpo-44786: Fix a warning in regular expression in the c-analyzer script.

C API
-----

- bpo-39026: Fix Python.h to build C extensions with Xcode: remove a
  relative include from ``Include/cpython/pystate.h``.

- bpo-45307: Restore the private C API function
  :func:`_PyImport_FindExtensionObject`. It will be removed in Python 3.11.

- bpo-44687: :meth:`BufferedReader.peek` no longer raises :exc:`ValueError`
  when the entire file has already been buffered.

- bpo-44751: Remove ``crypt.h`` include from the public ``Python.h`` header.


What's New in Python 3.10.0 final?
==================================

*Release date: 2021-10-04*

Core and Builtins
-----------------

- bpo-45121: Fix issue where ``Protocol.__init__`` raises ``RecursionError``
  when it's called directly or via ``super()``. Patch provided by Yurii
  Karabas.

Library
-------

- bpo-45234: Fixed a regression in :func:`~shutil.copyfile`,
  :func:`~shutil.copy`, :func:`~shutil.copy2` raising
  :exc:`FileNotFoundError` when source is a directory, which should raise
  :exc:`IsADirectoryError`

Documentation
-------------

- bpo-45216: Remove extra documentation listing methods in ``difflib``. It
  was rendering twice in pydoc and was outdated in some places.

- bpo-45024: :mod:`collections.abc` documentation has been expanded to
  explicitly cover how instance and subclass checks work, with additional
  doctest examples and an exhaustive list of ABCs which test membership
  purely by presence of the right :term:`special method`\s. Patch by Raymond
  Hettinger.

Tests
-----

- bpo-45128: Fix ``test_multiprocessing_fork`` failure due to
  ``test_logging`` and ``sys.modules`` manipulation.

- bpo-44860: Update ``test_sysconfig.test_user_similar()`` for the
  posix_user scheme: ``platlib`` doesn't use :data:`sys.platlibdir`. Patch
  by Victor Stinner.

Build
-----

- bpo-45067: The ncurses function extended_color_content was introduced in
  2017

  (https://invisible-island.net/ncurses/NEWS.html#index-t20170401).  The

  ncurses-devel package in CentOS 7 had a older version ncurses resulted in
  compilation error.  For compiling ncurses with extended color support, we
  verify the version of the ncurses library >= 20170401.

IDLE
----

- bpo-45193: Make completion boxes appear on Ubuntu again.

C API
-----

- bpo-45307: Restore the private C API function
  :func:`_PyImport_FindExtensionObject`. It will be removed in Python 3.11.


What's New in Python 3.10.0 release candidate 2?
================================================

*Release date: 2021-09-07*

Security
--------

- bpo-42278: Replaced usage of :func:`tempfile.mktemp` with
  :class:`~tempfile.TemporaryDirectory` to avoid a potential race condition.

- bpo-44394: Update the vendored copy of libexpat to 2.4.1 (from 2.2.8) to
  get the fix for the CVE-2013-0340 "Billion Laughs" vulnerability. This
  copy is most used on Windows and macOS.

- bpo-43124: Made the internal ``putcmd`` function in :mod:`smtplib`
  sanitize input for presence of ``\r`` and ``\n`` characters to avoid
  (unlikely) command injection.

Core and Builtins
-----------------

- bpo-45123: Fix PyAiter_Check to only check for the __anext__ presence (not
  for __aiter__). Rename PyAiter_Check to PyAIter_Check, PyObject_GetAiter
  -> PyObject_GetAIter.

- bpo-45018: Fixed pickling of range iterators that iterated for over 2**32
  times.

- bpo-45000: A :exc:`SyntaxError` is now raised when trying to delete
  :const:`__debug__`. Patch by Dong-hee Na.

- bpo-44963: Implement ``send()`` and ``throw()`` methods for
  ``anext_awaitable`` objects. Patch by Pablo Galindo.

- bpo-44962: Fix a race in WeakKeyDictionary, WeakValueDictionary and
  WeakSet when two threads attempt to commit the last pending removal. This
  fixes asyncio.create_task and fixes a data loss in asyncio.run where
  shutdown_asyncgens is not run

- bpo-44954: Fixed a corner case bug where the result of
  ``float.fromhex('0x.8p-1074')`` was rounded the wrong way.

- bpo-44947: Refine the syntax error for trailing commas in import
  statements. Patch by Pablo Galindo.

- bpo-44698: Restore behaviour of complex exponentiation with integer-valued
  exponent of type :class:`float` or :class:`complex`.

- bpo-44885: Correct the ast locations of f-strings with format specs and
  repeated expressions. Patch by Pablo Galindo

- bpo-44872: Use new trashcan macros (Py_TRASHCAN_BEGIN/END) in
  frameobject.c instead of the old ones (Py_TRASHCAN_SAFE_BEGIN/END).

- bpo-33930: Fix segmentation fault with deep recursion when cleaning method
  objects. Patch by Augusto Goulart and Pablo Galindo.

- bpo-25782: Fix bug where ``PyErr_SetObject`` hangs when the current
  exception has a cycle in its context chain.

- bpo-44856: Fix reference leaks in the error paths of ``update_bases()``
  and ``__build_class__``. Patch by Pablo Galindo.

- bpo-44838: Fixed a bug that was causing the parser to raise an incorrect
  custom :exc:`SyntaxError` for invalid 'if' expressions. Patch by Pablo
  Galindo.

- bpo-44584: The threading debug (:envvar:`PYTHONTHREADDEBUG` environment
  variable) is deprecated in Python 3.10 and will be removed in Python 3.12.
  This feature requires a debug build of Python. Patch by Victor Stinner.

- bpo-39091: Fix crash when using passing a non-exception to a generator's
  ``throw()`` method. Patch by Noah Oxer

Library
-------

- bpo-45081: Fix issue when dataclasses that inherit from
  ``typing.Protocol`` subclasses have wrong ``__init__``. Patch provided by
  Yurii Karabas.

- bpo-41620: :meth:`~unittest.TestCase.run` now always return a
  :class:`~unittest.TestResult` instance. Previously it returned ``None`` if
  the test class or method was decorated with a skipping decorator.

- bpo-43913: Fix bugs in cleaning up classes and modules in :mod:`unittest`:

  * Functions registered with :func:`~unittest.addModuleCleanup` were not called unless the user defines ``tearDownModule()`` in their test module.
  * Functions registered with :meth:`~unittest.TestCase.addClassCleanup` were not called if ``tearDownClass`` is set to ``None``.
  * Buffering in :class:`~unittest.TestResult` did not work with functions registered with ``addClassCleanup()`` and ``addModuleCleanup()``.
  * Errors in functions registered with ``addClassCleanup()`` and ``addModuleCleanup()`` were not handled correctly in buffered and debug modes.
  * Errors in ``setUpModule()`` and functions registered with ``addModuleCleanup()`` were reported in wrong order.
  * And several lesser bugs.

- bpo-45030: Fix integer overflow in pickling and copying the range
  iterator.

- bpo-45001: Made email date parsing more robust against malformed input,
  namely a whitespace-only ``Date:`` header. Patch by Wouter Bolsterlee.

- bpo-44449: Fix a crash in the signal handler of the :mod:`faulthandler`
  module: no longer modify the reference count of frame objects. Patch by
  Victor Stinner.

- bpo-44955: Method :meth:`~unittest.TestResult.stopTestRun` is now always
  called in pair with method :meth:`~unittest.TestResult.startTestRun` for
  :class:`~unittest.TestResult` objects implicitly created in
  :meth:`~unittest.TestCase.run`. Previously it was not called for test
  methods and classes decorated with a skipping decorator.

- bpo-44935: :mod:`subprocess` on Solaris now also uses
  :func:`os.posix_spawn()` for better performance.

- bpo-44911: :class:`~unittest.IsolatedAsyncioTestCase` will no longer throw
  an exception while cancelling leaked tasks. Patch by Bar Harel.

- bpo-44524: Make exception message more useful when subclass from typing
  special form alias. Patch provided by Yurii Karabas.

- bpo-38956: :class:`argparse.BooleanOptionalAction`'s default value is no
  longer printed twice when used with
  :class:`argparse.ArgumentDefaultsHelpFormatter`.

- bpo-44860: Fix the ``posix_user`` scheme in :mod:`sysconfig` to not depend
  on :data:`sys.platlibdir`.

- bpo-44581: Upgrade bundled pip to 21.2.3 and setuptools to 57.4.0

- bpo-44849: Fix the :func:`os.set_inheritable` function on FreeBSD 14 for
  file descriptor opened with the :data:`~os.O_PATH` flag: ignore the
  :data:`~errno.EBADF` error on ``ioctl()``, fallback on the ``fcntl()``
  implementation. Patch by Victor Stinner.

- bpo-44605: The @functools.total_ordering() decorator now works with
  metaclasses.

- bpo-44524: Fixed an issue wherein the ``__name__`` and ``__qualname__``
  attributes of subscribed specialforms could be ``None``.

- bpo-44822: :mod:`sqlite3` user-defined functions and aggregators returning
  :class:`strings <str>` with embedded NUL characters are no longer
  truncated. Patch by Erlend E. Aasland.

- bpo-44801: Ensure that the :class:`~typing.ParamSpec` variable in Callable
  can only be substituted with a parameters expression (a list of types, an
  ellipsis, ParamSpec or Concatenate).

- bpo-27334: The :mod:`sqlite3` context manager now performs a rollback
  (thus releasing the database lock) if commit failed.  Patch by Luca Citi
  and Erlend E. Aasland.

- bpo-41402: Fix :meth:`email.message.EmailMessage.set_content` when called
  with binary data and ``7bit`` content transfer encoding.

- bpo-32695: The *compresslevel* and *preset* keyword arguments of
  :func:`tarfile.open` are now both documented and tested.

- bpo-34990: Fixed a Y2k38 bug in the compileall module where it would fail
  to compile files with a modification time after the year 2038.

- bpo-38840: Fix ``test___all__`` on platforms lacking a shared memory
  implementation.

- bpo-26228: pty.spawn no longer hangs on FreeBSD, macOS, and Solaris.

- bpo-33349: lib2to3 now recognizes async generators everywhere.

Documentation
-------------

- bpo-44957: Promote PEP 604 union syntax by using it where possible. Also,
  mention ``X | Y`` more prominently in section about ``Union`` and mention
  ``X | None`` at all in section about ``Optional``.

- bpo-44903: Removed the othergui.rst file, any references to it, and the
  list of GUI frameworks in the FAQ. In their place I've added links to the
  Python Wiki `page on GUI frameworks
  <https://wiki.python.org/moin/GuiProgramming>`.

- bpo-33479: Tkinter documentation has been greatly expanded with new
  "Architecture" and "Threading model" sections.

- bpo-36700: :mod:`base64` RFC references were updated to point to
  :rfc:`4648`; a section was added to point users to the new "security
  considerations" section of the RFC.

- bpo-44756: Reverted automated virtual environment creation on ``make
  html`` when building documentation. It turned out to be disruptive for
  downstream distributors.

- bpo-42958: Updated the docstring and docs of :func:`filecmp.cmp` to be
  more accurate and less confusing especially in respect to *shallow* arg.

- bpo-43066: Added a warning to :mod:`zipfile` docs: filename arg with a
  leading slash may cause archive to be un-openable on Windows systems.

- bpo-39452: Rewrote ``Doc/library/__main__.rst``. Broadened scope of the
  document to explicitly discuss and differentiate between ``__main__.py``
  in packages versus the ``__name__ == '__main__'`` expression (and the
  idioms that surround it).

- bpo-27752: Documentation of csv.Dialect is more descriptive.

- bpo-41576: document BaseException in favor of bare except

- bpo-39498: Add a "Security Considerations" index which links to standard
  library modules that have explicitly documented security considerations.

- bpo-33479: Remove the unqualified claim that tkinter is threadsafe. It has
  not been true for several years and likely never was. An explanation of
  what is true may be added later, after more discussion, and possibly after
  patching _tkinter.c,

Tests
-----

- bpo-45052: ``WithProcessesTestSharedMemory.test_shared_memory_basics``
  test was ignored, because ``self.assertEqual(sms.size, sms2.size)`` line
  was failing. It is now removed and test is unskipped.

  The main motivation for this line to be removed from the test is that the
  ``size`` of ``SharedMemory`` is not ever guaranteed to be the same. It is
  decided by the platform.

- bpo-45042: Fixes that test classes decorated with
  ``@hashlib_helper.requires_hashdigest`` were skipped all the time.

- bpo-45011: Made tests relying on the :mod:`_asyncio` C extension module
  optional to allow running on alternative Python implementations. Patch by
  Serhiy Storchaka.

- bpo-44949: Fix auto history tests of test_readline: sometimes, the newline
  character is not written at the end, so don't expect it in the output.

- bpo-44891: Tests were added to clarify :func:`id` is preserved when ``obj
  * 1`` is used on :class:`str` and :class:`bytes` objects. Patch by Nikita
  Sobolev.

- bpo-44852: Add ability to wholesale silence DeprecationWarnings while
  running the regression test suite.

- bpo-40928: Notify users running test_decimal regression tests on macOS of
  potential harmless "malloc can't allocate region" messages spewed by
  test_decimal.

Windows
-------

- bpo-45007: Update to OpenSSL 1.1.1l in Windows build

macOS
-----

- bpo-45007: Update macOS installer builds to use OpenSSL 1.1.1l.

- bpo-44689: :meth:`ctypes.util.find_library` now works correctly on macOS
  11 Big Sur even if Python is built on an older version of macOS.
  Previously, when built on older macOS systems, ``find_library`` was not
  able to find  macOS system libraries when running on Big Sur due to
  changes in  how system libraries are stored.


What's New in Python 3.10.0 release candidate 1?
================================================

*Release date: 2021-08-02*

Security
--------

- bpo-44600: Fix incorrect line numbers while tracing some failed patterns
  in :ref:`match <match>` statements. Patch by Charles Burkland.

Core and Builtins
-----------------

- bpo-44792: Improve syntax errors for if expressions. Patch by Miguel Brito

- bpo-34013: Generalize the invalid legacy statement custom error message
  (like the one generated when "print" is called without parentheses) to
  include more generic expressions. Patch by Pablo Galindo

- bpo-44732: Rename ``types.Union`` to ``types.UnionType``.

- bpo-44698: Fix undefined behaviour in complex object exponentiation.

- bpo-44653: Support :mod:`typing` types in parameter substitution in the
  union type.

- bpo-44676: Add ability to serialise ``types.Union`` objects. Patch
  provided by Yurii Karabas.

- bpo-44633: Parameter substitution of the union type with wrong types now
  raises ``TypeError`` instead of returning ``NotImplemented``.

- bpo-44662: Add ``__module__`` to ``types.Union``. This also fixes
  ``types.Union`` issues with ``typing.Annotated``. Patch provided by Yurii
  Karabas.

- bpo-44655: Include the name of the type in unset __slots__ attribute
  errors. Patch by Pablo Galindo

- bpo-44655: Don't include a missing attribute with the same name as the
  failing one when offering suggestions for missing attributes. Patch by
  Pablo Galindo

- bpo-44646: Fix the hash of the union type: it no longer depends on the
  order of arguments.

- bpo-44636: Collapse union of equal types. E.g. the result of ``int | int``
  is now ``int``. Fix comparison of the union type with non-hashable
  objects. E.g. ``int | str == {}`` no longer raises a TypeError.

- bpo-44635: Convert ``None`` to ``type(None)`` in the union type
  constructor.

- bpo-44589: Mapping patterns in ``match`` statements with two or more equal
  literal keys will now raise a :exc:`SyntaxError` at compile-time.

- bpo-44606: Fix ``__instancecheck__`` and ``__subclasscheck__`` for the
  union type.

- bpo-42073: The ``@classmethod`` decorator can now wrap other
  classmethod-like descriptors.

- bpo-44490: :mod:`typing` now searches for type parameters in
  ``types.Union`` objects. ``get_type_hints`` will also properly resolve
  annotations with nested ``types.Union`` objects. Patch provided by Yurii
  Karabas.

- bpo-44490: Add ``__parameters__`` attribute and ``__getitem__`` operator
  to ``types.Union``. Patch provided by Yurii Karabas.

- bpo-44472: Fix ltrace functionality when exceptions are raised. Patch by
  Pablo Galindo

Library
-------

- bpo-44806: Non-protocol subclasses of :class:`typing.Protocol` ignore now
  the ``__init__`` method inherited from protocol base classes.

- bpo-44793: Fix checking the number of arguments when subscribe a generic
  type with ``ParamSpec`` parameter.

- bpo-44784: In importlib.metadata tests, override warnings behavior under
  expected DeprecationWarnings (importlib_metadata 4.6.3).

- bpo-44667: The :func:`tokenize.tokenize` doesn't incorrectly generate a
  ``NEWLINE`` token if the source doesn't end with a new line character but
  the last line is a comment, as the function is already generating a ``NL``
  token. Patch by Pablo Galindo

- bpo-44752: :mod:`rcompleter` does not call :func:`getattr` on
  :class:`property` objects to avoid the side-effect of  evaluating the
  corresponding method.

- bpo-44720: ``weakref.proxy`` objects referencing non-iterators now raise
  ``TypeError`` rather than dereferencing the null ``tp_iternext`` slot and
  crashing.

- bpo-44704: The implementation of ``collections.abc.Set._hash()`` now
  matches that of ``frozenset.__hash__()``.

- bpo-44666: Fixed issue in :func:`compileall.compile_file` when
  ``sys.stdout`` is redirected. Patch by Stefan Hölzl.

- bpo-42854: Fixed a bug in the :mod:`_ssl` module that was throwing
  :exc:`OverflowError` when using :meth:`_ssl._SSLSocket.write` and
  :meth:`_ssl._SSLSocket.read` for a big value of the ``len`` parameter.
  Patch by Pablo Galindo

- bpo-44353: Refactor ``typing.NewType`` from function into callable class.
  Patch provided by Yurii Karabas.

- bpo-44524: Add missing ``__name__`` and ``__qualname__`` attributes to
  ``typing`` module classes. Patch provided by Yurii Karabas.

- bpo-40897: Give priority to using the current class constructor in
  :func:`inspect.signature`. Patch by Weipeng Hong.

- bpo-44648: Fixed wrong error being thrown by :func:`inspect.getsource`
  when examining a class in the interactive session. Instead of
  :exc:`TypeError`, it should be :exc:`OSError` with appropriate error
  message.

- bpo-44608: Fix memory leak in :func:`_tkinter._flatten` if it is called
  with a sequence or set, but not list or tuple.

- bpo-44559: [Enum] module reverted to 3.9; 3.10 changes pushed until 3.11

- bpo-41928: Update :func:`shutil.copyfile` to raise
  :exc:`FileNotFoundError` instead of confusing :exc:`IsADirectoryError`
  when a path ending with a :const:`os.path.sep` does not exist;
  :func:`shutil.copy` and :func:`shutil.copy2` are also affected.

- bpo-44566: handle StopIteration subclass raised from
  @contextlib.contextmanager generator

- bpo-41249: Fixes ``TypedDict`` to work with ``typing.get_type_hints()``
  and postponed evaluation of annotations across modules.

- bpo-44461: Fix bug with :mod:`pdb`'s handling of import error due to a
  package which does not have a ``__main__`` module

- bpo-43625: Fix a bug in the detection of CSV file headers by
  :meth:`csv.Sniffer.has_header` and improve documentation of same.

- bpo-42892: Fixed an exception thrown while parsing a malformed multipart
  email by :class:`email.message.EmailMessage`.

- bpo-27827: :meth:`pathlib.PureWindowsPath.is_reserved` now identifies a
  greater range of reserved filenames, including those with trailing spaces
  or colons.

- bpo-38741: :mod:`configparser`: using ']' inside a section header will no
  longer cut the section name short at the ']'

- bpo-27513: :func:`email.utils.getaddresses` now accepts
  :class:`email.header.Header` objects along with string values. Patch by
  Zackery Spytz.

- bpo-29298: Fix ``TypeError`` when required subparsers without ``dest`` do
  not receive arguments. Patch by Anthony Sottile.

Documentation
-------------

- bpo-44740: Replaced occurences of uppercase "Web" and "Internet" with
  lowercase versions per the 2016 revised Associated Press Style Book.

- bpo-44693: Update the definition of __future__ in the glossary by
  replacing the confusing word "pseudo-module" with a more accurate
  description.

- bpo-35183: Add typical examples to os.path.splitext docs

- bpo-30511: Clarify that :func:`shutil.make_archive` is not thread-safe due
  to reliance on changing the current working directory.

- bpo-44561: Update of three expired hyperlinks in
  Doc/distributing/index.rst: "Project structure", "Building and packaging
  the project", and "Uploading the project to the Python Packaging Index".

- bpo-44613: importlib.metadata is no longer provisional.

- bpo-44544: List all kwargs for :func:`textwrap.wrap`,
  :func:`textwrap.fill`, and :func:`textwrap.shorten`. Now, there are nav
  links to attributes of :class:`TextWrap`, which makes navigation much
  easier while minimizing duplication in the documentation.

- bpo-44453: Fix documentation for the return type of
  :func:`sysconfig.get_path`.

Tests
-----

- bpo-44734: Fixed floating point precision issue in turtle tests.

- bpo-44708: Regression tests, when run with -w, are now re-running only the
  affected test methods instead of re-running the entire test file.

- bpo-44647: Added a permanent Unicode-valued environment variable to
  regression tests to ensure they handle this use case in the future. If
  your test environment breaks because of that, report a bug to us, and
  temporarily set PYTHONREGRTEST_UNICODE_GUARD=0 in your test environment.

- bpo-44515: Adjust recently added contextlib tests to avoid assuming the
  use of a refcounted GC

Windows
-------

- bpo-44572: Avoid consuming standard input in the :mod:`platform` module

- bpo-40263: This is a follow-on bug from
  https://bugs.python.org/issue26903. Once that is applied we run into an
  off-by-one assertion problem. The assert was not correct.

macOS
-----

- bpo-41972: The framework build's user header path in sysconfig is changed
  to add a 'pythonX.Y' component to match distutils's behavior.

- bpo-34932: Add socket.TCP_KEEPALIVE support for macOS. Patch by Shane
  Harvey.

Tools/Demos
-----------

- bpo-44756: In the Makefile for documentation (:file:`Doc/Makefile`), the
  ``build`` rule is dependent on the ``venv`` rule. Therefore, ``html``,
  ``latex``, and other build-dependent rules are also now dependent on
  ``venv``. The ``venv`` rule only performs an action if ``$(VENVDIR)`` does
  not exist. :file:`Doc/README.rst` was updated; most users now only need to
  type ``make html``.

C API
-----

- bpo-41103: Reverts removal of the old buffer protocol because they are
  part of stable ABI.

- bpo-42747: The ``Py_TPFLAGS_HAVE_VERSION_TAG`` type flag now does nothing.
  The ``Py_TPFLAGS_HAVE_AM_SEND`` flag (which was added in 3.10) is removed.
  Both were unnecessary because it is not possible to have type objects with
  the relevant fields missing.


What's New in Python 3.10.0 beta 4?
===================================

*Release date: 2021-07-10*

Security
--------

- bpo-41180: Add auditing events to the :mod:`marshal` module, and stop
  raising ``code.__init__`` events for every unmarshalled code object.
  Directly instantiated code objects will continue to raise an event, and
  audit event handlers should inspect or collect the raw marshal data. This
  reduces a significant performance overhead when loading from ``.pyc``
  files.

Core and Builtins
-----------------

- bpo-44562: Remove uses of :c:func:`PyObject_GC_Del` in error path when
  initializing :class:`types.GenericAlias`.

- bpo-41486: Fix a memory consumption and copying performance regression in
  earlier 3.10 beta releases if someone used an output buffer larger than
  4GiB with zlib.decompress on input data that expands that large.

- bpo-44553: Implement GC methods for ``types.Union`` to break reference
  cycles and prevent memory leaks.

- bpo-44523: Remove the pass-through for :func:`hash` of
  :class:`weakref.proxy` objects to prevent unintended consequences when the
  original referred object dies while the proxy is part of a hashable
  object. Patch by Pablo Galindo.

- bpo-44483: Fix a crash in ``types.Union`` objects when creating a union of
  an object with bad ``__module__`` field.

- bpo-44297: Make sure that the line number is set when entering a
  comprehension scope. Ensures that backtraces inclusing generator
  expressions show the correct line number.

- bpo-44456: Improve the syntax error when mixing positional and keyword
  patterns. Patch by Pablo Galindo.

- bpo-44368: Improve syntax errors for invalid "as" targets. Patch by Pablo
  Galindo

- bpo-44317: Improve tokenizer error with improved locations. Patch by Pablo
  Galindo.

- bpo-43667: Improve Unicode support in non-UTF locales on Oracle Solaris.
  This issue does not affect other Solaris systems.

Library
-------

- bpo-44558: Make the implementation consistency of
  :func:`~operator.indexOf` between C and Python versions. Patch by Dong-hee
  Na.

- bpo-34798: Break up paragraph about :class:`pprint.PrettyPrinter`
  construction parameters to make it easier to read.

- bpo-44516: Update vendored pip to 21.1.3

- bpo-44468: :func:`typing.get_type_hints` now finds annotations in classes
  and base classes with unexpected ``__module__``. Previously, it skipped
  those MRO elements.

- bpo-43977: Set the proper :const:`Py_TPFLAGS_MAPPING` and
  :const:`Py_TPFLAGS_SEQUENCE` flags for subclasses created before a parent
  has been registered as a :class:`collections.abc.Mapping` or
  :class:`collections.abc.Sequence`.

- bpo-44482: Fix very unlikely resource leak in :mod:`glob` in alternate
  Python implementations.

- bpo-44466: The :mod:`faulthandler` module now detects if a fatal error
  occurs during a garbage collector collection. Patch by Victor Stinner.

- bpo-44404: :mod:`tkinter`'s ``after()`` method now supports callables
  without the ``__name__`` attribute.

- bpo-44458: ``BUFFER_BLOCK_SIZE`` is now declared static, to avoid linking
  collisions when bz2, lmza or zlib are statically linked.

- bpo-44464: Remove exception for flake8 in deprecated importlib.metadata
  interfaces. Sync with importlib_metadata 4.6.

- bpo-44446: Take into account that ``lineno`` might be ``None`` in
  :class:`traceback.FrameSummary`.

- bpo-44439: Fix in :meth:`bz2.BZ2File.write` / :meth:`lzma.LZMAFile.write`
  methods, when the input data is an object that supports the buffer
  protocol, the file length may be wrong.

- bpo-44434: _thread.start_new_thread() no longer calls
  PyThread_exit_thread() explicitly at the thread exit, the call was
  redundant. On Linux with the glibc, pthread_exit() aborts the whole
  process if dlopen() fails to open libgcc_s.so file (ex: EMFILE error).
  Patch by Victor Stinner.

- bpo-44395: Fix :meth:`~email.message.MIMEPart.as_string` to pass unixfrom
  properly. Patch by Dong-hee Na.

- bpo-34266: Handle exceptions from parsing the arg of :mod:`pdb`'s
  run/restart command.

- bpo-44077: It's now possible to receive the type of service (ToS), a.k.a.
  differentiated services (DS), a.k.a. differenciated services code point
  (DSCP) and excplicit congestion notification (ECN) IP header fields with
  ``socket.IP_RECVTOS``.

- bpo-43024: Improve the help signature of
  :func:`traceback.print_exception`, :func:`traceback.format_exception` and
  :func:`traceback.format_exception_only`.

- bpo-30256: Pass multiprocessing BaseProxy argument ``manager_owned``
  through AutoProxy.

Documentation
-------------

- bpo-44558: Match the docstring and python implementation of
  :func:`~operator.countOf` to the behavior of its c implementation.

- bpo-38062: Clarify that atexit uses equality comparisons internally.

- bpo-40620: Convert examples in tutorial controlflow.rst section 4.3 to be
  interpreter-demo style.

- bpo-13814: In the Design FAQ, answer "Why don't generators support the
  with statement?"

- bpo-41621: Document that :class:`collections.defaultdict` parameter
  ``default_factory`` defaults to None and is positional-only.

Tests
-----

- bpo-44287: Fix asyncio test_popen() of test_windows_utils by using a
  longer timeout. Use military grade battle-tested
  :data:`test.support.SHORT_TIMEOUT` timeout rather than a hardcoded timeout
  of 10 seconds: it's 30 seconds by default, but it is made longer on slow
  buildbots. Patch by Victor Stinner.

- bpo-44451: Reset ``DeprecationWarning`` filters in
  ``test.test_importlib.test_metadata_api.APITests.test_entry_points_by_index``
  to avoid ``StopIteration`` error if ``DeprecationWarnings`` are ignored.

- bpo-30256: Add test for nested queues when using ``multiprocessing``
  shared objects ``AutoProxy[Queue]`` inside ``ListProxy`` and ``DictProxy``

Build
-----

- bpo-44535: Enable building using a Visual Studio 2022 install on Windows.

- bpo-43298: Improved error message when building without a Windows SDK
  installed.

Windows
-------

- bpo-44582: Accelerate speed of :mod:`mimetypes` initialization using a
  native implementation of the registry scan.

- bpo-41299: Fix 16ms jitter when using timeouts in :mod:`threading`, such
  as with :meth:`threading.Lock.acquire` or
  :meth:`threading.Condition.wait`.

C API
-----

- bpo-44441: :c:func:`Py_RunMain` now resets :c:data:`PyImport_Inittab` to
  its initial value at exit. It must be possible to call
  :c:func:`PyImport_AppendInittab` or :c:func:`PyImport_ExtendInittab` at
  each Python initialization. Patch by Victor Stinner.

- bpo-40939: Removed documentation for the removed ``PyParser_*`` C API.


What's New in Python 3.10.0 beta 3?
===================================

*Release date: 2021-06-17*

Core and Builtins
-----------------

- bpo-44409: Fix error location information for tokenizer errors raised on
  initialization of the tokenizer. Patch by Pablo Galindo.

- bpo-44396: Fix a possible crash in the tokenizer when raising syntax
  errors for unclosed strings. Patch by Pablo Galindo.

- bpo-44349: Fix an edge case when displaying text from files with encoding
  in syntax errors. Patch by Pablo Galindo.

- bpo-44335: Fix a regression when identifying incorrect characters in
  syntax errors. Patch by Pablo Galindo

- bpo-44304: Fix a crash in the :mod:`sqlite3` module that happened when the
  garbage collector clears :class:`sqlite.Statement` objects. Patch by Pablo
  Galindo

- bpo-44305: Improve error message for ``try`` blocks without ``except`` or
  ``finally`` blocks. Patch by Pablo Galindo.

- bpo-43833: Emit a deprecation warning if the numeric literal is
  immediately followed by one of keywords: and, else, for, if, in, is, or.
  Raise a syntax error with more informative message if it is immediately
  followed by other keyword or identifier.

- bpo-11105: When compiling :class:`ast.AST` objects with recursive
  references through :func:`compile`, the interpreter doesn't crash anymore
  instead it raises a :exc:`RecursionError`.

Library
-------

- bpo-42972: The _thread.RLock type now fully implement the GC protocol: add
  a traverse function and the :const:`Py_TPFLAGS_HAVE_GC` flag. Patch by
  Victor Stinner.

- bpo-44422: The :func:`threading.enumerate` function now uses a reentrant
  lock to prevent a hang on reentrant call. Patch by Victor Stinner.

- bpo-44389: Fix deprecation of :data:`ssl.OP_NO_TLSv1_3`

- bpo-44362: Improve :mod:`ssl` module's deprecation messages, error
  reporting, and documentation for deprecations.

- bpo-44342: [Enum] Change pickling from by-value to by-name.

- bpo-44356: [Enum] Allow multiple data-type mixins if they are all the
  same.

- bpo-44351: Restore back :func:`parse_makefile` in
  :mod:`distutils.sysconfig` because it behaves differently than the similar
  implementation in :mod:`sysconfig`.

- bpo-44242: Remove missing flag check from Enum creation and move into a
  ``verify`` decorator.

- bpo-44246: In ``importlib.metadata``, restore compatibility in the result
  from ``Distribution.entry_points`` (``EntryPoints``) to honor expectations
  in older implementations and issuing deprecation warnings for these cases:
  A. ``EntryPoints`` objects are once again mutable, allowing   for
  ``sort()`` and other list-based mutation operations.   Avoid deprecation
  warnings by casting to a   mutable sequence (e.g.
  ``list(dist.entry_points).sort()``). B. ``EntryPoints`` results once again
  allow   for access by index. To avoid deprecation warnings,   cast the
  result to a Sequence first   (e.g. ``tuple(dist.entry_points)[0]``).

- bpo-44246: In importlib.metadata.entry_points, de-duplication of
  distributions no longer requires loading the full metadata for
  PathDistribution objects, improving entry point loading performance by
  ~10x.

- bpo-43853: Improved string handling for :mod:`sqlite3` user-defined
  functions and aggregates:

  * It is now possible to pass strings with embedded null characters to UDFs
  * Conversion failures now correctly raise :exc:`MemoryError`

  Patch by Erlend E. Aasland.

- bpo-43318: Fix a bug where :mod:`pdb` does not always echo cleared
  breakpoints.

- bpo-37022: :mod:`pdb` now displays exceptions from ``repr()`` with its
  ``p`` and ``pp`` commands.

Documentation
-------------

- bpo-44392: Added a new section in the C API documentation for types used
  in type hinting.  Documented ``Py_GenericAlias`` and
  ``Py_GenericAliasType``.

- bpo-38291: Mark ``typing.io`` and ``typing.re`` as deprecated since Python
  3.8 in the documentation. They were never properly supported by type
  checkers.

- bpo-44322: Document that SyntaxError args have a details tuple and that
  details are adjusted for errors in f-string field replacement expressions.

Tests
-----

- bpo-44363: Account for address sanitizer in test_capi. test_capi now
  passes when run GCC address sanitizer.

- bpo-43921: Fix test_ssl.test_wrong_cert_tls13(): use
  ``suppress_ragged_eofs=False``, since ``read()`` can raise
  :exc:`ssl.SSLEOFError` on Windows. Patch by Victor Stinner.

- bpo-43921: Fix test_pha_required_nocert() of test_ssl: catch two more EOF
  cases (when the ``recv()`` method returns an empty string). Patch by
  Victor Stinner.

Build
-----

- bpo-44381: The Windows build now accepts :envvar:`EnableControlFlowGuard`
  set to ``guard`` to enable CFG.

IDLE
----

- bpo-40128: Mostly fix completions on macOS when not using tcl/tk 8.6.11
  (as with 3.9). The added update_idletask call should be harmless and
  possibly helpful otherwise.

- bpo-33962: Move the indent space setting from the Font tab to the new
  Windows tab. Patch by Mark Roseman and Terry Jan Reedy.

- bpo-40468: Split the settings dialog General tab into Windows and Shell/ED
  tabs. Move help sources, which extend the Help menu, to the Extensions
  tab. Make space for new options and shorten the dialog. The latter makes
  the dialog better fit small screens.

C API
-----

- bpo-43795: The list in :ref:`stable-abi-list` now shows the public name
  :c:struct:`PyFrameObject` rather than ``_frame``. The non-existing entry
  ``_node`` no longer appears in the list.

- bpo-44378: :c:func:`Py_IS_TYPE` no longer uses :c:func:`Py_TYPE` to avoid
  a compiler warning: no longer cast ``const PyObject*`` to ``PyObject*``.
  Patch by Victor Stinner.


What's New in Python 3.10.0 beta 2?
===================================

*Release date: 2021-05-31*

Security
--------

- bpo-44022: mod:`http.client` now avoids infinitely reading potential HTTP
  headers after a ``100 Continue`` status response from the server.

Core and Builtins
-----------------

- bpo-43667: Improve Unicode support in non-UTF locales on Oracle Solaris.
  This issue does not affect other Solaris systems.

- bpo-44232: Fix a regression in :func:`type` when a metaclass raises an
  exception. The C function :c:func:`type_new` must properly report the
  exception when a metaclass constructor raises an exception and the winner
  class is not the metaclass. Patch by Victor Stinner.

- bpo-44201: Avoid side effects of checking for specialized syntax errors in
  the REPL that was causing it to ask for extra tokens after a syntax error
  had been detected. Patch by Pablo Galindo

- bpo-44184: Fix a crash at Python exit when a deallocator function removes
  the last strong reference to a heap type. Patch by Victor Stinner.

- bpo-44180: The parser doesn't report generic syntax errors that happen in
  a position further away that the one it reached in the first pass. Patch
  by Pablo Galindo

- bpo-44168: Fix error message in the parser involving keyword arguments
  with invalid expressions. Patch by Pablo Galindo

- bpo-44143: Fixed a crash in the parser that manifest when raising
  tokenizer errors when an existing exception was present. Patch by Pablo
  Galindo.

- bpo-44114: Fix incorrect dictkeys_reversed and dictitems_reversed function
  signatures in C code, which broke webassembly builds.

- bpo-43149: Corrent the syntax error message regarding multiple exception
  types to not refer to "exception groups". Patch by Pablo Galindo

- bpo-44056: Syntax errors when default ``except`` is not the last
  ``except``  are reported with the correct location. Patch by Mark Shannon.

- bpo-43822: The parser will prioritize tokenizer errors over custom syntax
  errors when raising exceptions. Patch by Pablo Galindo.

- bpo-28146: Fix a confusing error message in :func:`str.format`.

Library
-------

- bpo-44254: On Mac, give turtledemo button text a color that works on both
  light or dark background.  Programmers cannot control the latter.

- bpo-38693: Prefer f-strings to ``.format`` in importlib.resources.

- bpo-33693: Importlib.metadata now prefers f-strings to .format.

- bpo-44241: Incorporate minor tweaks from importlib_metadata 4.1:
  SimplePath protocol, support for Metadata 2.2.

- bpo-44210: Make importlib.metadata._meta.PackageMetadata public.

- bpo-43643: Declare readers.MultiplexedPath.name as a property per the
  spec.

- bpo-33433: For IPv4 mapped IPv6 addresses (:rfc:`4291` Section 2.5.5.2),
  the :mod:`ipaddress.IPv6Address.is_private` check is deferred to the
  mapped IPv4 address. This solves a bug where public mapped IPv4 addresses
  were considered private by the IPv6 check.

- bpo-44145: :mod:`hmac` computations were not releasing the GIL while
  calling the OpenSSL ``HMAC_Update`` C API (a new feature in 3.9).  This
  unintentionally prevented parallel computation as other :mod:`hashlib`
  algorithms support.

- bpo-37788: Fix a reference leak when a Thread object is never joined.

- bpo-38908: Subclasses of ``typing.Protocol`` which only have data
  variables declared will now raise a ``TypeError`` when checked with
  ``isinstance`` unless they are decorated with :func:`runtime_checkable`.
  Previously, these checks passed silently. Patch provided by Yurii Karabas.

- bpo-44098: ``typing.ParamSpec`` will no longer be found in the
  ``__parameters__`` of most :mod:`typing` generics except in valid use
  locations specified by :pep:`612`. This prevents incorrect usage like
  ``typing.List[P][int]``. This change means incorrect usage which may have
  passed silently in 3.10 beta 1 and earlier will now error.

- bpo-44089: Allow subclassing ``csv.Error`` in 3.10 (it was allowed in 3.9
  and earlier but was disallowed in early versions of 3.10).

- bpo-44059: Register the SerenityOS Browser in the :mod:`webbrowser`
  module.

- bpo-36515: The :mod:`hashlib` module no longer does unaligned memory
  accesses when compiled for ARM platforms.

- bpo-44018: random.seed() no longer mutates bytearray inputs.

- bpo-38352: Add ``IO``, ``BinaryIO``, ``TextIO``, ``Match``, and
  ``Pattern`` to ``typing.__all__``. Patch by Jelle Zijlstra.

- bpo-43972: When :class:`http.server.SimpleHTTPRequestHandler` sends a
  ``301 (Moved Permanently)`` for a directory path not ending with `/`, add
  a ``Content-Length: 0`` header. This improves the behavior for certain
  clients.

- bpo-28528: Fix a bug in :mod:`pdb` where :meth:`~pdb.Pdb.checkline` raises
  :exc:`AttributeError` if it is called after :meth:`~pdb.Pdb.reset`.

- bpo-43650: Fix :exc:`MemoryError` in :func:`shutil.unpack_archive` which
  fails inside :func:`shutil._unpack_zipfile` on large files. Patch by Igor
  Bolshakov.

- bpo-41730: ``DeprecationWarning`` is now raised when importing
  :mod:`tkinter.tix`, which has been deprecated in documentation since
  Python 3.6.

Documentation
-------------

- bpo-42392: Document the deprecation and removal of the ``loop`` parameter
  for many functions and classes in :mod:`asyncio`.

- bpo-44195: Corrected references to ``TraversableResources`` in docs. There
  is no ``TraversableReader``.

- bpo-41963: Document that ``ConfigParser`` strips off comments when reading
  configuration files.

- bpo-44072: Correct where in the numeric ABC hierarchy ``**`` support is
  added, i.e., in numbers.Complex, not numbers.Integral.

- bpo-43558: Add the remark to :mod:`dataclasses` documentation that the
  :meth:`__init__` of any base class has to be called in
  :meth:`__post_init__`, along with a code example.

- bpo-44025: Clarify when '_' in match statements is a keyword, and when
  not.

Tests
-----

- bpo-31904: Ignore error string case in test_py_compile
  ``test_file_not_exists()``.

- bpo-42083: Add test to check that ``PyStructSequence_NewType`` accepts a
  ``PyStructSequence_Desc`` with ``doc`` field set to ``NULL``.

- bpo-35753: Fix crash in doctest when doctest parses modules that include
  unwrappable functions by skipping those functions.

Build
-----

- bpo-41282: Fix broken ``make install`` that caused standard library
  extension modules to be unnecessarily and incorrectly rebuilt during the
  install phase of cpython.

Windows
-------

- bpo-42686: Build :mod:`sqlite3` with math functions enabled. Patch by
  Erlend E. Aasland.

macOS
-----

- bpo-43109: Allow --with-lto configure option to work with Apple-supplied
  Xcode or Command Line Tools.

IDLE
----

- bpo-41611: Avoid uncaught exceptions in
  ``AutoCompleteWindow.winconfig_event()``.

- bpo-41611: Fix IDLE sometimes freezing upon tab-completion on macOS.

- bpo-44010: Highlight the new :ref:`match <match>` statement's :ref:`soft
  keywords <soft-keywords>`: :keyword:`match`, :keyword:`case <match>`, and
  :keyword:`_ <wildcard-patterns>`. However, this highlighting is not
  perfect and will be incorrect in some rare cases, including some ``_``-s
  in ``case`` patterns.

- bpo-44026: Include interpreter's typo fix suggestions in message line for
  NameErrors and AttributeErrors.  Patch by E. Paine.

Tools/Demos
-----------

- bpo-44074: Make patchcheck automatically detect the correct base branch
  name (previously it was hardcoded to 'master')

C API
-----

- bpo-43795: The undocumented function :c:func:`Py_FrozenMain` is removed
  from the Limited API.

- bpo-43795: :c:func:`PyCodec_Unregister` is now properly exported as a
  function in the Windows Stable ABI DLL.


What's New in Python 3.10.0 beta 1?
===================================

*Release date: 2021-05-03*

Security
--------

- bpo-43434: Creating :class:`sqlite3.Connection` objects now also produces
  ``sqlite3.connect`` and ``sqlite3.connect/handle`` :ref:`auditing events
  <auditing>`. Previously these events were only produced by
  :func:`sqlite3.connect` calls. Patch by Erlend E. Aasland.

- bpo-43998: The :mod:`ssl` module sets more secure cipher suites defaults.
  Ciphers without forward secrecy and with SHA-1 MAC are disabled by
  default. Security level 2 prohibits weak RSA, DH, and ECC keys with less
  than 112 bits of security. :class:`~ssl.SSLContext` defaults to minimum
  protocol version TLS 1.2. Settings are based on Hynek Schlawack's
  research.

- bpo-43882: The presence of newline or tab characters in parts of a URL
  could allow some forms of attacks.

  Following the controlling specification for URLs defined by WHATWG
  :func:`urllib.parse` now removes ASCII newlines and tabs from URLs,
  preventing such attacks.

- bpo-43472: Ensures interpreter-level audit hooks receive the
  ``cpython.PyInterpreterState_New`` event when called through the
  ``_xxsubinterpreters`` module.

- bpo-43362: Fix invalid free in _sha3 module. The issue was introduced in
  3.10.0a1. Python 3.9 and earlier are not affected.

- bpo-43762: Add audit events for :func:`sqlite3.connect/handle`,
  :meth:`sqlite3.Connection.enable_load_extension`, and
  :meth:`sqlite3.Connection.load_extension`. Patch by Erlend E. Aasland.

- bpo-43756: Add new audit event ``glob.glob/2`` to incorporate the new
  *root_dir* and *dir_fd* arguments added to :func:`glob.glob` and
  :func:`glob.iglob`.

- bpo-36384: :mod:`ipaddress` module no longer accepts any leading zeros in
  IPv4 address strings. Leading zeros are ambiguous and interpreted as octal
  notation by some libraries. For example the legacy function
  :func:`socket.inet_aton` treats leading zeros as octal notatation. glibc
  implementation of modern :func:`~socket.inet_pton` does not accept any
  leading zeros. For a while the :mod:`ipaddress` module used to accept
  ambiguous leading zeros.

- bpo-43075: Fix Regular Expression Denial of Service (ReDoS) vulnerability
  in :class:`urllib.request.AbstractBasicAuthHandler`.  The ReDoS-vulnerable
  regex has quadratic worst-case complexity and it allows cause a denial of
  service when identifying crafted invalid RFCs. This ReDoS issue is on the
  client side and needs remote attackers to control the HTTP server.

- bpo-42800: Audit hooks are now fired for frame.f_code, traceback.tb_frame,
  and generator code/frame attribute access.

- bpo-37363: Add audit events to the :mod:`http.client` module.

Core and Builtins
-----------------

- bpo-43977: Prevent classes being both a sequence and a mapping when
  pattern matching.

- bpo-43977: Use :c:member:`~PyTypeObject.tp_flags` on the class object to
  determine if the subject is a sequence or mapping when pattern matching.
  Avoids the need to import :mod:`collections.abc` when pattern matching.

- bpo-43892: Restore proper validation of complex literal value patterns
  when parsing :keyword:`!match` blocks.

- bpo-43933: Set frame.f_lineno to the line number of the 'with' kweyword
  when executing the call to ``__exit__``.

- bpo-43933: If the current position in a frame has no line number then set
  the f_lineno attribute to None, instead of -1, to conform to PEP 626. This
  should not normally be possible, but might occur in some unusual
  circumstances.

- bpo-43963: Importing the :mod:`_signal` module in a subinterpreter has no
  longer side effects.

- bpo-42739: The internal representation of line number tables is changed to
  not use sentinels, and an explicit length parameter is added to the out of
  process API function ``PyLineTable_InitAddressRange``. This makes the
  handling of line number tables more robust in some circumstances.

- bpo-43908: Make :mod:`re` types immutable. Patch by Erlend E. Aasland.

- bpo-43908: Make the :class:`array.array` type immutable. Patch by Erlend
  E. Aasland.

- bpo-43901: Change class and module objects to lazy-create empty
  annotations dicts on demand.  The annotations dicts are stored in the
  object's __dict__ for backwards compatibility.

- bpo-43892: Match patterns now use new dedicated AST nodes (``MatchValue``,
  ``MatchSingleton``, ``MatchSequence``, ``MatchStar``, ``MatchMapping``,
  ``MatchClass``) rather than reusing expression AST nodes. ``MatchAs`` and
  ``MatchOr`` are now defined as pattern nodes rather than as expression
  nodes. Patch by Nick Coghlan.

- bpo-42725: Usage of ``await``/``yield``/``yield from`` and named
  expressions within an annotation is now forbidden when PEP 563 is
  activated.

- bpo-43754: When performing structural pattern matching (:pep:`634`),
  captured names are now left unbound until the *entire* pattern has matched
  successfully.

- bpo-42737: Annotations for complex targets (everything beside simple
  names) no longer cause any runtime effects with ``from __future__ import
  annotations``.

- bpo-43914: :exc:`SyntaxError` exceptions raised by the interpreter will
  highlight the full error range of the expression that consistutes the
  syntax error itself, instead of just where the problem is detected. Patch
  by Pablo Galindo.

- bpo-38605: Revert making ``from __future__ import annotations`` the
  default. This follows the Steering Council decision to postpone PEP 563
  changes to at least Python 3.11. See the original email for more
  information regarding the decision:
  https://mail.python.org/archives/list/python-dev@python.org/thread/CLVXXPQ2T2LQ5MP2Y53VVQFCXYWQJHKZ/.
  Patch by Pablo Galindo.

- bpo-43475: Hashes of NaN values now depend on object identity.  Formerly,
  they always hashed to 0 even though NaN values are not equal to one
  another.  Having the same hash for unequal values caused pile-ups in hash
  tables.

- bpo-43859: Improve the error message for :exc:`IndentationError`
  exceptions. Patch by Pablo Galindo

- bpo-41323: Constant tuple folding in bytecode optimizer now reuses tuple
  in constant table.

- bpo-43846: Data stack usage is much reduced for large literal and call
  expressions.

- bpo-38530: When printing :exc:`NameError` raised by the interpreter,
  :c:func:`PyErr_Display` will offer suggestions of similar variable names
  in the function that the exception was raised from. Patch by Pablo Galindo

- bpo-43823: Improve syntax errors for invalid dictionary literals. Patch by
  Pablo Galindo.

- bpo-43822: Improve syntax errors in the parser for missing commas between
  expressions. Patch by Pablo Galindo.

- bpo-43798: :class:`ast.alias` nodes now include source location metadata
  attributes e.g. lineno, col_offset.

- bpo-43797: Improve ``SyntaxError`` error messages for invalid comparisons.
  Patch by Pablo Galindo.

- bpo-43760: Move the flag for checking whether tracing is enabled to the C
  stack, from the heap. Should speed up dispatch in the interpreter.

- bpo-43682: Static methods (:func:`@staticmethod <staticmethod>`) and class
  methods (:func:`@classmethod <classmethod>`) now inherit the method
  attributes (``__module__``, ``__name__``, ``__qualname__``, ``__doc__``,
  ``__annotations__``) and have a new ``__wrapped__`` attribute. Patch by
  Victor Stinner.

- bpo-43751: Fixed a bug where ``anext(ait, default)`` would erroneously
  return None.

- bpo-42128: :data:`~object.__match_args__` is no longer allowed to be a
  list.

- bpo-43683: Add GEN_START opcode. Marks start of generator, including
  async, or coroutine and handles sending values to a newly created
  generator or coroutine.

- bpo-43105: Importlib now resolves relative paths when creating module spec
  objects from file locations.

- bpo-43682: Static methods (:func:`@staticmethod <staticmethod>`) are now
  callable as regular functions. Patch by Victor Stinner.

- bpo-42609: Prevented crashes in the AST validator and optimizer when
  compiling some absurdly long expressions like ``"+0"*1000000``.
  :exc:`RecursionError` is now raised instead.

- bpo-38530: When printing :exc:`AttributeError`, :c:func:`PyErr_Display`
  will offer suggestions of similar attribute names in the object that the
  exception was raised from. Patch by Pablo Galindo

Library
-------

- bpo-44015: In @dataclass(), raise a TypeError if KW_ONLY is specified more
  than once.

- bpo-25478: Added a *total()* method to collections.Counter() to compute
  the sum of the counts.

- bpo-43733: Change :class:`netrc.netrc` to use UTF-8 encoding before using
  locale encoding.

- bpo-43979: Removed an unnecessary list comprehension before looping from
  :func:`urllib.parse.parse_qsl`.  Patch by Christoph Zwerschke and Dong-hee
  Na.

- bpo-43993: Update bundled pip to 21.1.1.

- bpo-43957: [Enum] Deprecate ``TypeError`` when non-member is used in a
  containment check; In 3.12 ``True`` or ``False`` will be returned instead,
  and containment will return ``True`` if the value is either a member of
  that enum or one of its members' value.

- bpo-42904: For backwards compatibility with previous minor versions of
  Python, if :func:`typing.get_type_hints` receives no namespace dictionary
  arguments, :func:`typing.get_type_hints` will search through the global
  then local namespaces during evaluation of stringized type annotations
  (string forward references) inside a class.

- bpo-43945: [Enum] Deprecate non-standard mixin format() behavior: in 3.12
  the enum member, not the member's value, will be used for format() calls.

- bpo-41139: Deprecate undocumented ``cgi.log()`` API.

- bpo-43937: Fixed the :mod:`turtle` module working with non-default root
  window.

- bpo-43930: Update bundled pip to 21.1 and setuptools to 56.0.0

- bpo-43907: Fix a bug in the pure-Python pickle implementation when using
  protocol 5, where bytearray instances that occur several time in the
  pickled object graph would incorrectly unpickle into repeated copies of
  the bytearray object.

- bpo-43926: In ``importlib.metadata``, provide a uniform interface to
  ``Description``, allow for any field to be encoded with multiline values,
  remove continuation lines from multiline values, and add a ``.json``
  property for easy access to the PEP 566 JSON-compatible form. Sync with
  ``importlib_metadata 4.0``.

- bpo-43920: OpenSSL 3.0.0: :meth:`~ssl.SSLContext.load_verify_locations`
  now returns a consistent error message when cadata contains no valid
  certificate.

- bpo-43607: :mod:`urllib` can now convert Windows paths with ``\\?\``
  prefixes into URL paths.

- bpo-43817: Add :func:`inspect.get_annotations`, which safely computes the
  annotations defined on an object.  It works around the quirks of accessing
  the annotations from various types of objects, and makes very few
  assumptions about the object passed in. :func:`inspect.get_annotations`
  can also correctly un-stringize stringized annotations.

  :func:`inspect.signature`, :func:`inspect.from_callable`, and
  :func:`inspect.from_function` now call :func:`inspect.get_annotations` to
  retrieve annotations.  This means :func:`inspect.signature` and
  :func:`inspect.from_callable` can now un-stringize stringized annotations,
  too.

- bpo-43284: platform.win32_ver derives the windows version from
  sys.getwindowsversion().platform_version which in turn derives the version
  from kernel32.dll (which can be of a different version than Windows
  itself). Therefore change the platform.win32_ver to determine the version
  using the platform module's _syscmd_ver private function to return an
  accurate version.

- bpo-42854: The :mod:`ssl` module now uses ``SSL_read_ex`` and
  ``SSL_write_ex`` internally. The functions support reading and writing of
  data larger than 2 GB. Writing zero-length data no longer fails with a
  protocol violation error.

- bpo-42333: Port ``_ssl`` extension module to multiphase initialization.

- bpo-43880: :mod:`ssl` now raises DeprecationWarning for OP_NO_SSL/TLS*
  options, old TLS versions, old protocols, and other features that have
  been deprecated since Python 3.6, 3.7, or OpenSSL 1.1.0.

- bpo-41559: :pep:`612` is now implemented purely in Python; builtin
  ``types.GenericAlias`` objects no longer include ``typing.ParamSpec`` in
  ``__parameters__`` (with the exception of ``collections.abc.Callable``\ 's
  ``GenericAlias``). This means previously invalid uses of ``ParamSpec``
  (such as ``list[P]``) which worked in earlier versions of Python 3.10
  alpha, will now raise ``TypeError`` during substitution.

- bpo-43867: The :mod:`multiprocessing` ``Server`` class now explicitly
  catches :exc:`SystemExit` and closes the client connection in this case.
  It happens when the ``Server.serve_client()`` method reaches the end of
  file (EOF).

- bpo-40443: Remove unused imports: pyclbr no longer uses copy, and typing
  no longer uses ast. Patch by Victor Stinner.

- bpo-43820: Remove an unneeded copy of the namespace passed to
  dataclasses.make_dataclass().

- bpo-43787: Add ``__iter__()`` method to :class:`bz2.BZ2File`,
  :class:`gzip.GzipFile`, and :class:`lzma.LZMAFile`. It makes iterating
  them about 2x faster. Patch by Inada Naoki.

- bpo-43680: Deprecate io.OpenWrapper and _pyio.OpenWrapper: use io.open and
  _pyio.open instead. Until Python 3.9, _pyio.open was not a static method
  and builtins.open was set to OpenWrapper to not become a bound method when
  set to a class variable. _io.open is a built-in function whereas
  _pyio.open is a Python function. In Python 3.10, _pyio.open() is now a
  static method, and builtins.open() is now io.open().

- bpo-43680: The Python :func:`_pyio.open` function becomes a static method
  to behave as :func:`io.open` built-in function: don't become a bound
  method when stored as a class variable. It becomes possible since static
  methods are now callable in Python 3.10. Moreover,
  :func:`_pyio.OpenWrapper` becomes a simple alias to :func:`_pyio.open`.
  Patch by Victor Stinner.

- bpo-41515: Fix :exc:`KeyError` raised in :func:`typing.get_type_hints` due
  to synthetic modules that don't appear in ``sys.modules``.

- bpo-43776: When :class:`subprocess.Popen` args are provided as a string or
  as :class:`pathlib.Path`, the Popen instance repr now shows the right
  thing.

- bpo-42248: [Enum] ensure exceptions raised in ``_missing__`` are released

- bpo-43744: fix issue with enum member name matching the start of a private
  variable name

- bpo-43772: Fixed the return value of ``TypeVar.__ror__``. Patch by Jelle
  Zijlstra.

- bpo-43764: Add match_args parameter to @dataclass decorator to allow
  suppression of __match_args__ generation.

- bpo-43799: OpenSSL 3.0.0: define ``OPENSSL_API_COMPAT`` 1.1.1 to suppress
  deprecation warnings. Python requires OpenSSL 1.1.1 APIs.

- bpo-43478: Mocks can no longer be used as the specs for other Mocks. As a
  result, an already-mocked object cannot have an attribute mocked using
  ``autospec=True`` or be the subject of a ``create_autospec(...)`` call.
  This can uncover bugs in tests since these Mock-derived Mocks will always
  pass certain tests (e.g. :func:`isinstance`) and builtin assert functions
  (e.g. assert_called_once_with) will unconditionally pass.

- bpo-43794: Add :data:`ssl.OP_IGNORE_UNEXPECTED_EOF` constants (OpenSSL
  3.0.0)

- bpo-43785: Improve ``bz2.BZ2File`` performance by removing the RLock from
  BZ2File. This makes BZ2File thread unsafe in the face of multiple
  simultaneous readers or writers, just like its equivalent classes in
  :mod:`gzip` and :mod:`lzma` have always been.  Patch by Inada Naoki.

- bpo-43789: OpenSSL 3.0.0: Don't call the password callback function a
  second time when first call has signaled an error condition.

- bpo-43788: The header files for :mod:`ssl` error codes are now OpenSSL
  version-specific. Exceptions will now show correct reason and library
  codes. The ``make_ssl_data.py`` script has been rewritten to use OpenSSL's
  text file with error codes.

- bpo-43766: Implement :pep:`647` in the :mod:`typing` module by adding
  :data:`TypeGuard`.

- bpo-25264: :func:`os.path.realpath` now accepts a *strict* keyword-only
  argument. When set to ``True``, :exc:`OSError` is raised if a path doesn't
  exist or a symlink loop is encountered.

- bpo-43780: In ``importlib.metadata``, incorporate changes from
  importlib_metadata 3.10: Add mtime-based caching during distribution
  discovery. Flagged use of dict result from ``entry_points()`` as
  deprecated.

- The ``P.args`` and ``P.kwargs`` attributes of :class:`typing.ParamSpec`
  are now instances of the new classes :class:`typing.ParamSpecArgs` and
  :class:`typing.ParamSpecKwargs`, which enables a more useful ``repr()``.
  Patch by Jelle Zijlstra.

- bpo-43731: Add an ``encoding`` parameter :func:`logging.fileConfig()`.

- bpo-43712: Add ``encoding`` and ``errors`` parameters to
  :func:`fileinput.input` and :class:`fileinput.FileInput`.

- bpo-38659: A ``simple_enum`` decorator is added to the ``enum`` module to
  convert a normal class into an Enum. ``test_simple_enum`` added to test
  simple enums against a corresponding normal Enum.  Standard library
  modules updated to use ``simple_enum``.

- bpo-43764: Fix an issue where :data:`~object.__match_args__` generation
  could fail for some :mod:`dataclasses`.

- bpo-43752: Fix :mod:`sqlite3` regression for zero-sized blobs with
  converters, where ``b""`` was returned instead of ``None``. The regression
  was introduced by PR 24723. Patch by Erlend E. Aasland.

- bpo-43655: :mod:`tkinter` dialog windows are now recognized as dialogs by
  window managers on macOS and X Window.

- bpo-43723: The following ``threading`` methods are now deprecated and
  should be replaced:

  - ``currentThread`` => :func:`threading.current_thread`

  - ``activeCount`` => :func:`threading.active_count`

  - ``Condition.notifyAll`` => :meth:`threading.Condition.notify_all`

  - ``Event.isSet`` => :meth:`threading.Event.is_set`

  - ``Thread.setName`` => :attr:`threading.Thread.name`

  - ``thread.getName`` => :attr:`threading.Thread.name`

  - ``Thread.isDaemon`` => :attr:`threading.Thread.daemon`

  - ``Thread.setDaemon`` => :attr:`threading.Thread.daemon`

  Patch by Jelle Zijlstra.

- bpo-2135: Deprecate find_module() and find_loader() implementations in
  importlib and zipimport.

- bpo-43534: :func:`turtle.textinput` and :func:`turtle.numinput` create now
  a transient window working on behalf of the canvas window.

- bpo-43532: Add the ability to specify keyword-only fields to dataclasses.
  These fields will become keyword-only arguments to the generated __init__.

- bpo-43522: Fix problem with
  :attr:`~ssl.SSLContext.hostname_checks_common_name`. OpenSSL does not copy
  hostflags from *struct SSL_CTX* to *struct SSL*.

- bpo-8978: Improve error message for :func:`tarfile.open` when :mod:`lzma`
  / :mod:`bz2` are unavailable.  Patch by Anthony Sottile.

- bpo-42967: Allow :class:`bytes` ``separator`` argument in
  ``urllib.parse.parse_qs`` and ``urllib.parse.parse_qsl`` when parsing
  :class:`str` query strings. Previously, this raised a ``TypeError``.

- bpo-43296: Improve :mod:`sqlite3` error handling: ``sqlite3_value_blob()``
  errors that set ``SQLITE_NOMEM`` now raise :exc:`MemoryError`. Patch by
  Erlend E. Aasland.

- bpo-43312: New functions :func:`sysconfig.get_preferred_scheme` and
  :func:`sysconfig.get_default_scheme` are added to query a platform for its
  preferred "user", "home", and "prefix" (default) scheme names.

- bpo-43265: Improve :meth:`sqlite3.Connection.backup` error handling. The
  error message for non-existent target database names is now ``unknown
  database <database name>`` instead of ``SQL logic error``. Patch by Erlend
  E. Aasland.

- bpo-41282: Install schemes in :mod:`distutils.command.install` are now
  loaded from :mod:`sysconfig`.

- bpo-41282: :mod:`distutils.sysconfig` has been merged to :mod:`sysconfig`.

- bpo-43176: Fixed processing of a dataclass that inherits from a frozen
  dataclass with no fields.  It is now correctly detected as an error.

- bpo-43080: :mod:`pprint` now has support for
  :class:`dataclasses.dataclass`. Patch by Lewis Gaul.

- bpo-39950: Add `pathlib.Path.hardlink_to()` method that supersedes
  `link_to()`. The new method has the same argument order as `symlink_to()`.

- bpo-42904: :func:`typing.get_type_hints` now checks the local namespace of
  a class when evaluating :pep:`563` annotations inside said class.

- bpo-42269: Add ``slots`` parameter to ``dataclasses.dataclass`` decorator
  to automatically generate ``__slots__`` for class. Patch provided by Yurii
  Karabas.

- bpo-39529: Deprecated use of :func:`asyncio.get_event_loop` without
  running event loop. Emit deprecation warning for :mod:`asyncio` functions
  which implicitly create a :class:`~asyncio.Future` or
  :class:`~asyncio.Task` objects if there is no running event loop and no
  explicit *loop* argument is passed: :func:`~asyncio.ensure_future`,
  :func:`~asyncio.wrap_future`, :func:`~asyncio.gather`,
  :func:`~asyncio.shield`, :func:`~asyncio.as_completed` and constructors of
  :class:`~asyncio.Future`, :class:`~asyncio.Task`,
  :class:`~asyncio.StreamReader`, :class:`~asyncio.StreamReaderProtocol`.

- bpo-18369: Certificate and PrivateKey classes were added to the ssl
  module. Certificates and keys can now be loaded from memory buffer, too.

- bpo-41486: Use a new output buffer management code for :mod:`bz2` /
  :mod:`lzma` / :mod:`zlib` modules, and add ``.readall()`` function to
  ``_compression.DecompressReader`` class. These bring some performance
  improvements. Patch by Ma Lin.

- bpo-31870: The :func:`ssl.get_server_certificate` function now has a
  *timeout* parameter.

- bpo-41735: Fix thread locks in zlib module may go wrong in rare case.
  Patch by Ma Lin.

- bpo-36470: Fix dataclasses with ``InitVar``\s and
  :func:`~dataclasses.replace()`. Patch by Claudiu Popa.

- bpo-40849: Expose X509_V_FLAG_PARTIAL_CHAIN ssl flag

- bpo-35114: :func:`ssl.RAND_status` now returns a boolean value (as
  documented) instead of ``1`` or ``0``.

- bpo-39906: :meth:`pathlib.Path.stat` and :meth:`~pathlib.Path.chmod` now
  accept a *follow_symlinks* keyword-only argument for consistency with
  corresponding functions in the :mod:`os` module.

- bpo-39899: :func:`os.path.expanduser()` now refuses to guess Windows home
  directories if the basename of current user's home directory does not
  match their username.

  :meth:`pathlib.Path.expanduser()` and :meth:`~pathlib.Path.home()` now
  consistently raise :exc:`RuntimeError` exception when a home directory
  cannot be resolved. Previously a :exc:`KeyError` exception could be raised
  on Windows when the ``"USERNAME"``  environment variable was unset.

- bpo-36076: Added SNI support to :func:`ssl.get_server_certificate`.

- bpo-38490: Covariance, Pearson's correlation, and simple linear regression
  functionality was added to statistics module. Patch by Tymoteusz Wołodźko.

- bpo-33731: Provide a locale.localize() function, which converts a
  normalized number string into a locale format.

- bpo-32745: Fix a regression in the handling of ctypes'
  :data:`ctypes.c_wchar_p` type: embedded null characters would cause a
  :exc:`ValueError` to be raised. Patch by Zackery Spytz.

Documentation
-------------

- bpo-43987: Add "Annotations Best Practices" document as a new HOWTO.

- bpo-43977: Document the new :const:`Py_TPFLAGS_MAPPING` and
  :const:`Py_TPFLAGS_SEQUENCE` type flags.

- bpo-43959: The documentation on the PyContextVar C-API was clarified.

- bpo-43938: Update dataclasses documentation to express that
  FrozenInstanceError is derived from AttributeError.

- bpo-43778: Fix the Sphinx glossary_search extension: create the _static/
  sub-directory if it doesn't exist.

- bpo-43755: Update documentation to reflect that unparenthesized lambda
  expressions can no longer be the expression part in an ``if`` clause in
  comprehensions and generator expressions since Python 3.9.

- bpo-43739: Fixing the example code in Doc/extending/extending.rst to
  declare and initialize the pmodule variable to be of the right type.

Tests
-----

- bpo-43961: Fix test_logging.test_namer_rotator_inheritance() on Windows:
  use :func:`os.replace` rather than :func:`os.rename`. Patch by Victor
  Stinner.

- bpo-43842: Fix a race condition in the SMTP test of test_logging. Don't
  close a file descriptor (socket) from a different thread while
  asyncore.loop() is polling the file descriptor. Patch by Victor Stinner.

- bpo-43843: :mod:`test.libregrtest` now marks a test as ENV_CHANGED
  (altered the execution environment) if a thread raises an exception but
  does not catch it. It sets a hook on :func:`threading.excepthook`. Use
  ``--fail-env-changed`` option to mark the test as failed. Patch by Victor
  Stinner.

- bpo-43811: Tests multiple OpenSSL versions on GitHub Actions. Use ccache
  to speed up testing.

- bpo-43791: OpenSSL 3.0.0: Disable testing of legacy protocols TLS 1.0 and
  1.1. Tests are failing with TLSV1_ALERT_INTERNAL_ERROR.

Build
-----

- bpo-43567: Improved generated code refresh (AST/tokens/opcodes/keywords)
  on Windows.

- bpo-43669: Implement :pep:`644`. Python now requires OpenSSL 1.1.1 or
  newer.

Windows
-------

- bpo-35306: Adds additional arguments to :func:`os.startfile` function.

- bpo-43538: Avoid raising errors from :meth:`pathlib.Path.exists()` when
  passed an invalid filename.

- bpo-38822: Fixed :func:`os.stat` failing on inaccessible directories with
  a trailing slash, rather than falling back to the parent directory's
  metadata. This implicitly affected :func:`os.path.exists` and
  :func:`os.path.isdir`.

- bpo-26227: Fixed decoding of host names in :func:`socket.gethostbyaddr`
  and :func:`socket.gethostbyname_ex`.

- bpo-40432: Updated pegen regeneration script on Windows to find and use
  Python 3.8 or higher.  Prior to this, pegen regeneration already required
  3.8 or higher, but the script may have used lower versions of Python.

- bpo-43745: Actually updates Windows release to OpenSSL 1.1.1k. Earlier
  releases were mislabelled and actually included 1.1.1i again.

- bpo-43652: Update Tcl and Tk to 8.6.11 in Windows installer.

- bpo-43492: Upgrade Windows installer to use SQLite 3.35.5.

- bpo-30555: Fix ``WindowsConsoleIO`` errors in the presence of fd
  redirection. Patch by Segev Finer.

macOS
-----

- bpo-42119: Fix check for macOS SDK paths when building Python. Narrow
  search to match contents of SDKs, namely only files in
  ``/System/Library``, ``/System/IOSSupport``, and ``/usr`` other than
  ``/usr/local``. Previously, anything under ``/System`` was assumed to be
  in an SDK which causes problems with the new file system layout in 10.15+
  where user file systems may appear to be mounted under ``/System``.  Paths
  in ``/Library`` were also incorrectly treated as SDK locations.

- bpo-43568: Drop support for MACOSX_DEPLOYMENT_TARGET < 10.3

- bpo-44009: Provide "python3.x-intel64" executable to allow reliably
  forcing macOS universal2 framework builds to run under Rosetta 2 Intel-64
  emulation on Apple Silicon Macs.  This can be useful for testing or when
  universal2 wheels are not yet available.

- bpo-43851: Build SQLite with ``SQLITE_OMIT_AUTOINIT`` on macOS. Patch by
  Erlend E. Aasland.

- bpo-43492: Update macOS installer to use SQLite 3.35.4.

- bpo-42235: ``Mac/BuildScript/build-installer.py`` will now use
  "--enable-optimizations" and ``--with-lto`` when building on macOS 10.15
  or later.

IDLE
----

- bpo-37903: Add mouse actions to the shell sidebar.  Left click and
  optional drag selects one or more lines, as with the editor line number
  sidebar.  Right click after selecting raises a context menu with 'copy
  with prompts'.  This zips together prompts from the sidebar with lines
  from the selected text.

- bpo-43981: Fix reference leak in test_sidebar and test_squeezer. Patches
  by Terry Jan Reedy and Pablo Galindo

- bpo-37892: Indent IDLE Shell input with spaces instead of tabs

- bpo-43655: IDLE dialog windows are now recognized as dialogs by window
  managers on macOS and X Window.

- bpo-37903: IDLE's shell now shows prompts in a separate side-bar.

C API
-----

- bpo-43916: Add a new :c:data:`Py_TPFLAGS_DISALLOW_INSTANTIATION` type flag
  to disallow creating type instances. Patch by Victor Stinner.

- bpo-43774: Remove the now unused ``PYMALLOC_DEBUG`` macro. Debug hooks on
  memory allocators are now installed by default if Python is built in debug
  mode (if ``Py_DEBUG`` macro is defined). Moreover, they can now be used on
  Python build in release mode (ex: using ``PYTHONMALLOC=debug`` environment
  variable).

- bpo-43962: _PyInterpreterState_IDIncref() now calls
  _PyInterpreterState_IDInitref() and always increments id_refcount.
  Previously, calling _xxsubinterpreters.get_current() could create an
  id_refcount inconsistency when a _xxsubinterpreters.InterpreterID object
  was deallocated. Patch by Victor Stinner.

- bpo-28254: Add new C-API functions to control the state of the garbage
  collector: :c:func:`PyGC_Enable()`, :c:func:`PyGC_Disable()`,
  :c:func:`PyGC_IsEnabled()`, corresponding to the functions in the
  :mod:`gc` module.

- bpo-43908: Introduce :const:`Py_TPFLAGS_IMMUTABLETYPE` flag for immutable
  type objects, and modify :c:func:`PyType_Ready` to set it for static
  types. Patch by Erlend E. Aasland.

- bpo-43795: :c:func:`PyMem_Calloc` is now available in the limited C API
  (``Py_LIMITED_API``).

- bpo-43868: :c:func:`PyOS_ReadlineFunctionPointer` is no longer exported by
  limited C API headers and by ``python3.dll`` on Windows. Like any function
  that takes ``FILE*``, it is not part of the stable ABI.

- bpo-43795: Stable ABI and limited API definitions are generated from a
  central manifest (:pep:`652`).

- bpo-43753: Add the :c:func:`Py_Is(x, y) <Py_Is>` function to test if the
  *x* object is the *y* object, the same as ``x is y`` in Python. Add also
  the :c:func:`Py_IsNone`, :c:func:`Py_IsTrue`, :c:func:`Py_IsFalse`
  functions to test if an object is, respectively, the ``None`` singleton,
  the ``True`` singleton or the ``False`` singleton. Patch by Victor
  Stinner.


What's New in Python 3.10.0 alpha 7?
====================================

*Release date: 2021-04-05*

Security
--------

- bpo-42988: CVE-2021-3426: Remove the ``getfile`` feature of the
  :mod:`pydoc` module which could be abused to read arbitrary files on the
  disk (directory traversal vulnerability). Moreover, even source code of
  Python modules can contain sensitive data like passwords. Vulnerability
  reported by David Schwörer.

- bpo-43285: :mod:`ftplib` no longer trusts the IP address value returned
  from the server in response to the PASV command by default.  This prevents
  a malicious FTP server from using the response to probe IPv4 address and
  port combinations on the client network.

  Code that requires the former vulnerable behavior may set a
  ``trust_server_pasv_ipv4_address`` attribute on their :class:`ftplib.FTP`
  instances to ``True`` to re-enable it.

- bpo-43439: Add audit hooks for :func:`gc.get_objects`,
  :func:`gc.get_referrers` and :func:`gc.get_referents`. Patch by Pablo
  Galindo.

Core and Builtins
-----------------

- bpo-27129: Update CPython bytecode magic number.

- bpo-43672: Raise ImportWarning when calling find_loader().

- bpo-43660: Fix crash that happens when replacing ``sys.stderr`` with a
  callable that can remove the object while an exception is being printed.
  Patch by Pablo Galindo.

- bpo-27129: The bytecode interpreter uses instruction, rather byte, offsets
  internally. This reduces the number of EXTENDED_ARG instructions needed
  and streamlines instruction dispatch a bit.

- bpo-40645: Fix reference leak in the :mod:`_hashopenssl` extension. Patch
  by Pablo Galindo.

- bpo-42134: Calls to find_module() by the import system now raise
  ImportWarning.

- bpo-41064: Improve the syntax error for invalid usage of double starred
  elements ('**') in f-strings. Patch by Pablo Galindo.

- bpo-43575: Speed up calls to ``map()`` by using the :pep:`590`
  ``vectorcall`` calling convention. Patch by Dong-hee Na.

- bpo-42137: The import system now prefers using ``__spec__`` for
  ``ModuleType.__repr__`` over ``module_repr()``.

- bpo-43452: Added micro-optimizations to ``_PyType_Lookup()`` to improve
  cache lookup performance in the common case of cache hits.

- bpo-43555: Report the column offset for :exc:`SyntaxError` for invalid
  line continuation characters. Patch by Pablo Galindo.

- bpo-43517: Fix misdetection of circular imports when using ``from pkg.mod
  import attr``, which caused false positives in non-trivial multi-threaded
  code.

- bpo-43497: Emit SyntaxWarnings for assertions with tuple constants, this
  is a regression introduced in python3.7

- bpo-39316: Tracing now has correct line numbers for attribute accesses
  when the the attribute is on a different line from the object. Improves
  debugging and profiling for multi-line method chains.

- bpo-35883: Python no longer fails at startup with a fatal error if a
  command line argument contains an invalid Unicode character. The
  :c:func:`Py_DecodeLocale` function now escapes byte sequences which would
  be decoded as Unicode characters outside the [U+0000; U+10ffff] range.

- bpo-43410: Fix a bug that was causing the parser to crash when emitting
  syntax errors when reading input from stdin. Patch by Pablo Galindo

- bpo-43406: Fix a possible race condition where ``PyErr_CheckSignals``
  tries to execute a non-Python signal handler.

- bpo-42128: Add ``__match_args__`` to :c:type:`structsequence` based
  classes. Patch by Pablo Galindo.

- bpo-43390: CPython now sets the ``SA_ONSTACK`` flag in ``PyOS_setsig`` for
  the VM's default signal handlers.  This is friendlier to other in-process
  code that an extension module or embedding use could pull in (such as
  Golang's cgo) where tiny thread stacks are the norm and ``sigaltstack()``
  has been used to provide for signal handlers.  This is a no-op change for
  the vast majority of processes that don't use sigaltstack.

- bpo-43287: Speed up calls to ``filter()`` by using the :pep:`590`
  ``vectorcall`` calling convention. Patch by Dong-hee Na.

- bpo-37448: Add a radix tree based memory map to track in-use obmalloc
  arenas. Use to replace the old implementation of address_in_range(). The
  radix tree approach makes it easy to increase pool sizes beyond the OS
  page size. Boosting the pool and arena size allows obmalloc to handle a
  significantly higher percentage of requests from its ultra-fast paths.

  It also has the advantage of eliminating the memory unsanitary behavior of
  the previous address_in_range(). The old address_in_range() was marked
  with the annotations _Py_NO_SANITIZE_ADDRESS, _Py_NO_SANITIZE_THREAD, and
  _Py_NO_SANITIZE_MEMORY. Those annotations are no longer needed.

  To disable the radix tree map, set a preprocessor flag as follows:
  `-DWITH_PYMALLOC_RADIX_TREE=0`.

  Co-authored-by: Tim Peters <tim.peters@gmail.com>

- bpo-29988: Only handle asynchronous exceptions and requests to drop the
  GIL when returning from a call or on the back edges of loops. Makes sure
  that :meth:`__exit__` is always called in with statements, even for
  interrupts.

Library
-------

- bpo-43720: Document various stdlib deprecations in imp, pkgutil, and
  importlib.util for removal in Python 3.12.

- bpo-43433: :class:`xmlrpc.client.ServerProxy` no longer ignores query and
  fragment in the URL of the server.

- bpo-31956: The :meth:`~array.array.index` method of :class:`array.array`
  now has optional *start* and *stop* parameters.

- bpo-40066: Enum: adjust ``repr()`` to show only enum and member name (not
  value, nor angle brackets) and ``str()`` to show only member name.  Update
  and improve documentation to match.

- bpo-42136: Deprecate all module_repr() methods found in importlib as their
  use is being phased out by Python 3.12.

- bpo-35930: Raising an exception raised in a "future" instance will create
  reference cycles.

- bpo-41369: Finish updating the vendored libmpdec to version 2.5.1.  Patch
  by Stefan Krah.

- bpo-43422: Revert the _decimal C API which was added in bpo-41324.

- bpo-43577: Fix deadlock when using :class:`ssl.SSLContext` debug callback
  with :meth:`ssl.SSLContext.sni_callback`.

- bpo-43571: It's now possible to create MPTCP sockets with IPPROTO_MPTCP

- bpo-43542: ``image/heic`` and ``image/heif`` were added to
  :mod:`mimetypes`.

- bpo-40645: The :mod:`hmac` module now uses OpenSSL's HMAC implementation
  when digestmod argument is a hash name or builtin hash function.

- bpo-43510: Implement :pep:`597`: Add ``EncodingWarning`` warning, ``-X
  warn_default_encoding`` option, :envvar:`PYTHONWARNDEFAULTENCODING`
  environment variable and ``encoding="locale"`` argument value.

- bpo-43521: ``ast.unparse`` can now render NaNs and empty sets.

- bpo-42914: :func:`pprint.pprint` gains a new boolean
  ``underscore_numbers`` optional argument to emit integers with thousands
  separated by an underscore character for improved readability (for example
  ``1_000_000`` instead of ``1000000``).

- bpo-41361: :meth:`~collections.deque.rotate` calls are now slightly faster
  due to faster argument parsing.

- bpo-43423: :func:`subprocess.communicate` no longer raises an IndexError
  when there is an empty stdout or stderr IO buffer during a timeout on
  Windows.

- bpo-27820: Fixed long-standing bug of smtplib.SMTP where doing AUTH LOGIN
  with initial_response_ok=False will fail.

  The cause is that SMTP.auth_login _always_ returns a password if provided
  with a challenge string, thus non-compliant with the standard for AUTH
  LOGIN.

  Also fixes bug with the test for smtpd.

- bpo-43445: Add frozen modules to :data:`sys.stdlib_module_names`. For
  example, add ``"_frozen_importlib"`` and ``"_frozen_importlib_external"``
  names.

- bpo-43245: Add keyword arguments support to ``ChainMap.new_child()``.

- bpo-29982: Add optional parameter *ignore_cleanup_errors* to
  :func:`tempfile.TemporaryDirectory` and allow multiple :func:`cleanup`
  attempts. Contributed by C.A.M. Gerlach.

- bpo-43428: Include changes from `importlib_metadata 3.7
  <https://importlib-metadata.readthedocs.io/en/latest/history.html#v3-7-0>`_:

  Performance enhancements to distribution discovery.

  ``entry_points`` only returns unique distributions.

  Introduces new ``EntryPoints`` object for containing a set of entry points
  with convenience methods for selecting entry points by group or name.
  ``entry_points`` now returns this object if selection parameters are
  supplied but continues to return a dict object for compatibility. Users
  are encouraged to rely on the selection interface. The dict object result
  is likely to be deprecated in the future.

  Added packages_distributions function to return a mapping of packages to
  the distributions that provide them.

- bpo-43332: Improves the networking efficiency of :mod:`http.client` when
  using a proxy via :meth:`~HTTPConnection.set_tunnel`.  Fewer small send
  calls are made during connection setup.

- bpo-43420: Improve performance of :class:`fractions.Fraction` arithmetics
  for large components.  Contributed by Sergey B. Kirpichev.

- bpo-43356: Allow passing a signal number to ``_thread.interrupt_main()``.

- bpo-43399: Fix ``ElementTree.extend`` not working on iterators when using
  the Python implementation

- bpo-43369: Improve :mod:`sqlite3` error handling: If
  ``sqlite3_column_text()`` and ``sqlite3_column_blob()`` set
  ``SQLITE_NOMEM``, :exc:`MemoryError` is now raised. Patch by Erlend E.
  Aasland.

- bpo-43368: Fix a regression introduced in PR 24562, where an empty
  bytestring was fetched as ``None`` instead of ``b''`` in :mod:`sqlite3`.
  Patch by Mariusz Felisiak.

- bpo-41282: Fixed stacklevel of ``DeprecationWarning`` emitted from
  ``import distutils``.

- bpo-42129: ``importlib.resources`` now honors namespace packages, merging
  resources from each location in the namespace as introduced in
  ``importlib_resources`` 3.2 and including incidental changes through
  5.0.3.

- bpo-43295: :meth:`datetime.datetime.strptime` now raises ``ValueError``
  instead of ``IndexError`` when matching ``'z'`` with the ``%z`` format
  specifier.

- bpo-43125: Return empty string if base64mime.body_encode receive empty
  bytes

- bpo-43084: :func:`curses.window.enclose` returns now ``True`` or ``False``
  (as was documented) instead of ``1`` or ``0``.

- bpo-42994: Add MIME types for opus, AAC, 3gpp and 3gpp2

- bpo-14678: Add an invalidate_caches() method to the zipimport.zipimporter
  class to support importlib.invalidate_caches(). Patch by Desmond Cheong.

- bpo-42782: Fail fast in :func:`shutil.move()` to avoid creating
  destination directories on failure.

- bpo-40066: Enum's `repr()` and `str()` have changed: `repr()` is now
  *EnumClass.MemberName* and `str()` is *MemberName*.  Additionally, stdlib
  Enum's whose contents are available as module attributes, such as
  `RegexFlag.IGNORECASE`, have their `repr()` as *module.name*, e.g.
  `re.IGNORECASE`.

- bpo-26053: Fixed bug where the :mod:`pdb` interactive run command echoed
  the args from the shell command line, even if those have been overridden
  at the pdb prompt.

- bpo-24160: Fixed bug where breakpoints did not persist across multiple
  debugger sessions in :mod:`pdb`'s interactive mode.

- bpo-40701: When the :data:`tempfile.tempdir` global variable is set to a
  value of type bytes, it is now handled consistently.  Previously
  exceptions could be raised from some tempfile APIs when the directory did
  not already exist in this situation.  Also ensures that the
  :func:`tempfile.gettempdir()` and :func:`tempfile.gettempdirb()` functions
  *always* return ``str`` and ``bytes`` respectively.

- bpo-39342: Expose ``X509_V_FLAG_ALLOW_PROXY_CERTS`` as
  :data:`~ssl.VERIFY_ALLOW_PROXY_CERTS` to allow proxy certificate
  validation as explained in
  https://www.openssl.org/docs/man1.1.1/man7/proxy-certificates.html.

- bpo-31861: Add builtins.aiter and builtins.anext. Patch by Joshua Bronson
  (@jab), Daniel Pope (@lordmauve), and Justin Wang (@justin39).

Documentation
-------------

- bpo-43199: Answer "Why is there no goto?" in the Design and History FAQ.

- bpo-43407: Clarified that a result from :func:`time.monotonic`,
  :func:`time.perf_counter`, :func:`time.process_time`, or
  :func:`time.thread_time` can be compared with the result from any
  following call to the same function - not just the next immediate call.

- bpo-43354: Fix type documentation for ``Fault.faultCode``; the type has to
  be ``int`` instead of ``str``.

- bpo-41933: Clarified wording of s * n in the Common Sequence Operations

Tests
-----

- bpo-37945: Fix test_getsetlocale_issue1813() of test_locale: skip the test
  if ``setlocale()`` fails. Patch by Victor Stinner.

- bpo-41561: Add workaround for Ubuntu's custom OpenSSL security level
  policy.

Build
-----

- bpo-43179: Introduce and correctly use ALIGNOF_X in place of SIZEOF_X for
  alignment-related code in optimized string routines. Patch by Jessica
  Clarke.

- bpo-43631: Update macOS, Windows, and CI to OpenSSL 1.1.1k.

- bpo-43617: Improve configure.ac: Check for presence of autoconf-archive
  package and remove our copies of M4 macros.

- bpo-43466: The ``configure`` script now supports ``--with-openssl-rpath``
  option.

- bpo-43372: Use ``_freeze_importlib`` to generate code for the
  ``__hello__`` module. This approach ensures the code matches the
  interpreter version.  Previously, PYTHON_FOR_REGEN was used to generate
  the code, which might be wrong.  The marshal format for code objects has
  changed with bpo-42246, commit 877df851. Update the code and the expected
  code sizes in ctypes test_frozentable.

Windows
-------

- bpo-43440: Build :mod:`sqlite3` with the ``R*Tree`` module enabled. Patch
  by Erlend E. Aasland.

IDLE
----

- bpo-42225: Document that IDLE can fail on Unix either from misconfigured
  IP masquerade rules or failure displaying complex colored (non-ascii)
  characters.

C API
-----

- bpo-43688: The limited C API is now supported if Python is built in debug
  mode (if the ``Py_DEBUG`` macro is defined). In the limited C API, the
  :c:func:`Py_INCREF` and :c:func:`Py_DECREF` functions are now implemented
  as opaque function calls, rather than accessing directly the
  :c:member:`PyObject.ob_refcnt` member, if Python is built in debug mode
  and the ``Py_LIMITED_API`` macro targets Python 3.10 or newer. It became
  possible to support the limited C API in debug mode because the
  :c:type:`PyObject` structure is the same in release and debug mode since
  Python 3.8 (see :issue:`36465`).

  The limited C API is still not supported in the ``--with-trace-refs``
  special build (``Py_TRACE_REFS`` macro).

  Patch by Victor Stinner.

- bpo-43244: Remove the ``pyarena.h`` header file with functions:

  * ``PyArena_New()``
  * ``PyArena_Free()``
  * ``PyArena_Malloc()``
  * ``PyArena_AddPyObject()``

  These functions were undocumented, excluded from the limited C API, and
  were only used internally by the compiler. Patch by Victor Stinner.

- bpo-43244: Remove the compiler and parser functions using ``struct _mod``
  type, because the public AST C API was removed:

  * ``PyAST_Compile()``
  * ``PyAST_CompileEx()``
  * ``PyAST_CompileObject()``
  * ``PyFuture_FromAST()``
  * ``PyFuture_FromASTObject()``
  * ``PyParser_ASTFromFile()``
  * ``PyParser_ASTFromFileObject()``
  * ``PyParser_ASTFromFilename()``
  * ``PyParser_ASTFromString()``
  * ``PyParser_ASTFromStringObject()``

  These functions were undocumented and excluded from the limited C API.
  Patch by Victor Stinner.

- bpo-43244: Remove ``ast.h``, ``asdl.h``, and ``Python-ast.h`` header
  files. These functions were undocumented and excluded from the limited C
  API. Most names defined by these header files were not prefixed by ``Py``
  and so could create names conflicts. For example, ``Python-ast.h`` defined
  a ``Yield`` macro which was conflict with the ``Yield`` name used by the
  Windows ``<winbase.h>`` header. Use the Python :mod:`ast` module instead.
  Patch by Victor Stinner.

- bpo-43541: Fix a ``PyEval_EvalCodeEx()`` regression: fix reference
  counting on builtins. Patch by Victor Stinner.

- bpo-43244: Remove the ``symtable.h`` header file and the undocumented
  functions:

  * ``PyST_GetScope()``
  * ``PySymtable_Build()``
  * ``PySymtable_BuildObject()``
  * ``PySymtable_Free()``
  * ``Py_SymtableString()``
  * ``Py_SymtableStringObject()``

  The ``Py_SymtableString()`` function was part the stable ABI by mistake
  but it could not be used, because the ``symtable.h`` header file was
  excluded from the limited C API.

  The Python :mod:`symtable` module remains available and is unchanged.

  Patch by Victor Stinner.

- bpo-43244: Remove the ``PyAST_Validate()`` function. It is no longer
  possible to build a AST object (``mod_ty`` type) with the public C API.
  The function was already excluded from the limited C API (:pep:`384`).
  Patch by Victor Stinner.


What's New in Python 3.10.0 alpha 6?
====================================

*Release date: 2021-03-01*

Security
--------

- bpo-42967: Fix web cache poisoning vulnerability by defaulting the query
  args separator to ``&``, and allowing the user to choose a custom
  separator.

Core and Builtins
-----------------

- bpo-43321: Fix ``SystemError`` raised when ``PyArg_Parse*()`` is used with
  ``#`` but without ``PY_SSIZE_T_CLEAN`` defined.

- bpo-36346: ``PyArg_Parse*()`` functions now emits ``DeprecationWarning``
  when ``u`` or ``Z`` format is used. See :pep:`623` for detail.

- bpo-43277: Add a new :c:func:`PySet_CheckExact` function to the C-API to
  check if an object is an instance of :class:`set` but not an instance of a
  subtype. Patch by Pablo Galindo.

- bpo-42990: The :data:`types.FunctionType` constructor now inherits the
  current builtins if the *globals* dictionary has no ``"__builtins__"``
  key, rather than using ``{"None": None}`` as builtins: same behavior as
  :func:`eval` and :func:`exec` functions. Defining a function with ``def
  function(...): ...`` in Python is not affected, globals cannot be
  overridden with this syntax: it also inherits the current builtins. Patch
  by Victor Stinner.

- bpo-42990: Functions have a new ``__builtins__`` attribute which is used
  to look for builtin symbols when a function is executed, instead of
  looking into ``__globals__['__builtins__']``. Patch by Mark Shannon and
  Victor Stinner.

- bpo-43149: Improve the error message in the parser for exception groups
  without parentheses. Patch by Pablo Galindo.

- bpo-43121: Fixed an incorrect :exc:`SyntaxError` message for missing comma
  in literals. Patch by Pablo Galindo.

- bpo-42819: :mod:`readline`: Explicitly disable bracketed paste in the
  interactive interpreter, even if it's set in the inputrc, is enabled by
  default (eg GNU Readline 8.1), or a user calls
  ``readline.read_init_file()``. The Python REPL has not implemented
  bracketed paste support. Also, bracketed mode writes the ``"\x1b[?2004h"``
  escape sequence into stdout which causes test failures in applications
  that don't support it. It can still be explicitly enabled by calling
  ``readline.parse_and_bind("set enable-bracketed-paste on")``. Patch by
  Dustin Rodrigues.

- bpo-42808: Simple calls to ``type(object)`` are now faster due to the
  ``vectorcall`` calling convention. Patch by Dennis Sweeney.

- bpo-42217: Make the compiler merges same co_code and co_linetable objects
  in a module like already did for co_consts.

- bpo-41972: Substring search functions such as ``str1 in str2`` and
  ``str2.find(str1)`` now sometimes use the "Two-Way" string comparison
  algorithm to avoid quadratic behavior on long strings.

- bpo-42128: Implement :pep:`634` (structural pattern matching). Patch by
  Brandt Bucher.

- bpo-40692: In the :class:`concurrent.futures.ProcessPoolExecutor`,
  validate that :func:`multiprocess.synchronize` is available on a given
  platform and rely on that check in the :mod:`concurrent.futures` test
  suite so we can run tests that are unrelated to
  :class:`ProcessPoolExecutor` on those platforms.

- bpo-38302: If :func:`object.__ipow__` returns :const:`NotImplemented`, the
  operator will correctly fall back to :func:`object.__pow__` and
  :func:`object.__rpow__` as expected.

Library
-------

- bpo-43316: The ``python -m gzip`` command line application now properly
  fails when detecting an unsupported extension. It exits with a non-zero
  exit code and prints an error message to stderr.

- bpo-43317: Set the chunk size for the ``gzip`` module main function to
  io.DEFAULT_BUFFER_SIZE. This is slightly faster than the 1024 bytes
  constant that was used previously.

- bpo-43146: Handle None in single-arg versions of
  :func:`~traceback.print_exception` and
  :func:`~traceback.format_exception`.

- bpo-43260: Fix TextIOWrapper can not flush internal buffer forever after
  very large text is written.

- bpo-43258: Prevent needless allocation of :mod:`sqlite3` aggregate
  function context when no rows match an aggregate query. Patch by Erlend E.
  Aasland.

- bpo-43251: Improve :mod:`sqlite3` error handling:
  ``sqlite3_column_name()`` failures now result in :exc:`MemoryError`. Patch
  by Erlend E. Aasland.

- bpo-40956: Fix segfault in :meth:`sqlite3.Connection.backup` if no
  argument was provided. The regression was introduced by PR 23838. Patch by
  Erlend E. Aasland.

- bpo-43172: The readline module now passes its tests when built directly
  against libedit. Existing irreconcilable API differences remain in
  :func:`readline.get_begidx` and :func:`readline.get_endidx` behavior based
  on libreadline vs libedit use.

- bpo-43163: Fix a bug in :mod:`codeop` that was causing it to not ask for
  more input when multi-line snippets have unclosed parentheses. Patch by
  Pablo Galindo

- bpo-43162: deprecate unsupported ability to access enum members as
  attributes of other enum members

- bpo-43146: Fix recent regression in None argument handling in
  :mod:`~traceback` module functions.

- bpo-43102: The namedtuple __new__ method had its __builtins__ set to None
  instead of an actual dictionary.  This created problems for introspection
  tools.

- bpo-43106: Added :data:`~os.O_EVTONLY`, :data:`~os.O_FSYNC`,
  :data:`~os.O_SYMLINK` and :data:`~os.O_NOFOLLOW_ANY` for macOS. Patch by
  Dong-hee Na.

- bpo-42960: Adds :data:`resource.RLIMIT_KQUEUES` constant from FreeBSD to
  the :mod:`resource` module.

- bpo-42151: Make the pure Python implementation of
  :mod:`xml.etree.ElementTree` behave the same as the C implementation
  (:mod:`_elementree`) regarding default attribute values (by not setting
  ``specified_attributes=1``).

- bpo-29753: In ctypes, now packed bitfields are calculated properly and the
  first item of packed bitfields is now shrank correctly.

Documentation
-------------

- bpo-27646: Clarify that 'yield from <expr>' works with any iterable, not
  just iterators.

- bpo-36346: Update some deprecated unicode APIs which are documented as
  "will be removed in 4.0" to "3.12". See :pep:`623` for detail.

Tests
-----

- bpo-43288: Fix test_importlib to correctly skip Unicode file tests if the
  filesystem does not support them.

Build
-----

- bpo-43174: Windows build now uses ``/utf-8`` compiler option.

- bpo-43103: Add a new configure ``--without-static-libpython`` option to
  not build the ``libpythonMAJOR.MINOR.a`` static library and not install
  the ``python.o`` object file.

- bpo-13501: The configure script can now use *libedit* instead of
  *readline* with the command line option ``--with-readline=editline``.

- bpo-42603: Make configure script use pkg-config to detect the location of
  Tcl/Tk headers and libraries, used to build tkinter.

  On macOS, a Tcl/Tk configuration provided by pkg-config will be preferred
  over Tcl/Tk frameworks installed in ``/{System/,}Library/Frameworks``. If
  both exist and the latter is preferred, the appropriate ``--with-tcltk-*``
  configuration options need to be explicitly set.

- bpo-39448: Add the "regen-frozen" makefile target that regenerates the
  code for the frozen ``__hello__`` module.

Windows
-------

- bpo-43155: :c:func:`PyCMethod_New` is now present in ``python3.lib``.

macOS
-----

- bpo-41837: Update macOS installer build to use OpenSSL 1.1.1j.

IDLE
----

- bpo-43283: Document why printing to IDLE's Shell is often slower than
  printing to a system terminal and that it can be made faster by
  pre-formatting a single string before printing.

C API
-----

- bpo-43278: Always put compiler and system information on the first line of
  the REPL welcome message.

- bpo-43270: Remove the private ``_PyErr_OCCURRED()`` macro: use the public
  :c:func:`PyErr_Occurred` function instead.

- bpo-35134: Move odictobject.h, parser_interface.h, picklebufobject.h,
  pydebug.h, and pyfpe.h into the cpython/ directory. They must not be
  included directly, as they are already included by Python.h: :ref:`Include
  Files <api-includes>`.

- bpo-35134: Move pyarena.h, pyctype.h, and pytime.h into the cpython/
  directory. They must not be included directly, as they are already
  included by Python.h: :ref:`Include Files <api-includes>`.

- bpo-40170: :c:func:`PyExceptionClass_Name` is now always declared as a
  function, in order to hide implementation details. The macro accessed
  :c:member:`PyTypeObject.tp_name` directly.  Patch by Erlend E. Aasland.

- bpo-43239: The :c:func:`PyCFunction_New` function is now exported in the
  ABI when compiled with ``-fvisibility=hidden``.

- bpo-40170: :c:func:`PyIter_Check` is now always declared as a function, in
  order to hide implementation details. The macro accessed
  :c:member:`PyTypeObject.tp_iternext` directly. Patch by Erlend E. Aasland.

- bpo-40170: Convert :c:func:`PyDescr_IsData` macro to a function to hide
  implementation details: The macro accessed
  :c:member:`PyTypeObject.tp_descr_set` directly. Patch by Erlend E.
  Aasland.

- bpo-43181: Convert :c:func:`PyObject_TypeCheck` macro to a static inline
  function. Patch by Erlend E. Aasland.


What's New in Python 3.10.0 alpha 5?
====================================

*Release date: 2021-02-02*

Security
--------

- bpo-42938: Avoid static buffers when computing the repr of
  :class:`ctypes.c_double` and :class:`ctypes.c_longdouble` values.

Core and Builtins
-----------------

- bpo-42990: Refactor the ``PyEval_`` family of functions.

  * An new function ``_PyEval_Vector`` is added to simplify calls to Python from C.
  * ``_PyEval_EvalCodeWithName`` is removed
  * ``PyEval_EvalCodeEx`` is retained as part of the API, but is not used internally

- bpo-38631: Replace :c:func:`Py_FatalError` calls in the compiler with
  regular :exc:`SystemError` exceptions. Patch by Victor Stinner.

- bpo-42997: Improve error message for missing ":" before blocks. Patch by
  Pablo Galindo.

- bpo-43017: Improve error message in the parser when using un-parenthesised
  tuples in comprehensions. Patch by Pablo Galindo.

- bpo-42986: Fix parser crash when reporting syntax errors in f-string with
  newlines. Patch by Pablo Galindo.

- bpo-40176: Syntax errors for unterminated string literals now point to the
  start of the string instead of reporting EOF/EOL.

- bpo-42927: The inline cache for ``LOAD_ATTR`` now also optimizes access to
  attributes defined by ``__slots__``. This makes reading such attribute up
  to 30% faster.

- bpo-42864: Improve error messages in the parser when parentheses are not
  closed. Patch by Pablo Galindo.

- bpo-42924: Fix ``bytearray`` repetition incorrectly copying data from the
  start of the buffer, even if the data is offset within the buffer (e.g.
  after reassigning a slice at the start of the ``bytearray`` to a shorter
  byte string).

- bpo-42882: Fix the :c:func:`_PyUnicode_FromId` function
  (_Py_IDENTIFIER(var) API) when :c:func:`Py_Initialize` /
  :c:func:`Py_Finalize` is called multiple times: preserve
  ``_PyRuntime.unicode_ids.next_index`` value.

- bpo-42827: Fix a crash when working out the error line of a
  :exc:`SyntaxError` in some multi-line expressions.

- bpo-42823: frame.f_lineno is correct even if frame.f_trace is set to True

- bpo-37324: Remove deprecated aliases to
  :ref:`collections-abstract-base-classes` from the :mod:`collections`
  module.

- bpo-41994: Fixed possible leak in ``import`` when ``sys.modules`` is not a
  ``dict``.

- bpo-27772: In string formatting, preceding the *width* field by ``'0'`` no
  longer affects the default alignment for strings.

Library
-------

- bpo-43108: Fixed a reference leak in the :mod:`curses` module. Patch by
  Pablo Galindo

- bpo-43077: Update the bundled pip to 21.0.1 and setuptools to 52.0.0.

- bpo-41282: Deprecate ``distutils`` in documentation and add warning on
  import.

- bpo-43014: Improve performance of :mod:`tokenize` by 20-30%.  Patch by
  Anthony Sottile.

- bpo-42323: Fix :func:`math.nextafter` for NaN on AIX.

- bpo-42955: Add :data:`sys.stdlib_module_names`, containing the list of the
  standard library module names. Patch by Victor Stinner.

- bpo-42944: Fix ``random.Random.sample`` when ``counts`` argument is not
  ``None``.

- bpo-42934: Use :class:`~traceback.TracebackException`'s new ``compact``
  param in :class:`~unittest.TestResult` to reduce time and memory consumed
  by traceback formatting.

- bpo-42931: Add :func:`randbytes` to ``random.__all__``.

- bpo-38250: [Enum] Flags consisting of a single bit are now considered
  canonical, and will be the only flags returned from listing and iterating
  over a Flag class or a Flag member.  Multi-bit flags are considered
  aliases; they will be returned from lookups and operations that result in
  their value. Iteration for both Flag and Flag members is in definition
  order.

- bpo-42877: Added the ``compact`` parameter to the constructor of
  :class:`traceback.TracebackException` to reduce time and memory for use
  cases that only need to call :func:`TracebackException.format` and
  :func:`TracebackException.format_exception_only`.

- bpo-42923: The :c:func:`Py_FatalError` function and the
  :mod:`faulthandler` module now dump the list of extension modules on a
  fatal error.

- bpo-42848: Removed recursion from :class:`~traceback.TracebackException`
  to allow it to handle long exception chains.

- bpo-42901: [Enum] move member creation from ``EnumMeta.__new__`` to
  ``_proto_member.__set_name__``, allowing members to be created and visible
  in ``__init_subclass__``.

- bpo-42780: Fix os.set_inheritable() for O_PATH file descriptors on Linux.

- bpo-42866: Fix a reference leak in the ``getcodec()`` function of CJK
  codecs. Patch by Victor Stinner.

- bpo-42846: Convert the 6 CJK codec extension modules (_codecs_cn,
  _codecs_hk, _codecs_iso2022, _codecs_jp, _codecs_kr and _codecs_tw) to the
  multiphase initialization API (:pep:`489`). Patch by Victor Stinner.

- bpo-42851: remove __init_subclass__ support for Enum members

- bpo-42834: Make internal caches of the ``_json`` module compatible with
  subinterpreters.

- bpo-41748: Fix HTMLParser parsing rules for element attributes containing
  commas with spaces. Patch by Karl Dubost.

- bpo-40810: Require SQLite 3.7.15 or newer. Patch by Erlend E. Aasland.

- bpo-1635741: Convert the _multibytecodec extension module (CJK codecs) to
  multi-phase initialization (:pep:`489`).  Patch by Erlend E. Aasland.

- bpo-42802: The distutils ``bdist_wininst`` command deprecated in Python
  3.8 has been removed. The distutils ``bdist_wheel`` command is now
  recommended to distribute binary packages on Windows.

- bpo-24464: The undocumented built-in function
  ``sqlite3.enable_shared_cache`` is now deprecated, scheduled for removal
  in Python 3.12.  Its use is strongly discouraged by the SQLite3
  documentation.  Patch by Erlend E. Aasland.

- bpo-42384: Make pdb populate sys.path[0] exactly the same as regular
  python execution.

- bpo-42383: Fix pdb: previously pdb would fail to restart the debugging
  target if it was specified using a relative path and the current directory
  changed.

- bpo-42005: Fix CLI of :mod:`cProfile` and :mod:`profile` to catch
  :exc:`BrokenPipeError`.

- bpo-41604: Don't decrement the reference count of the previous user_ptr
  when set_panel_userptr fails.

- bpo-41149: Allow executing callables that have a boolean value of
  ``False`` when passed to :class:`Threading.thread` as the target. Patch
  contributed by Barney Stratford.

- bpo-38307: Add an 'end_lineno' attribute to the Class and Function objects
  that appear in the tree returned by pyclbr functions.  This and the
  existing 'lineno' attribute define the extent of class and def statements.
  Patch by Aviral Srivastava.

- bpo-39273: The ``BUTTON5_*`` constants are now exposed in the
  :mod:`curses` module if available.

- bpo-33289: Correct call to :mod:`tkinter.colorchooser` to return RGB
  triplet of ints instead of floats.  Patch by Cheryl Sabella.

Documentation
-------------

- bpo-40304: Fix doc for type(name, bases, dict).  Patch by Boris
  Verkhovskiy and Éric Araujo.

- bpo-42811: Updated importlib.utils.resolve_name() doc to use
  __spec__.parent instead of __package__. (Thanks Yair Frid.)

Tests
-----

- bpo-40823: Use :meth:`unittest.TestLoader().loadTestsFromTestCase` instead
  of :meth:`unittest.makeSuite` in :mod:`sqlite3` tests. Patch by Erlend E.
  Aasland.

- bpo-40810: In :mod:`sqlite3`, fix ``CheckTraceCallbackContent`` for SQLite
  pre 3.7.15.

Build
-----

- bpo-43031: Pass ``--timeout=$(TESTTIMEOUT)`` option to the default profile
  task ``./python -m test --pgo`` command.

- bpo-36143: ``make regen-all`` now also runs ``regen-keyword``. Patch by
  Victor Stinner.

- bpo-42874: Removed the grep -q and -E flags in the tzpath validation
  section of the configure script to better accommodate users of some
  platforms (specifically Solaris 10).

- bpo-31904: Add library search path by wr-cc in add_cross_compiling_paths()
  for VxWorks.

- bpo-42856: Add ``--with-wheel-pkg-dir=PATH`` option to the ``./configure``
  script. If specified, the :mod:`ensurepip` module looks for ``setuptools``
  and ``pip`` wheel packages in this directory: if both are present, these
  wheel packages are used instead of ensurepip bundled wheel packages.

  Some Linux distribution packaging policies recommend against bundling
  dependencies. For example, Fedora installs wheel packages in the
  ``/usr/share/python-wheels/`` directory and don't install the
  ``ensurepip._bundled`` package.

Windows
-------

- bpo-41837: Updated Windows installer to include OpenSSL 1.1.1i

- bpo-42584: Upgrade Windows installer to use SQLite 3.34.0.

macOS
-----

- bpo-42504: Ensure that the value of
  sysconfig.get_config_var('MACOSX_DEPLOYMENT_TARGET') is always a string,
  even in when the value is parsable as an integer.

IDLE
----

- bpo-43008: Make IDLE invoke :func:`sys.excepthook` in normal, 2-process
  mode. Patch by Ken Hilton.

- bpo-33065: Fix problem debugging user classes with __repr__ method.

- bpo-23544: Disable Debug=>Stack Viewer when user code is running or
  Debugger is active, to prevent hang or crash.  Patch by Zackery Spytz.

- bpo-32631: Finish zzdummy example extension module: make menu entries
  work; add docstrings and tests with 100% coverage.

C API
-----

- bpo-42979: When Python is built in debug mode (with C assertions), calling
  a type slot like ``sq_length`` (``__len__()`` in Python) now fails with a
  fatal error if the slot succeeded with an exception set, or failed with no
  exception set. The error message contains the slot, the type name, and the
  current exception (if an exception is set). Patch by Victor Stinner.

- bpo-43030: Fixed a compiler warning in :c:func:`Py_UNICODE_ISSPACE()` on
  platforms with signed ``wchar_t``.


What's New in Python 3.10.0 alpha 4?
====================================

*Release date: 2021-01-04*

Core and Builtins
-----------------

- bpo-42814: Fix undefined behavior in ``Objects/genericaliasobject.c``.

- bpo-42806: Fix the column offsets for f-strings :mod:`ast` nodes
  surrounded by parentheses and for nodes that spawn multiple lines. Patch
  by Pablo Galindo.

- bpo-40631: Fix regression where a single parenthesized starred expression
  was a valid assignment target.

- bpo-27794: Improve the error message for failed writes/deletes to property
  objects. When possible, the attribute name is now shown. Patch provided by
  Yurii Karabas.

- bpo-42745: Make the type attribute lookup cache per-interpreter. Patch by
  Victor Stinner.

- bpo-42246: Jumps to jumps are not eliminated when it would break PEP 626.

- bpo-42246: Make sure that the ``f_lasti`` and ``f_lineno`` attributes of a
  frame are set correctly when an exception is raised or re-raised. Required
  for PEP 626.

- bpo-32381: The coding cookie (ex: ``# coding: latin1``) is now ignored in
  the command passed to the :option:`-c` command line option. Patch by
  Victor Stinner.

- bpo-30858: Improve error location in expressions that contain assignments.
  Patch by Pablo Galindo and Lysandros Nikolaou.

- bpo-42615: Remove jump commands made redundant by the deletion of
  unreachable bytecode blocks

- bpo-42639: Make the :mod:`atexit` module state per-interpreter. It is now
  safe have more than one :mod:`atexit` module instance. Patch by Dong-hee
  Na and Victor Stinner.

- bpo-32381: Fix encoding name when running a ``.pyc`` file on Windows:
  :c:func:`PyRun_SimpleFileExFlags()` now uses the correct encoding to
  decode the filename.

- bpo-42195: The ``__args__`` of the parameterized generics for
  :data:`typing.Callable` and :class:`collections.abc.Callable` are now
  consistent.  The ``__args__`` for :class:`collections.abc.Callable` are
  now flattened while :data:`typing.Callable`'s have not changed.  To allow
  this change, :class:`types.GenericAlias` can now be subclassed and
  ``collections.abc.Callable``'s ``__class_getitem__`` will now return a
  subclass of ``types.GenericAlias``.  Tests for typing were also updated to
  not subclass things like ``Callable[..., T]`` as that is not a valid base
  class.  Finally, both ``Callable``\ s no longer validate their
  ``argtypes``, in ``Callable[[argtypes], resulttype]`` to prepare for
  :pep:`612`.  Patch by Ken Jin.

- bpo-40137: Convert functools module to use
  :c:func:`PyType_FromModuleAndSpec`.

- bpo-40077: Convert :mod:`array` to use heap types, and establish module
  state for these.

- bpo-42008: Fix _random.Random() seeding.

- bpo-1635741: Port the :mod:`pyexpat` extension module to multi-phase
  initialization (:pep:`489`).

- bpo-40521: Make the Unicode dictionary of interned strings compatible with
  subinterpreters. Patch by Victor Stinner.

- bpo-39465: Make :c:func:`_PyUnicode_FromId` function compatible with
  subinterpreters. Each interpreter now has an array of identifier objects
  (interned strings decoded from UTF-8). Patch by Victor Stinner.

Library
-------

- bpo-42257: Handle empty string in variable executable in
  platform.libc_ver()

- bpo-42772: randrange() now raises a TypeError when step is specified
  without a stop argument.  Formerly, it silently ignored the step argument.

- bpo-42759: Fixed equality comparison of :class:`tkinter.Variable` and
  :class:`tkinter.font.Font`. Objects which belong to different Tcl
  interpreters are now always different, even if they have the same name.

- bpo-42756: Configure LMTP Unix-domain socket to use socket global default
  timeout when a timeout is not explicitly provided.

- bpo-23328: Allow / character in username, password fields on _PROXY
  envars.

- bpo-42740: :func:`typing.get_args` and :func:`typing.get_origin` now
  support :pep:`604` union types and :pep:`612` additions to ``Callable``.

- bpo-42655: :mod:`subprocess` *extra_groups* is now correctly passed into
  setgroups() system call.

- bpo-42727: ``EnumMeta.__prepare__`` now accepts ``**kwds`` to properly
  support ``__init_subclass__``

- bpo-38308: Add optional *weights* to *statistics.harmonic_mean()*.

- bpo-42721: When simple query dialogs (:mod:`tkinter.simpledialog`),
  message boxes (:mod:`tkinter.messagebox`) or color choose dialog
  (:mod:`tkinter.colorchooser`) are created without arguments *master* and
  *parent*, and the default root window is not yet created, and
  :func:`~tkinter.NoDefaultRoot` was not called, a new temporal hidden root
  window will be created automatically. It will not be set as the default
  root window and will be destroyed right after closing the dialog window.
  It will help to use these simple dialog windows in programs which do not
  need other GUI.

- bpo-25246: Optimized :meth:`collections.deque.remove`.

- bpo-35728: Added a root parameter to :func:`tkinter.font.nametofont`.

- bpo-15303: :mod:`tkinter` supports now widgets with boolean value False.

- bpo-42681: Fixed range checks for color and pair numbers in :mod:`curses`.

- bpo-42685: Improved placing of simple query windows in Tkinter (such as
  :func:`tkinter.simpledialog.askinteger`). They are now centered at the
  center of the parent window if it is specified and shown, otherwise at the
  center of the screen.

- bpo-9694: Argparse help no longer uses the confusing phrase, "optional
  arguments". It uses "options" instead.

- bpo-1635741: Port the :mod:`_thread` extension module to the multiphase
  initialization API (:pep:`489`) and convert its static types to heap
  types.

- bpo-37961: Fix crash in :func:`tracemalloc.Traceback.__repr__` (regressed
  in Python 3.9).

- bpo-42630: :mod:`tkinter` functions and constructors which need a default
  root window raise now :exc:`RuntimeError` with descriptive message instead
  of obscure :exc:`AttributeError` or :exc:`NameError` if it is not created
  yet or cannot be created automatically.

- bpo-42639: :func:`atexit._run_exitfuncs` now logs callback exceptions
  using :data:`sys.unraisablehook`, rather than logging them directly into
  :data:`sys.stderr` and raise the last exception.

- bpo-42644: ``logging.disable`` will now validate the types and value of
  its parameter. It also now accepts strings representing the levels (as
  does ``loging.setLevel``) instead of only the numerical values.

- bpo-42639: At Python exit, if a callback registered with
  :func:`atexit.register` fails, its exception is now logged. Previously,
  only some exceptions were logged, and the last exception was always
  silently ignored.

- bpo-36541: Fixed lib2to3.pgen2 to be able to parse PEP-570 positional only
  argument syntax.

- bpo-42382: In ``importlib.metadata``: -  ``EntryPoint`` objects now expose
  a ``.dist`` object referencing the ``Distribution`` when constructed from
  a ``Distribution``. - Add support for package discovery under package
  normalization rules. - The object returned by ``metadata()`` now has a
  formally-defined protocol called ``PackageMetadata`` with declared support
  for the ``.get_all()`` method. - Synced with importlib_metadata 3.3.

- bpo-41877: A check is added against misspellings of autospect, auto_spec
  and set_spec being passed as arguments to patch, patch.object and
  create_autospec.

- bpo-39717: [tarfile] update nested exception raising to use ``from None``
  or ``from e``

- bpo-41877: AttributeError for suspected misspellings of assertions on
  mocks are now pointing out that the cause are misspelled assertions and
  also what to do if the misspelling is actually an intended attribute name.
  The unittest.mock document is also updated to reflect the current set of
  recognised misspellings.

- bpo-41559: Implemented :pep:`612`: added ``ParamSpec`` and ``Concatenate``
  to :mod:`typing`.  Patch by Ken Jin.

- bpo-42385: StrEnum: fix _generate_next_value_ to return a str

- bpo-31904: Define THREAD_STACK_SIZE for VxWorks.

- bpo-34750: [Enum] `_EnumDict.update()` is now supported

- bpo-42517: Enum: private names do not become members / do not generate
  errors -- they remain normal attributes

- bpo-42678: ``Enum``: call ``__init_subclass__`` after members have been
  added

- bpo-28964: :func:`ast.literal_eval` adds line number information (if
  available) in error message for malformed nodes.

- bpo-42470: :func:`random.sample` no longer warns on a sequence which is
  also a set.

- bpo-31904: :func:`posixpath.expanduser` returns the input *path* unchanged
  if user home directory is None on VxWorks.

- bpo-42388: Fix subprocess.check_output(..., input=None) behavior when
  text=True to be consistent with that of the documentation and
  universal_newlines=True.

- bpo-34463: Fixed discrepancy between :mod:`traceback` and the interpreter
  in formatting of SyntaxError with lineno not set (:mod:`traceback` was
  changed to match interpreter).

- bpo-42393: Raise :exc:`OverflowError` instead of silent truncation in
  :meth:`socket.ntohs` and :meth:`socket.htons`.  Silent truncation was
  deprecated in Python 3.7. Patch by Erlend E. Aasland

- bpo-42222: Harmonized :func:`random.randrange` argument handling to match
  :func:`range`.

  * The integer test and conversion in ``randrange()`` now uses
    :func:`operator.index`.
  * Non-integer arguments to ``randrange()`` are deprecated.
  * The ``ValueError`` is deprecated in favor of a ``TypeError``.
  * It now runs a little faster than before.

  (Contributed by Raymond Hettinger and Serhiy Storchaka.)

- bpo-42163: Restore compatibility for ``uname_result`` around deepcopy and
  _replace.

- bpo-42090: ``zipfile.Path.joinpath`` now accepts arbitrary arguments, same
  as ``pathlib.Path.joinpath``.

- bpo-1635741: Port the _csv module to the multi-phase initialization API
  (:pep:`489`).

- bpo-42059: :class:`typing.TypedDict` types created using the alternative
  call-style syntax now correctly respect the ``total`` keyword argument
  when setting their ``__required_keys__`` and ``__optional_keys__`` class
  attributes.

- bpo-41960: Add ``globalns`` and ``localns`` parameters to the
  :func:`inspect.signature` and :meth:`inspect.Signature.from_callable`.

- bpo-41907: fix ``format()`` behavior for ``IntFlag``

- bpo-41891: Ensure asyncio.wait_for waits for task completion

- bpo-24792: Fixed bug where :mod:`zipimporter` sometimes reports an
  incorrect cause of import errors.

- bpo-31904: Fix site and sysconfig modules for VxWorks RTOS which has no
  home directories.

- bpo-41462: Add :func:`os.set_blocking()` support for VxWorks RTOS.

- bpo-40219: Lowered :class:`tkinter.ttk.LabeledScale` dummy widget to
  prevent hiding part of the content label.

- bpo-37193: Fixed memory leak in ``socketserver.ThreadingMixIn`` introduced
  in Python 3.7.

- bpo-39068: Fix initialization race condition in :func:`a85encode` and
  :func:`b85encode` in :mod:`base64`. Patch by Brandon Stansbury.

Documentation
-------------

- bpo-17140: Add documentation for the
  :class:`multiprocessing.pool.ThreadPool` class.

- bpo-34398: Prominently feature listings from the glossary in documentation
  search results. Patch by Ammar Askar.

Tests
-----

- bpo-42794: Update test_nntplib to use official group name of news.aioe.org
  for testing. Patch by Dong-hee Na.

- bpo-31904: Skip some asyncio tests on VxWorks.

- bpo-42641: Enhance ``test_select.test_select()``: it now takes 500 ms
  rather than 10 seconds. Use Python rather than a shell to make the test
  more portable.

- bpo-31904: Skip some tests in _test_all_chown_common() on VxWorks.

- bpo-42199: Fix bytecode helper assertNotInBytecode.

- bpo-41443: Add more attribute checking in test_posix.py

- bpo-31904: Disable os.popen and impacted tests on VxWorks

- bpo-41439: Port test_ssl and test_uuid to VxWorks RTOS.

Build
-----

- bpo-42692: Fix __builtin_available check on older compilers. Patch by
  Joshua Root.

- bpo-27640: Added ``--disable-test-modules`` option to the ``configure``
  script: don't build nor install test modules. Patch by Xavier de Gaye,
  Thomas Petazzoni and Peixing Xin.

- bpo-42604: Now all platforms use a value for the "EXT_SUFFIX" build
  variable derived from SOABI (for instance in freeBSD, "EXT_SUFFIX" is now
  ".cpython-310d.so" instead of ".so"). Previously only Linux, Mac and
  VxWorks were using a value for "EXT_SUFFIX" that included "SOABI".

- bpo-42598: Fix implicit function declarations in configure which could
  have resulted in incorrect configuration checks.  Patch contributed by
  Joshua Root.

- bpo-31904: Enable libpython3.so for VxWorks.

- bpo-29076: Add fish shell support to macOS installer.

macOS
-----

- bpo-42361: Update macOS installer build to use Tcl/Tk 8.6.11 (rc2,
  expected to be final release).

- bpo-41837: Update macOS installer build to use OpenSSL 1.1.1i.

- bpo-42584: Update macOS installer to use SQLite 3.34.0.

Tools/Demos
-----------

- bpo-42726: Fixed Python 3 compatibility issue with gdb/libpython.py
  handling of attribute dictionaries.

- bpo-42613: Fix ``freeze.py`` tool to use the prope config and library
  directories. Patch by Victor Stinner.

C API
-----

- bpo-42591: Export the :c:func:`Py_FrozenMain` function: fix a Python 3.9.0
  regression. Python 3.9 uses ``-fvisibility=hidden`` and the function was
  not exported explicitly and so not exported.

- bpo-32381: Remove the private :c:func:`_Py_fopen` function which is no
  longer needed. Use :c:func:`_Py_wfopen` or :c:func:`_Py_fopen_obj`
  instead. Patch by Victor Stinner.

- bpo-1635741: Port :mod:`resource` extension module to module state

- bpo-42111: Update the ``xxlimited`` module to be a better example of how
  to use the limited C API.

- bpo-40052: Fix an alignment build warning/error in function
  ``PyVectorcall_Function()``. Patch by Andreas Schneider, Antoine Pitrou
  and Petr Viktorin.


What's New in Python 3.10.0 alpha 3?
====================================

*Release date: 2020-12-07*

Security
--------

- bpo-40791: Add ``volatile`` to the accumulator variable in
  ``hmac.compare_digest``, making constant-time-defeating optimizations less
  likely.

Core and Builtins
-----------------

- bpo-42576: ``types.GenericAlias`` will now raise a ``TypeError`` when
  attempting to initialize with a keyword argument.  Previously, this would
  cause the interpreter to crash if the interpreter was compiled with debug
  symbols. This does not affect interpreters compiled for release.  Patch by
  Ken Jin.

- bpo-42536: Several built-in and standard library types now ensure that
  their internal result tuples are always tracked by the :term:`garbage
  collector <garbage collection>`:

  - :meth:`collections.OrderedDict.items() <collections.OrderedDict>`

  - :meth:`dict.items`

  - :func:`enumerate`

  - :func:`functools.reduce`

  - :func:`itertools.combinations`

  - :func:`itertools.combinations_with_replacement`

  - :func:`itertools.permutations`

  - :func:`itertools.product`

  - :func:`itertools.zip_longest`

  - :func:`zip`

  Previously, they could have become untracked by a prior garbage
  collection. Patch by Brandt Bucher.

- bpo-42500: Improve handling of exceptions near recursion limit. Converts a
  number of Fatal Errors in RecursionErrors.

- bpo-42246: PEP 626: After a return, the f_lineno attribute of a frame is
  always the last line executed.

- bpo-42435: Speed up comparison of bytes objects with non-bytes objects
  when option :option:`-b` is specified. Speed up comparison of bytarray
  objects with non-buffer object.

- bpo-1635741: Port the ``_warnings`` extension module to the multi-phase
  initialization API (:pep:`489`). Patch by Victor Stinner.

- bpo-41686: On Windows, the ``SIGINT`` event, ``_PyOS_SigintEvent()``, is
  now created even if Python is configured to not install signal handlers
  (if :c:member:`PyConfig.install_signal_handlers` equals to 0, or
  ``Py_InitializeEx(0)``).

- bpo-42381: Allow assignment expressions in set literals and set
  comprehensions as per PEP 572. Patch by Pablo Galindo.

- bpo-42202: Change function parameters annotations internal representation
  to tuple of strings. Patch provided by Yurii Karabas.

- bpo-42374: Fix a regression introduced by the new parser, where an
  unparenthesized walrus operator was not allowed within generator
  expressions.

- bpo-42316: Allow an unparenthesized walrus in subscript indexes.

- bpo-42349: Make sure that the compiler front-end produces a well-formed
  control flow graph. Be be more aggressive in the compiler back-end, as it
  is now safe to do so.

- bpo-42296: On Windows, fix a regression in signal handling which prevented
  to interrupt a program using CTRL+C. The signal handler can be run in a
  thread different than the Python thread, in which case the test deciding
  if the thread can handle signals is wrong.

- bpo-42332: :class:`types.GenericAlias` objects can now be the targets of
  weakrefs.

- bpo-42282: Optimise constant subexpressions that appear as part of named
  expressions (previously the AST optimiser did not descend into named
  expressions). Patch by Nick Coghlan.

- bpo-42266: Fixed a bug with the LOAD_ATTR opcode cache that was not
  respecting monkey-patching a class-level attribute to make it a
  descriptor. Patch by Pablo Galindo.

- bpo-40077: Convert :mod:`queue` to use heap types.

- bpo-42246: Improved accuracy of line tracing events and f_lineno attribute
  of Frame objects. See PEP 626 for details.

- bpo-40077: Convert :mod:`mmap` to use heap types.

- bpo-42233: Allow ``GenericAlias`` objects to use :ref:`union type
  expressions <types-union>`. This allows expressions like ``list[int] |
  dict[float, str]`` where previously a ``TypeError`` would have been
  thrown.  This also fixes union type expressions not de-duplicating
  ``GenericAlias`` objects. (Contributed by Ken Jin in :issue:`42233`.)

- bpo-26131: The import system triggers a `ImportWarning` when it falls back
  to using `load_module()`.

Library
-------

- bpo-5054: CGIHTTPRequestHandler.run_cgi() HTTP_ACCEPT improperly parsed.
  Replace the special purpose getallmatchingheaders with generic get_all
  method and add relevant tests.

  Original Patch by Martin Panter. Modified by Senthil Kumaran.

- bpo-42562: Fix issue when dis failed to parse function that has no line
  numbers. Patch provided by Yurii Karabas.

- bpo-17735: :func:`inspect.findsource` now raises :exc:`OSError` instead of
  :exc:`IndexError` when :attr:`co_lineno` of a code object is greater than
  the file length. This can happen, for example, when a file is edited after
  it was imported.  PR by Irit Katriel.

- bpo-42116: Fix handling of trailing comments by :func:`inspect.getsource`.

- bpo-42532: Remove unexpected call of ``__bool__`` when passing a
  ``spec_arg`` argument to a Mock.

- bpo-38200: Added itertools.pairwise()

- bpo-41818: Fix test_master_read() so that it succeeds on all platforms
  that either raise OSError or return b"" upon reading from master.

- bpo-42487: ChainMap.__iter__ no longer calls __getitem__ on underlying
  maps

- bpo-42482: :class:`~traceback.TracebackException` no longer holds a
  reference to the exception's traceback object. Consequently, instances of
  TracebackException for equivalent but non-equal exceptions now compare as
  equal.

- bpo-41818: Make test_openpty() avoid unexpected success due to number of
  rows and/or number of columns being == 0.

- bpo-42392: Remove loop parameter from ``asyncio.subprocess`` and
  ``asyncio.tasks`` functions. Patch provided by Yurii Karabas.

- bpo-42392: Remove loop parameter from ``asyncio.open_connection`` and
  ``asyncio.start_server`` functions. Patch provided by Yurii Karabas.

- bpo-28468: Add :func:`platform.freedesktop_os_release` function to parse
  freedesktop.org ``os-release`` files.

- bpo-42299: Removed the ``formatter`` module, which was deprecated in
  Python 3.4. It is somewhat obsolete, little used, and not tested. It was
  originally scheduled to be removed in Python 3.6, but such removals were
  delayed until after Python 2.7 EOL. Existing users should copy whatever
  classes they use into their code. Patch by Dong-hee Na and and Terry J.
  Reedy.

- bpo-26131: Deprecate zipimport.zipimporter.load_module() in favour of
  exec_module().

- bpo-41818: Updated tests for the pty library. test_basic() has been
  changed to test_openpty(); this additionally checks if slave termios and
  slave winsize are being set properly by pty.openpty(). In order to add
  support for FreeBSD, NetBSD, OpenBSD, and Darwin, this also adds
  test_master_read(), which demonstrates that pty.spawn() should not depend
  on an OSError to exit from its copy loop.

- bpo-42392: Remove loop parameter from ``__init__`` in all
  ``asyncio.locks`` and ``asyncio.Queue`` classes. Patch provided by Yurii
  Karabas.

- bpo-15450: Make :class:`filecmp.dircmp` respect subclassing. Now the
  :attr:`filecmp.dircmp.subdirs` behaves as expected when subclassing
  dircmp.

- bpo-42413: The exception :exc:`socket.timeout` is now an alias of
  :exc:`TimeoutError`.

- bpo-31904: Support signal module on VxWorks.

- bpo-42406: We fixed an issue in `pickle.whichmodule` in which importing
  `multiprocessing` could change the how pickle identifies which module an
  object belongs to, potentially breaking the unpickling of those objects.

- bpo-42403: Simplify the :mod:`importlib` external bootstrap code:
  ``importlib._bootstrap_external`` now uses regular imports to import
  builtin modules. When it is imported, the builtin :func:`__import__()`
  function is already fully working and so can be used to import builtin
  modules like :mod:`sys`. Patch by Victor Stinner.

- bpo-1635741: Convert _sre module types to heap types (PEP 384). Patch by
  Erlend E. Aasland.

- bpo-42375: subprocess module update for DragonFlyBSD support.

- bpo-41713: Port the ``_signal`` extension module to the multi-phase
  initialization API (:pep:`489`). Patch by Victor Stinner and Mohamed
  Koubaa.

- bpo-37205: :func:`time.time()`, :func:`time.perf_counter()` and
  :func:`time.monotonic()` functions can no longer fail with a Python fatal
  error, instead raise a regular Python exception on failure.

- bpo-42328: Fixed :meth:`tkinter.ttk.Style.map`. The function accepts now
  the representation of the default state as empty sequence (as returned by
  ``Style.map()``). The structure of the result is now the same on all
  platform and does not depend on the value of ``wantobjects``.

- bpo-42345: Fix various issues with ``typing.Literal`` parameter handling
  (flatten, deduplicate, use type to cache key). Patch provided by Yurii
  Karabas.

- bpo-37205: :func:`time.perf_counter()` on Windows and
  :func:`time.monotonic()` on macOS are now system-wide. Previously, they
  used an offset computed at startup to reduce the precision loss caused by
  the float type. Use :func:`time.perf_counter_ns()` and
  :func:`time.monotonic_ns()` added in Python 3.7 to avoid this precision
  loss.

- bpo-42318: Fixed support of non-BMP characters in :mod:`tkinter` on macOS.

- bpo-42350: Fix the :class:`threading.Thread` class at fork: do nothing if
  the thread is already stopped (ex: fork called at Python exit).
  Previously, an error was logged in the child process.

- bpo-42333: Port _ssl extension module to heap types.

- bpo-42014: The ``onerror`` callback from ``shutil.rmtree`` now receives
  correct function when ``os.open`` fails.

- bpo-42237: Fix `os.sendfile()` on illumos.

- bpo-42308: Add :data:`threading.__excepthook__` to allow retrieving the
  original value of :func:`threading.excepthook` in case it is set to a
  broken or a different value. Patch by Mario Corchero.

- bpo-42131: Implement PEP 451/spec methods on zipimport.zipimporter:
  find_spec(), create_module(), and exec_module().

  This also allows for the documented deprecation of find_loader(),
  find_module(), and load_module().

- bpo-41877: Mock objects which are not unsafe will now raise an
  AttributeError if an attribute with the prefix asert, aseert, or assrt is
  accessed, in addition to this already happening for the prefixes assert or
  assret.

- bpo-42264: ``sqlite3.OptimizedUnicode`` has been undocumented and obsolete
  since Python 3.3, when it was made an alias to :class:`str`.  It is now
  deprecated, scheduled for removal in Python 3.12.

- bpo-42251: Added :func:`threading.gettrace` and
  :func:`threading.getprofile` to retrieve the functions set by
  :func:`threading.settrace` and :func:`threading.setprofile` respectively.
  Patch by Mario Corchero.

- bpo-42249: Fixed writing binary Plist files larger than 4 GiB.

- bpo-42236: On Unix, the :func:`os.device_encoding` function now returns
  ``'UTF-8'`` rather than the device encoding if the :ref:`Python UTF-8 Mode
  <utf8-mode>` is enabled.

- bpo-41754: webbrowser: Ignore *NotADirectoryError* when calling
  ``xdg-settings``.

- bpo-42183: Fix a stack overflow error for asyncio Task or Future repr().

  The overflow occurs under some circumstances when a Task or Future
  recursively returns itself.

- bpo-42140: Improve asyncio.wait function to create the futures set just
  one time.

- bpo-42133: Update various modules in the stdlib to fall back on
  `__spec__.loader` when `__loader__` isn't defined on a module.

- bpo-26131: The `load_module()` methods found in importlib now trigger a
  DeprecationWarning.

- bpo-39825: Windows: Change ``sysconfig.get_config_var('EXT_SUFFIX')`` to
  the expected full ``platform_tag.extension`` format. Previously it was
  hard-coded to ``.pyd``, now it is compatible with ``distutils.sysconfig``
  and will result in something like ``.cp38-win_amd64.pyd``. This brings
  windows into conformance with the other platforms.

- bpo-26389: The :func:`traceback.format_exception`,
  :func:`traceback.format_exception_only`, and
  :func:`traceback.print_exception` functions can now take an exception
  object as a positional-only argument.

- bpo-41889: Enum: fix regression involving inheriting a multiply-inherited
  enum

- bpo-41861: Convert :mod:`sqlite3` to use heap types (PEP 384). Patch by
  Erlend E. Aasland.

- bpo-40624: Added support for the XPath ``!=`` operator in xml.etree

- bpo-28850: Fix :meth:`pprint.PrettyPrinter.format` overrides being ignored
  for contents of small containers. The :func:`pprint._safe_repr` function
  was removed.

- bpo-41625: Expose the :c:func:`splice` as :func:`os.splice` in the
  :mod:`os` module. Patch by Pablo Galindo

- bpo-34215: Clarify the error message for
  :exc:`asyncio.IncompleteReadError` when ``expected`` is ``None``.

- bpo-41543: Add async context manager support for contextlib.nullcontext.

- bpo-21041: :attr:`pathlib.PurePath.parents` now supports negative
  indexing. Patch contributed by Yaroslav Pankovych.

- bpo-41332: Added missing connect_accepted_socket() method to
  ``asyncio.AbstractEventLoop``.

- bpo-12800: Extracting a symlink from a tarball should succeed and
  overwrite the symlink if it already exists. The fix is to remove the
  existing file or symlink before extraction. Based on patch by Chris AtLee,
  Jeffrey Kintscher, and Senthil Kumaran.

- bpo-40968: :mod:`urllib.request` and :mod:`http.client` now send
  ``http/1.1`` ALPN extension during TLS handshake when no custom context is
  supplied.

- bpo-41001: Add func:`os.eventfd` to provide a low level interface for
  Linux's event notification file descriptor.

- bpo-40816: Add AsyncContextDecorator to contextlib to support async
  context manager as a decorator.

- bpo-40550: Fix time-of-check/time-of-action issue in
  subprocess.Popen.send_signal.

- bpo-39411: Add an ``is_async`` identifier to :mod:`pyclbr`'s ``Function``
  objects. Patch by Batuhan Taskaya

- bpo-35498: Add slice support to :attr:`pathlib.PurePath.parents`.

Documentation
-------------

- bpo-42238: Tentative to deprecate ``make suspicious`` by first removing it
  from the CI and documentation builds, but keeping it around for manual
  uses.

- bpo-42153: Fix the URL for the IMAP protocol documents.

- bpo-41028: Language and version switchers, previously maintained in every
  cpython branches, are now handled by docsbuild-script.

Tests
-----

- bpo-41473: Re-enable test_gdb on gdb 9.2 and newer:
  https://bugzilla.redhat.com/show_bug.cgi?id=1866884 bug is fixed in gdb
  10.1.

- bpo-42553: Fix ``test_asyncio.test_call_later()`` race condition: don't
  measure asyncio performance in the ``call_later()`` unit test. The test
  failed randomly on the CI.

- bpo-31904: Fix test_netrc on VxWorks: create temporary directories using
  temp_cwd().

- bpo-31904: skip test_getaddrinfo_ipv6_scopeid_symbolic and
  test_getnameinfo_ipv6_scopeid_symbolic on VxWorks

- bpo-31904: skip test_test of test_mailcap on VxWorks

- bpo-31904: add shell requirement for test_pipes

- bpo-31904: skip some tests related to fifo on VxWorks

- bpo-31904: Fix test_doctest.py failures for VxWorks.

- bpo-40754: Include ``_testinternalcapi`` module in Windows installer for
  test suite

- bpo-41561: test_ssl: skip test_min_max_version_mismatch when TLS 1.0 is
  not available

- bpo-31904: Fix os module failures for VxWorks RTOS.

- bpo-31904: Fix fifo test cases for VxWorks RTOS.

Build
-----

- bpo-31904: remove libnet dependency from detect_socket() for VxWorks

- bpo-42398: Fix a race condition in "make regen-all" when make -jN option
  is used to run jobs in parallel. The clinic.py script now only use atomic
  write to write files. Moveover, generated files are now left unchanged if
  the content does not change, to not change the file modification time.

- bpo-41617: Fix building ``pycore_bitutils.h`` internal header on old clang
  version without ``__builtin_bswap16()`` (ex: Xcode 4.6.3 on Mac OS X
  10.7). Patch by Joshua Root and Victor Stinner.

- bpo-38823: It is no longer possible to build the ``_ctypes`` extension
  module without :c:type:`wchar_t` type: remove ``CTYPES_UNICODE`` macro.
  Anyway, the :c:type:`wchar_t` type is required to build Python. Patch by
  Victor Stinner.

- bpo-42087: Support was removed for AIX 5.3 and below. See :issue:`40680`.

- bpo-40998: Addressed three compiler warnings found by undefined behavior
  sanitizer (ubsan).

Windows
-------

- bpo-42120: Remove macro definition of ``copysign`` (to ``_copysign``) in
  headers.

- bpo-38506: The Windows launcher now properly handles Python 3.10 when
  listing installed Python versions.

macOS
-----

- bpo-42504: Fix build on macOS Big Sur when MACOSX_DEPLOYMENT_TARGET=11

- bpo-41116: Ensure distutils.unixxcompiler.find_library_file can find
  system provided libraries on macOS 11.

- bpo-41100: Add support for macOS 11 and Apple Silicon systems.

  It is now possible to build "Universal 2" binaries using
  "--enable-universalsdk --with-universal-archs=universal2".

  Binaries build on later macOS versions can be deployed back to older
  versions (tested up to macOS 10.9), when using the correct deployment
  target. This is tested using Xcode 11 and later.

- bpo-42232: Added Darwin specific madvise options to mmap module.

- bpo-38443: The ``--enable-universalsdk`` and ``--with-universal-archs``
  options for the configure script now check that the specified
  architectures can be used.

IDLE
----

- bpo-42508: Keep IDLE running on macOS.  Remove obsolete workaround that
  prevented running files with shortcuts when using new universal2
  installers built on macOS 11.

- bpo-42426: Fix reporting offset of the RE error in searchengine.

- bpo-42415: Get docstrings for IDLE calltips more often by using
  inspect.getdoc.

Tools/Demos
-----------

- bpo-42212: The smelly.py script now also checks the Python dynamic library
  and extension modules, not only the Python static library. Make also the
  script more verbose: explain what it does.

- bpo-36310: Allow :file:`Tools/i18n/pygettext.py` to detect calls to
  ``gettext`` in f-strings.

C API
-----

- bpo-42423: The :c:func:`PyType_FromSpecWithBases` and
  :c:func:`PyType_FromModuleAndSpec` functions now accept a single class as
  the *bases* argument.

- bpo-1635741: Port :mod:`select` extension module to multiphase
  initialization (:pep:`489`).

- bpo-1635741: Port _posixsubprocess extension module to multiphase
  initialization (:pep:`489`).

- bpo-1635741: Port _posixshmem extension module to multiphase
  initialization (:pep:`489`)

- bpo-1635741: Port _struct extension module to multiphase initialization
  (:pep:`489`)

- bpo-1635741: Port :mod:`spwd` extension module to multiphase
  initialization (:pep:`489`)

- bpo-1635741: Port :mod:`gc` extension module to multiphase initialization
  (:pep:`489`)

- bpo-1635741: Port _queue extension module to multiphase initialization
  (:pep:`489`)

- bpo-39573: Convert :c:func:`Py_TYPE` and :c:func:`Py_SIZE` back to macros
  to allow using them as an l-value. Many third party C extension modules
  rely on the ability of using Py_TYPE() and Py_SIZE() to set an object type
  and size: ``Py_TYPE(obj) = type;`` and ``Py_SIZE(obj) = size;``.

- bpo-1635741: Port :mod:`symtable` extension module to multiphase
  initialization (:pep:`489`)

- bpo-1635741: Port :mod:`grp` and :mod:`pwd` extension modules to
  multiphase initialization (:pep:`489`)

- bpo-1635741: Port _random extension module to multiphase initialization
  (:pep:`489`)

- bpo-1635741: Port _hashlib extension module to multiphase initialization
  (:pep:`489`)

- bpo-41713: Removed the undocumented ``PyOS_InitInterrupts()`` function.
  Initializing Python already implicitly installs signal handlers: see
  :c:member:`PyConfig.install_signal_handlers`. Patch by Victor Stinner.

- bpo-40170: The ``Py_TRASHCAN_BEGIN`` macro no longer accesses PyTypeObject
  attributes, but now can get the condition by calling the new private
  :c:func:`_PyTrash_cond()` function which hides implementation details.

- bpo-42260: :c:func:`Py_GetPath`, :c:func:`Py_GetPrefix`,
  :c:func:`Py_GetExecPrefix`, :c:func:`Py_GetProgramFullPath`,
  :c:func:`Py_GetPythonHome` and :c:func:`Py_GetProgramName` functions now
  return ``NULL`` if called before :c:func:`Py_Initialize` (before Python is
  initialized). Use the new :ref:`Python Initialization Configuration API
  <init-config>` to get the :ref:`Python Path Configuration.
  <init-path-config>`. Patch by Victor Stinner.

- bpo-42260: The :c:func:`PyConfig_Read` function now only parses
  :c:member:`PyConfig.argv` arguments once: :c:member:`PyConfig.parse_argv`
  is set to ``2`` after arguments are parsed. Since Python arguments are
  strippped from :c:member:`PyConfig.argv`, parsing arguments twice would
  parse the application options as Python options.

- bpo-42262: Added :c:func:`Py_NewRef` and :c:func:`Py_XNewRef` functions to
  increment the reference count of an object and return the object. Patch by
  Victor Stinner.

- bpo-42260: When :c:func:`Py_Initialize` is called twice, the second call
  now updates more :mod:`sys` attributes for the configuration, rather than
  only :data:`sys.argv`. Patch by Victor Stinner.

- bpo-41832: The :c:func:`PyType_FromModuleAndSpec` function now accepts
  NULL ``tp_doc`` slot.

- bpo-1635741: Added :c:func:`PyModule_AddObjectRef` function: similar to
  :c:func:`PyModule_AddObject` but don't steal a reference to the value on
  success. Patch by Victor Stinner.

- bpo-42171: The :c:data:`METH_FASTCALL` calling convention is added to the
  limited API. The functions  :c:func:`PyModule_AddType`,
  :c:func:`PyType_FromModuleAndSpec`, :c:func:`PyType_GetModule` and
  :c:func:`PyType_GetModuleState` are added to the limited API on Windows.

- bpo-42085: Add dedicated entry to PyAsyncMethods for sending values

- bpo-41073: :c:func:`PyType_GetSlot()` can now accept static types.

- bpo-30459: :c:func:`PyList_SET_ITEM`, :c:func:`PyTuple_SET_ITEM` and
  :c:func:`PyCell_SET` macros can no longer be used as l-value or r-value.
  For example, ``x = PyList_SET_ITEM(a, b, c)`` and ``PyList_SET_ITEM(a, b,
  c) = x`` now fail with a compiler error. It prevents bugs like ``if
  (PyList_SET_ITEM (a, b, c) < 0) ...`` test. Patch by Zackery Spytz and
  Victor Stinner.


What's New in Python 3.10.0 alpha 2?
====================================

*Release date: 2020-11-03*

Security
--------

- bpo-42103: Prevented potential DoS attack via CPU and RAM exhaustion when
  processing malformed Apple Property List files in binary format.

- bpo-42051: The :mod:`plistlib` module no longer accepts entity
  declarations in XML plist files to avoid XML vulnerabilities. This should
  not affect users as entity declarations are not used in regular plist
  files.

Core and Builtins
-----------------

- bpo-42236: If the ``nl_langinfo(CODESET)`` function returns an empty
  string, Python now uses UTF-8 as the filesystem encoding. Patch by Victor
  Stinner.

- bpo-42218: Fixed a bug in the PEG parser that was causing crashes in debug
  mode. Now errors are checked in left-recursive rules to avoid cases where
  such errors do not get handled in time and appear as long-distance crashes
  in other places.

- bpo-42214: Fixed a possible crash in the PEG parser when checking for the
  '!=' token in the ``barry_as_flufl`` rule. Patch by Pablo Galindo.

- bpo-42206: Propagate and raise the errors caused by
  :c:func:`PyAST_Validate` in the parser.

- bpo-41796: The :mod:`ast` module internal state is now per interpreter.
  Patch by Victor Stinner.

- bpo-42143: Fix handling of errors during creation of ``PyFunctionObject``,
  which resulted in operations on uninitialized memory. Patch by Yonatan
  Goldschmidt.

- bpo-41659: Fix a bug in the parser, where a curly brace following a
  `primary` didn't fail immediately. This led to invalid expressions like `a
  {b}` to throw a :exc:`SyntaxError` with a wrong offset, or invalid
  expressions ending with a curly brace like `a {` to not fail immediately
  in the REPL.

- bpo-42150: Fix possible buffer overflow in the new parser when checking
  for continuation lines. Patch by Pablo Galindo.

- bpo-42123: Run the parser two times. On the first run, disable all the
  rules that only generate better error messages to gain performance. If
  there's a parse failure, run the parser a second time with those enabled.

- bpo-42093: The ``LOAD_ATTR`` instruction now uses new "per opcode cache"
  mechanism and it is about 36% faster now. Patch by Pablo Galindo and Yury
  Selivanov.

- bpo-42030: Support for the legacy AIX-specific shared library loading
  support has been removed. All versions of AIX since 4.3 have supported and
  defaulted to using the common Unix mechanism instead.

- bpo-41984: The garbage collector now tracks all user-defined classes.
  Patch by Brandt Bucher.

- bpo-41993: Fixed potential issues with removing not completely initialized
  module from ``sys.modules`` when import fails.

- bpo-41979: Star-unpacking is now allowed for with item's targets in the
  PEG parser.

- bpo-41974: Removed special methods ``__int__``, ``__float__``,
  ``__floordiv__``, ``__mod__``, ``__divmod__``, ``__rfloordiv__``,
  ``__rmod__`` and ``__rdivmod__`` of the :class:`complex` class.  They
  always raised a :exc:`TypeError`.

- bpo-41902: Micro optimization when compute
  :c:member:`~PySequenceMethods.sq_item` and
  :c:member:`~PyMappingMethods.mp_subscript` of :class:`range`. Patch by
  Dong-hee Na.

- bpo-41894: When loading a native module and a load failure occurs, prevent
  a possible UnicodeDecodeError when not running in a UTF-8 locale by
  decoding the load error message using the current locale's encoding.

- bpo-41902: Micro optimization for range.index if step is 1. Patch by
  Dong-hee Na.

- bpo-41435: Add `sys._current_exceptions()` function to retrieve a
  dictionary mapping each thread's identifier to the topmost exception
  currently active in that thread at the time the function is called.

- bpo-38605: Enable ``from __future__ import annotations`` (:pep:`563`) by
  default. The values found in :attr:`__annotations__` dicts are now
  strings, e.g. ``{"x": "int"}`` instead of ``{"x": int}``.

Library
-------

- bpo-35455: On Solaris, :func:`~time.thread_time` is now implemented with
  ``gethrvtime()`` because ``clock_gettime(CLOCK_THREAD_CPUTIME_ID)`` is not
  always available. Patch by Jakub Kulik.

- bpo-42233: The :func:`repr` of :mod:`typing` types containing
  :ref:`Generic Alias Types <types-genericalias>` previously did not show
  the parameterized types in the ``GenericAlias``.  They have now been
  changed to do so.

- bpo-29566: ``binhex.binhex()`` consistently writes macOS 9 line endings.

- bpo-26789: The :class:`logging.FileHandler` class now keeps a reference to
  the builtin :func:`open` function to be able to open or reopen the file
  during Python finalization. Fix errors like: ``NameError: name 'open' is
  not defined``. Patch by Victor Stinner.

- bpo-42157: Removed the ``unicodedata.ucnhash_CAPI`` attribute which was an
  internal PyCapsule object. The related private ``_PyUnicode_Name_CAPI``
  structure was moved to the internal C API. Patch by Victor Stinner.

- bpo-42157: Convert the :mod:`unicodedata` extension module to the
  multiphase initialization API (:pep:`489`) and convert the
  ``unicodedata.UCD`` static type to a heap type. Patch by Mohamed Koubaa
  and Victor Stinner.

- bpo-42146: Fix memory leak in :func:`subprocess.Popen` in case an uid
  (gid) specified in `user` (`group`, `extra_groups`) overflows `uid_t`
  (`gid_t`).

- bpo-42103: :exc:`~plistlib.InvalidFileException` and :exc:`RecursionError`
  are now the only errors caused by loading malformed binary Plist file
  (previously ValueError and TypeError could be raised in some specific
  cases).

- bpo-41490: In ``importlib.resources``, ``.path`` method is more aggressive
  about releasing handles to zipfile objects early, enabling use-cases like
  certifi to leave the context open but delete the underlying zip file.

- bpo-41052: Pickling heap types implemented in C with protocols 0 and 1
  raises now an error instead of producing incorrect data.

- bpo-42089: In ``importlib.metadata.PackageNotFoundError``, make reference
  to the package metadata being missing to improve the user experience.

- bpo-41491: plistlib: fix parsing XML plists with hexadecimal integer
  values

- bpo-42065: Fix an incorrectly formatted error from
  :meth:`_codecs.charmap_decode` when called with a mapped value outside the
  range of valid Unicode code points. PR by Max Bernstein.

- bpo-41966: Fix pickling pure Python :class:`datetime.time` subclasses.
  Patch by Dean Inwood.

- bpo-19270: :meth:`sched.scheduler.cancel()` will now cancel the correct
  event, if two events with same priority are scheduled for the same time.
  Patch by Bar Harel.

- bpo-28660: :func:`textwrap.wrap` now attempts to break long words after
  hyphens when ``break_long_words=True`` and ``break_on_hyphens=True``.

- bpo-35823: Use ``vfork()`` instead of ``fork()`` for
  :func:`subprocess.Popen` on Linux to improve performance in cases where it
  is deemed safe.

- bpo-42043: Add support for ``zipfile.Path`` inheritance.
  ``zipfile.Path.is_file()`` now returns False for non-existent names.
  ``zipfile.Path`` objects now expose a ``.filename`` attribute and rely on
  that to resolve ``.name`` and ``.parent`` when the ``Path`` object is at
  the root of the zipfile.

- bpo-42021: Fix possible ref leaks in :mod:`sqlite3` module init.

- bpo-39101: Fixed tests using IsolatedAsyncioTestCase from hanging on
  BaseExceptions.

- bpo-41976: Fixed a bug that was causing :func:`ctypes.util.find_library`
  to return ``None`` when triying to locate a library in an environment when
  gcc>=9 is available and ``ldconfig`` is not. Patch by Pablo Galindo

- bpo-41943: Fix bug where TestCase.assertLogs doesn't correctly filter
  messages by level.

- bpo-41923: Implement :pep:`613`, introducing :data:`typing.TypeAlias`
  annotation.

- bpo-41905: A new function in abc: *update_abstractmethods* to re-calculate
  an abstract class's abstract status. In addition, *dataclass* has been
  changed to call this function.

- bpo-23706: Added *newline* parameter to ``pathlib.Path.write_text()``.

- bpo-41876: Tkinter font class repr uses font name

- bpo-41831: ``str()`` for the ``type`` attribute of the ``tkinter.Event``
  object always returns now the numeric code returned by Tk instead of the
  name of the event type.

- bpo-39337: :func:`encodings.normalize_encoding` now ignores non-ASCII
  characters.

- bpo-41747: Ensure all methods that generated from
  :func:`dataclasses.dataclass` objects now have the proper ``__qualname__``
  attribute referring to the class they belong to. Patch by Batuhan Taskaya.

- bpo-30681: Handle exceptions caused by unparsable date headers when using
  email "default" policy.  Patch by Tim Bell, Georges Toth

- bpo-41586: Add F_SETPIPE_SZ and F_GETPIPE_SZ to fcntl module. Allow
  setting pipesize on subprocess.Popen.

- bpo-41229: Add ``contextlib.aclosing`` for deterministic cleanup of async
  generators which is analogous to ``contextlib.closing`` for non-async
  generators. Patch by Joongi Kim and John Belmonte.

- bpo-16396: Allow ``ctypes.wintypes`` to be imported on non-Windows
  systems.

- bpo-4356: Add a key function to the bisect module.

- bpo-40592: :func:`shutil.which` now ignores empty entries in
  :envvar:`PATHEXT` instead of treating them as a match.

- bpo-40492: Fix ``--outfile`` for :mod:`cProfile` / :mod:`profile` not
  writing the output file in the original directory when the program being
  profiled changes the working directory.  PR by Anthony Sottile.

- bpo-34204: The :mod:`shelve` module now uses
  :data:`pickle.DEFAULT_PROTOCOL` by default instead of :mod:`pickle`
  protocol ``3``.

- bpo-27321: Fixed KeyError exception when flattening an email to a string
  attempts to replace a non-existent Content-Transfer-Encoding header.

- bpo-38976: The :mod:`http.cookiejar` module now supports the parsing of
  cookies in CURL-style cookiejar files through MozillaCookieJar on all
  platforms. Previously, such cookie entries would be silently ignored when
  loading a cookiejar with such entries.

  Additionally, the HTTP Only attribute is persisted in the object, and will
  be correctly written to file if the MozillaCookieJar object is
  subsequently dumped.

Documentation
-------------

- bpo-42061: Document __format__ functionality for IP addresses.

- bpo-41910: Document the default implementation of `object.__eq__`.

- bpo-42010: Clarify that subscription expressions are also valid for
  certain :term:`classes <class>` and :term:`types <type>` in the standard
  library, and for user-defined classes and types if the classmethod
  :meth:`__class_getitem__` is provided.

- bpo-41805: Documented :ref:`generic alias type <types-genericalias>` and
  :data:`types.GenericAlias`. Also added an entry in glossary for
  :term:`generic types <generic type>`.

- bpo-39693: Fix tarfile's extractfile documentation

- bpo-39416: Document some restrictions on the default string
  representations of numeric classes.

Tests
-----

- bpo-41739: Fix test_logging.test_race_between_set_target_and_flush(): the
  test now waits until all threads complete to avoid leaking running
  threads.

- bpo-41970: Avoid a test failure in ``test_lib2to3`` if the module has
  already imported at the time the test executes. Patch by Pablo Galindo.

- bpo-41944: Tests for CJK codecs no longer call ``eval()`` on content
  received via HTTP.

- bpo-41306: Fixed a failure in ``test_tk.test_widgets.ScaleTest`` happening
  when executing the test with Tk 8.6.10.

Build
-----

- bpo-38980: Add ``-fno-semantic-interposition`` to both the compile and
  link line when building with ``--enable-optimizations``. Patch by Victor
  Stinner and Pablo Galindo.

Windows
-------

- bpo-38439: Updates the icons for IDLE in the Windows Store package.

- bpo-38252: Use 8-byte step to detect ASCII sequence in 64-bit Windows
  build.

- bpo-39107: Update Tcl and Tk to 8.6.10 in Windows installer.

- bpo-41557: Update Windows installer to use SQLite 3.33.0.

- bpo-38324: Avoid Unicode errors when accessing certain locale data on
  Windows.

macOS
-----

- bpo-41471: Ignore invalid prefix lengths in system proxy excludes.

IDLE
----

- bpo-33987: Mostly finish using ttk widgets, mainly for editor, settings,
  and searches. Some patches by Mark Roseman.

- bpo-40511: Typing opening and closing parentheses inside the parentheses
  of a function call will no longer cause unnecessary "flashing" off and on
  of an existing open call-tip, e.g. when typed in a string literal.

- bpo-38439: Add a 256×256 pixel IDLE icon to the Windows .ico file. Created
  by Andrew Clover. Remove the low-color gif variations from the .ico file.

C API
-----

- bpo-42157: The private ``_PyUnicode_Name_CAPI`` structure of the PyCapsule
  API ``unicodedata.ucnhash_CAPI`` has been moved to the internal C API.
  Patch by Victor Stinner.

- bpo-42015: Fix potential crash in deallocating method objects when
  dynamically allocated `PyMethodDef`'s lifetime is managed through the
  ``self`` argument of a `PyCFunction`.

- bpo-40423: The :mod:`subprocess` module and ``os.closerange`` will now use
  the ``close_range(low, high, flags)`` syscall when it is available for
  more efficient closing of ranges of descriptors.

- bpo-41845: :c:func:`PyObject_GenericGetDict` is available again in the
  limited API when targeting 3.10 or later.

- bpo-40422: Add `_Py_closerange` function to provide performant closing of
  a range of file descriptors.

- bpo-41986: :c:data:`Py_FileSystemDefaultEncodeErrors` and
  :c:data:`Py_UTF8Mode` are available again in limited API.

- bpo-41756: Add `PyIter_Send` function to allow sending value into
  generator/coroutine/iterator without raising StopIteration exception to
  signal return.

- bpo-41784: Added ``PyUnicode_AsUTF8AndSize`` to the limited C API.


What's New in Python 3.10.0 alpha 1?
====================================

*Release date: 2020-10-05*

Security
--------

- bpo-41304: Fixes `python3x._pth` being ignored on Windows, caused by the
  fix for :issue:`29778` (CVE-2020-15801).

- bpo-41162: Audit hooks are now cleared later during finalization to avoid
  missing events.

- bpo-29778: Ensure :file:`python3.dll` is loaded from correct locations
  when Python is embedded (CVE-2020-15523).

- bpo-41004: The __hash__() methods of  ipaddress.IPv4Interface and
  ipaddress.IPv6Interface incorrectly generated constant hash values of 32
  and 128 respectively. This resulted in always causing hash collisions. The
  fix uses hash() to generate hash values for the tuple of (address, mask
  length, network address).

- bpo-39603: Prevent http header injection by rejecting control characters
  in http.client.putrequest(...).

Core and Builtins
-----------------

- bpo-41909: Fixed stack overflow in :func:`issubclass` and
  :func:`isinstance` when getting the ``__bases__`` attribute leads to
  infinite recursion.

- bpo-41922: Speed up calls to ``reversed()`` by using the :pep:`590`
  ``vectorcall`` calling convention. Patch by Dong-hee Na.

- bpo-41873: Calls to ``float()`` are now faster due to the ``vectorcall``
  calling convention. Patch by Dennis Sweeney.

- bpo-41870: Speed up calls to ``bool()`` by using the :pep:`590`
  ``vectorcall`` calling convention. Patch by Dong-hee Na.

- bpo-1635741: Port the :mod:`_bisect` module to the multi-phase
  initialization API (:pep:`489`).

- bpo-39934: Correctly count control blocks in 'except' in compiler. Ensures
  that a syntax error, rather a fatal error, occurs for deeply nested, named
  exception handlers.

- bpo-41780: Fix :meth:`__dir__` of :class:`types.GenericAlias`. Patch by
  Batuhan Taskaya.

- bpo-1635741: Port the :mod:`_lsprof` extension module to multi-phase
  initialization (:pep:`489`).

- bpo-1635741: Port the :mod:`cmath` extension module to multi-phase
  initialization (:pep:`489`).

- bpo-1635741: Port the :mod:`_scproxy` extension module to multi-phase
  initialization (:pep:`489`).

- bpo-1635741: Port the :mod:`termios` extension module to multi-phase
  initialization (:pep:`489`).

- bpo-1635741: Convert the :mod:`_sha256` extension module types to heap
  types.

- bpo-41690: Fix a possible stack overflow in the parser when parsing
  functions and classes with a huge amount of arguments. Patch by Pablo
  Galindo.

- bpo-1635741: Port the :mod:`_overlapped` extension module to multi-phase
  initialization (:pep:`489`).

- bpo-1635741: Port the :mod:`_curses_panel` extension module to multi-phase
  initialization (:pep:`489`).

- bpo-1635741: Port the :mod:`_opcode` extension module to multi-phase
  initialization (:pep:`489`).

- bpo-41681: Fixes the wrong error description in the error raised by using
  2 `,` in format string in f-string and :meth:`str.format`.

- bpo-41675: The implementation of :func:`signal.siginterrupt` now uses
  :c:func:`sigaction` (if it is available in the system) instead of the
  deprecated :c:func:`siginterrupt`. Patch by Pablo Galindo.

- bpo-41670: Prevent line trace being skipped on platforms not compiled with
  ``USE_COMPUTED_GOTOS``. Fixes issue where some lines nested within a
  try-except block were not being traced on Windows.

- bpo-41654: Fix a crash that occurred when destroying subclasses of
  :class:`MemoryError`. Patch by Pablo Galindo.

- bpo-1635741: Port the :mod:`zlib` extension module to multi-phase
  initialization (:pep:`489`).

- bpo-41631: The ``_ast`` module uses again a global state. Using a module
  state per module instance is causing subtle practical problems. For
  example, the Mercurial project replaces the ``__import__()`` function to
  implement lazy import, whereas Python expected that ``import _ast`` always
  return a fully initialized ``_ast`` module.

- bpo-40077: Convert :mod:`_operator` to use :c:func:`PyType_FromSpec`.

- bpo-1653741: Port :mod:`_sha3` to multi-phase init.  Convert static types
  to heap types.

- bpo-1635741: Port the :mod:`_blake2` extension module to the multi-phase
  initialization API (:pep:`489`).

- bpo-41533: Free the stack allocated in ``va_build_stack`` if
  ``do_mkstack`` fails and the stack is not a ``small_stack``.

- bpo-41531: Fix a bug that was dropping keys when compiling dict literals
  with more than 0xFFFF elements. Patch by Pablo Galindo.

- bpo-41525: The output of ``python --help`` contains now only ASCII
  characters.

- bpo-1635741: Port the :mod:`_sha1`, :mod:`_sha512`, and :mod:`_md5`
  extension modules to multi-phase initialization API (:pep:`489`).

- bpo-41431: Optimize ``dict_merge()`` for copying dict (e.g. ``dict(d)``
  and ``{}.update(d)``).

- bpo-41428: Implement PEP 604. This supports (int | str) etc. in place of
  Union[str, int].

- bpo-41340: Removed fallback implementation for ``strdup``.

- bpo-38156: Handle interrupts that come after EOF correctly in
  ``PyOS_StdioReadline``.

- bpo-41342: :func:`round` with integer argument is now faster (9--60%).

- bpo-41334: Constructors :func:`str`, :func:`bytes` and :func:`bytearray`
  are now faster (around 30--40% for small objects).

- bpo-41295: Resolve a regression in CPython 3.8.4 where defining
  "__setattr__" in a multi-inheritance setup and calling up the hierarchy
  chain could fail if builtins/extension types were involved in the base
  types.

- bpo-41323: Bytecode optimizations are performed directly on the control
  flow graph. This will result in slightly more compact code objects in some
  circumstances.

- bpo-41247: Always cache the running loop holder when running
  ``asyncio.set_running_loop``.

- bpo-41252: Fix incorrect refcounting in _ssl.c's
  ``_servername_callback()``.

- bpo-1635741: Port :mod:`multiprocessing` to multi-phase initialization

- bpo-1635741: Port :mod:`winapi` to multiphase initialization

- bpo-41215: Use non-NULL default values in the PEG parser keyword list to
  overcome a bug that was preventing Python from being properly compiled
  when using the XLC compiler. Patch by Pablo Galindo.

- bpo-41218: Python 3.8.3 had a regression where compiling with
  ast.PyCF_ALLOW_TOP_LEVEL_AWAIT would aggressively mark list comprehension
  with CO_COROUTINE. Now only list comprehension making use of async/await
  will tagged as so.

- bpo-1635741: Port :mod:`faulthandler` to multiphase initialization.

- bpo-1635741: Port :mod:`sha256` to multiphase initialization

- bpo-41175: Guard against a NULL pointer dereference within bytearrayobject
  triggered by the ``bytearray() + bytearray()`` operation.

- bpo-41100: add arm64 to the allowable Mac OS arches in mpdecimal.h

- bpo-41094: Fix decoding errors with audit when open files with non-ASCII
  names on non-UTF-8 locale.

- bpo-39960: The "hackcheck" that prevents sneaking around a type's
  __setattr__() by calling the superclass method was rewritten to allow C
  implemented heap types.

- bpo-41084: Prefix the error message with 'f-string: ', when parsing an
  f-string expression which throws a :exc:`SyntaxError`.

- bpo-40521: Empty frozensets are no longer singletons.

- bpo-41076: Pre-feed the parser with the location of the f-string
  expression, not the f-string itself, which allows us to skip the shifting
  of the AST node locations after the parsing is completed.

- bpo-41056: Fixes a reference to deallocated stack space during startup
  when constructing sys.path involving a relative symlink when code was
  supplied via -c.  (discovered via Coverity)

- bpo-41061: Fix incorrect expressions and asserts in hashtable code and
  tests.

- bpo-41052: Opt out serialization/deserialization for _random.Random

- bpo-40939: Rename `PyPegen*` functions to `PyParser*`, so that we can
  remove the old set of `PyParser*` functions that were using the old
  parser, but keep everything backwards-compatible.

- bpo-35975: Stefan Behnel reported that cf_feature_version is used even
  when PyCF_ONLY_AST is not set. This is against the intention and against
  the documented behavior, so it's been fixed.

- bpo-40939: Remove the remaining files from the old parser and the
  :mod:`symbol` module.

- bpo-40077: Convert :mod:`_bz2` to use :c:func:`PyType_FromSpec`.

- bpo-41006: The ``encodings.latin_1`` module is no longer imported at
  startup. Now it is only imported when it is the filesystem encoding or the
  stdio encoding.

- bpo-40636: :func:`zip` now supports :pep:`618`'s ``strict`` parameter,
  which raises a :exc:`ValueError` if the arguments are exhausted at
  different lengths. Patch by Brandt Bucher.

- bpo-1635741: Port :mod:`_gdbm` to multiphase initialization.

- bpo-40985: Fix a bug that caused the :exc:`SyntaxError` text to be empty
  when a file ends with a line ending in a line continuation character (i.e.
  backslash). The error text should contain the text of the last line.

- bpo-40958: Fix a possible buffer overflow in the PEG parser when gathering
  information for emitting syntax errors. Patch by Pablo Galindo.

- bpo-1635741: Port :mod:`_dbm` to multiphase initialization.

- bpo-40957: Fix refleak in _Py_fopen_obj() when PySys_Audit() fails

- bpo-40950: Add a state to the :mod:`nis` module (:pep:`3121`) and apply
  the multiphase initialization. Patch by Dong-hee Na.

- bpo-40947: The Python :ref:`Path Configuration <init-path-config>` now
  takes :c:member:`PyConfig.platlibdir` in account.

- bpo-40939: Remove the old parser, the :mod:`parser` module and all
  associated support code, command-line options and environment variables.
  Patch by Pablo Galindo.

- bpo-40847: Fix a bug where a line with only a line continuation character
  is not considered a blank line at tokenizer level. In such cases, more
  than a single `NEWLINE` token was emitted. The old parser was working
  around the issue, but the new parser threw a :exc:`SyntaxError` for valid
  input due to this. For example, an empty line following a line
  continuation character was interpreted as a :exc:`SyntaxError`.

- bpo-40890: Each dictionary view now has a ``mapping`` attribute that
  provides a :class:`types.MappingProxyType` wrapping the original
  dictionary.  Patch contributed by Dennis Sweeney.

- bpo-40889: Improved the performance of symmetric difference operations on
  dictionary item views.  Patch by Dennis Sweeney.

- bpo-40904: Fix possible segfault in the new PEG parser when parsing
  f-string containing yield statements with no value (:code:`f"{yield}"`).
  Patch by Pablo Galindo

- bpo-40903: Fixed a possible segfault in the new PEG parser when producing
  error messages for invalid assignments of the form :code:`p=p=`. Patch by
  Pablo Galindo

- bpo-40880: Fix invalid memory read in the new parser when checking
  newlines in string literals. Patch by Pablo Galindo.

- bpo-40883: Fix memory leak in when parsing f-strings in the new parser.
  Patch by Pablo Galindo

- bpo-40870: Raise :exc:`ValueError` when validating custom AST's where the
  constants ``True``, ``False`` and ``None`` are used within a
  :class:`ast.Name` node.

- bpo-40854: Allow overriding :data:`sys.platlibdir` via a new
  :envvar:`PYTHONPLATLIBDIR` environment variable.

- bpo-40826: Fix GIL usage in :c:func:`PyOS_Readline`: lock the GIL to set
  an exception and pass the Python thread state when checking if there is a
  pending signal.

- bpo-1635741: Port :mod:`fcntl` to multiphase initialization.

- bpo-19468: Delete unnecessary instance check in importlib.reload(). Patch
  by Furkan Önder.

- bpo-40824: Unexpected errors in calling the ``__iter__`` method are no
  longer masked by ``TypeError`` in the :keyword:`in` operator and functions
  :func:`~operator.contains`, :func:`~operator.indexOf` and
  :func:`~operator.countOf` of the :mod:`operator` module.

- bpo-40792: Attributes ``start``, ``stop`` and ``step`` of the
  :class:`range` object now always has exact type :class:`int`.  Previously,
  they could have been an instance of a subclass of ``int``.

- bpo-40780: Fix a corner case where g-style string formatting of a float
  failed to remove trailing zeros.

- bpo-38964: When there's a :exc:`SyntaxError` in the expression part of an
  fstring, the filename attribute of the :exc:`SyntaxError` gets correctly
  set to the name of the file the fstring resides in.

- bpo-40750: Support the "-d" debug flag in the new PEG parser. Patch by
  Pablo Galindo

- bpo-40217: Instances of types created with
  :c:func:`PyType_FromSpecWithBases` will no longer automatically visit
  their class object when traversing references in the garbage collector.
  The user is expected to manually visit the object's class. Patch by Pablo
  Galindo.

- bpo-39573: :c:func:`Py_TYPE()` is changed to the inline static function.
  Patch by Dong-hee Na.

- bpo-40696: Fix a hang that can arise after :meth:`generator.throw` due to
  a cycle in the exception context chain.

- bpo-40521: Each interpreter now its has own free lists, singletons and
  caches:

  * Free lists: float, tuple, list, dict, frame, context,
    asynchronous generator, MemoryError.
  * Singletons: empty tuple, empty bytes string, empty Unicode string,
    single byte character, single Unicode (latin1) character.
  * Slice cache.

  They are no longer shared by all interpreters.

- bpo-40679: Certain :exc:`TypeError` messages about missing or extra
  arguments now include the function's :term:`qualified name`.  Patch by
  Dennis Sweeney.

- bpo-29590: Make the stack trace correct after calling
  :meth:`generator.throw` on a generator that has yielded from a ``yield
  from``.

- bpo-4022: Improve performance of generators by not raising internal
  StopIteration.

- bpo-1635741: Port :mod:`mmap` to multiphase initialization.

- bpo-1635741: Port :mod:`_lzma` to multiphase initialization.

- bpo-37999: Builtin and extension functions that take integer arguments no
  longer accept :class:`~decimal.Decimal`\ s, :class:`~fractions.Fraction`\
  s and other objects that can be converted to integers only with a loss
  (e.g. that have the :meth:`~object.__int__` method but do not have the
  :meth:`~object.__index__` method).

- bpo-29882: Add :meth:`int.bit_count()`, counting the number of ones in the
  binary representation of an integer. Patch by Niklas Fiekas.

- bpo-36982: Use ncurses extended color functions when available to support
  terminals with 256 colors, and add the new function
  :func:`curses.has_extended_color_support` to indicate whether extended
  color support is provided by the underlying ncurses library.

- bpo-19569: Add the private macros ``_Py_COMP_DIAG_PUSH``,
  ``_Py_COMP_DIAG_IGNORE_DEPR_DECLS``, and ``_Py_COMP_DIAG_POP``.

- bpo-26680: The int type now supports the x.is_integer() method for
  compatibility with float.

Library
-------

- bpo-41900: C14N 2.0 serialisation in xml.etree.ElementTree failed for
  unprefixed attributes when a default namespace was defined.

- bpo-41887: Strip leading spaces and tabs on :func:`ast.literal_eval`. Also
  document stripping of spaces and tabs for :func:`eval`.

- bpo-41773: Note in documentation that :func:`random.choices` doesn't
  support non-finite weights, raise :exc:`ValueError` when given non-finite
  weights.

- bpo-41840: Fix a bug in the :mod:`symtable` module that was causing
  module-scope global variables to not be reported as both local and global.
  Patch by Pablo Galindo.

- bpo-41842: Add :func:`codecs.unregister` function to unregister a codec
  search function.

- bpo-40564: In ``zipfile.Path``, mutate the passed ZipFile object type
  instead of making a copy. Prevents issues when both the local copy and the
  caller’s copy attempt to close the same file handle.

- bpo-40670: More reliable validation of statements in
  :class:`timeit.Timer`. It now accepts "empty" statements (only whitespaces
  and comments) and rejects misindentent statements.

- bpo-41833: The :class:`threading.Thread` constructor now uses the target
  name if the *target* argument is specified but the *name* argument is
  omitted.

- bpo-41817: fix `tkinter.EventType` Enum so all members are strings, and
  none are tuples

- bpo-41810: :data:`types.EllipsisType`, :data:`types.NotImplementedType`
  and :data:`types.NoneType` have been reintroduced, providing a new set of
  types readily interpretable by static type checkers.

- bpo-41815: Fix SQLite3 segfault when backing up closed database. Patch
  contributed by Peter David McCormick.

- bpo-41816: StrEnum added: it ensures that all members are already strings
  or string candidates

- bpo-41517: fix bug allowing Enums to be extended via multiple inheritance

- bpo-39587: use the correct mix-in data type when constructing Enums

- bpo-41792: Add is_typeddict function to typing.py to check if a type is a
  TypedDict class

  Previously there was no way to check that without using private API. See
  the `relevant issue in python/typing
  <https://github.com/python/typing/issues/751>`

- bpo-41789: Honor `object` overrides in `Enum` class creation
  (specifically, `__str__`, `__repr__`, `__format__`, and `__reduce_ex__`).

- bpo-32218: `enum.Flag` and `enum.IntFlag` members are now iterable

- bpo-39651: Fix a race condition in the ``call_soon_threadsafe()`` method
  of ``asyncio.ProactorEventLoop``: do nothing if the self-pipe socket has
  been closed.

- bpo-1635741: Port the ``mashal`` extension module to the multi-phase
  initialization API (:pep:`489`).

- bpo-1635741: Port the ``_string`` extension module to the multi-phase
  initialization API (:pep:`489`).

- bpo-41732: Added an :term:`iterator` to :class:`memoryview`.

- bpo-41720: Fixed :meth:`turtle.Vec2D.__rmul__` for arguments which are not
  int or float.

- bpo-41696: Fix handling of debug mode in :func:`asyncio.run`. This allows
  setting ``PYTHONASYNCIODEBUG`` or ``-X dev`` to enable asyncio debug mode
  when using :func:`asyncio.run`.

- bpo-41687: Fix implementation of sendfile to be compatible with Solaris.

- bpo-41662: No longer override exceptions raised in ``__len__()`` of a
  sequence of parameters in :mod:`sqlite3` with
  :exc:`~sqlite3.ProgrammingError`.

- bpo-39010: Restarting a ``ProactorEventLoop`` on Windows no longer logs
  spurious ``ConnectionResetErrors``.

- bpo-41638: :exc:`~sqlite3.ProgrammingError` message for absent parameter
  in :mod:`sqlite3` contains now the name of the parameter instead of its
  index when parameters are supplied as a dict.

- bpo-41662: Fixed crash when mutate list of parameters during iteration in
  :mod:`sqlite3`.

- bpo-41513: Improved the accuracy of math.hypot().  Internally, each step
  is computed with extra precision so that the result is now almost always
  correctly rounded.

- bpo-41609: The pdb whatis command correctly reports instance methods as
  'Method' rather than 'Function'.

- bpo-39994: Fixed pprint's handling of dict subclasses that override
  __repr__.

- bpo-32751: When cancelling the task due to a timeout,
  :meth:`asyncio.wait_for` will now wait until the cancellation is complete
  also in the case when *timeout* is <= 0, like it does with positive
  timeouts.

- bpo-37658: :meth:`asyncio.wait_for` now properly handles races between
  cancellation of itself and the completion of the wrapped awaitable.

- bpo-40782: Change the method asyncio.AbstractEventLoop.run_in_executor to
  not be a coroutine.

- bpo-41520: Fix :mod:`codeop` regression that prevented turning compile
  warnings into errors.

- bpo-41528: turtle uses math module functions to convert degrees to radians
  and vice versa and to calculate vector norm

- bpo-41513: Minor algorithmic improvement to math.hypot() and math.dist()
  giving small gains in speed and accuracy.

- bpo-41503: Fixed a race between setTarget and flush in
  logging.handlers.MemoryHandler.

- bpo-41497: Fix potential UnicodeDecodeError in dis module.

- bpo-41467: On Windows, fix asyncio ``recv_into()`` return value when the
  socket/pipe is closed (:exc:`BrokenPipeError`): return ``0`` rather than
  an empty byte string (``b''``).

- bpo-41425: Make tkinter doc example runnable.

- bpo-41421: Make an algebraic simplification to random.paretovariate().  It
  now is slightly less subject to round-off error and is slightly faster.
  Inputs that used to cause ZeroDivisionError now cause an OverflowError
  instead.

- bpo-41440: Add :func:`os.cpu_count()` support for VxWorks RTOS.

- bpo-41316: Fix the :mod:`tarfile` module to write only basename of TAR
  file to GZIP compression header.

- bpo-41384: Raise TclError instead of TypeError when an unknown option is
  passed to tkinter.OptionMenu.

- bpo-41317: Use add_done_callback() in asyncio.loop.sock_accept() to
  unsubscribe reader early on cancellation.

- bpo-41364: Reduce import overhead of :mod:`uuid`.

- bpo-35328: Set the environment variable ``VIRTUAL_ENV_PROMPT`` at
  :mod:`venv` activation.

- bpo-41341: Recursive evaluation of `typing.ForwardRef` in
  `get_type_hints`.

- bpo-41344: Prevent creating :class:`shared_memory.SharedMemory` objects
  with :code:`size=0`.

- bpo-41333: :meth:`collections.OrderedDict.pop` is now 2 times faster.

- bpo-41288: Unpickling invalid NEWOBJ_EX opcode with the C implementation
  raises now UnpicklingError instead of crashing.

- bpo-39017: Avoid infinite loop when reading specially crafted TAR files
  using the tarfile module (CVE-2019-20907).

- bpo-41273: Speed up any transport using ``_ProactorReadPipeTransport`` by
  calling ``recv_into`` instead of ``recv``, thus not creating a new buffer
  for each ``recv`` call in the transport's read loop.

- bpo-41235: Fix the error handling in
  :meth:`ssl.SSLContext.load_dh_params`.

- bpo-41207: In distutils.spawn, restore expectation that DistutilsExecError
  is raised when the command is not found.

- bpo-29727: Register :class:`array.array` as a
  :class:`~collections.abc.MutableSequence`. Patch by Pablo Galindo.

- bpo-39168: Remove the ``__new__`` method of :class:`typing.Generic`.

- bpo-41194: Fix a crash in the ``_ast`` module: it can no longer be loaded
  more than once. It now uses a global state rather than a module state.

- bpo-41195: Add read-only ssl.SSLContext.security_level attribute to
  retrieve the context's security level.

- bpo-41193: The ``write_history()`` atexit function of the readline
  completer now ignores any :exc:`OSError` to ignore error if the filesystem
  is read-only, instead of only ignoring :exc:`FileNotFoundError` and
  :exc:`PermissionError`.

- bpo-41182: selector: use DefaultSelector based upon implementation

- bpo-41161: The decimal module now requires libmpdec-2.5.0. Users of
  --with-system-libmpdec should update their system library.

- bpo-40874: The decimal module now requires libmpdec-2.5.0.

- bpo-41138: Fixed the :mod:`trace` module CLI for Python source files with
  non-UTF-8 encoding.

- bpo-31082: Use the term "iterable" in the docstring for
  :func:`functools.reduce`.

- bpo-40521: Remove freelist from collections.deque().

- bpo-31938: Fix default-value signatures of several functions in the
  :mod:`select` module - by Anthony Sottile.

- bpo-41068: Fixed reading files with non-ASCII names from ZIP archive
  directly after writing them.

- bpo-41058: :func:`pdb.find_function` now correctly determines the source
  file encoding.

- bpo-41056: Invalid file descriptor values are now prevented from being
  passed to os.fpathconf. (discovered by Coverity)

- bpo-41056: Fix a NULL pointer dereference within the ssl module during a
  MemoryError in the keylog callback. (discovered by Coverity)

- bpo-41056: Fixed an instance where a MemoryError within the zoneinfo
  module might not be reported or not reported at its source. (found by
  Coverity)

- bpo-41048: :func:`mimetypes.read_mime_types` function reads the rule file
  using UTF-8 encoding, not the locale encoding. Patch by Srinivas Reddy
  Thatiparthy.

- bpo-41043: Fixed the use of :func:`~glob.glob` in the stdlib: literal part
  of the path is now always correctly escaped.

- bpo-41025: Fixed an issue preventing the C implementation of
  :class:`zoneinfo.ZoneInfo` from being subclassed.

- bpo-35018: Add the :class:`xml.sax.handler.LexicalHandler` class that is
  present in other SAX XML implementations.

- bpo-41002: Improve performance of HTTPResponse.read with a given amount.
  Patch by Bruce Merry.

- bpo-40448: :mod:`ensurepip` now disables the use of `pip` cache when
  installing the bundled versions of `pip` and `setuptools`.  Patch by
  Krzysztof Konopko.

- bpo-40967: Removed :meth:`asyncio.Task.current_task` and
  :meth:`asyncio.Task.all_tasks`. Patch contributed by Rémi Lapeyre.

- bpo-40924: Ensure ``importlib.resources.path`` returns an extant path for
  the SourceFileLoader's resource reader. Avoids the regression identified
  in master while a long-term solution is devised.

- bpo-40955: Fix a minor memory leak in :mod:`subprocess` module when
  extra_groups was specified.

- bpo-40855: The standard deviation and variance functions in the statistics
  module were ignoring their mu and xbar arguments.

- bpo-40939: Use the new PEG parser when generating the stdlib
  :mod:`keyword` module.

- bpo-23427: Add :data:`sys.orig_argv` attribute: the list of the original
  command line arguments passed to the Python executable.

- bpo-33689: Ignore empty or whitespace-only lines in .pth files. This
  matches the documentated behavior. Before, empty lines caused the
  site-packages dir to appear multiple times in sys.path. By Ido Michael,
  contributors Malcolm Smith and Tal Einat.

- bpo-40884: Added a `defaults` parameter to :class:`logging.Formatter`, to
  allow specifying default values for custom fields. Patch by Asaf Alon and
  Bar Harel.

- bpo-40876: Clarify error message in the :mod:`csv` module.

- bpo-39791: Refresh importlib.metadata from importlib_metadata 1.6.1.

- bpo-40807: Stop codeop._maybe_compile, used by code.InteractiveInterpreter
  (and IDLE). from emitting each warning three times.

- bpo-32604: Fix reference leak in the :mod:`select` module when the module
  is imported in a subinterpreter.

- bpo-39791: Built-in loaders (SourceFileLoader and ZipImporter) now supply
  ``TraversableResources`` implementations for ``ResourceReader``, and the
  fallback function has been removed.

- bpo-39314: :class:`rlcompleter.Completer` and the standard Python shell
  now close the parenthesis for functions that take no arguments. Patch
  contributed by Rémi Lapeyre.

- bpo-17005: The topological sort functionality that was introduced
  initially in the :mod:`functools` module has been moved to a new
  :mod:`graphlib` module to better accommodate the new tools and keep the
  original scope of the :mod:`functools` module. Patch by Pablo Galindo

- bpo-40834: Fix truncate when sending str object
  with_xxsubinterpreters.channel_send.

- bpo-40755: Add rich comparisons to collections.Counter().

- bpo-26407: Unexpected errors in calling the ``__iter__`` method are no
  longer masked by ``TypeError`` in :func:`csv.reader`,
  :func:`csv.writer.writerow` and :meth:`csv.writer.writerows`.

- bpo-39384: Fixed email.contentmanager to allow set_content() to set a null
  string.

- bpo-40744: The :mod:`sqlite3` module uses SQLite API functions that
  require SQLite v3.7.3 or higher.  This patch removes support for older
  SQLite versions, and explicitly requires SQLite 3.7.3 both at build,
  compile and runtime.  Patch by Sergey Fedoseev and Erlend E. Aasland.

- bpo-40777: Initialize PyDateTime_IsoCalendarDateType.tp_base at run-time
  to avoid errors on some compilers.

- bpo-38488: Update ensurepip to install pip 20.1.1 and setuptools 47.1.0.

- bpo-40792: The result of :func:`operator.index` now always has exact type
  :class:`int`. Previously, the result could have been an instance of a
  subclass of ``int``.

- bpo-40767: :mod:`webbrowser` now properly finds the default browser in
  pure Wayland systems by checking the WAYLAND_DISPLAY environment variable.
  Patch contributed by Jérémy Attali.

- bpo-40791: :func:`hashlib.compare_digest` uses OpenSSL's
  ``CRYPTO_memcmp()`` function when OpenSSL is available.

- bpo-40795: :mod:`ctypes` module: If ctypes fails to convert the result of
  a callback or if a ctypes callback function raises an exception,
  sys.unraisablehook is now called with an exception set. Previously, the
  error was logged into stderr by :c:func:`PyErr_Print`.

- bpo-16995: Add :func:`base64.b32hexencode` and :func:`base64.b32hexdecode`
  to support the Base32 Encoding with Extended Hex Alphabet.

- bpo-30008: Fix :mod:`ssl` code to be compatible with OpenSSL 1.1.x builds
  that use ``no-deprecated`` and ``--api=1.1.0``.

- bpo-30064: Fix asyncio ``loop.sock_*`` race condition issue

- bpo-40759: Deprecate the :mod:`symbol` module.

- bpo-40756: The second argument (extra) of ``LoggerAdapter.__init__`` now
  defaults to None.

- bpo-37129: Add a new :data:`os.RWF_APPEND` flag for :func:`os.pwritev`.

- bpo-40737: Fix possible reference leak for :mod:`sqlite3` initialization.

- bpo-40726: Handle cases where the ``end_lineno`` is ``None`` on
  :func:`ast.increment_lineno`.

- bpo-40698: :mod:`distutils` upload creates SHA2-256 and Blake2b-256
  digests. MD5 digests is skipped if platform blocks MD5.

- bpo-40695: :mod:`hashlib` no longer falls back to builtin hash
  implementations when OpenSSL provides a hash digest and the algorithm is
  blocked by security policy.

- bpo-9216: func:`hashlib.new` passed ``usedforsecurity`` to OpenSSL EVP
  constructor ``_hashlib.new()``. test_hashlib and test_smtplib handle
  strict security policy better.

- bpo-40614: :func:`ast.parse` will not parse self documenting expressions
  in f-strings when passed ``feature_version`` is less than ``(3, 8)``.

- bpo-40626: Add h5 file extension as MIME Type application/x-hdf5, as per
  HDF Group recommendation for HDF5 formatted data files. Patch contributed
  by Mark Schwab.

- bpo-25920: On macOS, when building Python for macOS 10.4 and older, which
  wasn't the case for python.org macOS installer, :func:`socket.getaddrinfo`
  no longer uses an internal lock to prevent race conditions when calling
  ``getaddrinfo()`` which is thread-safe since macOS 10.5. Python 3.9
  requires macOS 10.6 or newer. The internal lock caused random hang on fork
  when another thread was calling :func:`socket.getaddrinfo`. The lock was
  also used on FreeBSD older than 5.3, OpenBSD older than 201311 and NetBSD
  older than 4.

- bpo-40671: Prepare ``_hashlib`` for :pep:`489` and use
  :c:func:`PyModule_AddType`.

- bpo-32309: Added a new :term:`coroutine` :func:`asyncio.to_thread`. It is
  mainly used for running IO-bound functions in a separate thread to avoid
  blocking the event loop, and essentially works as a high-level version of
  :meth:`~asyncio.loop.run_in_executor` that can directly take keyword
  arguments.

- bpo-36543: Restored the deprecated :mod:`xml.etree.cElementTree` module.

- bpo-40611: :data:`~mmap.MAP_POPULATE` constant has now been added to the
  list of exported :mod:`mmap` module flags.

- bpo-39881: PEP 554 for use in the test suite. (Patch By Joannah Nanjekye)

- bpo-13097: ``ctypes`` now raises an ``ArgumentError`` when a callback is
  invoked with more than 1024 arguments.

- bpo-39385: A new test assertion context-manager,
  :func:`unittest.assertNoLogs` will ensure a given block of code emits no
  log messages using the logging module. Contributed by Kit Yan Choi.

- bpo-23082: Updated the error message and docs of PurePath.relative_to() to
  better reflect the function behaviour.

- bpo-40318: Use SQLite3 trace v2 API, if it is available.

- bpo-40105: ZipFile truncates files to avoid corruption when a shorter
  comment is provided in append ("a") mode. Patch by Jan Mazur.

- bpo-40084: Fix ``Enum.__dir__``: dir(Enum.member) now includes attributes
  as well as methods.

- bpo-31122: ssl.wrap_socket() now raises ssl.SSLEOFError rather than
  OSError when peer closes connection during TLS negotiation

- bpo-39728: fix default `_missing_` so a duplicate `ValueError` is not set
  as the `__context__` of the original `ValueError`

- bpo-39244: Fixed :class:`multiprocessing.context.get_all_start_methods` to
  properly return the default method first on macOS.

- bpo-39040: Fix parsing of invalid mime headers parameters by collapsing
  whitespace between encoded words in a bare-quote-string.

- bpo-38731: Add ``--quiet`` option to command-line interface of
  :mod:`py_compile`. Patch by Gregory Schevchenko.

- bpo-35714: :exc:`struct.error` is now raised if there is a null character
  in a :mod:`struct` format string.

- bpo-38144: Added the *root_dir* and *dir_fd* parameters in
  :func:`glob.glob`.

- bpo-26543: Fix :meth:`IMAP4.noop()` when debug mode is enabled (ex:
  ``imaplib.Debug = 3``).

- bpo-12178: :func:`csv.writer` now correctly escapes *escapechar* when
  input contains *escapechar*.  Patch by Catalin Iacob, Berker Peksag, and
  Itay Elbirt.

- bpo-36290: AST nodes are now raising :exc:`TypeError` on conflicting
  keyword arguments. Patch contributed by Rémi Lapeyre.

- bpo-33944: Added site.py site-packages tracing in verbose mode.

- bpo-35078: Refactor formatweekday, formatmonthname methods in
  LocaleHTMLCalendar and LocaleTextCalendar classes in calendar module to
  call the base class methods.This enables customizable CSS classes for
  LocaleHTMLCalendar. Patch by Srinivas Reddy Thatiparthy

- bpo-29620: :func:`~unittest.TestCase.assertWarns` no longer raises a
  ``RuntimeException`` when accessing a module's ``__warningregistry__``
  causes importation of a new module, or when a new module is imported in
  another thread. Patch by Kernc.

- bpo-31844: Remove ``ParserBase.error()`` method from the private and
  undocumented ``_markupbase`` module.  :class:`html.parser.HTMLParser` is
  the only subclass of ``ParserBase`` and its ``error()`` implementation was
  deprecated in Python 3.4 and removed in Python 3.5.

- bpo-34226: Fix `cgi.parse_multipart` without content_length. Patch by
  Roger Duran

- bpo-33660: Fix pathlib.PosixPath to resolve a relative path located on the
  root directory properly.

- bpo-28557: Improve the error message for a misbehaving ``rawio.readinto``

- bpo-26680: The d.is_integer() method is added to the Decimal type, for
  compatibility with other number types.

- bpo-26680: The x.is_integer() method is incorporated into the abstract
  types of the numeric tower, Real, Rational and Integral, with appropriate
  default implementations.

Documentation
-------------

- bpo-41428: Add documentation for :pep:`604` (Allow writing union types as
  ``X | Y``).

- bpo-41774: In Programming FAQ "Sequences (Tuples/Lists)" section, add "How
  do you remove multiple items from a list".

- bpo-35293: Fix RemovedInSphinx40Warning when building the documentation.
  Patch by Dong-hee Na.

- bpo-37149: Change Shipman tkinter doc link from archive.org to TkDocs.
  (The doc has been removed from the NMT server.)  The new link responds
  much faster and includes a short explanatory note.

- bpo-41726: Update the refcounts info of ``PyType_FromModuleAndSpec``.

- bpo-41624: Fix the signature of :class:`typing.Coroutine`.

- bpo-40204: Enable Sphinx 3.2 ``c_allow_pre_v3`` option and disable
  ``c_warn_on_allowed_pre_v3`` option to make the documentation compatible
  with Sphinx 2 and Sphinx 3.

- bpo-41045: Add documentation for debug feature of f-strings.

- bpo-41314: Changed the release when ``from __future__ import annotations``
  becomes the default from ``4.0`` to ``3.10`` (following a change in PEP
  563).

- bpo-40979: Refactored typing.rst, arranging more than 70 classes,
  functions, and decorators into new sub-sections.

- bpo-40552: Fix in tutorial section 4.2. Code snippet is now correct.

- bpo-39883: Make code, examples, and recipes in the Python documentation be
  licensed under the more permissive BSD0 license in addition to the
  existing Python 2.0 license.

- bpo-37703: Updated Documentation to comprehensively elaborate on the
  behaviour of gather.cancel()

Tests
-----

- bpo-41939: Fix test_site.test_license_exists_at_url(): call
  ``urllib.request.urlcleanup()`` to reset the global
  ``urllib.request._opener``. Patch by Victor Stinner.

- bpo-41731: Make test_cmd_line_script pass with option '-vv'.

- bpo-41602: Add tests for SIGINT handling in the runpy module.

- bpo-41521: :mod:`test.support`: Rename ``blacklist`` parameter of
  :func:`~test.support.check__all__` to ``not_exported``.

- bpo-41477: Make ctypes optional in test_genericalias.

- bpo-41085: Fix integer overflow in the :meth:`array.array.index` method on
  64-bit Windows for index larger than ``2**31``.

- bpo-41069: :data:`test.support.TESTFN` and the current directory for tests
  when run via ``test.regrtest`` contain now non-ascii characters if
  possible.

- bpo-38377: On Linux, skip tests using multiprocessing if the current user
  cannot create a file in ``/dev/shm/`` directory. Add the
  :func:`~test.support.skip_if_broken_multiprocessing_synchronize` function
  to the :mod:`test.support` module.

- bpo-41009: Fix use of ``support.require_{linux|mac|freebsd}_version()``
  decorators as class decorator.

- bpo-41003: Fix ``test_copyreg`` when ``numpy`` is installed:
  ``test.pickletester`` now saves/restores warnings filters when importing
  ``numpy``, to ignore filters installed by ``numpy``.

- bpo-40964: Disable remote :mod:`imaplib` tests, host cyrus.andrew.cmu.edu
  is blocking incoming connections.

- bpo-40927: Fix test_binhex when run twice: it now uses
  import_fresh_module() to ensure that it raises DeprecationWarning each
  time.

- bpo-17258: Skip some :mod:`multiprocessing` tests when MD5 hash digest is
  blocked.

- bpo-31904: Increase LOOPBACK_TIMEOUT to 10 for VxWorks RTOS.

- bpo-38169: Increase code coverage for SharedMemory and ShareableList

- bpo-34401: Make test_gdb properly run on HP-UX. Patch by Michael Osipov.

Build
-----

- bpo-38249: Update :c:macro:`Py_UNREACHABLE` to use __builtin_unreachable()
  if only the compiler is able to use it. Patch by Dong-hee Na.

- bpo-41617: Fix ``pycore_bitutils.h`` header file to support old clang
  versions: ``__builtin_bswap16()`` is not available in LLVM clang 3.0.

- bpo-40204: Pin Sphinx version to 2.3.1 in ``Doc/Makefile``.

- bpo-36020: The C99 functions :c:func:`snprintf` and :c:func:`vsnprintf`
  are now required to build Python.

- bpo-40684: ``make install`` now uses the ``PLATLIBDIR`` variable for the
  destination ``lib-dynload/`` directory when ``./configure
  --with-platlibdir`` is used.

- bpo-40683: Fixed an issue where the :mod:`zoneinfo` module and its tests
  were not included when Python is installed with ``make``.

Windows
-------

- bpo-41744: Fixes automatic import of props file when using the Nuget
  package.

- bpo-41627: The user site directory for 32-bit now includes a ``-32``
  suffix to distinguish it from the 64-bit interpreter's directory.

- bpo-41526: Fixed layout of final page of the installer by removing the
  special thanks to Mark Hammond (with his permission).

- bpo-41492: Fixes the description that appears in UAC prompts.

- bpo-40948: Improve post-install message to direct people to the "py"
  command.

- bpo-41412: The installer will now fail to install on Windows 7 and Windows
  8. Further, the UCRT dependency is now always downloaded on demand.

- bpo-40741: Update Windows release to include SQLite 3.32.3.

- bpo-41142: :mod:`msilib` now supports creating CAB files with non-ASCII
  file path and adding files with non-ASCII file path to them.

- bpo-41074: Fixed support of non-ASCII names in functions
  :func:`msilib.OpenDatabase` and :func:`msilib.init_database` and non-ASCII
  SQL in method :meth:`msilib.Database.OpenView`.

- bpo-41039: Stable ABI redirection DLL (python3.dll) now uses ``#pragma
  comment(linker)`` for re-exporting.

- bpo-40164: Updates Windows OpenSSL to 1.1.1g

- bpo-39631: Changes the registered MIME type for ``.py`` files on Windows
  to ``text/x-python`` instead of ``text/plain``.

- bpo-40677: Manually define IO_REPARSE_TAG_APPEXECLINK in case some old
  Windows SDK doesn't have it.

- bpo-37556: Extend py.exe help to mention overrides via venv, shebang,
  environmental variables & ini files.

macOS
-----

- bpo-41557: Update macOS installer to use SQLite 3.33.0.

- bpo-39580: Avoid opening Finder window if running installer from the
  command line. Patch contributed by Rick Heil.

- bpo-41100: Fix configure error when building on macOS 11. Note that the
  current Python release was released shortly after the first developer
  preview of macOS 11 (Big Sur); there are other known issues with building
  and running on the developer preview. Big Sur is expected to be fully
  supported in a future bugfix release of Python 3.8.x and with 3.9.0.

- bpo-40741: Update macOS installer to use SQLite 3.32.3.

- bpo-41005: fixed an XDG settings issue not allowing macos to open browser
  in webbrowser.py

- bpo-40741: Update macOS installer to use SQLite 3.32.2.

IDLE
----

- bpo-41775: Use 'IDLE Shell' as shell title

- bpo-35764: Rewrite the Calltips doc section.

- bpo-40181: In calltips, stop reminding that '/' marks the end of
  positional-only arguments.

- bpo-41468: Improve IDLE run crash error message (which users should never
  see).

- bpo-41373: Save files loaded with no line ending, as when blank, or
  different line endings, by setting its line ending to the system default.
  Fix regression in 3.8.4 and 3.9.0b4.

- bpo-41300: Save files with non-ascii chars. Fix regression released in
  3.9.0b4 and 3.8.4.

- bpo-37765: Add keywords to module name completion list.  Rewrite
  Completions section of IDLE doc.

- bpo-41152: The encoding of ``stdin``, ``stdout`` and ``stderr`` in IDLE is
  now always UTF-8.

- bpo-41144: Make Open Module open a special module such as os.path.

- bpo-39885: Make context menu Cut and Copy work again when right-clicking
  within a selection.

- bpo-40723: Make test_idle pass when run after import.

C API
-----

- bpo-41936: Removed undocumented macros ``Py_ALLOW_RECURSION`` and
  ``Py_END_ALLOW_RECURSION`` and the ``recursion_critical`` field of the
  :c:type:`PyInterpreterState` structure.

- bpo-41692: The ``PyUnicode_InternImmortal()`` function is now deprecated
  and will be removed in Python 3.12: use :c:func:`PyUnicode_InternInPlace`
  instead. Patch by Victor Stinner.

- bpo-41842: Add :c:func:`PyCodec_Unregister` function to unregister a codec
  search function.

- bpo-41834: Remove the ``_Py_CheckRecursionLimit`` variable: it has been
  replaced by ``ceval.recursion_limit`` of the :c:type:`PyInterpreterState`
  structure. Patch by Victor Stinner.

- bpo-41689: Types created with :c:func:`PyType_FromSpec` now make any
  signature in their ``tp_doc`` slot accessible from ``__text_signature__``.

- bpo-41524: Fix bug in PyOS_mystrnicmp and PyOS_mystricmp that incremented
  pointers beyond the end of a string.

- bpo-41324: Add a minimal decimal capsule API.  The API supports fast
  conversions between Decimals up to 38 digits and their triple
  representation as a C struct.

- bpo-30155: Add :c:func:`PyDateTime_DATE_GET_TZINFO` and
  :c:func:`PyDateTime_TIME_GET_TZINFO` macros for accessing the ``tzinfo``
  attributes of :class:`datetime.datetime` and :class:`datetime.time`
  objects.

- bpo-40170: Revert :c:func:`PyType_HasFeature` change: it reads again
  directly the :c:member:`PyTypeObject.tp_flags` member when the limited C
  API is not used, rather than always calling :c:func:`PyType_GetFlags`
  which hides implementation details.

- bpo-41123: Remove ``PyUnicode_AsUnicodeCopy``.

- bpo-41123: Removed ``PyLong_FromUnicode()``.

- bpo-41123: Removed ``PyUnicode_GetMax()``.

- bpo-41123: Removed ``Py_UNICODE_str*`` functions manipulating
  ``Py_UNICODE*`` strings.

- bpo-41103: ``PyObject_AsCharBuffer()``, ``PyObject_AsReadBuffer()``,
  ``PyObject_CheckReadBuffer()``, and ``PyObject_AsWriteBuffer()`` are
  removed. Please migrate to new buffer protocol;
  :c:func:`PyObject_GetBuffer` and :c:func:`PyBuffer_Release`.

- bpo-36346: Raises DeprecationWarning for ``PyUnicode_FromUnicode(NULL,
  size)`` and ``PyUnicode_FromStringAndSize(NULL, size)`` with ``size > 0``.

- bpo-36346: Mark ``Py_UNICODE_COPY``, ``Py_UNICODE_FILL``,
  ``PyUnicode_WSTR_LENGTH``, ``PyUnicode_FromUnicode``,
  ``PyUnicode_AsUnicode``, and ``PyUnicode_AsUnicodeAndSize`` as deprecated
  in C. Remove ``Py_UNICODE_MATCH`` which was deprecated and broken since
  Python 3.3.

- bpo-40989: The :c:func:`PyObject_INIT` and :c:func:`PyObject_INIT_VAR`
  macros become aliases to, respectively, :c:func:`PyObject_Init` and
  :c:func:`PyObject_InitVar` functions.

- bpo-36020: On Windows, ``#include "pyerrors.h"`` no longer defines
  ``snprintf`` and ``vsnprintf`` macros.

- bpo-40943: The ``PY_SSIZE_T_CLEAN`` macro must now be defined to use
  :c:func:`PyArg_ParseTuple` and :c:func:`Py_BuildValue` formats which use
  ``#``: ``es#``, ``et#``, ``s#``, ``u#``, ``y#``, ``z#``, ``U#`` and
  ``Z#``. See :ref:`Parsing arguments and building values <arg-parsing>` and
  the :pep:`353`.

- bpo-40910: Export explicitly the :c:func:`Py_GetArgcArgv` function to the
  C API and document the function. Previously, it was exported implicitly
  which no longer works since Python is built with ``-fvisibility=hidden``.

- bpo-40724: Allow defining buffer slots in type specs.

- bpo-40679: Fix a ``_PyEval_EvalCode()`` crash if *qualname* argument is
  NULL.

- bpo-40839: Calling :c:func:`PyDict_GetItem` without :term:`GIL` held had
  been allowed for historical reason. It is no longer allowed.

- bpo-40826: :c:func:`PyOS_InterruptOccurred` now fails with a fatal error
  if it is called with the GIL released.

- bpo-40792: The result of :c:func:`PyNumber_Index` now always has exact
  type :class:`int`. Previously, the result could have been an instance of a
  subclass of ``int``.

- bpo-39573: Convert :c:func:`Py_REFCNT` and :c:func:`Py_SIZE` macros to
  static inline functions. They cannot be used as l-value anymore: use
  :c:func:`Py_SET_REFCNT` and :c:func:`Py_SET_SIZE` to set an object
  reference count and size. This change is backward incompatible on purpose,
  to prepare the C API for an opaque :c:type:`PyObject` structure.

- bpo-40703: The PyType_FromSpec*() functions no longer overwrite the type's
  "__module__" attribute if it is set via "Py_tp_members" or "Py_tp_getset".

- bpo-39583: Remove superfluous "extern C" declarations from
  ``Include/cpython/*.h``.


What's New in Python 3.9.0 beta 1?
==================================

*Release date: 2020-05-19*

Security
--------

- bpo-40501: :mod:`uuid` no longer uses :mod:`ctypes` to load
  :file:`libuuid` or :file:`rpcrt4.dll` at runtime.

Core and Builtins
-----------------

- bpo-40663: Correctly generate annotations where parentheses are omitted
  but required (e.g: ``Type[(str, int, *other))]``.

- bpo-40596: Fixed :meth:`str.isidentifier` for non-canonicalized strings
  containing non-BMP characters on Windows.

- bpo-40593: Improved syntax errors for invalid characters in source code.

- bpo-40585: Fixed a bug when using :func:`codeop.compile_command` that was
  causing exceptions to be swallowed with the new parser. Patch by Pablo
  Galindo

- bpo-40566: Apply :pep:`573` to :mod:`abc`.

- bpo-40502: Initialize ``n->n_col_offset``. (Patch by Joannah Nanjekye)

- bpo-40527: Fix command line argument parsing: no longer write errors
  multiple times into stderr.

- bpo-1635741: Port :mod:`errno` to multiphase initialization (:pep:`489`).

- bpo-40523: Add pass-throughs for :func:`hash` and :func:`reversed` to
  :class:`weakref.proxy` objects. Patch by Pablo Galindo.

- bpo-1635741: Port :mod:`syslog` to multiphase initialization (:pep:`489`).

- bpo-40246: Reporting a specialised error message for invalid string
  prefixes, which was introduced in :issue:`40246`, is being reverted due to
  backwards compatibility concerns for strings that immediately follow a
  reserved keyword without whitespace between them. Constructs like
  `bg="#d00" if clear else"#fca"` were failing to parse, which is not an
  acceptable breakage on such short notice.

- bpo-40417: Fix imp module deprecation warning when PyImport_ReloadModule
  is called. Patch by Robert Rouhani.

- bpo-40408: Fixed support of nested type variables in GenericAlias (e.g.
  ``list[list[T]]``).

- bpo-1635741: Port _stat module to multiphase initialization (:pep:`489`).

- bpo-29587: Enable implicit exception chaining when calling
  :meth:`generator.throw`.

- bpo-40328: Add tools for generating mappings headers for CJKCodecs.

- bpo-40228: Setting frame.f_lineno is now robust w.r.t. changes in the
  source-to-bytecode compiler

- bpo-38880: Added the ability to list interpreters associated with channel
  ends in the internal subinterpreters module.

- bpo-37986: Improve performance of :c:func:`PyLong_FromDouble` for values
  that fit into :c:type:`long`.

Library
-------

- bpo-40662: Fixed :func:`ast.get_source_segment` for ast nodes that have
  incomplete location information. Patch by Irit Katriel.

- bpo-40665: Convert :mod:`bisect` to use Argument Clinic.

- bpo-40536: Added the :func:`~zoneinfo.available_timezones` function to the
  :mod:`zoneinfo` module. Patch by Paul Ganssle.

- bpo-40645: The :class:`hmac.HMAC` exposes internal implementation details.
  The attributes ``digest_cons``, ``inner``, and ``outer`` are deprecated
  and will be removed in the future.

- bpo-40645: The internal module ``_hashlib`` wraps and exposes OpenSSL's
  HMAC API. The new code will be used in Python 3.10 after the internal
  implementation details of the pure Python HMAC module are no longer part
  of the public API.

- bpo-40637: Builtin hash modules can now be disabled or selectively enabled
  with ``configure --with-builtin-hashlib-hashes=sha3,blake1`` or
  ``--without-builtin-hashlib-hashes``.

- bpo-37630: The :mod:`hashlib` module can now use SHA3 hashes and SHAKE XOF
  from OpenSSL when available.

- bpo-40479: The :mod:`hashlib` now compiles with OpenSSL 3.0.0-alpha2.

- bpo-40257: Revert changes to :func:`inspect.getdoc`.

- bpo-40607: When cancelling a task due to timeout, :meth:`asyncio.wait_for`
  will now propagate the exception if an error happens during cancellation.
  Patch by Roman Skurikhin.

- bpo-40612: Fix edge cases in SyntaxError formatting. If the offset is <=
  0, no caret is printed. If the offset is > line length, the caret is
  printed pointing just after the last character.

- bpo-40597: If text content lines are longer than policy.max_line_length,
  always use a content-encoding to make sure they are wrapped.

- bpo-40571: Added functools.cache() as a simpler, more discoverable way to
  access the unbounded cache variant of lru_cache(maxsize=None).

- bpo-40503: :pep:`615`, the :mod:`zoneinfo` module. Adds support for the
  IANA time zone database.

- bpo-40397: Removed attributes ``__args__`` and ``__parameters__`` from
  special generic aliases like ``typing.List`` (not subscripted).

- bpo-40549: Convert posixmodule.c ("posix" or "nt" module) to the
  multiphase initialization (PEP 489).

- bpo-31033: Add a ``msg`` argument to :meth:`Future.cancel` and
  :meth:`Task.cancel`.

- bpo-40541: Added an optional *counts* parameter to random.sample().

- bpo-40515: The :mod:`ssl` and :mod:`hashlib` modules now actively check
  that OpenSSL is build with thread support. Python 3.7.0 made thread
  support mandatory and no longer works safely with a no-thread builds.

- bpo-31033: When a :class:`asyncio.Task` is cancelled, the exception
  traceback now chains all the way back to where the task was first
  interrupted.

- bpo-40504: :func:`functools.lru_cache` objects can now be the targets of
  weakrefs.

- bpo-40559: Fix possible memory leak in the C implementation of
  :class:`asyncio.Task`.

- bpo-40480: ``fnmatch.fnmatch()`` could take exponential time in the
  presence of multiple ``*`` pattern characters.  This was repaired by
  generating more elaborate regular expressions to avoid futile
  backtracking.

- bpo-40495: :mod:`compileall` is now able to use hardlinks to prevent
  duplicates in a case when ``.pyc`` files for different optimization levels
  have the same content.

- bpo-40457: The ssl module now support OpenSSL builds without TLS 1.0 and
  1.1 methods.

- bpo-40355: Improve error reporting in :func:`ast.literal_eval` in the
  presence of malformed :class:`ast.Dict` nodes instead of silently ignoring
  any non-conforming elements. Patch by Curtis Bucher.

- bpo-40465: Deprecated the optional *random* argument to
  *random.shuffle()*.

- bpo-40459: :func:`platform.win32_ver` now produces correct *ptype* strings
  instead of empty strings.

- bpo-39435: The first argument of :func:`pickle.loads` is now
  positional-only.

- bpo-39305: Update :mod:`nntplib` to merge :class:`nntplib.NNTP` and
  :class:`nntplib._NNTPBase`. Patch by Dong-hee Na.

- bpo-32494: Update :mod:`dbm.gnu` to use gdbm_count if possible when
  calling :func:`len`. Patch by Dong-hee Na.

- bpo-40453: Add ``isolated=True`` keyword-only parameter to
  ``_xxsubinterpreters.create()``. An isolated subinterpreter cannot spawn
  threads, spawn a child process or call ``os.fork()``.

- bpo-40286: Remove ``_random.Random.randbytes()``: the C implementation of
  ``randbytes()``. Implement the method in Python to ease subclassing:
  ``randbytes()`` now directly reuses ``getrandbits()``.

- bpo-40394: Added default arguments to
  :meth:`difflib.SequenceMatcher.find_longest_match()`.

- bpo-39995: Fix a race condition in concurrent.futures._ThreadWakeup:
  access to _ThreadWakeup is now protected with the shutdown lock.

- bpo-30966: ``Process.shutdown(wait=True)`` of :mod:`concurrent.futures`
  now closes explicitly the result queue.

- bpo-30966: Add a new :meth:`~multiprocessing.SimpleQueue.close` method to
  the :class:`~multiprocessing.SimpleQueue` class to explicitly close the
  queue.

- bpo-39966: Revert bpo-25597. :class:`unittest.mock.MagicMock` with wraps'
  set uses default return values for magic methods.

- bpo-39791: Added ``files()`` function to importlib.resources with support
  for subdirectories in package data, matching backport in
  importlib_resources 1.5.

- bpo-40375: :meth:`imaplib.IMAP4.unselect` is added. Patch by Dong-hee Na.

- bpo-40389: ``repr()`` now returns ``typing.Optional[T]`` when called for
  ``typing.Union`` of two types, one of which is ``NoneType``.

- bpo-40291: Add support for CAN_J1939 sockets (available on Linux 5.4+)

- bpo-40273: :class:`types.MappingProxyType` is now reversible.

- bpo-39075: The repr for :class:`types.SimpleNamespace` is now insertion
  ordered rather than alphabetical.

- bpo-40192: On AIX, :func:`~time.thread_time` is now implemented with
  ``thread_cputime()`` which has nanosecond resolution, rather than
  ``clock_gettime(CLOCK_THREAD_CPUTIME_ID)`` which has a resolution of 10
  ms. Patch by Batuhan Taskaya.

- bpo-40025: Raise TypeError when _generate_next_value_ is defined after
  members. Patch by Ethan Onstott.

- bpo-39058: In the argparse module, the repr for Namespace() and other
  argument holders now displayed in the order attributes were added.
  Formerly, it displayed in alphabetical order even though argument order is
  preserved the user visible parts of the module.

- bpo-24416: The ``isocalendar()`` methods of :class:`datetime.date` and
  :class:`datetime.datetime` now return a :term:`named tuple` instead of a
  :class:`tuple`.

Documentation
-------------

- bpo-34790: Add version of removal for explicit passing of coros to
  `asyncio.wait()`'s documentation

- bpo-40561: Provide docstrings for webbrowser open functions.

- bpo-40499: Mention that :func:`asyncio.wait` requires a non-empty set of
  awaitables.

- bpo-39705: Tutorial example for sorted() in the Loop Techniques section is
  given a better explanation. Also a new example is included to explain
  sorted()'s basic behavior.

- bpo-39435: Fix an incorrect signature for :func:`pickle.loads` in the docs

Tests
-----

- bpo-40055: distutils.tests now saves/restores warnings filters to leave
  them unchanged. Importing tests imports docutils which imports
  pkg_resources which adds a warnings filter.

- bpo-40436: test_gdb and test.pythoninfo now check gdb command exit code.

Build
-----

- bpo-40653: Move _dirnameW out of HAVE_SYMLINK to fix a potential compiling
  issue.

- bpo-40514: Add ``--with-experimental-isolated-subinterpreters`` build
  option to ``configure``: better isolate subinterpreters, experimental
  build mode.

Windows
-------

- bpo-40650: Include winsock2.h in pytime.c for timeval.

- bpo-40458: Increase reserved stack space to prevent overflow crash on
  Windows.

- bpo-39148: Add IPv6 support to :mod:`asyncio` datagram endpoints in
  ProactorEventLoop. Change the raised exception for unknown address
  families to ValueError as it's not coming from Windows API.

macOS
-----

- bpo-34956: When building Python on macOS from source, ``_tkinter`` now
  links with non-system Tcl and Tk frameworks if they are installed in
  ``/Library/Frameworks``, as had been the case on older releases of macOS.
  If a macOS SDK is explicitly configured, by using
  ``--enable-universalsdk=`` or ``-isysroot``, only the SDK itself is
  searched. The default behavior can still be overridden with
  ``--with-tcltk-includes`` and ``--with-tcltk-libs``.

- bpo-35569: Expose RFC 3542 IPv6 socket options.

Tools/Demos
-----------

- bpo-40479: Update multissltest helper to test with latest OpenSSL 1.0.2,
  1.1.0, 1.1.1, and 3.0.0-alpha.

- bpo-40431: Fix a syntax typo in ``turtledemo`` that now raises a
  ``SyntaxError``.

- bpo-40163: Fix multissltest tool. OpenSSL has changed download URL for old
  releases. The multissltest tool now tries to download from current and old
  download URLs.

C API
-----

- bpo-39465: Remove the ``_PyUnicode_ClearStaticStrings()`` function from
  the C API.

- bpo-38787: Add PyCFunction_CheckExact() macro for exact type checks now
  that we allow subtypes of PyCFunction, as well as PyCMethod_CheckExact()
  and PyCMethod_Check() for the new PyCMethod subtype.

- bpo-40545: Declare ``_PyErr_GetTopmostException()`` with ``PyAPI_FUNC()``
  to properly export the function in the C API. The function remains private
  (``_Py``) prefix.

- bpo-40412: Nullify inittab_copy during finalization, preventing future
  interpreter initializations in an embedded situation from crashing. Patch
  by Gregory Szorc.

- bpo-40429: The :c:func:`PyThreadState_GetFrame` function now returns a
  strong reference to the frame.

- bpo-40428: Remove the following functions from the C API. Call
  :c:func:`PyGC_Collect` explicitly to free all free lists.

  * ``PyAsyncGen_ClearFreeLists()``
  * ``PyContext_ClearFreeList()``
  * ``PyDict_ClearFreeList()``
  * ``PyFloat_ClearFreeList()``
  * ``PyFrame_ClearFreeList()``
  * ``PyList_ClearFreeList()``
  * ``PySet_ClearFreeList()``
  * ``PyTuple_ClearFreeList()``

- bpo-40421: New :c:func:`PyFrame_GetBack` function: get the frame next
  outer frame.

- bpo-40421: New :c:func:`PyFrame_GetCode` function: return a borrowed
  reference to the frame code.

- bpo-40217: Ensure that instances of types created with
  :c:func:`PyType_FromSpecWithBases` will visit its class object when
  traversing references in the garbage collector (implemented as an
  extension of the provided :c:member:`~PyTypeObject.tp_traverse`). Patch by
  Pablo Galindo.

- bpo-38787: Module C state is now accessible from C-defined heap type
  methods (:pep:`573`). Patch by Marcel Plch and Petr Viktorin.


What's New in Python 3.9.0 alpha 6?
===================================

*Release date: 2020-04-27*

Security
--------

- bpo-40121: Fixes audit events raised on creating a new socket.

- bpo-39073: Disallow CR or LF in email.headerregistry.Address arguments to
  guard against header injection attacks.

- bpo-39503: CVE-2020-8492: The
  :class:`~urllib.request.AbstractBasicAuthHandler` class of the
  :mod:`urllib.request` module uses an inefficient regular expression which
  can be exploited by an attacker to cause a denial of service. Fix the
  regex to prevent the catastrophic backtracking. Vulnerability reported by
  Ben Caller and Matt Schwager.

Core and Builtins
-----------------

- bpo-40313: Improve the performance of bytes.hex().

- bpo-40334: Switch to a new parser, based on PEG.  For more details see PEP
  617. To temporarily switch back to the old parser, use ``-X oldparser`` or
  ``PYTHONOLDPARSER=1``.  In Python 3.10 we will remove the old parser
  completely, including the ``parser`` module (already deprecated) and
  anything that depends on it.

- bpo-40267: Fix the tokenizer to display the correct error message, when
  there is a SyntaxError on the last input character and no newline follows.
  It used to be `unexpected EOF while parsing`, while it should be `invalid
  syntax`.

- bpo-39522: Correctly unparse explicit ``u`` prefix for strings when
  postponed evaluation for annotations activated. Patch by Batuhan Taskaya.

- bpo-40246: Report a specialized error message, `invalid string prefix`,
  when the tokenizer encounters a string with an invalid prefix.

- bpo-40082: Fix the signal handler: it now always uses the main
  interpreter, rather than trying to get the current Python thread state.

- bpo-37388: str.encode() and str.decode() no longer check the encoding and
  errors in development mode or in debug mode during Python finalization.
  The codecs machinery can no longer work on very late calls to str.encode()
  and str.decode().

- bpo-40077: Fix possible refleaks in :mod:`_json`, memo of PyScannerObject
  should be traversed.

- bpo-37207: Speed up calls to ``dict()`` by using the :pep:`590`
  ``vectorcall`` calling convention.

- bpo-40141: Add column and line information to ``ast.keyword`` nodes. Patch
  by Pablo Galindo.

- bpo-1635741: Port :mod:`resource` to multiphase initialization
  (:pep:`489`).

- bpo-1635741: Port :mod:`math` to multiphase initialization (:pep:`489`).

- bpo-1635741: Port _uuid module to multiphase initialization (:pep:`489`).

- bpo-40077: Convert json module to use :c:func:`PyType_FromSpec`.

- bpo-40067: Improve the error message for multiple star expressions in an
  assignment. Patch by Furkan Onder

- bpo-1635741: Port _functools module to multiphase initialization (PEP
  489). Patch by Paulo Henrique Silva.

- bpo-1635741: Port operator module to multiphase initialization (PEP 489).
  Patch by Paulo Henrique Silva.

- bpo-20526: Fix :c:func:`PyThreadState_Clear()`. ``PyThreadState.frame`` is
  a borrowed reference, not a strong reference: ``PyThreadState_Clear()``
  must not call ``Py_CLEAR(tstate->frame)``.

- bpo-1635741: Port time module to multiphase initialization (:pep:`489`).
  Patch by Paulo Henrique Silva.

- bpo-1635741: Port _weakref extension module to multiphase initialization
  (:pep:`489`).

- bpo-40020: Fix a leak and subsequent crash in parsetok.c caused by realloc
  misuse on a rare codepath.

- bpo-39939: Added str.removeprefix and str.removesuffix methods and
  corresponding bytes, bytearray, and collections.UserString methods to
  remove affixes from a string if present. See :pep:`616` for a full
  description. Patch by Dennis Sweeney.

- bpo-39481: Implement PEP 585. This supports list[int], tuple[str, ...]
  etc.

- bpo-32894: Support unparsing of infinity numbers in postponed annotations.
  Patch by Batuhan Taşkaya.

- bpo-37207: Speed up calls to ``list()`` by using the :pep:`590`
  ``vectorcall`` calling convention. Patch by Mark Shannon.

Library
-------

- bpo-40398: :func:`typing.get_args` now always returns an empty tuple for
  special generic aliases.

- bpo-40396: Functions :func:`typing.get_origin`, :func:`typing.get_args`
  and :func:`typing.get_type_hints` support now generic aliases like
  ``list[int]``.

- bpo-38061: Optimize the :mod:`subprocess` module on FreeBSD using
  ``closefrom()``. A single ``close(fd)`` syscall is cheap, but when
  ``sysconf(_SC_OPEN_MAX)`` is high, the loop calling ``close(fd)`` on each
  file descriptor can take several milliseconds.

  The workaround on FreeBSD to improve performance was to load and mount the
  fdescfs kernel module, but this is not enabled by default.

  Initial patch by Ed Maste (emaste), Conrad Meyer (cem), Kyle Evans
  (kevans) and Kubilay Kocak (koobs):
  https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=242274

- bpo-38061: On FreeBSD, ``os.closerange(fd_low, fd_high)`` now calls
  ``closefrom(fd_low)`` if *fd_high* is greater than or equal to
  ``sysconf(_SC_OPEN_MAX)``.

  Initial patch by Ed Maste (emaste), Conrad Meyer (cem), Kyle Evans
  (kevans) and Kubilay Kocak (koobs):
  https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=242274

- bpo-40360: The :mod:`lib2to3` module is pending deprecation due to
  :pep:`617`.

- bpo-40138: Fix the Windows implementation of :func:`os.waitpid` for exit
  code larger than ``INT_MAX >> 8``. The exit status is now interpreted as
  an unsigned number.

- bpo-39942: Set "__main__" as the default module name when "__name__" is
  missing in :class:`typing.TypeVar`. Patch by Weipeng Hong.

- bpo-40275: The :mod:`logging` package is now imported lazily in
  :mod:`unittest` only when the :meth:`~unittest.TestCase.assertLogs`
  assertion is used.

- bpo-40275: The :mod:`asyncio` package is now imported lazily in
  :mod:`unittest` only when the :class:`~unittest.IsolatedAsyncioTestCase`
  class is used.

- bpo-40330: In :meth:`ShareableList.__setitem__`, check the size of a new
  string item after encoding it to utf-8, not before.

- bpo-40148: Added :meth:`pathlib.Path.with_stem()` to create a new Path
  with the stem replaced.

- bpo-40325: Deprecated support for set objects in random.sample().

- bpo-40257: Improved help for the :mod:`typing` module. Docstrings are now
  shown for all special forms and special generic aliases (like ``Union``
  and ``List``). Using ``help()`` with generic alias like ``List[int]`` will
  show the help for the correspondent concrete type (``list`` in this case).

- bpo-40257: func:`inspect.getdoc` no longer returns docstring inherited
  from the type of the object or from parent class if it is a class if it is
  not defined in the object itself. In :mod:`pydoc` the documentation string
  is now shown not only for class, function, method etc, but for any object
  that has its own ``__doc__`` attribute.

- bpo-40287: Fixed ``SpooledTemporaryFile.seek()`` to return the position.

- bpo-40290: Added zscore() to statistics.NormalDist().

- bpo-40282: Allow ``random.getrandbits(0)`` to succeed and to return 0.

- bpo-40286: Add :func:`random.randbytes` function and
  :meth:`random.Random.randbytes` method to generate random bytes.

- bpo-40277: :func:`collections.namedtuple` now provides a human-readable
  repr for its field accessors.

- bpo-40270: The included copy of sqlite3 on Windows is now compiled with
  the json extension. This allows the use of functions such as
  ``json_object``.

- bpo-29255: Wait in `KqueueSelector.select` when no fds are registered

- bpo-40260: Ensure :mod:`modulefinder` uses :func:`io.open_code` and
  respects coding comments.

- bpo-40234: Allow again to spawn daemon threads in subinterpreters (revert
  change which denied them).

- bpo-39207: Workers in :class:`~concurrent.futures.ProcessPoolExecutor` are
  now spawned on demand, only when there are no available idle workers to
  reuse. This optimizes startup overhead and reduces the amount of lost CPU
  time to idle workers. Patch by Kyle Stanley.

- bpo-40091: Fix a hang at fork in the logging module: the new private
  _at_fork_reinit() method is now used to reinitialize locks at fork in the
  child process.

- bpo-40149: Implement traverse and clear slots in _abc._abc_data type.

- bpo-40208: Remove deprecated :meth:`symtable.SymbolTable.has_exec`.

- bpo-40196: Fix a bug in the :mod:`symtable` module that was causing
  incorrectly report global variables as local. Patch by Pablo Galindo.

- bpo-40190: Add support for ``_SC_AIX_REALMEM`` to :func:`posix.sysconf`.

- bpo-40182: Removed the ``_field_types`` attribute of the
  :class:`typing.NamedTuple` class.

- bpo-36517: Multiple inheritance with :class:`typing.NamedTuple` now raises
  an error instead of silently ignoring other types.

- bpo-40126: Fixed reverting multiple patches in unittest.mock. Patcher's
  ``__exit__()`` is now never called if its ``__enter__()`` is failed.
  Returning true from ``__exit__()`` silences now the exception.

- bpo-40094: CGIHTTPRequestHandler of http.server now logs the CGI script
  exit code, rather than the CGI script exit status of os.waitpid(). For
  example, if the script is killed by signal 11, it now logs: "CGI script
  exit code -11."

- bpo-40108: Improve the error message when triying to import a module using
  :mod:`runpy` and incorrently use the ".py" extension at the end of the
  module name. Patch by Pablo Galindo.

- bpo-40094: Add :func:`os.waitstatus_to_exitcode` function: convert a wait
  status to an exit code.

- bpo-40089: Fix threading._after_fork(): if fork was not called by a thread
  spawned by threading.Thread, threading._after_fork() now creates a
  _MainThread instance for _main_thread, instead of a _DummyThread instance.

- bpo-40089: Add a private ``_at_fork_reinit()`` method to
  :class:`_thread.Lock`, :class:`_thread.RLock`, :class:`threading.RLock`
  and :class:`threading.Condition` classes: reinitialize the lock at fork in
  the child process, reset the lock to the unlocked state. Rename also the
  private ``_reset_internal_locks()`` method of :class:`threading.Event` to
  ``_at_fork_reinit()``.

- bpo-25780: Expose :data:`~socket.CAN_RAW_JOIN_FILTERS` in the
  :mod:`socket` module.

- bpo-39503: :class:`~urllib.request.AbstractBasicAuthHandler` of
  :mod:`urllib.request` now parses all WWW-Authenticate HTTP headers and
  accepts multiple challenges per header: use the realm of the first Basic
  challenge.

- bpo-39812: Removed daemon threads from :mod:`concurrent.futures` by adding
  an internal `threading._register_atexit()`, which calls registered
  functions prior to joining all non-daemon threads. This allows for
  compatibility with subinterpreters, which don't support daemon threads.

- bpo-40050: Fix ``importlib._bootstrap_external``: avoid creating a new
  ``winreg`` builtin module if it's already available in
  :data:`sys.modules`, and remove redundant imports.

- bpo-40014: Fix ``os.getgrouplist()``: if ``getgrouplist()`` function fails
  because the group list is too small, retry with a larger group list. On
  failure, the glibc implementation of ``getgrouplist()`` sets ``ngroups``
  to the total number of groups. For other implementations, double the group
  list size.

- bpo-40017: Add :data:`time.CLOCK_TAI` constant if the operating system
  support it.

- bpo-40016: In re docstring, clarify the relationship between inline and
  argument compile flags.

- bpo-39953: Update internal table of OpenSSL error codes in the ``ssl``
  module.

- bpo-36144: Added :pep:`584` operators to
  :class:`weakref.WeakValueDictionary`.

- bpo-36144: Added :pep:`584` operators to
  :class:`weakref.WeakKeyDictionary`.

- bpo-38891: Fix linear runtime behaviour of the `__getitem__` and
  `__setitem__` methods in
  :class:`multiprocessing.shared_memory.ShareableList`. This avoids
  quadratic performance when iterating a `ShareableList`. Patch by Thomas
  Krennwallner.

- bpo-39682: Remove undocumented support for *closing* a `pathlib.Path`
  object via its context manager. The context manager magic methods remain,
  but they are now a no-op, making `Path` objects immutable.

- bpo-36144: Added :pep:`584` operators (``|`` and ``|=``) to
  :class:`collections.ChainMap`.

- bpo-39011: Normalization of line endings in ElementTree attributes was
  removed, as line endings which were replaced by entity numbers should be
  preserved in original form.

- bpo-38410: Properly handle :func:`sys.audit` failures in
  :func:`sys.set_asyncgen_hooks`.

- bpo-36541: lib2to3 now recognizes named assignment expressions (the walrus
  operator, ``:=``)

- bpo-35967: In platform, delay the invocation of 'uname -p' until the
  processor attribute is requested.

- bpo-35113: :meth:`inspect.getsource` now returns correct source code for
  inner class with same name as module level class. Decorators are also
  returned as part of source of the class. Patch by Karthikeyan
  Singaravelan.

- bpo-33262: Deprecate passing None as an argument for
  :func:`shlex.split()`'s ``s`` parameter.  Patch by Zackery Spytz.

- bpo-31758: Prevent crashes when using an uninitialized
  ``_elementtree.XMLParser`` object. Patch by Oren Milman.

Documentation
-------------

- bpo-27635: The pickle documentation incorrectly claimed that ``__new__``
  isn't called by default when unpickling.

- bpo-39879: Updated :ref:`datamodel` docs to include :func:`dict` insertion
  order preservation. Patch by Furkan Onder and Samy Lahfa.

- bpo-38387: Document :c:macro:`PyDoc_STRVAR` macro in the C-API reference.

- bpo-13743: Some methods within xml.dom.minidom.Element class are now
  better documented.

Tests
-----

- bpo-31904: Set expected default encoding in test_c_locale_coercion.py for
  VxWorks RTOS.

- bpo-40162: Update Travis CI configuration to OpenSSL 1.1.1f.

- bpo-40146: Update OpenSSL to 1.1.1f in Azure Pipelines.

- bpo-40094: Add :func:`test.support.wait_process` function.

- bpo-40003: ``test.bisect_cmd`` now copies Python command line options like
  ``-O`` or ``-W``. Moreover, emit a warning if ``test.bisect_cmd`` is used
  with ``-w``/``--verbose2`` option.

- bpo-39380: Add the encoding in :class:`ftplib.FTP` and
  :class:`ftplib.FTP_TLS` to the constructor as keyword-only and change the
  default from ``latin-1`` to ``utf-8`` to follow :rfc:`2640`.

- bpo-39793: Use the same domain when testing ``make_msgid``. Patch by
  Batuhan Taskaya.

- bpo-1812: Fix newline handling in doctest.testfile when loading from a
  package whose loader has a get_data method. Patch by Peter Donis.

Build
-----

- bpo-38360: Support single-argument form of macOS -isysroot flag.

- bpo-40158: Fix CPython MSBuild Properties in NuGet Package
  (build/native/python.props)

- bpo-38527: Fix configure check on Solaris for "float word ordering":
  sometimes, the correct "grep" command was not being used. Patch by Arnon
  Yaari.

Windows
-------

- bpo-40164: Updates Windows to OpenSSL 1.1.1f

- bpo-8901: Ignore the Windows registry when the ``-E`` option is used.

macOS
-----

- bpo-38329: python.org macOS installers now update the Current version
  symlink of /Library/Frameworks/Python.framework/Versions for 3.9 installs.
  Previously, Current was only updated for Python 2.x installs. This should
  make it easier to embed Python 3 into other macOS applications.

- bpo-40164: Update macOS installer builds to use OpenSSL 1.1.1g.

IDLE
----

- bpo-38439: Add a 256×256 pixel IDLE icon to support more modern
  environments. Created by Andrew Clover. Delete the unused macOS idle.icns
  icon file.

- bpo-38689: IDLE will no longer freeze when inspect.signature fails when
  fetching a calltip.

Tools/Demos
-----------

- bpo-40385: Removed the checkpyc.py tool. Please see compileall without
  force mode as a potential alternative.

- bpo-40179: Fixed translation of ``#elif`` in Argument Clinic.

- bpo-40094: Fix ``which.py`` script exit code: it now uses
  :func:`os.waitstatus_to_exitcode` to convert :func:`os.system` exit status
  into an exit code.

C API
-----

- bpo-40241: Move the :c:type:`PyGC_Head` structure to the internal C API.

- bpo-40170: Convert :c:func:`PyObject_IS_GC` macro to a function to hide
  implementation details.

- bpo-40241: Add the functions :c:func:`PyObject_GC_IsTracked` and
  :c:func:`PyObject_GC_IsFinalized` to the public API to allow to query if
  Python objects are being currently tracked or have been already finalized
  by the garbage collector respectively. Patch by Pablo Galindo.

- bpo-40170: The :c:func:`PyObject_NEW` macro becomes an alias to the
  :c:func:`PyObject_New` macro, and the :c:func:`PyObject_NEW_VAR` macro
  becomes an alias to the :c:func:`PyObject_NewVar` macro, to hide
  implementation details. They no longer access directly the
  :c:member:`PyTypeObject.tp_basicsize` member.

- bpo-40170: :c:func:`PyType_HasFeature` now always calls
  :c:func:`PyType_GetFlags` to hide implementation details. Previously, it
  accessed directly the :c:member:`PyTypeObject.tp_flags` member when the
  limited C API was not used.

- bpo-40170: Convert the :c:func:`PyObject_GET_WEAKREFS_LISTPTR` macro to a
  function to hide implementation details: the macro accessed directly to
  the :c:member:`PyTypeObject.tp_weaklistoffset` member.

- bpo-40170: Convert :c:func:`PyObject_CheckBuffer` macro to a function to
  hide implementation details: the macro accessed directly the
  :c:member:`PyTypeObject.tp_as_buffer` member.

- bpo-40170: Always declare :c:func:`PyIndex_Check` as an opaque function to
  hide implementation details: remove ``PyIndex_Check()`` macro. The macro
  accessed directly the :c:member:`PyTypeObject.tp_as_number` member.

- bpo-39947: Add :c:func:`PyThreadState_GetID` function: get the unique
  identifier of a Python thread state.


What's New in Python 3.9.0 alpha 5?
===================================

*Release date: 2020-03-23*

Security
--------

- bpo-38576: Disallow control characters in hostnames in http.client,
  addressing CVE-2019-18348. Such potentially malicious header injection
  URLs now cause a InvalidURL to be raised.

Core and Builtins
-----------------

- bpo-40010: Optimize pending calls in multithreaded applications. If a
  thread different than the main thread schedules a pending call
  (:c:func:`Py_AddPendingCall`), the bytecode evaluation loop is no longer
  interrupted at each bytecode instruction to check for pending calls which
  cannot be executed. Only the main thread can execute pending calls.

  Previously, the bytecode evaluation loop was interrupted at each
  instruction until the main thread executes pending calls.

- bpo-1635741: Port _weakref extension module to multiphase initialization
  (:pep:`489`).

- bpo-1635741: Port _collections module to multiphase initialization
  (:pep:`489`).

- bpo-40010: Optimize signal handling in multithreaded applications. If a
  thread different than the main thread gets a signal, the bytecode
  evaluation loop is no longer interrupted at each bytecode instruction to
  check for pending signals which cannot be handled. Only the main thread of
  the main interpreter can handle signals.

  Previously, the bytecode evaluation loop was interrupted at each
  instruction until the main thread handles signals.

- bpo-39984: If :c:func:`Py_AddPendingCall` is called in a subinterpreter,
  the function is now scheduled to be called from the subinterpreter, rather
  than being called from the main interpreter. Each subinterpreter now has
  its own list of scheduled calls.

- bpo-1635741: Port _heapq module to multiphase initialization.

- bpo-1635741: Port itertools module to multiphase initialization
  (:pep:`489`).

- bpo-37207: Speed up calls to ``frozenset()`` by using the :pep:`590`
  ``vectorcall`` calling convention. Patch by Dong-hee Na.

- bpo-39984: subinterpreters: Move
  ``_PyRuntimeState.ceval.tracing_possible`` to
  ``PyInterpreterState.ceval.tracing_possible``: each interpreter now has
  its own variable.

- bpo-37207: Speed up calls to ``set()`` by using the :pep:`590`
  ``vectorcall`` calling convention. Patch by Dong-hee Na.

- bpo-1635741: Port _statistics module to multiphase initialization
  (:pep:`489`).

- bpo-39968: Use inline function to replace extension modules'
  get_module_state macros.

- bpo-39965: Correctly raise ``SyntaxError`` if *await* is used inside
  non-async functions and ``PyCF_ALLOW_TOP_LEVEL_AWAIT`` is set (like in the
  asyncio REPL). Patch by Pablo Galindo.

- bpo-39562: Allow executing asynchronous comprehensions on the top level
  when the ``PyCF_ALLOW_TOP_LEVEL_AWAIT`` flag is given. Patch by Batuhan
  Taskaya.

- bpo-37207: Speed up calls to ``tuple()`` by using the :pep:`590`
  ``vectorcall`` calling convention. Patch by Dong-hee Na.

- bpo-38373: Changed list overallocation strategy. It no longer
  overallocates if the new size is closer to overallocated size than to the
  old size and adds padding.

- bpo-39926: Update Unicode database to Unicode version 13.0.0.

- bpo-19466: Clear the frames of daemon threads earlier during the Python
  shutdown to call objects destructors. So "unclosed file" resource warnings
  are now emitted for daemon threads in a more reliable way.

- bpo-38894: Fix a bug that was causing incomplete results when calling
  ``pathlib.Path.glob`` in the presence of symlinks that point to files
  where the user does not have read access. Patch by Pablo Galindo and Matt
  Wozniski.

- bpo-39877: Fix :c:func:`PyEval_RestoreThread` random crash at exit with
  daemon threads. It now accesses the ``_PyRuntime`` variable directly
  instead of using ``tstate->interp->runtime``, since ``tstate`` can be a
  dangling pointer after :c:func:`Py_Finalize` has been called. Moreover,
  the daemon thread now exits before trying to take the GIL.

- bpo-39871: Fix a possible :exc:`SystemError` in
  ``math.{atan2,copysign,remainder}()`` when the first argument cannot be
  converted to a :class:`float`. Patch by Zackery Spytz.

- bpo-39776: Fix race condition where threads created by PyGILState_Ensure()
  could get a duplicate id.

  This affects consumers of tstate->id like the contextvar caching
  machinery, which could return invalid cached objects under heavy thread
  load (observed in embedded scenarios).

- bpo-39778: Fixed a crash due to incorrect handling of weak references in
  ``collections.OrderedDict`` classes. Patch by Pablo Galindo.

- bpo-1635741: Port audioop extension module to multiphase initialization
  (:pep:`489`).

- bpo-39702: Relax :term:`decorator` grammar restrictions to allow any valid
  expression (:pep:`614`).

- bpo-38091: Tweak import deadlock detection code to not deadlock itself.

- bpo-1635741: Port _locale extension module to multiphase initialization
  (:pep:`489`).

- bpo-39087: Optimize :c:func:`PyUnicode_AsUTF8` and
  :c:func:`PyUnicode_AsUTF8AndSize` slightly when they need to create
  internal UTF-8 cache.

- bpo-39520: Fix unparsing of ext slices with no items (``foo[:,]``). Patch
  by Batuhan Taskaya.

- bpo-39220: Do not optimize annotations if 'from __future__ import
  annotations' is used. Patch by Pablo Galindo.

- bpo-35712: Using :data:`NotImplemented` in a boolean context has been
  deprecated. Patch contributed by Josh Rosenberg.

- bpo-22490: Don't leak environment variable ``__PYVENV_LAUNCHER__`` into
  the interpreter session on macOS.

Library
-------

- bpo-39830: Add :class:`zipfile.Path` to ``__all__`` in the :mod:`zipfile`
  module.

- bpo-40000: Improved error messages for validation of ``ast.Constant``
  nodes. Patch by Batuhan Taskaya.

- bpo-39999: ``__module__`` of the AST node classes is now set to "ast"
  instead of "_ast". Added docstrings for dummy AST node classes and
  deprecated attributes.

- bpo-39991: :func:`uuid.getnode` now skips IPv6 addresses with the same
  string length than a MAC address (17 characters): only use MAC addresses.

- bpo-39988: Deprecated ``ast.AugLoad`` and ``ast.AugStore`` node classes
  because they are no longer used.

- bpo-39656: Ensure ``bin/python3.#`` is always present in virtual
  environments on POSIX platforms - by Anthony Sottile.

- bpo-39969: Deprecated ``ast.Param`` node class because it's no longer
  used. Patch by Batuhan Taskaya.

- bpo-39360: Ensure all workers exit when finalizing a
  :class:`multiprocessing.Pool` implicitly via the module finalization
  handlers of multiprocessing. This fixes a deadlock situation that can be
  experienced when the Pool is not properly finalized via the context
  manager or a call to ``multiprocessing.Pool.terminate``. Patch by Batuhan
  Taskaya and Pablo Galindo.

- bpo-35370: sys.settrace(), sys.setprofile() and _lsprof.Profiler.enable()
  now properly report :c:func:`PySys_Audit` error if "sys.setprofile" or
  "sys.settrace" audit event is denied.

- bpo-39936: AIX: Fix _aix_support module when the subprocess is not
  available, when building Python from scratch. It now uses new private
  _bootsubprocess module, rather than having two implementations depending
  if subprocess is available or not. So _aix_support.aix_platform() result
  is now the same if subprocess is available or not.

- bpo-36144: :class:`collections.OrderedDict` now implements ``|`` and
  ``|=`` (:pep:`584`).

- bpo-39652: The column name found in ``sqlite3.Cursor.description`` is now
  truncated on the first '[' only if the PARSE_COLNAMES option is set.

- bpo-39915: Ensure :attr:`unittest.mock.AsyncMock.await_args_list` has call
  objects in the order of awaited arguments instead of using
  :attr:`unittest.mock.Mock.call_args` which has the last value of the call.
  Patch by Karthikeyan Singaravelan.

- bpo-36144: Updated :data:`os.environ` and :data:`os.environb` to support
  :pep:`584`'s merge (``|``) and update (``|=``) operators.

- bpo-38662: The ``ensurepip`` module now invokes ``pip`` via the ``runpy``
  module. Hence it is no longer tightly coupled with the internal API of the
  bundled ``pip`` version, allowing easier updates to a newer ``pip``
  version both internally and for distributors.

- bpo-38075: Fix the :meth:`random.Random.seed` method when a :class:`bool`
  is passed as the seed.

- bpo-39916: More reliable use of ``os.scandir()`` in ``Path.glob()``. It no
  longer emits a ResourceWarning when interrupted.

- bpo-39850: :mod:`multiprocessing` now supports abstract socket addresses
  (if abstract sockets are supported in the running platform). When creating
  arbitrary addresses (like when default-constructing
  :class:`multiprocessing.connection.Listener` objects) abstract sockets are
  preferred to avoid the case when the temporary-file-generated address is
  too large for an AF_UNIX socket address. Patch by Pablo Galindo.

- bpo-36287: :func:`ast.dump()` no longer outputs optional fields and
  attributes with default values. The default values for optional fields and
  attributes of AST nodes are now set as class attributes (e.g.
  ``Constant.kind`` is set to ``None``).

- bpo-39889: Fixed :func:`ast.unparse` for extended slices containing a
  single element (e.g. ``a[i:j,]``). Remove redundant tuples when index with
  a tuple (e.g. ``a[i, j]``).

- bpo-39828: Fix :mod:`json.tool` to catch :exc:`BrokenPipeError`. Patch by
  Dong-hee Na.

- bpo-13487: Avoid a possible *"RuntimeError: dictionary changed size during
  iteration"* from :func:`inspect.getmodule` when it tried to loop through
  :attr:`sys.modules`.

- bpo-39674: Revert "bpo-37330: open() no longer accept 'U' in file mode".
  The "U" mode of open() is kept in Python 3.9 to ease transition from
  Python 2.7, but will be removed in Python 3.10.

- bpo-28577: The hosts method on 32-bit prefix length IPv4Networks and
  128-bit prefix IPv6Networks now returns a list containing the single
  Address instead of an empty list.

- bpo-39826: Add getConnection method to logging HTTPHandler to enable
  custom connections.

- bpo-39763: Reimplement :func:`distutils.spawn.spawn` function with the
  :mod:`subprocess` module.

- bpo-39794: Add --without-decimal-contextvar build option.  This enables a
  thread-local rather than a coroutine local context.

- bpo-36144: :class:`collections.defaultdict` now implements ``|``
  (:pep:`584`).

- bpo-39517: Fix runpy.run_path() when using pathlike objects

- bpo-39775: Change ``inspect.Signature.parameters`` back to
  ``collections.OrderedDict``. This was changed to ``dict`` in Python
  3.9.0a4.

- bpo-39678: Refactor queue_manager in
  :class:`concurrent.futures.ProcessPoolExecutor` to make it easier to
  maintain.

- bpo-39764: Fix AttributeError when calling get_stack on a PyAsyncGenObject
  Task

- bpo-39769: The :func:`compileall.compile_dir` function's *ddir* parameter
  and the compileall command line flag `-d` no longer write the wrong
  pathname to the generated pyc file for submodules beneath the root of the
  directory tree being compiled.  This fixes a regression introduced with
  Python 3.5.

- bpo-36144: :class:`types.MappingProxyType` objects now support the merge
  (``|``) operator from :pep:`584`.

- bpo-38691: The :mod:`importlib` module now ignores the
  :envvar:`PYTHONCASEOK` environment variable when the :option:`-E` or
  :option:`-I` command line options are being used.

- bpo-39719: Remove :meth:`tempfile.SpooledTemporaryFile.softspace` as files
  no longer have the ``softspace`` attribute in Python 3. Patch by Shantanu.

- bpo-39667: Improve pathlib.Path compatibility on zipfile.Path and correct
  performance degradation as found in zipp 3.0.

- bpo-39638: Keep ASDL signatures in the docstrings for ``AST`` nodes. Patch
  by Batuhan Taskaya

- bpo-39639: Deprecated ``ast.Suite`` node class because it's no longer
  used. Patch by Batuhan Taskaya.

- bpo-39609: Add thread_name_prefix to default asyncio executor

- bpo-39548: Fix handling of header in
  :class:`urllib.request.AbstractDigestAuthHandler` when the optional
  ``qop`` parameter is not present.

- bpo-39509: HTTP status codes ``103 EARLY_HINTS`` and ``425 TOO_EARLY`` are
  added to :class:`http.HTTPStatus`. Patch by Dong-hee Na.

- bpo-39507: Adding HTTP status 418 "I'm a Teapot" to HTTPStatus in http
  library. Patch by Ross Rhodes.

- bpo-39495: Remove default value from *attrs* parameter of
  :meth:`xml.etree.ElementTree.TreeBuilder.start` for consistency between
  Python and C implementations.

- bpo-38971: Open issue in the BPO indicated a desire to make the
  implementation of codecs.open() at parity with io.open(), which implements
  a try/except to assure file stream gets closed before an exception is
  raised.

- bpo-38641: Added starred expressions support to ``return`` and ``yield``
  statements for ``lib2to3``. Patch by Vlad Emelianov.

- bpo-37534: When using minidom module to generate XML documents the ability
  to add Standalone Document Declaration is added. All the changes are made
  to generate a document in compliance with Extensible Markup Language (XML)
  1.0 (Fifth Edition) W3C Recommendation (available here:
  https://www.w3.org/TR/xml/#sec-prolog-dtd).

- bpo-34788: Add support for scoped IPv6 addresses to :mod:`ipaddress`.
  Patch by Oleksandr Pavliuk.

- bpo-34822: Simplified AST for subscription. Simple indices are now
  represented by their value, extended slices are represented as tuples.
  :mod:`ast` classes ``Index`` and ``ExtSlice`` are considered deprecated
  and will be removed in future Python versions. In the meantime,
  ``Index(value)`` now returns a ``value`` itself, ``ExtSlice(slices)``
  returns ``Tuple(slices, Load())``.

Documentation
-------------

- bpo-39868: Updated the Language Reference for :pep:`572`.

- bpo-13790: Change 'string' to 'specification' in format doc.

- bpo-17422: The language reference no longer restricts default class
  namespaces to dicts only.

- bpo-39530: Fix misleading documentation about mixed-type numeric
  comparisons.

- bpo-39718: Update :mod:`token` documentation to reflect additions in
  Python 3.8

- bpo-39677: Changed operand name of **MAKE_FUNCTION** from *argc* to
  *flags* for module :mod:`dis`

Tests
-----

- bpo-40019: test_gdb now skips tests if it detects that gdb failed to read
  debug information because the Python binary is optimized.

- bpo-27807: ``test_site.test_startup_imports()`` is now skipped if a path
  of :data:`sys.path` contains a ``.pth`` file.

- bpo-26067: Do not fail test_shutil test_chown test when uid or gid of user
  cannot be resolved to a name.

- bpo-39855: test_subprocess.test_user() now skips the test on an user name
  if the user name doesn't exist. For example, skip the test if the user
  "nobody" doesn't exist on Linux.

Build
-----

- bpo-39761: Fix build with DTrace but without additional DFLAGS.

- bpo-39763: setup.py now uses a basic implementation of the
  :mod:`subprocess` module if the :mod:`subprocess` module is not available:
  before required C extension modules are built.

- bpo-1294959: Add ``--with-platlibdir`` option to the configure script:
  name of the platform-specific library directory, stored in the new
  :attr:`sys.platlibdir` attribute. It is used to build the path of
  platform-specific extension modules and the path of the standard library.
  It is equal to ``"lib"`` on most platforms. On Fedora and SuSE, it is
  equal to ``"lib64"`` on 64-bit platforms. Patch by Jan Matějek, Matěj
  Cepl, Charalampos Stratakis and Victor Stinner.

Windows
-------

- bpo-39930: Ensures the required :file:`vcruntime140.dll` is included in
  install packages.

- bpo-39847: Avoid hang when computer is hibernated whilst waiting for a
  mutex (for lock-related objects from :mod:`threading`) around 49-day
  uptime.

- bpo-38597: :mod:`distutils` will no longer statically link
  :file:`vcruntime140.dll` when a redistributable version is unavailable.
  All future releases of CPython will include a copy of this DLL to ensure
  distributed extensions can continue to load.

- bpo-38380: Update Windows builds to use SQLite 3.31.1

- bpo-39789: Update Windows release build machines to Visual Studio 2019
  (MSVC 14.2).

- bpo-34803: Package for nuget.org now includes repository reference and
  bundled icon image.

macOS
-----

- bpo-38380: Update macOS builds to use SQLite 3.31.1

IDLE
----

- bpo-27115: For 'Go to Line', use a Query box subclass with IDLE standard
  behavior and improved error checking.

- bpo-39885: Since clicking to get an IDLE context menu moves the cursor,
  any text selection should be and now is cleared.

- bpo-39852: Edit "Go to line" now clears any selection, preventing
  accidental deletion. It also updates Ln and Col on the status bar.

- bpo-39781: Selecting code context lines no longer causes a jump.

Tools/Demos
-----------

- bpo-36184: Port python-gdb.py to FreeBSD. python-gdb.py now checks for
  "take_gil" function name to check if a frame tries to acquire the GIL,
  instead of checking for "pthread_cond_timedwait" which is specific to
  Linux and can be a different condition than the GIL.

- bpo-38080: Added support to fix ``getproxies`` in the
  :mod:`lib2to3.fixes.fix_urllib` module. Patch by José Roberto Meza
  Cabrera.

C API
-----

- bpo-40024: Add :c:func:`PyModule_AddType` helper function: add a type to a
  module. Patch by Dong-hee Na.

- bpo-39946: Remove ``_PyRuntime.getframe`` hook and remove
  ``_PyThreadState_GetFrame`` macro which was an alias to
  ``_PyRuntime.getframe``. They were only exposed by the internal C API.
  Remove also ``PyThreadFrameGetter`` type.

- bpo-39947: Add :c:func:`PyThreadState_GetFrame` function: get the current
  frame of a Python thread state.

- bpo-37207: Add _PyArg_NoKwnames helper function. Patch by Dong-hee Na.

- bpo-39947: Add :c:func:`PyThreadState_GetInterpreter`: get the interpreter
  of a Python thread state.

- bpo-39947: Add :c:func:`PyInterpreterState_Get` function to the limited C
  API.

- bpo-35370: If :c:func:`PySys_Audit` fails in :c:func:`PyEval_SetProfile`
  or :c:func:`PyEval_SetTrace`, log the error as an unraisable exception.

- bpo-39947: Move the static inline function flavor of
  Py_EnterRecursiveCall() and Py_LeaveRecursiveCall() to the internal C API:
  they access PyThreadState attributes. The limited C API provides regular
  functions which hide implementation details.

- bpo-39947: Py_TRASHCAN_BEGIN_CONDITION and Py_TRASHCAN_END macro no longer
  access PyThreadState attributes, but call new private _PyTrash_begin() and
  _PyTrash_end() functions which hide implementation details.

- bpo-39884: :c:func:`PyDescr_NewMethod` and :c:func:`PyCFunction_NewEx` now
  include the method name in the SystemError "bad call flags" error message
  to ease debug.

- bpo-39877: Deprecated :c:func:`PyEval_InitThreads` and
  :c:func:`PyEval_ThreadsInitialized`. Calling :c:func:`PyEval_InitThreads`
  now does nothing.

- bpo-38249: :c:macro:`Py_UNREACHABLE` is now implemented with
  ``__builtin_unreachable()`` and analogs in release mode.

- bpo-38643: :c:func:`PyNumber_ToBase` now raises a :exc:`SystemError`
  instead of crashing when called with invalid base.

- bpo-39882: The :c:func:`Py_FatalError` function is replaced with a macro
  which logs automatically the name of the current function, unless the
  ``Py_LIMITED_API`` macro is defined.

- bpo-39824: Extension modules: :c:member:`~PyModuleDef.m_traverse`,
  :c:member:`~PyModuleDef.m_clear` and :c:member:`~PyModuleDef.m_free`
  functions of :c:type:`PyModuleDef` are no longer called if the module
  state was requested but is not allocated yet. This is the case immediately
  after the module is created and before the module is executed
  (:c:data:`Py_mod_exec` function). More precisely, these functions are not
  called if :c:member:`~PyModuleDef.m_size` is greater than 0 and the module
  state (as returned by :c:func:`PyModule_GetState`) is ``NULL``.

  Extension modules without module state (``m_size <= 0``) are not affected.

- bpo-38913: Fixed segfault in ``Py_BuildValue()`` called with a format
  containing "#" and undefined PY_SSIZE_T_CLEAN whwn an exception is set.

- bpo-38500: Add a private API to get and set the frame evaluation function:
  add :c:func:`_PyInterpreterState_GetEvalFrameFunc` and
  :c:func:`_PyInterpreterState_SetEvalFrameFunc` C functions. The
  :c:type:`_PyFrameEvalFunction` function type now takes a *tstate*
  parameter.


What's New in Python 3.9.0 alpha 4?
===================================

*Release date: 2020-02-25*

Security
--------

- bpo-39184: Add audit events to functions in `fcntl`, `msvcrt`, `os`,
  `resource`, `shutil`, `signal` and `syslog`.

- bpo-39401: Avoid unsafe DLL load at startup on Windows 7 and earlier.

- bpo-39184: Add audit events to command execution functions in os and pty
  modules.

Core and Builtins
-----------------

- bpo-39382: Fix a use-after-free in the single inheritance path of
  ``issubclass()``, when the ``__bases__`` of an object has a single
  reference, and so does its first item. Patch by Yonatan Goldschmidt.

- bpo-39573: Update clinic tool to use :c:func:`Py_IS_TYPE`. Patch by
  Dong-hee Na.

- bpo-39619: Enable use of :func:`os.chroot` on HP-UX systems.

- bpo-39573: Add :c:func:`Py_IS_TYPE` static inline function to check
  whether the object *o* type is *type*.

- bpo-39606: Fix regression caused by fix for bpo-39386, that prevented
  calling ``aclose`` on an async generator that had already been closed or
  exhausted.

- bpo-39579: Change the ending column offset of `Attribute` nodes
  constructed in `ast_for_dotted_name` to point at the end of the current
  node and not at the end of the last `NAME` node.

- bpo-1635741: Port _crypt extension module to multiphase initialization
  (:pep:`489`).

- bpo-1635741: Port _contextvars extension module to multiphase
  initialization (:pep:`489`).

- bpo-39510: Fix segfault in ``readinto()`` method on closed BufferedReader.

- bpo-39502: Fix :func:`time.localtime` on 64-bit AIX  to support years
  before 1902 and after 2038. Patch by M Felt.

- bpo-39492: Fix a reference cycle in the C Pickler that was preventing the
  garbage collection of deleted, pickled objects.

- bpo-39453: Fixed a possible crash in :meth:`list.__contains__` when a list
  is changed during comparing items. Patch by Dong-hee Na.

- bpo-39434: :term:`floor division` of float operation now has a better
  performance. Also the message of :exc:`ZeroDivisionError` for this
  operation is updated. Patch by Dong-hee Na.

- bpo-1635741: Port _codecs extension module to multiphase initialization
  (:pep:`489`).

- bpo-1635741: Port _bz2 extension module to multiphase initialization
  (:pep:`489`).

- bpo-1635741: Port _abc extension module to multiphase initialization
  (:pep:`489`).

- bpo-39320: Replace two complex bytecodes for building dicts with two
  simpler ones. The new bytecodes ``DICT_MERGE`` and ``DICT_UPDATE`` have
  been added The old bytecodes ``BUILD_MAP_UNPACK`` and
  ``BUILD_MAP_UNPACK_WITH_CALL`` have been removed.

- bpo-39219: Syntax errors raised in the tokenizer now always set correct
  "text" and "offset" attributes.

- bpo-36051: Drop the GIL during large ``bytes.join`` operations. Patch by
  Bruce Merry.

- bpo-38960: Fix DTrace build issues on FreeBSD. Patch by David Carlier.

- bpo-37207: Speed up calls to ``range()`` by about 30%, by using the PEP
  590 ``vectorcall`` calling convention. Patch by Mark Shannon.

- bpo-36144: :class:`dict` (and :class:`collections.UserDict`) objects now
  support PEP 584's merge (``|``) and update (``|=``) operators. Patch by
  Brandt Bucher.

- bpo-32856: Optimized the idiom for assignment a temporary variable in
  comprehensions. Now ``for y in [expr]`` in comprehensions is as fast as a
  simple assignment ``y = expr``.

Library
-------

- bpo-30566: Fix :exc:`IndexError` when trying to decode an invalid string
  with punycode codec.

- bpo-39649: Remove obsolete check for `__args__` in
  bdb.Bdb.format_stack_entry.

- bpo-39648: Expanded :func:`math.gcd` and :func:`math.lcm` to handle
  multiple arguments.

- bpo-39681: Fix a regression where the C pickle module wouldn't allow
  unpickling from a file-like object that doesn't expose a readinto()
  method.

- bpo-35950: Raise :exc:`io.UnsupportedOperation` in
  :meth:`io.BufferedReader.truncate` when it is called on a read-only
  :class:`io.BufferedReader` instance.

- bpo-39479: Add :func:`math.lcm` function: least common multiple.

- bpo-39674: Revert "Do not expose abstract collection classes in the
  collections module" change (bpo-25988). Aliases to ABC like
  collections.Mapping are kept in Python 3.9 to ease transition from Python
  2.7, but will be removed in Python 3.10.

- bpo-39104: Fix hanging ProcessPoolExcutor on ``shutdown(wait=False)`` when
  a task has failed pickling.

- bpo-39627: Fixed TypedDict totality check for inherited keys.

- bpo-39474: Fixed starting position of AST for expressions like ``(a)(b)``,
  ``(a)[b]`` and ``(a).b``.

- bpo-21016: The :mod:`pydoc` and :mod:`trace` modules now use the
  :mod:`sysconfig` module to get the path to the Python standard library, to
  support uncommon installation path like ``/usr/lib64/python3.9/`` on
  Fedora. Patch by Jan Matějek.

- bpo-39590: Collections.deque now holds strong references during
  deque.__contains__ and deque.count, fixing crashes.

- bpo-39586: The distutils ``bdist_msi`` command is deprecated in Python
  3.9, use ``bdist_wheel`` (wheel packages) instead.

- bpo-39595: Improved performance of zipfile.Path for files with a large
  number of entries. Also improved performance and fixed minor issue as
  published with `importlib_metadata 1.5
  <https://importlib-metadata.readthedocs.io/en/latest/changelog%20(links).html#v1-5-0>`_.

- bpo-39350: Fix regression in :class:`fractions.Fraction` if the numerator
  and/or the denominator is an :class:`int` subclass. The :func:`math.gcd`
  function is now used to normalize the *numerator* and *denominator*.
  :func:`math.gcd` always return a :class:`int` type. Previously, the GCD
  type depended on *numerator* and *denominator*.

- bpo-39567: Added audit for :func:`os.walk`, :func:`os.fwalk`,
  :meth:`pathlib.Path.glob` and :meth:`pathlib.Path.rglob`.

- bpo-39559: Remove unused, undocumented argument ``getters`` from
  :func:`uuid.getnode`

- bpo-38149: :func:`sys.audit` is now called only once per call of
  :func:`glob.glob` and :func:`glob.iglob`.

- bpo-39546: Fix a regression in :class:`~argparse.ArgumentParser` where
  ``allow_abbrev=False`` was ignored for long options that used a prefix
  character other than "-".

- bpo-39450: Striped whitespace from docstring before returning it from
  :func:`unittest.case.shortDescription`.

- bpo-12915: A new function ``resolve_name`` has been added to the
  ``pkgutil`` module. This resolves a string of the form ``'a.b.c.d'`` or
  ``'a.b:c.d'`` to an object. In the example, ``a.b`` is a package/module
  and ``c.d`` is an object within that package/module reached via recursive
  attribute access.

- bpo-39353: The :func:`binascii.crc_hqx` function is no longer deprecated.

- bpo-39493: Mark ``typing.IO.closed`` as a property

- bpo-39491: Add :data:`typing.Annotated` and ``include_extras`` parameter
  to :func:`typing.get_type_hints` as part of :pep:`593`. Patch by Till
  Varoquaux, documentation by Till Varoquaux and Konstantin Kashin.

- bpo-39485: Fix a bug in :func:`unittest.mock.create_autospec` that would
  complain about the wrong number of arguments for custom descriptors
  defined in an extension module returning functions.

- bpo-38932: Mock fully resets child objects on reset_mock(). Patch by
  Vegard Stikbakke

- bpo-39082: Allow AsyncMock to correctly patch static/class methods

- bpo-39432: Implement PEP-489 algorithm for non-ascii "PyInit\_..." symbol
  names in distutils to make it export the correct init symbol also on
  Windows.

- bpo-18819: Omit ``devmajor`` and ``devminor`` fields for non-device files
  in :mod:`tarfile` archives, enabling bit-for-bit compatibility with GNU
  ``tar(1)``.

- bpo-39349: Added a new *cancel_futures* parameter to
  :meth:`concurrent.futures.Executor.shutdown` that cancels all pending
  futures which have not started running, instead of waiting for them to
  complete before shutting down the executor.

- bpo-39274: ``bool(fraction.Fraction)`` now returns a boolean even if
  (numerator != 0) does not return a boolean (ex: numpy number).

- bpo-34793: Remove support for ``with (await asyncio.lock):`` and ``with
  (yield from asyncio.lock):``.  The same is correct for
  ``asyncio.Condition`` and ``asyncio.Semaphore``.

- bpo-25597: Ensure, if ``wraps`` is supplied to
  :class:`unittest.mock.MagicMock`, it is used to calculate return values
  for the magic methods instead of using the default return values. Patch by
  Karthikeyan Singaravelan.

- bpo-36350: `inspect.Signature.parameters` and
  `inspect.BoundArguments.arguments` are now dicts instead of OrderedDicts.
  Patch contributed by Rémi Lapeyre.

- bpo-35727: Fix sys.exit() and sys.exit(None) exit code propagation when
  used in multiprocessing.Process.

- bpo-32173: * Add `lazycache` function to `__all__`. * Use `dict.clear` to
  clear the cache. * Refactoring `getline` function and `checkcache`
  function.

Documentation
-------------

- bpo-17422: The language reference now specifies restrictions on class
  namespaces. Adapted from a patch by Ethan Furman.

- bpo-39572: Updated documentation of ``total`` flag of ``TypedDict``.

- bpo-39654: In pyclbr doc, update 'class' to 'module' where appropriate and
  add readmodule comment. Patch by Hakan Çelik.

- bpo-39153: Clarify refcounting semantics for the following functions: -
  PyObject_SetItem - PyMapping_SetItemString - PyDict_SetItem -
  PyDict_SetItemString

- bpo-39392: Explain that when filling with turtle, overlap regions may be
  left unfilled.

- bpo-39369: Update mmap readline method description. The fact that the
  readline method does update the file position should not be ignored since
  this might give the impression for the programmer that it doesn't update
  it.

- bpo-9056: Include subsection in TOC for PDF version of docs.

Tests
-----

- bpo-38325: Skip tests on non-BMP characters of test_winconsoleio.

- bpo-39502: Skip test_zipfile.test_add_file_after_2107() if
  :func:`time.localtime` fails with :exc:`OverflowError`. It is the case on
  AIX 6.1 for example.

Build
-----

- bpo-39489: Remove ``COUNT_ALLOCS`` special build.

Windows
-------

- bpo-39553: Delete unused code related to SxS manifests.

- bpo-39439: Honor the Python path when a virtualenv is active on Windows.

- bpo-39393: Improve the error message when attempting to load a DLL with
  unresolved dependencies.

- bpo-38883: :meth:`~pathlib.Path.home()` and
  :meth:`~pathlib.Path.expanduser()` on Windows now prefer
  :envvar:`USERPROFILE` and no longer use :envvar:`HOME`, which is not
  normally set for regular user accounts. This makes them again behave like
  :func:`os.path.expanduser`, which was changed to ignore :envvar:`HOME` in
  3.8, see :issue:`36264`.

- bpo-39185: The build.bat script has additional options for very-quiet
  output (-q) and very-verbose output (-vv)

IDLE
----

- bpo-39663: Add tests for pyparse find_good_parse_start().

- bpo-39600: In the font configuration window, remove duplicated font names.

- bpo-30780: Add remaining configdialog tests for buttons and highlights and
  keys tabs.

- bpo-39388: IDLE Settings Cancel button now cancels pending changes

- bpo-38792: Close an IDLE shell calltip if a :exc:`KeyboardInterrupt` or
  shell restart occurs.  Patch by Zackery Spytz.

C API
-----

- bpo-35081: Move the ``bytes_methods.h`` header file to the internal C API
  as ``pycore_bytes_methods.h``: it only contains private symbols (prefixed
  by ``_Py``), except of the ``PyDoc_STRVAR_shared()`` macro.

- bpo-35081: Move the ``dtoa.h`` header file to the internal C API as
  ``pycore_dtoa.h``: it only contains private functions (prefixed by
  ``_Py``). The :mod:`math` and :mod:`cmath` modules must now be compiled
  with the ``Py_BUILD_CORE`` macro defined.

- bpo-39573: Add :c:func:`Py_SET_SIZE` function to set the size of an
  object.

- bpo-39500: :c:func:`PyUnicode_IsIdentifier` does not call
  :c:func:`Py_FatalError` anymore if the string is not ready.

- bpo-39573: Add :c:func:`Py_SET_TYPE` function to set the type of an
  object.

- bpo-39573: Add a :c:func:`Py_SET_REFCNT` function to set the reference
  counter of an object.

- bpo-39542: Convert :c:func:`PyType_HasFeature`, :c:func:`PyType_Check` and
  :c:func:`PyType_CheckExact` macros to static inline functions.

- bpo-39542: In the limited C API, ``PyObject_INIT()`` and
  ``PyObject_INIT_VAR()`` are now defined as aliases to
  :c:func:`PyObject_Init` and :c:func:`PyObject_InitVar` to make their
  implementation opaque. It avoids to leak implementation details in the
  limited C API. Exclude the following functions from the limited C API:
  ``_Py_NewReference()``, ``_Py_ForgetReference()``,
  ``_PyTraceMalloc_NewReference()`` and ``_Py_GetRefTotal()``.

- bpo-39542: Exclude trashcan mechanism from the limited C API: it requires
  access to PyTypeObject and PyThreadState structure fields, whereas these
  structures are opaque in the limited C API.

- bpo-39511: The :c:func:`PyThreadState_Clear` function now calls the
  :c:member:`PyThreadState.on_delete` callback. Previously, that happened in
  :c:func:`PyThreadState_Delete`.

- bpo-38076: Fix to clear the interpreter state only after clearing module
  globals to guarantee module state access from C Extensions during runtime
  destruction

- bpo-39245: The Vectorcall API (PEP 590) was made public, adding the
  functions ``PyObject_Vectorcall``, ``PyObject_VectorcallMethod``,
  ``PyVectorcall_Function``, ``PyObject_CallOneArg``,
  ``PyObject_CallMethodNoArgs``, ``PyObject_CallMethodOneArg``,
  ``PyObject_FastCallDict``, and the flag ``Py_TPFLAGS_HAVE_VECTORCALL``.


What's New in Python 3.9.0 alpha 3?
===================================

*Release date: 2020-01-24*

Core and Builtins
-----------------

- bpo-39427: Document all possibilities for the ``-X`` options in the
  command line help section. Patch by Pablo Galindo.

- bpo-39421: Fix possible crashes when operating with the functions in the
  :mod:`heapq` module and custom comparison operators.

- bpo-39386: Prevent double awaiting of async iterator.

- bpo-17005: Add :class:`functools.TopologicalSorter` to the
  :mod:`functools` module to offers functionality to perform topological
  sorting of graphs. Patch by Pablo Galindo, Tim Peters and Larry Hastings.

- bpo-39320: Replace four complex bytecodes for building sequences with
  three simpler ones.

  The following four bytecodes have been removed:

  * BUILD_LIST_UNPACK
  * BUILD_TUPLE_UNPACK
  * BUILD_SET_UNPACK
  * BUILD_TUPLE_UNPACK_WITH_CALL

  The following three bytecodes have been added:

  * LIST_TO_TUPLE
  * LIST_EXTEND
  * SET_UPDATE

- bpo-39336: Import loaders which publish immutable module objects can now
  publish immutable packages in addition to individual modules.

- bpo-39322: Added a new function :func:`gc.is_finalized` to check if an
  object has been finalized by the garbage collector. Patch by Pablo
  Galindo.

- bpo-39048: Improve the displayed error message when incorrect types are
  passed to ``async with`` statements by looking up the :meth:`__aenter__`
  special method before the :meth:`__aexit__` special method when entering
  an asynchronous context manager. Patch by Géry Ogam.

- bpo-39235: Fix AST end location for lone generator expression in function
  call, e.g. f(i for i in a).

- bpo-39209: Correctly handle multi-line tokens in interactive mode. Patch
  by Pablo Galindo.

- bpo-1635741: Port _json extension module to multiphase initialization
  (:pep:`489`).

- bpo-39216: Fix constant folding optimization for positional only arguments
  - by Anthony Sottile.

- bpo-39215: Fix ``SystemError`` when nested function has annotation on
  positional-only argument - by Anthony Sottile.

- bpo-39200: Correct the error message when calling the :func:`min` or
  :func:`max` with no arguments. Patch by Dong-hee Na.

- bpo-39200: Correct the error message when trying to construct
  :class:`range` objects with no arguments. Patch by Pablo Galindo.

- bpo-39166: Fix incorrect line execution reporting in trace functions when
  tracing the last iteration of asynchronous for loops. Patch by Pablo
  Galindo.

- bpo-39114: Fix incorrect line execution reporting in trace functions when
  tracing exception handlers with name binding. Patch by Pablo Galindo.

- bpo-39156: Split the COMPARE_OP bytecode instruction into four distinct
  instructions.

  *  COMPARE_OP for rich comparisons
  *  IS_OP for 'is' and 'is not' tests
  *  CONTAINS_OP for 'in' and 'is not' tests
  *  JUMP_IF_NOT_EXC_MATCH for checking exceptions in 'try-except' statements.

  This improves the clarity of the interpreter and should provide a modest
  speedup.

- bpo-38588: Fix possible crashes in dict and list when calling
  :c:func:`PyObject_RichCompareBool`.

- bpo-13601: By default, ``sys.stderr`` is line-buffered now, even if
  ``stderr`` is redirected to a file. You can still make ``sys.stderr``
  unbuffered by passing the :option:`-u` command-line option or setting the
  :envvar:`PYTHONUNBUFFERED` environment variable.

  (Contributed by Jendrik Seipp in bpo-13601.)

- bpo-38610: Fix possible crashes in several list methods by holding strong
  references to list elements when calling
  :c:func:`PyObject_RichCompareBool`.

- bpo-32021: Include brotli .br encoding in mimetypes encodings_map

Library
-------

- bpo-39430: Fixed race condition in lazy imports in :mod:`tarfile`.

- bpo-39413: The :func:`os.unsetenv` function is now also available on
  Windows.

- bpo-39390: Fixed a regression with the `ignore` callback of
  :func:`shutil.copytree`. The argument types are now str and List[str]
  again.

- bpo-39395: The :func:`os.putenv` and :func:`os.unsetenv` functions are now
  always available.

- bpo-39406: If ``setenv()`` C function is available, :func:`os.putenv` is
  now implemented with ``setenv()`` instead of ``putenv()``, so Python
  doesn't have to handle the environment variable memory.

- bpo-39396: Fix ``math.nextafter(-0.0, +0.0)`` on AIX 7.1.

- bpo-29435: Allow :func:`tarfile.is_tarfile` to be used with file and
  file-like objects, like :func:`zipfile.is_zipfile`. Patch by William
  Woodruff.

- bpo-39377: Removed ``encoding`` option from :func:`json.loads`.  It has
  been deprecated since Python 3.1.

- bpo-39389: Write accurate compression level metadata in :mod:`gzip`
  archives, rather than always signaling maximum compression.

- bpo-39366: The previously deprecated ``xpath()`` and ``xgtitle()`` methods
  of :class:`nntplib.NNTP` have been removed.

- bpo-39357: Remove the *buffering* parameter of :class:`bz2.BZ2File`. Since
  Python 3.0, it was ignored and using it was emitting
  :exc:`DeprecationWarning`. Pass an open file object, to control how the
  file is opened. The *compresslevel* parameter becomes keyword-only.

- bpo-39353: Deprecate binhex4 and hexbin4 standards. Deprecate the
  :mod:`binhex` module and the following :mod:`binascii` functions:
  :func:`~binascii.b2a_hqx`, :func:`~binascii.a2b_hqx`,
  :func:`~binascii.rlecode_hqx`, :func:`~binascii.rledecode_hqx`,
  :func:`~binascii.crc_hqx`.

- bpo-39351: Remove ``base64.encodestring()`` and ``base64.decodestring()``,
  aliases deprecated since Python 3.1: use :func:`base64.encodebytes` and
  :func:`base64.decodebytes` instead.

- bpo-39350: Remove ``fractions.gcd()`` function, deprecated since Python
  3.5 (:issue:`22486`): use :func:`math.gcd` instead.

- bpo-39329: :class:`~smtplib.LMTP` constructor now has an optional
  *timeout* parameter. Patch by Dong-hee Na.

- bpo-39313: Add a new ``exec_function`` option (*--exec-function* in the
  CLI) to ``RefactoringTool`` for making ``exec`` a function. Patch by
  Batuhan Taskaya.

- bpo-39259: :class:`~ftplib.FTP_TLS` and :class:`~ftplib.FTP_TLS` now raise
  a :class:`ValueError` if the given timeout for their constructor is zero
  to prevent the creation of a non-blocking socket. Patch by Dong-hee Na.

- bpo-39259: :class:`~smtplib.SMTP` and :class:`~smtplib.SMTP_SSL` now raise
  a :class:`ValueError` if the given timeout for their constructor is zero
  to prevent the creation of a non-blocking socket. Patch by Dong-hee Na.

- bpo-39310: Add :func:`math.ulp`: return the value of the least significant
  bit of a float.

- bpo-39297: Improved performance of importlib.metadata distribution
  discovery and resilients to inaccessible sys.path entries
  (importlib_metadata v1.4.0).

- bpo-39259: :class:`~nntplib.NNTP` and :class:`~nntplib.NNTP_SSL` now raise
  a :class:`ValueError` if the given timeout for their constructor is zero
  to prevent the creation of a non-blocking socket. Patch by Dong-hee Na.

- bpo-38901: When you specify prompt='.' or equivalently python -m venv
  --prompt . ... the basename of the current directory is used to set the
  created venv's prompt when it's activated.

- bpo-39288: Add :func:`math.nextafter`: return the next floating-point
  value after *x* towards *y*.

- bpo-39259: :class:`~poplib.POP3` and :class:`~poplib.POP3_SSL` now raise a
  :class:`ValueError` if the given timeout for their constructor is zero to
  prevent the creation of a non-blocking socket. Patch by Dong-hee Na.

- bpo-39242: Updated the Gmane domain from news.gmane.org to news.gmane.io
  which is used for examples of :class:`~nntplib.NNTP` news reader server
  and nntplib tests.

- bpo-35292: Proxy the `SimpleHTTPRequestHandler.guess_type` to
  `mimetypes.guess_type` so the `mimetypes.init` is called lazily to avoid
  unnecessary costs when :mod:`http.server` module is imported.

- bpo-39239: The :meth:`select.epoll.unregister` method no longer ignores
  the :data:`~errno.EBADF` error.

- bpo-38907: In http.server script, restore binding to IPv4 on Windows.

- bpo-39152: Fix ttk.Scale.configure([name]) to return configuration tuple
  for name or all options.  Giovanni Lombardo contributed part of the patch.

- bpo-39198: If an exception were to be thrown in `Logger.isEnabledFor`
  (say, by asyncio timeouts or stopit) , the `logging` global lock may not
  be released appropriately, resulting in deadlock.  This change wraps that
  block of code with `try...finally` to ensure the lock is released.

- bpo-39191: Perform a check for running loop before starting a new task in
  ``loop.run_until_complete()`` to fail fast; it prevents the side effect of
  new task spawning before exception raising.

- bpo-38871: Correctly parenthesize filter-based statements that contain
  lambda expressions in mod:`lib2to3`. Patch by Dong-hee Na.

- bpo-39142: A change was made to logging.config.dictConfig to avoid
  converting instances of named tuples to ConvertingTuple. It's assumed that
  named tuples are too specialised to be treated like ordinary tuples; if a
  user of named tuples requires ConvertingTuple functionality, they will
  have to implement that themselves in their named tuple class.

- bpo-39158: ast.literal_eval() now supports empty sets.

- bpo-39129: Fix import path for ``asyncio.TimeoutError``

- bpo-39057: :func:`urllib.request.proxy_bypass_environment` now ignores
  leading dots and no longer ignores a trailing newline.

- bpo-39056: Fixed handling invalid warning category in the -W option.  No
  longer import the re module if it is not needed.

- bpo-39055: :func:`base64.b64decode` with ``validate=True`` raises now a
  binascii.Error if the input ends with a single ``\n``.

- bpo-21600: Fix :func:`mock.patch.stopall` to stop active patches that were
  created with :func:`mock.patch.dict`.

- bpo-39019: Implement dummy ``__class_getitem__`` for
  :class:`tempfile.SpooledTemporaryFile`.

- bpo-39019: Implement dummy ``__class_getitem__`` for ``subprocess.Popen``,
  ``subprocess.CompletedProcess``

- bpo-38914: Adjusted the wording of the warning issued by distutils'
  ``check`` command when the ``author`` and ``maintainer`` fields are
  supplied but no corresponding e-mail field (``author_email`` or
  ``maintainer_email``) is found. The wording now reflects the fact that
  these fields are suggested, but not required. Patch by Juergen Gmach.

- bpo-38878: Fixed __subclasshook__ of :class:`os.PathLike` to return a
  correct result upon inheritance. Patch by Bar Harel.

- bpo-38615: :class:`~imaplib.IMAP4` and :class:`~imaplib.IMAP4_SSL` now
  have an optional *timeout* parameter for their constructors. Also, the
  :meth:`~imaplib.IMAP4.open` method now has an optional *timeout* parameter
  with this change. The overridden methods of :class:`~imaplib.IMAP4_SSL`
  and :class:`~imaplib.IMAP4_stream` were applied to this change. Patch by
  Dong-hee Na.

- bpo-35182: Fixed :func:`Popen.communicate` subsequent call crash when the
  child process has already closed any piped standard stream, but still
  continues to be running. Patch by Andriy Maletsky.

- bpo-38630: On Unix, :meth:`subprocess.Popen.send_signal` now polls the
  process status. Polling reduces the risk of sending a signal to the wrong
  process if the process completed, the :attr:`subprocess.Popen.returncode`
  attribute is still ``None``, and the pid has been reassigned (recycled) to
  a new different process.

- bpo-38536: Removes trailing space in formatted currency with
  `international=True` and a locale with symbol following value. E.g.
  `locale.currency(12.34, international=True)` returned `'12,34 EUR '`
  instead of `'12,34 EUR'`.

- bpo-38473: Use signature from inner mock for autospecced methods attached
  with :func:`unittest.mock.attach_mock`. Patch by Karthikeyan Singaravelan.

- bpo-38361: Fixed an issue where ``ident`` could include a leading path
  separator when :func:`syslog.openlog` was called without arguments.

- bpo-38293: Add :func:`copy.copy` and :func:`copy.deepcopy` support to
  :func:`property` objects.

- bpo-37958: Added the pstats.Stats.get_profile_dict() method to return the
  profile data as a StatsProfile instance.

- bpo-28367: Termios magic constants for the following baud rates:   -
  B500000   - B576000   - B921600   - B1000000   - B1152000   - B1500000   -
  B2000000   - B2500000   - B3000000   - B3500000   - B4000000 Patch by
  Andrey Smirnov

Documentation
-------------

- bpo-39381: Mention in docs that :func:`asyncio.get_event_loop` implicitly
  creates new event loop only if called from the main thread.

- bpo-38918: Add an entry for ``__module__`` in the "function" & "method"
  sections of the `inspect docs types and members table
  <https://docs.python.org/3/library/inspect.html#types-and-members>`_

- bpo-3530: In the :mod:`ast` module documentation, fix a misleading
  ``NodeTransformer`` example and add advice on when to use the
  ``fix_missing_locations`` function.

Build
-----

- bpo-39395: On non-Windows platforms, the :c:func:`setenv` and
  :c:func:`unsetenv` functions are now required to build Python.

- bpo-39160: Updated the documentation in `./configure --help` to show
  default values, reference documentation where required and add additional
  explanation where needed.

- bpo-39144: The ctags and etags build targets both include Modules/_ctypes
  and Python standard library source files.

IDLE
----

- bpo-39050: Make IDLE Settings dialog Help button work again.

- bpo-34118: Tag memoryview, range, and tuple as classes, the same as list,
  etcetera, in the library manual built-in functions list.

- bpo-32989: Add tests for editor newline_and_indent_event method. Remove
  dead code from pyparse find_good_parse_start method.

C API
-----

- bpo-39372: Clean header files of interfaces defined but with no
  implementation. The public API symbols being removed are:
  ``_PyBytes_InsertThousandsGroupingLocale``,
  ``_PyBytes_InsertThousandsGrouping``, ``_Py_InitializeFromArgs``,
  ``_Py_InitializeFromWideArgs``, ``_PyFloat_Repr``, ``_PyFloat_Digits``,
  ``_PyFloat_DigitsInit``, ``PyFrame_ExtendStack``,
  ``_PyAIterWrapper_Type``, ``PyNullImporter_Type``, ``PyCmpWrapper_Type``,
  ``PySortWrapper_Type``, ``PyNoArgsFunction``.

- bpo-39164: Add a private ``_PyErr_GetExcInfo()`` function to retrieve
  exception information of the specified Python thread state.


What's New in Python 3.9.0 alpha 2?
===================================

*Release date: 2019-12-18*

Security
--------

- bpo-38945: Newline characters have been escaped when performing uu
  encoding to prevent them from overflowing into to content section of the
  encoded file. This prevents malicious or accidental modification of data
  during the decoding process.

- bpo-37228: Due to significant security concerns, the *reuse_address*
  parameter of :meth:`asyncio.loop.create_datagram_endpoint` is no longer
  supported. This is because of the behavior of ``SO_REUSEADDR`` in UDP. For
  more details, see the documentation for
  ``loop.create_datagram_endpoint()``. (Contributed by Kyle Stanley, Antoine
  Pitrou, and Yury Selivanov in :issue:`37228`.)

- bpo-38804: Fixes a ReDoS vulnerability in :mod:`http.cookiejar`. Patch by
  Ben Caller.

Core and Builtins
-----------------

- bpo-39028: Slightly improve the speed of keyword argument parsing with
  many kwargs by strengthening the assumption that kwargs are interned
  strings.

- bpo-39080: Fix the value of *end_col_offset* for Starred Expression AST
  nodes when they are among the elements in the *args* attribute of Call AST
  nodes.

- bpo-39031: When parsing an "elif" node, lineno and col_offset of the node
  now point to the "elif" keyword and not to its condition, making it
  consistent with the "if" node. Patch by Lysandros Nikolaou.

- bpo-20443: In Python 3.9.0a1, sys.argv[0] was made an absolute path if a
  filename was specified on the command line. Revert this change, since most
  users expect sys.argv to be unmodified.

- bpo-39008: :c:func:`PySys_Audit` now requires ``Py_ssize_t`` to be used
  for size arguments in the format string, regardless of whether
  ``PY_SSIZE_T_CLEAN`` was defined at include time.

- bpo-38673: In REPL mode, don't switch to PS2 if the line starts with
  comment or whitespace. Based on work by Batuhan Taşkaya.

- bpo-38922: Calling ``replace`` on a code object now raises the
  ``code.__new__`` audit event.

- bpo-38920: Add audit hooks for when :func:`sys.excepthook` and
  :func:`sys.unraisablehook` are invoked.

- bpo-38892: Improve documentation for audit events table and functions.

- bpo-38852: Set the thread stack size to 8 Mb for debug builds on android
  platforms.

- bpo-38858: Each Python subinterpreter now has its own "small integer
  singletons": numbers in [-5; 257] range. It is no longer possible to
  change the number of small integers at build time by overriding
  ``NSMALLNEGINTS`` and ``NSMALLPOSINTS`` macros: macros should now be
  modified manually in ``pycore_pystate.h`` header file.

- bpo-36854: The garbage collector state becomes per interpreter
  (``PyInterpreterState.gc``), rather than being global
  (``_PyRuntimeState.gc``).

- bpo-38835: The ``PyFPE_START_PROTECT()`` and ``PyFPE_END_PROTECT()``
  macros are empty: they have been doing nothing for the last year, so stop
  using them.

- bpo-38328: Sped up the creation time of constant :class:`list` and
  :class:`set` displays. Patch by Brandt Bucher.

- bpo-38707: ``MainThread.native_id`` is now correctly reset in child
  processes spawned using :class:`multiprocessing.Process`, instead of
  retaining the parent's value.

- bpo-38629: Added ``__floor__`` and ``__ceil__`` methods to float object.
  Patch by Batuhan Taşkaya.

- bpo-27145: int + int and int - int operators can now return small integer
  singletons. Patch by hongweipeng.

- bpo-38021: Provide a platform tag for AIX that is sufficient for PEP425
  binary distribution identification. Patch by Michael Felt.

- bpo-35409: Ignore GeneratorExit exceptions when throwing an exception into
  the aclose coroutine of an asynchronous generator.

- bpo-33387: Removed WITH_CLEANUP_START, WITH_CLEANUP_FINISH, BEGIN_FINALLY,
  END_FINALLY, CALL_FINALLY and POP_FINALLY bytecodes. Replaced with RERAISE
  and WITH_EXCEPT_START bytecodes. The compiler now generates different code
  for exceptional and non-exceptional branches for 'with' and 'try-except'
  statements. For 'try-finally' statements the 'finally' block is replicated
  for each exit from the 'try' body.

Library
-------

- bpo-39033: Fix :exc:`NameError` in :mod:`zipimport`. Patch by Karthikeyan
  Singaravelan.

- bpo-39022: Update importlib.metadata to include improvements from
  importlib_metadata 1.3 including better serialization of EntryPoints and
  improved documentation for custom finders.

- bpo-39006: Fix asyncio when the ssl module is missing: only check for
  ssl.SSLSocket instance if the ssl module is available.

- bpo-38708: Fix a potential IndexError in email parser when parsing an
  empty msg-id.

- bpo-38698: Add a new ``InvalidMessageID`` token to email parser to
  represent invalid Message-ID headers.  Also, add defects when there is
  remaining value after parsing the header.

- bpo-38994: Implement ``__class_getitem__`` for ``os.PathLike``,
  ``pathlib.Path``.

- bpo-38979: Return class from ``ContextVar.__class_getitem__`` to simplify
  subclassing.

- bpo-38978: Implement ``__class_getitem__`` on asyncio objects (Future,
  Task, Queue). Patch by Batuhan Taskaya.

- bpo-38916: :class:`array.array`: Remove ``tostring()`` and
  ``fromstring()`` methods. They were aliases to ``tobytes()`` and
  ``frombytes()``, deprecated since Python 3.2.

- bpo-38986: Make repr of C accelerated TaskWakeupMethWrapper the same as of
  pure Python version.

- bpo-38982: Fix asyncio ``PidfdChildWatcher``: handle ``waitpid()`` error.
  If ``waitpid()`` is called elsewhere, ``waitpid()`` call fails with
  :exc:`ChildProcessError`: use return code 255 in this case, and log a
  warning. It ensures that the pidfd file descriptor is closed if this error
  occurs.

- bpo-38529: Drop too noisy asyncio warning about deletion of a stream
  without explicit ``.close()`` call.

- bpo-27413: Added ability to pass through ``ensure_ascii`` options to
  json.dumps in the ``json.tool`` command-line interface.

- bpo-38634: The :mod:`readline` module now detects if Python is linked to
  libedit at runtime on all platforms.  Previously, the check was only done
  on macOS.

- bpo-33684: Fix ``json.tool`` failed to read a JSON file with non-ASCII
  characters when locale encoding is not UTF-8.

- bpo-38698: Prevent UnboundLocalError to pop up in parse_message_id.

  parse_message_id() was improperly using a token defined inside an
  exception handler, which was raising `UnboundLocalError` on parsing an
  invalid value. Patch by Claudiu Popa.

- bpo-38927: Use ``python -m pip`` instead of ``pip`` to upgrade
  dependencies in venv.

- bpo-26730: Fix ``SpooledTemporaryFile.rollover()`` might corrupt the file
  when it is in text mode. Patch by Serhiy Storchaka.

- bpo-38881: random.choices() now raises a ValueError when all the weights
  are zero.

- bpo-38876: Raise pickle.UnpicklingError when loading an item from memo for
  invalid input.

  The previous code was raising a `KeyError` for both the Python and C
  implementation. This was caused by the specified index of an invalid input
  which did not exist in the memo structure, where the pickle stores what
  objects it has seen. The malformed input would have caused either a
  `BINGET` or `LONG_BINGET` load from the memo, leading to a `KeyError` as
  the determined index was bogus. Patch by Claudiu Popa

- bpo-38688: Calling func:`shutil.copytree` to copy a directory tree from
  one directory to another subdirectory resulted in an endless loop and a
  RecursionError. A fix was added to consume an iterator and create the list
  of the entries to be copied, avoiding the recursion for newly created
  directories. Patch by Bruno P. Kinoshita.

- bpo-38863: Improve :func:`is_cgi` function in :mod:`http.server`, which
  enables processing the case that cgi directory is a child of another
  directory other than root.

- bpo-37838: :meth:`typing.get_type_hints` properly handles functions
  decorated with :meth:`functools.wraps`.

- bpo-38870: Expose :func:`ast.unparse` as a function of the :mod:`ast`
  module that can be used to unparse an :class:`ast.AST` object and produce
  a string with code that would produce an equivalent :class:`ast.AST`
  object when parsed. Patch by Pablo Galindo and Batuhan Taskaya.

- bpo-38859: AsyncMock now returns StopAsyncIteration on the exhaustion of a
  side_effects iterable. Since PEP-479 its Impossible to raise a
  StopIteration exception from a coroutine.

- bpo-38857: AsyncMock fix for return values that are awaitable types.  This
  also covers side_effect iterable values that happened to be awaitable, and
  wraps callables that return an awaitable type. Before these awaitables
  were being awaited instead of being returned as is.

- bpo-38834: :class:`typing.TypedDict` subclasses now track which keys are
  optional using the ``__required_keys__`` and ``__optional_keys__``
  attributes, to enable runtime validation by downstream projects.  Patch by
  Zac Hatfield-Dodds.

- bpo-38821: Fix unhandled exceptions in :mod:`argparse` when
  internationalizing error messages for arguments with ``nargs`` set to
  special (non-integer) values. Patch by Federico Bond.

- bpo-38820: Make Python compatible with OpenSSL 3.0.0.
  :func:`ssl.SSLSocket.getpeercert` no longer returns IPv6 addresses with a
  trailing new line.

- bpo-38811: Fix an unhandled exception in :mod:`pathlib` when
  :meth:`os.link` is missing. Patch by Toke Høiland-Jørgensen.

- bpo-38686: Added support for multiple ``qop`` values in
  :class:`urllib.request.AbstractDigestAuthHandler`.

- bpo-38712: Add the Linux-specific :func:`signal.pidfd_send_signal`
  function, which allows sending a signal to a process identified by a file
  descriptor rather than a pid.

- bpo-38348: Add ``-i`` and ``--indent`` (indentation level), and
  ``--no-type-comments`` (type comments) command line options to ast parsing
  tool.

- bpo-37523: Change :class:`zipfile.ZipExtFile` to raise ``ValueError`` when
  trying to access the underlying file object after it has been closed. This
  new behavior is consistent with how accessing closed files is handled in
  other parts of Python.

- bpo-38045: Improve the performance of :func:`enum._decompose` in
  :mod:`enum`. Patch by hongweipeng.

- bpo-36820: Break cycle generated when saving an exception in socket.py,
  codeop.py and dyld.py as they keep alive not only the exception but user
  objects through the ``__traceback__`` attribute. Patch by Mario Corchero.

- bpo-36406: Handle namespace packages in :mod:`doctest`. Patch by
  Karthikeyan Singaravelan.

- bpo-34776: Fix dataclasses to support forward references in type
  annotations

- bpo-20928: ElementTree supports recursive XInclude processing.  Patch by
  Stefan Behnel.

- bpo-29636: Add whitespace options for formatting JSON with the
  ``json.tool`` CLI. The following mutually exclusive options are now
  supported: ``--indent`` for setting the indent level in spaces; ``--tab``
  for indenting with tabs; ``--no-indent`` for suppressing newlines; and
  ``--compact`` for suppressing all whitespace. The default behavior remains
  the same as ``--indent=4``.

Documentation
-------------

- bpo-38928: Correct when venv's ``upgrade_dependencies()`` and
  ``--upgrade-deps`` are added.

- bpo-38899: Update documentation to state that to activate virtual
  environments under fish one should use `source`, not `.` as documented at
  https://fishshell.com/docs/current/commands.html#source.

- bpo-22377: Improves documentation of the values that
  :meth:`datetime.datetime.strptime` accepts for ``%Z``. Patch by Karl
  Dubost.

Tests
-----

- bpo-38546: Fix test_ressources_gced_in_workers() of
  test_concurrent_futures: explicitly stop the manager to prevent leaking a
  child process running in the background after the test completes.

- bpo-38546: Multiprocessing and concurrent.futures tests now stop the
  resource tracker process when tests complete.

- bpo-38614: Replace hardcoded timeout constants in tests with new
  :mod:`test.support` constants: :data:`~test.support.LOOPBACK_TIMEOUT`,
  :data:`~test.support.INTERNET_TIMEOUT`,
  :data:`~test.support.SHORT_TIMEOUT` and
  :data:`~test.support.LONG_TIMEOUT`. It becomes easier to adjust these four
  timeout constants for all tests at once, rather than having to adjust
  every single test file.

- bpo-38547: Fix test_pty: if the process is the session leader, closing the
  master file descriptor raises a SIGHUP signal: simply ignore SIGHUP when
  running the tests.

- bpo-38992: Fix a test for :func:`math.fsum` that was failing due to
  constant folding.

- bpo-38991: :mod:`test.support`:
  :func:`~test.support.run_python_until_end`,
  :func:`~test.support.assert_python_ok` and
  :func:`~test.support.assert_python_failure` functions no longer strip
  whitespaces from stderr. Remove ``test.support.strip_python_stderr()``
  function.

- bpo-38965: Fix test_faulthandler on GCC 10. Use the "volatile" keyword in
  ``faulthandler._stack_overflow()`` to prevent tail call optimization on
  any compiler, rather than relying on compiler specific pragma.

- bpo-38875: test_capi: trashcan tests now require the test "cpu" resource.

- bpo-38841: Skip asyncio test_create_datagram_endpoint_existing_sock_unix
  on platforms lacking a functional bind() for named unix domain sockets.

- bpo-38692: Skip the test_posix.test_pidfd_open() test if
  ``os.pidfd_open()`` fails with a :exc:`PermissionError`. This situation
  can happen in a Linux sandbox using a syscall whitelist which doesn't
  allow the ``pidfd_open()`` syscall yet.

- bpo-38839: Fix some unused functions in tests. Patch by Adam Johnson.

- bpo-38669: Raise :exc:`TypeError` when passing target as a string with
  :meth:`unittest.mock.patch.object`.

- bpo-37957: test.regrtest now can receive a list of test patterns to ignore
  (using the -i/--ignore argument) or a file with a list of patterns to
  ignore (using the --ignore-file argument). Patch by Pablo Galindo.

Build
-----

- bpo-37404: :mod:`asyncio` now raises :exc:`TyperError` when calling
  incompatible methods with an :class:`ssl.SSLSocket` socket.  Patch by Ido
  Michael.

- bpo-36500: Added an optional "regen" project to the Visual Studio solution
  that will regenerate all grammar, tokens, and opcodes.

Windows
-------

- bpo-39007: Add auditing events to functions in :mod:`winreg`.

- bpo-33125: Add support for building and releasing Windows ARM64 packages.

macOS
-----

- bpo-37931: Fixed a crash on OSX dynamic builds that occurred when
  re-initializing the posix module after a Py_Finalize if the environment
  had changed since the previous `import posix`. Patch by Benoît Hudson.

IDLE
----

- bpo-38944: Escape key now closes IDLE completion windows.  Patch by Johnny
  Najera.

- bpo-38943: Fix IDLE autocomplete windows not always appearing on some
  systems. Patch by Johnny Najera.

- bpo-38862: 'Strip Trailing Whitespace' on the Format menu removes extra
  newlines at the end of non-shell files.

- bpo-38636: Fix IDLE Format menu tab toggle and file indent width. These
  functions (default shortcuts Alt-T and Alt-U) were mistakenly disabled in
  3.7.5 and 3.8.0.

C API
-----

- bpo-38896: Remove ``PyUnicode_ClearFreeList()`` function: the Unicode free
  list has been removed in Python 3.3.

- bpo-37340: Remove ``PyMethod_ClearFreeList()`` and
  ``PyCFunction_ClearFreeList()`` functions: the free lists of bound method
  objects have been removed.

- bpo-38835: Exclude ``PyFPE_START_PROTECT()`` and ``PyFPE_END_PROTECT()``
  macros of ``pyfpe.h`` from ``Py_LIMITED_API`` (stable API).


What's New in Python 3.9.0 alpha 1?
===================================

*Release date: 2019-11-19*

Security
--------

- bpo-38722: :mod:`runpy` now uses :meth:`io.open_code` to open code files.
  Patch by Jason Killen.

- bpo-38622: Add additional audit events for the :mod:`ctypes` module.

- bpo-38418: Fixes audit event for :func:`os.system` to be named
  ``os.system``.

- bpo-38243: Escape the server title of
  :class:`xmlrpc.server.DocXMLRPCServer` when rendering the document page as
  HTML. (Contributed by Dong-hee Na in :issue:`38243`.)

- bpo-38174: Update vendorized expat library version to 2.2.8, which
  resolves CVE-2019-15903.

- bpo-37764: Fixes email._header_value_parser.get_unstructured going into an
  infinite loop for a specific case in which the email header does not have
  trailing whitespace, and the case in which it contains an invalid encoded
  word. Patch by Ashwin Ramaswami.

- bpo-37461: Fix an infinite loop when parsing specially crafted email
  headers. Patch by Abhilash Raj.

- bpo-37363: Adds audit events for the range of supported run commands (see
  :ref:`using-on-general`).

- bpo-37463: ssl.match_hostname() no longer accepts IPv4 addresses with
  additional text after the address and only quad-dotted notation without
  trailing whitespaces. Some inet_aton() implementations ignore whitespace
  and all data after whitespace, e.g. '127.0.0.1 whatever'.

- bpo-37363: Adds audit events for :mod:`ensurepip`, :mod:`ftplib`,
  :mod:`glob`, :mod:`imaplib`, :mod:`nntplib`, :mod:`pdb`, :mod:`poplib`,
  :mod:`shutil`, :mod:`smtplib`, :mod:`sqlite3`, :mod:`subprocess`,
  :mod:`telnetlib`, :mod:`tempfile` and :mod:`webbrowser`, as well as
  :func:`os.listdir`, :func:`os.scandir` and :func:`breakpoint`.

- bpo-37364: :func:`io.open_code` is now used when reading :file:`.pth`
  files.

- bpo-34631: Updated OpenSSL to 1.1.1c in Windows installer

- bpo-34155: Fix parsing of invalid email addresses with more than one ``@``
  (e.g. a@b@c.com.) to not return the part before 2nd ``@`` as valid email
  address. Patch by maxking & jpic.

Core and Builtins
-----------------

- bpo-38631: Replace ``Py_FatalError()`` call with a regular
  :exc:`RuntimeError` exception in :meth:`float.__getformat__`.

- bpo-38639: Optimized :func:`math.floor()`, :func:`math.ceil()` and
  :func:`math.trunc()` for floats.

- bpo-38640: Fixed a bug in the compiler that was causing to raise in the
  presence of break statements and continue statements inside always false
  while loops. Patch by Pablo Galindo.

- bpo-38613: Optimized some set operations (e.g. ``|``, ``^``, and ``-``) of
  ``dict_keys``. ``d.keys() | other`` was slower than ``set(d) | other`` but
  they are almost same performance for now.

- bpo-28029: ``"".replace("", s, n)`` now returns ``s`` instead of an empty
  string for all non-zero ``n``.  There are similar changes for
  :class:`bytes` and :class:`bytearray` objects.

- bpo-38535: Fixed line numbers and column offsets for AST nodes for calls
  without arguments in decorators.

- bpo-38525: Fix a segmentation fault when using reverse iterators of empty
  ``dict`` objects. Patch by Dong-hee Na and Inada Naoki.

- bpo-38465: :class:`bytearray`, :class:`~array.array` and
  :class:`~mmap.mmap` objects allow now to export more than ``2**31``
  buffers at a time.

- bpo-38469: Fixed a bug where the scope of named expressions was not being
  resolved correctly in the presence of the *global* keyword. Patch by Pablo
  Galindo.

- bpo-38437: Activate the ``GC_DEBUG`` macro for debug builds of the
  interpreter (when ``Py_DEBUG`` is set). Patch by Pablo Galindo.

- bpo-38379: When the garbage collector makes a collection in which some
  objects resurrect (they are reachable from outside the isolated cycles
  after the finalizers have been executed), do not block the collection of
  all objects that are still unreachable. Patch by Pablo Galindo and Tim
  Peters.

- bpo-38379: When cyclic garbage collection (gc) runs finalizers that
  resurrect unreachable objects, the current gc run ends, without collecting
  any cyclic trash.  However, the statistics reported by ``collect()`` and
  ``get_stats()`` claimed that all cyclic trash found was collected, and
  that the resurrected objects were collected.   Changed the stats to report
  that none were collected.

- bpo-38392: In debug mode, :c:func:`PyObject_GC_Track` now calls
  ``tp_traverse()`` of the object type to ensure that the object is valid:
  test that objects visited by ``tp_traverse()`` are valid.

- bpo-38210: Remove unnecessary intersection and update set operation in
  dictview with empty set. (Contributed by Dong-hee Na in :issue:`38210`.)

- bpo-38402: Check the error from the system's underlying ``crypt`` or
  ``crypt_r``.

- bpo-37474: On FreeBSD, Python no longer calls ``fedisableexcept()`` at
  startup to control the floating point control mode. The call became
  useless since FreeBSD 6: it became the default mode.

- bpo-38006: Fix a bug due to the interaction of weakrefs and the cyclic
  garbage collector. We must clear any weakrefs in garbage in order to
  prevent their callbacks from executing and causing a crash.

- bpo-38317: Fix warnings options priority: ``PyConfig.warnoptions`` has the
  highest priority, as stated in the :pep:`587`.

- bpo-38310: Predict ``BUILD_MAP_UNPACK_WITH_CALL`` -> ``CALL_FUNCTION_EX``
  opcode pairs in the main interpreter loop. Patch by Brandt Bucher.

- bpo-36871: Improve error handling for the assert_has_calls and
  assert_has_awaits methods of mocks. Fixed a bug where any errors
  encountered while binding the expected calls to the mock's spec were
  silently swallowed, leading to misleading error output.

- bpo-11410: Better control over symbol visibility is provided through use
  of the visibility attributes available in gcc >= 4.0, provided in a
  uniform way across POSIX and Windows. The POSIX build files have been
  updated to compile with -fvisibility=hidden, minimising exported symbols.

- bpo-38219: Optimized the :class:`dict` constructor and the
  :meth:`~dict.update` method for the case when the argument is a dict.

- bpo-38236: Python now dumps path configuration if it fails to import the
  Python codecs of the filesystem and stdio encodings.

- bpo-38013: Allow to call ``async_generator_athrow().throw(...)`` even for
  non-started async generator helper. It fixes annoying warning at the end
  of :func:`asyncio.run` call.

- bpo-38124: Fix an off-by-one error in PyState_AddModule that could cause
  out-of-bounds memory access.

- bpo-38116: The select module is now PEP-384 compliant and no longer has
  static state

- bpo-38113: ast module updated to PEP-384 and all statics removed

- bpo-38076: The struct module is now PEP-384 compatible

- bpo-38075: The random module is now PEP-384 compatible

- bpo-38074: zlib module made PEP-384 compatible

- bpo-38073: Make pwd extension module PEP-384 compatible

- bpo-38072: grp module made PEP-384 compatible

- bpo-38069: Make _posixsubprocess PEP-384 compatible

- bpo-38071: Make termios extension module PEP-384 compatible

- bpo-38005: Fixed comparing and creating of InterpreterID and ChannelID.

- bpo-36946: Fix possible signed integer overflow when handling slices.
  Patch by hongweipeng.

- bpo-37994: Fixed silencing arbitrary errors if an attribute lookup fails
  in several sites. Only AttributeError should be silenced.

- bpo-8425: Optimize set difference_update for the case when the other set
  is much larger than the base set.  (Suggested by Evgeny Kapun with code
  contributed by Michele Orrù).

- bpo-37966: The implementation of :func:`~unicodedata.is_normalized` has
  been greatly sped up on strings that aren't normalized, by implementing
  the full normalization-quick-check algorithm from the Unicode standard.

- bpo-37947: Adjust correctly the recursion level in the symtable generation
  for named expressions. Patch by Pablo Galindo.

- bpo-37812: The ``CHECK_SMALL_INT`` macro used inside
  :file:`Object/longobject.c` has been replaced with an explicit ``return``
  at each call site.

- bpo-37751: Fix :func:`codecs.lookup` to normalize the encoding name the
  same way than :func:`encodings.normalize_encoding`, except that
  :func:`codecs.lookup` also converts the name to lower case.

- bpo-37830: Fixed compilation of :keyword:`break` and :keyword:`continue`
  in the :keyword:`finally` block when the corresponding :keyword:`try`
  block contains :keyword:`return` with a non-constant value.

- bpo-20490: Improve import error message for partially initialized module
  on circular ``from`` imports - by Anthony Sottile.

- bpo-37840: Fix handling of negative indices in
  :c:member:`~PySequenceMethods.sq_item` of :class:`bytearray`. Patch by
  Sergey Fedoseev.

- bpo-37802: Slightly improve performance of
  :c:func:`PyLong_FromUnsignedLong`, :c:func:`PyLong_FromUnsignedLongLong`
  and :c:func:`PyLong_FromSize_t`. Patch by Sergey Fedoseev.

- bpo-37409: Ensure explicit relative imports from interactive sessions and
  scripts (having no parent package) always raise ImportError, rather than
  treating the current module as the package. Patch by Ben Lewis.

- bpo-32912: Reverted :issue:`32912`: emitting :exc:`SyntaxWarning` instead
  of :exc:`DeprecationWarning` for invalid escape sequences in string and
  bytes literals.

- bpo-37757: :pep:`572`: As described in the PEP, assignment expressions now
  raise :exc:`SyntaxError` when their interaction with comprehension scoping
  results in an ambiguous target scope.

  The ``TargetScopeError`` subclass originally proposed by the PEP has been
  removed in favour of just raising regular syntax errors for the disallowed
  cases.

- bpo-36279: Fix potential use of uninitialized memory in :func:`os.wait3`.

- bpo-36311: Decoding bytes objects larger than 2GiB is faster and no longer
  fails when a multibyte characters spans a chunk boundary.

- bpo-34880: The :keyword:`assert` statement now works properly if the
  :exc:`AssertionError` exception is being shadowed. Patch by Zackery Spytz.

- bpo-37340: Removed object cache (``free_list``) for bound method objects.
  Temporary bound method objects are less used than before thanks to the
  ``LOAD_METHOD`` opcode and the ``_PyObject_VectorcallMethod`` C API.

- bpo-37648: Fixed minor inconsistency in :meth:`list.__contains__`,
  :meth:`tuple.__contains__` and a few other places. The collection's item
  is now always at the left and the needle is on the right of ``==``.

- bpo-37444: Update differing exception between :meth:`builtins.__import__`
  and :meth:`importlib.__import__`.

- bpo-37619: When adding a wrapper descriptor from one class to a different
  class (for example, setting ``__add__ = str.__add__`` on an ``int``
  subclass), an exception is correctly raised when the operator is called.

- bpo-37593: Swap the positions of the *posonlyargs* and *args* parameters
  in the constructor of :class:`ast.parameters` nodes.

- bpo-37543: Optimized pymalloc for non PGO build.

- bpo-37537: Compute allocated pymalloc blocks inside
  _Py_GetAllocatedBlocks().  This slows down _Py_GetAllocatedBlocks() but
  gives a small speedup to _PyObject_Malloc() and _PyObject_Free().

- bpo-37467: Fix :func:`sys.excepthook` and :c:func:`PyErr_Display` if a
  filename is a bytes string. For example, for a SyntaxError exception where
  the filename attribute is a bytes string.

- bpo-37433: Fix ``SyntaxError`` indicator printing too many spaces for
  multi-line strings - by Anthony Sottile.

- bpo-37417: :meth:`bytearray.extend` now correctly handles errors that
  arise during iteration. Patch by Brandt Bucher.

- bpo-37414: The undocumented ``sys.callstats()`` function has been removed.
  Since Python 3.7, it was deprecated and always returned ``None``. It
  required a special build option ``CALL_PROFILE`` which was already removed
  in Python 3.7.

- bpo-37392: Remove ``sys.getcheckinterval()`` and
  ``sys.setcheckinterval()`` functions. They were deprecated since Python
  3.2. Use :func:`sys.getswitchinterval` and :func:`sys.setswitchinterval`
  instead. Remove also ``check_interval`` field of the
  ``PyInterpreterState`` structure.

- bpo-37388: In development mode and in debug build, *encoding* and *errors*
  arguments are now checked on string encoding and decoding operations.
  Examples: :func:`open`, :meth:`str.encode` and :meth:`bytes.decode`.

  By default, for best performances, the *errors* argument is only checked
  at the first encoding/decoding error, and the *encoding* argument is
  sometimes ignored for empty strings.

- bpo-37348: Optimized decoding short ASCII string with UTF-8 and ascii
  codecs. ``b"foo".decode()`` is about 15% faster.  Patch by Inada Naoki.

- bpo-24214: Improved support of the surrogatepass error handler in the
  UTF-8 and UTF-16 incremental decoders.

- bpo-37330: :func:`open`, :func:`io.open`, :func:`codecs.open` and
  :class:`fileinput.FileInput` no longer accept ``'U'`` ("universal
  newline") in the file mode. This flag was deprecated since Python 3.3.

- bpo-35224: Reverse evaluation order of key: value in dict comprehensions
  as proposed in PEP 572. I.e. in ``{k: v for ...}``, ``k`` will be
  evaluated before ``v``.

- bpo-37316: Fix the :c:func:`PySys_Audit` call in :class:`mmap.mmap`.

- bpo-37300: Remove an unnecessary Py_XINCREF in classobject.c.

- bpo-37269: Fix a bug in the peephole optimizer that was not treating
  correctly constant conditions with binary operators. Patch by Pablo
  Galindo.

- bpo-20443: Python now gets the absolute path of the script filename
  specified on the command line (ex: "python3 script.py"): the __file__
  attribute of the __main__ module and sys.path[0] become an absolute path,
  rather than a relative path.

- bpo-37257: Python's small object allocator (``obmalloc.c``) now allows (no
  more than) one empty arena to remain available for immediate reuse,
  without returning it to the OS.  This prevents thrashing in simple loops
  where an arena could be created and destroyed anew on each iteration.

- bpo-37231: The dispatching of type slots to special methods (for example
  calling ``__mul__`` when doing ``x * y``) has been made faster.

- bpo-36974: Implemented separate vectorcall functions for every calling
  convention of builtin functions and methods. This improves performance for
  calls.

- bpo-37213: Handle correctly negative line offsets in the peephole
  optimizer. Patch by Pablo Galindo.

- bpo-37219: Remove erroneous optimization for empty set differences.

- bpo-15913: Implement :c:func:`PyBuffer_SizeFromFormat()` function
  (previously documented but not implemented): call :func:`struct.calcsize`.
  Patch by Joannah Nanjekye.

- bpo-36922: Slot functions optimize any callable with
  ``Py_TPFLAGS_METHOD_DESCRIPTOR`` instead of only instances of
  ``function``.

- bpo-36974: The slot ``tp_vectorcall_offset`` is inherited unconditionally
  to support ``super().__call__()`` when the base class uses vectorcall.

- bpo-37160: :func:`threading.get_native_id` now also supports NetBSD.

- bpo-37077: Add :func:`threading.get_native_id` support for AIX. Patch by
  M. Felt

- bpo-36781: :func:`sum` has been optimized for boolean values.

- bpo-34556: Add ``--upgrade-deps`` to venv module. Patch by Cooper Ry Lees

- bpo-20523: ``pdb.Pdb`` supports ~/.pdbrc in Windows 7. Patch by Tim Hopper
  and Dan Lidral-Porter.

- bpo-35551: Updated encodings: - Removed the "tis260" encoding, which was
  an alias for the nonexistent "tactis" codec. - Added "mac_centeuro" as an
  alias for the mac_latin2 encoding.

- bpo-19072: The :class:`classmethod` decorator can now wrap other
  descriptors such as property objects.  Adapted from a patch written by
  Graham Dumpleton.

- bpo-27575: Improve speed of dictview intersection by directly using set
  intersection logic. Patch by David Su.

- bpo-30773: Prohibit parallel running of aclose() / asend() / athrow(). Fix
  ag_running to reflect the actual running status of the AG.

Library
-------

- bpo-36589: The :func:`curses.update_lines_cols` function now returns
  ``None`` instead of ``1`` on success.

- bpo-38807: Update :exc:`TypeError` messages for :meth:`os.path.join` to
  include :class:`os.PathLike` objects as acceptable input types.

- bpo-38724: Add a repr for ``subprocess.Popen`` objects. Patch by Andrey
  Doroschenko.

- bpo-38786: pydoc now recognizes and parses HTTPS URLs. Patch by python273.

- bpo-38785: Prevent asyncio from crashing if parent ``__init__`` is not
  called from a constructor of object derived from ``asyncio.Future``.

- bpo-38723: :mod:`pdb` now uses :meth:`io.open_code` to trigger auditing
  events.

- bpo-27805: Allow opening pipes and other non-seekable files in append mode
  with :func:`open`.

- bpo-38438: Simplify the :mod:`argparse` usage message for ``nargs="*"``.

- bpo-38761: WeakSet is now registered as a collections.abc.MutableSet.

- bpo-38716: logging: change RotatingHandler namer and rotator to
  class-level attributes. This stops __init__ from setting them to None in
  the case where a subclass defines them with eponymous methods.

- bpo-38713: Add :data:`os.P_PIDFD` constant, which may be passed to
  :func:`os.waitid` to wait on a Linux process file descriptor.

- bpo-38692: Add :class:`asyncio.PidfdChildWatcher`, a Linux-specific child
  watcher implementation that polls process file descriptors.

- bpo-38692: Expose the Linux ``pidfd_open`` syscall as
  :func:`os.pidfd_open`.

- bpo-38602: Added constants :data:`~fcntl.F_OFD_GETLK`,
  :data:`~fcntl.F_OFD_SETLK` and :data:`~fcntl.F_OFD_SETLKW` to the
  :mod:`fcntl` module. Patch by Dong-hee Na.

- bpo-38334: Fixed seeking backward on an encrypted
  :class:`zipfile.ZipExtFile`.

- bpo-38312: Add :func:`curses.get_escdelay`, :func:`curses.set_escdelay`,
  :func:`curses.get_tabsize`, and :func:`curses.set_tabsize` functions - by
  Anthony Sottile.

- bpo-38586: Now :func:`~logging.config.fileConfig` correctly sets the .name
  of handlers loaded.

- bpo-38565: Add new cache_parameters() method for functools.lru_cache() to
  better support pickling.

- bpo-34679: asynci.ProactorEventLoop.close() now only calls
  signal.set_wakeup_fd() in the main thread.

- bpo-31202: The case the result of :func:`pathlib.WindowsPath.glob` matches
  now the case of the pattern for literal parts.

- bpo-36321: Remove misspelled attribute.  The 3.8 changelog noted that this
  would be removed in 3.9.

- bpo-38521: Fixed erroneous equality comparison in statistics.NormalDist().

- bpo-38493: Added :data:`~os.CLD_KILLED` and :data:`~os.CLD_STOPPED` for
  :attr:`si_code`. Patch by Dong-hee Na.

- bpo-38478: Fixed a bug in :meth:`inspect.signature.bind` that was causing
  it to fail when handling a keyword argument with same name as
  positional-only parameter. Patch by Pablo Galindo.

- bpo-33604: Fixed `hmac.new` and `hmac.HMAC` to raise TypeError instead of
  ValueError when the digestmod parameter, now required in 3.8, is omitted.
  Also clarified the hmac module documentation and docstrings.

- bpo-38378: Parameters *out* and *in* of :func:`os.sendfile` was renamed to
  *out_fd* and *in_fd*.

- bpo-38417: Added support for setting the umask in the child process to the
  subprocess module on POSIX systems.

- bpo-38449: Revert PR 15522, which introduces a regression in
  :meth:`mimetypes.guess_type` due to improper handling of filenames as
  urls.

- bpo-38431: Fix ``__repr__`` method for :class:`dataclasses.InitVar` to
  support typing objects, patch by Samuel Colvin.

- bpo-38109: Add missing :data:`stat.S_IFDOOR`, :data:`stat.S_IFPORT`,
  :data:`stat.S_IFWHT`, :func:`stat.S_ISDOOR`, :func:`stat.S_ISPORT`, and
  :func:`stat.S_ISWHT` values to the Python implementation of :mod:`stat`.

- bpo-38422: Clarify docstrings of pathlib suffix(es)

- bpo-38405: Nested subclasses of :class:`typing.NamedTuple` are now
  pickleable.

- bpo-38332: Prevent :exc:`KeyError` thrown by :func:`_encoded_words.decode`
  when given an encoded-word with invalid content-type encoding from
  propagating all the way to :func:`email.message.get`.

- bpo-38371: Deprecated the ``split()`` method in
  :class:`_tkinter.TkappType` in favour of the ``splitlist()`` method which
  has more consistent and predicable behavior.

- bpo-38341: Add :exc:`smtplib.SMTPNotSupportedError` to the :mod:`smtplib`
  exported names.

- bpo-38319: sendfile() used in socket and shutil modules was raising
  OverflowError for files >= 2GiB on 32-bit architectures.  (patch by
  Giampaolo Rodola)

- bpo-38242: Revert the new asyncio Streams API

- bpo-13153: OS native encoding is now used for converting between Python
  strings and Tcl objects.  This allows to display, copy and paste to
  clipboard emoji and other non-BMP characters.  Converting strings from Tcl
  to Python and back now never fails (except MemoryError).

- bpo-38019: Correctly handle pause/resume reading of closed asyncio unix
  pipe.

- bpo-38163: Child mocks will now detect their type as either synchronous or
  asynchronous, asynchronous child mocks will be AsyncMocks and synchronous
  child mocks will be either MagicMock or Mock (depending on their parent
  type).

- bpo-38161: Removes _AwaitEvent from AsyncMock.

- bpo-38216: Allow the rare code that wants to send invalid http requests
  from the `http.client` library a way to do so.  The fixes for bpo-30458
  led to breakage for some projects that were relying on this ability to
  test their own behavior in the face of bad requests.

- bpo-28286: Deprecate opening :class:`~gzip.GzipFile` for writing
  implicitly.  Always specify the *mode* argument for writing.

- bpo-38108: Any synchronous magic methods on an AsyncMock now return a
  MagicMock. Any asynchronous magic methods on a MagicMock now return an
  AsyncMock.

- bpo-38265: Update the *length* parameter of :func:`os.pread` to accept
  :c:type:`Py_ssize_t` instead of :c:type:`int`.

- bpo-38112: :mod:`compileall` has a higher default recursion limit and new
  command-line arguments for path manipulation, symlinks handling, and
  multiple optimization levels.

- bpo-38248: asyncio: Fix inconsistent immediate Task cancellation

- bpo-38237: The arguments for the builtin pow function are more
  descriptive. They can now also be passed in as keywords.

- bpo-34002: Improve efficiency in parts of email package by changing
  while-pop to a for loop, using isdisjoint instead of set intersections.

- bpo-38191: Constructors of :class:`~typing.NamedTuple` and
  :class:`~typing.TypedDict` types now accept arbitrary keyword argument
  names, including "cls", "self", "typename", "_typename", "fields" and
  "_fields".

- bpo-38155: Add ``__all__`` to  :mod:`datetime`. Patch by Tahia Khan.

- bpo-38185: Fixed case-insensitive string comparison in
  :class:`sqlite3.Row` indexing.

- bpo-38136: Changes AsyncMock call count and await count to be two
  different counters. Now await count only counts when a coroutine has been
  awaited, not when it has been called, and vice-versa. Update the
  documentation around this.

- bpo-37828: Fix default mock name in
  :meth:`unittest.mock.Mock.assert_called` exceptions. Patch by Abraham
  Toriz Cruz.

- bpo-38175: Fix a memory leak in comparison of :class:`sqlite3.Row`
  objects.

- bpo-33936: _hashlib no longer calls obsolete OpenSSL initialization
  function with OpenSSL 1.1.0+.

- bpo-34706: Preserve subclassing in inspect.Signature.from_callable.

- bpo-38153: Names of hashing algorithms from OpenSSL are now normalized to
  follow Python's naming conventions. For example OpenSSL uses sha3-512
  instead of sha3_512 or blake2b512 instead of blake2b.

- bpo-38115: Fix a bug in dis.findlinestarts() where it would return invalid
  bytecode offsets. Document that a code object's co_lnotab can contain
  invalid bytecode offsets.

- bpo-38148: Add slots to :mod:`asyncio` transport classes, which can reduce
  memory usage.

- bpo-38142: The _hashlib OpenSSL wrapper extension module is now PEP-384
  compliant.

- bpo-9216: hashlib constructors now support usedforsecurity flag to signal
  that a hashing algorithm is not used in a security context.

- bpo-36991: Fixes a potential incorrect AttributeError exception escaping
  ZipFile.extract() in some unsupported input error situations.

- bpo-38134: Remove obsolete copy of PBKDF2_HMAC_fast. All supported OpenSSL
  versions contain a fast implementation.

- bpo-38132: The OpenSSL hashlib wrapper uses a simpler implementation.
  Several Macros and pointless caches are gone. The hash name now comes from
  OpenSSL's EVP. The algorithm name stays the same, except it is now always
  lower case.

- bpo-38008: Fix parent class check in protocols to correctly identify the
  module that provides a builtin protocol, instead of assuming they all come
  from the :mod:`collections.abc` module

- bpo-34037: For :mod:`asyncio`, add a new coroutine
  :meth:`loop.shutdown_default_executor`. The new coroutine provides an API
  to schedule an executor shutdown that waits on the threadpool to finish
  closing. Also, :func:`asyncio.run` has been updated to utilize the new
  coroutine. Patch by Kyle Stanley.

- bpo-37405: Fixed regression bug for socket.getsockname() for non-CAN_ISOTP
  AF_CAN address family sockets by returning a 1-tuple instead of string.

- bpo-38121: Update parameter names on functions in importlib.metadata
  matching the changes in the 0.22 release of importlib_metadata.

- bpo-38110: The os.closewalk() implementation now uses the libc fdwalk()
  API on platforms where it is available.

- bpo-38093: Fixes AsyncMock so it doesn't crash when used with
  AsyncContextManagers or AsyncIterators.

- bpo-37488: Add warning to :meth:`datetime.utctimetuple`,
  :meth:`datetime.utcnow` and :meth:`datetime.utcfromtimestamp` .

- bpo-35640: Allow passing a :term:`path-like object` as ``directory``
  argument to the :class:`http.server.SimpleHTTPRequestHandler` class. Patch
  by Géry Ogam.

- bpo-38086: Update importlib.metadata with changes from `importlib_metadata
  0.21
  <https://gitlab.com/python-devs/importlib_metadata/blob/0.21/importlib_metadata/docs/changelog.rst>`_.

- bpo-37251: Remove `__code__` check in AsyncMock that incorrectly evaluated
  function specs as async objects but failed to evaluate classes with
  `__await__` but no `__code__` attribute defined as async objects.

- bpo-38037: Fix reference counters in the :mod:`signal` module.

- bpo-38066: Hide internal asyncio.Stream methods: feed_eof(), feed_data(),
  set_exception() and set_transport().

- bpo-38059: inspect.py now uses sys.exit() instead of exit()

- bpo-38049: Added command-line interface for the :mod:`ast` module.

- bpo-37953: In :mod:`typing`, improved the ``__hash__`` and ``__eq__``
  methods for :class:`ForwardReferences`.

- bpo-38026: Fixed :func:`inspect.getattr_static` used ``isinstance`` while
  it should avoid dynamic lookup.

- bpo-35923: Update :class:`importlib.machinery.BuiltinImporter` to use
  ``loader._ORIGIN`` instead of a hardcoded value. Patch by Dong-hee Na.

- bpo-38010: In ``importlib.metadata`` sync with ``importlib_metadata``
  0.20, clarifying behavior of ``files()`` and fixing issue where only one
  requirement was returned for ``requires()`` on ``dist-info`` packages.

- bpo-38006: weakref.WeakValueDictionary defines a local remove() function
  used as callback for weak references. This function was created with a
  closure. Modify the implementation to avoid the closure.

- bpo-37995: Added the *indent* option to :func:`ast.dump` which allows it
  to produce a multiline indented output.

- bpo-34410: Fixed a crash in the :func:`tee` iterator when re-enter it.
  RuntimeError is now raised in this case.

- bpo-37140: Fix a ctypes regression of Python 3.8. When a ctypes.Structure
  is passed by copy to a function, ctypes internals created a temporary
  object which had the side effect of calling the structure finalizer
  (__del__) twice. The Python semantics requires a finalizer to be called
  exactly once. Fix ctypes internals to no longer call the finalizer twice.

- bpo-37587: ``_json.scanstring`` is now up to 3x faster when there are many
  backslash escaped characters in the JSON string.

- bpo-37834: Prevent shutil.rmtree exception when built on non-Windows
  system without fd system call support, like older versions of macOS.

- bpo-10978: Semaphores and BoundedSemaphores can now release more than one
  waiting thread at a time.

- bpo-37972: Subscripts to the `unittest.mock.call` objects now receive the
  same chaining mechanism as any other custom attributes, so that the
  following usage no longer raises a `TypeError`:

  call().foo().__getitem__('bar')

  Patch by blhsing

- bpo-37965: Fix C compiler warning caused by
  distutils.ccompiler.CCompiler.has_function.

- bpo-37964: Add ``F_GETPATH`` command to :mod:`fcntl`.

- bpo-37960: ``repr()`` of buffered and text streams now silences only
  expected exceptions when get the value of "name" and "mode" attributes.

- bpo-37961: Add a ``total_nframe`` field to the traces collected by the
  tracemalloc module. This field indicates the original number of frames
  before it was truncated.

- bpo-37951: Most features of the subprocess module now work again in
  subinterpreters. Only *preexec_fn* is restricted in subinterpreters.

- bpo-36205: Fix the rusage implementation of time.process_time() to
  correctly report the sum of the system and user CPU time.

- bpo-37950: Fix :func:`ast.dump` when call with incompletely initialized
  node.

- bpo-34679: Restores instantiation of Windows IOCP event loops from the
  non-main thread.

- bpo-36917: Add default implementation of the
  :meth:`ast.NodeVisitor.visit_Constant` method which emits a deprecation
  warning and calls corresponding methody ``visit_Num()``, ``visit_Str()``,
  etc.

- bpo-37798: Update test_statistics.py to verify that the statistics module
  works well for both C and Python implementations. Patch by Dong-hee Na

- bpo-26589: Added a new status code to the http module: 451
  UNAVAILABLE_FOR_LEGAL_REASONS

- bpo-37915: Fix a segmentation fault that appeared when comparing instances
  of ``datetime.timezone`` and ``datetime.tzinfo`` objects. Patch by Pablo
  Galindo.

- bpo-32554: Deprecate having random.seed() call hash on arbitrary types.

- bpo-9938: Add optional keyword argument ``exit_on_error`` for
  :class:`ArgumentParser`.

- bpo-37851: The :mod:`faulthandler` module no longer allocates its
  alternative stack at Python startup. Now the stack is only allocated at
  the first faulthandler usage.

- bpo-32793: Fix a duplicated debug message when
  :meth:`smtplib.SMTP.connect` is called.

- bpo-37885: venv: Don't generate unset variable warning on deactivate.

- bpo-37868: Fix dataclasses.is_dataclass when given an instance that never
  raises AttributeError in __getattr__.  That is, an object that returns
  something for __dataclass_fields__ even if it's not a dataclass.

- bpo-37811: Fix ``socket`` module's ``socket.connect(address)`` function
  being unable to establish connection in case of interrupted system call.
  The problem was observed on all OSes which ``poll(2)`` system call can
  take only non-negative integers and -1 as a timeout value.

- bpo-37863: Optimizations for Fraction.__hash__ suggested by Tim Peters.

- bpo-21131: Fix ``faulthandler.register(chain=True)`` stack. faulthandler
  now allocates a dedicated stack of ``SIGSTKSZ*2`` bytes, instead of just
  ``SIGSTKSZ`` bytes. Calling the previous signal handler in faulthandler
  signal handler uses more than ``SIGSTKSZ`` bytes of stack memory on some
  platforms.

- bpo-37798: Add C fastpath for statistics.NormalDist.inv_cdf() Patch by
  Dong-hee Na

- bpo-37804: Remove the deprecated method `threading.Thread.isAlive()`.
  Patch by Dong-hee Na.

- bpo-37819: Add Fraction.as_integer_ratio() to match the corresponding
  methods in bool, int, float, and decimal.

- bpo-14465: Add an xml.etree.ElementTree.indent() function for
  pretty-printing XML trees. Contributed by Stefan Behnel.

- bpo-37810: Fix :mod:`difflib` ``?`` hint in diff output when dealing with
  tabs.  Patch by Anthony Sottile.

- bpo-37772: In ``zipfile.Path``, when adding implicit dirs, ensure that
  ancestral directories are added and that duplicates are excluded.

- bpo-18578: Renamed and documented `test.bytecode_helper` as
  `test.support.bytecode_helper`. Patch by Joannah Nanjekye.

- bpo-37785: Fix xgettext warnings in :mod:`argparse`.

- bpo-34488: :meth:`writelines` method of :class:`io.BytesIO` is now
  slightly faster when many small lines are passed. Patch by Sergey
  Fedoseev.

- bpo-37449: `ensurepip` now uses `importlib.resources.read_binary()` to
  read data instead of `pkgutil.get_data()`. Patch by Joannah Nanjekye.

- bpo-28292: Mark calendar.py helper functions as being private.  The
  follows PEP 8 guidance to maintain the style conventions in the module and
  it addresses a known case of user confusion.

- bpo-18049: Add definition of THREAD_STACK_SIZE for AIX in
  Python/thread_pthread.h The default thread stacksize caused crashes with
  the default recursion limit Patch by M Felt

- bpo-37742: The logging.getLogger() API now returns the root logger when
  passed the name 'root', whereas previously it returned a non-root logger
  named 'root'. This could affect cases where user code explicitly wants a
  non-root logger named 'root', or instantiates a logger using
  logging.getLogger(__name__) in some top-level module called 'root.py'.

- bpo-37738: Fix the implementation of curses ``addch(str, color_pair)``:
  pass the color pair to ``setcchar()``, instead of always passing 0 as the
  color pair.

- bpo-37723: Fix performance regression on regular expression parsing with
  huge character sets. Patch by Yann Vaginay.

- bpo-35943: The function :c:func:`PyImport_GetModule` now ensures any
  module it returns is fully initialized. Patch by Joannah Nanjekye.

- bpo-32178: Fix IndexError in :mod:`email` package when trying to parse
  invalid address fields starting with ``:``.

- bpo-37268: The :mod:`parser` module is deprecated and will be removed in
  future versions of Python.

- bpo-11953: Completing WSA* error codes in :mod:`socket`.

- bpo-37685: Fixed comparisons of :class:`datetime.timedelta` and
  :class:`datetime.timezone`.

- bpo-37697: Synchronize ``importlib.metadata`` with `importlib_metadata
  0.19
  <https://gitlab.com/python-devs/importlib_metadata/-/milestones/20>`_,
  improving handling of EGG-INFO files and fixing a crash when entry point
  names contained colons.

- bpo-37695: Correct :func:`curses.unget_wch` error message.  Patch by
  Anthony Sottile.

- bpo-37689: Add :meth:`is_relative_to` in :class:`PurePath` to determine
  whether or not one path is relative to another.

- bpo-29553: Fixed :meth:`argparse.ArgumentParser.format_usage` for mutually
  exclusive groups. Patch by Andrew Nester.

- bpo-37691: Let math.dist() accept coordinates as sequences (or iterables)
  rather than just tuples.

- bpo-37685: Fixed ``__eq__``, ``__lt__`` etc implementations in some
  classes. They now return :data:`NotImplemented` for unsupported type of
  the other operand. This allows the other operand to play role (for example
  the equality comparison with :data:`~unittest.mock.ANY` will return
  ``True``).

- bpo-37354: Make Activate.ps1 Powershell script static to allow for signing
  it.

- bpo-37664: Update wheels bundled with ensurepip (pip 19.2.3 and setuptools
  41.2.0)

- bpo-37663: Bring consistency to venv shell activation scripts by always
  using __VENV_PROMPT__.

- bpo-37642: Allowed the pure Python implementation of
  :class:`datetime.timezone` to represent sub-minute offsets close to
  minimum and maximum boundaries, specifically in the ranges (23:59, 24:00)
  and (-23:59, 24:00). Patch by Ngalim Siregar

- bpo-36161: In :mod:`posix`, use ``ttyname_r`` instead of ``ttyname`` for
  thread safety.

- bpo-36324: Make internal attributes for statistics.NormalDist() private.

- bpo-37555: Fix `NonCallableMock._call_matcher` returning tuple instead of
  `_Call` object when `self._spec_signature` exists. Patch by Elizabeth
  Uselton

- bpo-29446: Make `from tkinter import *` import only the expected objects.

- bpo-16970: Adding a value error when an invalid value in passed to nargs
  Patch by Robert Leenders

- bpo-34443: Exceptions from :mod:`enum` now use the ``__qualname`` of the
  enum class in the exception message instead of the ``__name__``.

- bpo-37491: Fix ``IndexError`` when parsing email headers with unexpectedly
  ending bare-quoted string value. Patch by Abhilash Raj.

- bpo-37587: Make json.loads faster for long strings. (Patch by Marco
  Paolini)

- bpo-18378: Recognize "UTF-8" as a valid value for LC_CTYPE in
  locale._parse_localename.

- bpo-37579: Return :exc:`NotImplemented` in Python implementation of
  ``__eq__`` for :class:`~datetime.timedelta` and :class:`~datetime.time`
  when the other object being compared is not of the same type to match C
  implementation. Patch by Karthikeyan Singaravelan.

- bpo-21478: Record calls to parent when autospecced object is attached to a
  mock using :func:`unittest.mock.attach_mock`. Patch by Karthikeyan
  Singaravelan.

- bpo-37531: "python3 -m test -jN --timeout=TIMEOUT" now kills a worker
  process if it runs longer than *TIMEOUT* seconds.

- bpo-37482: Fix serialization of display name in originator or destination
  address fields with both encoded words and special chars.

- bpo-36993: Improve error reporting for corrupt zip files with bad zip64
  extra data. Patch by Daniel Hillier.

- bpo-37502: pickle.loads() no longer raises TypeError when the buffers
  argument is set to None

- bpo-37520: Correct behavior for zipfile.Path.parent when the path object
  identifies a subdirectory.

- bpo-18374: Fix the ``.col_offset`` attribute of nested :class:`ast.BinOp`
  instances which had a too large value in some situations.

- bpo-37424: Fixes a possible hang when using a timeout on
  `subprocess.run()` while capturing output.  If the child process spawned
  its own children or otherwise connected its stdout or stderr handles with
  another process, we could hang after the timeout was reached and our child
  was killed when attempting to read final output from the pipes.

- bpo-37421: Fix :func:`multiprocessing.util.get_temp_dir` finalizer: clear
  also the 'tempdir' configuration of the current process, so next call to
  ``get_temp_dir()`` will create a new temporary directory, rather than
  reusing the removed temporary directory.

- bpo-37481: The distutils ``bdist_wininst`` command is deprecated in Python
  3.8, use ``bdist_wheel`` (wheel packages) instead.

- bpo-37479: When `Enum.__str__` is overridden in a derived class, the
  override will be used by `Enum.__format__` regardless of whether mixin
  classes are present.

- bpo-37440: http.client now enables TLS 1.3 post-handshake authentication
  for default context or if a cert_file is passed to HTTPSConnection.

- bpo-37437: Update vendorized expat version to 2.2.7.

- bpo-37428: SSLContext.post_handshake_auth = True no longer sets
  SSL_VERIFY_POST_HANDSHAKE verify flag for client connections. Although the
  option is documented as ignored for clients, OpenSSL implicitly enables
  cert chain validation when the flag is set.

- bpo-37420: :func:`os.sched_setaffinity` now correctly handles errors that
  arise during iteration over its ``mask`` argument. Patch by Brandt Bucher.

- bpo-37412: The :func:`os.getcwdb` function now uses the UTF-8 encoding on
  Windows, rather than the ANSI code page: see :pep:`529` for the rationale.
  The function is no longer deprecated on Windows.

- bpo-37406: The sqlite3 module now raises TypeError, rather than
  ValueError, if operation argument type is not str: execute(),
  executemany() and calling a connection.

- bpo-29412: Fix IndexError in parsing a header value ending unexpectedly.
  Patch by Abhilash Raj.

- bpo-36546: The *dist* argument for statistics.quantiles() is now
  positional only. The current name doesn't reflect that the argument can be
  either a dataset or a distribution.  Marking the parameter as positional
  avoids confusion and makes it possible to change the name later.

- bpo-37394: Fix a bug that was causing the :mod:`queue` module to fail if
  the accelerator module was not available. Patch by Pablo Galindo.

- bpo-37376: :mod:`pprint` now has support for
  :class:`types.SimpleNamespace`. Patch by Carl Bordum Hansen.

- bpo-26967: An :class:`~argparse.ArgumentParser` with
  ``allow_abbrev=False`` no longer disables grouping of short flags, such as
  ``-vv``, but only disables abbreviation of long flags as documented. Patch
  by Zac Hatfield-Dodds.

- bpo-37212: :func:`unittest.mock.call` now preserves the order of keyword
  arguments in repr output. Patch by Karthikeyan Singaravelan.

- bpo-37372: Fix error unpickling datetime.time objects from Python 2 with
  seconds>=24. Patch by Justin Blanchard.

- bpo-37345: Add formal support for UDPLITE sockets. Support was present
  before, but it is now easier to detect support with ``hasattr(socket,
  'IPPROTO_UDPLITE')`` and there are constants defined for each of the
  values needed: :py:obj:`socket.IPPROTO_UDPLITE`,
  :py:obj:`UDPLITE_SEND_CSCOV`, and :py:obj:`UDPLITE_RECV_CSCOV`. Patch by
  Gabe Appleton.

- bpo-37358: Optimized ``functools.partial`` by using vectorcall.

- bpo-37347: :meth:`sqlite3.Connection.create_aggregate`,
  :meth:`sqlite3.Connection.create_function`,
  :meth:`sqlite3.Connection.set_authorizer`,
  :meth:`sqlite3.Connection.set_progress_handler`
  :meth:`sqlite3.Connection.set_trace_callback` methods lead to segfaults if
  some of these methods are called twice with an equal object but not the
  same. Now callbacks are stored more carefully. Patch by Aleksandr Balezin.

- bpo-37163: The *obj* argument of :func:`dataclasses.replace` is
  positional-only now.

- bpo-37085: Add the optional Linux SocketCAN Broadcast Manager constants,
  used as flags to configure the BCM behaviour, in the socket module.  Patch
  by Karl Ding.

- bpo-37328: ``HTMLParser.unescape`` is removed.  It was undocumented and
  deprecated since Python 3.4.

- bpo-37305: Add .webmanifest -> application/manifest+json to list of
  recognized file types and content type headers

- bpo-37320: ``aifc.openfp()`` alias to ``aifc.open()``, ``sunau.openfp()``
  alias to ``sunau.open()``, and ``wave.openfp()`` alias to ``wave.open()``
  have been removed. They were deprecated since Python 3.7.

- bpo-37315: Deprecated accepting floats with integral value (like ``5.0``)
  in :func:`math.factorial`.

- bpo-37312: ``_dummy_thread`` and ``dummy_threading`` modules have been
  removed. These modules were deprecated since Python 3.7 which requires
  threading support.

- bpo-33972: Email with single part but content-type set to ``multipart/*``
  doesn't raise AttributeError anymore.

- bpo-37280: Use threadpool for reading from file for sendfile fallback
  mode.

- bpo-37279: Fix asyncio sendfile support when sendfile sends extra data in
  fallback mode.

- bpo-19865: :func:`ctypes.create_unicode_buffer()` now also supports
  non-BMP characters on platforms with 16-bit :c:type:`wchar_t` (for
  example, Windows and AIX).

- bpo-37266: In a subinterpreter, spawning a daemon thread now raises an
  exception. Daemon threads were never supported in subinterpreters.
  Previously, the subinterpreter finalization crashed with a Python fatal
  error if a daemon thread was still running.

- bpo-37210: Allow pure Python implementation of :mod:`pickle` to work even
  when the C :mod:`_pickle` module is unavailable.

- bpo-21872: Fix :mod:`lzma`: module decompresses data incompletely. When
  decompressing a FORMAT_ALONE format file, and it doesn't have the end
  marker, sometimes the last one to dozens bytes can't be output. Patch by
  Ma Lin.

- bpo-35922: Fix :meth:`RobotFileParser.crawl_delay` and
  :meth:`RobotFileParser.request_rate` to return ``None`` rather than raise
  :exc:`AttributeError` when no relevant rule is defined in the robots.txt
  file.  Patch by Rémi Lapeyre.

- bpo-35766: Change the format of feature_version to be a (major, minor)
  tuple.

- bpo-36607: Eliminate :exc:`RuntimeError` raised by
  :func:`asyncio.all_tasks()` if internal tasks weak set is changed by
  another thread during iteration.

- bpo-18748: :class:`_pyio.IOBase` destructor now does nothing if getting
  the ``closed`` attribute fails to better mimic :class:`_io.IOBase`
  finalizer.

- bpo-36402: Fix a race condition at Python shutdown when waiting for
  threads. Wait until the Python thread state of all non-daemon threads get
  deleted (join all non-daemon threads), rather than just wait until
  non-daemon Python threads complete.

- bpo-37206: Default values which cannot be represented as Python objects no
  longer improperly represented as ``None`` in function signatures.

- bpo-37111: Added ``encoding`` and ``errors`` keyword parameters to
  ``logging.basicConfig``.

- bpo-12144: Ensure cookies with ``expires`` attribute are handled in
  :meth:`CookieJar.make_cookies`.

- bpo-34886: Fix an unintended ValueError from :func:`subprocess.run` when
  checking for conflicting `input` and `stdin` or `capture_output` and
  `stdout` or `stderr` args when they were explicitly provided but with
  `None` values within a passed in `**kwargs` dict rather than as passed
  directly by name. Patch contributed by Rémi Lapeyre.

- bpo-37173: The exception message for ``inspect.getfile()`` now correctly
  reports the passed class rather than the builtins module.

- bpo-37178: Give math.perm() a one argument form that means the same as
  math.factorial().

- bpo-37178: For math.perm(n, k), let k default to n, giving the same result
  as factorial.

- bpo-37165: Converted _collections._count_elements to use the Argument
  Clinic.

- bpo-34767: Do not always create a :class:`collections.deque` in
  :class:`asyncio.Lock`.

- bpo-37158: Speed-up statistics.fmean() by switching from a function to a
  generator.

- bpo-34282: Remove ``Enum._convert`` method, deprecated in 3.8.

- bpo-37150: `argparse._ActionsContainer.add_argument` now throws error, if
  someone accidentally pass FileType class object instead of instance of
  FileType as `type` argument

- bpo-28724: The socket module now has the :func:`socket.send_fds` and
  :func:`socket.recv.fds` methods. Contributed by Joannah Nanjekye, Shinya
  Okano and Victor Stinner.

- bpo-35621: Support running asyncio subprocesses when execution event loop
  in a thread on UNIX.

- bpo-36520: Lengthy email headers with UTF-8 characters are now properly
  encoded when they are folded. Patch by Jeffrey Kintscher.

- bpo-30835: Fixed a bug in email parsing where a message with invalid bytes
  in content-transfer-encoding of a multipart message can cause an
  AttributeError. Patch by Andrew Donnellan.

- bpo-31163: pathlib.Path instance's rename and replace methods now return
  the new Path instance.

- bpo-25068: :class:`urllib.request.ProxyHandler` now lowercases the keys of
  the passed dictionary.

- bpo-26185: Fix :func:`repr` on empty :class:`ZipInfo` object. Patch by
  Mickaël Schoentgen.

- bpo-21315: Email headers containing RFC2047 encoded words are parsed
  despite the missing whitespace, and a defect registered. Also missing
  trailing whitespace after encoded words is now registered as a defect.

- bpo-31904: Port test_datetime to VxWorks: skip zoneinfo tests on VxWorks

- bpo-35805: Add parser for Message-ID header and add it to default
  HeaderRegistry. This should prevent folding of Message-ID using RFC 2048
  encoded words.

- bpo-36871: Ensure method signature is used instead of constructor
  signature of a class while asserting mock object against method calls.
  Patch by Karthikeyan Singaravelan.

- bpo-35070: posix.getgrouplist() now works correctly when the user belongs
  to NGROUPS_MAX supplemental groups. Patch by Jeffrey Kintscher.

- bpo-31783: Fix race condition in ThreadPoolExecutor when worker threads
  are created during interpreter shutdown.

- bpo-36582: Fix ``UserString.encode()`` to correctly return ``bytes``
  rather than a ``UserString`` instance.

- bpo-32424: Deprecate xml.etree.ElementTree.Element.copy() in favor of
  copy.copy().

  Patch by Gordon P. Hemsley

- bpo-36564: Fix infinite loop in email header folding logic that would be
  triggered when an email policy's max_line_length is not long enough to
  include the required markup and any values in the message. Patch by Paul
  Ganssle

- bpo-36543: Removed methods Element.getchildren(), Element.getiterator()
  and ElementTree.getiterator() and the xml.etree.cElementTree module.

- bpo-36409: Remove the old plistlib API deprecated in Python 3.4

- bpo-36302: distutils sorts source file lists so that Extension .so files
  build more reproducibly by default

- bpo-36250: Ignore ``ValueError`` from ``signal`` with ``interaction`` in
  non-main thread.

- bpo-36046: Added ``user``, ``group`` and ``extra_groups`` parameters to
  the subprocess.Popen constructor. Patch by Patrick McLean.

- bpo-32627: Fix compile error when ``_uuid`` headers conflicting included.

- bpo-35800: Deprecate ``smtpd.MailmanProxy`` ready for future removal.

- bpo-35168: :attr:`shlex.shlex.punctuation_chars` is now a read-only
  property.

- bpo-8538: Add support for boolean actions like ``--foo`` and ``--no-foo``
  to argparse. Patch contributed by Rémi Lapeyre.

- bpo-20504: Fixes a bug in :mod:`cgi` module when a multipart/form-data
  request has no `Content-Length` header.

- bpo-25988: The abstract base classes in :mod:`collections.abc` no longer
  are exposed in the regular :mod:`collections` module.

- bpo-11122: Distutils won't check for rpmbuild in specified paths only.

- bpo-34775: Division handling of PurePath now returns NotImplemented
  instead of raising a TypeError when passed something other than an
  instance of str or PurePath. Patch by Roger Aiudi.

- bpo-34749: :func:`binascii.a2b_base64` is now up to 2 times faster. Patch
  by Sergey Fedoseev.

- bpo-34519: Add additional aliases for HP Roman 8. Patch by Michael Osipov.

- bpo-28009: Fix uuid.getnode() on platforms with '.' as MAC Addr delimiter
  as well fix for MAC Addr format that omits a leading 0 in MAC Addr values.
  Currently, AIX is the only know platform with these settings. Patch by
  Michael Felt.

- bpo-30618: Add :meth:`~pathlib.Path.readlink`. Patch by Girts Folkmanis.

- bpo-32498: Made :func:`urllib.parse.unquote()` accept bytes in addition to
  strings. Patch by Stein Karlsen.

- bpo-33348: lib2to3 now recognizes expressions after ``*`` and `**` like in
  ``f(*[] or [])``.

- bpo-32689: Update :func:`shutil.move` function to allow for Path objects
  to be used as source argument. Patch by Emily Morehouse and Maxwell
  "5.13b" McKinnon.

- bpo-32820: Added __format__ to IPv4 and IPv6 classes.  Always outputs a
  fully zero- padded string. Supports b/x/n modifiers (bin/hex/native
  format).  Native format for IPv4 is bin, native format for IPv6 is hex.
  Also supports '#' and '_' modifiers.

- bpo-27657: Fix urllib.parse.urlparse() with numeric paths. A string like
  "path:80" is no longer parsed as a path but as a scheme ("path") and a
  path ("80").

- bpo-4963: Fixed non-deterministic behavior related to mimetypes extension
  mapping and module reinitialization.

Documentation
-------------

- bpo-21767: Explicitly mention abc support in functools.singledispatch

- bpo-38816: Provides more details about the interaction between
  :c:func:`fork` and CPython's runtime, focusing just on the C-API.  This
  includes cautions about where :c:func:`fork` should and shouldn't be
  called.

- bpo-38351: Modernize :mod:`email` examples from %-formatting to f-strings.

- bpo-38778: Document the fact that :exc:`RuntimeError` is raised if
  :meth:`os.fork` is called in a subinterpreter.

- bpo-38592: Add Brazilian Portuguese to the language switcher at Python
  Documentation website.

- bpo-38294: Add list of no-longer-escaped chars to re.escape documentation

- bpo-38053: Modernized the plistlib documentation

- bpo-26868: Fix example usage of :c:func:`PyModule_AddObject` to properly
  handle errors.

- bpo-36797: Fix a dead link in the distutils API Reference.

- bpo-37977: Warn more strongly and clearly about pickle insecurity

- bpo-37979: Added a link to dateutil.parser.isoparse in the
  datetime.fromisoformat documentation. Patch by Paul Ganssle

- bpo-12707: Deprecate info(), geturl(), getcode() methods in favor of the
  headers, url, and status properties, respectively, for HTTPResponse and
  addinfourl. Also deprecate the code attribute of addinfourl in favor of
  the status attribute. Patch by Ashwin Ramaswami

- bpo-37937: Mention ``frame.f_trace`` in :func:`sys.settrace` docs.

- bpo-37878: Make :c:func:`PyThreadState_DeleteCurrent` Internal.

- bpo-37759: Beginning edits to Whatsnew 3.8

- bpo-37726: Stop recommending getopt in the tutorial for command line
  argument parsing and promote argparse.

- bpo-32910: Remove implementation-specific behaviour of how venv's
  Deactivate works.

- bpo-37256: Fix wording of arguments for :class:`Request` in
  :mod:`urllib.request`

- bpo-37284: Add a brief note to indicate that any new
  ``sys.implementation`` required attributes must go through the PEP
  process.

- bpo-30088: Documented that :class:`mailbox.Maildir` constructor doesn't
  attempt to verify the maildir folder layout correctness. Patch by
  Sviatoslav Sydorenko.

- bpo-37521: Fix `importlib` examples to insert any newly created modules
  via importlib.util.module_from_spec() immediately into sys.modules instead
  of after calling loader.exec_module().

  Thanks to Benjamin Mintz for finding the bug.

- bpo-37456: Slash ('/') is now part of syntax.

- bpo-37487: Fix PyList_GetItem index description to include 0.

- bpo-37149: Replace the dead link to the Tkinter 8.5 reference by John
  Shipman, New Mexico Tech, with a link to the archive.org copy.

- bpo-37478: Added possible exceptions to the description of os.chdir().

- bpo-34903: Documented that in :meth:`datetime.datetime.strptime()`, the
  leading zero in some two-digit formats is optional. Patch by Mike Gleen.

- bpo-36260: Add decompression pitfalls to zipfile module documentation.

- bpo-37004: In the documentation for difflib, a note was added explicitly
  warning that the results of SequenceMatcher's ratio method may depend on
  the order of the input strings.

- bpo-36960: Restructured the :mod:`datetime` docs in the interest of making
  them more user-friendly and improving readability. Patch by Brad Solomon.

- bpo-36487: Make C-API docs clear about what the "main" interpreter is.

- bpo-23460: The documentation for decimal string formatting using the `:g`
  specifier has been updated to reflect the correct exponential notation
  cutoff point. Original patch contributed by Tuomas Suutari.

- bpo-35803: Document and test that ``tempfile`` functions may accept a
  :term:`path-like object` for the ``dir`` argument.  Patch by Anthony
  Sottile.

- bpo-33944: Added a note about the intended use of code in .pth files.

- bpo-34293: Fix the Doc/Makefile regarding PAPER environment variable and
  PDF builds

- bpo-25237: Add documentation for tkinter modules

Tests
-----

- bpo-38614: Fix test_communicate() of test_asyncio.test_subprocess: use
  ``support.LONG_TIMEOUT`` (5 minutes), instead of just 1 minute.

- bpo-38614: Add timeout constants to :mod:`test.support`:
  :data:`~test.support.LOOPBACK_TIMEOUT`,
  :data:`~test.support.INTERNET_TIMEOUT`,
  :data:`~test.support.SHORT_TIMEOUT` and
  :data:`~test.support.LONG_TIMEOUT`.

- bpo-38502: test.regrtest now uses process groups in the multiprocessing
  mode (-jN command line option) if process groups are available: if
  :func:`os.setsid` and :func:`os.killpg` functions are available.

- bpo-35998: Fix a race condition in test_asyncio.test_start_tls_server_1().
  Previously, there was a race condition between the test main() function
  which replaces the protocol and the test ServerProto protocol which sends
  ANSWER once it gets HELLO. Now, only the test main() function is
  responsible to send data, ServerProto no longer sends data.

- bpo-38470: Fix ``test_compileall.test_compile_dir_maxlevels()`` on Windows
  without long path support: only create 3 subdirectories instead of between
  20 and 100 subdirectories.

- bpo-37531: On timeout, regrtest no longer attempts to call
  ``popen.communicate()`` again: it can hang until all child processes using
  stdout and stderr pipes completes. Kill the worker process and ignores its
  output. Change also the faulthandler timeout of the main process from 1
  minute to 5 minutes, for Python slowest buildbots.

- bpo-38239: Fix test_gdb for Link Time Optimization (LTO) builds.

- bpo-38275: test_ssl now handles disabled TLS/SSL versions better.
  OpenSSL's crypto policy and run-time settings are recognized and tests for
  disabled versions are skipped. Tests also accept more TLS minimum_versions
  for platforms that override OpenSSL's default with strict settings.

- bpo-38271: The private keys for test_ssl were encrypted with 3DES in
  traditional PKCS#5 format. 3DES and the digest algorithm of PKCS#5 are
  blocked by some strict crypto policies. Use PKCS#8 format with AES256
  encryption instead.

- bpo-38270: test.support now has a helper function to check for
  availability of a hash digest function. Several tests are refactored avoid
  MD5 and use SHA256 instead. Other tests are marked to use MD5 and skipped
  when MD5 is disabled.

- bpo-37123: Multiprocessing test test_mymanager() now also expects
  -SIGTERM, not only exitcode 0. BaseManager._finalize_manager() sends
  SIGTERM to the manager process if it takes longer than 1 second to stop,
  which happens on slow buildbots.

- bpo-38212: Multiprocessing tests: increase
  test_queue_feeder_donot_stop_onexc() timeout from 1 to 60 seconds.

- bpo-38117: Test with OpenSSL 1.1.1d

- bpo-38018: Increase code coverage for multiprocessing.shared_memory.

- bpo-37805: Add tests for json.dump(..., skipkeys=True). Patch by Dong-hee
  Na.

- bpo-37531: Enhance regrtest multiprocess timeout: write a message when
  killing a worker process, catch popen.kill() and popen.wait() exceptions,
  put a timeout on the second call to popen.communicate().

- bpo-37876: Add tests for ROT-13 codec.

- bpo-36833: Added tests for PyDateTime_xxx_GET_xxx() macros of the C API of
  the :mod:`datetime` module. Patch by Joannah Nanjekye.

- bpo-37558: Fix test_shared_memory_cleaned_after_process_termination name
  handling

- bpo-37526: Add :func:`test.support.catch_threading_exception`: context
  manager catching :class:`threading.Thread` exception using
  :func:`threading.excepthook`.

- bpo-37421: test_concurrent_futures now explicitly stops the ForkServer
  instance if it's running.

- bpo-37421: multiprocessing tests now stop the ForkServer instance if it's
  running: close the "alive" file descriptor to ask the server to stop and
  then remove its UNIX address.

- bpo-37421: test_distutils.test_build_ext() is now able to remove the
  temporary directory on Windows: don't import the newly built C extension
  ("xx") in the current process, but test it in a separated process.

- bpo-37421: test_concurrent_futures now cleans up multiprocessing to remove
  immediately temporary directories created by
  multiprocessing.util.get_temp_dir().

- bpo-37421: test_winconsoleio doesn't leak a temporary file anymore: use
  tempfile.TemporaryFile() to remove it when the test completes.

- bpo-37421: multiprocessing tests now explicitly call ``_run_finalizers()``
  to immediately remove temporary directories created by tests.

- bpo-37421: urllib.request tests now call
  :func:`~urllib.request.urlcleanup` to remove temporary files created by
  ``urlretrieve()`` tests and to clear the ``_opener`` global variable set
  by ``urlopen()`` and functions calling indirectly ``urlopen()``.

- bpo-37472: Remove ``Lib/test/outstanding_bugs.py``.

- bpo-37199: Fix test failures when IPv6 is unavailable or disabled.

- bpo-19696: Replace deprecated method "random.choose" with "random.choice"
  in "test_pkg_import.py".

- bpo-37335: Remove no longer necessary code from c locale coercion tests

- bpo-37421: Fix test_shutil to no longer leak temporary files.

- bpo-37411: Fix test_wsgiref.testEnviron() to no longer depend on the
  environment variables (don't fail if "X" variable is set).

- bpo-37400: Fix test_os.test_chown(): use os.getgroups() rather than
  grp.getgrall() to get groups. Rename also the test to test_chown_gid().

- bpo-37359: Add --cleanup option to python3 -m test to remove
  ``test_python_*`` directories of previous failed jobs. Add "make
  cleantest" to run ``python3 -m test --cleanup``.

- bpo-37362: test_gdb no longer fails if it gets an "unexpected" message on
  stderr: it now ignores stderr. The purpose of test_gdb is to test that
  python-gdb.py commands work as expected, not to test gdb.

- bpo-35998: Avoid TimeoutError in test_asyncio: test_start_tls_server_1()

- bpo-37278: Fix test_asyncio ProactorLoopCtrlC: join the thread to prevent
  leaking a running thread and leaking a reference.

- bpo-37261: Fix :func:`test.support.catch_unraisable_exception`: its
  __exit__() method now ignores unraisable exception raised when clearing
  its ``unraisable`` attribute.

- bpo-37069: regrtest now uses :func:`sys.unraisablehook` to mark a test as
  "environment altered" (ENV_CHANGED) if it emits an "unraisable exception".
  Moreover, regrtest logs a warning in this case.

  Use ``python3 -m test --fail-env-changed`` to catch unraisable exceptions
  in tests.

- bpo-37252: Fix assertions in ``test_close`` and
  ``test_events_mask_overflow`` devpoll tests.

- bpo-37169: Rewrite ``_PyObject_IsFreed()`` unit tests.

- bpo-37153: ``test_venv.test_multiprocessing()`` now explicitly calls
  ``pool.terminate()`` to wait until the pool completes.

- bpo-34001: Make test_ssl pass with LibreSSL. LibreSSL handles minimum and
  maximum TLS version differently than OpenSSL.

- bpo-36919: Make ``test_source_encoding.test_issue2301`` implementation
  independent. The test will work now for both CPython and IronPython.

- bpo-30202: Update ``test.test_importlib.test_abc`` to test
  ``find_spec()``.

- bpo-28009: Modify the test_uuid logic to test when a program is available
  AND can be used to obtain a MACADDR as basis for an UUID. Patch by M. Felt

- bpo-34596: Fallback to a default reason when :func:`unittest.skip` is
  uncalled. Patch by Naitree Zhu.

Build
-----

- bpo-38809: On Windows, build scripts will now recognize and use python.exe
  from an active virtual env.

- bpo-38684: Fix _hashlib build when Blake2 is disabled, but OpenSSL
  supports it.

- bpo-38468: Misc/python-config.in now uses `getvar()` for all still
  existing `sysconfig.get_config_var()` calls. Patch by Joannah Nanjekye.

- bpo-37415: Fix stdatomic.h header check for ICC compiler: the ICC
  implementation lacks atomic_uintptr_t type which is needed by Python.

- bpo-38301: In Solaris family, we must be sure to use ``-D_REENTRANT``.
  Patch by Jesús Cea Avión.

- bpo-36002: Locate ``llvm-profdata`` and ``llvm-ar`` binaries using
  ``AC_PATH_TOOL`` rather than ``AC_PATH_TARGET_TOOL``.

- bpo-37936: The :file:`.gitignore` file systematically keeps "rooted", with
  a non-trailing slash, all the rules that are meant to apply to files in a
  specific place in the repo.  Previously, when the intended file to ignore
  happened to be at the root of the repo, we'd most often accidentally also
  ignore files and directories with the same name anywhere in the tree.

- bpo-37760: The :file:`Tools/unicode/makeunicodedata.py` script, which is
  used for converting information from the Unicode Character Database into
  generated code and data used by the methods of :class:`str` and by the
  :mod:`unicodedata` module, now handles each character's data as a
  ``dataclass`` with named attributes, rather than a length-18 list of
  different fields.

- bpo-37936: The :file:`.gitignore` file no longer applies to any files that
  are in fact tracked in the Git repository.  Patch by Greg Price.

- bpo-37725: Change "clean" makefile target to also clean the program guided
  optimization (PGO) data.  Previously you would have to use "make clean"
  and "make profile-removal", or "make clobber".

- bpo-37707: Mark some individual tests to skip when --pgo is used.  The
  tests marked increase the PGO task time significantly and likely don't
  help improve optimization of the final executable.

- bpo-36044: Reduce the number of unit tests run for the PGO generation
  task.  This speeds up the task by a factor of about 15x.  Running the full
  unit test suite is slow.  This change may result in a slightly less
  optimized build since not as many code branches will be executed.  If you
  are willing to wait for the much slower build, the old behavior can be
  restored using './configure [..] PROFILE_TASK="-m test --pgo-extended"'.
  We make no guarantees as to which PGO task set produces a faster build.
  Users who care should run their own relevant benchmarks as results can
  depend on the environment, workload, and compiler tool chain.

- bpo-37468: ``make install`` no longer installs ``wininst-*.exe`` files
  used by distutils bdist_wininst: bdist_wininst only works on Windows.

- bpo-37189: Many ``PyRun_XXX()`` functions like :c:func:`PyRun_String` were
  no longer exported in ``libpython38.dll`` by mistake. Export them again to
  fix the ABI compatibility.

- bpo-25361: Enables use of SSE2 instructions in Windows 32-bit build.

- bpo-36210: Update optional extension module detection for AIX. ossaudiodev
  and spwd are not applicable for AIX, and are no longer reported as
  missing. 3rd-party packaging of ncurses (with ASIS support) conflicts with
  officially supported AIX curses library, so configure AIX to use
  libcurses.a. However, skip trying to build _curses_panel.

  patch by M Felt

Windows
-------

- bpo-38589: Fixes HTML Help shortcut when Windows is not installed to C
  drive

- bpo-38453: Ensure ntpath.realpath() correctly resolves relative paths.

- bpo-38519: Restores the internal C headers that were missing from the
  nuget.org and Microsoft Store packages.

- bpo-38492: Remove ``pythonw.exe`` dependency on the Microsoft C++ runtime.

- bpo-38344: Fix error message in activate.bat

- bpo-38359: Ensures ``pyw.exe`` launcher reads correct registry key.

- bpo-38355: Fixes ``ntpath.realpath`` failing on ``sys.executable``.

- bpo-38117: Update bundled OpenSSL to 1.1.1d

- bpo-38092: Reduce overhead when using multiprocessing in a Windows virtual
  environment.

- bpo-38133: Allow py.exe launcher to locate installations from the
  Microsoft Store and improve display of active virtual environments.

- bpo-38114: The ``pip.ini`` is no longer included in the Nuget package.

- bpo-32592: Set Windows 8 as the minimum required version for API support

- bpo-36634: :func:`os.cpu_count` now returns active processors rather than
  maximum processors.

- bpo-36634: venv activate.bat now works when the existing variables contain
  double quote characters.

- bpo-38081: Prevent error calling :func:`os.path.realpath` on ``'NUL'``.

- bpo-38087: Fix case sensitivity in test_pathlib and test_ntpath.

- bpo-38088: Fixes distutils not finding vcruntime140.dll with only the v142
  toolset installed.

- bpo-37283: Ensure command-line and unattend.xml setting override
  previously detected states in Windows installer.

- bpo-38030: Fixes :func:`os.stat` failing for block devices on Windows

- bpo-38020: Fixes potential crash when calling :func:`os.readlink` (or
  indirectly through :func:`~os.path.realpath`) on a file that is not a
  supported link.

- bpo-37705: Improve the implementation of ``winerror_to_errno()``.

- bpo-37549: :func:`os.dup` no longer fails for standard streams on Windows
  7.

- bpo-1311: The ``nul`` file on Windows now returns True from
  :func:`~os.path.exists` and a valid result from :func:`os.stat` with
  ``S_IFCHR`` set.

- bpo-9949: Enable support for following symlinks in :func:`os.realpath`.

- bpo-37834: Treat all name surrogate reparse points on Windows in
  :func:`os.lstat` and other reparse points as regular files in
  :func:`os.stat`.

- bpo-36266: Add the module name in the formatted error message when DLL
  load fail happens during module import in
  ``_PyImport_FindSharedFuncptrWindows()``. Patch by Srinivas Nyayapati.

- bpo-25172: Trying to import the :mod:`crypt` module on Windows will result
  in an :exc:`ImportError` with a message explaining that the module isn't
  supported on Windows. On other platforms, if the underlying ``_crypt``
  module is not available, the ImportError will include a message explaining
  the problem.

- bpo-37778: Fixes the icons used for file associations to the Microsoft
  Store package.

- bpo-37734: Fix use of registry values to launch Python from Microsoft
  Store app.

- bpo-37702: Fix memory leak on Windows in creating an SSLContext object or
  running urllib.request.urlopen('https://...').

- bpo-37672: Switch Windows Store package's pip to use bundled
  :file:`pip.ini` instead of :envvar:`PIP_USER` variable.

- bpo-10945: Officially drop support for creating bdist_wininst installers
  on non-Windows systems.

- bpo-37445: Include the ``FORMAT_MESSAGE_IGNORE_INSERTS`` flag in
  ``FormatMessageW()`` calls.

- bpo-37369: Fixes path for :data:`sys.executable` when running from the
  Microsoft Store.

- bpo-37380: Don't collect unfinished processes with ``subprocess._active``
  on Windows to cleanup later. Patch by Ruslan Kuprieiev.

- bpo-37351: Removes libpython38.a from standard Windows distribution.

- bpo-35360: Update Windows builds to use SQLite 3.28.0.

- bpo-37267: On Windows, :func:`os.dup` no longer creates an inheritable fd
  when handling a character file.

- bpo-36779: Ensure ``time.tzname`` is correct on Windows when the active
  code page is set to CP_UTF7 or CP_UTF8.

- bpo-32587: Make :data:`winreg.REG_MULTI_SZ` support zero-length strings.

- bpo-28269: Replace use of :c:func:`strcasecmp` for the system function
  :c:func:`_stricmp`. Patch by Minmin Gong.

- bpo-36590: Add native Bluetooth RFCOMM support to socket module.

macOS
-----

- bpo-38117: Updated OpenSSL to 1.1.1d in macOS installer.

- bpo-38089: Move Azure Pipelines to latest VM versions and make macOS tests
  optional

- bpo-18049: Increase the default stack size of threads from 5MB to 16MB on
  macOS, to match the stack size of the main thread. This avoids crashes on
  deep recursion in threads.

- bpo-34602: Avoid test suite failures on macOS by no longer calling
  resource.setrlimit to increase the process stack size limit at runtime.
  The runtime change is no longer needed since the interpreter is being
  built with a larger default stack size.

- bpo-35360: Update macOS installer to use SQLite 3.28.0.

- bpo-34631: Updated OpenSSL to 1.1.1c in macOS installer.

IDLE
----

- bpo-26353: Stop adding newline when saving an IDLE shell window.

- bpo-4630: Add an option to toggle IDLE's cursor blink for shell, editor,
  and output windows.  See Settings, General, Window Preferences, Cursor
  Blink. Patch by Zackery Spytz.

- bpo-38598: Do not try to compile IDLE shell or output windows

- bpo-36698: IDLE no longer fails when write non-encodable characters to
  stderr.  It now escapes them with a backslash, as the regular Python
  interpreter. Added the ``errors`` field to the standard streams.

- bpo-35379: When exiting IDLE, catch any AttributeError.  One happens when
  EditorWindow.close is called twice.  Printing a traceback, when IDLE is
  run from a terminal, is useless and annoying.

- bpo-38183: To avoid problems, test_idle ignores the user config directory.
  It no longer tries to create or access .idlerc or any files within. Users
  must run IDLE to discover problems with saving settings.

- bpo-38077: IDLE no longer adds 'argv' to the user namespace when
  initializing it.  This bug only affected 3.7.4 and 3.8.0b2 to 3.8.0b4.

- bpo-38041: Shell restart lines now fill the window width, always start
  with '=', and avoid wrapping unnecessarily. The line will still wrap if
  the included file name is long relative to the width.

- bpo-35771: To avoid occasional spurious test_idle failures on slower
  machines, increase the ``hover_delay`` in test_tooltip.

- bpo-37824: Properly handle user input warnings in IDLE shell. Cease
  turning SyntaxWarnings into SyntaxErrors.

- bpo-37929: IDLE Settings dialog now closes properly when there is no shell
  window.

- bpo-37902: Add mousewheel scrolling for IDLE module, path, and stack
  browsers. Patch by George Zhang.

- bpo-37849: Fixed completions list appearing too high or low when shown
  above the current line.

- bpo-36419: Refactor IDLE autocomplete and improve testing.

- bpo-37748: Reorder the Run menu.  Put the most common choice, Run Module,
  at the top.

- bpo-37692: Improve highlight config sample with example shell interaction
  and better labels for shell elements.

- bpo-37628: Settings dialog no longer expands with font size.

- bpo-37627: Initialize the Customize Run dialog with the command line
  arguments most recently entered before.  The user can optionally edit
  before submitting them.

- bpo-33610: Fix code context not showing the correct context when first
  toggled on.

- bpo-37530: Optimize code context to reduce unneeded background activity.
  Font and highlight changes now occur along with text changes instead of
  after a random delay.

- bpo-27452: Cleanup ``config.py`` by inlining ``RemoveFile`` and
  simplifying the handling of ``file`` in ``CreateConfigHandlers``.

- bpo-37325: Fix tab focus traversal order for help source and custom run
  dialogs.

- bpo-37321: Both subprocess connection error messages now refer to the
  'Startup failure' section of the IDLE doc.

- bpo-17535: Add optional line numbers for IDLE editor windows.  Windows
  open without line numbers unless set otherwise in the General tab of the
  configuration dialog.

- bpo-26806: To compensate for stack frames added by IDLE and avoid possible
  problems with low recursion limits, add 30 to limits in the user code
  execution process.  Subtract 30 when reporting recursion limits to make
  this addition mostly transparent.

- bpo-37177: Properly 'attach' search dialogs to their main window so that
  they behave like other dialogs and do not get hidden behind their main
  window.

- bpo-37039: Adjust "Zoom Height" to individual screens by momentarily
  maximizing the window on first use with a particular screen.  Changing
  screen settings may invalidate the saved height.  While a window is
  maximized, "Zoom Height" has no effect.

- bpo-35763: Make calltip reminder about '/' meaning positional-only less
  obtrusive by only adding it when there is room on the first line.

- bpo-5680: Add 'Run... Customized' to the Run menu to run a module with
  customized settings.  Any 'command line arguments' entered are added to
  sys.argv. One can suppress the normal Shell main module restart.

- bpo-36390: Gather Format menu functions into format.py.  Combine
  paragraph.py, rstrip.py, and format methods from editor.py.

Tools/Demos
-----------

- bpo-38118: Update Valgrind suppression file to ignore a false alarm in
  :c:func:`PyUnicode_Decode` when using GCC builtin strcmp().

- bpo-38347: pathfix.py: Assume all files that end on '.py' are Python
  scripts when working recursively.

- bpo-37803: pdb's ``--help`` and ``--version`` long options now work.

- bpo-37942: Improve ArgumentClinic converter for floats.

- bpo-37704: Remove ``Tools/scripts/h2py.py``: use cffi to access a C API in
  Python.

- bpo-37675: 2to3 now works when run from a zipped standard library.

- bpo-37034: Argument Clinic now uses the argument name on errors with
  keyword-only argument instead of their position. Patch contributed by Rémi
  Lapeyre.

- bpo-37064: Add option -k to pathscript.py script: preserve shebang flags.
  Add option -a to pathscript.py script: add flags.

C API
-----

- bpo-37633: Re-export some function compatibility wrappers for macros in
  ``pythonrun.h``.

- bpo-38644: Provide :c:func:`Py_EnterRecursiveCall` and
  :c:func:`Py_LeaveRecursiveCall` as regular functions for the limited API.
  Previously, there were defined as macros, but these macros didn't work
  with the limited API which cannot access ``PyThreadState.recursion_depth``
  field. Remove ``_Py_CheckRecursionLimit`` from the stable ABI.

- bpo-38650: The global variable :c:data:`PyStructSequence_UnnamedField` is
  now a constant and refers to a constant string.

- bpo-38540: Fixed possible leak in :c:func:`PyArg_Parse` and similar
  functions for format units ``"es#"`` and ``"et#"`` when the macro
  :c:macro:`PY_SSIZE_T_CLEAN` is not defined.

- bpo-38395: Fix a crash in :class:`weakref.proxy` objects due to incorrect
  lifetime management when calling some associated methods that may delete
  the last reference to object being referenced by the proxy. Patch by Pablo
  Galindo.

- bpo-36389: The ``_PyObject_CheckConsistency()`` function is now also
  available in release mode. For example, it can be used to debug a crash in
  the ``visit_decref()`` function of the GC.

- bpo-38266: Revert the removal of PyThreadState_DeleteCurrent() with
  documentation.

- bpo-38303: Update audioop extension module to use the stable ABI
  (PEP-384). Patch by Tyler Kieft.

- bpo-38234: :c:func:`Py_SetPath` now sets :data:`sys.executable` to the
  program full path (:c:func:`Py_GetProgramFullPath`) rather than to the
  program name (:c:func:`Py_GetProgramName`).

- bpo-38234: Python ignored arguments passed to :c:func:`Py_SetPath`,
  :c:func:`Py_SetPythonHome` and :c:func:`Py_SetProgramName`: fix Python
  initialization to use specified arguments.

- bpo-38205: The :c:func:`Py_UNREACHABLE` macro now calls
  :c:func:`Py_FatalError`.

- bpo-38140: Make dict and weakref offsets opaque for C heap types by
  passing the offsets through PyMemberDef

- bpo-15088: The C function ``PyGen_NeedsFinalizing`` has been removed. It
  was not documented, tested or used anywhere within CPython after the
  implementation of :pep:`442`. Patch by Joannah Nanjekye. (Patch by Joannah
  Nanjekye)

- bpo-36763: Options added by ``PySys_AddXOption()`` are now handled the
  same way than ``PyConfig.xoptions`` and command line ``-X`` options.

- bpo-37926: Fix a crash in ``PySys_SetArgvEx(0, NULL, 0)``.

- bpo-37879: Fix subtype_dealloc to suppress the type decref when the base
  type is a C heap type

- bpo-37645: Add :c:func:`_PyObject_FunctionStr` to get a user-friendly
  string representation of a function-like object. Patch by Jeroen Demeyer.

- bpo-29548: The functions ``PyEval_CallObject``, ``PyEval_CallFunction``,
  ``PyEval_CallMethod`` and ``PyEval_CallObjectWithKeywords`` are
  deprecated. Use :c:func:`PyObject_Call` and its variants instead.

- bpo-37151: ``PyCFunction_Call`` is now a deprecated alias of
  :c:func:`PyObject_Call`.

- bpo-37540: The vectorcall protocol now requires that the caller passes
  only strings as keyword names.

- bpo-37207: The vectorcall protocol is now enabled for ``type`` objects:
  set ``tp_vectorcall`` to a vectorcall function to be used instead of
  ``tp_new`` and ``tp_init`` when calling the class itself.

- bpo-21120: Exclude Python-ast.h, ast.h and asdl.h from the limited API.

- bpo-37483: Add new function ``_PyObject_CallOneArg`` for calling an object
  with one positional argument.

- bpo-36763: Add :func:`PyConfig_SetWideStringList` function.

- bpo-37337: Add fast functions for calling methods:
  :c:func:`_PyObject_VectorcallMethod`, :c:func:`_PyObject_CallMethodNoArgs`
  and :c:func:`_PyObject_CallMethodOneArg`.

- bpo-28805: The :const:`METH_FASTCALL` calling convention has been
  documented.

- bpo-37221: The new function :c:func:`PyCode_NewWithPosOnlyArgs` allows to
  create code objects like :c:func:`PyCode_New`, but with an extra
  *posonlyargcount* parameter for indicating the number of positonal-only
  arguments.

- bpo-37215: Fix dtrace issue introduce by bpo-36842

- bpo-37194: Add a new public :c:func:`PyObject_CallNoArgs` function to the
  C API: call a callable Python object without any arguments. It is the most
  efficient way to call a callback without any argument. On x86-64, for
  example, ``PyObject_CallFunctionObjArgs(func, NULL)`` allocates 960 bytes
  on the stack per call, whereas ``PyObject_CallNoArgs(func)`` only
  allocates 624 bytes per call.

- bpo-37170: Fix the cast on error in
  :c:func:`PyLong_AsUnsignedLongLongMask()`.

- bpo-35381: Convert posixmodule.c statically allocated types
  ``DirEntryType`` and ``ScandirIteratorType`` to heap-allocated types.

- bpo-34331: Use singular/plural noun in error message when instantiating an
  abstract class with non-overriden abstract method(s).


What's New in Python 3.8.0 beta 1?
==================================

*Release date: 2019-06-04*

Security
--------

- bpo-35907: CVE-2019-9948: Avoid file reading by disallowing
  ``local-file://`` and ``local_file://`` URL schemes in
  ``URLopener().open()`` and ``URLopener().retrieve()`` of
  :mod:`urllib.request`.

- bpo-33529: Prevent fold function used in email header encoding from
  entering infinite loop when there are too many non-ASCII characters in a
  header.

- bpo-33164: Updated blake2 implementation which uses secure memset
  implementation provided by platform.

Core and Builtins
-----------------

- bpo-35814: Allow unpacking in the right hand side of annotated
  assignments. In particular, ``t: Tuple[int, ...] = x, y, *z`` is now
  allowed.

- bpo-37126: All structseq objects are now tracked by the garbage collector.
  Patch by Pablo Galindo.

- bpo-37122: Make the *co_argcount* attribute of code objects represent the
  total number of positional arguments (including positional-only
  arguments). The value of *co_posonlyargcount* can be used to distinguish
  which arguments are positional only, and the difference (*co_argcount* -
  *co_posonlyargcount*) is the number of positional-or-keyword arguments.
  Patch by Pablo Galindo.

- bpo-20092: Constructors of :class:`int`, :class:`float` and
  :class:`complex` will now use the :meth:`~object.__index__` special
  method, if available and the corresponding method :meth:`~object.__int__`,
  :meth:`~object.__float__` or :meth:`~object.__complex__` is not available.

- bpo-37087: Add native thread ID (TID) support to OpenBSD.

- bpo-26219: Implemented per opcode cache mechanism and ``LOAD_GLOBAL``
  instruction use it. ``LOAD_GLOBAL`` is now about 40% faster. Contributed
  by Yury Selivanov, and Inada Naoki.

- bpo-37072: Fix crash in PyAST_FromNodeObject() when flags is NULL.

- bpo-37029: Freeing a great many small objects could take time quadratic in
  the number of arenas, due to using linear search to keep ``obmalloc.c``'s
  list of usable arenas sorted by order of number of free memory pools.
  This is accomplished without search now, leaving the worst-case time
  linear in the number of arenas.  For programs where this quite visibly
  matters (typically with more than 100 thousand small objects alive
  simultaneously), this can greatly reduce the time needed to release their
  memory.

- bpo-26423: Fix possible overflow in ``wrap_lenfunc()`` when ``sizeof(long)
  < sizeof(Py_ssize_t)`` (e.g., 64-bit Windows).

- bpo-37050: Improve the AST for "debug" f-strings, which use '=' to print
  out the source of the expression being evaluated.  Delete expr_text from
  the FormattedValue node, and instead use a Constant string node (possibly
  merged with adjacent constant expressions inside the f-string).

- bpo-22385: The `bytes.hex`, `bytearray.hex`, and `memoryview.hex` methods
  as well as the `binascii.hexlify` and `b2a_hex` functions now have the
  ability to include an optional separator between hex bytes.  This
  functionality was inspired by MicroPython's hexlify implementation.

- bpo-26836: Add :func:`os.memfd_create`.

- bpo-37032: Added new ``replace()`` method to the code type
  (:class:`types.CodeType`).

- bpo-37007: Implement :func:`socket.if_nameindex()`,
  :func:`socket.if_nametoindex()`, and :func:`socket.if_indextoname()` on
  Windows.

- bpo-36829: :c:func:`PyErr_WriteUnraisable` now creates a traceback object
  if there is no current traceback. Moreover, call
  :c:func:`PyErr_NormalizeException` and :c:func:`PyException_SetTraceback`
  to normalize the exception value. Ignore any error.

- bpo-36878: Only accept text after `# type: ignore` if the first character
  is ASCII. This is to disallow things like `# type: ignoreé`.

- bpo-36878: Store text appearing after a `# type: ignore` comment in the
  AST. For example a type ignore like `# type: ignore[E1000]` will have the
  string `"[E1000]"` stored in its AST node.

- bpo-2180: Treat line continuation at EOF as a ``SyntaxError`` by Anthony
  Sottile.

- bpo-36907: Fix a crash when calling a C function with a keyword dict
  (``f(**kwargs)``) and changing the dict ``kwargs`` while that function is
  running.

- bpo-36946: Fix possible signed integer overflow when handling slices.

- bpo-36826: Add NamedExpression kind support to ast_unparse.c

- bpo-1875: A :exc:`SyntaxError` is now raised if a code blocks that will be
  optimized away (e.g. if conditions that are always false) contains syntax
  errors. Patch by Pablo Galindo.

- bpo-36027: Allow computation of modular inverses via three-argument
  ``pow``: the second argument is now permitted to be negative in the case
  where the first and third arguments are relatively prime.

- bpo-36861: Update the Unicode database to version 12.1.0.

- bpo-28866: Avoid caching attributes of classes which type defines mro() to
  avoid a hard cache invalidation problem.

- bpo-36851: The ``FrameType`` stack is now correctly cleaned up if the
  execution ends with a return and the stack is not empty.

- bpo-34616: The ``compile()`` builtin functions now support the
  ``ast.PyCF_ALLOW_TOP_LEVEL_AWAIT`` flag,  which allow to compile sources
  that  contains top-level ``await``, ``async with`` or ``async for``. This
  is useful to evaluate async-code from with an already async functions; for
  example in a custom REPL.

- bpo-36842: Implement PEP 578, adding sys.audit, io.open_code and related
  APIs.

- bpo-27639: Correct return type for UserList slicing operations. Patch by
  Michael Blahay, Erick Cervantes, and vaultah

- bpo-36737: Move PyRuntimeState.warnings into per-interpreter state (via
  "module state").

- bpo-36793: Removed ``__str__`` implementations from builtin types
  :class:`bool`, :class:`int`, :class:`float`, :class:`complex` and few
  classes from the standard library. They now inherit ``__str__()`` from
  :class:`object`.

- bpo-36817: Add a ``=`` feature f-strings for debugging. This can precede
  ``!s``, ``!r``, or ``!a``. It produces the text of the expression,
  followed by an equal sign, followed by the repr of the value of the
  expression. So ``f'{3*9+15=}'`` would be equal to the string
  ``'3*9+15=42'``.  If ``=`` is specified, the default conversion is set to
  ``!r``, unless a format spec is given, in which case the formatting
  behavior is unchanged, and __format__ will be used.

- bpo-24048: Save the live exception during import.c's ``remove_module()``.

- bpo-27987: pymalloc returns memory blocks aligned by 16 bytes, instead of
  8 bytes, on 64-bit platforms to conform x86-64 ABI. Recent compilers
  assume this alignment more often. Patch by Inada Naoki.

- bpo-36601: A long-since-meaningless check for ``getpid() == main_pid`` was
  removed from Python's internal C signal handler.

- bpo-36594: Fix incorrect use of ``%p`` in format strings. Patch by Zackery
  Spytz.

- bpo-36045: builtins.help() now prefixes `async` for async functions

- bpo-36084: Add native thread ID (TID) to threading.Thread objects
  (supported platforms: Windows, FreeBSD, Linux, macOS)

- bpo-36035: Added fix for broken symlinks in combination with pathlib

- bpo-35983: Added new trashcan macros to deal with a double deallocation
  that could occur when the `tp_dealloc` of a subclass calls the
  `tp_dealloc` of a base class and that base class uses the trashcan
  mechanism. Patch by Jeroen Demeyer.

- bpo-20602: Do not clear :data:`sys.flags` and :data:`sys.float_info`
  during shutdown. Patch by Zackery Spytz.

- bpo-26826: Expose :func:`copy_file_range` as a low level API in the
  :mod:`os` module.

- bpo-32388: Remove cross-version binary compatibility requirement in
  tp_flags.

- bpo-31862: Port binascii to PEP 489 multiphase initialization. Patch by
  Marcel Plch.

Library
-------

- bpo-37128: Added :func:`math.perm`.

- bpo-37120: Add SSLContext.num_tickets to control the number of TLSv1.3
  session tickets.

- bpo-12202: Fix the error handling in
  :meth:`msilib.SummaryInformation.GetProperty`. Patch by Zackery Spytz.

- bpo-26835: The fcntl module now contains file sealing constants for
  sealing of memfds.

- bpo-29262: Add ``get_origin()`` and ``get_args()`` introspection helpers
  to ``typing`` module.

- bpo-12639: :meth:`msilib.Directory.start_component()` no longer fails if
  *keyfile* is not ``None``.

- bpo-36999: Add the ``asyncio.Task.get_coro()`` method to publicly expose
  the tasks's coroutine object.

- bpo-35246: Make :func:`asyncio.create_subprocess_exec` accept path-like
  arguments.

- bpo-35279: Change default *max_workers* of ``ThreadPoolExecutor`` from
  ``cpu_count() * 5`` to ``min(32, cpu_count() + 4)``.  Previous value was
  unreasonably large on many cores machines.

- bpo-37076: :func:`_thread.start_new_thread` now logs uncaught exception
  raised by the function using :func:`sys.unraisablehook`, rather than
  :func:`sys.excepthook`, so the hook gets access to the function which
  raised the exception.

- bpo-33725: On macOS, the :mod:`multiprocessing` module now uses *spawn*
  start method by default.

- bpo-37054: Fix destructor :class:`_pyio.BytesIO` and
  :class:`_pyio.TextIOWrapper`: initialize their ``_buffer`` attribute as
  soon as possible (in the class body), because it's used by ``__del__()``
  which calls ``close()``.

- bpo-37058: PEP 544: Add ``Protocol`` and ``@runtime_checkable`` to the
  ``typing`` module.

- bpo-36933: The functions ``sys.set_coroutine_wrapper`` and
  ``sys.get_coroutine_wrapper`` that were deprecated and marked for removal
  in 3.8 have been removed.

- bpo-37047: Handle late binding and attribute access in
  :class:`unittest.mock.AsyncMock` setup for autospeccing. Document newly
  implemented async methods in :class:`unittest.mock.MagicMock`.

- bpo-37049: PEP 589: Add ``TypedDict`` to the ``typing`` module.

- bpo-37046: PEP 586: Add ``Literal`` to the ``typing`` module.

- bpo-37045: PEP 591: Add ``Final`` qualifier and ``@final`` decorator to
  the ``typing`` module.

- bpo-37035: Don't log OSError based exceptions if a fatal error has
  occurred in asyncio transport. Peer can generate almost any OSError, user
  cannot avoid these exceptions by fixing own code. Errors are still
  propagated to user code, it's just logging them is pointless and pollute
  asyncio logs.

- bpo-37001: :func:`symtable.symtable` now accepts the same input types for
  source code as the built-in :func:`compile` function. Patch by Dino
  Viehland.

- bpo-37028: Implement asyncio REPL

- bpo-37027: Return safe to use proxy socket object from
  transport.get_extra_info('socket')

- bpo-32528: Make asyncio.CancelledError a BaseException.

  This will address the common mistake many asyncio users make: an "except
  Exception" clause breaking Tasks cancellation.

  In addition to this change, we stop inheriting asyncio.TimeoutError and
  asyncio.InvalidStateError from their concurrent.futures.* counterparts.
  There's no point for these exceptions to share the inheritance chain.

- bpo-1230540: Add a new :func:`threading.excepthook` function which handles
  uncaught :meth:`threading.Thread.run` exception. It can be overridden to
  control how uncaught :meth:`threading.Thread.run` exceptions are handled.

- bpo-36996: Handle :func:`unittest.mock.patch` used as a decorator on async
  functions.

- bpo-37008: Add support for calling :func:`next` with the mock resulting
  from :func:`unittest.mock.mock_open`

- bpo-27737: Allow whitespace only header encoding in ``email.header`` - by
  Batuhan Taskaya

- bpo-36969: PDB command `args` now  display positional only arguments.
  Patch contributed by Rémi Lapeyre.

- bpo-36969: PDB command `args` now  display keyword only arguments. Patch
  contributed by Rémi Lapeyre.

- bpo-36983: Add missing names to ``typing.__all__``: ``ChainMap``,
  ``ForwardRef``, ``OrderedDict`` - by Anthony Sottile.

- bpo-36972: Add SupportsIndex protocol to the typing module to allow type
  checking to detect classes that can be passed to `hex()`, `oct()` and
  `bin()`.

- bpo-32972: Implement ``unittest.IsolatedAsyncioTestCase`` to help testing
  asyncio-based code.

- bpo-36952: :func:`fileinput.input` and :class:`fileinput.FileInput`
  **bufsize** argument has been removed (was deprecated and ignored since
  Python 3.6), and as a result the **mode** and **openhook** arguments have
  been made keyword-only.

- bpo-36952: Starting with Python 3.3, importing ABCs from
  :mod:`collections` is deprecated, and import should be done from
  :mod:`collections.abc`. Still being able to import from :mod:`collections`
  was marked for removal in 3.8, but has been delayed to 3.9; documentation
  and ``DeprecationWarning`` clarified.

- bpo-36949: Implement __repr__ for WeakSet objects.

- bpo-36948: Fix :exc:`NameError` in
  :meth:`urllib.request.URLopener.retrieve`. Patch by Karthikeyan
  Singaravelan.

- bpo-33524: Fix the folding of email header when the max_line_length is 0
  or None and the header contains non-ascii characters.  Contributed by
  Licht Takeuchi (@Licht-T).

- bpo-24564: :func:`shutil.copystat` now ignores :const:`errno.EINVAL` on
  :func:`os.setxattr` which may occur when copying files on filesystems
  without extended attributes support.

  Original patch by Giampaolo Rodola, updated by Ying Wang.

- bpo-36888: Python child processes can now access the status of their
  parent process using multiprocessing.process.parent_process

- bpo-36921: Deprecate ``@coroutine`` for sake of ``async def``.

- bpo-25652: Fix bug in ``__rmod__`` of ``UserString`` - by Batuhan Taskaya.

- bpo-36916: Remove a message about an unhandled exception in a task when
  writer.write() is used without await and writer.drain() fails with an
  exception.

- bpo-36889: Introduce :class:`asyncio.Stream` class that merges
  :class:`asyncio.StreamReader` and :class:`asyncio.StreamWriter`
  functionality. :class:`asyncio.Stream` can work in readonly, writeonly and
  readwrite modes. Provide :func:`asyncio.connect`,
  :func:`asyncio.connect_unix`, :func:`asyncio.connect_read_pipe` and
  :func:`asyncio.connect_write_pipe` factories to open
  :class:`asyncio.Stream` connections. Provide :class:`asyncio.StreamServer`
  and :class:`UnixStreamServer` to serve servers with asyncio.Stream API.
  Modify :func:`asyncio.create_subprocess_shell` and
  :func:`asyncio.create_subprocess_exec` to use :class:`asyncio.Stream`
  instead of deprecated :class:`StreamReader` and :class:`StreamWriter`.
  Deprecate :class:`asyncio.StreamReader` and :class:`asyncio.StreamWriter`.
  Deprecate usage of private classes, e.g.
  :class:`asyncio.FlowControlMixing` and
  :class:`asyncio.StreamReaderProtocol` outside of asyncio package.

- bpo-36845: Added validation of integer prefixes to the construction of IP
  networks and interfaces in the ipaddress module.

- bpo-23378: Add an extend action to argparser.

- bpo-36867: Fix a bug making a SharedMemoryManager instance and its parent
  process use two separate resource_tracker processes.

- bpo-23896: Adds a grammar to lib2to3.pygram that contains exec as a
  function not as statement.

- bpo-36895: The function ``time.clock()`` was deprecated in 3.3 in favor of
  ``time.perf_counter()`` and marked for removal in 3.8, it has removed.

- bpo-35545: Fix asyncio discarding IPv6 scopes when ensuring hostname
  resolutions internally

- bpo-36887: Add new function :func:`math.isqrt` to compute integer square
  roots.

- bpo-34632: Introduce the ``importlib.metadata`` module with (provisional)
  support for reading metadata from third-party packages.

- bpo-36878: When using `type_comments=True` in `ast.parse`, treat `# type:
  ignore` followed by a non-alphanumeric character and then arbitrary text
  as a type ignore, instead of requiring nothing but whitespace or another
  comment. This is to permit formations such as `# type: ignore[E1000]`.

- bpo-36778: ``cp65001`` encoding (Windows code page 65001) becomes an alias
  to ``utf_8`` encoding.

- bpo-36867: The multiprocessing.resource_tracker replaces the
  multiprocessing.semaphore_tracker module. Other than semaphores,
  resource_tracker also tracks shared_memory segments.

- bpo-30262: The ``Cache`` and ``Statement`` objects of the :mod:`sqlite3`
  module are not exposed to the user.  Patch by Aviv Palivoda.

- bpo-24538: In `shutil.copystat()`, first copy extended file attributes and
  then file permissions, since extended attributes can only be set on the
  destination while it is still writeable.

- bpo-36829: Add new :func:`sys.unraisablehook` function which can be
  overridden to control how "unraisable exceptions" are handled. It is
  called when an exception has occurred but there is no way for Python to
  handle it. For example, when a destructor raises an exception or during
  garbage collection (:func:`gc.collect`).

- bpo-36832: Introducing ``zipfile.Path``, a pathlib-compatible wrapper for
  traversing zip files.

- bpo-36814: Fix an issue where os.posix_spawnp() would incorrectly raise a
  TypeError when file_actions is None.

- bpo-33110: Handle exceptions raised by functions added by
  concurrent.futures add_done_callback correctly when the Future has already
  completed.

- bpo-26903: Limit `max_workers` in `ProcessPoolExecutor` to 61 to work
  around a WaitForMultipleObjects limitation.

- bpo-36813: Fix :class:`~logging.handlers.QueueListener` to call
  ``queue.task_done()`` upon stopping. Patch by Bar Harel.

- bpo-36806: Forbid creation of asyncio stream objects like StreamReader,
  StreamWriter, Process, and their protocols outside of asyncio package.

- bpo-36802: Provide both sync and async calls for StreamWriter.write() and
  StreamWriter.close()

- bpo-36801: Properly handle SSL connection closing in asyncio
  StreamWriter.drain() call.

- bpo-36785: Implement PEP 574 (pickle protocol 5 with out-of-band buffers).

- bpo-36772: functools.lru_cache() can now be used as a straight decorator
  in addition to its existing usage as a function that returns a decorator.

- bpo-6584: Add a :exc:`~gzip.BadGzipFile` exception to the :mod:`gzip`
  module.

- bpo-36748: Optimized write buffering in C implementation of
  ``TextIOWrapper``. Writing ASCII string to ``TextIOWrapper`` with ascii,
  latin1, or utf-8 encoding is about 20% faster.  Patch by Inada Naoki.

- bpo-8138: Don't mark ``wsgiref.simple_server.SimpleServer`` as
  multi-threaded since ``wsgiref.simple_server.WSGIServer`` is
  single-threaded.

- bpo-22640: :func:`py_compile.compile` now supports silent mode. Patch by
  Joannah Nanjekye

- bpo-29183: Fix double exceptions in :class:`wsgiref.handlers.BaseHandler`
  by calling its :meth:`~wsgiref.handlers.BaseHandler.close` method only
  when no exception is raised.

- bpo-36548: Improved the repr of regular expression flags.

- bpo-36542: The signature of Python functions can now be overridden by
  specifying the ``__text_signature__`` attribute.

- bpo-36533: Reinitialize logging.Handler locks in forked child processes
  instead of attempting to acquire them all in the parent before forking
  only to be released in the child process.  The acquire/release pattern was
  leading to deadlocks in code that has implemented any form of chained
  logging handlers that depend upon one another as the lock acquisition
  order cannot be guaranteed.

- bpo-35252: Throw a TypeError instead of an AssertionError when using an
  invalid type annotation with singledispatch.

- bpo-35900: Allow reduction methods to return a 6-item tuple where the 6th
  item specifies a custom state-setting method that's called instead of the
  regular ``__setstate__`` method.

- bpo-35900: enable custom reduction callback registration for functions and
  classes in _pickle.c, using the new Pickler's attribute
  ``reducer_override``

- bpo-36368: Fix a bug crashing SharedMemoryManager instances in interactive
  sessions after a ctrl-c (KeyboardInterrupt) was sent

- bpo-31904: Fix mmap fail for VxWorks

- bpo-27497: :meth:`csv.DictWriter.writeheader` now returns the return value
  of the underlying :meth:`csv.Writer.writerow` method. Patch contributed by
  Ashish Nitin Patil.

- bpo-36239: Parsing .mo files now ignores comments starting and ending with
  #-#-#-#-#.

- bpo-26707: Enable plistlib to read and write binary plist files that were
  created as a KeyedArchive file. Specifically, this allows the plistlib to
  process 0x80 tokens as UID objects.

- bpo-31904: Add posix module support for VxWorks.

- bpo-35125: Asyncio: Remove inner callback on outer cancellation in shield

- bpo-35721: Fix :meth:`asyncio.SelectorEventLoop.subprocess_exec()` leaks
  file descriptors if ``Popen`` fails and called with
  ``stdin=subprocess.PIPE``. Patch by Niklas Fiekas.

- bpo-31855: :func:`unittest.mock.mock_open` results now respects the
  argument of read([size]). Patch contributed by Rémi Lapeyre.

- bpo-35431: Implement :func:`math.comb` that returns binomial coefficient,
  that computes the number of ways to choose k items from n items without
  repetition and without order. Patch by Yash Aggarwal and Keller Fuchs.

- bpo-26660: Fixed permission errors in
  :class:`~tempfile.TemporaryDirectory` clean up. Previously
  ``TemporaryDirectory.cleanup()`` failed when non-writeable or
  non-searchable files or directories were created inside a temporary
  directory.

- bpo-34271: Add debugging helpers to ssl module. It's now possible to dump
  key material and to trace TLS protocol. The default and stdlib contexts
  also support SSLKEYLOGFILE env var.

- bpo-26467: Added AsyncMock to support using unittest to mock asyncio
  coroutines. Patch by Lisa Roach.

- bpo-33569: dataclasses.InitVar: Exposes the type used to create the init
  var.

- bpo-34424: Fix serialization of messages containing encoded strings when
  the policy.linesep is set to a multi-character string. Patch by Jens
  Troeger.

- bpo-34303: Performance of :func:`functools.reduce` is slightly improved.
  Patch by Sergey Fedoseev.

- bpo-33361: Fix a bug in :class:`codecs.StreamRecoder` where seeking might
  leave old data in a buffer and break subsequent read calls. Patch by Ammar
  Askar.

- bpo-22454: The :mod:`shlex` module now exposes :func:`shlex.join`, the
  inverse of :func:`shlex.split`. Patch by Bo Bayles.

- bpo-31922: :meth:`asyncio.AbstractEventLoop.create_datagram_endpoint`: Do
  not connect UDP socket when broadcast is allowed. This allows to receive
  replies after a UDP broadcast.

- bpo-24882: Change ThreadPoolExecutor to use existing idle threads before
  spinning up new ones.

- bpo-31961: Added support for bytes and path-like objects in
  :func:`subprocess.Popen` on Windows.  The *args* parameter now accepts a
  :term:`path-like object` if *shell* is ``False`` and a sequence containing
  bytes and path-like objects. The *executable* parameter now accepts a
  bytes and :term:`path-like object`. The *cwd* parameter now accepts a
  bytes object. Based on patch by Anders Lorentsen.

- bpo-33123: :class:`pathlib.Path.unlink` now accepts a *missing_ok*
  parameter to avoid a :exc:`FileNotFoundError` from being raised. Patch by
  Robert Buchholz.

- bpo-32941: Allow :class:`mmap.mmap` objects to access the madvise() system
  call (through :meth:`mmap.mmap.madvise`).

- bpo-22102: Added support for ZIP files with disks set to 0. Such files are
  commonly created by builtin tools on Windows when use ZIP64 extension.
  Patch by Francisco Facioni.

- bpo-32515: trace.py can now run modules via python3 -m trace -t --module
  module_name

- bpo-32299: Changed :func:`unittest.mock.patch.dict` to return the patched
  dictionary when used as context manager. Patch by Vadim Tsander.

- bpo-27141: Added a ``__copy__()`` to ``collections.UserList`` and
  ``collections.UserDict`` in order to correctly implement shallow copying
  of the objects. Patch by Bar Harel.

- bpo-31829: ``\r``, ``\0`` and ``\x1a`` (end-of-file on Windows) are now
  escaped in protocol 0 pickles of Unicode strings. This allows to load them
  without loss from files open in text mode in Python 2.

- bpo-23395: ``_thread.interrupt_main()`` now avoids setting the Python
  error status if the ``SIGINT`` signal is ignored or not handled by Python.

Documentation
-------------

- bpo-36896: Clarify that some types have unstable constructor signature
  between Python versions.

- bpo-36686: Improve documentation of the stdin, stdout, and stderr
  arguments of the ``asyncio.subprocess_exec`` function to specify which
  values are supported. Also mention that decoding as text is not supported.

  Add a few tests to verify that the various values passed to the std*
  arguments actually work.

- bpo-36984: Improve version added references in ``typing`` module - by
  Anthony Sottile.

- bpo-36868: What's new now mentions SSLContext.hostname_checks_common_name
  instead of SSLContext.host_flags.

- bpo-35924: Add a note to the ``curses.addstr()`` documentation to warn
  that multiline strings can cause segfaults because of an ncurses bug.

- bpo-36783: Added C API Documentation for Time_FromTimeAndFold and
  PyDateTime_FromDateAndTimeAndFold as per PEP 495. Patch by Edison
  Abahurire.

- bpo-36797: More of the legacy distutils documentation has been either
  pruned, or else more clearly marked as being retained solely until the
  setuptools documentation covers it independently.

- bpo-22865: Add detail to the documentation on the `pty.spawn` function.

- bpo-35397: Remove deprecation and document urllib.parse.unwrap(). Patch
  contributed by Rémi Lapeyre.

- bpo-32995: Added the context variable in glossary.

- bpo-33519: Clarify that `copy()` is not part of the `MutableSequence` ABC.

- bpo-33482: Make `codecs.StreamRecoder.writelines` take a list of bytes.

- bpo-25735: Added documentation for func factorial to indicate that returns
  integer values

- bpo-20285: Expand object.__doc__ (docstring) to make it clearer. Modify
  pydoc.py so that help(object) lists object methods (for other classes,
  help omits methods of the object base class.)

Tests
-----

- bpo-37069: Modify test_coroutines, test_cprofile, test_generators,
  test_raise, test_ssl and test_yield_from to use
  :func:`test.support.catch_unraisable_exception` rather than
  :func:`test.support.captured_stderr`.

- bpo-37098: Fix test_memfd_create on older Linux Kernels.

- bpo-37081: Test with OpenSSL 1.1.1c

- bpo-36829: Add :func:`test.support.catch_unraisable_exception`: context
  manager catching unraisable exception using :func:`sys.unraisablehook`.

- bpo-36915: The main regrtest process now always removes all temporary
  directories of worker processes even if they crash or if they are killed
  on KeyboardInterrupt (CTRL+c).

- bpo-36719: "python3 -m test -jN ..." now continues the execution of next
  tests when a worker process crash (CHILD_ERROR state). Previously, the
  test suite stopped immediately. Use --failfast to stop at the first error.

- bpo-36816: Update Lib/test/selfsigned_pythontestdotnet.pem to match
  self-signed.pythontest.net's new TLS certificate.

- bpo-35925: Skip httplib and nntplib networking tests when they would
  otherwise fail due to a modern OS or distro with a default OpenSSL policy
  of rejecting connections to servers with weak certificates.

- bpo-36782: Add tests for several C API functions in the :mod:`datetime`
  module. Patch by Edison Abahurire.

- bpo-36342: Fix test_multiprocessing in test_venv if platform lacks
  functioning sem_open.

Build
-----

- bpo-36721: To embed Python into an application, a new ``--embed`` option
  must be passed to ``python3-config --libs --embed`` to get ``-lpython3.8``
  (link the application to libpython). To support both 3.8 and older, try
  ``python3-config --libs --embed`` first and fallback to ``python3-config
  --libs`` (without ``--embed``) if the previous command fails.

  Add a pkg-config ``python-3.8-embed`` module to embed Python into an
  application: ``pkg-config python-3.8-embed --libs`` includes
  ``-lpython3.8``. To support both 3.8 and older, try ``pkg-config
  python-X.Y-embed --libs`` first and fallback to ``pkg-config python-X.Y
  --libs`` (without ``--embed``) if the previous command fails (replace
  ``X.Y`` with the Python version).

  On the other hand, ``pkg-config python3.8 --libs`` no longer contains
  ``-lpython3.8``. C extensions must not be linked to libpython (except on
  Android, case handled by the script); this change is backward incompatible
  on purpose.

- bpo-36786: "make install" now runs compileall in parallel.

Windows
-------

- bpo-36965: include of STATUS_CONTROL_C_EXIT without depending on MSC
  compiler

- bpo-35926: Update to OpenSSL 1.1.1b for Windows.

- bpo-29883: Add Windows support for UDP transports for the Proactor Event
  Loop. Patch by Adam Meily.

- bpo-33407: The :c:macro:`Py_DEPRECATED()` macro has been implemented for
  MSVC.

macOS
-----

- bpo-36231: Support building Python on macOS without /usr/include
  installed. As of macOS 10.14, system header files are only available
  within an SDK provided by either the Command Line Tools or the Xcode app.

IDLE
----

- bpo-35610: Replace now redundant .context_use_ps1 with .prompt_last_line.
  This finishes change started in bpo-31858.

- bpo-37038: Make idlelib.run runnable; add test clause.

- bpo-36958: Print any argument other than None or int passed to SystemExit
  or sys.exit().

- bpo-36807: When saving a file, call os.fsync() so bits are flushed to e.g.
  USB drive.

- bpo-32411: In browser.py, remove extraneous sorting by line number since
  dictionary was created in line number order.

Tools/Demos
-----------

- bpo-37053: Handle strings like u"bar" correctly in
  Tools/parser/unparse.py. Patch by Chih-Hsuan Yen.

C API
-----

- bpo-36763: Implement the :pep:`587` "Python Initialization Configuration".

- bpo-36379: Fix crashes when attempting to use the *modulo* parameter when
  ``__ipow__`` is implemented in C.

- bpo-37107: Update :c:func:`PyObject_CallMethodObjArgs` and
  ``_PyObject_CallMethodIdObjArgs`` to use ``_PyObject_GetMethod`` to avoid
  creating a bound method object in many cases. Patch by Michael J.
  Sullivan.

- bpo-36974: Implement :pep:`590`: Vectorcall: a fast calling protocol for
  CPython. This is a new protocol to optimize calls of custom callable
  objects.

- bpo-36763: ``Py_Main()`` now returns the exitcode rather than calling
  ``Py_Exit(exitcode)`` when calling ``PyErr_Print()`` if the current
  exception type is ``SystemExit``.

- bpo-36922: Add new type flag ``Py_TPFLAGS_METHOD_DESCRIPTOR`` for objects
  behaving like unbound methods. These are objects supporting the
  optimization given by the ``LOAD_METHOD``/``CALL_METHOD`` opcodes. See PEP
  590.

- bpo-36728: The :c:func:`PyEval_ReInitThreads` function has been removed
  from the C API. It should not be called explicitly: use
  :c:func:`PyOS_AfterFork_Child` instead.


What's New in Python 3.8.0 alpha 4?
===================================

*Release date: 2019-05-06*

Security
--------

- bpo-36742: Fixes mishandling of pre-normalization characters in
  urlsplit().

- bpo-30458: Address CVE-2019-9740 by disallowing URL paths with embedded
  whitespace or control characters through into the underlying http client
  request.  Such potentially malicious header injection URLs now cause an
  http.client.InvalidURL exception to be raised.

- bpo-35755: :func:`shutil.which` now uses ``os.confstr("CS_PATH")`` if
  available and if the :envvar:`PATH` environment variable is not set.
  Remove also the current directory from :data:`posixpath.defpath`. On Unix,
  :func:`shutil.which` and the :mod:`subprocess` module no longer search the
  executable in the current directory if the :envvar:`PATH` environment
  variable is not set.

Core and Builtins
-----------------

- bpo-36722: In debug build, import now also looks for C extensions compiled
  in release mode and for C extensions compiled in the stable ABI.

- bpo-32849: Fix Python Initialization code on FreeBSD to detect properly
  when stdin file descriptor (fd 0) is invalid.

- bpo-36623: Remove parser headers and related function declarations that
  lack implementations after the removal of pgen.

- bpo-20180: ``dict.pop()`` is now up to 33% faster thanks to Argument
  Clinic. Patch by Inada Naoki.

- bpo-36611: Debug memory allocators: disable serialno field by default from
  debug hooks on Python memory allocators to reduce the memory footprint by
  5%. Enable :mod:`tracemalloc` to get the traceback where a memory block
  has been allocated when a fatal memory error is logged to decide where to
  put a breakpoint. Compile Python with ``PYMEM_DEBUG_SERIALNO`` defined to
  get back the field.

- bpo-36588: On AIX, :attr:`sys.platform` doesn't contain the major version
  anymore. Always return ``'aix'``, instead of ``'aix3'`` .. ``'aix7'``.
  Since older Python versions include the version number, it is recommended
  to always use ``sys.platform.startswith('aix')``. Contributed by M. Felt.

- bpo-36549: Change str.capitalize to use titlecase for the first character
  instead of uppercase.

- bpo-36540: Implement :pep:`570` (Python positional-only parameters). Patch
  by Pablo Galindo.

- bpo-36475: :c:func:`PyEval_AcquireLock` and :c:func:`PyEval_AcquireThread`
  now terminate the current thread if called while the interpreter is
  finalizing, making them consistent with :c:func:`PyEval_RestoreThread`,
  :c:func:`Py_END_ALLOW_THREADS`, and :c:func:`PyGILState_Ensure`.

- bpo-36504: Fix signed integer overflow in _ctypes.c's
  ``PyCArrayType_new()``.

- bpo-20844: Fix running script with encoding cookie and LF line ending may
  fail on Windows.

- bpo-24214: Fixed support of the surrogatepass error handler in the UTF-8
  incremental decoder.

- bpo-36452: Changing ``dict`` keys during iteration of the dict itself,
  ``keys()``, ``values()``, or ``items()`` will now be detected in certain
  corner cases where keys are deleted/added so that the number of keys isn't
  changed. A `RuntimeError` will be raised after ``len(dict)`` iterations.
  Contributed by Thomas Perl.

- bpo-36459: Fix a possible double ``PyMem_FREE()`` due to tokenizer.c's
  ``tok_nextc()``.

- bpo-36433: Fixed TypeError message in classmethoddescr_call.

- bpo-36430: Fix a possible reference leak in :func:`itertools.count`.

- bpo-36440: Include node names in ``ParserError`` messages, instead of
  numeric IDs. Patch by A. Skrobov.

- bpo-36143: Regenerate :mod:`keyword` from the Grammar and Tokens file
  using pgen. Patch by Pablo Galindo.

- bpo-18372: Add missing :c:func:`PyObject_GC_Track` calls in the
  :mod:`pickle` module. Patch by Zackery Spytz.

Library
-------

- bpo-35952: Fix pythoninfo when the compiler is missing.

- bpo-28238: The ``.find*()`` methods of xml.etree.ElementTree can now
  search for wildcards like ``{*}tag`` and ``{ns}*`` that match a tag in any
  namespace or all tags in a namespace.  Patch by Stefan Behnel.

- bpo-26978: `pathlib.path.link_to()` is now implemented. It creates a hard
  link pointing to a path.

- bpo-1613500: :class:`fileinput.FileInput` now uses the input file mode to
  correctly set the output file mode (previously it was hardcoded to
  ``'w'``)  when ``inplace=True`` is passed to its constructor.

- bpo-36734: Fix compilation of ``faulthandler.c`` on HP-UX. Initialize
  ``stack_t current_stack`` to zero using ``memset()``.

- bpo-13611: The xml.etree.ElementTree packages gained support for C14N 2.0
  serialisation. Patch by Stefan Behnel.

- bpo-36669: Add missing matrix multiplication operator support to
  weakref.proxy.

- bpo-36676: The XMLParser() in xml.etree.ElementTree provides namespace
  prefix context to the parser target if it defines the callback methods
  "start_ns()" and/or "end_ns()". Patch by Stefan Behnel.

- bpo-36673: The TreeBuilder and XMLPullParser in xml.etree.ElementTree
  gained support for parsing comments and processing instructions. Patch by
  Stefan Behnel.

- bpo-36650: The C version of functools.lru_cache() was treating calls with
  an empty ``**kwargs`` dictionary as being distinct from calls with no
  keywords at all. This did not result in an incorrect answer, but it did
  trigger an unexpected cache miss.

- bpo-28552: Fix :mod:`distutils.sysconfig` if :data:`sys.executable` is
  ``None`` or an empty string: use :func:`os.getcwd` to initialize
  ``project_base``.  Fix also the distutils build command: don't use
  :data:`sys.executable` if it is ``None`` or an empty string.

- bpo-35755: :func:`shutil.which` and
  :func:`distutils.spawn.find_executable` now use ``os.confstr("CS_PATH")``
  if available instead of :data:`os.defpath`, if the ``PATH`` environment
  variable is not set. Moreover, don't use ``os.confstr("CS_PATH")`` nor
  :data:`os.defpath` if the ``PATH`` environment variable is set to an empty
  string.

- bpo-25430: improve performance of ``IPNetwork.__contains__()``

- bpo-30485: Path expressions in xml.etree.ElementTree can now avoid
  explicit namespace prefixes for tags (or the "{namespace}tag" notation) by
  passing a default namespace with an empty string prefix.

- bpo-36613: Fix :mod:`asyncio` wait() not removing callback if exception

- bpo-36598: Fix ``isinstance`` check for Mock objects with spec when the
  code is executed under tracing. Patch by Karthikeyan Singaravelan.

- bpo-18748: In development mode (:option:`-X` ``dev``) and in debug build,
  the :class:`io.IOBase` destructor now logs ``close()`` exceptions. These
  exceptions are silent by default in release mode.

- bpo-36575: The ``_lsprof`` module now uses internal timer same to
  ``time.perf_counter()`` by default. ``gettimeofday(2)`` was used on Unix.
  New timer has better resolution on most Unix platforms and timings are no
  longer impacted by system clock updates since ``perf_counter()`` is
  monotonic. Patch by Inada Naoki.

- bpo-33461: ``json.loads`` now emits ``DeprecationWarning`` when
  ``encoding`` option is specified.  Patch by Matthias Bussonnier.

- bpo-36559: The random module now prefers the lean internal _sha512 module
  over hashlib for seed(version=2) to optimize import time.

- bpo-17561: Set backlog=None as the default for socket.create_server.

- bpo-34373: Fix :func:`time.mktime` error handling on AIX for year before
  1970.

- bpo-36232: Improve error message when trying to open existing DBM database
  that actually doesn't exist. Patch by Marco Rougeth.

- bpo-36546: Add statistics.quantiles()

- bpo-36050: Optimized ``http.client.HTTPResponse.read()`` for large
  response. Patch by Inada Naoki.

- bpo-36522: If *debuglevel* is set to >0 in :mod:`http.client`, print all
  values for headers with multiple values for the same header name. Patch by
  Matt Houglum.

- bpo-36492: Deprecated passing required arguments like *func* as keyword
  arguments in functions which should accept arbitrary keyword arguments and
  pass them to other function. Arbitrary keyword arguments (even with names
  "self" and "func") can now be passed to these functions if the required
  arguments are passed as positional arguments.

- bpo-27181: Add statistics.geometric_mean().

- bpo-30427: ``os.path.normcase()`` relies on ``os.fspath()`` to check the
  type of its argument. Redundant checks have been removed from its
  ``posixpath.normcase()`` and ``ntpath.normcase()`` implementations. Patch
  by Wolfgang Maier.

- bpo-36385: Stop rejecting IPv4 octets for being ambiguously octal. Leading
  zeros are ignored, and no longer are assumed to specify octal octets.
  Octets are always decimal numbers. Octets must still be no more than three
  digits, including leading zeroes.

- bpo-36434: Errors during writing to a ZIP file no longer prevent to
  properly close it.

- bpo-36407: Fixed wrong indentation writing for CDATA section in
  xml.dom.minidom. Patch by Vladimir Surjaninov.

- bpo-36326: inspect.getdoc() can now find docstrings for member objects
  when __slots__ is a dictionary.

- bpo-36366: Calling ``stop()`` on an unstarted or stopped
  :func:`unittest.mock.patch` object will now return `None` instead of
  raising :exc:`RuntimeError`, making the method idempotent. Patch by
  Karthikeyan Singaravelan.

- bpo-36348: The :meth:`imap.IMAP4.logout` method no longer ignores silently
  arbitrary exceptions.

- bpo-31904: Add time module support and fix test_time faiures for VxWorks.

- bpo-36227: Added support for keyword arguments `default_namespace` and
  `xml_declaration` in functions ElementTree.tostring() and
  ElementTree.tostringlist().

- bpo-36004: Added new alternate constructors
  :meth:`datetime.date.fromisocalendar` and
  :meth:`datetime.datetime.fromisocalendar`, which construct date objects
  from ISO year, week number and weekday; these are the inverse of each
  class's ``isocalendar`` method. Patch by Paul Ganssle.

- bpo-35936: :mod:`modulefinder` no longer depends on the deprecated
  :mod:`imp` module, and the initializer for
  :class:`modulefinder.ModuleFinder` now has immutable default arguments.
  Patch by Brandt Bucher.

- bpo-35376: :mod:`modulefinder` correctly handles modules that have the
  same name as a bad package. Patch by Brandt Bucher.

- bpo-17396: :mod:`modulefinder` no longer crashes when encountering syntax
  errors in followed imports. Patch by Brandt Bucher.

- bpo-35934: Added :meth:`~socket.create_server()` and
  :meth:`~socket.has_dualstack_ipv6()` convenience functions to automate the
  necessary tasks usually involved when creating a server socket, including
  accepting both IPv4 and IPv6 connections on the same socket.  (Contributed
  by Giampaolo Rodola in :issue:`17561`.)

- bpo-23078: Add support for :func:`classmethod` and :func:`staticmethod` to
  :func:`unittest.mock.create_autospec`.  Initial patch by Felipe Ochoa.

- bpo-35416: Fix potential resource warnings in distutils. Patch by Mickaël
  Schoentgen.

- bpo-25451: Add transparency methods to :class:`tkinter.PhotoImage`.  Patch
  by Zackery Spytz.

- bpo-35082: Don't return deleted attributes when calling dir on a
  :class:`unittest.mock.Mock`.

- bpo-34547: :class:`wsgiref.handlers.BaseHandler` now handles abrupt client
  connection terminations gracefully. Patch by Petter Strandmark.

- bpo-31658: :func:`xml.sax.parse` now supports :term:`path-like <path-like
  object>`. Patch by Mickaël Schoentgen.

- bpo-34139: Remove stale unix datagram socket before binding

- bpo-33530: Implemented Happy Eyeballs in `asyncio.create_connection()`.
  Added two new arguments, *happy_eyeballs_delay* and *interleave*, to
  specify Happy Eyeballs behavior.

- bpo-33291: Do not raise AttributeError when calling the inspect functions
  isgeneratorfunction, iscoroutinefunction, isasyncgenfunction on a method
  created from an arbitrary callable. Instead, return False.

- bpo-31310: Fix the multiprocessing.semaphore_tracker so it is reused by
  child processes

- bpo-31292: Fix ``setup.py check --restructuredtext`` for files containing
  ``include`` directives.

Documentation
-------------

- bpo-36625: Remove obsolete comments from docstrings in fractions.Fraction

- bpo-30840: Document relative imports

- bpo-36523: Add docstring for io.IOBase.writelines().

- bpo-36425: New documentation translation: `Simplified Chinese
  <https://docs.python.org/zh-cn/>`_.

- bpo-36345: Avoid the duplication of code from ``Tools/scripts/serve.py``
  in using the :rst:dir:`literalinclude` directive for the basic
  wsgiref-based web server in the documentation of :mod:`wsgiref`.
  Contributed by Stéphane Wirtel.

- bpo-36345: Using the code of the ``Tools/scripts/serve.py`` script as an
  example in the :mod:`wsgiref` documentation.  Contributed by Stéphane
  Wirtel.

- bpo-36157: Added Documention for  PyInterpreterState_Main().

- bpo-33043: Updates the docs.python.org page with the addition of a
  'Contributing to Docs' link at the end of the page (between 'Reporting
  Bugs' and 'About Documentation'). Updates the 'Found a Bug' page with
  additional links and information in the Documentation Bugs section.

- bpo-35581: @typing.type_check_only now allows type stubs to mark functions
  and classes not available during runtime.

- bpo-33832: Add glossary entry for 'magic method'.

- bpo-32913: Added re.Match.groupdict example to regex HOWTO.

Tests
-----

- bpo-36719: regrtest now always detects uncollectable objects. Previously,
  the check was only enabled by ``--findleaks``. The check now also works
  with ``-jN/--multiprocess N``. ``--findleaks`` becomes a deprecated alias
  to ``--fail-env-changed``.

- bpo-36725: When using multiprocessing mode (-jN), regrtest now better
  reports errors if a worker process fails, and it exits immediately on a
  worker thread failure or when interrupted.

- bpo-36454: Change test_time.test_monotonic() to test only the lower bound
  of elapsed time after a sleep command rather than the upper bound. This
  prevents unnecessary test failures on slow buildbots. Patch by Victor
  Stinner.

- bpo-32424: Improve test coverage for xml.etree.ElementTree. Patch by
  Gordon P. Hemsley.

- bpo-32424: Fix typo in test_cyclic_gc() test for xml.etree.ElementTree.
  Patch by Gordon P. Hemsley.

- bpo-36635: Add a new :mod:`_testinternalcapi` module to test the internal
  C API.

- bpo-36629: Fix ``test_imap4_host_default_value()`` of ``test_imaplib``:
  catch also :data:`errno.ENETUNREACH` error.

- bpo-36611: Fix ``test_sys.test_getallocatedblocks()`` when
  :mod:`tracemalloc` is enabled.

- bpo-36560: Fix reference leak hunting in regrtest: compute also deltas (of
  reference count, allocated memory blocks, file descriptor count) during
  warmup, to ensure that everything is initialized before starting to hunt
  reference leaks.

- bpo-36565: Fix reference hunting (``python3 -m test -R 3:3``) when Python
  has no built-in abc module.

- bpo-31904: Port test_resource to VxWorks: skip tests cases setting
  RLIMIT_FSIZE and RLIMIT_CPU.

- bpo-31904: Fix test_tabnanny on VxWorks: adjust ENOENT error message.

- bpo-36436: Fix ``_testcapi.pymem_buffer_overflow()``: handle memory
  allocation failure.

- bpo-31904: Fix test_utf8_mode on VxWorks: Python always use UTF-8 on
  VxWorks.

- bpo-36341: Fix tests that may fail with PermissionError upon calling
  bind() on AF_UNIX sockets.

Build
-----

- bpo-36747: Remove the stale scriptsinstall Makefile target.

- bpo-21536: On Unix, C extensions are no longer linked to libpython except
  on Android and Cygwin.

  It is now possible for a statically linked Python to load a C extension
  built using a shared library Python.

  When Python is embedded, ``libpython`` must not be loaded with
  ``RTLD_LOCAL``, but ``RTLD_GLOBAL`` instead. Previously, using
  ``RTLD_LOCAL``, it was already not possible to load C extensions which
  were not linked to ``libpython``, such as C extensions of the standard
  library built by the ``*shared*`` section of ``Modules/Setup``.

  distutils, python-config and python-config.py have been modified.

- bpo-36707: ``./configure --with-pymalloc`` no longer adds the ``m`` flag
  to SOABI (sys.implementation.cache_tag). Enabling or disabling pymalloc
  has no impact on the ABI.

- bpo-36635: Change ``PyAPI_FUNC(type)``, ``PyAPI_DATA(type)`` and
  ``PyMODINIT_FUNC`` macros of ``pyport.h`` when ``Py_BUILD_CORE_MODULE`` is
  defined. The ``Py_BUILD_CORE_MODULE`` define must be now be used to build
  a C extension as a dynamic library accessing Python internals: export the
  PyInit_xxx() function in DLL exports on Windows.

- bpo-31904: Don't build the ``_crypt`` extension on VxWorks.

- bpo-36618: Add ``-fmax-type-align=8`` to CFLAGS when clang compiler is
  detected. The pymalloc memory allocator aligns memory on 8 bytes. On
  x86-64, clang expects alignment on 16 bytes by default and so uses MOVAPS
  instruction which can lead to segmentation fault. Instruct clang that
  Python is limited to alignment on 8 bytes to use MOVUPS instruction
  instead: slower but don't trigger a SIGSEGV if the memory is not aligned
  on 16 bytes. Sadly, the flag must be added to ``CFLAGS`` and not just
  ``CFLAGS_NODIST``, since third party C extensions can have the same issue.

- bpo-36605: ``make tags`` and ``make TAGS`` now also parse
  ``Modules/_io/*.c`` and ``Modules/_io/*.h``.

- bpo-36465: Release builds and debug builds are now ABI compatible:
  defining the ``Py_DEBUG`` macro no longer implies the ``Py_TRACE_REFS``
  macro, which introduces the only ABI incompatibility. The
  ``Py_TRACE_REFS`` macro, which adds the :func:`sys.getobjects` function
  and the :envvar:`PYTHONDUMPREFS` environment variable, can be set using
  the new ``./configure --with-trace-refs`` build option.

- bpo-36577: setup.py now correctly reports missing OpenSSL headers and
  libraries again.

- bpo-36544: Fix regression introduced in bpo-36146 refactoring setup.py

- bpo-36508: ``python-config --ldflags`` no longer includes flags of the
  ``LINKFORSHARED`` variable. The ``LINKFORSHARED`` variable must only be
  used to build executables.

- bpo-36503: Remove references to "aix3" and "aix4". Patch by M. Felt.

Windows
-------

- bpo-35920: Added platform.win32_edition() and platform.win32_is_iot().
  Added support for cross-compiling packages for Windows ARM32. Skip tests
  that are not expected to work on Windows IoT Core ARM32.

- bpo-36649: Remove trailing spaces for registry keys when installed via the
  Store.

- bpo-34144: Fixed activate.bat to correctly update codepage when chcp.com
  returns dots in output. Patch by Lorenz Mende.

- bpo-36509: Added preset-iot layout for Windows IoT ARM containers. This
  layout doesn't contain UI components like tkinter or IDLE. It also doesn't
  contain files to support on-target builds since Windows ARM32 builds must
  be cross-compiled when using MSVC.

- bpo-35941: enum_certificates function of the ssl module now returns
  certificates from all available certificate stores inside windows in a
  query instead of returning only certificates from the system wide
  certificate store. This includes certificates from these certificate
  stores: local machine, local machine enterprise, local machine group
  policy, current user, current user group policy, services, users.
  ssl.enum_crls() function is changed in the same way to return all
  certificate revocation lists inside the windows certificate revocation
  list stores.

- bpo-36441: Fixes creating a venv when debug binaries are installed.

- bpo-36085: Enable better DLL resolution on Windows by using safe DLL
  search paths and adding :func:`os.add_dll_directory`.

- bpo-36010: Add the venv standard library module to the nuget distribution
  for Windows.

- bpo-29515: Add the following socket module constants on Windows:
  IPPROTO_AH IPPROTO_CBT IPPROTO_DSTOPTS IPPROTO_EGP IPPROTO_ESP
  IPPROTO_FRAGMENT IPPROTO_GGP IPPROTO_HOPOPTS IPPROTO_ICLFXBM
  IPPROTO_ICMPV6 IPPROTO_IDP IPPROTO_IGMP IPPROTO_IGP IPPROTO_IPV4
  IPPROTO_IPV6 IPPROTO_L2TP IPPROTO_MAX IPPROTO_ND IPPROTO_NONE IPPROTO_PGM
  IPPROTO_PIM IPPROTO_PUP IPPROTO_RDP IPPROTO_ROUTING IPPROTO_SCTP
  IPPROTO_ST

- bpo-35947: Added current version of libffi to cpython-source-deps. Change
  _ctypes to use current version of libffi on Windows.

- bpo-34060: Report system load when running test suite on Windows. Patch by
  Ammar Askar. Based on prior work by Jeremy Kloth.

- bpo-31512: With the Windows 10 Creators Update, non-elevated users can now
  create symlinks as long as the computer has Developer Mode enabled.

macOS
-----

- bpo-34602: Avoid failures setting macOS stack resource limit with
  resource.setrlimit. This reverts an earlier fix for bpo-18075 which forced
  a non-default stack size when building the interpreter executable on
  macOS.

IDLE
----

- bpo-36429: Fix starting IDLE with pyshell. Add idlelib.pyshell alias at
  top; remove pyshell alias at bottom. Remove obsolete __name__=='__main__'
  command.

Tools/Demos
-----------

- bpo-14546: Fix the argument handling in Tools/scripts/lll.py.

C API
-----

- bpo-36763: Fix memory leak in :c:func:`Py_SetStandardStreamEncoding`:
  release memory if the function is called twice.

- bpo-36641: :c:macro:`PyDoc_VAR(name)` and
  :c:macro:`PyDoc_STRVAR(name,str)` now create ``static const char name[]``
  instead of ``static char name[]``.  Patch by Inada Naoki.

- bpo-36389: Change the value of ``CLEANBYTE``, ``DEADDYTE`` and
  ``FORBIDDENBYTE`` internal constants used by debug hooks on Python memory
  allocators (:c:func:`PyMem_SetupDebugHooks` function). Byte patterns
  ``0xCB``, ``0xDB`` and ``0xFB`` have been replaced with ``0xCD``, ``0xDD``
  and ``0xFD`` to use the same values than Windows CRT debug ``malloc()``
  and ``free()``.

- bpo-36443: Since Python 3.7.0, calling :c:func:`Py_DecodeLocale` before
  :c:func:`Py_Initialize` produces mojibake if the ``LC_CTYPE`` locale is
  coerced and/or if the UTF-8 Mode is enabled by the user configuration. The
  LC_CTYPE coercion and UTF-8 Mode are now disabled by default to fix the
  mojibake issue. They must now be enabled explicitly (opt-in) using the new
  :c:func:`_Py_PreInitialize` API with ``_PyPreConfig``.

- bpo-36025: Fixed an accidental change to the datetime C API where the
  arguments to the :c:func:`PyDate_FromTimestamp` function were incorrectly
  interpreted as a single timestamp rather than an arguments tuple, which
  causes existing code to start raising :exc:`TypeError`. The
  backwards-incompatible change was only present in alpha releases of Python
  3.8. Patch by Paul Ganssle.

- bpo-35810: Modify ``PyObject_Init`` to correctly increase the refcount of
  heap- allocated Type objects. Also fix the refcounts of the heap-allocated
  types that were either doing this manually or not decreasing the type's
  refcount in tp_dealloc


What's New in Python 3.8.0 alpha 3?
===================================

*Release date: 2019-03-25*

Security
--------

- bpo-36216: Changes urlsplit() to raise ValueError when the URL contains
  characters that decompose under IDNA encoding (NFKC-normalization) into
  characters that affect how the URL is parsed.

- bpo-35121: Don't send cookies of domain A without Domain attribute to
  domain B when domain A is a suffix match of domain B while using a
  cookiejar with :class:`http.cookiejar.DefaultCookiePolicy` policy. Patch
  by Karthikeyan Singaravelan.

Core and Builtins
-----------------

- bpo-36421: Fix a possible double decref in _ctypes.c's
  ``PyCArrayType_new()``.

- bpo-36412: Fix a possible crash when creating a new dictionary.

- bpo-36398: Fix a possible crash in ``structseq_repr()``.

- bpo-36256: Fix bug in parsermodule when parsing a state in a DFA that has
  two or more arcs with labels of the same type. Patch by Pablo Galindo.

- bpo-36365: repr(structseq) is no longer limited to 512 bytes.

- bpo-36374: Fix a possible null pointer dereference in
  ``merge_consts_recursive()``. Patch by Zackery Spytz.

- bpo-36236: At Python initialization, the current directory is no longer
  prepended to :data:`sys.path` if it has been removed.

- bpo-36352: Python initialization now fails with an error, rather than
  silently truncating paths, if a path is too long.

- bpo-36301: Python initialization now fails if decoding ``pybuilddir.txt``
  configuration file fails at startup.

- bpo-36333: Fix leak in _PyRuntimeState_Fini. Contributed by Stéphane
  Wirtel.

- bpo-36332: The builtin :func:`compile` can now handle AST objects that
  contain assignment expressions. Patch by Pablo Galindo.

- bpo-36282: Improved error message for too much positional arguments in
  some builtin functions.

- bpo-30040: New empty dict uses fewer memory for now.  It used more memory
  than empty dict created by ``dict.clear()``.  And empty dict creation and
  deletion is about 2x faster.  Patch by Inada Naoki.

- bpo-36262: Fix an unlikely memory leak on conversion from string to float
  in the function ``_Py_dg_strtod()`` used by ``float(str)``,
  ``complex(str)``, :func:`pickle.load`, :func:`marshal.load`, etc.

- bpo-36252: Update Unicode databases to version 12.0.0.

- bpo-36218: Fix a segfault occurring when sorting a list of heterogeneous
  values. Patch contributed by Rémi Lapeyre and Elliot Gorokhovsky.

- bpo-36188: Cleaned up left-over vestiges of Python 2 unbound method
  handling in method objects and documentation. Patch by Martijn Pieters

- bpo-36124: Add a new interpreter-specific dict and expose it in the C-API
  via PyInterpreterState_GetDict().  This parallels PyThreadState_GetDict().
  However, extension modules should continue using PyModule_GetState() for
  their own internal per-interpreter state.

- bpo-35975: Add a ``feature_version`` flag to ``ast.parse()`` (documented)
  and ``compile()`` (hidden) that allows tweaking the parser to support
  older versions of the grammar. In particular, if ``feature_version`` is 5
  or 6, the hacks for the ``async`` and ``await`` keyword from PEP 492 are
  reinstated. (For 7 or higher, these are unconditionally treated as
  keywords, but they are still special tokens rather than ``NAME`` tokens
  that the parser driver recognizes.)

- bpo-31904: Use UTF-8 as the system encoding on VxWorks.

- bpo-36048: The :meth:`~object.__index__` special method will be used
  instead of :meth:`~object.__int__` for implicit conversion of Python
  numbers to C integers.  Using the ``__int__()`` method in implicit
  conversions has been deprecated.

- bpo-35808: Retire pgen and use a modified version of pgen2 to generate the
  parser. Patch by Pablo Galindo.

Library
-------

- bpo-36401: The class documentation created by pydoc now has a separate
  section for readonly properties.

- bpo-36320: The typing.NamedTuple() class has deprecated the _field_types
  attribute in favor of the __annotations__ attribute which carried the same
  information. Also, both attributes were converted from OrderedDict to a
  regular dict.

- bpo-34745: Fix :mod:`asyncio` ssl memory issues caused by circular
  references

- bpo-36324: Add method to statistics.NormalDist for computing the inverse
  cumulative normal distribution.

- bpo-36321: collections.namedtuple() misspelled the name of an attribute.
  To be consistent with typing.NamedTuple, the attribute name should have
  been "_field_defaults" instead of "_fields_defaults".  For backwards
  compatibility, both spellings are now created.  The misspelled version may
  be removed in the future.

- bpo-36297: "unicode_internal" codec is removed.  It was deprecated since
  Python 3.3. Patch by Inada Naoki.

- bpo-36298: Raise ModuleNotFoundError in pyclbr when a module can't be
  found. Thanks to 'mental' for the bug report.

- bpo-36268: Switch the default format used for writing tars with
  mod:`tarfile` to the modern POSIX.1-2001 pax standard, from the
  vendor-specific GNU. Contributed by C.A.M. Gerlach.

- bpo-36285: Fix integer overflows in the array module. Patch by Stephan
  Hohe.

- bpo-31904: Add _signal module support for VxWorks.

- bpo-36272: :mod:`logging` does not silently ignore RecursionError anymore.
  Patch contributed by Rémi Lapeyre.

- bpo-36280: Add a kind field to ast.Constant. It is 'u' if the literal has
  a 'u' prefix (i.e. a Python 2 style unicode literal), else None.

- bpo-35931: The :mod:`pdb` ``debug`` command now gracefully handles all
  exceptions.

- bpo-36251: Fix format strings used for stderrprinter and re.Match reprs.
  Patch by Stephan Hohe.

- bpo-36235: Fix ``CFLAGS`` in ``customize_compiler()`` of
  ``distutils.sysconfig``: when the ``CFLAGS`` environment variable is
  defined, don't override ``CFLAGS`` variable with the ``OPT`` variable
  anymore. Initial patch written by David Malcolm.

- bpo-35807: Update ensurepip to install pip 19.0.3 and setuptools 40.8.0.

- bpo-36139: Release GIL when closing :class:`~mmap.mmap` objects.

- bpo-36179: Fix two unlikely reference leaks in _hashopenssl. The leaks
  only occur in out-of-memory cases.

- bpo-36169: Add overlap() method to statistics.NormalDist.  Computes the
  overlapping coefficient for two normal distributions.

- bpo-36103: Default buffer size used by ``shutil.copyfileobj()`` is changed
  from 16 KiB to 64 KiB on non-Windows platform to reduce system call
  overhead. Contributed by Inada Naoki.

- bpo-36130: Fix ``pdb`` with ``skip=...`` when stepping into a frame
  without a ``__name__`` global.  Patch by Anthony Sottile.

- bpo-35652: shutil.copytree(copy_function=...) erroneously pass DirEntry
  instead of a path string.

- bpo-35178: Ensure custom :func:`warnings.formatwarning` function can
  receive `line` as positional argument. Based on patch by Tashrif Billah.

- bpo-36106: Resolve potential name clash with libm's sinpi(). Patch by
  Dmitrii Pasechnik.

- bpo-36091: Clean up reference to async generator in Lib/types. Patch by
  Henry Chen.

- bpo-36043: :class:`FileCookieJar` supports :term:`path-like object`.
  Contributed by Stéphane Wirtel

- bpo-35899: Enum has been fixed to correctly handle empty strings and
  strings with non-Latin characters (ie. 'α', 'א') without crashing.
  Original patch contributed by Maxwell. Assisted by Stéphane Wirtel.

- bpo-21269: Add ``args`` and ``kwargs`` properties to mock call objects.
  Contributed by Kumar Akshay.

- bpo-30670: `pprint.pp` has been added to pretty-print objects with
  dictionary keys being sorted with their insertion order by default.
  Parameter *sort_dicts* has been added to `pprint.pprint`, `pprint.pformat`
  and `pprint.PrettyPrinter`. Contributed by Rémi Lapeyre.

- bpo-35843: Implement ``__getitem__`` for ``_NamespacePath``.  Patch by
  Anthony Sottile.

- bpo-35802: Clean up code which checked presence of ``os.stat`` /
  ``os.lstat`` / ``os.chmod`` which are always present.  Patch by Anthony
  Sottile.

- bpo-35715: Librates the return value of a ProcessPoolExecutor
  _process_worker after it's no longer needed to free memory

- bpo-35493: Use :func:`multiprocessing.connection.wait` instead of polling
  each 0.2 seconds for worker updates in :class:`multiprocessing.Pool`.
  Patch by Pablo Galindo.

- bpo-35661: Store the venv prompt in pyvenv.cfg.

- bpo-35121: Don't set cookie for a request when the request path is a
  prefix match of the cookie's path attribute but doesn't end with "/".
  Patch by Karthikeyan Singaravelan.

- bpo-21478: Calls to a child function created with
  :func:`unittest.mock.create_autospec` should propagate to the parent.
  Patch by Karthikeyan Singaravelan.

- bpo-35198: Fix C++ extension compilation on AIX

Documentation
-------------

- bpo-36329: Declare the path of the Python binary for the usage of
  ``Tools/scripts/serve.py`` when executing ``make -C Doc/ serve``.
  Contributed by Stéphane Wirtel

- bpo-36138: Improve documentation about converting datetime.timedelta to
  scalars.

- bpo-21314: A new entry was added to the Core Language Section of the
  Programming FAQ, which explaines the usage of slash(/) in the signature of
  a function. Patch by Lysandros Nikolaou

Tests
-----

- bpo-36234: test_posix.PosixUidGidTests: add tests for invalid uid/gid type
  (str). Initial patch written by David Malcolm.

- bpo-29571: Fix ``test_re.test_locale_flag()``:  use
  ``locale.getpreferredencoding()`` rather than ``locale.getlocale()`` to
  get the locale encoding. With some locales, ``locale.getlocale()`` returns
  the wrong encoding.

- bpo-36123: Fix race condition in test_socket.

Build
-----

- bpo-36356: Fix leaks that led to build failure when configured with
  address sanitizer.

- bpo-36146: Add ``TEST_EXTENSIONS`` constant to ``setup.py`` to allow to
  not build test extensions like ``_testcapi``.

- bpo-36146: Fix setup.py on macOS: only add ``/usr/include/ffi`` to include
  directories of _ctypes, not for all extensions.

- bpo-31904: Enable build system to cross-build for VxWorks RTOS.

Windows
-------

- bpo-36312: Fixed decoders for the following code pages: 50220, 50221,
  50222, 50225, 50227, 50229, 57002 through 57011, 65000 and 42.

- bpo-36264: Don't honor POSIX ``HOME`` in ``os.path.expanduser`` on
  windows.  Patch by Anthony Sottile.

- bpo-24643: Fix name collisions due to ``#define timezone _timezone`` in
  PC/pyconfig.h.

IDLE
----

- bpo-36405: Use dict unpacking in idlelib.

- bpo-36396: Remove fgBg param of idlelib.config.GetHighlight(). This param
  was only used twice and changed the return type.

- bpo-36176: Fix IDLE autocomplete & calltip popup colors. Prevent conflicts
  with Linux dark themes (and slightly darken calltip background).

- bpo-23205: For the grep module, add tests for findfiles, refactor
  findfiles to be a module-level function, and refactor findfiles to use
  os.walk.

- bpo-23216: Add docstrings to IDLE search modules.

- bpo-36152: Remove colorizer.ColorDelegator.close_when_done and the
  corresponding argument of .close().  In IDLE, both have always been None
  or False since 2007.

- bpo-32129: Avoid blurry IDLE application icon on macOS with Tk 8.6. Patch
  by Kevin Walzer.

- bpo-36096: Refactor class variables to instance variables in colorizer.

- bpo-30348: Increase test coverage of idlelib.autocomplete by 30%. Patch by
  Louie Lu

Tools/Demos
-----------

- bpo-35132: Fix py-list and py-bt commands of python-gdb.py on gdb7.

- bpo-32217: Fix freeze script on Windows.

C API
-----

- bpo-36381: Raise ``DeprecationWarning`` when '#' formats are used for
  building or parsing values without ``PY_SSIZE_T_CLEAN``.

- bpo-36142: The whole coreconfig.h header is now excluded from
  Py_LIMITED_API. Move functions definitions into a new internal
  pycore_coreconfig.h header.


What's New in Python 3.8.0 alpha 2?
===================================

*Release date: 2019-02-25*

Core and Builtins
-----------------

- bpo-36052: Raise a :exc:`SyntaxError` when assigning a value to
  `__debug__` with the Assignment Operator. Contributed by Stéphane Wirtel
  and Pablo Galindo.

- bpo-36012: Doubled the speed of class variable writes.  When a non-dunder
  attribute was updated, there was an unnecessary call to update slots.

- bpo-35942: The error message emitted when returning invalid types from
  ``__fspath__`` in interfaces that allow passing :class:`~os.PathLike`
  objects has been improved and now it does explain the origin of the error.

- bpo-36016: ``gc.get_objects`` can now receive an optional parameter
  indicating a generation to get objects from. Patch by Pablo Galindo.

- bpo-1054041: When the main interpreter exits due to an uncaught
  KeyboardInterrupt, the process now exits in the appropriate manner for its
  parent process to detect that a SIGINT or ^C terminated the process.  This
  allows shells and batch scripts to understand that the user has asked them
  to stop.

- bpo-35992: Fix ``__class_getitem__()`` not being called on a class with a
  custom non-subscriptable metaclass.

- bpo-35993: Fix a crash on fork when using subinterpreters. Contributed by
  Stéphane Wirtel

- bpo-35991: Fix a potential double free in Modules/_randommodule.c.

- bpo-35961: Fix a crash in slice_richcompare(): use strong references
  rather than stolen references for the two temporary internal tuples.

- bpo-35911: Enable the creation of cell objects by adding a
  ``cell.__new__`` method, and expose the type ``cell`` in ``Lib/types.py``
  under the name CellType. Patch by Pierre Glaser.

- bpo-12822: Use monotonic clock for ``pthread_cond_timedwait`` when
  ``pthread_condattr_setclock`` and ``CLOCK_MONOTONIC`` are available.

- bpo-15248: The compiler emits now syntax warnings in the case when a comma
  is likely missed before tuple or list.

- bpo-35886: The implementation of PyInterpreterState has been moved into
  the internal header files (guarded by Py_BUILD_CORE).

- bpo-31506: Clarify the errors reported when ``object.__new__`` and
  ``object.__init__`` receive more than one argument. Contributed by Sanyam
  Khurana.

- bpo-35724: Signal-handling is now guaranteed to happen relative to the
  main interpreter.

- bpo-33608: We added a new internal _Py_AddPendingCall() that operates
  relative to the provided interpreter.  This allows us to use the existing
  implementation to ask another interpreter to do work that cannot be done
  in the current interpreter, like decref an object the other interpreter
  owns.  The existing Py_AddPendingCall() only operates relative to the main
  interpreter.

- bpo-33989: Fix a possible crash in :meth:`list.sort` when sorting objects
  with ``ob_type->tp_richcompare == NULL``.  Patch by Zackery Spytz.

Library
-------

- bpo-35512: :func:`unittest.mock.patch.dict` used as a decorator with
  string target resolves the target during function call instead of during
  decorator construction. Patch by Karthikeyan Singaravelan.

- bpo-36018: Add statistics.NormalDist, a tool for creating and manipulating
  normal distributions of random variable.  Features a composite class that
  treats the mean and standard deviation of measurement data as single
  entity.

- bpo-35904: Added statistics.fmean() as a faster, floating point variant of
  the existing mean() function.

- bpo-35918: Removed broken ``has_key`` method from
  multiprocessing.managers.SyncManager.dict. Contributed by Rémi Lapeyre.

- bpo-18283: Add support for bytes to :func:`shutil.which`.

- bpo-35960: Fix :func:`dataclasses.field` throwing away empty mapping
  objects passed as metadata.

- bpo-35500: Write expected and actual call parameters on separate lines in
  :meth:`unittest.mock.Mock.assert_called_with` assertion errors.
  Contributed by Susan Su.

- bpo-35931: The :mod:`pdb` ``debug`` command now gracefully handles syntax
  errors.

- bpo-24209: In http.server script, rely on getaddrinfo to bind to preferred
  address based on the bind parameter. Now default bind or binding to a name
  may bind to IPv6 or dual-stack, depending on the environment.

- bpo-35321: Set ``__spec__.origin`` of  ``_frozen_importlib`` to frozen so
  that it matches the behavior of ``_frozen_importlib_external``.  Patch by
  Nina Zakharenko.

- bpo-35378: Fix a reference issue inside :class:`multiprocessing.Pool` that
  caused the pool to remain alive if it was deleted without being closed or
  terminated explicitly. A new strong reference is added to the pool
  iterators to link the lifetime of the pool to the lifetime of its
  iterators so the pool does not get destroyed if a pool iterator is still
  alive.

- bpo-34294: re module, fix wrong capturing groups in rare cases.
  :func:`re.search`, :func:`re.findall`, :func:`re.sub` and other functions
  that scan through string looking for a match, should reset capturing
  groups between two match attempts. Patch by Ma Lin.

- bpo-35615: :mod:`weakref`: Fix a RuntimeError when copying a
  WeakKeyDictionary or a WeakValueDictionary, due to some keys or values
  disappearing while iterating.

- bpo-35606: Implement :func:`math.prod` as analogous function to
  :func:`sum` that returns the product of a 'start' value (default: 1) times
  an iterable of numbers. Patch by Pablo Galindo.

- bpo-32417: Performing arithmetic between :class:`datetime.datetime`
  subclasses and :class:`datetime.timedelta` now returns an object of the
  same type as the :class:`datetime.datetime` subclass. As a result,
  :meth:`datetime.datetime.astimezone` and alternate constructors like
  :meth:`datetime.datetime.now` and :meth:`datetime.fromtimestamp` called
  with a ``tz`` argument now *also* retain their subclass.

- bpo-35153: Add *headers* optional keyword-only parameter to
  :class:`xmlrpc.client.ServerProxy`, :class:`xmlrpc.client.Transport` and
  :class:`xmlrpc.client.SafeTransport`.  Patch by Cédric Krier.

- bpo-34572: Fix C implementation of pickle.loads to use importlib's locking
  mechanisms, and thereby avoid using partially-loaded modules. Patch by Tim
  Burgess.

Documentation
-------------

- bpo-36083: Fix formatting of --check-hash-based-pycs options in the
  manpage Synopsis.

- bpo-36007: Bump minimum sphinx version to 1.8.  Patch by Anthony Sottile.

- bpo-22062: Update documentation and docstrings for pathlib. Original patch
  by Mike Short.

Tests
-----

- bpo-27313: Avoid test_ttk_guionly ComboboxTest failure with macOS Cocoa
  Tk.

- bpo-36019: Add test.support.TEST_HTTP_URL and replace references of
  http://www.example.com by this new constant. Contributed by Stéphane
  Wirtel.

- bpo-36037: Fix test_ssl for strict OpenSSL configuration like RHEL8 strict
  crypto policy. Use older TLS version for minimum TLS version of the server
  SSL context if needed, to test TLS version older than default minimum TLS
  version.

- bpo-35798: Added :func:`test.support.check_syntax_warning`.

- bpo-35505: Make test_imap4_host_default_value independent on whether the
  local IMAP server is running.

- bpo-35917: multiprocessing: provide unit tests for SyncManager and
  SharedMemoryManager classes + all the shareable types which are supposed
  to be supported by them.  (patch by Giampaolo Rodola)

- bpo-35704: Skip ``test_shutil.test_unpack_archive_xztar`` to prevent a
  MemoryError on 32-bit AIX when MAXDATA setting is less than 0x20000000.

  Patch by Michael Felt (aixtools)

- bpo-34720: Assert m_state != NULL to mimic GC traversal functions that do
  not correctly handle module creation when the module state has not been
  created.

Windows
-------

- bpo-35976: Added ARM build support to Windows build files in PCBuild.

- bpo-35692: ``pathlib`` no longer raises when checking file and directory
  existence on drives that are not ready

- bpo-35872: Uses the base Python executable when invoking venv in a virtual
  environment

- bpo-35873: Prevents venv paths being inherited by child processes

- bpo-35299: Fix sysconfig detection of the source directory and distutils
  handling of pyconfig.h during PGO profiling

IDLE
----

- bpo-24310: IDLE -- Document settings dialog font tab sample.

- bpo-35833: Revise IDLE doc for control codes sent to Shell. Add a code
  example block.

- bpo-35689: Add docstrings and unittests for colorizer.py.


What's New in Python 3.8.0 alpha 1?
===================================

*Release date: 2019-02-03*

Security
--------

- bpo-35746: [CVE-2019-5010] Fix a NULL pointer deref in ssl module. The
  cert parser did not handle CRL distribution points with empty DP or URI
  correctly. A malicious or buggy certificate can result into segfault.
  Vulnerability (TALOS-2018-0758) reported by Colin Read and Nicolas Edet of
  Cisco.

- bpo-34812: The :option:`-I` command line option (run Python in isolated
  mode) is now also copied by the :mod:`multiprocessing` and
  :mod:`distutils` modules when spawning child processes. Previously, only
  :option:`-E` and :option:`-s` options (enabled by :option:`-I`) were
  copied.

- bpo-34791: The xml.sax and xml.dom.domreg no longer use environment
  variables to override parser implementations when
  sys.flags.ignore_environment is set by -E or -I arguments.

- bpo-17239: The xml.sax and xml.dom.minidom parsers no longer processes
  external entities by default. External DTD and ENTITY declarations no
  longer load files or create network connections.

- bpo-34623: CVE-2018-14647: The C accelerated _elementtree module now
  initializes hash randomization salt from _Py_HashSecret instead of
  libexpat's default CSPRNG.

- bpo-34405: Updated to OpenSSL 1.1.0i for Windows builds.

- bpo-33871: Fixed sending the part of the file in :func:`os.sendfile` on
  macOS.  Using the *trailers* argument could cause sending more bytes from
  the input file than was specified.

- bpo-32533: Fixed thread-safety of error handling in _ssl.

- bpo-33136: Harden ssl module against LibreSSL CVE-2018-8970.
  X509_VERIFY_PARAM_set1_host() is called with an explicit namelen. A new
  test ensures that NULL bytes are not allowed.

- bpo-33001: Minimal fix to prevent buffer overrun in os.symlink on Windows

- bpo-32981: Regexes in difflib and poplib were vulnerable to catastrophic
  backtracking. These regexes formed potential DOS vectors (REDOS). They
  have been refactored. This resolves CVE-2018-1060 and CVE-2018-1061. Patch
  by Jamie Davis.

- bpo-28414: The ssl module now allows users to perform their own IDN
  en/decoding when using SNI.

Core and Builtins
-----------------

- bpo-35877: Make parenthesis optional for named expressions in while
  statement. Patch by Karthikeyan Singaravelan.

- bpo-35814: Allow same right hand side expressions in annotated assignments
  as in normal ones. In particular, ``x: Tuple[int, int] = 1, 2`` (without
  parentheses on the right) is now allowed.

- bpo-35766: Add the option to parse PEP 484 type comments in the ast
  module. (Off by default.) This is merging the key functionality of the
  third party fork thereof,
  [typed_ast](https://github.com/python/typed_ast).

- bpo-35713: Reorganize Python initialization to get working exceptions and
  sys.stderr earlier.

- bpo-33416: Add end line and end column position information to the Python
  AST nodes. This is a C-level backwards incompatible change.

- bpo-35720: Fixed a minor memory leak in pymain_parse_cmdline_impl function
  in Modules/main.c

- bpo-35634: ``func(**kwargs)`` will now raise an error when ``kwargs`` is a
  mapping containing multiple entries with the same key. An error was
  already raised when other keyword arguments are passed before ``**kwargs``
  since Python 3.6.

- bpo-35623: Fix a crash when sorting very long lists. Patch by Stephan
  Hohe.

- bpo-35214: clang Memory Sanitizer build instrumentation was added to work
  around false positives from posix, socket, time, test_io, and
  test_faulthandler.

- bpo-35560: Fix an assertion error in :func:`format` in debug build for
  floating point formatting with "n" format, zero padding and small width.
  Release build is not impacted. Patch by Karthikeyan Singaravelan.

- bpo-35552: Format characters ``%s`` and ``%V`` in
  :c:func:`PyUnicode_FromFormat` and ``%s`` in :c:func:`PyBytes_FromFormat`
  no longer read memory past the limit if *precision* is specified.

- bpo-35504: Fix segfaults and :exc:`SystemError`\ s when deleting certain
  attributes. Patch by Zackery Spytz.

- bpo-35504: Fixed a SystemError when delete the characters_written
  attribute of an OSError.

- bpo-35494: Improved syntax error messages for unbalanced parentheses in
  f-string.

- bpo-35444: Fixed error handling in pickling methods when fail to look up
  builtin "getattr". Sped up pickling iterators.

- bpo-35436: Fix various issues with memory allocation error handling.
  Patch by Zackery Spytz.

- bpo-35423: Separate the signal handling trigger in the eval loop from the
  "pending calls" machinery. There is no semantic change and the difference
  in performance is insignificant.

- bpo-35357: Internal attributes' names of unittest.mock._Call and
  unittest.mock.MagicProxy (name, parent & from_kall) are now prefixed with
  _mock_ in order to prevent clashes with widely used object attributes.
  Fixed minor typo in test function name.

- bpo-35372: Fixed the code page decoder for input longer than 2 GiB
  containing undecodable bytes.

- bpo-35336: Fix PYTHONCOERCECLOCALE=1 environment variable: only coerce the
  C locale if the LC_CTYPE locale is "C".

- bpo-31241: The *lineno* and *col_offset* attributes of AST nodes for list
  comprehensions, generator expressions and tuples are now point to the
  opening parenthesis or square brace. For tuples without parenthesis they
  point to the position of the first item.

- bpo-33954: For :meth:`str.format`, :meth:`float.__format__` and
  :meth:`complex.__format__` methods for non-ASCII decimal point when using
  the "n" formatter.

- bpo-35269: Fix a possible segfault involving a newly-created coroutine.
  Patch by Zackery Spytz.

- bpo-35224: Implement :pep:`572` (assignment expressions). Patch by Emily
  Morehouse.

- bpo-32492: Speed up :class:`namedtuple` attribute access by 1.6x using a C
  fast-path for the name descriptors. Patch by Pablo Galindo.

- bpo-35214: Fixed an out of bounds memory access when parsing a truncated
  unicode escape sequence at the end of a string such as ``'\N'``.  It would
  read one byte beyond the end of the memory allocation.

- bpo-35214: The interpreter and extension modules have had annotations
  added so that they work properly under clang's Memory Sanitizer.  A new
  configure flag --with-memory-sanitizer has been added to make test builds
  of this nature easier to perform.

- bpo-35193: Fix an off by one error in the bytecode peephole optimizer
  where it could read bytes beyond the end of bounds of an array when
  removing unreachable code. This bug was present in every release of Python
  3.6 and 3.7 until now.

- bpo-35169: Improved error messages for forbidden assignments.

- bpo-34022: Fix handling of hash-based bytecode files in :mod:`zipimport`.
  Patch by Elvis Pranskevichus.

- bpo-28401: Debug builds will no longer to attempt to import extension
  modules built for the ABI as they were never compatible to begin with.
  Patch by Stefano Rivera.

- bpo-29341: Clarify in the docstrings of :mod:`os` methods that path-like
  objects are also accepted as input parameters.

- bpo-35050: :mod:`socket`: Fix off-by-one bug in length check for
  ``AF_ALG`` name and type.

- bpo-29743: Raise :exc:`ValueError` instead of :exc:`OverflowError` in case
  of a negative ``_length_`` in a :class:`ctypes.Array` subclass.  Also
  raise :exc:`TypeError` instead of :exc:`AttributeError` for non-integer
  ``_length_``. Original patch by Oren Milman.

- bpo-16806: Fix ``lineno`` and ``col_offset`` for multi-line string tokens.

- bpo-35029: :exc:`SyntaxWarning` raised as an exception at code generation
  time will be now replaced with a :exc:`SyntaxError` for better error
  reporting.

- bpo-34983: Expose :meth:`symtable.Symbol.is_nonlocal` in the symtable
  module. Patch by Pablo Galindo.

- bpo-34974: :class:`bytes` and :class:`bytearray` constructors no longer
  convert unexpected exceptions (e.g. :exc:`MemoryError` and
  :exc:`KeyboardInterrupt`) to :exc:`TypeError`.

- bpo-34939: Allow annotated names in module namespace that are declared
  global before the annotation happens. Patch by Pablo Galindo.

- bpo-34973: Fixed crash in :func:`bytes` when the :class:`list` argument is
  mutated while it is iterated.

- bpo-34876: The *lineno* and *col_offset* attributes of the AST for
  decorated function and class refer now to the position of the
  corresponding ``def``, ``async def`` and ``class`` instead of the position
  of the first decorator. This leads to more correct line reporting in
  tracing. This is the only case when the position of child AST nodes can
  precede the position of the parent AST node.

- bpo-34879: Fix a possible null pointer dereference in bytesobject.c.
  Patch by Zackery Spytz.

- bpo-34784: Fix the implementation of PyStructSequence_NewType in order to
  create heap allocated StructSequences.

- bpo-32912: A :exc:`SyntaxWarning` is now emitted instead of a
  :exc:`DeprecationWarning` for invalid escape sequences in string and bytes
  literals.

- bpo-34854: Fixed a crash in compiling string annotations containing a
  lambda with a keyword-only argument that doesn't have a default value.

- bpo-34850: The compiler now produces a :exc:`SyntaxWarning` when identity
  checks (``is`` and ``is not``) are used with certain types of literals
  (e.g. strings, ints).  These can often work by accident in CPython, but
  are not guaranteed by the language spec.  The warning advises users to use
  equality tests (``==`` and ``!=``) instead.

- bpo-34824: Fix a possible null pointer dereference in Modules/_ssl.c.
  Patch by Zackery Spytz.

- bpo-30156: The C function ``property_descr_get()`` uses a "cached" tuple
  to optimize function calls. But this tuple can be discovered in debug mode
  with :func:`sys.getobjects()`. Remove the optimization, it's not really
  worth it and it causes 3 different crashes last years.

- bpo-34762: Fix contextvars C API to use PyObject* pointer types.

- bpo-34751: The hash function for tuples is now based on xxHash which gives
  better collision results on (formerly) pathological cases. Additionally,
  on 64-bit systems it improves tuple hashes in general. Patch by Jeroen
  Demeyer with substantial contributions by Tim Peters.

- bpo-34735: Fix a memory leak in Modules/timemodule.c.  Patch by Zackery
  Spytz.

- bpo-34683: Fixed a bug where some SyntaxError error pointed to locations
  that were off-by-one.

- bpo-34651: Only allow the main interpreter to fork.  The avoids the
  possibility of affecting the main interpreter, which is critical to
  operation of the runtime.

- bpo-34653: Remove unused function PyParser_SimpleParseStringFilename.

- bpo-32236: Warn that line buffering is not supported if :func:`open` is
  called with binary mode and ``buffering=1``.

- bpo-34641: Further restrict the syntax of the left-hand side of keyword
  arguments in function calls. In particular, ``f((keyword)=arg)`` is now
  disallowed.

- bpo-34637: Make the *start* argument to *sum()* visible as a keyword
  argument.

- bpo-1621: Do not assume signed integer overflow behavior (C undefined
  behavior) when performing set hash table resizing.

- bpo-34588: Fix an off-by-one in the recursive call pruning feature of
  traceback formatting.

- bpo-34485: On Windows, the LC_CTYPE is now set to the user preferred
  locale at startup. Previously, the LC_CTYPE locale was "C" at startup, but
  changed when calling setlocale(LC_CTYPE, "") or setlocale(LC_ALL, "").

- bpo-34485: Standard streams like sys.stdout now use the "surrogateescape"
  error handler, instead of "strict", on the POSIX locale (when the C locale
  is not coerced and the UTF-8 Mode is disabled).

- bpo-34485: Fix the error handler of standard streams like sys.stdout:
  PYTHONIOENCODING=":" is now ignored instead of setting the error handler
  to "strict".

- bpo-34485: Python now gets the locale encoding with C code to initialize
  the encoding of standard streams like sys.stdout. Moreover, the encoding
  is now initialized to the Python codec name to get a normalized encoding
  name and to ensure that the codec is loaded. The change avoids importing
  _bootlocale and _locale modules at startup by default.

- bpo-34527: On FreeBSD, Py_DecodeLocale() and Py_EncodeLocale() now also
  forces the ASCII encoding if the LC_CTYPE locale is "POSIX", not only if
  the LC_CTYPE locale is "C".

- bpo-34527: The UTF-8 Mode is now also enabled by the "POSIX" locale, not
  only by the "C" locale.

- bpo-34403: On HP-UX with C or POSIX locale, sys.getfilesystemencoding()
  now returns "ascii" instead of "roman8" (when the UTF-8 Mode is disabled
  and the C locale is not coerced).

- bpo-34523: The Python filesystem encoding is now read earlier during the
  Python initialization.

- bpo-12458: Tracebacks show now correct line number for subexpressions in
  multiline expressions. Tracebacks show now the line number of the first
  line for multiline expressions instead of the line number of the last
  subexpression.

- bpo-34408: Prevent a null pointer dereference and resource leakage in
  ``PyInterpreterState_New()``.

- bpo-34400: Fix undefined behavior in parsetok.c.  Patch by Zackery Spytz.

- bpo-33073: Added as_integer_ratio to ints to make them more interoperable
  with floats.

- bpo-34377: Update valgrind suppression list to use
  ``_PyObject_Free``/``_PyObject_Realloc`` instead of
  ``PyObject_Free``/``PyObject_Realloc``.

- bpo-34353: Added the "socket" option in the `stat.filemode()` Python
  implementation to match the C implementation.

- bpo-34320: Fix ``dict(od)`` didn't copy iteration order of OrderedDict.

- bpo-34113: Fixed crash on debug builds when opcode stack was adjusted with
  negative numbers. Patch by Constantin Petrisor.

- bpo-34100: Compiler now merges constants in tuples and frozensets
  recursively. Code attributes like ``co_names`` are merged too.

- bpo-34151: Performance of list concatenation, repetition and slicing
  operations is slightly improved. Patch by Sergey Fedoseev.

- bpo-34170: -X dev: it is now possible to override the memory allocator
  using PYTHONMALLOC even if the developer mode is enabled.

- bpo-33237: Improved :exc:`AttributeError` message for partially
  initialized module.

- bpo-34149: Fix min and max functions to get default behavior when key is
  None.

- bpo-34125: Profiling of unbound built-in methods now works when
  ``**kwargs`` is given.

- bpo-34141: Optimized pickling atomic types (None, bool, int, float, bytes,
  str).

- bpo-34126: Fix crashes when profiling certain invalid calls of unbound
  methods. Patch by Jeroen Demeyer.

- bpo-24618: Fixed reading invalid memory when create the code object with
  too small varnames tuple or too large argument counts.

- bpo-34068: In :meth:`io.IOBase.close`, ensure that the
  :attr:`~io.IOBase.closed` attribute is not set with a live exception.
  Patch by Zackery Spytz and Serhiy Storchaka.

- bpo-34087: Fix buffer overflow while converting unicode to numeric values.

- bpo-34080: Fixed a memory leak in the compiler when it raised some
  uncommon errors during tokenizing.

- bpo-34066: Disabled interruption by Ctrl-C between calling ``open()`` and
  entering a **with** block in ``with open()``.

- bpo-34042: Fix dict.copy() to maintain correct total refcount (as reported
  by sys.gettotalrefcount()).

- bpo-33418: Fix potential memory leak in function object when it creates
  reference cycle.

- bpo-33985: Implement contextvars.ContextVar.name attribute.

- bpo-33956: Update vendored Expat library copy to version 2.2.5.

- bpo-24596: Decref the module object in :c:func:`PyRun_SimpleFileExFlags`
  before calling :c:func:`PyErr_Print()`.  Patch by Zackery Spytz.

- bpo-33451: Close directly executed pyc files before calling
  ``PyEval_EvalCode()``.

- bpo-1617161: The hash of :class:`BuiltinMethodType` instances (methods of
  built-in classes) now depends on the hash of the identity of *__self__*
  instead of its value. The hash and equality of :class:`ModuleType` and
  :class:`MethodWrapperType` instances (methods of user-defined classes and
  some methods of built-in classes like ``str.__add__``) now depend on the
  hash and equality of the identity of *__self__* instead of its value.
  :class:`MethodWrapperType` instances no longer support ordering.

- bpo-33824: Fix "LC_ALL=C python3.7 -V": reset properly the command line
  parser when the encoding changes after reading the Python configuration.

- bpo-33803: Fix a crash in hamt.c caused by enabling GC tracking for an
  object that hadn't all of its fields set to NULL.

- bpo-33738: Seven macro incompatibilities with the Limited API were fixed,
  and the macros :c:func:`PyIter_Check`, :c:func:`PyIndex_Check` and
  :c:func:`PyExceptionClass_Name` were added as functions. A script for
  automatic macro checks was added.

- bpo-33786: Fix asynchronous generators to handle GeneratorExit in athrow()
  correctly

- bpo-30167: ``PyRun_SimpleFileExFlags`` removes ``__cached__`` from module
  in addition to ``__file__``.

- bpo-33706: Fix a crash in Python initialization when parsing the command
  line options. Thanks Christoph Gohlke for the bug report and the fix!

- bpo-33597: Reduce ``PyGC_Head`` size from 3 words to 2 words.

- bpo-30654: Fixed reset of the SIGINT handler to SIG_DFL on interpreter
  shutdown even when there was a custom handler set previously. Patch by
  Philipp Kerling.

- bpo-33622: Fixed a leak when the garbage collector fails to add an object
  with the ``__del__`` method or referenced by it into the
  :data:`gc.garbage` list. :c:func:`PyGC_Collect` can now be called when an
  exception is set and preserves it.

- bpo-33462: Make dict and dict views reversible. Patch by Rémi Lapeyre.

- bpo-23722: A :exc:`RuntimeError` is now raised when the custom metaclass
  doesn't provide the ``__classcell__`` entry in the namespace passed to
  ``type.__new__``.  A :exc:`DeprecationWarning` was emitted in Python
  3.6--3.7.

- bpo-33499: Add :envvar:`PYTHONPYCACHEPREFIX` environment variable and
  :option:`-X` ``pycache_prefix`` command-line option to set an alternate
  root directory for writing module bytecode cache files.

- bpo-25711: The :mod:`zipimport` module has been rewritten in pure Python.

- bpo-33509: Fix module_globals parameter of warnings.warn_explicit(): don't
  crash if module_globals is not a dict.

- bpo-31849: Fix signed/unsigned comparison warning in pyhash.c.

- bpo-33475: Fixed miscellaneous bugs in converting annotations to strings
  and optimized parentheses in the string representation.

- bpo-20104: Added support for the `setpgroup`, `resetids`, `setsigmask`,
  `setsigdef` and `scheduler` parameters of `posix_spawn`. Patch by Pablo
  Galindo.

- bpo-33391: Fix a leak in set_symmetric_difference().

- bpo-33363: Raise a SyntaxError for ``async with`` and ``async for``
  statements outside of async functions.

- bpo-28055: Fix unaligned accesses in siphash24(). Patch by Rolf Eike Beer.

- bpo-33128: Fix a bug that causes PathFinder to appear twice on
  sys.meta_path. Patch by Pablo Galindo Salgado.

- bpo-33331: Modules imported last are now cleared first at interpreter
  shutdown.

- bpo-33312: Fixed clang ubsan (undefined behavior sanitizer) warnings in
  dictobject.c by adjusting how the internal struct _dictkeysobject shared
  keys structure is declared.

- bpo-33305: Improved syntax error messages for invalid numerical literals.

- bpo-33306: Improved syntax error messages for unbalanced parentheses.

- bpo-33234: The list constructor will pre-size and not over-allocate when
  the input length is known.

- bpo-33270: Intern the names for all anonymous code objects.  Patch by
  Zackery Spytz.

- bpo-30455: The C and Python code and the documentation related to tokens
  are now generated from a single source file :file:`Grammar/Tokens`.

- bpo-33176: Add a ``toreadonly()`` method to memoryviews.

- bpo-33231: Fix potential memory leak in ``normalizestring()``.

- bpo-33205: Change dict growth function from
  ``round_up_to_power_2(used*2+hashtable_size/2)`` to
  ``round_up_to_power_2(used*3)``.  Previously, dict is shrinked only when
  ``used == 0``. Now dict has more chance to be shrinked.

- bpo-29922: Improved error messages in 'async with' when ``__aenter__()``
  or ``__aexit__()`` return non-awaitable object.

- bpo-33199: Fix ``ma_version_tag`` in dict implementation is uninitialized
  when copying from key-sharing dict.

- bpo-33053: When using the -m switch, sys.path[0] is now explicitly
  expanded as the *starting* working directory, rather than being left as
  the empty path (which allows imports from the current working directory at
  the time of the import)

- bpo-33138: Changed standard error message for non-pickleable and
  non-copyable types. It now says "cannot pickle" instead of "can't pickle"
  or "cannot serialize".

- bpo-33018: Improve consistency of errors raised by ``issubclass()`` when
  called with a non-class and an abstract base class as the first and second
  arguments, respectively. Patch by Josh Bronson.

- bpo-33083: ``math.factorial`` no longer accepts arguments that are not
  int-like. Patch by Pablo Galindo.

- bpo-33041: Added new opcode :opcode:`END_ASYNC_FOR` and fixes the
  following issues:

  * Setting global :exc:`StopAsyncIteration` no longer breaks ``async for``
    loops.
  * Jumping into an ``async for`` loop is now disabled.
  * Jumping out of an ``async for`` loop no longer corrupts the stack.

- bpo-25750: Fix rare Python crash due to bad refcounting in
  ``type_getattro()`` if a descriptor deletes itself from the class. Patch
  by Jeroen Demeyer.

- bpo-33041: Fixed bytecode generation for "async for" with a complex
  target. A StopAsyncIteration raised on assigning or unpacking will be now
  propagated instead of stopping the iteration.

- bpo-33026: Fixed jumping out of "with" block by setting f_lineno.

- bpo-33005: Fix a crash on fork when using a custom memory allocator (ex:
  using PYTHONMALLOC env var). _PyGILState_Reinit() and
  _PyInterpreterState_Enable() now use the default RAW memory allocator to
  allocate a new interpreters mutex on fork.

- bpo-32911: Due to unexpected compatibility issues discovered during
  downstream beta testing, reverted :issue:`29463`. ``docstring`` field is
  removed from Module, ClassDef, FunctionDef, and AsyncFunctionDef ast nodes
  which was added in 3.7a1.  Docstring expression is restored as a first
  statement in their body. Based on patch by Inada Naoki.

- bpo-17288: Prevent jumps from 'return' and 'exception' trace events.

- bpo-32946: Importing names from already imported module with "from ...
  import ..." is now 30% faster if the module is not a package.

- bpo-32932: Make error message more revealing when there are non-str
  objects in ``__all__``.

- bpo-32925: Optimized iterating and containing test for literal lists
  consisting of non-constants: ``x in [a, b]`` and ``for x in [a, b]``. The
  case of all constant elements already was optimized.

- bpo-32889: Update Valgrind suppression list to account for the rename of
  ``Py_ADDRESS_IN_RANG`` to ``address_in_range``.

- bpo-32836: Don't use temporary variables in cases of list/dict/set
  comprehensions

- bpo-31356: Remove the new API added in bpo-31356 (gc.ensure_disabled()
  context manager).

- bpo-32305: For namespace packages, ensure that both ``__file__`` and
  ``__spec__.origin`` are set to None.

- bpo-32303: Make sure ``__spec__.loader`` matches ``__loader__`` for
  namespace packages.

- bpo-32711: Fix the warning messages for Python/ast_unparse.c. Patch by
  Stéphane Wirtel

- bpo-32583: Fix possible crashing in builtin Unicode decoders caused by
  write out-of-bound errors when using customized decode error handlers.

- bpo-32489: A :keyword:`continue` statement is now allowed in the
  :keyword:`finally` clause.

- bpo-17611: Simplified the interpreter loop by moving the logic of
  unrolling the stack of blocks into the compiler. The compiler emits now
  explicit instructions for adjusting the stack of values and calling the
  cleaning up code for :keyword:`break`, :keyword:`continue` and
  :keyword:`return`.

  Removed opcodes :opcode:`BREAK_LOOP`, :opcode:`CONTINUE_LOOP`,
  :opcode:`SETUP_LOOP` and :opcode:`SETUP_EXCEPT`. Added new opcodes
  :opcode:`ROT_FOUR`, :opcode:`BEGIN_FINALLY` and :opcode:`CALL_FINALLY` and
  :opcode:`POP_FINALLY`. Changed the behavior of :opcode:`END_FINALLY` and
  :opcode:`WITH_CLEANUP_START`.

- bpo-32285: New function unicodedata.is_normalized, which can check whether
  a string is in a specific normal form.

- bpo-10544: Yield expressions are now disallowed in comprehensions and
  generator expressions except the expression for the outermost iterable.

- bpo-32117: Iterable unpacking is now allowed without parentheses in yield
  and return statements, e.g. ``yield 1, 2, 3, *rest``. Thanks to David
  Cuthbert for the change and Jordan Chapman for added tests.

- bpo-31902: Fix the ``col_offset`` attribute for ast nodes
  ``ast.AsyncFor``, ``ast.AsyncFunctionDef``, and ``ast.AsyncWith``.
  Previously, ``col_offset`` pointed to the keyword after ``async``.

- bpo-25862: Fix assertion failures in the ``tell()`` method of
  ``io.TextIOWrapper``. Patch by Zackery Spytz.

- bpo-21983: Fix a crash in `ctypes.cast()` in case the type argument is a
  ctypes structured data type. Patch by Eryk Sun and Oren Milman.

- bpo-31577: Fix a crash in `os.utime()` in case of a bad ns argument. Patch
  by Oren Milman.

- bpo-29832: Remove references to 'getsockaddrarg' from various socket error
  messages. Patch by Oren Milman.

Library
-------

- bpo-35845: Add 'order' parameter to memoryview.tobytes().

- bpo-35864: The _asdict() method for collections.namedtuple now returns a
  regular dict instead of an OrderedDict.

- bpo-35537: An ExitStack is now used internally within subprocess.Popen to
  clean up pipe file handles. No behavior change in normal operation. But if
  closing one handle were ever to cause an exception, the others will now be
  closed instead of leaked.  (patch by Giampaolo Rodola)

- bpo-35847: RISC-V needed the CTYPES_PASS_BY_REF_HACK.  Fixes ctypes
  Structure test_pass_by_value.

- bpo-35813: Shared memory submodule added to multiprocessing to avoid need
  for serialization between processes

- bpo-35780: Fix lru_cache() errors arising in recursive, reentrant, or
  multi-threaded code. These errors could result in orphan links and in the
  cache being trapped in a state with fewer than the specified maximum
  number of links. Fix handling of negative maxsize which should have been
  treated as zero. Fix errors in toggling the "full" status flag. Fix
  misordering of links when errors are encountered.  Sync-up the C code and
  pure Python code for the space saving path in functions with a single
  positional argument. In this common case, the space overhead of an lru
  cache entry is reduced by almost half.  Fix counting of cache misses. In
  error cases, the miss count was out of sync with the actual number of
  times the underlying user function was called.

- bpo-35537: :func:`os.posix_spawn` and :func:`os.posix_spawnp` now have a
  *setsid* parameter.

- bpo-23846: :class:`asyncio.ProactorEventLoop` now catches and logs send
  errors when the self-pipe is full.

- bpo-34323: :mod:`asyncio`: Enhance ``IocpProactor.close()`` log: wait 1
  second before the first log, then log every second. Log also the number of
  seconds since ``close()`` was called.

- bpo-35674: Add a new :func:`os.posix_spawnp` function. Patch by Joannah
  Nanjekye.

- bpo-35733: ``ast.Constant(boolean)`` no longer an instance of
  :class:`ast.Num`.  Patch by Anthony Sottile.

- bpo-35726: QueueHandler.prepare() now makes a copy of the record before
  modifying and enqueueing it, to avoid affecting other handlers in the
  chain.

- bpo-35719: Sped up multi-argument :mod:`math` functions atan2(),
  copysign(), remainder() and hypot() by 1.3--2.5 times.

- bpo-35717: Fix KeyError exception raised when using enums and compile.
  Patch contributed by Rémi Lapeyre.

- bpo-35699: Fixed detection of Visual Studio Build Tools 2017 in distutils

- bpo-32710: Fix memory leaks in asyncio ProactorEventLoop on overlapped
  operation failure.

- bpo-35702: The :data:`time.CLOCK_UPTIME_RAW` constant is now available for
  macOS 10.12.

- bpo-32710: Fix a memory leak in asyncio in the ProactorEventLoop when
  ``ReadFile()`` or ``WSASend()`` overlapped operation fail immediately:
  release the internal buffer.

- bpo-35682: Fix ``asyncio.ProactorEventLoop.sendfile()``: don't attempt to
  set the result of an internal future if it's already done.

- bpo-35283: Add a deprecated warning for the
  :meth:`threading.Thread.isAlive` method. Patch by Dong-hee Na.

- bpo-35664: Improve operator.itemgetter() performance by 33% with optimized
  argument handling and with adding a fast path for the common case of a
  single non-negative integer index into a tuple (which is the typical use
  case in the standard library).

- bpo-35643: Fixed a SyntaxWarning: invalid escape sequence in
  Modules/_sha3/cleanup.py. Patch by Mickaël Schoentgen.

- bpo-35619: Improved support of custom data descriptors in :func:`help` and
  :mod:`pydoc`.

- bpo-28503: The `crypt` module now internally uses the `crypt_r()` library
  function instead of `crypt()` when available.

- bpo-35614: Fixed help() on metaclasses. Patch by Sanyam Khurana.

- bpo-35568: Expose ``raise(signum)`` as `raise_signal`

- bpo-35588: The floor division and modulo operations and the :func:`divmod`
  function on :class:`fractions.Fraction` types are 2--4x faster. Patch by
  Stefan Behnel.

- bpo-35585: Speed-up building enums by value, e.g. http.HTTPStatus(200).

- bpo-30561: random.gammavariate(1.0, beta) now computes the same result as
  random.expovariate(1.0 / beta).  This synchronizes the two algorithms and
  eliminates some idiosyncrasies in the old implementation.  It does however
  produce a difference stream of random variables than it used to.

- bpo-35537: The :mod:`subprocess` module can now use the
  :func:`os.posix_spawn` function in some cases for better performance.

- bpo-35526: Delaying the 'joke' of barry_as_FLUFL.mandatory to Python
  version 4.0

- bpo-35523: Remove :mod:`ctypes` callback workaround: no longer create a
  callback at startup. Avoid SELinux alert on ``import ctypes`` and ``import
  uuid``.

- bpo-31784: :func:`uuid.uuid1` now calls :func:`time.time_ns` rather than
  ``int(time.time() * 1e9)``.

- bpo-35513: :class:`~unittest.runner.TextTestRunner` of
  :mod:`unittest.runner` now uses :func:`time.perf_counter` rather than
  :func:`time.time` to measure the execution time of a test:
  :func:`time.time` can go backwards, whereas :func:`time.perf_counter` is
  monotonic.

- bpo-35502: Fixed reference leaks in
  :class:`xml.etree.ElementTree.TreeBuilder` in case of unfinished building
  of the tree (in particular when an error was raised during parsing XML).

- bpo-35348: Make :func:`platform.architecture` parsing of ``file`` command
  output more reliable: add the ``-b`` option to the ``file`` command to
  omit the filename, force the usage of the C locale, and search also the
  "shared object" pattern.

- bpo-35491: :mod:`multiprocessing`: Add ``Pool.__repr__()`` and enhance
  ``BaseProcess.__repr__()`` (add pid and parent pid) to ease debugging.
  Pool state constant values are now strings instead of integers, for
  example ``RUN`` value becomes ``'RUN'`` instead of ``0``.

- bpo-35477: :meth:`multiprocessing.Pool.__enter__` now fails if the pool is
  not running: ``with pool:`` fails if used more than once.

- bpo-31446: Copy command line that was passed to CreateProcessW since this
  function can change the content of the input buffer.

- bpo-35471: Python 2.4 dropped MacOS 9 support. The macpath module was
  deprecated in Python 3.7. The module is now removed.

- bpo-23057: Unblock Proactor event loop when keyboard interrupt is received
  on Windows

- bpo-35052: Fix xml.dom.minidom cloneNode() on a document with an entity:
  pass the correct arguments to the user data handler of an entity.

- bpo-20239: Allow repeated assignment deletion of
  :class:`unittest.mock.Mock` attributes. Patch by Pablo Galindo.

- bpo-17185: Set ``__signature__`` on mock for :mod:`inspect` to get
  signature. Patch by Karthikeyan Singaravelan.

- bpo-35445: Memory errors during creating posix.environ no longer ignored.

- bpo-35415: Validate fileno= argument to socket.socket().

- bpo-35424: :class:`multiprocessing.Pool` destructor now emits
  :exc:`ResourceWarning` if the pool is still running.

- bpo-35330: When a :class:`Mock` instance was used to wrap an object, if
  `side_effect` is used in one of the mocks of it methods, don't call the
  original implementation and return the result of using the side effect the
  same way that it is done with return_value.

- bpo-35346: Drop Mac OS 9 and Rhapsody support from the :mod:`platform`
  module. Rhapsody last release was in 2000. Mac OS 9 last release was in
  2001.

- bpo-10496: :func:`~distutils.utils.check_environ` of
  :mod:`distutils.utils` now catches :exc:`KeyError` on calling
  :func:`pwd.getpwuid`: don't create the ``HOME`` environment variable in
  this case.

- bpo-10496: :func:`posixpath.expanduser` now returns the input *path*
  unchanged if the ``HOME`` environment variable is not set and the current
  user has no home directory (if the current user identifier doesn't exist
  in the password database). This change fix the :mod:`site` module if the
  current user doesn't exist in the password database (if the user has no
  home directory).

- bpo-35389: :func:`platform.libc_ver` now uses
  ``os.confstr('CS_GNU_LIBC_VERSION')`` if available and the *executable*
  parameter is not set.

- bpo-35394: Add empty slots to asyncio abstract protocols.

- bpo-35310: Fix a bug in :func:`select.select` where, in some cases, the
  file descriptor sequences were returned unmodified after a signal
  interruption, even though the file descriptors might not be ready yet.
  :func:`select.select` will now always return empty lists if a timeout has
  occurred.  Patch by Oran Avraham.

- bpo-35380: Enable TCP_NODELAY on Windows for proactor asyncio event loop.

- bpo-35341: Add generic version of ``collections.OrderedDict`` to the
  ``typing`` module. Patch by Ismo Toijala.

- bpo-35371: Fixed possible crash in ``os.utime()`` on Windows when pass
  incorrect arguments.

- bpo-35346: :func:`platform.uname` now redirects ``stderr`` to
  :data:`os.devnull` when running external programs like ``cmd /c ver``.

- bpo-35066: Previously, calling the strftime() method on a datetime object
  with a trailing '%' in the format string would result in an exception.
  However, this only occurred when the datetime C module was being used; the
  python implementation did not match this behavior. Datetime is now PEP-399
  compliant, and will not throw an exception on a trailing '%'.

- bpo-35345: The function `platform.popen` has been removed, it was
  deprecated since Python 3.3: use :func:`os.popen` instead.

- bpo-35344: On macOS, :func:`platform.platform` now uses
  :func:`platform.mac_ver`, if it returns a non-empty release string, to get
  the macOS version rather than the darwin version.

- bpo-35312: Make ``lib2to3.pgen2.parse.ParseError`` round-trip pickle-able.
  Patch by Anthony Sottile.

- bpo-35308: Fix regression in ``webbrowser`` where default browsers may be
  preferred over browsers in the ``BROWSER`` environment variable.

- bpo-24746: Avoid stripping trailing whitespace in doctest fancy diff.
  Original patch by R. David Murray & Jairo Trad. Enhanced by Sanyam
  Khurana.

- bpo-28604: :func:`locale.localeconv` now sets temporarily the ``LC_CTYPE``
  locale to the ``LC_MONETARY`` locale if the two locales are different and
  monetary strings are non-ASCII. This temporary change affects other
  threads.

- bpo-35277: Update ensurepip to install pip 18.1 and setuptools 40.6.2.

- bpo-24209: Adds IPv6 support when invoking http.server directly.

- bpo-35226: Recursively check arguments when testing for equality of
  :class:`unittest.mock.call` objects and add note that tracking of
  parameters used to create ancestors of mocks in ``mock_calls`` is not
  possible.

- bpo-29564: The warnings module now suggests to enable tracemalloc if the
  source is specified, the tracemalloc module is available, but tracemalloc
  is not tracing memory allocations.

- bpo-35189: Modify the following fnctl function to retry if interrupted by
  a signal (EINTR): flock, lockf, fnctl

- bpo-30064: Use add_done_callback() in sock_* asyncio API to unsubscribe
  reader/writer early on calcellation.

- bpo-35186: Removed the "built with" comment added when ``setup.py upload``
  is used with either ``bdist_rpm`` or ``bdist_dumb``.

- bpo-35152: Allow sending more than 2 GB at once on a multiprocessing
  connection on non-Windows systems.

- bpo-35062: Fix incorrect parsing of
  :class:`_io.IncrementalNewlineDecoder`'s *translate* argument.

- bpo-35065: Remove `StreamReaderProtocol._untrack_reader`. The call to
  `_untrack_reader` is currently performed too soon, causing the protocol to
  forget about the reader before `connection_lost` can run and feed the EOF
  to the reader.

- bpo-34160: ElementTree and minidom now preserve the attribute order
  specified by the user.

- bpo-35079: Improve difflib.SequenceManager.get_matching_blocks doc by
  adding 'non-overlapping' and changing '!=' to '<'.

- bpo-33710: Deprecated ``l*gettext()`` functions and methods in the
  :mod:`gettext` module. They return encoded bytes instead of Unicode
  strings and are artifacts from Python 2 times. Also deprecated functions
  and methods related to setting the charset for ``l*gettext()`` functions
  and methods.

- bpo-35017: :meth:`socketserver.BaseServer.serve_forever` now exits
  immediately if it's :meth:`~socketserver.BaseServer.shutdown` method is
  called while it is polling for new events.

- bpo-35024: `importlib` no longer logs `wrote <bytecode path>` redundantly
  after `(created|could not create) <bytecode path>` is already logged.
  Patch by Quentin Agren.

- bpo-35047: ``unittest.mock`` now includes mock calls in exception messages
  if ``assert_not_called``, ``assert_called_once``, or
  ``assert_called_once_with`` fails. Patch by Petter Strandmark.

- bpo-31047: Fix ``ntpath.abspath`` regression where it didn't remove a
  trailing separator on Windows. Patch by Tim Graham.

- bpo-35053: tracemalloc now tries to update the traceback when an object is
  reused from a "free list" (optimization for faster object creation, used
  by the builtin list type for example).

- bpo-31553: Add the --json-lines option to json.tool. Patch by hongweipeng.

- bpo-34794: Fixed a leak in Tkinter when pass the Python wrapper around
  Tcl_Obj back to Tcl/Tk.

- bpo-34909: Enum: fix grandchildren subclassing when parent mixed with
  concrete data types.

- bpo-35022: :class:`unittest.mock.MagicMock` now supports the
  ``__fspath__`` method (from :class:`os.PathLike`).

- bpo-35008: Fixed references leaks when call the ``__setstate__()`` method
  of :class:`xml.etree.ElementTree.Element` in the C implementation for
  already initialized element.

- bpo-23420: Verify the value for the parameter '-s' of the cProfile CLI.
  Patch by Robert Kuska

- bpo-33947: dataclasses now handle recursive reprs without raising
  RecursionError.

- bpo-34890: Make :func:`inspect.iscoroutinefunction`,
  :func:`inspect.isgeneratorfunction` and :func:`inspect.isasyncgenfunction`
  work with :func:`functools.partial`. Patch by Pablo Galindo.

- bpo-34521: Use :func:`socket.CMSG_SPACE` to calculate ancillary data size
  instead of :func:`socket.CMSG_LEN` in
  :func:`multiprocessing.reduction.recvfds` as :rfc:`3542` requires the use
  of the former for portable applications.

- bpo-31522: The `mailbox.mbox.get_string` function *from_* parameter can
  now successfully be set to a non-default value.

- bpo-34970: Protect tasks weak set manipulation in ``asyncio.all_tasks()``

- bpo-34969: gzip: Add --fast, --best on the gzip CLI, these parameters will
  be used for the fast compression method (quick) or the best method
  compress (slower, but smaller file). Also, change the default compression
  level to 6 (tradeoff).

- bpo-16965: The :term:`2to3` :2to3fixer:`execfile` fixer now opens the file
  with mode ``'rb'``.  Patch by Zackery Spytz.

- bpo-34966: :mod:`pydoc` now supports aliases not only to methods defined
  in the end class, but also to inherited methods.  The docstring is not
  duplicated for aliases.

- bpo-34926: :meth:`mimetypes.MimeTypes.guess_type` now accepts
  :term:`path-like object` in addition to url strings. Patch by Mayank
  Asthana.

- bpo-23831: Add ``moveto()`` method to the ``tkinter.Canvas`` widget. Patch
  by Juliette Monsel.

- bpo-34941: Methods ``find()``, ``findtext()`` and ``findall()`` of the
  ``Element`` class in the :mod:`xml.etree.ElementTree` module are now able
  to find children which are instances of ``Element`` subclasses.

- bpo-32680: :class:`smtplib.SMTP` objects now always have a `sock`
  attribute present

- bpo-34769: Fix for async generators not finalizing when event loop is in
  debug mode and garbage collector runs in another thread.

- bpo-34936: Fix ``TclError`` in ``tkinter.Spinbox.selection_element()``.
  Patch by Juliette Monsel.

- bpo-34829: Add methods ``selection_from``, ``selection_range``,
  ``selection_present`` and ``selection_to`` to the ``tkinter.Spinbox`` for
  consistency with the ``tkinter.Entry`` widget. Patch by Juliette Monsel.

- bpo-34911: Added *secure_protocols* argument to
  *http.cookiejar.DefaultCookiePolicy* to allow for tweaking of protocols
  and also to add support by default for *wss*, the secure websocket
  protocol.

- bpo-34922: Fixed integer overflow in the :meth:`~hashlib.shake.digest()`
  and :meth:`~hashlib.shake.hexdigest()` methods for the SHAKE algorithm in
  the :mod:`hashlib` module.

- bpo-34925: 25% speedup in argument parsing for the functions in the bisect
  module.

- bpo-34900: Fixed :meth:`unittest.TestCase.debug` when used to call test
  methods with subtests.  Patch by Bruno Oliveira.

- bpo-34844: logging.Formatter enhancement - Ensure styles and fmt matches
  in logging.Formatter - Added validate method in each format style class:
  StrFormatStyle, PercentStyle, StringTemplateStyle. - This method is called
  in the constructor of logging.Formatter class - Also re-raise the KeyError
  in the format method of each style class, so it would a bit clear that
  it's an error with the invalid format fields.

- bpo-34897: Adjust test.support.missing_compiler_executable check so that a
  nominal command name of "" is ignored. Patch by Michael Felt.

- bpo-34871: Fix inspect module polluted ``sys.modules`` when parsing
  ``__text_signature__`` of callable.

- bpo-34898: Add `mtime` argument to `gzip.compress` for reproducible
  output. Patch by Guo Ci Teo.

- bpo-28441: On Cygwin and MinGW, ensure that ``sys.executable`` always
  includes the full filename in the path, including the ``.exe`` suffix
  (unless it is a symbolic link).

- bpo-34866: Adding ``max_num_fields`` to ``cgi.FieldStorage`` to make DOS
  attacks harder by limiting the number of ``MiniFieldStorage`` objects
  created by ``FieldStorage``.

- bpo-34711: http.server ensures it reports HTTPStatus.NOT_FOUND when the
  local path ends with "/" and is not a directory, even if the underlying OS
  (e.g. AIX) accepts such paths as a valid file reference. Patch by Michael
  Felt.

- bpo-34872: Fix self-cancellation in C implementation of asyncio.Task

- bpo-34849: Don't log waiting for ``selector.select`` in asyncio loop
  iteration. The waiting is pretty normal for any asyncio program, logging
  its time just adds a noise to logs without any useful information
  provided.

- bpo-34022: The :envvar:`SOURCE_DATE_EPOCH` environment variable no longer
  overrides the value of the *invalidation_mode* argument to
  :func:`py_compile.compile`, and determines its default value instead.

- bpo-34819: Use a monotonic clock to compute timeouts in
  :meth:`Executor.map` and :func:`as_completed`, in order to prevent
  timeouts from deviating when the system clock is adjusted.

- bpo-34758: Add .wasm -> application/wasm to list of recognized file types
  and content type headers

- bpo-34789: :func:`xml.sax.make_parser` now accepts any iterable as its
  *parser_list* argument.  Patch by Andrés Delfino.

- bpo-34334: In :class:`QueueHandler`, clear `exc_text` from
  :class:`LogRecord` to prevent traceback from being written twice.

- bpo-34687: On Windows, asyncio now uses ProactorEventLoop, instead of
  SelectorEventLoop, by default.

- bpo-5950: Support reading zip files with archive comments in
  :mod:`zipimport`.

- bpo-32892: The parser now represents all constants as
  :class:`ast.Constant` instead of using specific constant AST types
  (``Num``, ``Str``, ``Bytes``, ``NameConstant`` and ``Ellipsis``). These
  classes are considered deprecated and will be removed in future Python
  versions.

- bpo-34728: Add deprecation warning when `loop` is used in methods:
  `asyncio.sleep`, `asyncio.wait` and `asyncio.wait_for`.

- bpo-34738: ZIP files created by :mod:`distutils` will now include entries
  for directories.

- bpo-34659: Add an optional *initial* argument to itertools.accumulate().

- bpo-29577: Support multiple mixin classes when creating Enums.

- bpo-34670: Add SSLContext.post_handshake_auth and
  SSLSocket.verify_client_post_handshake for TLS 1.3's post handshake
  authentication feature.

- bpo-32718: The Activate.ps1 script from venv works with PowerShell Core
  6.1 and is now available under all operating systems.

- bpo-31177: Fix bug that prevented using :meth:`reset_mock
  <unittest.mock.Mock.reset_mock>` on mock instances with deleted attributes

- bpo-34672: Add a workaround, so the ``'Z'`` :func:`time.strftime`
  specifier on the musl C library can work in some cases.

- bpo-34666: Implement ``asyncio.StreamWriter.awrite`` and
  ``asyncio.StreamWriter.aclose()`` coroutines.  Methods are needed for
  providing a consistent stream API with control flow switched on by
  default.

- bpo-6721: Acquire the logging module's commonly used internal locks while
  fork()ing to avoid deadlocks in the child process.

- bpo-34658: Fix a rare interpreter unhandled exception state SystemError
  only seen when using subprocess with a preexec_fn while an after_parent
  handler has been registered with os.register_at_fork and the fork system
  call fails.

- bpo-34652: Ensure :func:`os.lchmod` is never defined on Linux.

- bpo-34638: Store a weak reference to stream reader to break strong
  references loop between reader and protocol.  It allows to detect and
  close the socket if the stream is deleted (garbage collected) without
  ``close()`` call.

- bpo-34536: `Enum._missing_`:  raise `ValueError` if None returned and
  `TypeError` if non-member is returned.

- bpo-34636: Speed up re scanning of many non-matching characters for \s \w
  and \d within bytes objects. (microoptimization)

- bpo-24412: Add :func:`~unittest.addModuleCleanup()` and
  :meth:`~unittest.TestCase.addClassCleanup()` to unittest to support
  cleanups for :func:`~unittest.setUpModule()` and
  :meth:`~unittest.TestCase.setUpClass()`. Patch by Lisa Roach.

- bpo-34630: Don't log SSL certificate errors in asyncio code (connection
  error logging is skipped already).

- bpo-32490: Prevent filename duplication in :mod:`subprocess` exception
  messages.  Patch by Zackery Spytz.

- bpo-34363: dataclasses.asdict() and .astuple() now handle namedtuples
  correctly.

- bpo-34625: Update vendorized expat library version to 2.2.6.

- bpo-32270: The subprocess module no longer mistakenly closes redirected
  fds even when they were in pass_fds when outside of the default {0, 1, 2}
  set.

- bpo-34622: Create a dedicated ``asyncio.CancelledError``,
  ``asyncio.InvalidStateError`` and ``asyncio.TimeoutError`` exception
  classes.  Inherit them from corresponding exceptions from
  ``concurrent.futures`` package. Extract ``asyncio`` exceptions into a
  separate file.

- bpo-34610: Fixed iterator of :class:`multiprocessing.managers.DictProxy`.

- bpo-34421: Fix distutils logging for non-ASCII strings.  This caused
  installation issues on Windows.

- bpo-34604: Fix possible mojibake in the error message of `pwd.getpwnam`
  and `grp.getgrnam` using string representation because of invisible
  characters or trailing whitespaces. Patch by William Grzybowski.

- bpo-30977: Make uuid.UUID use ``__slots__`` to reduce its memory
  footprint. Based on original patch by Wouter Bolsterlee.

- bpo-34574: OrderedDict iterators are not exhausted during pickling
  anymore. Patch by Sergey Fedoseev.

- bpo-8110: Refactored :mod:`subprocess` to check for Windows-specific
  modules rather than ``sys.platform == 'win32'``.

- bpo-34530: ``distutils.spawn.find_executable()`` now falls back on
  :data:`os.defpath` if the ``PATH`` environment variable is not set.

- bpo-34563: On Windows, fix multiprocessing.Connection for very large read:
  fix _winapi.PeekNamedPipe() and _winapi.ReadFile() for read larger than
  INT_MAX (usually ``2**31-1``).

- bpo-34558: Correct typo in Lib/ctypes/_aix.py

- bpo-34282: Move ``Enum._convert`` to ``EnumMeta._convert_`` and fix enum
  members getting shadowed by parent attributes.

- bpo-22872: When the queue is closed, :exc:`ValueError` is now raised by
  :meth:`multiprocessing.Queue.put` and :meth:`multiprocessing.Queue.get`
  instead of :exc:`AssertionError` and :exc:`OSError`, respectively. Patch
  by Zackery Spytz.

- bpo-34515: Fix parsing non-ASCII identifiers in
  :mod:`lib2to3.pgen2.tokenize` (PEP 3131).

- bpo-13312: Avoids a possible integer underflow (undefined behavior) in the
  time module's year handling code when passed a very low negative year
  value.

- bpo-34472: Improved compatibility for streamed files in :mod:`zipfile`.
  Previously an optional signature was not being written and certain ZIP
  applications were not supported. Patch by Silas Sewell.

- bpo-34454: Fix the .fromisoformat() methods of datetime types crashing
  when given unicode with non-UTF-8-encodable code points.  Specifically,
  datetime.fromisoformat() now accepts surrogate unicode code points used as
  the separator. Report and tests by Alexey Izbyshev, patch by Paul Ganssle.

- bpo-6700: Fix inspect.getsourcelines for module level frames/tracebacks.
  Patch by Vladimir Matveev.

- bpo-34171: Running the :mod:`trace` module no longer creates the
  ``trace.cover`` file.

- bpo-34441: Fix crash when an ``ABC``-derived class with invalid
  ``__subclasses__`` is passed as the second argument to
  :func:`issubclass()`. Patch by Alexey Izbyshev.

- bpo-34427: Fix infinite loop in ``a.extend(a)`` for ``MutableSequence``
  subclasses.

- bpo-34412: Make :func:`signal.strsignal` work on HP-UX. Patch by Michael
  Osipov.

- bpo-20849: shutil.copytree now accepts a new ``dirs_exist_ok`` keyword
  argument. Patch by Josh Bronson.

- bpo-31715: Associate ``.mjs`` file extension with
  ``application/javascript`` MIME Type.

- bpo-34384: :func:`os.readlink` now accepts :term:`path-like <path-like
  object>` and :class:`bytes` objects on Windows.

- bpo-22602: The UTF-7 decoder now raises :exc:`UnicodeDecodeError` for
  ill-formed sequences starting with "+" (as specified in RFC 2152).  Patch
  by Zackery Spytz.

- bpo-2122: The :meth:`mmap.flush() <mmap.mmap.flush>` method now returns
  ``None`` on success, raises an exception on error under all platforms.

- bpo-34341: Appending to the ZIP archive with the ZIP64 extension no longer
  grows the size of extra fields of existing entries.

- bpo-34333: Fix %-formatting in :meth:`pathlib.PurePath.with_suffix` when
  formatting an error message.

- bpo-18540: The :class:`imaplib.IMAP4` and :class:`imaplib.IMAP4_SSL`
  classes now resolve to the local host IP correctly when the default value
  of *host* parameter (``''``) is used.

- bpo-26502: Implement ``traceback.FrameSummary.__len__()`` method to
  preserve compatibility with the old tuple API.

- bpo-34318: :func:`~unittest.TestCase.assertRaises`,
  :func:`~unittest.TestCase.assertRaisesRegex`,
  :func:`~unittest.TestCase.assertWarns` and
  :func:`~unittest.TestCase.assertWarnsRegex` no longer success if the
  passed callable is None. They no longer ignore unknown keyword arguments
  in the context manager mode. A DeprecationWarning was raised in these
  cases since Python 3.5.

- bpo-9372: Deprecate :meth:`__getitem__` methods of
  :class:`xml.dom.pulldom.DOMEventStream`, :class:`wsgiref.util.FileWrapper`
  and :class:`fileinput.FileInput`.

- bpo-33613: Fix a race condition in ``multiprocessing.semaphore_tracker``
  when the tracker receives SIGINT before it can register signal handlers
  for ignoring it.

- bpo-34248: Report filename in the exception raised when the database file
  cannot be opened by :func:`dbm.gnu.open` and :func:`dbm.ndbm.open` due to
  OS-related error. Patch by Zsolt Cserna.

- bpo-33089: Add math.dist() to compute the Euclidean distance between two
  points.

- bpo-34246: :meth:`smtplib.SMTP.send_message` no longer modifies the
  content of the *mail_options* argument. Patch by Pablo S. Blum de Aguiar.

- bpo-31047: Fix ``ntpath.abspath`` for invalid paths on windows. Patch by
  Franz Woellert.

- bpo-32321: Add pure Python fallback for functools.reduce. Patch by Robert
  Wright.

- bpo-34270: The default asyncio task class now always has a name which can
  be get or set using two new methods (:meth:`~asyncio.Task.get_name()` and
  :meth:`~asyncio.Task.set_name`) and is visible in the :func:`repr` output.
  An initial name can also be set using the new ``name`` keyword argument to
  :func:`asyncio.create_task` or the
  :meth:`~asyncio.AbstractEventLoop.create_task` method of the event loop.
  If no initial name is set, the default Task implementation generates a
  name like ``Task-1`` using a monotonic counter.

- bpo-34263: asyncio's event loop will not pass timeouts longer than one day
  to epoll/select etc.

- bpo-34035: Fix several AttributeError in zipfile seek() methods. Patch by
  Mickaël Schoentgen.

- bpo-32215: Fix performance regression in :mod:`sqlite3` when a DML
  statement appeared in a different line than the rest of the SQL query.

- bpo-34075: Deprecate passing non-ThreadPoolExecutor instances to
  :meth:`AbstractEventLoop.set_default_executor`.

- bpo-34251: Restore ``msilib.Win64`` to preserve backwards compatibility
  since it's already used by :mod:`distutils`' ``bdist_msi`` command.

- bpo-19891: Ignore errors caused by missing / non-writable homedir while
  writing history during exit of an interactive session.  Patch by Anthony
  Sottile.

- bpo-33089: Enhanced math.hypot() to support more than two dimensions.

- bpo-34228: tracemalloc: PYTHONTRACEMALLOC=0 environment variable and -X
  tracemalloc=0 command line option are now allowed to disable explicitly
  tracemalloc at startup.

- bpo-13041: Use :func:`shutil.get_terminal_size` to calculate the terminal
  width correctly in the ``argparse.HelpFormatter`` class.  Initial patch by
  Zbyszek Jędrzejewski-Szmek.

- bpo-34213: Allow frozen dataclasses to have a field named "object".
  Previously this conflicted with an internal use of "object".

- bpo-34052: :meth:`sqlite3.Connection.create_aggregate`,
  :meth:`sqlite3.Connection.create_function`,
  :meth:`sqlite3.Connection.set_authorizer`,
  :meth:`sqlite3.Connection.set_progress_handler` methods raises TypeError
  when unhashable objects are passed as callable. These methods now don't
  pass such objects to SQLite API. Previous behavior could lead to
  segfaults. Patch by Sergey Fedoseev.

- bpo-34197: Attributes *skipinitialspace*, *doublequote* and *strict* of
  the *dialect* attribute of the :mod:`csv` reader are now :class:`bool`
  instances instead of integers 0 or 1.

- bpo-32788: Errors other than :exc:`TypeError` raised in methods
  ``__adapt__()`` and ``__conform__()`` in the :mod:`sqlite3` module are now
  propagated to the user.

- bpo-21446: The :2to3fixer:`reload` fixer now uses :func:`importlib.reload`
  instead of deprecated :func:`imp.reload`.

- bpo-940286: pydoc's ``Helper.showtopic()`` method now prints the cross
  references of a topic correctly.

- bpo-34164: :func:`base64.b32decode` could raise UnboundLocalError or
  OverflowError for incorrect padding.  Now it always raises
  :exc:`base64.Error` in these cases.

- bpo-33729: Fixed issues with arguments parsing in :mod:`hashlib`.

- bpo-34097: ZipFile can zip files older than 1980-01-01 and newer than
  2107-12-31 using a new ``strict_timestamps`` parameter at the cost of
  setting the timestamp to the limit.

- bpo-34108: Remove extraneous CR in 2to3 refactor.

- bpo-34070: Make sure to only check if the handle is a tty, when opening a
  file with ``buffering=-1``.

- bpo-27494: Reverted :issue:`27494`. 2to3 rejects now a trailing comma in
  generator expressions.

- bpo-33967: functools.singledispatch now raises TypeError instead of
  IndexError when no positional arguments are passed.

- bpo-34041: Add the parameter *deterministic* to the
  :meth:`sqlite3.Connection.create_function` method. Patch by Sergey
  Fedoseev.

- bpo-34056: Ensure the loader shim created by ``imp.load_module`` always
  returns bytes from its ``get_data()`` function. This fixes using
  ``imp.load_module`` with :pep:`552` hash-based pycs.

- bpo-34054: The multiprocessing module now uses the monotonic clock
  :func:`time.monotonic` instead of the system clock :func:`time.time` to
  implement timeout.

- bpo-34043: Optimize tarfile uncompress performance about 15% when gzip is
  used.

- bpo-34044: ``subprocess.Popen`` now copies the *startupinfo* argument to
  leave it unchanged: it will modify the copy, so that the same
  ``STARTUPINFO`` object can be used multiple times.

- bpo-34010: Fixed a performance regression for reading streams with
  tarfile. The buffered read should use a list, instead of appending to a
  bytes object.

- bpo-34019: webbrowser: Correct the arguments passed to Opera Browser when
  opening a new URL using the ``webbrowser`` module. Patch by Bumsik Kim.

- bpo-34003: csv.DictReader now creates dicts instead of OrderedDicts. Patch
  by Michael Selik.

- bpo-33978: Closed existing logging handlers before reconfiguration via
  fileConfig and dictConfig. Patch by Karthikeyan Singaravelan.

- bpo-14117: Make minor tweaks to turtledemo. The 'wikipedia' example is now
  'rosette', describing what it draws.  The 'penrose' print output is
  reduced. The'1024' output of 'tree' is eliminated.

- bpo-33974: Fixed passing lists and tuples of strings containing special
  characters ``"``, ``\``, ``{``, ``}`` and ``\n`` as options to
  :mod:`~tkinter.ttk` widgets.

- bpo-27500: Fix getaddrinfo to resolve IPv6 addresses correctly.

- bpo-24567: Improve random.choices() to handle subnormal input weights that
  could occasionally trigger an IndexError.

- bpo-33871: Fixed integer overflow in :func:`os.readv`, :func:`os.writev`,
  :func:`os.preadv` and :func:`os.pwritev` and in :func:`os.sendfile` with
  *headers* or *trailers* arguments (on BSD-based OSes and macOS).

- bpo-25007: Add :func:`copy.copy` and :func:`copy.deepcopy` support to zlib
  compressors and decompressors.  Patch by Zackery Spytz.

- bpo-33929: multiprocessing: Fix a race condition in Popen of
  multiprocessing.popen_spawn_win32. The child process now duplicates the
  read end of pipe instead of "stealing" it. Previously, the read end of
  pipe was "stolen" by the child process, but it leaked a handle if the
  child process had been terminated before it could steal the handle from
  the parent process.

- bpo-33899: Tokenize module now implicitly emits a NEWLINE when provided
  with input that does not have a trailing new line.  This behavior now
  matches what the C tokenizer does internally.  Contributed by Ammar Askar.

- bpo-33897: Added a 'force' keyword argument to logging.basicConfig().

- bpo-33695: :func:`shutil.copytree` uses :func:`os.scandir` function and
  all copy functions depending from it use cached :func:`os.stat` values.
  The speedup for copying a directory with 8000 files is around +9% on
  Linux, +20% on Windows and + 30% on a Windows SMB share. Also the number
  of :func:`os.stat` syscalls is reduced by 38% making
  :func:`shutil.copytree` especially faster on network filesystems.
  (Contributed by Giampaolo Rodola' in :issue:`33695`.)

- bpo-33916: bz2 and lzma: When Decompressor.__init__() is called twice,
  free the old lock to not leak memory.

- bpo-32568: Make select.epoll() and its documentation consistent regarding
  *sizehint* and *flags*.

- bpo-33833: Fixed bug in asyncio where ProactorSocketTransport logs
  AssertionError if force closed during write.

- bpo-33663: Convert content length to string before putting to header.

- bpo-33721: :mod:`os.path` functions that return a boolean result like
  :func:`~os.path.exists`, :func:`~os.path.lexists`, :func:`~os.path.isdir`,
  :func:`~os.path.isfile`, :func:`~os.path.islink`, and
  :func:`~os.path.ismount`, and :mod:`pathlib.Path` methods that return a
  boolean result like :meth:`~pathlib.Path.exists()`,
  :meth:`~pathlib.Path.is_dir()`, :meth:`~pathlib.Path.is_file()`,
  :meth:`~pathlib.Path.is_mount()`, :meth:`~pathlib.Path.is_symlink()`,
  :meth:`~pathlib.Path.is_block_device()`,
  :meth:`~pathlib.Path.is_char_device()`, :meth:`~pathlib.Path.is_fifo()`,
  :meth:`~pathlib.Path.is_socket()` now return ``False`` instead of raising
  :exc:`ValueError` or its subclasses :exc:`UnicodeEncodeError` and
  :exc:`UnicodeDecodeError` for paths that contain characters or bytes
  unrepresentable at the OS level.

- bpo-26544: Fixed implementation of :func:`platform.libc_ver`. It almost
  always returned version '2.9' for glibc.

- bpo-33843: Remove deprecated ``cgi.escape``, ``cgi.parse_qs`` and
  ``cgi.parse_qsl``.

- bpo-33842: Remove ``tarfile.filemode`` which is deprecated since Python
  3.3.

- bpo-30167: Prevent site.main() exception if PYTHONSTARTUP is set. Patch by
  Steve Weber.

- bpo-33805: Improve error message of dataclasses.replace() when an InitVar
  is not specified

- bpo-33687: Fix the call to ``os.chmod()`` for ``uu.decode()`` if a mode is
  given or decoded. Patch by Timo Furrer.

- bpo-33812: Datetime instance d with non-None tzinfo, but with
  d.tzinfo.utcoffset(d) returning None is now treated as naive by the
  astimezone() method.

- bpo-32108: In configparser, don't clear section when it is assigned to
  itself.

- bpo-27397: Make email module properly handle invalid-length base64
  strings.

- bpo-33578: Implement multibyte encoder/decoder state methods

- bpo-30805: Avoid race condition with debug logging

- bpo-33476: Fix _header_value_parser.py when address group is missing final
  ';'. Contributed by Enrique Perez-Terron

- bpo-33694: asyncio: Fix a race condition causing data loss on
  pause_reading()/resume_reading() when using the ProactorEventLoop.

- bpo-32493: Correct test for ``uuid_enc_be`` availability in
  ``configure.ac``. Patch by Michael Felt.

- bpo-33792: Add asyncio.WindowsSelectorEventLoopPolicy and
  asyncio.WindowsProactorEventLoopPolicy.

- bpo-33274: W3C DOM Level 1 specifies return value of
  Element.removeAttributeNode() as "The Attr node that was removed."
  xml.dom.minidom now complies with this requirement.

- bpo-33778: Update ``unicodedata``'s database to Unicode version 11.0.0.

- bpo-33165: Added a stacklevel parameter to logging calls to allow use of
  wrapper/helper functions for logging APIs.

- bpo-33770: improve base64 exception message for encoded inputs of invalid
  length

- bpo-33769: asyncio/start_tls: Fix error message; cancel callbacks in case
  of an unhandled error; mark SSLTransport as closed if it is aborted.

- bpo-33767: The concatenation (``+``) and repetition (``*``) sequence
  operations now raise :exc:`TypeError` instead of :exc:`SystemError` when
  performed on :class:`mmap.mmap` objects.  Patch by Zackery Spytz.

- bpo-33734: asyncio/ssl: Fix AttributeError, increase default handshake
  timeout

- bpo-31014: Fixed creating a controller for :mod:`webbrowser` when a user
  specifies a path to an entry in the BROWSER environment variable.  Based
  on patch by John Still.

- bpo-2504: Add gettext.pgettext() and variants.

- bpo-33197: Add description property for _ParameterKind

- bpo-32751: When cancelling the task due to a timeout,
  :meth:`asyncio.wait_for` will now wait until the cancellation is complete.

- bpo-32684: Fix gather to propagate cancellation of itself even with
  return_exceptions.

- bpo-33654: Support protocol type switching in SSLTransport.set_protocol().

- bpo-33674: Pause the transport as early as possible to further reduce the
  risk of data_received() being called before connection_made().

- bpo-33671: :func:`shutil.copyfile`, :func:`shutil.copy`,
  :func:`shutil.copy2`, :func:`shutil.copytree` and :func:`shutil.move` use
  platform-specific fast-copy syscalls on Linux and macOS in order to copy
  the file more efficiently. On Windows :func:`shutil.copyfile` uses a
  bigger default buffer size (1 MiB instead of 16 KiB) and a
  :func:`memoryview`-based variant of :func:`shutil.copyfileobj` is used.
  The speedup for copying a 512MiB file is about +26% on Linux, +50% on
  macOS and +40% on Windows. Also, much less CPU cycles are consumed.
  (Contributed by Giampaolo Rodola' in :issue:`25427`.)

- bpo-33674: Fix a race condition in SSLProtocol.connection_made() of
  asyncio.sslproto: start immediately the handshake instead of using
  call_soon(). Previously, data_received() could be called before the
  handshake started, causing the handshake to hang or fail.

- bpo-31647: Fixed bug where calling write_eof() on a
  _SelectorSocketTransport after it's already closed raises AttributeError.

- bpo-32610: Make asyncio.all_tasks() return only pending tasks.

- bpo-32410: Avoid blocking on file IO in sendfile fallback code

- bpo-33469: Fix RuntimeError after closing loop that used run_in_executor

- bpo-33672: Fix Task.__repr__ crash with Cython's bogus coroutines

- bpo-33654: Fix transport.set_protocol() to support switching between
  asyncio.Protocol and asyncio.BufferedProtocol.  Fix loop.start_tls() to
  work with asyncio.BufferedProtocols.

- bpo-33652: Pickles of type variables and subscripted generics are now
  future-proof and compatible with older Python versions.

- bpo-32493: Fixed :func:`uuid.uuid1` on FreeBSD.

- bpo-33238: Add ``InvalidStateError`` to :mod:`concurrent.futures`.
  ``Future.set_result`` and ``Future.set_exception`` now raise
  ``InvalidStateError`` if the futures are not pending or running. Patch by
  Jason Haydaman.

- bpo-33618: Finalize and document preliminary and experimental TLS 1.3
  support with OpenSSL 1.1.1

- bpo-33625: Release GIL on `grp.getgrnam`, `grp.getgrgid`, `pwd.getpwnam`
  and `pwd.getpwuid` if reentrant variants of these functions are available.
  Patch by William Grzybowski.

- bpo-33623: Fix possible SIGSGV when asyncio.Future is created in __del__

- bpo-11874: Use a better regex when breaking usage into wrappable parts.
  Avoids bogus assertion errors from custom metavar strings.

- bpo-30877: Fixed a bug in the Python implementation of the JSON decoder
  that prevented the cache of parsed strings from clearing after finishing
  the decoding. Based on patch by c-fos.

- bpo-33604: Remove HMAC default to md5 marked for removal in 3.8 (removal
  originally planned in 3.6, bump to 3.8 in PR 7062).

- bpo-33582: Emit a deprecation warning for inspect.formatargspec

- bpo-21145: Add ``functools.cached_property`` decorator, for computed
  properties cached for the life of the instance.

- bpo-33570: Change TLS 1.3 cipher suite settings for compatibility with
  OpenSSL 1.1.1-pre6 and newer. OpenSSL 1.1.1 will have TLS 1.3 ciphers
  enabled by default.

- bpo-28556: Do not simplify arguments to `typing.Union`. Now
  `Union[Manager, Employee]` is not simplified to `Employee` at runtime.
  Such simplification previously caused several bugs and limited
  possibilities for introspection.

- bpo-12486: :func:`tokenize.generate_tokens` is now documented as a public
  API to tokenize unicode strings. It was previously present but
  undocumented.

- bpo-33540: Add a new ``block_on_close`` class attribute to
  ``ForkingMixIn`` and ``ThreadingMixIn`` classes of :mod:`socketserver`.

- bpo-33548: tempfile._candidate_tempdir_list should consider common TEMP
  locations

- bpo-33109: argparse subparsers are once again not required by default,
  reverting the change in behavior introduced by bpo-26510 in 3.7.0a2.

- bpo-33541: Remove unused private method ``_strptime.LocaleTime.__pad``
  (a.k.a. ``_LocaleTime__pad``).

- bpo-33536: dataclasses.make_dataclass now checks for invalid field names
  and duplicate fields. Also, added a check for invalid field
  specifications.

- bpo-33542: Prevent ``uuid.get_node`` from using a DUID instead of a MAC on
  Windows. Patch by Zvi Effron

- bpo-26819: Fix race condition with `ReadTransport.resume_reading` in
  Windows proactor event loop.

- Fix failure in `typing.get_type_hints()` when ClassVar was provided as a
  string forward reference.

- bpo-33516: :class:`unittest.mock.MagicMock` now supports the ``__round__``
  magic method.

- bpo-28612: Added support for Site Maps to urllib's ``RobotFileParser`` as
  :meth:`RobotFileParser.site_maps()
  <urllib.robotparser.RobotFileParser.site_maps>`. Patch by Lady Red, based
  on patch by Peter Wirtz.

- bpo-28167: Remove platform.linux_distribution, which was deprecated since
  3.5.

- bpo-33504: Switch the default dictionary implementation for
  :mod:`configparser` from :class:`collections.OrderedDict` to the standard
  :class:`dict` type.

- bpo-33505: Optimize asyncio.ensure_future() by reordering if checks: 1.17x
  faster.

- bpo-33497: Add errors param to cgi.parse_multipart and make an encoding in
  FieldStorage use the given errors (needed for Twisted).  Patch by Amber
  Brown.

- bpo-29235: The :class:`cProfile.Profile` class can now be used as a
  context manager. Patch by Scott Sanderson.

- bpo-33495: Change dataclasses.Fields repr to use the repr of each of its
  members, instead of str.  This makes it more clear what each field
  actually represents.  This is especially true for the 'type' member.

- bpo-26103: Correct ``inspect.isdatadescriptor`` to look for ``__set__`` or
  ``__delete__``.  Patch by Aaron Hall.

- bpo-29209: Removed the ``doctype()`` method and the *html* parameter of
  the constructor of :class:`~xml.etree.ElementTree.XMLParser`.  The
  ``doctype()`` method defined in a subclass will no longer be called.
  Deprecated methods ``getchildren()`` and ``getiterator()`` in the
  :mod:`~xml.etree.ElementTree` module emit now a :exc:`DeprecationWarning`
  instead of :exc:`PendingDeprecationWarning`.

- bpo-33453: Fix dataclasses to work if using literal string type
  annotations or if using PEP 563 "Postponed Evaluation of Annotations".
  Only specific string prefixes are detected for both ClassVar ("ClassVar"
  and "typing.ClassVar") and InitVar ("InitVar" and "dataclasses.InitVar").

- bpo-28556: Minor fixes in typing module: add annotations to
  ``NamedTuple.__new__``, pass ``*args`` and ``**kwds`` in
  ``Generic.__new__``.  Original PRs by Paulius Šarka and Chad Dombrova.

- bpo-33365: Print the header values besides the header keys instead just
  the header keys if *debuglevel* is set to >0 in :mod:`http.client`. Patch
  by Marco Strigl.

- bpo-20087: Updated alias mapping with glibc 2.27 supported locales.

- bpo-33422: Fix trailing quotation marks getting deleted when looking up
  byte/string literals on pydoc. Patch by Andrés Delfino.

- bpo-28167: The function ``platform.linux_distribution`` and
  ``platform.dist`` now trigger a ``DeprecationWarning`` and have been
  marked for removal in Python 3.8

- bpo-33281: Fix ctypes.util.find_library regression on macOS.

- bpo-33311: Text and html output generated by cgitb does not display
  parentheses if the current call is done directly in the module. Patch by
  Stéphane Blondon.

- bpo-27300: The file classes in *tempfile* now accept an *errors* parameter
  that complements the already existing *encoding*.  Patch by Stephan Hohe.

- bpo-32933: :func:`unittest.mock.mock_open` now supports iteration over the
  file contents. Patch by Tony Flury.

- bpo-33217: Raise :exc:`TypeError` when looking up non-Enum objects in Enum
  classes and Enum members.

- bpo-33197: Update error message when constructing invalid
  inspect.Parameters Patch by Dong-hee Na.

- bpo-33383: Fixed crash in the get() method of the :mod:`dbm.ndbm` database
  object when it is called with a single argument.

- bpo-33375: The warnings module now finds the Python file associated with a
  warning from the code object, rather than the frame's global namespace.
  This is consistent with how tracebacks and pdb find filenames, and should
  work better for dynamically executed code.

- bpo-33336: ``imaplib`` now allows ``MOVE`` command in ``IMAP4.uid()`` (RFC
  6851: IMAP MOVE Extension) and potentially as a name of supported method
  of ``IMAP4`` object.

- bpo-32455: Added *jump* parameter to :func:`dis.stack_effect`.

- bpo-27485: Rename and deprecate undocumented functions in
  :func:`urllib.parse`.

- bpo-33332: Add ``signal.valid_signals()`` to expose the POSIX sigfillset()
  functionality.

- bpo-33251: `ConfigParser.items()` was fixed so that key-value pairs passed
  in via `vars` are not included in the resulting output.

- bpo-33329: Fix multiprocessing regression on newer glibcs

- bpo-33334: :func:`dis.stack_effect` now supports all defined opcodes
  including NOP and EXTENDED_ARG.

- bpo-991266: Fix quoting of the ``Comment`` attribute of
  :class:`http.cookies.SimpleCookie`.

- bpo-33131: Upgrade bundled version of pip to 10.0.1.

- bpo-33308: Fixed a crash in the :mod:`parser` module when converting an ST
  object to a tree of tuples or lists with ``line_info=False`` and
  ``col_info=True``.

- bpo-23403: lib2to3 now uses pickle protocol 4 for pre-computed grammars.

- bpo-33266: lib2to3 now recognizes ``rf'...'`` strings.

- bpo-11594: Ensure line-endings are respected when using lib2to3.

- bpo-33254: Have :func:`importlib.resources.contents` and
  :meth:`importlib.abc.ResourceReader.contents` return an :term:`iterable`
  instead of an :term:`iterator`.

- bpo-33265: ``contextlib.ExitStack`` and ``contextlib.AsyncExitStack`` now
  use a method instead of a wrapper function for exit callbacks.

- bpo-33263: Fix FD leak in `_SelectorSocketTransport`  Patch by Vlad
  Starostin.

- bpo-33256: Fix display of ``<module>`` call in the html produced by
  ``cgitb.html()``. Patch by Stéphane Blondon.

- bpo-33144: ``random.Random()`` and its subclassing mechanism got optimized
  to check only once at class/subclass instantiation time whether its
  ``getrandbits()`` method can be relied on by other methods, including
  ``randrange()``, for the generation of arbitrarily large random integers.
  Patch by Wolfgang Maier.

- bpo-33185: Fixed regression when running pydoc with the :option:`-m`
  switch. (The regression was introduced in 3.7.0b3 by the resolution of
  :issue:`33053`)

  This fix also changed pydoc to add ``os.getcwd()`` to :data:`sys.path`
  when necessary, rather than adding ``"."``.

- bpo-29613: Added support for the ``SameSite`` cookie flag to the
  ``http.cookies`` module.

- bpo-33169: Delete entries of ``None`` in :data:`sys.path_importer_cache`
  when :meth:`importlib.machinery.invalidate_caches` is called.

- bpo-33203: ``random.Random.choice()`` now raises ``IndexError`` for empty
  sequences consistently even when called from subclasses without a
  ``getrandbits()`` implementation.

- bpo-33224: Update difflib.mdiff() for :pep:`479`.  Convert an uncaught
  StopIteration in a generator into a return-statement.

- bpo-33209: End framing at the end of C implementation of
  :func:`pickle.Pickler.dump`.

- bpo-32861: The urllib.robotparser's ``__str__`` representation now
  includes wildcard entries and the "Crawl-delay" and "Request-rate" fields.
  Also removes extra newlines that were being appended to the end of the
  string. Patch by Michael Lazar.

- bpo-23403: ``DEFAULT_PROTOCOL`` in :mod:`pickle` was bumped to 4. Protocol
  4 is described in :pep:`3154` and available since Python 3.4. It offers
  better performance and smaller size compared to protocol 3 introduced in
  Python 3.0.

- bpo-20104: Improved error handling and fixed a reference leak in
  :func:`os.posix_spawn()`.

- bpo-33106: Deleting a key from a read-only dbm database raises module
  specific error instead of KeyError.

- bpo-33175: In dataclasses, Field.__set_name__ now looks up the
  __set_name__ special method on the class, not the instance, of the default
  value.

- bpo-32380: Create functools.singledispatchmethod to support generic single
  dispatch on descriptors and methods.

- bpo-33141: Have Field objects pass through __set_name__ to their default
  values, if they have their own __set_name__.

- bpo-33096: Allow ttk.Treeview.insert to insert iid that has a false
  boolean value. Note iid=0 and iid=False would be same. Patch by Garvit
  Khatri.

- bpo-32873: Treat type variables and special typing forms as immutable by
  copy and pickle.  This fixes several minor issues and inconsistencies, and
  improves backwards compatibility with Python 3.6.

- bpo-33134: When computing dataclass's __hash__, use the lookup table to
  contain the function which returns the __hash__ value.  This is an
  improvement over looking up a string, and then testing that string to see
  what to do.

- bpo-33127: The ssl module now compiles with LibreSSL 2.7.1.

- bpo-32505: Raise TypeError if a member variable of a dataclass is of type
  Field, but doesn't have a type annotation.

- bpo-33078: Fix the failure on OSX caused by the tests relying on
  sem_getvalue

- bpo-33116: Add 'Field' to dataclasses.__all__.

- bpo-32896: Fix an error where subclassing a dataclass with a field that
  uses a default_factory would generate an incorrect class.

- bpo-33100: Dataclasses: If a field has a default value that's a
  MemberDescriptorType, then it's from that field being in __slots__, not an
  actual default value.

- bpo-32953: If a non-dataclass inherits from a frozen dataclass, allow
  attributes to be added to the derived class.  Only attributes from the
  frozen dataclass cannot be assigned to.  Require all dataclasses in a
  hierarchy to be either all frozen or all non-frozen.

- bpo-33097: Raise RuntimeError when ``executor.submit`` is called during
  interpreter shutdown.

- bpo-32968: Modulo and floor division involving Fraction and float should
  return float.

- bpo-33061: Add missing ``NoReturn`` to ``__all__`` in typing.py

- bpo-33078: Fix the size handling in multiprocessing.Queue when a pickling
  error occurs.

- bpo-33064: lib2to3 now properly supports trailing commas after ``*args``
  and ``**kwargs`` in function signatures.

- bpo-33056: FIX properly close leaking fds in
  concurrent.futures.ProcessPoolExecutor.

- bpo-33021: Release the GIL during fstat() calls, avoiding hang of all
  threads when calling mmap.mmap(), os.urandom(), and random.seed().  Patch
  by Nir Soffer.

- bpo-31804: Avoid failing in multiprocessing.Process if the standard
  streams are closed or None at exit.

- bpo-33034: Providing an explicit error message when casting the port
  property to anything that is not an integer value using ``urlparse()`` and
  ``urlsplit()``. Patch by Matt Eaton.

- bpo-30249: Improve struct.unpack_from() exception messages for problems
  with the buffer size and offset.

- bpo-33037: Skip sending/receiving data after SSL transport closing.

- bpo-27683: Fix a regression in :mod:`ipaddress` that result of
  :meth:`hosts` is empty when the network is constructed by a tuple
  containing an integer mask and only 1 bit left for addresses.

- bpo-22674: Add the strsignal() function in the signal module that returns
  the system description of the given signal, as returned by strsignal(3).

- bpo-32999: Fix C implementation of ``ABC.__subclasscheck__(cls,
  subclass)`` crashed when ``subclass`` is not a type object.

- bpo-33009: Fix inspect.signature() for single-parameter partialmethods.

- bpo-32969: Expose several missing constants in zlib and fix corresponding
  documentation.

- bpo-32056: Improved exceptions raised for invalid number of channels and
  sample width when read an audio file in modules :mod:`aifc`, :mod:`wave`
  and :mod:`sunau`.

- bpo-32970: Improved disassembly of the MAKE_FUNCTION instruction.

- bpo-32844: Fix wrong redirection of a low descriptor (0 or 1) to stderr in
  subprocess if another low descriptor is closed.

- bpo-32960: For dataclasses, disallow inheriting frozen from non-frozen
  classes, and also disallow inheriting non-frozen from frozen classes. This
  restriction will be relaxed at a future date.

- bpo-32713: Fixed tarfile.itn handling of out-of-bounds float values. Patch
  by Joffrey Fuhrer.

- bpo-32257: The ssl module now contains OP_NO_RENEGOTIATION constant,
  available with OpenSSL 1.1.0h or 1.1.1.

- bpo-32951: Direct instantiation of SSLSocket and SSLObject objects is now
  prohibited. The constructors were never documented, tested, or designed as
  public constructors. Users were suppose to use ssl.wrap_socket() or
  SSLContext.

- bpo-32929: Remove the tri-state parameter "hash", and add the boolean
  "unsafe_hash". If unsafe_hash is True, add a __hash__ function, but if a
  __hash__ exists, raise TypeError.  If unsafe_hash is False, add a __hash__
  based on the values of eq= and frozen=.  The unsafe_hash=False behavior is
  the same as the old hash=None behavior.  unsafe_hash=False is the default,
  just as hash=None used to be.

- bpo-32947: Add OP_ENABLE_MIDDLEBOX_COMPAT and test workaround for TLSv1.3
  for future compatibility with OpenSSL 1.1.1.

- bpo-32146: Document the interaction between frozen executables and the
  spawn and forkserver start methods in multiprocessing.

- bpo-30622: The ssl module now detects missing NPN support in LibreSSL.

- bpo-32922: dbm.open() now encodes filename with the filesystem encoding
  rather than default encoding.

- bpo-32759: Free unused arenas in multiprocessing.heap.

- bpo-32859: In ``os.dup2``, don't check every call whether the ``dup3``
  syscall exists or not.

- bpo-32556: nt._getfinalpathname, nt._getvolumepathname and
  nt._getdiskusage now correctly convert from bytes.

- bpo-21060: Rewrite confusing message from setup.py upload from "No dist
  file created in earlier command" to the more helpful "Must create and
  upload files in one command".

- bpo-32857: In :mod:`tkinter`, ``after_cancel(None)`` now raises a
  :exc:`ValueError` instead of canceling the first scheduled function.
  Patch by Cheryl Sabella.

- bpo-32852: Make sure sys.argv remains as a list when running trace.

- bpo-31333: ``_abc`` module is added.  It is a speedup module with C
  implementations for various functions and methods in ``abc``.  Creating an
  ABC subclass and calling ``isinstance`` or ``issubclass`` with an ABC
  subclass are up to 1.5x faster. In addition, this makes Python start-up up
  to 10% faster.

  Note that the new implementation hides internal registry and caches,
  previously accessible via private attributes ``_abc_registry``,
  ``_abc_cache``, and ``_abc_negative_cache``.  There are three debugging
  helper methods that can be used instead ``_dump_registry``,
  ``_abc_registry_clear``, and ``_abc_caches_clear``.

- bpo-32841: Fixed `asyncio.Condition` issue which silently ignored
  cancellation after notifying and cancelling a conditional lock. Patch by
  Bar Harel.

- bpo-32819: ssl.match_hostname() has been simplified and no longer depends
  on re and ipaddress module for wildcard and IP addresses. Error reporting
  for invalid wildcards has been improved.

- bpo-19675: ``multiprocessing.Pool`` no longer leaks processes if its
  initialization fails.

- bpo-32394: socket: Remove
  TCP_FASTOPEN,TCP_KEEPCNT,TCP_KEEPIDLE,TCP_KEEPINTVL flags on older version
  Windows during run-time.

- bpo-31787: Fixed refleaks of ``__init__()`` methods in various modules.
  (Contributed by Oren Milman)

- bpo-30157: Fixed guessing quote and delimiter in csv.Sniffer.sniff() when
  only the last field is quoted.  Patch by Jake Davis.

- bpo-30688: Added support of ``\N{name}`` escapes in regular expressions.
  Based on patch by Jonathan Eunice.

- bpo-32792: collections.ChainMap() preserves the order of the underlying
  mappings.

- bpo-32775: :func:`fnmatch.translate()` no longer produces patterns which
  contain set operations. Sets starting with '[' or containing '--', '&&',
  '~~' or '||' will be interpreted differently in regular expressions in
  future versions. Currently they emit warnings. fnmatch.translate() now
  avoids producing patterns containing such sets by accident.

- bpo-32622: Implement native fast sendfile for Windows proactor event loop.

- bpo-32777: Fix a rare but potential pre-exec child process deadlock in
  subprocess on POSIX systems when marking file descriptors inheritable on
  exec in the child process.  This bug appears to have been introduced in
  3.4.

- bpo-32647: The ctypes module used to depend on indirect linking for
  dlopen. The shared extension is now explicitly linked against libdl on
  platforms with dl.

- bpo-32749: A :mod:`dbm.dumb` database opened with flags 'r' is now
  read-only. :func:`dbm.dumb.open` with flags 'r' and 'w' no longer creates
  a database if it does not exist.

- bpo-32741: Implement ``asyncio.TimerHandle.when()`` method.

- bpo-32691: Use mod_spec.parent when running modules with pdb

- bpo-32734: Fixed ``asyncio.Lock()`` safety issue which allowed acquiring
  and locking the same lock multiple times, without it being free. Patch by
  Bar Harel.

- bpo-32727: Do not include name field in SMTP envelope from address. Patch
  by Stéphane Wirtel

- bpo-31453: Add TLSVersion constants and SSLContext.maximum_version /
  minimum_version attributes. The new API wraps OpenSSL 1.1
  https://www.openssl.org/docs/man1.1.0/ssl/SSL_CTX_set_min_proto_version.html
  feature.

- bpo-24334: Internal implementation details of ssl module were cleaned up.
  The SSLSocket has one less layer of indirection. Owner and session
  information are now handled by the SSLSocket and SSLObject constructor.
  Channel binding implementation has been simplified.

- bpo-31848: Fix the error handling in Aifc_read.initfp() when the SSND
  chunk is not found. Patch by Zackery Spytz.

- bpo-32585: Add Ttk spinbox widget to :mod:`tkinter.ttk`.  Patch by Alan D
  Moore.

- bpo-32512: :mod:`profile` CLI accepts `-m module_name` as an alternative
  to script path.

- bpo-8525: help() on a type now displays builtin subclasses. This is
  intended primarily to help with notification of more specific exception
  subclasses.

  Patch by Sanyam Khurana.

- bpo-31639: http.server now exposes a ThreadingHTTPServer class and uses it
  when the module is run with ``-m`` to cope with web browsers pre-opening
  sockets.

- bpo-29877: compileall: import ProcessPoolExecutor only when needed,
  preventing hangs on low resource platforms

- bpo-32221: Various functions returning tuple containing IPv6 addresses now
  omit ``%scope`` part since the same information is already encoded in
  *scopeid* tuple item. Especially this speeds up :func:`socket.recvfrom`
  when it receives multicast packet since useless resolving of network
  interface name is omitted.

- bpo-32147: :func:`binascii.unhexlify` is now up to 2 times faster. Patch
  by Sergey Fedoseev.

- bpo-30693: The TarFile class now recurses directories in a reproducible
  way.

- bpo-30693: The ZipFile class now recurses directories in a reproducible
  way.

- bpo-31680: Added :data:`curses.ncurses_version`.

- bpo-31908: Fix output of cover files for ``trace`` module command-line
  tool. Previously emitted cover files only when ``--missing`` option was
  used. Patch by Michael Selik.

- bpo-31608: Raise a ``TypeError`` instead of crashing if a
  ``collections.deque`` subclass returns a non-deque from ``__new__``. Patch
  by Oren Milman.

- bpo-31425: Add support for sockets of the AF_QIPCRTR address family,
  supported by the Linux kernel. This is used to communicate with services,
  such as GPS or radio, running on Qualcomm devices. Patch by Bjorn
  Andersson.

- bpo-22005: Implemented unpickling instances of
  :class:`~datetime.datetime`, :class:`~datetime.date` and
  :class:`~datetime.time` pickled by Python 2. ``encoding='latin1'`` should
  be used for successful decoding.

- bpo-27645: :class:`sqlite3.Connection` now exposes a
  :class:`~sqlite3.Connection.backup` method, if the underlying SQLite
  library is at version 3.6.11 or higher.  Patch by Lele Gaifax.

- bpo-16865: Support arrays >=2GiB in :mod:`ctypes`.  Patch by Segev Finer.

- bpo-31508: Removed support of arguments in
  `tkinter.ttk.Treeview.selection`. It was deprecated in 3.6.  Use
  specialized methods like `selection_set` for changing the selection.

- bpo-29456: Fix bugs in hangul normalization: u1176, u11a7 and u11c3

Documentation
-------------

- bpo-21257: Document :func:`http.client.parse_headers`.

- bpo-34764: Improve example of iter() with 2nd sentinel argument.

- bpo-35564: Explicitly set master_doc variable in conf.py for compliance
  with Sphinx 2.0

- bpo-35511: Specified that profile.Profile class doesn't not support enable
  or disable methods. Also, elaborated that Profile object as a context
  manager is only supported in cProfile module.

- bpo-10536: Enhance the gettext docs. Patch by Éric Araujo

- bpo-35089: Remove mention of ``typing.io`` and ``typing.re``. Their types
  should be imported from ``typing`` directly.

- bpo-35038: Fix the documentation about an unexisting `f_restricted`
  attribute in the frame object. Patch by Stéphane Wirtel

- bpo-35042: Replace PEP XYZ by the pep role and allow to use the direct
  links to the PEPs.

- bpo-35044: Fix the documentation with the role ``exc`` for the
  appropriated exception. Patch by Stéphane Wirtel

- bpo-35035: Rename documentation for :mod:`email.utils` to
  ``email.utils.rst``.

- bpo-34967: Use app.add_object_type() instead of the deprecated Sphinx
  function app.description_unit()

- bpo-34913: Add documentation about the new command line interface of the
  gzip module.

- bpo-32174: chm document displays non-ASCII charaters properly on some MBCS
  Windows systems.

- bpo-11233: Create availability directive for documentation.  Original
  patch by Georg Brandl.

- bpo-34790: Document how passing coroutines to asyncio.wait() can be
  confusing.

- bpo-34552: Make clear that ``==`` operator sometimes is equivalent to
  `is`. The ``<``, ``<=``, ``>`` and ``>=`` operators are only defined where
  they make sense.

- bpo-28617: Fixed info in the stdtypes docs concerning the types that
  support membership tests.

- bpo-20177: Migrate datetime.date.fromtimestamp to Argument Clinic. Patch
  by Tim Hoffmann.

- bpo-34065: Fix wrongly written basicConfig documentation markup syntax

- bpo-33460: replaced ellipsis with correct error codes in tutorial chapter
  3.

- bpo-33847: Add '@' operator entry to index.

- bpo-33409: Clarified the relationship between :pep:`538`'s
  PYTHONCOERCECLOCALE and PEP 540's PYTHONUTF8 mode.

- bpo-33197: Add versionadded tag to the documentation of
  ParameterKind.description

- bpo-17045: Improve the C-API doc for PyTypeObject.  This includes adding
  several quick-reference tables and a lot of missing slot/typedef entries.
  The existing entries were also cleaned up with a slightly more consistent
  format.

- bpo-33736: Improve the documentation of :func:`asyncio.open_connection`,
  :func:`asyncio.start_server` and their UNIX socket counterparts.

- bpo-23859: Document that `asyncio.wait()` does not cancel its futures on
  timeout.

- bpo-32436: Document :pep:`567` changes to asyncio.

- bpo-33604: Update HMAC md5 default to a DeprecationWarning, bump removal
  to 3.8.

- bpo-33594: Document ``getargspec``, ``from_function`` and ``from_builtin``
  as deprecated in their respective docstring, and include version since
  deprecation in DeprecationWarning message.

- bpo-33503: Fix broken pypi link

- bpo-33421: Add missing documentation for ``typing.AsyncContextManager``.

- bpo-33487: BZ2file now emit a DeprecationWarning when buffering=None is
  passed, the deprecation message and documentation also now explicitly
  state it is deprecated since 3.0.

- bpo-33378: Add Korean language switcher for https://docs.python.org/3/

- bpo-33276: Clarify that the ``__path__`` attribute on modules cannot be
  just any value.

- bpo-33201: Modernize documentation for writing C extension types.

- bpo-33195: Deprecate ``Py_UNICODE`` usage in ``c-api/arg`` document.
  ``Py_UNICODE`` related APIs are deprecated since Python 3.3, but it is
  missed in the document.

- bpo-33126: Document PyBuffer_ToContiguous().

- bpo-27212: Modify documentation for the :func:`islice` recipe to consume
  initial values up to the start index.

- bpo-28247: Update :mod:`zipapp` documentation to describe how to make
  standalone applications.

- bpo-18802: Documentation changes for ipaddress.  Patch by Jon Foster and
  Berker Peksag.

- bpo-27428: Update documentation to clarify that ``WindowsRegistryFinder``
  implements ``MetaPathFinder``. (Patch by Himanshu Lakhara)

- bpo-28124: The ssl module function ssl.wrap_socket() has been
  de-emphasized and deprecated in favor of the more secure and efficient
  SSLContext.wrap_socket() method.

- bpo-17232: Clarify docs for -O and -OO.  Patch by Terry Reedy.

- bpo-32436: Add documentation for the contextvars module (PEP 567).

- bpo-32800: Update link to w3c doc for xml default namespaces.

- bpo-11015: Update :mod:`test.support` documentation.

- bpo-32613: Update the faq/windows.html to use the py command from PEP 397
  instead of python.

- bpo-8722: Document :meth:`__getattr__` behavior when property :meth:`get`
  method raises :exc:`AttributeError`.

- bpo-32614: Modify RE examples in documentation to use raw strings to
  prevent :exc:`DeprecationWarning` and add text to REGEX HOWTO to highlight
  the deprecation.

- bpo-20709: Remove the paragraph where we explain that os.utime() does not
  support a directory as path under Windows. Patch by Jan-Philip Gehrcke

- bpo-32722: Remove the bad example in the tutorial of the Generator
  Expression. Patch by Stéphane Wirtel

- bpo-31972: Improve docstrings for `pathlib.PurePath` subclasses.

- bpo-30607: Use the externalized ``python-docs-theme`` package when
  building the documentation.

- bpo-8243: Add a note about curses.addch and curses.addstr exception
  behavior when writing outside a window, or pad.

- bpo-32337: Update documentation related with ``dict`` order.

- bpo-25041: Document ``AF_PACKET`` in the :mod:`socket` module.

- bpo-31432: Clarify meaning of CERT_NONE, CERT_OPTIONAL, and CERT_REQUIRED
  flags for ssl.SSLContext.verify_mode.

Tests
-----

- bpo-35772: Fix sparse file tests of test_tarfile on ppc64 with the tmpfs
  filesystem. Fix the function testing if the filesystem supports sparse
  files: create a file which contains data and "holes", instead of creating
  a file which contains no data. tmpfs effective block size is a page size
  (tmpfs lives in the page cache). RHEL uses 64 KiB pages on aarch64, ppc64,
  ppc64le, only s390x and x86_64 use 4 KiB pages, whereas the test punch
  holes of 4 KiB.

- bpo-35045: Make ssl tests less strict and also accept TLSv1 as system
  default. The changes unbreaks test_min_max_version on Fedora 29.

- bpo-32710: ``test_asyncio/test_sendfile.py`` now resets the event loop
  policy using :func:`tearDownModule` as done in other tests, to prevent a
  warning when running tests on Windows.

- bpo-33717: test.pythoninfo now logs information of all clocks, not only
  time.time() and time.perf_counter().

- bpo-35488: Add a test to pathlib's Path.match() to verify it does not
  support glob-style ** recursive pattern matching.

- bpo-31731: Fix a race condition in ``check_interrupted_write()`` of
  test_io: create directly the thread with SIGALRM signal blocked, rather
  than blocking the signal later from the thread. Previously, it was
  possible that the thread gets the signal before the signal is blocked.

- bpo-35424: Fix test_multiprocessing_main_handling: use
  :class:`multiprocessing.Pool` with a context manager and then explicitly
  join the pool.

- bpo-35519: Rename :mod:`test.bisect` module to :mod:`test.bisect_cmd` to
  avoid conflict with :mod:`bisect` module when running directly a test like
  ``./python Lib/test/test_xmlrpc.py``.

- bpo-35513: Replace :func:`time.time` with :func:`time.monotonic` in tests
  to measure time delta.

- bpo-34279: :func:`test.support.run_unittest` no longer raise
  :exc:`TestDidNotRun` if the test result contains skipped tests. The
  exception is now only raised if no test have been run and no test have
  been skipped.

- bpo-35412: Add testcase to ``test_future4``: check unicode literal.

- bpo-26704: Added test demonstrating double-patching of an instance method.
  Patch by Anthony Sottile.

- bpo-33725: test_multiprocessing_fork may crash on recent versions of
  macOS.  Until the issue is resolved, skip the test on macOS.

- bpo-35352: Modify test_asyncio to use the certificate set from the test
  directory.

- bpo-35317: Fix ``mktime()`` overflow error in ``test_email``: run
  ``test_localtime_daylight_true_dst_true()`` and
  ``test_localtime_daylight_false_dst_true()`` with a specific timezone.

- bpo-21263: After several reports that test_gdb does not work properly on
  macOS and since gdb is not shipped by default anymore, test_gdb is now
  skipped on macOS when LLVM Clang has been used to compile Python. Patch by
  Lysandros Nikolaou

- bpo-34279: regrtest issue a warning when no tests have been executed in a
  particular test file. Also, a new final result state is issued if no test
  have been executed across all test files. Patch by Pablo Galindo.

- bpo-34962: make docstest in Doc now passes., and is enforced in CI

- bpo-23596: Use argparse for the command line of the gzip module. Patch by
  Antony Lee

- bpo-34537: Fix ``test_gdb.test_strings()`` when ``LC_ALL=C`` and GDB was
  compiled with Python 3.6 or earlier.

- bpo-34587: test_socket: Remove RDSTest.testCongestion(). The test tries to
  fill the receiver's socket buffer and expects an error. But the RDS
  protocol doesn't require that. Moreover, the Linux implementation of RDS
  expects that the producer of the messages reduces its rate, it's not the
  role of the receiver to trigger an error. The test fails on Fedora 28 by
  design, so just remove it.

- bpo-34661: Fix test_shutil if unzip doesn't support -t.

- bpo-34200: Fixed non-deterministic flakiness of test_pkg by not using the
  scary test.support.module_cleanup() logic to save and restore sys.modules
  contents between test cases.

- bpo-34569: The experimental PEP 554 data channels now correctly pass
  negative PyLong objects between subinterpreters on 32-bit systems. Patch
  by Michael Felt.

- bpo-34594: Fix usage of hardcoded ``errno`` values in the tests.

- bpo-34579: Fix test_embed for AIX Patch by Michael Felt

- bpo-34542: Use 3072 RSA keys and SHA-256 signature for test certs and
  keys.

- bpo-11193: Remove special condition for AIX in
  `test_subprocess.test_undecodable_env`

- bpo-34347: Fix `test_utf8_mode.test_cmd_line` for AIX

- bpo-34490: On AIX with AF_UNIX family sockets getsockname() does not
  provide 'sockname', so skip calls to transport.get_extra_info('sockname')

- bpo-34391: Fix ftplib test for TLS 1.3 by reading from data socket.

- bpo-11192: Fix `test_socket` on AIX 6.1 and later IPv6 zone id supports
  only supported by inet_pton6_zone() Switch to runtime-based
  platform.system() to establish current platform  rather than build-time
  based sys.platform()

- bpo-34399: Update all RSA keys and DH params to use at least 2048 bits.

- bpo-34373: Fix ``test_mktime`` and ``test_pthread_getcpuclickid`` tests
  for AIX Add range checking for ``_PyTime_localtime`` for AIX Patch by
  Michael Felt

- bpo-11191: Skip the distutils test 'test_search_cpp' when using XLC as
  compiler patch by aixtools (Michael Felt)

- Improved an error message when mock assert_has_calls fails.

- bpo-33746: Fix test_unittest when run in verbose mode.

- bpo-33901: Fix test_dbm_gnu on macOS with gdbm 1.15: add a larger value to
  make sure that the file size changes.

- bpo-33873: Fix a bug in ``regrtest`` that caused an extra test to run if
  --huntrleaks/-R was used. Exit with error in case that invalid parameters
  are specified to --huntrleaks/-R (at least one warmup run and one
  repetition must be used).

- bpo-33562: Check that a global asyncio event loop policy is not left
  behind by any tests.

- bpo-33655: Ignore test_posix_fallocate failures on BSD platforms that
  might be due to running on ZFS.

- bpo-32962: Fixed test_gdb when Python is compiled with flags -mcet
  -fcf-protection -O0.

- bpo-33358: Fix ``test_embed.test_pre_initialization_sys_options()`` when
  the interpreter is built with ``--enable-shared``.

- bpo-32872: Avoid regrtest compatibility issue with namespace packages.

- bpo-32517: Fix failing ``test_asyncio`` on macOS 10.12.2+ due to transport
  of ``KqueueSelector`` loop was not being closed.

- bpo-32663: Making sure the `SMTPUTF8SimTests` class of tests gets run in
  test_smtplib.py.

- bpo-27643: Test_C test case needs "signed short" bitfields, but the IBM
  XLC compiler (on AIX) does not support this Skip the code and test when
  AIX and XLC are used

  Applicable to Python2-2.7 and later

- bpo-19417: Add test_bdb.py.

- bpo-31809: Add tests to verify connection with secp ECDH curves.

Build
-----

- bpo-34691: The _contextvars module is now built into the core Python
  library on Windows.

- bpo-35683: Improved Azure Pipelines build steps and now verifying layouts
  correctly

- bpo-35642: Remove asynciomodule.c from pythoncore.vcxproj

- bpo-35550: Fix incorrect Solaris #ifdef checks to look for __sun && __SVR4
  instead of sun when compiling.

- bpo-35499: ``make profile-opt`` no longer replaces ``CFLAGS_NODIST`` with
  ``CFLAGS``. It now adds profile-guided optimization (PGO) flags to
  ``CFLAGS_NODIST``: existing ``CFLAGS_NODIST`` flags are kept.

- bpo-35257: Avoid leaking the linker flags from Link Time Optimizations
  (LTO) into distutils when compiling C extensions.

- bpo-35351: When building Python with clang and LTO, LTO flags are no
  longer passed into CFLAGS to build third-party C extensions through
  distutils.

- bpo-35139: Fix a compiler error when statically linking `pyexpat` in
  `Modules/Setup`.

- bpo-35059: PCbuild: Set InlineFunctionExpansion to OnlyExplicitInline
  ("/Ob1" option) in pyproject.props in Debug mode to expand functions
  marked as inline. This change should make Python compiled in Debug mode a
  little bit faster on Windows.

- bpo-35011: Restores the use of pyexpatns.h to isolate our embedded copy of
  the expat C library so that its symbols do not conflict at link or dynamic
  loading time with an embedding application or other extension modules with
  their own version of libexpat.

- bpo-28015: Have --with-lto works correctly with clang.

- bpo-34765: Update the outdated install-sh file to the latest revision from
  automake v1.16.1

- bpo-34585: Check for floating-point byte order in configure.ac using
  compilation tests instead of executing code, so that these checks work in
  cross-compiled builds.

- bpo-34710: Fixed SSL module build with OpenSSL & pedantic CFLAGS.

- bpo-34582: Add JUnit XML output for regression tests and update Azure
  DevOps builds.

- bpo-34081: Make Sphinx warnings as errors in the Docs Makefile.

- bpo-34555: Fix for case where it was not possible to have both
  ``HAVE_LINUX_VM_SOCKETS_H`` and ``HAVE_SOCKADDR_ALG`` be undefined.

- bpo-33015: Fix an undefined behaviour in the pthread implementation of
  :c:func:`PyThread_start_new_thread`: add a function wrapper to always
  return ``NULL``.

- bpo-34245: The Python shared library is now installed with write
  permission (mode 0755), which is the standard way of installing such
  libraries.

- bpo-34121: Fix detection of C11 atomic support on clang.

- bpo-32430: Rename Modules/Setup.dist to Modules/Setup, and remove the
  necessity to copy the former manually to the latter when updating the
  local source tree.

- bpo-30345: Add -g to LDFLAGS when compiling with LTO to get debug symbols.

- bpo-5755: Move ``-Wstrict-prototypes`` option to ``CFLAGS_NODIST`` from
  ``OPT``. This option emitted annoying warnings when building extension
  modules written in C++.

- bpo-33614: Ensures module definition files for the stable ABI on Windows
  are correctly regenerated.

- bpo-33648: The --with-c-locale-warning configuration flag has been
  removed. It has had no effect for about a year.

- bpo-33522: Enable CI builds on Visual Studio Team Services at
  https://python.visualstudio.com/cpython

- bpo-33512: configure's check for "long double" has been simplified

- bpo-33483: C compiler is now correctly detected from the standard
  environment variables. --without-gcc and --with-icc options have been
  removed.

- bpo-33394: Enable the verbose build for extension modules, when GNU make
  is passed macros on the command line.

- bpo-33393: Update config.guess and config.sub files.

- bpo-33377: Add new triplets for mips r6 and riscv variants (used in
  extension suffixes).

- bpo-32232: By default, modules configured in `Modules/Setup` are no longer
  built with `-DPy_BUILD_CORE`. Instead, modules that specifically need that
  preprocessor definition include it in their individual entries.

- bpo-33182: The embedding tests can once again be built with clang 6.0

- bpo-33163: Upgrade pip to 9.0.3 and setuptools to v39.0.1.

- bpo-33012: gcc 8 has added a new warning heuristic to detect invalid
  function casts and a stock python build seems to hit that warning quite
  often.  The most common is the cast of a METH_NOARGS function (that uses
  just one argument) to a PyCFunction. Fix this by adding a dummy argument
  to all functions that implement METH_NOARGS.

- bpo-32898: Fix the python debug build when using COUNT_ALLOCS.

- bpo-29442: Replace optparse with argparse in setup.py

Windows
-------

- bpo-35890: Fix API calling consistency of GetVersionEx and wcstok.

- bpo-32560: The ``py`` launcher now forwards its ``STARTUPINFO`` structure
  to child processes.

- bpo-35854: Fix EnvBuilder and --symlinks in venv on Windows

- bpo-35811: Avoid propagating venv settings when launching via py.exe

- bpo-35797: Fix default executable used by the multiprocessing module

- bpo-35758: Allow building on ARM with MSVC.

- bpo-29734: Fix handle leaks in os.stat on Windows.

- bpo-35596: Use unchecked PYCs for the embeddable distro to avoid zipimport
  restrictions.

- bpo-35596: Fix vcruntime140.dll being added to embeddable distro multiple
  times.

- bpo-35402: Update Windows build to use Tcl and Tk 8.6.9

- bpo-35401: Updates Windows build to OpenSSL 1.1.0j

- bpo-34977: venv on Windows will now use a python.exe redirector rather
  than copying the actual binaries from the base environment.

- bpo-34977: Adds support for building a Windows App Store package

- bpo-35067: Remove _distutils_findvs module and use vswhere.exe instead.

- bpo-32557: Allow shutil.disk_usage to take a file path on Windows

- bpo-34770: Fix a possible null pointer dereference in pyshellext.cpp.

- bpo-34603: Fix returning structs from functions produced by MSVC

- bpo-34581: Guard MSVC-specific code in socketmodule.c with ``#ifdef
  _MSC_VER``.

- bpo-34532: Fixes exit code of list version arguments for py.exe.

- bpo-34062: Fixed the '--list' and '--list-paths' arguments for the py.exe
  launcher

- bpo-34225: Ensure INCLUDE and LIB directories do not end with a backslash.

- bpo-34011: A suite of code has been changed which copied across DLLs and
  init.tcl from the running Python location into a venv being created. These
  copies are needed only when running from a Python source build, and the
  copying code is now only run when that is the case, rather than whenever a
  venv is created.

- bpo-34006: Revert line length limit for Windows help docs. The line-length
  limit is not needed because the pages appear in a separate app rather than
  on a browser tab.  It can also interact badly with the DPI setting.

- bpo-31546: Restore running PyOS_InputHook while waiting for user input at
  the prompt. The restores integration of interactive GUI windows (such as
  Matplotlib figures) with the prompt on Windows.

- bpo-30237: Output error when ReadConsole is canceled by
  CancelSynchronousIo instead of crashing.

- bpo-33895: GIL is released while calling functions that acquire Windows
  loader lock.

- bpo-33720: Reduces maximum marshal recursion depth on release builds.

- bpo-29097: Fix bug where :meth:`datetime.fromtimestamp` erroneously throws
  an :exc:`OSError` on Windows for values between 0 and 86400. Patch by
  Ammar Askar.

- bpo-33316: PyThread_release_lock always fails

- bpo-33184: Update Windows installer to use OpenSSL 1.1.0h.

- bpo-32890: Fix usage of GetLastError() instead of errno in os.execve() and
  os.truncate().

- bpo-33016: Fix potential use of uninitialized memory in
  nt._getfinalpathname

- bpo-32903: Fix a memory leak in os.chdir() on Windows if the current
  directory is set to a UNC path.

- bpo-32901: Update Tcl and Tk versions to 8.6.8

- bpo-31966: Fixed WindowsConsoleIO.write() for writing empty data.

- bpo-32409: Ensures activate.bat can handle Unicode contents.

- bpo-32457: Improves handling of denormalized executable path when
  launching Python.

- bpo-32370: Use the correct encoding for ipconfig output in the uuid
  module. Patch by Segev Finer.

- bpo-29248: Fix :func:`os.readlink` on Windows, which was mistakenly
  treating the ``PrintNameOffset`` field of the reparse data buffer as a
  number of characters instead of bytes. Patch by Craig Holmquist and SSE4.

- bpo-1104: Correctly handle string length in
  ``msilib.SummaryInfo.GetProperty()`` to prevent it from truncating the
  last character.

macOS
-----

- bpo-35401: Update macOS installer to use OpenSSL 1.1.0j.

- bpo-35025: Properly guard the use of the ``CLOCK_GETTIME`` et al. macros
  in ``timemodule`` on macOS.

- bpo-24658: On macOS, fix reading from and writing into a file with a size
  larger than 2 GiB.

- bpo-34405: Update to OpenSSL 1.1.0i for macOS installer builds.

- bpo-33635: In macOS stat on some file descriptors (/dev/fd/3 f.e) will
  result in bad file descriptor OSError. Guard against this exception was
  added in is_dir, is_file and similar methods. DirEntry.is_dir can also
  throw this exception so _RecursiveWildcardSelector._iterate_directories
  was also extended with the same error ignoring pattern.

- bpo-13631: The .editrc file in user's home directory is now processed
  correctly during the readline initialization through editline emulation on
  macOS.

- bpo-33184: Update macOS installer build to use OpenSSL 1.1.0h.

- bpo-32726: Build and link with private copy of Tcl/Tk 8.6 for the macOS
  10.6+ installer. The 10.9+ installer variant already does this.  This
  means that the Python 3.7 provided by the python.org macOS installers no
  longer need or use any external versions of Tcl/Tk, either system-provided
  or user-installed, such as ActiveTcl.

- bpo-32901: Update macOS 10.9+ installer to Tcl/Tk 8.6.8.

- bpo-31903: In :mod:`_scproxy`, drop the GIL when calling into
  ``SystemConfiguration`` to avoid deadlocks.

IDLE
----

- bpo-35770: IDLE macosx deletes Options => Configure IDLE. It previously
  deleted Window => Zoom Height by mistake. (Zoom Height is now on the
  Options menu).  On Mac, the settings dialog is accessed via Preferences on
  the IDLE menu.

- bpo-35769: Change IDLE's new file name from 'Untitled' to 'untitled'

- bpo-35660: Fix imports in idlelib.window.

- bpo-35641: Proper format `calltip` when the function has no docstring.

- bpo-33987: Use ttk Frame for ttk widgets.

- bpo-34055: Fix erroneous 'smart' indents and newlines in IDLE Shell.

- bpo-35591: Find Selection now works when selection not found.

- bpo-35196: Speed up squeezer line counting.

- bpo-35598: Update config_key: use PEP 8 names and ttk widgets, make some
  objects global, and add tests.

- bpo-28097: Add Previous/Next History entries to Shell menu.

- bpo-35208: Squeezer now properly counts wrapped lines before newlines.

- bpo-35555: Gray out Code Context menu entry when it's not applicable.

- bpo-35521: Document the IDLE editor code context feature. Add some
  internal references within the IDLE doc.

- bpo-22703: The Code Context menu label now toggles between Show/Hide Code
  Context. The Zoom Height menu now toggles between Zoom/Restore Height.
  Zoom Height has moved from the Window menu to the Options menu.

- bpo-35213: Where appropriate, use 'macOS' in idlelib.

- bpo-34864: On macOS, warn if the system preference "Prefer tabs when
  opening documents" is set to "Always".

- bpo-34864: Document two IDLE on MacOS issues. The System Preferences Dock
  "prefer tabs always" setting disables some IDLE features.  Menus are a bit
  different than as described for Windows and Linux.

- bpo-35202: Remove unused imports from lib/idlelib

- bpo-33000: Document that IDLE's shell has no line limit. A program that
  runs indefinitely can overfill memory.

- bpo-23220: Explain how IDLE's Shell displays output.

- bpo-35099: Improve the doc about IDLE running user code.   The section is
  renamed from "IDLE -- console differences" is renamed "Running user code".
  It mostly covers the implications of using custom sys.stdxxx objects.

- bpo-35097: Add IDLE doc subsection explaining editor windows. Topics
  include opening, title and status bar, .py* extension, and running.

- bpo-35093: Document the IDLE document viewer in the IDLE doc. Add a
  paragraph in "Help and preferences", "Help sources" subsection.

- bpo-35088: Update idlelib.help.copy_string docstring. We now use git and
  backporting instead of hg and forward merging.

- bpo-35087: Update idlelib help files for the current doc build. The main
  change is the elimination of chapter-section numbers.

- bpo-34548: Use configured color theme for read-only text views.

- bpo-1529353: Enable "squeezing" of long outputs in the shell, to avoid
  performance degradation and to clean up the history without losing it.
  Squeezed outputs may be copied, viewed in a separate window, and
  "unsqueezed".

- bpo-34047: Fixed mousewheel scrolling direction on macOS.

- bpo-34275: Make IDLE calltips always visible on Mac. Some MacOS-tk
  combinations need .update_idletasks(). Patch by Kevin Walzer.

- bpo-34120: Fix unresponsiveness after closing certain windows and dialogs.

- bpo-33975: Avoid small type when running htests. Since part of the purpose
  of human-viewed tests is to determine that widgets look right, it is
  important that they look the same for testing as when running IDLE.

- bpo-33905: Add test for idlelib.stackview.StackBrowser.

- bpo-33924: Change mainmenu.menudefs key 'windows' to 'window'. Every other
  menudef key is lowercase version of main menu entry.

- bpo-33906: Rename idlelib.windows as window Match Window on the main menu
  and remove last plural module name.

- bpo-33917: Fix and document idlelib/idle_test/template.py. The revised
  file compiles, runs, and tests OK.  idle_test/README.txt explains how to
  use it to create new IDLE test files.

- bpo-33904: IDLE: In rstrip, rename class RstripExtension as Rstrip

- bpo-33907: For consistency and clarity, rename an IDLE module and classes.
  Module calltips and its class CallTips are now calltip and Calltip. In
  module calltip_w, class CallTip is now CalltipWindow.

- bpo-33856: Add "help" in the welcome message of IDLE

- bpo-33839: IDLE: refactor ToolTip and CallTip and add documentation and
  tests

- bpo-33855: Minimally test all IDLE modules. Add missing files, import
  module, instantiate classes, and check coverage. Check existing files.

- bpo-33656: On Windows, add API call saying that tk scales for DPI. On
  Windows 8.1+ or 10, with DPI compatibility properties of the Python binary
  unchanged, and a monitor resolution greater than 96 DPI, this should make
  text and lines sharper.  It should otherwise have no effect.

- bpo-33768: Clicking on a context line moves that line to the top of the
  editor window.

- bpo-33763: IDLE: Use read-only text widget for code context instead of
  label widget.

- bpo-33664: Scroll IDLE editor text by lines. Previously, the mouse wheel
  and scrollbar slider moved text by a fixed number of pixels, resulting in
  partial lines at the top of the editor box.  The change also applies to
  the shell and grep output windows, but not to read-only text views.

- bpo-33679: Enable theme-specific color configuration for Code Context. Use
  the Highlights tab to see the setting for built-in themes or add settings
  to custom themes.

- bpo-33642: Display up to maxlines non-blank lines for Code Context. If
  there is no current context, show a single blank line.

- bpo-33628: IDLE: Cleanup codecontext.py and its test.

- bpo-33564: IDLE's code context now recognizes async as a block opener.

- bpo-21474: Update word/identifier definition from ascii to unicode. In
  text and entry boxes, this affects selection by double-click, movement
  left/right by control-left/right, and deletion left/right by
  control-BACKSPACE/DEL.

- bpo-33204: IDLE: consistently color invalid string prefixes. A 'u' string
  prefix cannot be paired with either 'r' or 'f'. Consistently color as much
  of the prefix, starting at the right, as is valid. Revise and extend
  colorizer test.

- bpo-32984: Set ``__file__`` while running a startup file.  Like Python,
  IDLE optionally runs one startup file in the Shell window before
  presenting the first interactive input prompt.  For IDLE, ``-s`` runs a
  file named in environmental variable  :envvar:`IDLESTARTUP` or
  :envvar:`PYTHONSTARTUP`; ``-r file`` runs ``file``.  Python sets
  ``__file__`` to the startup file name before running the file and unsets
  it before the first prompt.  IDLE now does the same when run normally,
  without the ``-n`` option.

- bpo-32940: Simplify and rename StringTranslatePseudoMapping in pyparse.

- bpo-32916: Change ``str`` to ``code`` in pyparse.

- bpo-32905: Remove unused code in pyparse module.

- bpo-32874: Add tests for pyparse.

- bpo-32837: Using the system and place-dependent default encoding for
  open() is a bad idea for IDLE's system and location-independent files.

- bpo-32826: Add "encoding=utf-8" to open() in IDLE's test_help_about. GUI
  test test_file_buttons() only looks at initial ascii-only lines, but
  failed on systems where open() defaults to 'ascii' because readline()
  internally reads and decodes far enough ahead to encounter a non-ascii
  character in CREDITS.txt.

- bpo-32831: Add docstrings and tests for codecontext.

- bpo-32765: Update configdialog General tab docstring to add new widgets to
  the widget list.

Tools/Demos
-----------

- bpo-35884: Add a benchmark script for timing various ways to access
  variables: ``Tools/scripts/var_access_benchmark.py``.

- bpo-34989: python-gdb.py now handles errors on computing the line number
  of a Python frame.

- bpo-20260: Argument Clinic now has non-bitwise unsigned int converters.

- bpo-32962: python-gdb now catches ``UnicodeDecodeError`` exceptions when
  calling ``string()``.

- bpo-32962: python-gdb now catches ValueError on read_var(): when Python
  has no debug symbols for example.

- bpo-33189: :program:`pygettext.py` now recognizes only literal strings as
  docstrings and translatable strings, and rejects bytes literals and
  f-string expressions.

- bpo-31920: Fixed handling directories as arguments in the ``pygettext``
  script. Based on patch by Oleg Krasnikov.

- bpo-29673: Fix pystackv and pystack gdbinit macros.

- bpo-25427: Remove the pyvenv script in favor of ``python3 -m venv`` in
  order to lower confusion as to what Python interpreter a virtual
  environment will be created for.

- bpo-32885: Add an ``-n`` flag for ``Tools/scripts/pathfix.py`` to disable
  automatic backup creation (files with ``~`` suffix).

- bpo-32222: Fix pygettext not extracting docstrings for functions with type
  annotated arguments. Patch by Toby Harradine.

- bpo-31583: Fix 2to3 for using with --add-suffix option but without
  --output-dir option for relative path to files in current directory.

C API
-----

- bpo-35713: The :c:func:`PyByteArray_Init` and :c:func:`PyByteArray_Fini`
  functions have been removed. They did nothing since Python 2.7.4 and
  Python 3.2.0, were excluded from the limited API (stable ABI), and were
  not documented.

- bpo-33817: Fixed :c:func:`_PyBytes_Resize` for empty bytes objects.

- bpo-35322: Fix memory leak in :c:func:`PyUnicode_EncodeLocale` and
  :c:func:`PyUnicode_EncodeFSDefault` on error handling.

- bpo-35059: The following C macros have been converted to static inline
  functions: :c:func:`Py_INCREF`, :c:func:`Py_DECREF`, :c:func:`Py_XINCREF`,
  :c:func:`Py_XDECREF`, :c:func:`PyObject_INIT`,
  :c:func:`PyObject_INIT_VAR`.

- bpo-35296: ``make install`` now also installs the internal API:
  ``Include/internal/*.h`` header files.

- bpo-35081: Internal APIs surrounded by ``#ifdef Py_BUILD_CORE`` have been
  moved from ``Include/*.h`` headers to new header files
  ``Include/internal/pycore_*.h``.

- bpo-35259: Conditionally declare :c:func:`Py_FinalizeEx()` (new in 3.6)
  based on Py_LIMITED_API. Patch by Arthur Neufeld.

- bpo-35081: The :c:func:`_PyObject_GC_TRACK` and
  :c:func:`_PyObject_GC_UNTRACK` macros have been removed from the public C
  API.

- bpo-35134: Creation of a new ``Include/cpython/`` subdirectory.

- bpo-34725: Adds _Py_SetProgramFullPath so embedders may override
  sys.executable

- bpo-34910: Ensure that :c:func:`PyObject_Print` always returns ``-1`` on
  error.  Patch by Zackery Spytz.

- bpo-34523: Py_DecodeLocale() and Py_EncodeLocale() now use the UTF-8
  encoding on Windows if Py_LegacyWindowsFSEncodingFlag is zero.

- bpo-34193: Fix pluralization in TypeError messages in getargs.c and
  typeobject.c: '1 argument' instead of '1 arguments' and '1 element'
  instead of '1 elements'.

- bpo-34127: Return grammatically correct error message based on argument
  count. Patch by Karthikeyan Singaravelan.

- bpo-23927: Fixed :exc:`SystemError` in
  :c:func:`PyArg_ParseTupleAndKeywords` when the ``w*`` format unit is used
  for optional parameter.

- bpo-32455: Added :c:func:`PyCompile_OpcodeStackEffectWithJump`.

- bpo-34008: Py_Main() can again be called after Py_Initialize(), as in
  Python 3.6.

- bpo-32500: Fixed error messages for :c:func:`PySequence_Size`,
  :c:func:`PySequence_GetItem`, :c:func:`PySequence_SetItem` and
  :c:func:`PySequence_DelItem` called with a mapping and
  :c:func:`PyMapping_Size` called with a sequence.

- bpo-33818: :c:func:`PyExceptionClass_Name` will now return ``const char
  *`` instead of ``char *``.

- bpo-33042: Embedding applications may once again call
  PySys_ResetWarnOptions, PySys_AddWarnOption, and PySys_AddXOption prior to
  calling Py_Initialize.

- bpo-32374: Document that m_traverse for multi-phase initialized modules
  can be called with m_state=NULL, and add a sanity check

- bpo-30863: :c:func:`PyUnicode_AsWideChar` and
  :c:func:`PyUnicode_AsWideCharString` no longer cache the ``wchar_t*``
  representation of string objects.


What's New in Python 3.7.0 final?
=================================

*Release date: 2018-06-27*

Library
-------

- bpo-33851: Fix :func:`ast.get_docstring` for a node that lacks a
  docstring.

C API
-----

- bpo-33932: Calling Py_Initialize() twice does nothing, instead of failing
  with a fatal error: restore the Python 3.6 behaviour.


What's New in Python 3.7.0 release candidate 1?
===============================================

*Release date: 2018-06-12*

Core and Builtins
-----------------

- bpo-33803: Fix a crash in hamt.c caused by enabling GC tracking for an
  object that hadn't all of its fields set to NULL.

- bpo-33706: Fix a crash in Python initialization when parsing the command
  line options. Thanks Christoph Gohlke for the bug report and the fix!

- bpo-30654: Fixed reset of the SIGINT handler to SIG_DFL on interpreter
  shutdown even when there was a custom handler set previously. Patch by
  Philipp Kerling.

- bpo-31849: Fix signed/unsigned comparison warning in pyhash.c.

Library
-------

- bpo-30167: Prevent site.main() exception if PYTHONSTARTUP is set. Patch by
  Steve Weber.

- bpo-33812: Datetime instance d with non-None tzinfo, but with
  d.tzinfo.utcoffset(d) returning None is now treated as naive by the
  astimezone() method.

- bpo-30805: Avoid race condition with debug logging

- bpo-33694: asyncio: Fix a race condition causing data loss on
  pause_reading()/resume_reading() when using the ProactorEventLoop.

- bpo-32493: Correct test for ``uuid_enc_be`` availability in
  ``configure.ac``. Patch by Michael Felt.

- bpo-33792: Add asyncio.WindowsSelectorEventLoopPolicy and
  asyncio.WindowsProactorEventLoopPolicy.

- bpo-33778: Update ``unicodedata``'s database to Unicode version 11.0.0.

- bpo-33770: improve base64 exception message for encoded inputs of invalid
  length

- bpo-33769: asyncio/start_tls: Fix error message; cancel callbacks in case
  of an unhandled error; mark SSLTransport as closed if it is aborted.

- bpo-33767: The concatenation (``+``) and repetition (``*``) sequence
  operations now raise :exc:`TypeError` instead of :exc:`SystemError` when
  performed on :class:`mmap.mmap` objects.  Patch by Zackery Spytz.

- bpo-33734: asyncio/ssl: Fix AttributeError, increase default handshake
  timeout

- bpo-11874: Use a better regex when breaking usage into wrappable parts.
  Avoids bogus assertion errors from custom metavar strings.

- bpo-33582: Emit a deprecation warning for inspect.formatargspec

Documentation
-------------

- bpo-33409: Clarified the relationship between :pep:`538`'s
  PYTHONCOERCECLOCALE and PEP 540's PYTHONUTF8 mode.

- bpo-33736: Improve the documentation of :func:`asyncio.open_connection`,
  :func:`asyncio.start_server` and their UNIX socket counterparts.

- bpo-31432: Clarify meaning of CERT_NONE, CERT_OPTIONAL, and CERT_REQUIRED
  flags for ssl.SSLContext.verify_mode.

Build
-----

- bpo-5755: Move ``-Wstrict-prototypes`` option to ``CFLAGS_NODIST`` from
  ``OPT``. This option emitted annoying warnings when building extension
  modules written in C++.

Windows
-------

- bpo-33720: Reduces maximum marshal recursion depth on release builds.

IDLE
----

- bpo-33656: On Windows, add API call saying that tk scales for DPI. On
  Windows 8.1+ or 10, with DPI compatibility properties of the Python binary
  unchanged, and a monitor resolution greater than 96 DPI, this should make
  text and lines sharper.  It should otherwise have no effect.

- bpo-33768: Clicking on a context line moves that line to the top of the
  editor window.

- bpo-33763: IDLE: Use read-only text widget for code context instead of
  label widget.

- bpo-33664: Scroll IDLE editor text by lines. Previously, the mouse wheel
  and scrollbar slider moved text by a fixed number of pixels, resulting in
  partial lines at the top of the editor box.  The change also applies to
  the shell and grep output windows, but not to read-only text views.

- bpo-33679: Enable theme-specific color configuration for Code Context. Use
  the Highlights tab to see the setting for built-in themes or add settings
  to custom themes.

- bpo-33642: Display up to maxlines non-blank lines for Code Context. If
  there is no current context, show a single blank line.


What's New in Python 3.7.0 beta 5?
==================================

*Release date: 2018-05-30*

Core and Builtins
-----------------

- bpo-33622: Fixed a leak when the garbage collector fails to add an object
  with the ``__del__`` method or referenced by it into the
  :data:`gc.garbage` list. :c:func:`PyGC_Collect` can now be called when an
  exception is set and preserves it.

- bpo-33509: Fix module_globals parameter of warnings.warn_explicit(): don't
  crash if module_globals is not a dict.

- bpo-20104: The new `os.posix_spawn` added in 3.7.0b1 was removed as we are
  still working on what the API should look like.  Expect this in 3.8
  instead.

- bpo-33475: Fixed miscellaneous bugs in converting annotations to strings
  and optimized parentheses in the string representation.

- bpo-33391: Fix a leak in set_symmetric_difference().

- bpo-28055: Fix unaligned accesses in siphash24(). Patch by Rolf Eike Beer.

- bpo-32911: Due to unexpected compatibility issues discovered during
  downstream beta testing, reverted :issue:`29463`. ``docstring`` field is
  removed from Module, ClassDef, FunctionDef, and AsyncFunctionDef ast nodes
  which was added in 3.7a1.  Docstring expression is restored as a first
  statement in their body. Based on patch by Inada Naoki.

- bpo-21983: Fix a crash in `ctypes.cast()` in case the type argument is a
  ctypes structured data type. Patch by Eryk Sun and Oren Milman.

Library
-------

- bpo-32751: When cancelling the task due to a timeout,
  :meth:`asyncio.wait_for` will now wait until the cancellation is complete.

- bpo-32684: Fix gather to propagate cancellation of itself even with
  return_exceptions.

- bpo-33654: Support protocol type switching in SSLTransport.set_protocol().

- bpo-33674: Pause the transport as early as possible to further reduce the
  risk of data_received() being called before connection_made().

- bpo-33674: Fix a race condition in SSLProtocol.connection_made() of
  asyncio.sslproto: start immediately the handshake instead of using
  call_soon(). Previously, data_received() could be called before the
  handshake started, causing the handshake to hang or fail.

- bpo-31647: Fixed bug where calling write_eof() on a
  _SelectorSocketTransport after it's already closed raises AttributeError.

- bpo-32610: Make asyncio.all_tasks() return only pending tasks.

- bpo-32410: Avoid blocking on file IO in sendfile fallback code

- bpo-33469: Fix RuntimeError after closing loop that used run_in_executor

- bpo-33672: Fix Task.__repr__ crash with Cython's bogus coroutines

- bpo-33654: Fix transport.set_protocol() to support switching between
  asyncio.Protocol and asyncio.BufferedProtocol.  Fix loop.start_tls() to
  work with asyncio.BufferedProtocols.

- bpo-33652: Pickles of type variables and subscripted generics are now
  future-proof and compatible with older Python versions.

- bpo-32493: Fixed :func:`uuid.uuid1` on FreeBSD.

- bpo-33618: Finalize and document preliminary and experimental TLS 1.3
  support with OpenSSL 1.1.1

- bpo-33623: Fix possible SIGSGV when asyncio.Future is created in __del__

- bpo-30877: Fixed a bug in the Python implementation of the JSON decoder
  that prevented the cache of parsed strings from clearing after finishing
  the decoding. Based on patch by c-fos.

- bpo-33570: Change TLS 1.3 cipher suite settings for compatibility with
  OpenSSL 1.1.1-pre6 and newer. OpenSSL 1.1.1 will have TLS 1.3 ciphers
  enabled by default.

- bpo-28556: Do not simplify arguments to `typing.Union`. Now
  `Union[Manager, Employee]` is not simplified to `Employee` at runtime.
  Such simplification previously caused several bugs and limited
  possibilities for introspection.

- bpo-33540: Add a new ``block_on_close`` class attribute to
  ``ForkingMixIn`` and ``ThreadingMixIn`` classes of :mod:`socketserver`.

- bpo-33548: tempfile._candidate_tempdir_list should consider common TEMP
  locations

- bpo-33109: argparse subparsers are once again not required by default,
  reverting the change in behavior introduced by bpo-26510 in 3.7.0a2.

- bpo-33536: dataclasses.make_dataclass now checks for invalid field names
  and duplicate fields. Also, added a check for invalid field
  specifications.

- bpo-33542: Prevent ``uuid.get_node`` from using a DUID instead of a MAC on
  Windows. Patch by Zvi Effron

- bpo-26819: Fix race condition with `ReadTransport.resume_reading` in
  Windows proactor event loop.

- Fix failure in `typing.get_type_hints()` when ClassVar was provided as a
  string forward reference.

- bpo-33505: Optimize asyncio.ensure_future() by reordering if checks: 1.17x
  faster.

- bpo-33497: Add errors param to cgi.parse_multipart and make an encoding in
  FieldStorage use the given errors (needed for Twisted).  Patch by Amber
  Brown.

- bpo-33495: Change dataclasses.Fields repr to use the repr of each of its
  members, instead of str.  This makes it more clear what each field
  actually represents.  This is especially true for the 'type' member.

- bpo-33453: Fix dataclasses to work if using literal string type
  annotations or if using PEP 563 "Postponed Evaluation of Annotations".
  Only specific string prefixes are detected for both ClassVar ("ClassVar"
  and "typing.ClassVar") and InitVar ("InitVar" and "dataclasses.InitVar").

- bpo-28556: Minor fixes in typing module: add annotations to
  ``NamedTuple.__new__``, pass ``*args`` and ``**kwds`` in
  ``Generic.__new__``.  Original PRs by Paulius Šarka and Chad Dombrova.

- bpo-20087: Updated alias mapping with glibc 2.27 supported locales.

- bpo-33422: Fix trailing quotation marks getting deleted when looking up
  byte/string literals on pydoc. Patch by Andrés Delfino.

- bpo-28167: The function ``platform.linux_distribution`` and
  ``platform.dist`` now trigger a ``DeprecationWarning`` and have been
  marked for removal in Python 3.8

- bpo-33197: Update error message when constructing invalid
  inspect.Parameters Patch by Dong-hee Na.

- bpo-33263: Fix FD leak in `_SelectorSocketTransport`  Patch by Vlad
  Starostin.

- bpo-32861: The urllib.robotparser's ``__str__`` representation now
  includes wildcard entries and the "Crawl-delay" and "Request-rate" fields.
  Patch by Michael Lazar.

- bpo-32257: The ssl module now contains OP_NO_RENEGOTIATION constant,
  available with OpenSSL 1.1.0h or 1.1.1.

- bpo-16865: Support arrays >=2GiB in :mod:`ctypes`.  Patch by Segev Finer.

Documentation
-------------

- bpo-23859: Document that `asyncio.wait()` does not cancel its futures on
  timeout.

- bpo-32436: Document :pep:`567` changes to asyncio.

- bpo-33604: Update HMAC md5 default to a DeprecationWarning, bump removal
  to 3.8.

- bpo-33503: Fix broken pypi link

- bpo-33421: Add missing documentation for ``typing.AsyncContextManager``.

Tests
-----

- bpo-33655: Ignore test_posix_fallocate failures on BSD platforms that
  might be due to running on ZFS.

- bpo-32604: Remove the _xxsubinterpreters module (meant for testing) and
  associated helpers.  This module was originally added recently in 3.7b1.

Build
-----

- bpo-33614: Ensures module definition files for the stable ABI on Windows
  are correctly regenerated.

- bpo-33522: Enable CI builds on Visual Studio Team Services at
  https://python.visualstudio.com/cpython

- bpo-33012: Add ``-Wno-cast-function-type`` for gcc 8 for silencing
  warnings about function casts like casting to PyCFunction in method
  definition lists.

macOS
-----

- bpo-13631: The .editrc file in user's home directory is now processed
  correctly during the readline initialization through editline emulation on
  macOS.

IDLE
----

- bpo-33628: IDLE: Cleanup codecontext.py and its test.

- bpo-33564: IDLE's code context now recognizes async as a block opener.

- bpo-32831: Add docstrings and tests for codecontext.


What's New in Python 3.7.0 beta 4?
==================================

*Release date: 2018-05-02*

Core and Builtins
-----------------

- bpo-33363: Raise a SyntaxError for ``async with`` and ``async for``
  statements outside of async functions.

- bpo-33128: Fix a bug that causes PathFinder to appear twice on
  sys.meta_path. Patch by Pablo Galindo Salgado.

- bpo-33312: Fixed clang ubsan (undefined behavior sanitizer) warnings in
  dictobject.c by adjusting how the internal struct _dictkeysobject shared
  keys structure is declared.

- bpo-33231: Fix potential memory leak in ``normalizestring()``.

- bpo-33205: Change dict growth function from
  ``round_up_to_power_2(used*2+hashtable_size/2)`` to
  ``round_up_to_power_2(used*3)``.  Previously, dict is shrinked only when
  ``used == 0``. Now dict has more chance to be shrinked.

- bpo-29922: Improved error messages in 'async with' when ``__aenter__()``
  or ``__aexit__()`` return non-awaitable object.

- bpo-33199: Fix ``ma_version_tag`` in dict implementation is uninitialized
  when copying from key-sharing dict.

Library
-------

- bpo-33281: Fix ctypes.util.find_library regression on macOS.

- bpo-33383: Fixed crash in the get() method of the :mod:`dbm.ndbm` database
  object when it is called with a single argument.

- bpo-33329: Fix multiprocessing regression on newer glibcs

- bpo-991266: Fix quoting of the ``Comment`` attribute of
  :class:`http.cookies.SimpleCookie`.

- bpo-33131: Upgrade bundled version of pip to 10.0.1.

- bpo-33308: Fixed a crash in the :mod:`parser` module when converting an ST
  object to a tree of tuples or lists with ``line_info=False`` and
  ``col_info=True``.

- bpo-33266: lib2to3 now recognizes ``rf'...'`` strings.

- bpo-11594: Ensure line-endings are respected when using lib2to3.

- bpo-33254: Have :func:`importlib.resources.contents` and
  :meth:`importlib.abc.ResourceReader.contents` return an :term:`iterable`
  instead of an :term:`iterator`.

- bpo-33256: Fix display of ``<module>`` call in the html produced by
  ``cgitb.html()``. Patch by Stéphane Blondon.

- bpo-33185: Fixed regression when running pydoc with the :option:`-m`
  switch. (The regression was introduced in 3.7.0b3 by the resolution of
  :issue:`33053`) This fix also changed pydoc to add ``os.getcwd()`` to
  :data:`sys.path` when necessary, rather than adding ``"."``.

- bpo-33169: Delete entries of ``None`` in :data:`sys.path_importer_cache`
  when :meth:`importlib.machinery.invalidate_caches` is called.

- bpo-33217: Deprecate looking up non-Enum objects in Enum classes and Enum
  members (will raise :exc:`TypeError` in 3.8+).

- bpo-33203: ``random.Random.choice()`` now raises ``IndexError`` for empty
  sequences consistently even when called from subclasses without a
  ``getrandbits()`` implementation.

- bpo-33224: Update difflib.mdiff() for :pep:`479`.  Convert an uncaught
  StopIteration in a generator into a return-statement.

- bpo-33209: End framing at the end of C implementation of
  :func:`pickle.Pickler.dump`.

- bpo-20104: Improved error handling and fixed a reference leak in
  :func:`os.posix_spawn()`.

- bpo-33175: In dataclasses, Field.__set_name__ now looks up the
  __set_name__ special method on the class, not the instance, of the default
  value.

- bpo-33097: Raise RuntimeError when ``executor.submit`` is called during
  interpreter shutdown.

- bpo-31908: Fix output of cover files for ``trace`` module command-line
  tool. Previously emitted cover files only when ``--missing`` option was
  used. Patch by Michael Selik.

Documentation
-------------

- bpo-33378: Add Korean language switcher for https://docs.python.org/3/

- bpo-33276: Clarify that the ``__path__`` attribute on modules cannot be
  just any value.

- bpo-33201: Modernize documentation for writing C extension types.

- bpo-33195: Deprecate ``Py_UNICODE`` usage in ``c-api/arg`` document.
  ``Py_UNICODE`` related APIs are deprecated since Python 3.3, but it is
  missed in the document.

- bpo-8243: Add a note about curses.addch and curses.addstr exception
  behavior when writing outside a window, or pad.

- bpo-32337: Update documentation related with ``dict`` order.

Tests
-----

- bpo-33358: Fix ``test_embed.test_pre_initialization_sys_options()`` when
  the interpreter is built with ``--enable-shared``.

Build
-----

- bpo-33394: Enable the verbose build for extension modules, when GNU make
  is passed macros on the command line.

- bpo-33393: Update config.guess and config.sub files.

- bpo-33377: Add new triplets for mips r6 and riscv variants (used in
  extension suffixes).

- bpo-32232: By default, modules configured in `Modules/Setup` are no longer
  built with `-DPy_BUILD_CORE`. Instead, modules that specifically need that
  preprocessor definition include it in their individual entries.

- bpo-33182: The embedding tests can once again be built with clang 6.0

Windows
-------

- bpo-33184: Update Windows installer to use OpenSSL 1.1.0h.

macOS
-----

- bpo-33184: Update macOS installer build to use OpenSSL 1.1.0h.

IDLE
----

- bpo-21474: Update word/identifier definition from ascii to unicode. In
  text and entry boxes, this affects selection by double-click, movement
  left/right by control-left/right, and deletion left/right by
  control-BACKSPACE/DEL.

- bpo-33204: IDLE: consistently color invalid string prefixes. A 'u' string
  prefix cannot be paired with either 'r' or 'f'. Consistently color as much
  of the prefix, starting at the right, as is valid. Revise and extend
  colorizer test.

Tools/Demos
-----------

- bpo-33189: :program:`pygettext.py` now recognizes only literal strings as
  docstrings and translatable strings, and rejects bytes literals and
  f-string expressions.

- bpo-31920: Fixed handling directories as arguments in the ``pygettext``
  script. Based on patch by Oleg Krasnikov.

- bpo-29673: Fix pystackv and pystack gdbinit macros.

- bpo-31583: Fix 2to3 for using with --add-suffix option but without
  --output-dir option for relative path to files in current directory.


What's New in Python 3.7.0 beta 3?
==================================

*Release date: 2018-03-29*

Security
--------

- bpo-33136: Harden ssl module against LibreSSL CVE-2018-8970.
  X509_VERIFY_PARAM_set1_host() is called with an explicit namelen. A new
  test ensures that NULL bytes are not allowed.

- bpo-33001: Minimal fix to prevent buffer overrun in os.symlink on Windows

- bpo-32981: Regexes in difflib and poplib were vulnerable to catastrophic
  backtracking. These regexes formed potential DOS vectors (REDOS). They
  have been refactored. This resolves CVE-2018-1060 and CVE-2018-1061. Patch
  by Jamie Davis.

Core and Builtins
-----------------

- bpo-33053: When using the -m switch, sys.path[0] is now explicitly
  expanded as the *starting* working directory, rather than being left as
  the empty path (which allows imports from the current working directory at
  the time of the import)

- bpo-33018: Improve consistency of errors raised by ``issubclass()`` when
  called with a non-class and an abstract base class as the first and second
  arguments, respectively. Patch by Josh Bronson.

- bpo-33041: Fixed jumping when the function contains an ``async for`` loop.

- bpo-33026: Fixed jumping out of "with" block by setting f_lineno.

- bpo-33005: Fix a crash on fork when using a custom memory allocator (ex:
  using PYTHONMALLOC env var). _PyGILState_Reinit() and
  _PyInterpreterState_Enable() now use the default RAW memory allocator to
  allocate a new interpreters mutex on fork.

- bpo-17288: Prevent jumps from 'return' and 'exception' trace events.

- bpo-32836: Don't use temporary variables in cases of list/dict/set
  comprehensions

Library
-------

- bpo-33141: Have Field objects pass through __set_name__ to their default
  values, if they have their own __set_name__.

- bpo-33096: Allow ttk.Treeview.insert to insert iid that has a false
  boolean value. Note iid=0 and iid=False would be same. Patch by Garvit
  Khatri.

- bpo-32873: Treat type variables and special typing forms as immutable by
  copy and pickle.  This fixes several minor issues and inconsistencies, and
  improves backwards compatibility with Python 3.6.

- bpo-33134: When computing dataclass's __hash__, use the lookup table to
  contain the function which returns the __hash__ value.  This is an
  improvement over looking up a string, and then testing that string to see
  what to do.

- bpo-33127: The ssl module now compiles with LibreSSL 2.7.1.

- bpo-32505: Raise TypeError if a member variable of a dataclass is of type
  Field, but doesn't have a type annotation.

- bpo-33078: Fix the failure on OSX caused by the tests relying on
  sem_getvalue

- bpo-33116: Add 'Field' to dataclasses.__all__.

- bpo-32896: Fix an error where subclassing a dataclass with a field that
  uses a default_factory would generate an incorrect class.

- bpo-33100: Dataclasses: If a field has a default value that's a
  MemberDescriptorType, then it's from that field being in __slots__, not an
  actual default value.

- bpo-32953: If a non-dataclass inherits from a frozen dataclass, allow
  attributes to be added to the derived class.  Only attributes from the
  frozen dataclass cannot be assigned to.  Require all dataclasses in a
  hierarchy to be either all frozen or all non-frozen.

- bpo-33061: Add missing ``NoReturn`` to ``__all__`` in typing.py

- bpo-33078: Fix the size handling in multiprocessing.Queue when a pickling
  error occurs.

- bpo-33064: lib2to3 now properly supports trailing commas after ``*args``
  and ``**kwargs`` in function signatures.

- bpo-33056: FIX properly close leaking fds in
  concurrent.futures.ProcessPoolExecutor.

- bpo-33021: Release the GIL during fstat() calls, avoiding hang of all
  threads when calling mmap.mmap(), os.urandom(), and random.seed().  Patch
  by Nir Soffer.

- bpo-31804: Avoid failing in multiprocessing.Process if the standard
  streams are closed or None at exit.

- bpo-33037: Skip sending/receiving data after SSL transport closing.

- bpo-27683: Fix a regression in :mod:`ipaddress` that result of
  :meth:`hosts` is empty when the network is constructed by a tuple
  containing an integer mask and only 1 bit left for addresses.

- bpo-32999: Fix C implementation of ``ABC.__subclasscheck__(cls,
  subclass)`` crashed when ``subclass`` is not a type object.

- bpo-33009: Fix inspect.signature() for single-parameter partialmethods.

- bpo-32969: Expose several missing constants in zlib and fix corresponding
  documentation.

- bpo-32056: Improved exceptions raised for invalid number of channels and
  sample width when read an audio file in modules :mod:`aifc`, :mod:`wave`
  and :mod:`sunau`.

- bpo-32844: Fix wrong redirection of a low descriptor (0 or 1) to stderr in
  subprocess if another low descriptor is closed.

- bpo-32857: In :mod:`tkinter`, ``after_cancel(None)`` now raises a
  :exc:`ValueError` instead of canceling the first scheduled function.
  Patch by Cheryl Sabella.

- bpo-31639: http.server now exposes a ThreadedHTTPServer class and uses it
  when the module is run with ``-m`` to cope with web browsers pre-opening
  sockets.

- bpo-27645: :class:`sqlite3.Connection` now exposes a
  :class:`~sqlite3.Connection.backup` method, if the underlying SQLite
  library is at version 3.6.11 or higher.  Patch by Lele Gaifax.

Documentation
-------------

- bpo-33126: Document PyBuffer_ToContiguous().

- bpo-27212: Modify documentation for the :func:`islice` recipe to consume
  initial values up to the start index.

- bpo-28247: Update :mod:`zipapp` documentation to describe how to make
  standalone applications.

- bpo-18802: Documentation changes for ipaddress.  Patch by Jon Foster and
  Berker Peksag.

- bpo-27428: Update documentation to clarify that ``WindowsRegistryFinder``
  implements ``MetaPathFinder``. (Patch by Himanshu Lakhara)

Tests
-----

- bpo-32872: Avoid regrtest compatibility issue with namespace packages.

- bpo-32517: Fix failing ``test_asyncio`` on macOS 10.12.2+ due to transport
  of ``KqueueSelector`` loop was not being closed.

- bpo-19417: Add test_bdb.py.

Build
-----

- bpo-33163: Upgrade pip to 9.0.3 and setuptools to v39.0.1.

Windows
-------

- bpo-33016: Fix potential use of uninitialized memory in
  nt._getfinalpathname

- bpo-32903: Fix a memory leak in os.chdir() on Windows if the current
  directory is set to a UNC path.

macOS
-----

- bpo-32726: Build and link with private copy of Tcl/Tk 8.6 for the macOS
  10.6+ installer. The 10.9+ installer variant already does this.  This
  means that the Python 3.7 provided by the python.org macOS installers no
  longer need or use any external versions of Tcl/Tk, either system-provided
  or user-installed, such as ActiveTcl.

IDLE
----

- bpo-32984: Set ``__file__`` while running a startup file.  Like Python,
  IDLE optionally runs one startup file in the Shell window before
  presenting the first interactive input prompt.  For IDLE, ``-s`` runs a
  file named in environmental variable  :envvar:`IDLESTARTUP` or
  :envvar:`PYTHONSTARTUP`; ``-r file`` runs ``file``.  Python sets
  ``__file__`` to the startup file name before running the file and unsets
  it before the first prompt.  IDLE now does the same when run normally,
  without the ``-n`` option.

- bpo-32940: Simplify and rename StringTranslatePseudoMapping in pyparse.

Tools/Demos
-----------

- bpo-32885: Add an ``-n`` flag for ``Tools/scripts/pathfix.py`` to disable
  automatic backup creation (files with ``~`` suffix).

C API
-----

- bpo-33042: Embedding applications may once again call
  PySys_ResetWarnOptions, PySys_AddWarnOption, and PySys_AddXOption prior to
  calling Py_Initialize.

- bpo-32374: Document that m_traverse for multi-phase initialized modules
  can be called with m_state=NULL, and add a sanity check


What's New in Python 3.7.0 beta 2?
==================================

*Release date: 2018-02-27*

Security
--------

- bpo-28414: The ssl module now allows users to perform their own IDN
  en/decoding when using SNI.

Core and Builtins
-----------------

- bpo-32889: Update Valgrind suppression list to account for the rename of
  ``Py_ADDRESS_IN_RANG`` to ``address_in_range``.

- bpo-31356: Remove the new API added in bpo-31356 (gc.ensure_disabled()
  context manager).

- bpo-32305: For namespace packages, ensure that both ``__file__`` and
  ``__spec__.origin`` are set to None.

- bpo-32303: Make sure ``__spec__.loader`` matches ``__loader__`` for
  namespace packages.

- bpo-32711: Fix the warning messages for Python/ast_unparse.c. Patch by
  Stéphane Wirtel

- bpo-32583: Fix possible crashing in builtin Unicode decoders caused by
  write out-of-bound errors when using customized decode error handlers.

Library
-------

- bpo-32960: For dataclasses, disallow inheriting frozen from non-frozen
  classes, and also disallow inheriting non-frozen from frozen classes. This
  restriction will be relaxed at a future date.

- bpo-32713: Fixed tarfile.itn handling of out-of-bounds float values. Patch
  by Joffrey Fuhrer.

- bpo-32951: Direct instantiation of SSLSocket and SSLObject objects is now
  prohibited. The constructors were never documented, tested, or designed as
  public constructors. Users were suppose to use ssl.wrap_socket() or
  SSLContext.

- bpo-32929: Remove the tri-state parameter "hash", and add the boolean
  "unsafe_hash". If unsafe_hash is True, add a __hash__ function, but if a
  __hash__ exists, raise TypeError.  If unsafe_hash is False, add a __hash__
  based on the values of eq= and frozen=.  The unsafe_hash=False behavior is
  the same as the old hash=None behavior.  unsafe_hash=False is the default,
  just as hash=None used to be.

- bpo-32947: Add OP_ENABLE_MIDDLEBOX_COMPAT and test workaround for TLSv1.3
  for future compatibility with OpenSSL 1.1.1.

- bpo-30622: The ssl module now detects missing NPN support in LibreSSL.

- bpo-32922: dbm.open() now encodes filename with the filesystem encoding
  rather than default encoding.

- bpo-32859: In ``os.dup2``, don't check every call whether the ``dup3``
  syscall exists or not.

- bpo-32556: nt._getfinalpathname, nt._getvolumepathname and
  nt._getdiskusage now correctly convert from bytes.

- bpo-25988: Emit a :exc:`DeprecationWarning` when using or importing an ABC
  directly from :mod:`collections` rather than from :mod:`collections.abc`.

- bpo-21060: Rewrite confusing message from setup.py upload from "No dist
  file created in earlier command" to the more helpful "Must create and
  upload files in one command".

- bpo-32852: Make sure sys.argv remains as a list when running trace.

- bpo-31333: ``_abc`` module is added.  It is a speedup module with C
  implementations for various functions and methods in ``abc``.  Creating an
  ABC subclass and calling ``isinstance`` or ``issubclass`` with an ABC
  subclass are up to 1.5x faster. In addition, this makes Python start-up up
  to 10% faster. Note that the new implementation hides internal registry
  and caches, previously accessible via private attributes
  ``_abc_registry``, ``_abc_cache``, and ``_abc_negative_cache``.  There are
  three debugging helper methods that can be used instead
  ``_dump_registry``, ``_abc_registry_clear``, and ``_abc_caches_clear``.

- bpo-32841: Fixed `asyncio.Condition` issue which silently ignored
  cancellation after notifying and cancelling a conditional lock. Patch by
  Bar Harel.

- bpo-32819: ssl.match_hostname() has been simplified and no longer depends
  on re and ipaddress module for wildcard and IP addresses. Error reporting
  for invalid wildcards has been improved.

- bpo-32394: socket: Remove
  TCP_FASTOPEN,TCP_KEEPCNT,TCP_KEEPIDLE,TCP_KEEPINTVL flags on older version
  Windows during run-time.

- bpo-31787: Fixed refleaks of ``__init__()`` methods in various modules.
  (Contributed by Oren Milman)

- bpo-30157: Fixed guessing quote and delimiter in csv.Sniffer.sniff() when
  only the last field is quoted.  Patch by Jake Davis.

- bpo-32792: collections.ChainMap() preserves the order of the underlying
  mappings.

- bpo-32775: :func:`fnmatch.translate()` no longer produces patterns which
  contain set operations. Sets starting with '[' or containing '--', '&&',
  '~~' or '||' will be interpreted differently in regular expressions in
  future versions. Currently they emit warnings. fnmatch.translate() now
  avoids producing patterns containing such sets by accident.

- bpo-32622: Implement native fast sendfile for Windows proactor event loop.

- bpo-32777: Fix a rare but potential pre-exec child process deadlock in
  subprocess on POSIX systems when marking file descriptors inheritable on
  exec in the child process.  This bug appears to have been introduced in
  3.4.

- bpo-32647: The ctypes module used to depend on indirect linking for
  dlopen. The shared extension is now explicitly linked against libdl on
  platforms with dl.

- bpo-32741: Implement ``asyncio.TimerHandle.when()`` method.

- bpo-32691: Use mod_spec.parent when running modules with pdb

- bpo-32734: Fixed ``asyncio.Lock()`` safety issue which allowed acquiring
  and locking the same lock multiple times, without it being free. Patch by
  Bar Harel.

- bpo-32727: Do not include name field in SMTP envelope from address. Patch
  by Stéphane Wirtel

- bpo-31453: Add TLSVersion constants and SSLContext.maximum_version /
  minimum_version attributes. The new API wraps OpenSSL 1.1
  https://www.openssl.org/docs/man1.1.0/ssl/SSL_CTX_set_min_proto_version.html
  feature.

- bpo-24334: Internal implementation details of ssl module were cleaned up.
  The SSLSocket has one less layer of indirection. Owner and session
  information are now handled by the SSLSocket and SSLObject constructor.
  Channel binding implementation has been simplified.

- bpo-31848: Fix the error handling in Aifc_read.initfp() when the SSND
  chunk is not found. Patch by Zackery Spytz.

- bpo-32585: Add Ttk spinbox widget to :mod:`tkinter.ttk`.  Patch by Alan D
  Moore.

- bpo-32221: Various functions returning tuple containing IPv6 addresses now
  omit ``%scope`` part since the same information is already encoded in
  *scopeid* tuple item. Especially this speeds up :func:`socket.recvfrom`
  when it receives multicast packet since useless resolving of network
  interface name is omitted.

- bpo-30693: The TarFile class now recurses directories in a reproducible
  way.

- bpo-30693: The ZipFile class now recurses directories in a reproducible
  way.

Documentation
-------------

- bpo-28124: The ssl module function ssl.wrap_socket() has been
  de-emphasized and deprecated in favor of the more secure and efficient
  SSLContext.wrap_socket() method.

- bpo-17232: Clarify docs for -O and -OO.  Patch by Terry Reedy.

- bpo-32436: Add documentation for the contextvars module (PEP 567).

- bpo-32800: Update link to w3c doc for xml default namespaces.

- bpo-11015: Update :mod:`test.support` documentation.

- bpo-8722: Document :meth:`__getattr__` behavior when property :meth:`get`
  method raises :exc:`AttributeError`.

- bpo-32614: Modify RE examples in documentation to use raw strings to
  prevent :exc:`DeprecationWarning` and add text to REGEX HOWTO to highlight
  the deprecation.

- bpo-31972: Improve docstrings for `pathlib.PurePath` subclasses.

Tests
-----

- bpo-31809: Add tests to verify connection with secp ECDH curves.

Build
-----

- bpo-32898: Fix the python debug build when using COUNT_ALLOCS.

Windows
-------

- bpo-32901: Update Tcl and Tk versions to 8.6.8

- bpo-31966: Fixed WindowsConsoleIO.write() for writing empty data.

- bpo-32409: Ensures activate.bat can handle Unicode contents.

- bpo-32457: Improves handling of denormalized executable path when
  launching Python.

- bpo-32370: Use the correct encoding for ipconfig output in the uuid
  module. Patch by Segev Finer.

- bpo-29248: Fix :func:`os.readlink` on Windows, which was mistakenly
  treating the ``PrintNameOffset`` field of the reparse data buffer as a
  number of characters instead of bytes. Patch by Craig Holmquist and SSE4.

macOS
-----

- bpo-32901: Update macOS 10.9+ installer to Tcl/Tk 8.6.8.

IDLE
----

- bpo-32916: Change ``str`` to ``code`` in pyparse.

- bpo-32905: Remove unused code in pyparse module.

- bpo-32874: Add tests for pyparse.

- bpo-32837: Using the system and place-dependent default encoding for
  open() is a bad idea for IDLE's system and location-independent files.

- bpo-32826: Add "encoding=utf-8" to open() in IDLE's test_help_about. GUI
  test test_file_buttons() only looks at initial ascii-only lines, but
  failed on systems where open() defaults to 'ascii' because readline()
  internally reads and decodes far enough ahead to encounter a non-ascii
  character in CREDITS.txt.

- bpo-32765: Update configdialog General tab docstring to add new widgets to
  the widget list.

Tools/Demos
-----------

- bpo-32222: Fix pygettext not extracting docstrings for functions with type
  annotated arguments. Patch by Toby Harradine.


What's New in Python 3.7.0 beta 1?
==================================

*Release date: 2018-01-30*

Core and Builtins
-----------------

- bpo-32703: Fix coroutine's ResourceWarning when there's an active error
  set when it's being finalized.

- bpo-32650: Pdb and other debuggers dependent on bdb.py will correctly step
  over (next command) native coroutines. Patch by Pablo Galindo.

- bpo-28685: Optimize list.sort() and sorted() by using type specialized
  comparisons when possible.

- bpo-32685: Improve suggestion when the Python 2 form of print statement is
  either present on the same line as the header of a compound statement or
  else terminated by a semi-colon instead of a newline. Patch by Nitish
  Chandra.

- bpo-32697: Python now explicitly preserves the definition order of
  keyword-only parameters.  It's always preserved their order, but this
  behavior was never guaranteed before; this behavior is now guaranteed and
  tested.

- bpo-32690: The locals() dictionary now displays in the lexical order that
  variables were defined.  Previously, the order was reversed.

- bpo-32677: Add ``.isascii()`` method to ``str``, ``bytes`` and
  ``bytearray``. It can be used to test that string contains only ASCII
  characters.

- bpo-32670: Enforce :pep:`479` for all code. This means that manually
  raising a StopIteration exception from a generator is prohibited for all
  code, regardless of whether 'from __future__ import generator_stop' was
  used or not.

- bpo-32591: Added built-in support for tracking the origin of coroutine
  objects; see sys.set_coroutine_origin_tracking_depth and
  CoroutineType.cr_origin. This replaces the asyncio debug mode's use of
  coroutine wrapping for native coroutine objects.

- bpo-31368: Expose preadv and pwritev system calls in the os module. Patch
  by Pablo Galindo

- bpo-32544: ``hasattr(obj, name)`` and ``getattr(obj, name, default)`` are
  about 4 times faster than before when ``name`` is not found and ``obj``
  doesn't override ``__getattr__`` or ``__getattribute__``.

- bpo-26163: Improved frozenset() hash to create more distinct hash values
  when faced with datasets containing many similar values.

- bpo-32550: Remove the STORE_ANNOTATION bytecode.

- bpo-20104: Expose posix_spawn as a low level API in the os module.
  (removed before 3.7.0rc1)

- bpo-24340: Fixed estimation of the code stack size.

- bpo-32436: Implement :pep:`567` Context Variables.

- bpo-18533: ``repr()`` on a dict containing its own ``values()`` or
  ``items()`` no longer raises ``RecursionError``; OrderedDict similarly.
  Instead, use ``...``, as for other recursive structures.  Patch by Ben
  North.

- bpo-20891: Py_Initialize() now creates the GIL. The GIL is no longer
  created "on demand" to fix a race condition when PyGILState_Ensure() is
  called in a non-Python thread.

- bpo-32028: Leading whitespace is now correctly ignored when generating
  suggestions for converting Py2 print statements to Py3 builtin print
  function calls. Patch by Sanyam Khurana.

- bpo-31179: Make dict.copy() up to 5.5 times faster.

- bpo-31113: Get rid of recursion in the compiler for normal control flow.

Library
-------

- bpo-25988: Deprecate exposing the contents of collections.abc in the
  regular collections module.

- bpo-31429: The default cipher suite selection of the ssl module now uses a
  blacklist approach rather than a hard-coded whitelist. Python no longer
  re-enables ciphers that have been blocked by OpenSSL security update.
  Default cipher suite selection can be configured on compile time.

- bpo-30306: contextlib.contextmanager now releases the arguments passed to
  the underlying generator as soon as the context manager is entered.
  Previously it would keep them alive for as long as the context manager was
  alive, even when not being used as a function decorator. Patch by Martin
  Teichmann.

- bpo-21417: Added support for setting the compression level for
  zipfile.ZipFile.

- bpo-32251: Implement asyncio.BufferedProtocol (provisional API).

- bpo-32513: In dataclasses, allow easier overriding of dunder methods
  without specifying decorator parameters.

- bpo-32660: :mod:`termios` makes available ``FIONREAD``, ``FIONCLEX``,
  ``FIOCLEX``, ``FIOASYNC`` and ``FIONBIO`` also under Solaris/derivatives.

- bpo-27931: Fix email address header parsing error when the username is an
  empty quoted string. Patch by Xiang Zhang.

- bpo-32659: Under Solaris and derivatives, :class:`os.stat_result` provides
  a st_fstype attribute.

- bpo-32662: Implement Server.start_serving(), Server.serve_forever(), and
  Server.is_serving() methods.  Add 'start_serving' keyword parameter to
  loop.create_server() and loop.create_unix_server().

- bpo-32391: Implement :meth:`asyncio.StreamWriter.wait_closed` and
  :meth:`asyncio.StreamWriter.is_closing` methods

- bpo-32643: Make Task._step, Task._wakeup and Future._schedule_callbacks
  methods private.

- bpo-32630: Refactor decimal module to use contextvars to store decimal
  context.

- bpo-32622: Add :meth:`asyncio.AbstractEventLoop.sendfile` method.

- bpo-32304: distutils' upload command no longer corrupts tar files ending
  with a CR byte, and no longer tries to convert CR to CRLF in any of the
  upload text fields.

- bpo-32502: uuid.uuid1 no longer raises an exception if a 64-bit hardware
  address is encountered.

- bpo-32596: ``concurrent.futures`` imports ``ThreadPoolExecutor`` and
  ``ProcessPoolExecutor`` lazily (using :pep:`562`). It makes ``import
  asyncio`` about 15% faster because asyncio uses only
  ``ThreadPoolExecutor`` by default.

- bpo-31801: Add ``_ignore_`` to ``Enum`` so temporary variables can be used
  during class construction without being turned into members.

- bpo-32576: Use queue.SimpleQueue() in places where it can be invoked from
  a weakref callback.

- bpo-32574: Fix memory leak in asyncio.Queue, when the queue has limited
  size and it is full, the cancelation of queue.put() can cause a memory
  leak. Patch by: José Melero.

- bpo-32521: The nis module is now compatible with new libnsl and headers
  location.

- bpo-32467: collections.abc.ValuesView now inherits from
  collections.abc.Collection.

- bpo-32473: Improve ABCMeta._dump_registry() output readability

- bpo-32102: New argument ``capture_output`` for subprocess.run

- bpo-32521: glibc has removed Sun RPC. Use replacement libtirpc headers and
  library in nis module.

- bpo-32493: UUID module fixes build for FreeBSD/OpenBSD

- bpo-32503: Pickling with protocol 4 no longer creates too small frames.

- bpo-29237: Create enum for pstats sorting options

- bpo-32454: Add close(fd) function to the socket module.

- bpo-25942: The subprocess module is now more graceful when handling a
  Ctrl-C KeyboardInterrupt during subprocess.call, subprocess.run, or a
  Popen context manager.  It now waits a short amount of time for the child
  (presumed to have also gotten the SIGINT) to exit, before continuing the
  KeyboardInterrupt exception handling.  This still includes a SIGKILL in
  the call() and run() APIs, but at least the child had a chance first.

- bpo-32433: The hmac module now has hmac.digest(), which provides an
  optimized HMAC digest.

- bpo-28134: Sockets now auto-detect family, type and protocol from file
  descriptor by default.

- bpo-32404: Fix bug where :meth:`datetime.datetime.fromtimestamp` did not
  call __new__ in :class:`datetime.datetime` subclasses.

- bpo-32403: Improved speed of :class:`datetime.date` and
  :class:`datetime.datetime` alternate constructors.

- bpo-32228: Ensure that ``truncate()`` preserves the file position (as
  reported by ``tell()``) after writes longer than the buffer size.

- bpo-32410: Implement ``loop.sock_sendfile`` for asyncio event loop.

- bpo-22908: Added seek and tell to the ZipExtFile class. This only works if
  the file object used to open the zipfile is seekable.

- bpo-32373: Add socket.getblocking() method.

- bpo-32248: Add :mod:`importlib.resources` and
  :class:`importlib.abc.ResourceReader` as the unified API for reading
  resources contained within packages.  Loaders wishing to support resource
  reading must implement the :meth:`get_resource_reader()` method.
  File-based and zipimport-based loaders both implement these APIs.
  :class:`importlib.abc.ResourceLoader` is deprecated in favor of these new
  APIs.

- bpo-32320: collections.namedtuple() now supports default values.

- bpo-29302: Add contextlib.AsyncExitStack. Patch by Alexander Mohr and Ilya
  Kulakov.

- bpo-31961: *Removed in Python 3.7.0b2.* The *args* argument of
  subprocess.Popen can now be a :term:`path-like object`. If *args* is given
  as a sequence, it's first element can now be a :term:`path-like object` as
  well.

- bpo-31900: The :func:`locale.localeconv` function now sets temporarily the
  ``LC_CTYPE`` locale to the ``LC_NUMERIC`` locale to decode
  ``decimal_point`` and ``thousands_sep`` byte strings if they are non-ASCII
  or longer than 1 byte, and the ``LC_NUMERIC`` locale is different than the
  ``LC_CTYPE`` locale. This temporary change affects other threads. Same
  change for the :meth:`str.format` method when formatting a number
  (:class:`int`, :class:`float`, :class:`float` and subclasses) with the
  ``n`` type (ex: ``'{:n}'.format(1234)``).

- bpo-31853: Use super().method instead of socket.method in SSLSocket.  They
  were there most likely for legacy reasons.

- bpo-31399: The ssl module now uses OpenSSL's X509_VERIFY_PARAM_set1_host()
  and X509_VERIFY_PARAM_set1_ip() API to verify hostname and IP addresses.
  Subject common name fallback can be disabled with
  SSLContext.hostname_checks_common_name.

- bpo-14976: Add a queue.SimpleQueue class, an unbounded FIFO queue with a
  reentrant C implementation of put().

Documentation
-------------

- bpo-32724: Add references to some commands in the documentation of Pdb.
  Patch by Stéphane Wirtel

- bpo-32649: Complete the C API documentation, profiling and tracing part
  with the newly added per-opcode events.

- bpo-17799: Explain real behaviour of sys.settrace and sys.setprofile and
  their C-API counterparts regarding which type of events are received in
  each function. Patch by Pablo Galindo Salgado.

Tests
-----

- bpo-32721: Fix test_hashlib to not fail if the _md5 module is not built.

- bpo-28414: Add test cases for IDNA 2003 and 2008 host names. IDNA 2003
  internationalized host names are working since bpo-31399 has landed. IDNA
  2008 are still broken.

- bpo-32604: Add a new "_xxsubinterpreters" extension module that exposes
  the existing subinterpreter C-API and a new cross-interpreter data sharing
  mechanism. The module is primarily intended for more thorough testing of
  the existing subinterpreter support. Note that the _xxsubinterpreters
  module has been removed in 3.7.0rc1.

- bpo-32602: Add test certs and test for ECDSA cert and EC/RSA dual mode.

- bpo-32549: On Travis CI, Python now Compiles and uses a local copy of
  OpenSSL 1.1.0g for testing.

Build
-----

- bpo-32635: Fix segfault of the crypt module when libxcrypt is provided
  instead of libcrypt at the system.

- bpo-32598: Use autoconf to detect OpenSSL libs, headers and supported
  features. The ax_check_openssl M4 macro uses pkg-config to locate OpenSSL
  and falls back to manual search.

- bpo-32593: Drop support of FreeBSD 9 and older.

- bpo-29708: If the :envvar:`SOURCE_DATE_EPOCH` environment variable is set,
  :mod:`py_compile` will always create hash-based ``.pyc`` files.

Windows
-------

- bpo-32588: Create standalone _distutils_findvs module and add missing
  _queue module to installer.

- bpo-29911: Ensure separate Modify and Uninstall buttons are displayed.

- bpo-32507: Use app-local UCRT install rather than the proper update for
  old versions of Windows.

macOS
-----

- bpo-32726: Provide an additional, more modern macOS installer variant that
  supports macOS 10.9+ systems in 64-bit mode only.  Upgrade the supplied
  third-party libraries to OpenSSL 1.1.0g and to SQLite 3.22.0.  The 10.9+
  installer now links with and supplies its own copy of Tcl/Tk 8.6.

- bpo-28440: No longer add /Library/Python/3.x/site-packages to sys.path for
  macOS framework builds to avoid future conflicts.

C API
-----

- bpo-32681: Fix uninitialized variable 'res' in the C implementation of
  os.dup2. Patch by Stéphane Wirtel

- bpo-10381: Add C API access to the ``datetime.timezone`` constructor and
  ``datetime.timzone.UTC`` singleton.


What's New in Python 3.7.0 alpha 4?
===================================

*Release date: 2018-01-08*

Core and Builtins
-----------------

- bpo-31975: The default warning filter list now starts with a
  "default::DeprecationWarning:__main__" entry, so deprecation warnings are
  once again shown by default in single-file scripts and at the interactive
  prompt.

- bpo-32226: ``__class_getitem__`` is now an automatic class method.

- bpo-32399: Add AIX uuid library support for RFC4122 using uuid_create() in
  libc.a

- bpo-32390: Fix the compilation failure on AIX after the f_fsid field has
  been added to the object returned by os.statvfs() (issue #32143). Original
  patch by Michael Felt.

- bpo-32379: Make MRO computation faster when a class inherits from a single
  base.

- bpo-32259: The error message of a TypeError raised when unpack
  non-iterable is now more specific.

- bpo-27169: The ``__debug__`` constant is now optimized out at compile
  time. This fixes also bpo-22091.

- bpo-32329: The :option:`-R` option now turns on hash randomization when
  the :envvar:`PYTHONHASHSEED` environment variable is set to ``0``.
  Previously, the option was ignored. Moreover,
  ``sys.flags.hash_randomization`` is now properly set to 0 when hash
  randomization is turned off by ``PYTHONHASHSEED=0``.

- bpo-30416: The optimizer is now protected from spending much time doing
  complex calculations and consuming much memory for creating large
  constants in constant folding. Increased limits for constants that can be
  produced in constant folding.

- bpo-32282: Fix an unnecessary ifdef in the include of VersionHelpers.h in
  socketmodule on Windows.

- bpo-30579: Implement TracebackType.__new__ to allow Python-level creation
  of traceback objects, and make TracebackType.tb_next mutable.

- bpo-32260: Don't byte swap the input keys to the SipHash algorithm on
  big-endian platforms. This should ensure siphash gives consistent results
  across platforms.

- bpo-31506: Improve the error message logic for object.__new__ and
  object.__init__. Patch by Sanyam Khurana.

- bpo-20361: ``-b`` and ``-bb`` now inject ``'default::BytesWarning'`` and
  ``error::BytesWarning`` entries into ``sys.warnoptions``, ensuring that
  they take precedence over any other warning filters configured via the
  ``-W`` option or the ``PYTHONWARNINGS`` environment variable.

- bpo-32230: `-X dev` now injects a ``'default'`` entry into
  sys.warnoptions, ensuring that it behaves identically to actually passing
  ``-Wdefault`` at the command line.

- bpo-29240: Add a new UTF-8 mode: implementation of the :pep:`540`.

- bpo-32226: :pep:`560`: Add support for ``__mro_entries__`` and
  ``__class_getitem__``. Implemented by Ivan Levkivskyi.

- bpo-32225: :pep:`562`: Add support for module ``__getattr__`` and
  ``__dir__``. Implemented by Ivan Levkivskyi.

- bpo-31901: The `atexit` module now has its callback stored per
  interpreter.

- bpo-31650: Implement :pep:`552` (Deterministic pycs). Python now supports
  invalidating bytecode cache files bashed on a source content hash rather
  than source last-modified time.

- bpo-29469: Move constant folding from bytecode layer to AST layer.
  Original patch by Eugene Toder.

Library
-------

- bpo-32506: Now that dict is defined as keeping insertion order, drop
  OrderedDict and just use plain dict.

- bpo-32279: Add params to dataclasses.make_dataclasses(): init, repr, eq,
  order, hash, and frozen.  Pass them through to dataclass().

- bpo-32278: Make type information optional on dataclasses.make_dataclass().
  If omitted, the string 'typing.Any' is used.

- bpo-32499: Add dataclasses.is_dataclass(obj), which returns True if obj is
  a dataclass or an instance of one.

- bpo-32468: Improve frame repr() to mention filename, code name and current
  line number.

- bpo-23749: asyncio: Implement loop.start_tls()

- bpo-32441: Return the new file descriptor (i.e., the second argument) from
  ``os.dup2``. Previously, ``None`` was always returned.

- bpo-32422: ``functools.lru_cache`` uses less memory (3 words for each
  cached key) and takes about 1/3 time for cyclic GC.

- bpo-31721: Prevent Python crash from happening when Future._log_traceback
  is set to True manually.  Now it can only be set to False, or a ValueError
  is raised.

- bpo-32415: asyncio: Add Task.get_loop() and Future.get_loop()

- bpo-26133: Don't unsubscribe signals in asyncio UNIX event loop on
  interpreter shutdown.

- bpo-32363: Make asyncio.Task.set_exception() and set_result() raise
  NotImplementedError. Task._step() and Future.__await__() raise proper
  exceptions when they are in an invalid state, instead of raising an
  AssertionError.

- bpo-32357: Optimize asyncio.iscoroutine() and loop.create_task() for
  non-native coroutines (e.g. async/await compiled with Cython).
  'loop.create_task(python_coroutine)' used to be 20% faster than
  'loop.create_task(cython_coroutine)'.  Now, the latter is as fast.

- bpo-32356: asyncio.transport.resume_reading() and pause_reading() are now
  idempotent. New transport.is_reading() method is added.

- bpo-32355: Optimize asyncio.gather(); now up to 15% faster.

- bpo-32351: Use fastpath in asyncio.sleep if delay<0 (2x boost)

- bpo-32348: Optimize asyncio.Future schedule/add/remove callback.  The
  optimization shows 3-6% performance improvements of async/await code.

- bpo-32331: Fix socket.settimeout() and socket.setblocking() to keep
  socket.type as is. Fix socket.socket() constructor to reset any bit flags
  applied to socket's type.  This change only affects OSes that have
  SOCK_NONBLOCK and/or SOCK_CLOEXEC.

- bpo-32248: Add :class:`importlib.abc.ResourceReader` as an ABC for loaders
  to provide a unified API for reading resources contained within packages.
  Also add :mod:`importlib.resources` as the port of
  ``importlib_resources``.

- bpo-32311: Implement asyncio.create_task(coro) shortcut

- bpo-32327: Convert asyncio functions that were documented as coroutines to
  coroutines. Affected functions: loop.sock_sendall, loop.sock_recv,
  loop.sock_accept, loop.getaddrinfo, loop.getnameinfo.

- bpo-32323: :func:`urllib.parse.urlsplit()` does not convert zone-id
  (scope) to lower case for scoped IPv6 addresses in hostnames now.

- bpo-32302: Fix bdist_wininst of distutils for CRT v142: it binary
  compatible with CRT v140.

- bpo-29711: Fix ``stop_serving`` in asyncio proactor loop kill all
  listening servers

- bpo-32308: :func:`re.sub()` now replaces empty matches adjacent to a
  previous non-empty match.

- bpo-29970: Abort asyncio SSLProtocol connection if handshake not complete
  within 10s

- bpo-32314: Implement asyncio.run().

- bpo-17852: Revert incorrect fix based on misunderstanding of
  _Py_PyAtExit() semantics.

- bpo-32296: Implement asyncio._get_running_loop() and get_event_loop() in
  C. This makes them 4x faster.

- bpo-32250: Implement ``asyncio.current_task()`` and
  ``asyncio.all_tasks()``. Add helpers intended to be used by alternative
  task implementations: ``asyncio._register_task``, ``asyncio._enter_task``,
  ``asyncio._leave_task`` and ``asyncio._unregister_task``. Deprecate
  ``asyncio.Task.current_task()`` and ``asyncio.Task.all_tasks()``.

- bpo-32255: A single empty field is now always quoted when written into a
  CSV file. This allows to distinguish an empty row from a row consisting of
  a single empty field. Patch by Licht Takeuchi.

- bpo-32277: Raise ``NotImplementedError`` instead of ``SystemError`` on
  platforms where ``chmod(..., follow_symlinks=False)`` is not supported.
  Patch by Anthony Sottile.

- bpo-30050: New argument warn_on_full_buffer to signal.set_wakeup_fd lets
  you control whether Python prints a warning on stderr when the wakeup fd
  buffer overflows.

- bpo-29137: The ``fpectl`` library has been removed. It was never enabled
  by default, never worked correctly on x86-64, and it changed the Python
  ABI in ways that caused unexpected breakage of C extensions.

- bpo-32273: Move asyncio.test_utils to test.test_asyncio.

- bpo-32272: Remove asyncio.async() function.

- bpo-32269: Add asyncio.get_running_loop() function.

- bpo-32265: All class and static methods of builtin types now are correctly
  classified by inspect.classify_class_attrs() and grouped in pydoc ouput.
  Added types.ClassMethodDescriptorType for unbound class methods of builtin
  types.

- bpo-32253: Deprecate ``yield from lock``, ``await lock``, ``with (yield
  from lock)`` and ``with await lock`` for asyncio synchronization
  primitives.

- bpo-22589: Changed MIME type of .bmp from 'image/x-ms-bmp' to 'image/bmp'

- bpo-32193: Convert asyncio to use *async/await* syntax. Old styled ``yield
  from`` is still supported too.

- bpo-32206: Add support to run modules with pdb

- bpo-32227: ``functools.singledispatch`` now supports registering
  implementations using type annotations.

- bpo-15873: Added new alternate constructors
  :meth:`datetime.datetime.fromisoformat`,
  :meth:`datetime.time.fromisoformat` and
  :meth:`datetime.date.fromisoformat` as the inverse operation of each
  classes's respective ``isoformat`` methods.

- bpo-32199: The getnode() ip getter now uses 'ip link' instead of 'ip link
  list'.

- bpo-32143: os.statvfs() includes the f_fsid field from statvfs(2)

- bpo-26439: Fix ctypes.util.find_library() for AIX by implementing
  ctypes._aix.find_library() Patch by: Michael Felt

- bpo-31993: The pickler now uses less memory when serializing large bytes
  and str objects into a file.  Pickles created with protocol 4 will require
  less memory for unpickling large bytes and str objects.

- bpo-27456: Ensure TCP_NODELAY is set on Linux. Tests by Victor Stinner.

- bpo-31778: ast.literal_eval() is now more strict. Addition and subtraction
  of arbitrary numbers no longer allowed.

- bpo-31802: Importing native path module (``posixpath``, ``ntpath``) now
  works even if the ``os`` module still is not imported.

- bpo-30241: Add contextlib.AbstractAsyncContextManager. Patch by Jelle
  Zijlstra.

- bpo-31699: Fix deadlocks in
  :class:`concurrent.futures.ProcessPoolExecutor` when task arguments or
  results cause pickling or unpickling errors. This should make sure that
  calls to the :class:`ProcessPoolExecutor` API always eventually return.

- bpo-15216: ``TextIOWrapper.reconfigure()`` supports changing *encoding*,
  *errors*, and *newline*.

Documentation
-------------

- bpo-32418: Add get_loop() method to Server and AbstractServer classes.

Tests
-----

- bpo-32252: Fix faulthandler_suppress_crash_report() used to prevent core
  dump files when testing crashes. getrlimit() returns zero on success.

- bpo-32002: Adjust C locale coercion testing for the empty locale and POSIX
  locale cases to more readily adjust to platform dependent behaviour.

Windows
-------

- bpo-19764: Implement support for `subprocess.Popen(close_fds=True)` on
  Windows. Patch by Segev Finer.

Tools/Demos
-----------

- bpo-24960: 2to3 and lib2to3 can now read pickled grammar files using
  pkgutil.get_data() rather than probing the filesystem. This lets 2to3 and
  lib2to3 work when run from a zipfile.

C API
-----

- bpo-32030: Py_Initialize() doesn't reset the memory allocators to default
  if the ``PYTHONMALLOC`` environment variable is not set.

- bpo-29084: Undocumented C API for OrderedDict has been excluded from the
  limited C API. It was added by mistake and actually never worked in the
  limited C API.

- bpo-32264: Moved the pygetopt.h header into internal/, since it has no
  public APIs.

- bpo-32241: :c:func:`Py_SetProgramName` and :c:func:`Py_SetPythonHome` now
  take the ``const wchar *`` arguments instead of ``wchar *``.


What's New in Python 3.7.0 alpha 3?
===================================

*Release date: 2017-12-05*

Core and Builtins
-----------------

- bpo-32176: co_flags.CO_NOFREE is now always set correctly by the code
  object constructor based on freevars and cellvars, rather than needing to
  be set correctly by the caller. This ensures it will be cleared
  automatically when additional cell references are injected into a modified
  code object and function.

- bpo-10544: Yield expressions are now deprecated in comprehensions and
  generator expressions. They are still permitted in the definition of the
  outermost iterable, as that is evaluated directly in the enclosing scope.

- bpo-32137: The repr of deeply nested dict now raises a RecursionError
  instead of crashing due to a stack overflow.

- bpo-32096: Revert memory allocator changes in the C API: move structures
  back from _PyRuntime to Objects/obmalloc.c. The memory allocators are once
  again initialized statically, and so PyMem_RawMalloc() and
  Py_DecodeLocale() can be called before _PyRuntime_Initialize().

- bpo-32043: Add a new "developer mode": new "-X dev" command line option to
  enable debug checks at runtime.

- bpo-32023: SyntaxError is now correctly raised when a generator expression
  without parenthesis is used instead of an inheritance list in a class
  definition. The duplication of the parentheses can be omitted only on
  calls.

- bpo-32012: SyntaxError is now correctly raised when a generator expression
  without parenthesis is passed as an argument, but followed by a trailing
  comma. A generator expression always needs to be directly inside a set of
  parentheses and cannot have a comma on either side.

- bpo-28180: A new internal ``_Py_SetLocaleFromEnv(category)`` helper
  function has been added in order to improve the consistency of behaviour
  across different ``libc`` implementations (e.g. Android doesn't support
  setting the locale from the environment by default).

- bpo-31949: Fixed several issues in printing tracebacks
  (PyTraceBack_Print()). Setting sys.tracebacklimit to 0 or less now
  suppresses printing tracebacks. Setting sys.tracebacklimit to None now
  causes using the default limit. Setting sys.tracebacklimit to an integer
  larger than LONG_MAX now means using the limit LONG_MAX rather than the
  default limit. Fixed integer overflows in the case of more than ``2**31``
  traceback items on Windows. Fixed output errors handling.

- bpo-30696: Fix the interactive interpreter looping endlessly when no
  memory.

- bpo-20047: Bytearray methods partition() and rpartition() now accept only
  bytes-like objects as separator, as documented.  In particular they now
  raise TypeError rather of returning a bogus result when an integer is
  passed as a separator.

- bpo-21720: BytesWarning no longer emitted when the *fromlist* argument of
  ``__import__()`` or the ``__all__`` attribute of the module contain bytes
  instances.

- bpo-31845: Environment variables are once more read correctly at
  interpreter startup.

- bpo-28936: Ensure that lexically first syntax error involving a parameter
  and ``global`` or ``nonlocal`` is detected first at a given scope. Patch
  by Ivan Levkivskyi.

- bpo-31825: Fixed OverflowError in the 'unicode-escape' codec and in
  codecs.escape_decode() when decode an escaped non-ascii byte.

- bpo-31618: The per-frame tracing logic added in 3.7a1 has been altered so
  that ``frame->f_lineno`` is updated before either ``"line"`` or
  ``"opcode"`` events are emitted. Previously, opcode events were emitted
  first, and therefore would occasionally see stale line numbers on the
  frame. The behavior of this feature has changed slightly as a result: when
  both ``f_trace_lines`` and ``f_trace_opcodes`` are enabled, line events
  now occur first.

- bpo-28603: Print the full context/cause chain of exceptions on interpreter
  exit, even if an exception in the chain is unhashable or compares equal to
  later ones. Patch by Zane Bitter.

- bpo-31786: Fix timeout rounding in the select module to round correctly
  negative timeouts between -1.0 and 0.0. The functions now block waiting
  for events as expected. Previously, the call was incorrectly non-blocking.
  Patch by Pablo Galindo.

- bpo-31781: Prevent crashes when calling methods of an uninitialized
  ``zipimport.zipimporter`` object. Patch by Oren Milman.

- bpo-30399: Standard repr() of BaseException with a single argument no
  longer contains redundant trailing comma.

- bpo-31626: Fixed a bug in debug memory allocator.  There was a write to
  freed memory after shrinking a memory block.

- bpo-30817: `PyErr_PrintEx()` clears now the ignored exception that may be
  raised by `_PySys_SetObjectId()`, for example when no memory.

Library
-------

- bpo-28556: Two minor fixes for ``typing`` module: allow shallow copying
  instances of generic classes, improve interaction of ``__init_subclass__``
  with generics. Original PRs by Ivan Levkivskyi.

- bpo-32214: PEP 557, Data Classes. Provides a decorator which adds
  boilerplate methods to classes which use type annotations so specify
  fields.

- bpo-27240: The header folding algorithm for the new email policies has
  been rewritten, which also fixes bpo-30788, bpo-31831, and bpo-32182.  In
  particular, RFC2231 folding is now done correctly.

- bpo-32186: io.FileIO.readall() and io.FileIO.read() now release the GIL
  when getting the file size. Fixed hang of all threads with inaccessible
  NFS server. Patch by Nir Soffer.

- bpo-32101: Add :attr:`sys.flags.dev_mode` flag

- bpo-32154: The ``asyncio.windows_utils.socketpair()`` function has been
  removed: use directly :func:`socket.socketpair` which is available on all
  platforms since Python 3.5 (before, it wasn't available on Windows).
  ``asyncio.windows_utils.socketpair()`` was just an alias to
  ``socket.socketpair`` on Python 3.5 and newer.

- bpo-32089: warnings: In development (-X dev) and debug mode (pydebug
  build), use the "default" action for ResourceWarning, rather than the
  "always" action, in the default warnings filters.

- bpo-32107: ``uuid.getnode()`` now preferentially returns universally
  administered MAC addresses if available, over locally administered MAC
  addresses.  This makes a better guarantee for global uniqueness of UUIDs
  returned from ``uuid.uuid1()``.  If only locally administered MAC
  addresses are available, the first such one found is returned.

- bpo-23033: Wildcard is now supported in hostname when it is one and only
  character in the left most segment of hostname in second argument of
  :meth:`ssl.match_hostname`.  Patch by Mandeep Singh.

- bpo-12239: Make :meth:`msilib.SummaryInformation.GetProperty` return
  ``None`` when the value of property is ``VT_EMPTY``.  Initial patch by
  Mark Mc Mahon.

- bpo-28334: Use :func:`os.path.expanduser` to find the ``~/.netrc`` file in
  :class:`netrc.netrc`.  If it does not exist, :exc:`FileNotFoundError` is
  raised.  Patch by Dimitri Merejkowsky.

- bpo-32121: Made ``tracemalloc.Traceback`` behave more like the traceback
  module, sorting the frames from oldest to most recent.
  ``Traceback.format()`` now accepts negative *limit*, truncating the result
  to the ``abs(limit)`` oldest frames. To get the old behaviour, one can use
  the new *most_recent_first* argument to ``Traceback.format()``. (Patch by
  Jesse Bakker.)

- bpo-31325: Fix wrong usage of :func:`collections.namedtuple` in the
  :meth:`RobotFileParser.parse() <urllib.robotparser.RobotFileParser.parse>`
  method. Initial patch by Robin Wellner.

- bpo-12382: :func:`msilib.OpenDatabase` now raises a better exception
  message when it couldn't open or create an MSI file.  Initial patch by
  William Tisäter.

- bpo-19610: ``setup()`` now warns about invalid types for some fields. The
  ``distutils.dist.Distribution`` class now warns when ``classifiers``,
  ``keywords`` and ``platforms`` fields are not specified as a list or a
  string.

- bpo-32071: Added the ``-k`` command-line option to ``python -m unittest``
  to run only tests that match the given pattern(s).

- bpo-10049: Added *nullcontext* no-op context manager to contextlib. This
  provides a simpler and faster alternative to ExitStack() when handling
  optional context managers.

- bpo-28684: The new test.support.skip_unless_bind_unix_socket() decorator
  is used here to skip asyncio tests that fail because the platform lacks a
  functional bind() function for unix domain sockets (as it is the case for
  non root users on the recent Android versions that run now SELinux in
  enforcing mode).

- bpo-32110: ``codecs.StreamReader.read(n)`` now returns not more than *n*
  characters/bytes for non-negative *n*. This makes it compatible with
  ``read()`` methods of other file-like objects.

- bpo-27535: The warnings module doesn't leak memory anymore in the hidden
  warnings registry for the "ignore" action of warnings filters.
  warn_explicit() function doesn't add the warning key to the registry
  anymore for the "ignore" action.

- bpo-32088: warnings:  When Python is build is debug mode (``Py_DEBUG``),
  :exc:`DeprecationWarning`, :exc:`PendingDeprecationWarning` and
  :exc:`ImportWarning` warnings are now displayed by default.

- bpo-1647489: Fixed searching regular expression patterns that could match
  an empty string. Non-empty string can now be correctly found after
  matching an empty string.

- bpo-25054: Added support of splitting on a pattern that could match an
  empty string.

- bpo-32072: Fixed issues with binary plists: Fixed saving bytearrays.
  Identical objects will be saved only once. Equal references will be load
  as identical objects. Added support for saving and loading recursive data
  structures.

- bpo-32069: Drop legacy SSL transport from asyncio, ssl.MemoryBIO is always
  used anyway.

- bpo-32066: asyncio: Support pathlib.Path in create_unix_connection; sock
  arg should be optional

- bpo-32046: Updates 2to3 to convert from operator.isCallable(obj) to
  callable(obj). Patch by Dong-hee Na.

- bpo-32018: inspect.signature should follow :pep:`8`, if the parameter has
  an annotation and a default value. Patch by Dong-hee Na.

- bpo-32025: Add time.thread_time() and time.thread_time_ns()

- bpo-32037: Integers that fit in a signed 32-bit integer will be now
  pickled with protocol 0 using the INT opcode.  This will decrease the size
  of a pickle, speed up pickling and unpickling, and make these integers be
  unpickled as int instances in Python 2.

- bpo-32034: Make asyncio.IncompleteReadError and LimitOverrunError
  pickleable.

- bpo-32015: Fixed the looping of asyncio in the case of reconnection the
  socket during waiting async read/write from/to the socket.

- bpo-32011: Restored support of loading marshal files with the TYPE_INT64
  code. These files can be produced in Python 2.7.

- bpo-28369: Enhance add_reader/writer check that socket is not used by some
  transport. Before, only cases when add_reader/writer were called with an
  int FD were supported.  Now the check is implemented correctly for all
  file-like objects.

- bpo-31976: Fix race condition when flushing a file is slow, which can
  cause a segfault if closing the file from another thread.

- bpo-31985: Formally deprecated aifc.openfp, sunau.openfp, and wave.openfp.
  Since change 7bc817d5ba917528e8bd07ec461c635291e7b06a in 1993, openfp in
  each of the three modules had been pointing to that module's open function
  as a matter of backwards compatibility, though it had been both untested
  and undocumented.

- bpo-21862: cProfile command line now accepts `-m module_name` as an
  alternative to script path. Patch by Sanyam Khurana.

- bpo-31970: Reduce performance overhead of asyncio debug mode.

- bpo-31843: *database* argument of sqlite3.connect() now accepts a
  :term:`path-like object`, instead of just a string.

- bpo-31945: Add Configurable *blocksize* to ``HTTPConnection`` and
  ``HTTPSConnection`` for improved upload throughput.  Patch by Nir Soffer.

- bpo-31943: Add a ``cancelled()`` method to :class:`asyncio.Handle`.  Patch
  by Marat Sharafutdinov.

- bpo-9678: Fixed determining the MAC address in the uuid module: Using
  ifconfig on NetBSD and OpenBSD. Using arp on Linux, FreeBSD, NetBSD and
  OpenBSD. Based on patch by Takayuki Shimizukawa.

- bpo-30057: Fix potential missed signal in signal.signal().

- bpo-31933: Fix Blake2 params leaf_size and node_offset on big endian
  platforms. Patch by Jack O'Connor.

- bpo-21423: Add an initializer argument to {Process,Thread}PoolExecutor

- bpo-31927: Fixed compilation of the socket module on NetBSD 8.  Fixed
  assertion failure or reading arbitrary data when parse a AF_BLUETOOTH
  address on NetBSD and DragonFly BSD.

- bpo-27666: Fixed stack corruption in curses.box() and curses.ungetmouse()
  when the size of types chtype or mmask_t is less than the size of C long.
  curses.box() now accepts characters as arguments.  Based on patch by Steve
  Fink.

- bpo-31917: Add 3 new clock identifiers: :data:`time.CLOCK_BOOTTIME`,
  :data:`time.CLOCK_PROF` and :data:`time.CLOCK_UPTIME`.

- bpo-31897: plistlib now catches more errors when read binary plists and
  raises InvalidFileException instead of unexpected exceptions.

- bpo-25720: Fix the method for checking pad state of curses WINDOW. Patch
  by Masayuki Yamamoto.

- bpo-31893: Fixed the layout of the kqueue_event structure on OpenBSD and
  NetBSD. Fixed the comparison of the kqueue_event objects.

- bpo-31891: Fixed building the curses module on NetBSD.

- bpo-31884: added required constants to subprocess module for setting
  priority on windows

- bpo-28281: Remove year (1-9999) limits on the Calendar.weekday() function.
  Patch by Mark Gollahon.

- bpo-31702: crypt.mksalt() now allows to specify the number of rounds for
  SHA-256 and SHA-512 hashing.

- bpo-30639: :func:`inspect.getfile` no longer computes the repr of unknown
  objects to display in an error message, to protect against badly behaved
  custom reprs.

- bpo-30768: Fix the pthread+semaphore implementation of
  PyThread_acquire_lock_timed() when called with timeout > 0 and
  intr_flag=0: recompute the timeout if sem_timedwait() is interrupted by a
  signal (EINTR). See also the :pep:`475`.

- bpo-31854: Add ``mmap.ACCESS_DEFAULT`` constant.

- bpo-31834: Use optimized code for BLAKE2 only with SSSE3+. The pure SSE2
  implementation is slower than the pure C reference implementation.

- bpo-28292: Calendar.itermonthdates() will now consistently raise an
  exception when a date falls outside of the 0001-01-01 through 9999-12-31
  range.  To support applications that cannot tolerate such exceptions, the
  new methods itermonthdays3() and itermonthdays4() are added.  The new
  methods return tuples and are not restricted by the range supported by
  datetime.date.

- bpo-28564: The shutil.rmtree() function has been sped up to 20--40%. This
  was done using the os.scandir() function.

- bpo-28416: Instances of pickle.Pickler subclass with the persistent_id()
  method and pickle.Unpickler subclass with the persistent_load() method no
  longer create reference cycles.

- bpo-31653: Don't release the GIL if we can acquire a multiprocessing
  semaphore immediately.

- bpo-28326: Fix multiprocessing.Process when stdout and/or stderr is closed
  or None.

- bpo-20825: Add `subnet_of` and `superset_of` containment tests to
  :class:`ipaddress.IPv6Network` and :class:`ipaddress.IPv4Network`. Patch
  by Michel Albert and Cheryl Sabella.

- bpo-31827: Remove the os.stat_float_times() function. It was introduced in
  Python 2.3 for backward compatibility with Python 2.2, and was deprecated
  since Python 3.1.

- bpo-31756: Add a ``subprocess.Popen(text=False)`` keyword argument to
  `subprocess` functions to be more explicit about when the library should
  attempt to decode outputs into text. Patch by Andrew Clegg.

- bpo-31819: Add AbstractEventLoop.sock_recv_into().

- bpo-31457: If nested log adapters are used, the inner ``process()``
  methods are no longer omitted.

- bpo-31457: The ``manager`` property on LoggerAdapter objects is now
  properly settable.

- bpo-31806: Fix timeout rounding in time.sleep(), threading.Lock.acquire()
  and socket.socket.settimeout() to round correctly negative timeouts
  between -1.0 and 0.0. The functions now block waiting for events as
  expected. Previously, the call was incorrectly non-blocking. Patch by
  Pablo Galindo.

- bpo-31803: time.clock() and time.get_clock_info('clock') now emit a
  DeprecationWarning warning.

- bpo-31800: Extended support for parsing UTC offsets. strptime '%z' can now
  parse the output generated by datetime.isoformat, including seconds and
  microseconds.

- bpo-28603: traceback: Fix a TypeError that occurred during printing of
  exception tracebacks when either the current exception or an exception in
  its context/cause chain is unhashable. Patch by Zane Bitter.

- bpo-30541: Add new function to seal a mock and prevent the automatically
  creation of child mocks. Patch by Mario Corchero.

- bpo-31784: Implement the :pep:`564`, add new 6 new functions with
  nanosecond resolution to the :mod:`time` module:
  :func:`~time.clock_gettime_ns`, :func:`~time.clock_settime_ns`,
  :func:`~time.monotonic_ns`, :func:`~time.perf_counter_ns`,
  :func:`~time.process_time_ns`, :func:`~time.time_ns`.

- bpo-30143: 2to3 now generates a code that uses abstract collection classes
  from collections.abc rather than collections.

- bpo-31770: Prevent a crash when calling the ``__init__()`` method of a
  ``sqlite3.Cursor`` object more than once. Patch by Oren Milman.

- bpo-31764: Prevent a crash in ``sqlite3.Cursor.close()`` in case the
  ``Cursor`` object is uninitialized. Patch by Oren Milman.

- bpo-31752: Fix possible crash in timedelta constructor called with custom
  integers.

- bpo-31620: an empty asyncio.Queue now doesn't leak memory when queue.get
  pollers timeout

- bpo-31690: Allow the flags re.ASCII, re.LOCALE, and re.UNICODE to be used
  as group flags for regular expressions.

- bpo-30349: FutureWarning is now emitted if a regular expression contains
  character set constructs that will change semantically in the future
  (nested sets and set operations).

- bpo-31664: Added support for the Blowfish hashing in the crypt module.

- bpo-31632: Fix method set_protocol() of class _SSLProtocolTransport in
  asyncio module. This method was previously modifying a wrong reference to
  the protocol.

- bpo-15037: Added a workaround for getkey() in curses for ncurses 5.7 and
  earlier.

- bpo-31307: Allow use of bytes objects for arguments to
  :meth:`configparser.ConfigParser.read`. Patch by Vincent Michel.

- bpo-31334: Fix ``poll.poll([timeout])`` in the ``select`` module for
  arbitrary negative timeouts on all OSes where it can only be a
  non-negative integer or -1. Patch by Riccardo Coccioli.

- bpo-31310: multiprocessing's semaphore tracker should be launched again if
  crashed.

- bpo-31308: Make multiprocessing's forkserver process immune to Ctrl-C and
  other user interruptions. If it crashes, restart it when necessary.

- bpo-31245: Added support for AF_UNIX socket in asyncio
  `create_datagram_endpoint`.

- bpo-30553: Add HTTP/2 status code 421 (Misdirected Request) to
  :class:`http.HTTPStatus`. Patch by Vitor Pereira.

Documentation
-------------

- bpo-32105: Added asyncio.BaseEventLoop.connect_accepted_socket
  versionadded marker.

Tests
-----

- bpo-31380: Skip test_httpservers test_undecodable_file on macOS: fails on
  APFS.

- bpo-31705: Skip test_socket.test_sha256() on Linux kernel older than 4.5.
  The test fails with ENOKEY on kernel 3.10 (on ppc64le). A fix was merged
  into the kernel 4.5.

- bpo-32138: Skip on Android test_faulthandler tests that raise SIGSEGV and
  remove the test.support.requires_android_level decorator.

- bpo-32136: The runtime embedding tests have been split out from
  ``Lib/test/test_capi.py`` into a new ``Lib/test/test_embed.py`` file.

- bpo-28668: test.support.requires_multiprocessing_queue is removed. Skip
  tests with test.support.import_module('multiprocessing.synchronize')
  instead when the semaphore implementation is broken or missing.

- bpo-32126: Skip test_get_event_loop_new_process in
  test.test_asyncio.test_events when sem_open() is not functional.

- bpo-31174: Fix test_tools.test_unparse: DirectoryTestCase now stores the
  names sample to always test the same files. It prevents false alarms when
  hunting reference leaks.

Build
-----

- bpo-28538: Revert the previous changes, the if_nameindex structure is
  defined by Unified Headers.

- bpo-28762: Revert the last commit, the F_LOCK macro is defined by Android
  Unified Headers.

- bpo-29040: Support building Android with Unified Headers. The first NDK
  release to support Unified Headers is android-ndk-r14.

- bpo-32059: ``detect_modules()`` in ``setup.py`` now also searches the
  sysroot paths when cross-compiling.

- bpo-31957: Fixes Windows SDK version detection when building for Windows.

- bpo-31609: Fixes quotes in PCbuild/clean.bat

- bpo-31934: Abort the build when building out of a not clean source tree.

- bpo-31926: Fixed Argument Clinic sometimes causing compilation errors when
  there was more than one function and/or method in a .c file with the same
  name.

- bpo-28791: Update Windows builds to use SQLite 3.21.0.

- bpo-28791: Update OS X installer to use SQLite 3.21.0.

- bpo-28643: Record profile-opt build progress with stamp files.

- bpo-31866: Finish removing support for AtheOS.

Windows
-------

- bpo-1102: Return ``None`` when ``View.Fetch()`` returns
  ``ERROR_NO_MORE_ITEMS`` instead of raising ``MSIError``. Initial patch by
  Anthony Tuininga.

- bpo-31944: Fixes Modify button in Apps and Features dialog.

- bpo-20486: Implement the ``Database.Close()`` method to help closing MSI
  database objects.

- bpo-31857: Make the behavior of USE_STACKCHECK deterministic in a
  multi-threaded environment.

macOS
-----

- bpo-31392: Update macOS installer to use OpenSSL 1.0.2m

IDLE
----

- bpo-32207: Improve tk event exception tracebacks in IDLE. When tk event
  handling is driven by IDLE's run loop, a confusing and distracting
  queue.EMPTY traceback context is no longer added to tk event exception
  tracebacks.  The traceback is now the same as when event handling is
  driven by user code.  Patch based on a suggestion by Serhiy Storchaka.

- bpo-32164: Delete unused file idlelib/tabbedpages.py. Use of TabbedPageSet
  in configdialog was replaced by ttk.Notebook.

- bpo-32100: IDLE: Fix old and new bugs in pathbrowser; improve tests. Patch
  mostly by Cheryl Sabella.

- bpo-31858: IDLE -- Restrict shell prompt manipulation to the shell. Editor
  and output windows only see an empty last prompt line.  This simplifies
  the code and fixes a minor bug when newline is inserted. Sys.ps1, if
  present, is read on Shell start-up, but is not set or changed.

- bpo-31860: The font sample in the IDLE configuration dialog is now
  editable. Changes persist while IDLE remains open

- bpo-31836: Test_code_module now passes if run after test_idle, which sets
  ps1. The code module uses sys.ps1 if present or sets it to '>>> ' if not.
  Test_code_module now properly tests both behaviors.  Ditto for ps2.

- bpo-28603: Fix a TypeError that caused a shell restart when printing a
  traceback that includes an exception that is unhashable. Patch by Zane
  Bitter.

- bpo-13802: Use non-Latin characters in the IDLE's Font settings sample.
  Even if one selects a font that defines a limited subset of the unicode
  Basic Multilingual Plane, tcl/tk will use other fonts that define a
  character. The expanded example give users of non-Latin characters a
  better idea of what they might see in IDLE's shell and editors. To make
  room for the expanded sample, frames on the Font tab are re-arranged.  The
  Font/Tabs help explains a bit about the additions.

Tools/Demos
-----------

- bpo-32159: Remove CVS and Subversion tools: remove svneol.py and
  treesync.py scripts. CPython migrated from CVS to Subversion, to
  Mercurial, and then to Git. CVS and Subversion are no longer used to
  develop CPython.

- bpo-30722: Make redemo work with Python 3.6 and newer versions. Also,
  remove the ``LOCALE`` option since it doesn't work with string patterns in
  Python 3. Patch by Christoph Sarnowski.

C API
-----

- bpo-20891: Fix PyGILState_Ensure(). When PyGILState_Ensure() is called in
  a non-Python thread before PyEval_InitThreads(), only call
  PyEval_InitThreads() after calling PyThreadState_New() to fix a crash.

- bpo-32125: The ``Py_UseClassExceptionsFlag`` flag has been removed. It was
  deprecated and wasn't used anymore since Python 2.0.

- bpo-25612: Move the current exception state from the frame object to the
  co-routine. This simplifies the interpreter and fixes a couple of obscure
  bugs caused by having swap exception state when entering or exiting a
  generator.

- bpo-23699: Add Py_RETURN_RICHCOMPARE macro to reduce boilerplate code in
  rich comparison functions.

- bpo-30697: The `PyExc_RecursionErrorInst` singleton is removed and
  `PyErr_NormalizeException()` does not use it anymore. This singleton is
  persistent and its members being never cleared may cause a segfault during
  finalization of the interpreter. See also issue #22898.


What's New in Python 3.7.0 alpha 2?
===================================

*Release date: 2017-10-16*

Core and Builtins
-----------------

- bpo-31558: ``gc.freeze()`` is a new API that allows for moving all objects
  currently tracked by the garbage collector to a permanent generation,
  effectively removing them from future collection events. This can be used
  to protect those objects from having their PyGC_Head mutated. In effect,
  this enables great copy-on-write stability at fork().

- bpo-31642: Restored blocking "from package import module" by setting
  sys.modules["package.module"] to None.

- bpo-31708: Allow use of asynchronous generator expressions in synchronous
  functions.

- bpo-31709: Drop support of asynchronous __aiter__.

- bpo-30404: The -u option now makes the stdout and stderr streams
  unbuffered rather than line-buffered.

- bpo-31619: Fixed a ValueError when convert a string with large number of
  underscores to integer with binary base.

- bpo-31602: Fix an assertion failure in `zipimporter.get_source()` in case
  of a bad `zlib.decompress()`. Patch by Oren Milman.

- bpo-31592: Fixed an assertion failure in Python parser in case of a bad
  `unicodedata.normalize()`. Patch by Oren Milman.

- bpo-31588: Raise a `TypeError` with a helpful error message when class
  creation fails due to a metaclass with a bad ``__prepare__()`` method.
  Patch by Oren Milman.

- bpo-31574: Importlib was instrumented with two dtrace probes to profile
  import timing.

- bpo-31566: Fix an assertion failure in `_warnings.warn()` in case of a bad
  ``__name__`` global. Patch by Oren Milman.

- bpo-31506: Improved the error message logic for object.__new__ and
  object.__init__.

- bpo-31505: Fix an assertion failure in `json`, in case
  `_json.make_encoder()` received a bad `encoder()` argument. Patch by Oren
  Milman.

- bpo-31492: Fix assertion failures in case of failing to import from a
  module with a bad ``__name__`` attribute, and in case of failing to access
  an attribute of such a module. Patch by Oren Milman.

- bpo-31478: Fix an assertion failure in `_random.Random.seed()` in case the
  argument has a bad ``__abs__()`` method. Patch by Oren Milman.

- bpo-31336: Speed up class creation by 10-20% by reducing the overhead in
  the necessary special method lookups.  Patch by Stefan Behnel.

- bpo-31415: Add ``-X importtime`` option to show how long each import
  takes. It can be used to optimize application's startup time.  Support the
  :envvar:`PYTHONPROFILEIMPORTTIME` as an equivalent way to enable this.

- bpo-31410: Optimized calling wrapper and classmethod descriptors.

- bpo-31353: :pep:`553` - Add a new built-in called ``breakpoint()`` which
  calls ``sys.breakpointhook()``.  By default this imports ``pdb`` and calls
  ``pdb.set_trace()``, but users may override ``sys.breakpointhook()`` to
  call whatever debugger they want.  The original value of the hook is saved
  in ``sys.__breakpointhook__``.

- bpo-17852: Maintain a list of open buffered files, flush them before
  exiting the interpreter.  Based on a patch from Armin Rigo.

- bpo-31315: Fix an assertion failure in imp.create_dynamic(), when
  spec.name is not a string. Patch by Oren Milman.

- bpo-31311: Fix a crash in the ``__setstate__()`` method of
  `ctypes._CData`, in case of a bad ``__dict__``. Patch by Oren Milman.

- bpo-31293: Fix crashes in true division and multiplication of a timedelta
  object by a float with a bad as_integer_ratio() method. Patch by Oren
  Milman.

- bpo-31285: Fix an assertion failure in `warnings.warn_explicit`, when the
  return value of the received loader's get_source() has a bad splitlines()
  method. Patch by Oren Milman.

- bpo-30406: Make ``async`` and ``await`` proper keywords, as specified in
  :pep:`492`.

Library
-------

- bpo-30058: Fixed buffer overflow in select.kqueue.control().

- bpo-31672: ``idpattern`` in ``string.Template`` matched some non-ASCII
  characters. Now it uses ``-i`` regular expression local flag to avoid
  non-ASCII characters.

- bpo-31701: On Windows, faulthandler.enable() now ignores MSC and COM
  exceptions.

- bpo-31728: Prevent crashes in `_elementtree` due to unsafe cleanup of
  `Element.text` and `Element.tail`. Patch by Oren Milman.

- bpo-31671: Now ``re.compile()`` converts passed RegexFlag to normal int
  object before compiling. bm_regex_compile benchmark shows 14% performance
  improvements.

- bpo-30397: The types of compiled regular objects and match objects are now
  exposed as `re.Pattern` and `re.Match`.  This adds information in pydoc
  output for the re module.

- bpo-31675: Fixed memory leaks in Tkinter's methods splitlist() and split()
  when pass a string larger than 2 GiB.

- bpo-31673: Fixed typo in the name of Tkinter's method adderrorinfo().

- bpo-31648: Improvements to path predicates in ElementTree: Allow
  whitespace around predicate parts, i.e. "[a = 'text']" instead of
  requiring the less readable "[a='text']". Add support for text comparison
  of the current node, like "[.='text']". Patch by Stefan Behnel.

- bpo-30806: Fix the string representation of a netrc object.

- bpo-31638: Add optional argument ``compressed`` to
  ``zipapp.create_archive``, and add option ``--compress`` to the command
  line interface of ``zipapp``.

- bpo-25351: Avoid venv activate failures with undefined variables

- bpo-20519: Avoid ctypes use (if possible) and improve import time for
  uuid.

- bpo-28293: The regular expression cache is no longer completely dumped
  when it is full.

- bpo-31596: Added pthread_getcpuclockid() to the time module

- bpo-27494: Make 2to3 accept a trailing comma in generator expressions. For
  example, ``set(x for x in [],)`` is now allowed.

- bpo-30347: Stop crashes when concurrently iterate over itertools.groupby()
  iterators.

- bpo-30346: An iterator produced by itertools.groupby() iterator now
  becomes exhausted after advancing the groupby iterator.

- bpo-31556: Cancel asyncio.wait_for future faster if timeout <= 0

- bpo-31540: Allow passing a context object in
  :class:`concurrent.futures.ProcessPoolExecutor` constructor. Also, free
  job resources in :class:`concurrent.futures.ProcessPoolExecutor` earlier
  to improve memory usage when a worker waits for new jobs.

- bpo-31516: ``threading.current_thread()`` should not return a dummy thread
  at shutdown.

- bpo-31525: In the sqlite module, require the sqlite3_prepare_v2 API. Thus,
  the sqlite module now requires sqlite version at least 3.3.9.

- bpo-26510: argparse subparsers are now required by default.  This matches
  behaviour in Python 2. For optional subparsers, use the new parameter
  ``add_subparsers(required=False)``. Patch by Anthony Sottile. (As of
  3.7.0rc1, the default was changed to not required as had been the case
  since Python 3.3.)

- bpo-27541: Reprs of subclasses of some collection and iterator classes
  (`bytearray`, `array.array`, `collections.deque`,
  `collections.defaultdict`, `itertools.count`, `itertools.repeat`) now
  contain actual type name insteads of hardcoded name of the base class.

- bpo-31351: python -m ensurepip now exits with non-zero exit code if pip
  bootstrapping has failed.

- bpo-31389: ``pdb.set_trace()`` now takes an optional keyword-only argument
  ``header``. If given, this is printed to the console just before debugging
  begins.

Documentation
-------------

- bpo-31537: Fix incorrect usage of ``get_history_length`` in readline
  documentation example code. Patch by Brad Smith.

- bpo-30085: The operator functions without double underscores are preferred
  for clarity. The one with underscores are only kept for
  back-compatibility.

Build
-----

- bpo-31696: Improve compiler version information in :data:`sys.version`
  when Python is built with Clang.

- bpo-31625: Stop using ranlib on static libraries. Instead, we assume ar
  supports the 's' flag.

- bpo-31624: Remove support for BSD/OS.

- bpo-22140: Prevent double substitution of prefix in python-config.sh.

- bpo-31569: Correct PCBuild/ case to PCbuild/ in build scripts and
  documentation.

- bpo-31536: Avoid wholesale rebuild after `make regen-all` if nothing
  changed.

IDLE
----

- bpo-31460: Simplify the API of IDLE's Module Browser. Passing a widget
  instead of an flist with a root widget opens the option of creating a
  browser frame that is only part of a window.  Passing a full file name
  instead of pieces assumed to come from a .py file opens the possibility of
  browsing python files that do not end in .py.

- bpo-31649: IDLE - Make _htest, _utest parameters keyword only.

- bpo-31559: Remove test order dependence in idle_test.test_browser.

- bpo-31459: Rename IDLE's module browser from Class Browser to Module
  Browser. The original module-level class and method browser became a
  module browser, with the addition of module-level functions, years ago.
  Nested classes and functions were added yesterday.  For
  back-compatibility, the virtual event <<open-class-browser>>, which
  appears on the Keys tab of the Settings dialog, is not changed. Patch by
  Cheryl Sabella.

- bpo-31500: Default fonts now are scaled on HiDPI displays.

- bpo-1612262: IDLE module browser now shows nested classes and functions.
  Original patches for code and tests by Guilherme Polo and Cheryl Sabella,
  respectively.

C API
-----

- bpo-28280: Make `PyMapping_Keys()`, `PyMapping_Values()` and
  `PyMapping_Items()` always return a `list` (rather than a `list` or a
  `tuple`). Patch by Oren Milman.

- bpo-31532: Fix memory corruption due to allocator mix in getpath.c between
  Py_GetPath() and Py_SetPath()

- bpo-25658: Implement :pep:`539` for Thread Specific Storage (TSS) API: it
  is a new Thread Local Storage (TLS) API to CPython which would supersede
  use of the existing TLS API within the CPython interpreter, while
  deprecating the existing API. PEP written by Erik M. Bray, patch by
  Masayuki Yamamoto.


What's New in Python 3.7.0 alpha 1?
===================================

*Release date: 2017-09-19*

Security
--------

- bpo-29781: SSLObject.version() now correctly returns None when handshake
  over BIO has not been performed yet.

- bpo-29505: Add fuzz tests for float(str), int(str), unicode(str); for
  oss-fuzz.

- bpo-30947: Upgrade libexpat embedded copy from version 2.2.1 to 2.2.3 to
  get security fixes.

- bpo-30730: Prevent environment variables injection in subprocess on
  Windows.  Prevent passing other environment variables and command
  arguments.

- bpo-30694: Upgrade expat copy from 2.2.0 to 2.2.1 to get fixes of multiple
  security vulnerabilities including: CVE-2017-9233 (External entity
  infinite loop DoS), CVE-2016-9063 (Integer overflow, re-fix),
  CVE-2016-0718 (Fix regression bugs from 2.2.0's fix to CVE-2016-0718) and
  CVE-2012-0876 (Counter hash flooding with SipHash). Note: the
  CVE-2016-5300 (Use os-specific entropy sources like getrandom) doesn't
  impact Python, since Python already gets entropy from the OS to set the
  expat secret using ``XML_SetHashSalt()``.

- bpo-30500: Fix urllib.parse.splithost() to correctly parse fragments. For
  example, ``splithost('//127.0.0.1#@evil.com/')`` now correctly returns the
  ``127.0.0.1`` host, instead of treating ``@evil.com`` as the host in an
  authentication (``login@host``).

- bpo-29591: Update expat copy from 2.1.1 to 2.2.0 to get fixes of
  CVE-2016-0718 and CVE-2016-4472. See
  https://sourceforge.net/p/expat/bugs/537/ for more information.

Core and Builtins
-----------------

- bpo-31490: Fix an assertion failure in `ctypes` class definition, in case
  the class has an attribute whose name is specified in ``_anonymous_`` but
  not in ``_fields_``. Patch by Oren Milman.

- bpo-31471: Fix an assertion failure in `subprocess.Popen()` on Windows, in
  case the env argument has a bad keys() method. Patch by Oren Milman.

- bpo-31418: Fix an assertion failure in `PyErr_WriteUnraisable()` in case
  of an exception with a bad ``__module__`` attribute. Patch by Oren Milman.

- bpo-31416: Fix assertion failures in case of a bad warnings.filters or
  warnings.defaultaction. Patch by Oren Milman.

- bpo-28411: Change direct usage of PyInterpreterState.modules to
  PyImport_GetModuleDict(). Also introduce more uniformity in other code
  that deals with sys.modules. This helps reduce complications when working
  on sys.modules.

- bpo-28411: Switch to the abstract API when dealing with
  ``PyInterpreterState.modules``. This allows later support for all dict
  subclasses and other Mapping implementations.  Also add a
  ``PyImport_GetModule()`` function to reduce a bunch of duplicated code.

- bpo-31411: Raise a TypeError instead of SystemError in case
  warnings.onceregistry is not a dictionary. Patch by Oren Milman.

- bpo-31344: For finer control of tracing behaviour when testing the
  interpreter, two new frame attributes have been added to control the
  emission of particular trace events: ``f_trace_lines`` (``True`` by
  default) to turn off per-line trace events; and ``f_trace_opcodes``
  (``False`` by default) to turn on per-opcode trace events.

- bpo-31373: Fix several possible instances of undefined behavior due to
  floating-point demotions.

- bpo-30465: Location information (``lineno`` and ``col_offset``) in
  f-strings is now (mostly) correct.  This fixes tools like flake8 from
  showing warnings on the wrong line (typically the first line of the file).

- bpo-30860: Consolidate CPython's global runtime state under a single
  struct.  This improves discoverability of the runtime state.

- bpo-31347: Fix possible undefined behavior in _PyObject_FastCall_Prepend.

- bpo-31343: Include sys/sysmacros.h for major(), minor(), and makedev().
  GNU C libray plans to remove the functions from sys/types.h.

- bpo-31291: Fix an assertion failure in `zipimport.zipimporter.get_data` on
  Windows, when the return value of ``pathname.replace('/','\\')`` isn't a
  string. Patch by Oren Milman.

- bpo-31271: Fix an assertion failure in the write() method of
  `io.TextIOWrapper`, when the encoder doesn't return a bytes object. Patch
  by Oren Milman.

- bpo-31243: Fix a crash in some methods of `io.TextIOWrapper`, when the
  decoder's state is invalid. Patch by Oren Milman.

- bpo-30721: ``print`` now shows correct usage hint for using Python 2
  redirection syntax.  Patch by Sanyam Khurana.

- bpo-31070: Fix a race condition in importlib _get_module_lock().

- bpo-30747: Add a non-dummy implementation of _Py_atomic_store and
  _Py_atomic_load on MSVC.

- bpo-31095: Fix potential crash during GC caused by ``tp_dealloc`` which
  doesn't call ``PyObject_GC_UnTrack()``.

- bpo-31071: Avoid masking original TypeError in call with * unpacking when
  other arguments are passed.

- bpo-30978: str.format_map() now passes key lookup exceptions through.
  Previously any exception was replaced with a KeyError exception.

- bpo-30808: Use _Py_atomic API for concurrency-sensitive signal state.

- bpo-30876: Relative import from unloaded package now reimports the package
  instead of failing with SystemError.  Relative import from non-package now
  fails with ImportError rather than SystemError.

- bpo-30703: Improve signal delivery. Avoid using Py_AddPendingCall from
  signal handler, to avoid calling signal-unsafe functions. The tests I'm
  adding here fail without the rest of the patch, on Linux and OS X. This
  means our signal delivery logic had defects (some signals could be lost).

- bpo-30765: Avoid blocking in pthread_mutex_lock() when
  PyThread_acquire_lock() is asked not to block.

- bpo-31161: Make sure the 'Missing parentheses' syntax error message is
  only applied to SyntaxError, not to subclasses. Patch by Martijn Pieters.

- bpo-30814: Fixed a race condition when import a submodule from a package.

- bpo-30736: The internal unicodedata database has been upgraded to Unicode
  10.0.

- bpo-30604: Move co_extra_freefuncs from per-thread to per-interpreter to
  avoid crashes.

- bpo-30597: ``print`` now shows expected input in custom error message when
  used as a Python 2 statement. Patch by Sanyam Khurana.

- bpo-30682: Removed a too-strict assertion that failed for certain
  f-strings, such as eval("f'\\\n'") and eval("f'\\\r'").

- bpo-30501: The compiler now produces more optimal code for complex
  condition expressions in the "if", "while" and "assert" statement, the
  "if" expression, and generator expressions and comprehensions.

- bpo-28180: Implement :pep:`538` (legacy C locale coercion). This means
  that when a suitable coercion target locale is available, both the core
  interpreter and locale-aware C extensions will assume the use of UTF-8 as
  the default text encoding, rather than ASCII.

- bpo-30486: Allows setting cell values for __closure__. Patch by Lisa
  Roach.

- bpo-30537: itertools.islice now accepts integer-like objects (having an
  __index__ method) as start, stop, and slice arguments

- bpo-25324: Tokens needed for parsing in Python moved to C. ``COMMENT``,
  ``NL`` and ``ENCODING``. This way the tokens and tok_names in the token
  module don't get changed when you import the tokenize module.

- bpo-29104: Fixed parsing backslashes in f-strings.

- bpo-27945: Fixed various segfaults with dict when input collections are
  mutated during searching, inserting or comparing.  Based on patches by
  Duane Griffin and Tim Mitchell.

- bpo-25794: Fixed type.__setattr__() and type.__delattr__() for
  non-interned attribute names.  Based on patch by Eryk Sun.

- bpo-30039: If a KeyboardInterrupt happens when the interpreter is in the
  middle of resuming a chain of nested 'yield from' or 'await' calls, it's
  now correctly delivered to the innermost frame.

- bpo-28974: ``object.__format__(x, '')`` is now equivalent to ``str(x)``
  rather than ``format(str(self), '')``.

- bpo-30024: Circular imports involving absolute imports with binding a
  submodule to a name are now supported.

- bpo-12414: sys.getsizeof() on a code object now returns the sizes which
  includes the code struct and sizes of objects which it references. Patch
  by Dong-hee Na.

- bpo-29839: len() now raises ValueError rather than OverflowError if
  __len__() returned a large negative integer.

- bpo-11913: README.rst is now included in the list of distutils standard
  READMEs and therefore included in source distributions.

- bpo-29914: Fixed default implementations of __reduce__ and
  __reduce_ex__(). object.__reduce__() no longer takes arguments,
  object.__reduce_ex__() now requires one argument.

- bpo-29949: Fix memory usage regression of set and frozenset object.

- bpo-29935: Fixed error messages in the index() method of tuple, list and
  deque when pass indices of wrong type.

- bpo-29816: Shift operation now has less opportunity to raise
  OverflowError. ValueError always is raised rather than OverflowError for
  negative counts. Shifting zero with non-negative count always returns
  zero.

- bpo-24821: Fixed the slowing down to 25 times in the searching of some
  unlucky Unicode characters.

- bpo-29102: Add a unique ID to PyInterpreterState.  This makes it easier to
  identify each subinterpreter.

- bpo-29894: The deprecation warning is emitted if __complex__ returns an
  instance of a strict subclass of complex.  In a future versions of Python
  this can be an error.

- bpo-29859: Show correct error messages when any of the pthread_* calls in
  thread_pthread.h fails.

- bpo-29849: Fix a memory leak when an ImportError is raised during from
  import.

- bpo-28856: Fix an oversight that %b format for bytes should support
  objects follow the buffer protocol.

- bpo-29723: The ``sys.path[0]`` initialization change for bpo-29139 caused
  a regression by revealing an inconsistency in how sys.path is initialized
  when executing ``__main__`` from a zipfile, directory, or other import
  location. The interpreter now consistently avoids ever adding the import
  location's parent directory to ``sys.path``, and ensures no other
  ``sys.path`` entries are inadvertently modified when inserting the import
  location named on the command line.

- bpo-29568: Escaped percent "%%" in the format string for classic string
  formatting no longer allows any characters between two percents.

- bpo-29714: Fix a regression that bytes format may fail when containing
  zero bytes inside.

- bpo-29695: bool(), float(), list() and tuple() no longer take keyword
  arguments. The first argument of int() can now be passes only as
  positional argument.

- bpo-28893: Set correct __cause__ for errors about invalid awaitables
  returned from __aiter__ and __anext__.

- bpo-28876: ``bool(range)`` works even if ``len(range)`` raises
  :exc:`OverflowError`.

- bpo-29683: Fixes to memory allocation in _PyCode_SetExtra.  Patch by Brian
  Coleman.

- bpo-29684: Fix minor regression of PyEval_CallObjectWithKeywords. It
  should raise TypeError when kwargs is not a dict.  But it might cause segv
  when args=NULL and kwargs is not a dict.

- bpo-28598: Support __rmod__ for subclasses of str being called before
  str.__mod__. Patch by Martijn Pieters.

- bpo-29607: Fix stack_effect computation for CALL_FUNCTION_EX. Patch by
  Matthieu Dartiailh.

- bpo-29602: Fix incorrect handling of signed zeros in complex constructor
  for complex subclasses and for inputs having a __complex__ method. Patch
  by Serhiy Storchaka.

- bpo-29347: Fixed possibly dereferencing undefined pointers when creating
  weakref objects.

- bpo-29463: Add ``docstring`` field to Module, ClassDef, FunctionDef, and
  AsyncFunctionDef ast nodes.  docstring is not first stmt in their body
  anymore.  It affects ``co_firstlineno`` and ``co_lnotab`` of code object
  for module and class. (Reverted in :issue:`32911`.)

- bpo-29438: Fixed use-after-free problem in key sharing dict.

- bpo-29546: Set the 'path' and 'name' attribute on ImportError for ``from
  ... import ...``.

- bpo-29546: Improve from-import error message with location

- bpo-29478: If max_line_length=None is specified while using the Compat32
  policy, it is no longer ignored.  Patch by Mircea Cosbuc.

- bpo-29319: Prevent RunMainFromImporter overwriting sys.path[0].

- bpo-29337: Fixed possible BytesWarning when compare the code objects.
  Warnings could be emitted at compile time.

- bpo-29327: Fixed a crash when pass the iterable keyword argument to
  sorted().

- bpo-29034: Fix memory leak and use-after-free in os module
  (path_converter).

- bpo-29159: Fix regression in bytes(x) when x.__index__() raises Exception.

- bpo-29049: Call _PyObject_GC_TRACK() lazily when calling Python function.
  Calling function is up to 5% faster.

- bpo-28927: bytes.fromhex() and bytearray.fromhex() now ignore all ASCII
  whitespace, not only spaces.  Patch by Robert Xiao.

- bpo-28932: Do not include <sys/random.h> if it does not exist.

- bpo-25677: Correct the positioning of the syntax error caret for indented
  blocks. Based on patch by Michael Layzell.

- bpo-29000: Fixed bytes formatting of octals with zero padding in alternate
  form.

- bpo-18896: Python function can now have more than 255 parameters.
  collections.namedtuple() now supports tuples with more than 255 elements.

- bpo-28596: The preferred encoding is UTF-8 on Android. Patch written by
  Chi Hsuan Yen.

- bpo-22257: Clean up interpreter startup (see :pep:`432`).

- bpo-26919: On Android, operating system data is now always encoded/decoded
  to/from UTF-8, instead of the locale encoding to avoid inconsistencies
  with os.fsencode() and os.fsdecode() which are already using UTF-8.

- bpo-28991: functools.lru_cache() was susceptible to an obscure reentrancy
  bug triggerable by a monkey-patched len() function.

- bpo-28147: Fix a memory leak in split-table dictionaries: setattr() must
  not convert combined table into split table. Patch written by INADA Naoki.

- bpo-28739: f-string expressions are no longer accepted as docstrings and
  by ast.literal_eval() even if they do not include expressions.

- bpo-28512: Fixed setting the offset attribute of SyntaxError by
  PyErr_SyntaxLocationEx() and PyErr_SyntaxLocationObject().

- bpo-28918: Fix the cross compilation of xxlimited when Python has been
  built with Py_DEBUG defined.

- bpo-23722: Rather than silently producing a class that doesn't support
  zero-argument ``super()`` in methods, failing to pass the new
  ``__classcell__`` namespace entry up to ``type.__new__`` now results in a
  ``DeprecationWarning`` and a class that supports zero-argument
  ``super()``.

- bpo-28797: Modifying the class __dict__ inside the __set_name__ method of
  a descriptor that is used inside that class no longer prevents calling the
  __set_name__ method of other descriptors.

- bpo-28799: Remove the ``PyEval_GetCallStats()`` function and deprecate the
  untested and undocumented ``sys.callstats()`` function. Remove the
  ``CALL_PROFILE`` special build: use the :func:`sys.setprofile` function,
  :mod:`cProfile` or :mod:`profile` to profile function calls.

- bpo-12844: More than 255 arguments can now be passed to a function.

- bpo-28782: Fix a bug in the implementation ``yield from`` when checking if
  the next instruction is YIELD_FROM. Regression introduced by WORDCODE
  (issue #26647).

- bpo-28774: Fix error position of the unicode error in ASCII and Latin1
  encoders when a string returned by the error handler contains multiple
  non-encodable characters (non-ASCII for the ASCII codec, characters out of
  the U+0000-U+00FF range for Latin1).

- bpo-28731: Optimize _PyDict_NewPresized() to create correct size dict.
  Improve speed of dict literal with constant keys up to 30%.

- bpo-28532: Show sys.version when -V option is supplied twice.

- bpo-27100: The with-statement now checks for __enter__ before it checks
  for __exit__. This gives less confusing error messages when both methods
  are missing. Patch by Jonathan Ellington.

- bpo-28746: Fix the set_inheritable() file descriptor method on platforms
  that do not have the ioctl FIOCLEX and FIONCLEX commands.

- bpo-26920: Fix not getting the locale's charset upon initializing the
  interpreter, on platforms that do not have langinfo.

- bpo-28648: Fixed crash in Py_DecodeLocale() in debug build on Mac OS X
  when decode astral characters.  Patch by Xiang Zhang.

- bpo-28665: Improve speed of the STORE_DEREF opcode by 40%.

- bpo-19398: Extra slash no longer added to sys.path components in case of
  empty compile-time PYTHONPATH components.

- bpo-28621: Sped up converting int to float by reusing faster bits counting
  implementation.  Patch by Adrian Wielgosik.

- bpo-28580: Optimize iterating split table values. Patch by Xiang Zhang.

- bpo-28583: PyDict_SetDefault didn't combine split table when needed. Patch
  by Xiang Zhang.

- bpo-28128: Deprecation warning for invalid str and byte escape sequences
  now prints better information about where the error occurs. Patch by
  Serhiy Storchaka and Eric Smith.

- bpo-28509: dict.update() no longer allocate unnecessary large memory.

- bpo-28426: Fixed potential crash in PyUnicode_AsDecodedObject() in debug
  build.

- bpo-28517: Fixed of-by-one error in the peephole optimizer that caused
  keeping unreachable code.

- bpo-28214: Improved exception reporting for problematic __set_name__
  attributes.

- bpo-23782: Fixed possible memory leak in _PyTraceback_Add() and exception
  loss in PyTraceBack_Here().

- bpo-28183: Optimize and cleanup dict iteration.

- bpo-26081: Added C implementation of asyncio.Future. Original patch by
  Yury Selivanov.

- bpo-28379: Added sanity checks and tests for PyUnicode_CopyCharacters().
  Patch by Xiang Zhang.

- bpo-28376: The type of long range iterator is now registered as Iterator.
  Patch by Oren Milman.

- bpo-28376: Creating instances of range_iterator by calling range_iterator
  type now is disallowed.  Calling iter() on range instance is the only way.
  Patch by Oren Milman.

- bpo-26906: Resolving special methods of uninitialized type now causes
  implicit initialization of the type instead of a fail.

- bpo-18287: PyType_Ready() now checks that tp_name is not NULL. Original
  patch by Niklas Koep.

- bpo-24098: Fixed possible crash when AST is changed in process of
  compiling it.

- bpo-28201: Dict reduces possibility of 2nd conflict in hash table when
  hashes have same lower bits.

- bpo-28350: String constants with null character no longer interned.

- bpo-26617: Fix crash when GC runs during weakref callbacks.

- bpo-27942: String constants now interned recursively in tuples and
  frozensets.

- bpo-28289: ImportError.__init__ now resets not specified attributes.

- bpo-21578: Fixed misleading error message when ImportError called with
  invalid keyword args.

- bpo-28203: Fix incorrect type in complex(1.0, {2:3}) error message. Patch
  by Soumya Sharma.

- bpo-28086: Single var-positional argument of tuple subtype was passed
  unscathed to the C-defined function.  Now it is converted to exact tuple.

- bpo-28214: Now __set_name__ is looked up on the class instead of the
  instance.

- bpo-27955: Fallback on reading /dev/urandom device when the getrandom()
  syscall fails with EPERM, for example when blocked by SECCOMP.

- bpo-28192: Don't import readline in isolated mode.

- bpo-27441: Remove some redundant assignments to ob_size in longobject.c.
  Thanks Oren Milman.

- bpo-27222: Clean up redundant code in long_rshift function. Thanks Oren
  Milman.

- Upgrade internal unicode databases to Unicode version 9.0.0.

- bpo-28131: Fix a regression in zipimport's compile_source().  zipimport
  should use the same optimization level as the interpreter.

- bpo-28126: Replace Py_MEMCPY with memcpy(). Visual Studio can properly
  optimize memcpy().

- bpo-28120: Fix dict.pop() for splitted dictionary when trying to remove a
  "pending key" (Not yet inserted in split-table). Patch by Xiang Zhang.

- bpo-26182: Raise DeprecationWarning when async and await keywords are used
  as variable/attribute/class/function name.

- bpo-26182: Fix a refleak in code that raises DeprecationWarning.

- bpo-28721: Fix asynchronous generators aclose() and athrow() to handle
  StopAsyncIteration propagation properly.

- bpo-26110: Speed-up method calls: add LOAD_METHOD and CALL_METHOD opcodes.

Library
-------

- bpo-31499: xml.etree: Fix a crash when a parser is part of a reference
  cycle.

- bpo-31482: ``random.seed()`` now works with bytes in version=1

- bpo-28556: typing.get_type_hints now finds the right globalns for classes
  and modules by default (when no ``globalns`` was specified by the caller).

- bpo-28556: Speed improvements to the ``typing`` module.  Original PRs by
  Ivan Levkivskyi and Mitar.

- bpo-31544: The C accelerator module of ElementTree ignored exceptions
  raised when looking up TreeBuilder target methods in XMLParser().

- bpo-31234: socket.create_connection() now fixes manually a reference
  cycle: clear the variable storing the last exception on success.

- bpo-31457: LoggerAdapter objects can now be nested.

- bpo-31431: SSLContext.check_hostname now automatically sets
  SSLContext.verify_mode to ssl.CERT_REQUIRED instead of failing with a
  ValueError.

- bpo-31233: socketserver.ThreadingMixIn now keeps a list of non-daemonic
  threads to wait until all these threads complete in server_close().

- bpo-28638: Changed the implementation strategy for
  collections.namedtuple() to substantially reduce the use of exec() in
  favor of precomputed methods. As a result, the *verbose* parameter and
  *_source* attribute are no longer supported.  The benefits include 1)
  having a smaller memory footprint for applications using multiple named
  tuples, 2) faster creation of the named tuple class (approx 4x to 6x
  depending on how it is measured), and 3) minor speed-ups for instance
  creation using __new__, _make, and _replace.  (The primary patch
  contributor is Jelle Zijlstra with further improvements by INADA Naoki,
  Serhiy Storchaka, and Raymond Hettinger.)

- bpo-31400: Improves SSL error handling to avoid losing error numbers.

- bpo-27629: Make return types of SSLContext.wrap_bio() and
  SSLContext.wrap_socket() customizable.

- bpo-28958: ssl.SSLContext() now uses OpenSSL error information when a
  context cannot be instantiated.

- bpo-28182: The SSL module now raises SSLCertVerificationError when OpenSSL
  fails to verify the peer's certificate. The exception contains more
  information about the error.

- bpo-27340: SSLSocket.sendall() now uses memoryview to create slices of
  data. This fixes support for all bytes-like object. It is also more
  efficient and avoids costly copies.

- bpo-14191: A new function
  ``argparse.ArgumentParser.parse_intermixed_args`` provides the ability to
  parse command lines where there user intermixes options and positional
  arguments.

- bpo-31178: Fix string concatenation bug in rare error path in the
  subprocess module

- bpo-31350: Micro-optimize :func:`asyncio._get_running_loop` to become up
  to 10% faster.

- bpo-31170: expat: Update libexpat from 2.2.3 to 2.2.4. Fix copying of
  partial characters for UTF-8 input (libexpat bug 115):
  https://github.com/libexpat/libexpat/issues/115

- bpo-29136: Add TLS 1.3 cipher suites and OP_NO_TLSv1_3.

- bpo-1198569: ``string.Template`` subclasses can optionally define
  ``braceidpattern`` if they want to specify different placeholder patterns
  inside and outside the braces.  If None (the default) it falls back to
  ``idpattern``.

- bpo-31326: concurrent.futures.ProcessPoolExecutor.shutdown() now
  explicitly closes the call queue. Moreover, shutdown(wait=True) now also
  join the call queue thread, to prevent leaking a dangling thread.

- bpo-27144: The ``map()`` and ``as_completed()`` iterators in
  ``concurrent.futures`` now avoid keeping a reference to yielded objects.

- bpo-31281: Fix ``fileinput.FileInput(files, inplace=True)`` when ``files``
  contain ``pathlib.Path`` objects.

- bpo-10746: Fix ctypes producing wrong :pep:`3118` type codes for integer
  types.

- bpo-27584: ``AF_VSOCK`` has been added to the socket interface which
  allows communication between virtual machines and their host.

- bpo-22536: The subprocess module now sets the filename when
  FileNotFoundError is raised on POSIX systems due to the executable or cwd
  not being found.

- bpo-29741: Update some methods in the _pyio module to also accept integer
  types. Patch by Oren Milman.

- bpo-31249: concurrent.futures: WorkItem.run() used by ThreadPoolExecutor
  now breaks a reference cycle between an exception object and the WorkItem
  object.

- bpo-31247: xmlrpc.server now explicitly breaks reference cycles when using
  sys.exc_info() in code handling exceptions.

- bpo-23835: configparser: reading defaults in the ``ConfigParser()``
  constructor is now using ``read_dict()``, making its behavior consistent
  with the rest of the parser.  Non-string keys and values in the defaults
  dictionary are now being implicitly converted to strings.  Patch by James
  Tocknell.

- bpo-31238: pydoc: the stop() method of the private ServerThread class now
  waits until DocServer.serve_until_quit() completes and then explicitly
  sets its docserver attribute to None to break a reference cycle.

- bpo-5001: Many asserts in `multiprocessing` are now more informative, and
  some error types have been changed to more specific ones.

- bpo-31109: Convert zipimport to use Argument Clinic.

- bpo-30102: The ssl and hashlib modules now call
  OPENSSL_add_all_algorithms_noconf() on OpenSSL < 1.1.0. The function
  detects CPU features and enables optimizations on some CPU architectures
  such as POWER8. Patch is based on research from Gustavo Serra Scalet.

- bpo-18966: Non-daemonic threads created by a multiprocessing.Process are
  now joined on child exit.

- bpo-31183: `dis` now works with asynchronous generator and coroutine
  objects. Patch by George Collins based on diagnosis by Luciano Ramalho.

- bpo-5001: There are a number of uninformative asserts in the
  `multiprocessing` module, as noted in issue 5001. This change fixes two of
  the most potentially problematic ones, since they are in error-reporting
  code, in the `multiprocessing.managers.convert_to_error` function. (It
  also makes more informative a ValueError message.) The only potentially
  problematic change is that the AssertionError is now a TypeError; however,
  this should also help distinguish it from an AssertionError being
  *reported* by the function/its caller (such as in issue 31169). - Patch by
  Allen W. Smith (drallensmith on github).

- bpo-31185: Fixed miscellaneous errors in asyncio speedup module.

- bpo-31151: socketserver.ForkingMixIn.server_close() now waits until all
  child processes completed to prevent leaking zombie processes.

- bpo-31072: Add an ``include_file`` parameter to
  ``zipapp.create_archive()``

- bpo-24700: Optimize array.array comparison. It is now from 10x up to 70x
  faster when comparing arrays holding values of the same integer type.

- bpo-31135: ttk: fix the destroy() method of LabeledScale and OptionMenu
  classes. Call the parent destroy() method even if the used attribute
  doesn't exist. The LabeledScale.destroy() method now also explicitly
  clears label and scale attributes to help the garbage collector to destroy
  all widgets.

- bpo-31107: Fix `copyreg._slotnames()` mangled attribute calculation for
  classes whose name begins with an underscore. Patch by Shane Harvey.

- bpo-31080: Allow `logging.config.fileConfig` to accept kwargs and/or args.

- bpo-30897: ``pathlib.Path`` objects now include an ``is_mount()`` method
  (only implemented on POSIX).  This is similar to ``os.path.ismount(p)``.
  Patch by Cooper Ry Lees.

- bpo-31061: Fixed a crash when using asyncio and threads.

- bpo-30987: Added support for CAN ISO-TP protocol in the socket module.

- bpo-30522: Added a ``setStream`` method to ``logging.StreamHandler`` to
  allow the stream to be set after creation.

- bpo-30502: Fix handling of long oids in ssl.  Based on patch by Christian
  Heimes.

- bpo-5288: Support tzinfo objects with sub-minute offsets.

- bpo-30919: Fix shared memory performance regression in multiprocessing in
  3.x. Shared memory used anonymous memory mappings in 2.x, while 3.x mmaps
  actual files. Try to be careful to do as little disk I/O as possible.

- bpo-26732: Fix too many fds in processes started with the "forkserver"
  method. A child process would inherit as many fds as the number of
  still-running children.

- bpo-29403: Fix ``unittest.mock``'s autospec to not fail on method-bound
  builtin functions.  Patch by Aaron Gallagher.

- bpo-30961: Fix decrementing a borrowed reference in tracemalloc.

- bpo-19896: Fix multiprocessing.sharedctypes to recognize typecodes ``'q'``
  and ``'Q'``.

- bpo-30946: Remove obsolete code in readline module for platforms where GNU
  readline is older than 2.1 or where select() is not available.

- bpo-25684: Change ``ttk.OptionMenu`` radiobuttons to be unique across
  instances of ``OptionMenu``.

- bpo-30886: Fix multiprocessing.Queue.join_thread(): it now waits until the
  thread completes, even if the thread was started by the same process which
  created the queue.

- bpo-29854: Fix segfault in readline when using readline's history-size
  option.  Patch by Nir Soffer.

- bpo-30794: Added multiprocessing.Process.kill method to terminate using
  the SIGKILL signal on Unix.

- bpo-30319: socket.close() now ignores ECONNRESET error.

- bpo-30828: Fix out of bounds write in
  `asyncio.CFuture.remove_done_callback()`.

- bpo-30302: Use keywords in the ``repr`` of ``datetime.timedelta``.

- bpo-30807: signal.setitimer() may disable the timer when passed a tiny
  value. Tiny values (such as 1e-6) are valid non-zero values for
  setitimer(), which is specified as taking microsecond-resolution
  intervals. However, on some platform, our conversion routine could convert
  1e-6 into a zero interval, therefore disabling the timer instead of
  (re-)scheduling it.

- bpo-30441: Fix bug when modifying os.environ while iterating over it

- bpo-29585: Avoid importing ``sysconfig`` from ``site`` to improve startup
  speed. Python startup is about 5% faster on Linux and 30% faster on macOS.

- bpo-29293: Add missing parameter "n" on
  multiprocessing.Condition.notify(). The doc claims
  multiprocessing.Condition behaves like threading.Condition, but its
  notify() method lacked the optional "n" argument (to specify the number of
  sleepers to wake up) that threading.Condition.notify() accepts.

- bpo-30532: Fix email header value parser dropping folding white space in
  certain cases.

- bpo-30596: Add a ``close()`` method to ``multiprocessing.Process``.

- bpo-9146: Fix a segmentation fault in _hashopenssl when standard hash
  functions such as md5 are not available in the linked OpenSSL library.  As
  in some special FIPS-140 build environments.

- bpo-29169: Update zlib to 1.2.11.

- bpo-30119: ftplib.FTP.putline() now throws ValueError on commands that
  contains CR or LF. Patch by Dong-hee Na.

- bpo-30879: os.listdir() and os.scandir() now emit bytes names when called
  with bytes-like argument.

- bpo-30746: Prohibited the '=' character in environment variable names in
  ``os.putenv()`` and ``os.spawn*()``.

- bpo-30664: The description of a unittest subtest now preserves the order
  of keyword arguments of TestCase.subTest().

- bpo-21071: struct.Struct.format type is now :class:`str` instead of
  :class:`bytes`.

- bpo-29212: Fix concurrent.futures.thread.ThreadPoolExecutor threads to
  have a non repr() based thread name by default when no thread_name_prefix
  is supplied. They will now identify themselves as
  "ThreadPoolExecutor-y_n".

- bpo-29755: Fixed the lgettext() family of functions in the gettext module.
  They now always return bytes.

- bpo-30616: Functional API of enum allows to create empty enums. Patched by
  Dong-hee Na

- bpo-30038: Fix race condition between signal delivery and wakeup file
  descriptor. Patch by Nathaniel Smith.

- bpo-23894: lib2to3 now recognizes ``rb'...'`` and ``f'...'`` strings.

- bpo-24744: pkgutil.walk_packages function now raises ValueError if *path*
  is a string. Patch by Sanyam Khurana.

- bpo-24484: Avoid race condition in multiprocessing cleanup.

- bpo-30589: Fix multiprocessing.Process.exitcode to return the opposite of
  the signal number when the process is killed by a signal (instead of 255)
  when using the "forkserver" method.

- bpo-28994: The traceback no longer displayed for SystemExit raised in a
  callback registered by atexit.

- bpo-30508: Don't log exceptions if Task/Future "cancel()" method was
  called.

- bpo-30645: Fix path calculation in `imp.load_package()`, fixing it for
  cases when a package is only shipped with bytecodes. Patch by Alexandru
  Ardelean.

- bpo-11822: The dis.dis() function now is able to disassemble nested code
  objects.

- bpo-30624: selectors does not take KeyboardInterrupt and SystemExit into
  account, leaving a fd in a bad state in case of error. Patch by Giampaolo
  Rodola'.

- bpo-30595: multiprocessing.Queue.get() with a timeout now polls its reader
  in non-blocking mode if it succeeded to acquire the lock but the acquire
  took longer than the timeout.

- bpo-28556: Updates to typing module: Add generic AsyncContextManager, add
  support for ContextManager on all versions. Original PRs by Jelle Zijlstra
  and Ivan Levkivskyi

- bpo-30605: re.compile() no longer raises a BytesWarning when compiling a
  bytes instance with misplaced inline modifier.  Patch by Roy Williams.

- bpo-29870: Fix ssl sockets leaks when connection is aborted in asyncio/ssl
  implementation. Patch by Michaël Sghaïer.

- bpo-29743: Closing transport during handshake process leaks open socket.
  Patch by Nikolay Kim

- bpo-27585: Fix waiter cancellation in asyncio.Lock. Patch by Mathieu
  Sornay.

- bpo-30014: modify() method of poll(), epoll() and devpoll() based classes
  of selectors module is around 10% faster.  Patch by Giampaolo Rodola'.

- bpo-30418: On Windows, subprocess.Popen.communicate() now also ignore
  EINVAL on stdin.write() if the child process is still running but closed
  the pipe.

- bpo-30463: Addded empty __slots__ to abc.ABC.  This allows subclassers to
  deny __dict__ and __weakref__ creation.  Patch by Aaron Hall.

- bpo-30520: Loggers are now pickleable.

- bpo-30557: faulthandler now correctly filters and displays exception codes
  on Windows

- bpo-30526: Add TextIOWrapper.reconfigure() and a
  TextIOWrapper.write_through attribute.

- bpo-30245: Fix possible overflow when organize struct.pack_into error
  message.  Patch by Yuan Liu.

- bpo-30378: Fix the problem that logging.handlers.SysLogHandler cannot
  handle IPv6 addresses.

- bpo-16500: Allow registering at-fork handlers.

- bpo-30470: Deprecate invalid ctypes call protection on Windows.  Patch by
  Mariatta Wijaya.

- bpo-30414: multiprocessing.Queue._feed background running thread do not
  break from main loop on exception.

- bpo-30003: Fix handling escape characters in HZ codec.  Based on patch by
  Ma Lin.

- bpo-30149: inspect.signature() now supports callables with
  variable-argument parameters wrapped with partialmethod. Patch by Dong-hee
  Na.

- bpo-30436: importlib.find_spec() raises ModuleNotFoundError instead of
  AttributeError if the specified parent module is not a package (i.e. lacks
  a __path__ attribute).

- bpo-30301: Fix AttributeError when using SimpleQueue.empty() under *spawn*
  and *forkserver* start methods.

- bpo-30375: Warnings emitted when compile a regular expression now always
  point to the line in the user code.  Previously they could point into
  inners of the re module if emitted from inside of groups or conditionals.

- bpo-30329: imaplib and poplib now catch the Windows socket WSAEINVAL error
  (code 10022) on shutdown(SHUT_RDWR): An invalid operation was attempted.
  This error occurs sometimes on SSL connections.

- bpo-29196: Removed previously deprecated in Python 2.4 classes Plist, Dict
  and _InternalDict in the plistlib module.  Dict values in the result of
  functions readPlist() and readPlistFromBytes() are now normal dicts.  You
  no longer can use attribute access to access items of these dictionaries.

- bpo-9850: The :mod:`macpath` is now deprecated and will be removed in
  Python 3.8.

- bpo-30299: Compiling regular expression in debug mode on CPython now
  displays the compiled bytecode in human readable form.

- bpo-30048: Fixed ``Task.cancel()`` can be ignored when the task is running
  coroutine and the coroutine returned without any more ``await``.

- bpo-30266: contextlib.AbstractContextManager now supports
  anti-registration by setting __enter__ = None or __exit__ = None,
  following the pattern introduced in bpo-25958. Patch by Jelle Zijlstra.

- bpo-30340: Enhanced regular expressions optimization. This increased the
  performance of matching some patterns up to 25 times.

- bpo-30298: Weaken the condition of deprecation warnings for inline
  modifiers. Now allowed several subsequential inline modifiers at the start
  of the pattern (e.g. ``'(?i)(?s)...'``).  In verbose mode whitespaces and
  comments now are allowed before and between inline modifiers (e.g. ``'(?x)
  (?i) (?s)...'``).

- bpo-30285: Optimized case-insensitive matching and searching of regular
  expressions.

- bpo-29990: Fix range checking in GB18030 decoder.  Original patch by Ma
  Lin.

- bpo-29979: rewrite cgi.parse_multipart, reusing the FieldStorage class and
  making its results consistent with those of FieldStorage for
  multipart/form-data requests. Patch by Pierre Quentel.

- bpo-30243: Removed the __init__ methods of _json's scanner and encoder.
  Misusing them could cause memory leaks or crashes.  Now scanner and
  encoder objects are completely initialized in the __new__ methods.

- bpo-30215: Compiled regular expression objects with the re.LOCALE flag no
  longer depend on the locale at compile time.  Only the locale at matching
  time affects the result of matching.

- bpo-30185: Avoid KeyboardInterrupt tracebacks in forkserver helper process
  when Ctrl-C is received.

- bpo-30103: binascii.b2a_uu() and uu.encode() now support using ``'`'`` as
  zero instead of space.

- bpo-28556: Various updates to typing module: add typing.NoReturn type, use
  WrapperDescriptorType, minor bug-fixes.  Original PRs by Jim
  Fasarakis-Hilliard and Ivan Levkivskyi.

- bpo-30205: Fix getsockname() for unbound AF_UNIX sockets on Linux.

- bpo-30228: The seek() and tell() methods of io.FileIO now set the internal
  seekable attribute to avoid one syscall on open() (in buffered or text
  mode).

- bpo-30190: unittest's assertAlmostEqual and assertNotAlmostEqual provide a
  better message in case of failure which includes the difference between
  left and right arguments.  (patch by Giampaolo Rodola')

- bpo-30101: Add support for curses.A_ITALIC.

- bpo-29822: inspect.isabstract() now works during __init_subclass__.  Patch
  by Nate Soares.

- bpo-29960: Preserve generator state when _random.Random.setstate() raises
  an exception. Patch by Bryan Olson.

- bpo-30070: Fixed leaks and crashes in errors handling in the parser
  module.

- bpo-22352: Column widths in the output of dis.dis() are now adjusted for
  large line numbers and instruction offsets.

- bpo-30061: Fixed crashes in IOBase methods __next__() and readlines() when
  readline() or __next__() respectively return non-sizeable object. Fixed
  possible other errors caused by not checking results of PyObject_Size(),
  PySequence_Size(), or PyMapping_Size().

- bpo-30218: Fix PathLike support for shutil.unpack_archive. Patch by Jelle
  Zijlstra.

- bpo-10076: Compiled regular expression and match objects in the re module
  now support copy.copy() and copy.deepcopy() (they are considered atomic).

- bpo-30068: _io._IOBase.readlines will check if it's closed first when hint
  is present.

- bpo-29694: Fixed race condition in pathlib mkdir with flags parents=True.
  Patch by Armin Rigo.

- bpo-29692: Fixed arbitrary unchaining of RuntimeError exceptions in
  contextlib.contextmanager.  Patch by Siddharth Velankar.

- bpo-26187: Test that sqlite3 trace callback is not called multiple times
  when schema is changing.  Indirectly fixed by switching to use
  sqlite3_prepare_v2() in bpo-9303.  Patch by Aviv Palivoda.

- bpo-30017: Allowed calling the close() method of the zip entry writer
  object multiple times.  Writing to a closed writer now always produces a
  ValueError.

- bpo-29998: Pickling and copying ImportError now preserves name and path
  attributes.

- bpo-29995: re.escape() now escapes only regex special characters.

- bpo-29962: Add math.remainder operation, implementing remainder as
  specified in IEEE 754.

- bpo-29649: Improve struct.pack_into() exception messages for problems with
  the buffer size and offset.  Patch by Andrew Nester.

- bpo-29654: Support If-Modified-Since HTTP header (browser cache).  Patch
  by Pierre Quentel.

- bpo-29931: Fixed comparison check for ipaddress.ip_interface objects.
  Patch by Sanjay Sundaresan.

- bpo-29953: Fixed memory leaks in the replace() method of datetime and time
  objects when pass out of bound fold argument.

- bpo-29942: Fix a crash in itertools.chain.from_iterable when encountering
  long runs of empty iterables.

- bpo-10030: Sped up reading encrypted ZIP files by 2 times.

- bpo-29204: Element.getiterator() and the html parameter of XMLParser()
  were deprecated only in the documentation (since Python 3.2 and 3.4
  correspondingly). Now using them emits a deprecation warning.

- bpo-27863: Fixed multiple crashes in ElementTree caused by race conditions
  and wrong types.

- bpo-25996: Added support of file descriptors in os.scandir() on Unix.
  os.fwalk() is sped up by 2 times by using os.scandir().

- bpo-28699: Fixed a bug in pools in multiprocessing.pool that raising an
  exception at the very first of an iterable may swallow the exception or
  make the program hang. Patch by Davin Potts and Xiang Zhang.

- bpo-23890: unittest.TestCase.assertRaises() now manually breaks a
  reference cycle to not keep objects alive longer than expected.

- bpo-29901: The zipapp module now supports general path-like objects, not
  just pathlib.Path.

- bpo-25803: Avoid incorrect errors raised by Path.mkdir(exist_ok=True) when
  the OS gives priority to errors such as EACCES over EEXIST.

- bpo-29861: Release references to tasks, their arguments and their results
  as soon as they are finished in multiprocessing.Pool.

- bpo-19930: The mode argument of os.makedirs() no longer affects the file
  permission bits of newly-created intermediate-level directories.

- bpo-29884: faulthandler: Restore the old sigaltstack during teardown.
  Patch by Christophe Zeitouny.

- bpo-25455: Fixed crashes in repr of recursive buffered file-like objects.

- bpo-29800: Fix crashes in partial.__repr__ if the keys of partial.keywords
  are not strings.  Patch by Michael Seifert.

- bpo-8256: Fixed possible failing or crashing input() if attributes
  "encoding" or "errors" of sys.stdin or sys.stdout are not set or are not
  strings.

- bpo-28692: Using non-integer value for selecting a plural form in gettext
  is now deprecated.

- bpo-26121: Use C library implementation for math functions erf() and
  erfc().

- bpo-29619: os.stat() and os.DirEntry.inode() now convert inode (st_ino)
  using unsigned integers.

- bpo-28298: Fix a bug that prevented array 'Q', 'L' and 'I' from accepting
  big intables (objects that have __int__) as elements.

- bpo-29645: Speed up importing the webbrowser module.
  webbrowser.register() is now thread-safe.

- bpo-28231: The zipfile module now accepts path-like objects for external
  paths.

- bpo-26915: index() and count() methods of collections.abc.Sequence now
  check identity before checking equality when do comparisons.

- bpo-28682: Added support for bytes paths in os.fwalk().

- bpo-29728: Add new :data:`socket.TCP_NOTSENT_LOWAT` (Linux 3.12) constant.
  Patch by Nathaniel J. Smith.

- bpo-29623: Allow use of path-like object as a single argument in
  ConfigParser.read(). Patch by David Ellis.

- bpo-9303: Migrate sqlite3 module to _v2 API.  Patch by Aviv Palivoda.

- bpo-28963: Fix out of bound iteration in
  asyncio.Future.remove_done_callback implemented in C.

- bpo-29704: asyncio.subprocess.SubprocessStreamProtocol no longer closes
  before all pipes are closed.

- bpo-29271: Fix Task.current_task and Task.all_tasks implemented in C to
  accept None argument as their pure Python implementation.

- bpo-29703: Fix asyncio to support instantiation of new event loops in
  child processes.

- bpo-29615: SimpleXMLRPCDispatcher no longer chains KeyError (or any other
  exception) to exception(s) raised in the dispatched methods. Patch by Petr
  Motejlek.

- bpo-7769: Method register_function() of
  xmlrpc.server.SimpleXMLRPCDispatcher and its subclasses can now be used as
  a decorator.

- bpo-29376: Fix assertion error in threading._DummyThread.is_alive().

- bpo-28624: Add a test that checks that cwd parameter of Popen() accepts
  PathLike objects.  Patch by Sayan Chowdhury.

- bpo-28518: Start a transaction implicitly before a DML statement. Patch by
  Aviv Palivoda.

- bpo-29742: get_extra_info() raises exception if get called on closed ssl
  transport. Patch by Nikolay Kim.

- bpo-16285: urllib.parse.quote is now based on RFC 3986 and hence includes
  '~' in the set of characters that is not quoted by default. Patch by
  Christian Theune and Ratnadeep Debnath.

- bpo-29532: Altering a kwarg dictionary passed to functools.partial() no
  longer affects a partial object after creation.

- bpo-29110: Fix file object leak in aifc.open() when file is given as a
  filesystem path and is not in valid AIFF format. Patch by Anthony Zhang.

- bpo-22807: Add uuid.SafeUUID and uuid.UUID.is_safe to relay information
  from the platform about whether generated UUIDs are generated with a
  multiprocessing safe method.

- bpo-29576: Improve some deprecations in importlib. Some deprecated methods
  now emit DeprecationWarnings and have better descriptive messages.

- bpo-29534: Fixed different behaviour of Decimal.from_float() for _decimal
  and _pydecimal. Thanks Andrew Nester.

- bpo-10379: locale.format_string now supports the 'monetary' keyword
  argument, and locale.format is deprecated.

- bpo-29851: importlib.reload() now raises ModuleNotFoundError if the module
  lacks a spec.

- bpo-28556: Various updates to typing module: typing.Counter,
  typing.ChainMap, improved ABC caching, etc. Original PRs by Jelle
  Zijlstra, Ivan Levkivskyi, Manuel Krebber, and Łukasz Langa.

- bpo-29100: Fix datetime.fromtimestamp() regression introduced in Python
  3.6.0: check minimum and maximum years.

- bpo-29416: Prevent infinite loop in pathlib.Path.mkdir

- bpo-29444: Fixed out-of-bounds buffer access in the group() method of the
  match object. Based on patch by WGH.

- bpo-29377: Add WrapperDescriptorType, MethodWrapperType, and
  MethodDescriptorType built-in types to types module. Original patch by
  Manuel Krebber.

- bpo-29218: Unused install_misc command is now removed.  It has been
  documented as unused since 2000.  Patch by Eric N. Vander Weele.

- bpo-29368: The extend() method is now called instead of the append()
  method when unpickle collections.deque and other list-like objects. This
  can speed up unpickling to 2 times.

- bpo-29338: The help of a builtin or extension class now includes the
  constructor signature if __text_signature__ is provided for the class.

- bpo-29335: Fix subprocess.Popen.wait() when the child process has exited
  to a stopped instead of terminated state (ex: when under ptrace).

- bpo-29290: Fix a regression in argparse that help messages would wrap at
  non-breaking spaces.

- bpo-28735: Fixed the comparison of mock.MagickMock with mock.ANY.

- bpo-29197: Removed deprecated function ntpath.splitunc().

- bpo-29210: Removed support of deprecated argument "exclude" in
  tarfile.TarFile.add().

- bpo-29219: Fixed infinite recursion in the repr of uninitialized
  ctypes.CDLL instances.

- bpo-29192: Removed deprecated features in the http.cookies module.

- bpo-29193: A format string argument for string.Formatter.format() is now
  positional-only.

- bpo-29195: Removed support of deprecated undocumented keyword arguments in
  methods of regular expression objects.

- bpo-28969: Fixed race condition in C implementation of
  functools.lru_cache. KeyError could be raised when cached function with
  full cache was simultaneously called from different threads with the same
  uncached arguments.

- bpo-20804: The unittest.mock.sentinel attributes now preserve their
  identity when they are copied or pickled.

- bpo-29142: In urllib.request, suffixes in no_proxy environment variable
  with leading dots could match related hostnames again (e.g. .b.c matches
  a.b.c). Patch by Milan Oberkirch.

- bpo-28961: Fix unittest.mock._Call helper: don't ignore the name parameter
  anymore. Patch written by Jiajun Huang.

- bpo-15812: inspect.getframeinfo() now correctly shows the first line of a
  context. Patch by Sam Breese.

- bpo-28985: Update authorizer constants in sqlite3 module. Patch by
  Dingyuan Wang.

- bpo-29079: Prevent infinite loop in pathlib.resolve() on Windows

- bpo-13051: Fixed recursion errors in large or resized
  curses.textpad.Textbox.  Based on patch by Tycho Andersen.

- bpo-9770: curses.ascii predicates now work correctly with negative
  integers.

- bpo-28427: old keys should not remove new values from WeakValueDictionary
  when collecting from another thread.

- bpo-28923: Remove editor artifacts from Tix.py.

- bpo-28871: Fixed a crash when deallocate deep ElementTree.

- bpo-19542: Fix bugs in WeakValueDictionary.setdefault() and
  WeakValueDictionary.pop() when a GC collection happens in another thread.

- bpo-20191: Fixed a crash in resource.prlimit() when passing a sequence
  that doesn't own its elements as limits.

- bpo-16255: subprocess.Popen uses /system/bin/sh on Android as the shell,
  instead of /bin/sh.

- bpo-28779: multiprocessing.set_forkserver_preload() would crash the
  forkserver process if a preloaded module instantiated some multiprocessing
  objects such as locks.

- bpo-26937: The chown() method of the tarfile.TarFile class does not fail
  now when the grp module cannot be imported, as for example on Android
  platforms.

- bpo-28847: dbm.dumb now supports reading read-only files and no longer
  writes the index file when it is not changed.  A deprecation warning is
  now emitted if the index file is missed and recreated in the 'r' and 'w'
  modes (will be an error in future Python releases).

- bpo-27030: Unknown escapes consisting of ``'\'`` and an ASCII letter in
  re.sub() replacement templates regular expressions now are errors.

- bpo-28835: Fix a regression introduced in warnings.catch_warnings(): call
  warnings.showwarning() if it was overridden inside the context manager.

- bpo-27172: To assist with upgrades from 2.7, the previously documented
  deprecation of ``inspect.getfullargspec()`` has been reversed. This
  decision may be revisited again after the Python 2.7 branch is no longer
  officially supported.

- bpo-28740: Add sys.getandroidapilevel(): return the build time API version
  of Android as an integer. Function only available on Android.

- bpo-26273: Add new :data:`socket.TCP_CONGESTION` (Linux 2.6.13) and
  :data:`socket.TCP_USER_TIMEOUT` (Linux 2.6.37) constants. Patch written by
  Omar Sandoval.

- bpo-28752: Restored the __reduce__() methods of datetime objects.

- bpo-28727: Regular expression patterns, _sre.SRE_Pattern objects created
  by re.compile(), become comparable (only x==y and x!=y operators). This
  change should fix the issue #18383: don't duplicate warning filters when
  the warnings module is reloaded (thing usually only done in unit tests).

- bpo-20572: Remove the subprocess.Popen.wait endtime parameter.  It was
  deprecated in 3.4 and undocumented prior to that.

- bpo-25659: In ctypes, prevent a crash calling the from_buffer() and
  from_buffer_copy() methods on abstract classes like Array.

- bpo-28548: In the "http.server" module, parse the protocol version if
  possible, to avoid using HTTP 0.9 in some error responses.

- bpo-19717: Makes Path.resolve() succeed on paths that do not exist. Patch
  by Vajrasky Kok

- bpo-28563: Fixed possible DoS and arbitrary code execution when handle
  plural form selections in the gettext module.  The expression parser now
  supports exact syntax supported by GNU gettext.

- bpo-28387: Fixed possible crash in _io.TextIOWrapper deallocator when the
  garbage collector is invoked in other thread.  Based on patch by Sebastian
  Cufre.

- bpo-27517: LZMA compressor and decompressor no longer raise exceptions if
  given empty data twice.  Patch by Benjamin Fogle.

- bpo-28549: Fixed segfault in curses's addch() with ncurses6.

- bpo-28449: tarfile.open() with mode "r" or "r:" now tries to open a tar
  file with compression before trying to open it without compression.
  Otherwise it had 50% chance failed with ignore_zeros=True.

- bpo-23262: The webbrowser module now supports Firefox 36+ and derived
  browsers.  Based on patch by Oleg Broytman.

- bpo-24241: The webbrowser in an X environment now prefers using the
  default browser directly. Also, the webbrowser register() function now has
  a documented 'preferred' argument, to specify browsers to be returned by
  get() with no arguments. Patch by David Steele

- bpo-27939: Fixed bugs in tkinter.ttk.LabeledScale and tkinter.Scale caused
  by representing the scale as float value internally in Tk.  tkinter.IntVar
  now works if float value is set to underlying Tk variable.

- bpo-28255: calendar.TextCalendar.prweek() no longer prints a space after a
  weeks's calendar.  calendar.TextCalendar.pryear() no longer prints
  redundant newline after a year's calendar.  Based on patch by Xiang Zhang.

- bpo-28255: calendar.TextCalendar.prmonth() no longer prints a space at the
  start of new line after printing a month's calendar.  Patch by Xiang
  Zhang.

- bpo-20491: The textwrap.TextWrapper class now honors non-breaking spaces.
  Based on patch by Kaarle Ritvanen.

- bpo-28353: os.fwalk() no longer fails on broken links.

- bpo-28430: Fix iterator of C implemented asyncio.Future doesn't accept
  non-None value is passed to it.send(val).

- bpo-27025: Generated names for Tkinter widgets now start by the "!" prefix
  for readability.

- bpo-25464: Fixed HList.header_exists() in tkinter.tix module by addin a
  workaround to Tix library bug.

- bpo-28488: shutil.make_archive() no longer adds entry "./" to ZIP archive.

- bpo-25953: re.sub() now raises an error for invalid numerical group
  reference in replacement template even if the pattern is not found in the
  string.  Error message for invalid group reference now includes the group
  index and the position of the reference. Based on patch by SilentGhost.

- bpo-28469: timeit now uses the sequence 1, 2, 5, 10, 20, 50,... instead of
  1, 10, 100,... for autoranging.

- bpo-28115: Command-line interface of the zipfile module now uses argparse.
  Added support of long options.

- bpo-18219: Optimize csv.DictWriter for large number of columns. Patch by
  Mariatta Wijaya.

- bpo-28448: Fix C implemented asyncio.Future didn't work on Windows.

- bpo-23214: In the "io" module, the argument to BufferedReader and
  BytesIO's read1() methods is now optional and can be -1, matching the
  BufferedIOBase specification.

- bpo-28480: Fix error building socket module when multithreading is
  disabled.

- bpo-28240: timeit: remove ``-c/--clock`` and ``-t/--time`` command line
  options which were deprecated since Python 3.3.

- bpo-28240: timeit now repeats the benchmarks 5 times instead of only 3 to
  make benchmarks more reliable.

- bpo-28240: timeit autorange now uses a single loop iteration if the
  benchmark takes less than 10 seconds, instead of 10 iterations. "python3
  -m timeit -s 'import time' 'time.sleep(1)'" now takes 4 seconds instead of
  40 seconds.

- Distutils.sdist now looks for README and setup.py files with case
  sensitivity. This behavior matches that found in Setuptools 6.0 and later.
  See `setuptools 100 <https://github.com/pypa/setuptools/issues/100>`_ for
  rationale.

- bpo-24452: Make webbrowser support Chrome on Mac OS X. Patch by Ned
  Batchelder.

- bpo-20766: Fix references leaked by pdb in the handling of SIGINT
  handlers.

- bpo-27998: Fixed bytes path support in os.scandir() on Windows. Patch by
  Eryk Sun.

- bpo-28317: The disassembler now decodes FORMAT_VALUE argument.

- bpo-28380: unittest.mock Mock autospec functions now properly support
  assert_called, assert_not_called, and assert_called_once.

- bpo-28229: lzma module now supports pathlib.

- bpo-28321: Fixed writing non-BMP characters with binary format in
  plistlib.

- bpo-28225: bz2 module now supports pathlib.  Initial patch by Ethan
  Furman.

- bpo-28227: gzip now supports pathlib.  Patch by Ethan Furman.

- bpo-28332: Deprecated silent truncations in socket.htons and socket.ntohs.
  Original patch by Oren Milman.

- bpo-27358: Optimized merging var-keyword arguments and improved error
  message when passing a non-mapping as a var-keyword argument.

- bpo-28257: Improved error message when passing a non-iterable as a
  var-positional argument.  Added opcode BUILD_TUPLE_UNPACK_WITH_CALL.

- bpo-28322: Fixed possible crashes when unpickle itertools objects from
  incorrect pickle data.  Based on patch by John Leitch.

- bpo-28228: imghdr now supports pathlib.

- bpo-28226: compileall now supports pathlib.

- bpo-28314: Fix function declaration (C flags) for the getiterator() method
  of xml.etree.ElementTree.Element.

- bpo-28148: Stop using localtime() and gmtime() in the time module.
  Introduced platform independent _PyTime_localtime API that is similar to
  POSIX localtime_r, but available on all platforms.  Patch by Ed Schouten.

- bpo-28253: Fixed calendar functions for extreme months: 0001-01 and
  9999-12. Methods itermonthdays() and itermonthdays2() are reimplemented so
  that they don't call itermonthdates() which can cause datetime.date
  under/overflow.

- bpo-28275: Fixed possible use after free in the decompress() methods of
  the LZMADecompressor and BZ2Decompressor classes. Original patch by John
  Leitch.

- bpo-27897: Fixed possible crash in sqlite3.Connection.create_collation()
  if pass invalid string-like object as a name.  Patch by Xiang Zhang.

- bpo-18844: random.choices() now has k as a keyword-only argument to
  improve the readability of common cases and come into line with the
  signature used in other languages.

- bpo-18893: Fix invalid exception handling in Lib/ctypes/macholib/dyld.py.
  Patch by Madison May.

- bpo-27611: Fixed support of default root window in the tkinter.tix module.
  Added the master parameter in the DisplayStyle constructor.

- bpo-27348: In the traceback module, restore the formatting of exception
  messages like "Exception: None".  This fixes a regression introduced in
  3.5a2.

- bpo-25651: Allow falsy values to be used for msg parameter of subTest().

- bpo-27778: Fix a memory leak in os.getrandom() when the getrandom() is
  interrupted by a signal and a signal handler raises a Python exception.

- bpo-28200: Fix memory leak on Windows in the os module (fix
  path_converter() function).

- bpo-25400: RobotFileParser now correctly returns default values for
  crawl_delay and request_rate.  Initial patch by Peter Wirtz.

- bpo-27932: Prevent memory leak in win32_ver().

- Fix UnboundLocalError in socket._sendfile_use_sendfile.

- bpo-28075: Check for ERROR_ACCESS_DENIED in Windows implementation of
  os.stat().  Patch by Eryk Sun.

- bpo-22493: Warning message emitted by using inline flags in the middle of
  regular expression now contains a (truncated) regex pattern. Patch by Tim
  Graham.

- bpo-25270: Prevent codecs.escape_encode() from raising SystemError when an
  empty bytestring is passed.

- bpo-28181: Get antigravity over HTTPS. Patch by Kaartic Sivaraam.

- bpo-25895: Enable WebSocket URL schemes in urllib.parse.urljoin. Patch by
  Gergely Imreh and Markus Holtermann.

- bpo-28114: Fix a crash in parse_envlist() when env contains byte strings.
  Patch by Eryk Sun.

- bpo-27599: Fixed buffer overrun in binascii.b2a_qp() and
  binascii.a2b_qp().

- bpo-27906: Fix socket accept exhaustion during high TCP traffic. Patch by
  Kevin Conway.

- bpo-28174: Handle when SO_REUSEPORT isn't properly supported. Patch by
  Seth Michael Larson.

- bpo-26654: Inspect functools.partial in asyncio.Handle.__repr__. Patch by
  iceboy.

- bpo-26909: Fix slow pipes IO in asyncio. Patch by INADA Naoki.

- bpo-28176: Fix callbacks race in asyncio.SelectorLoop.sock_connect.

- bpo-27759: Fix selectors incorrectly retain invalid file descriptors.
  Patch by Mark Williams.

- bpo-28325: Remove vestigial MacOS 9 macurl2path module and its tests.

- bpo-28368: Refuse monitoring processes if the child watcher has no loop
  attached. Patch by Vincent Michel.

- bpo-28369: Raise RuntimeError when transport's FD is used with add_reader,
  add_writer, etc.

- bpo-28370: Speedup asyncio.StreamReader.readexactly. Patch by Коренберг
  Марк.

- bpo-28371: Deprecate passing asyncio.Handles to run_in_executor.

- bpo-28372: Fix asyncio to support formatting of non-python coroutines.

- bpo-28399: Remove UNIX socket from FS before binding. Patch by Коренберг
  Марк.

- bpo-27972: Prohibit Tasks to await on themselves.

- bpo-24142: Reading a corrupt config file left configparser in an invalid
  state. Original patch by Florian Höch.

- bpo-29581: ABCMeta.__new__ now accepts ``**kwargs``, allowing abstract
  base classes to use keyword parameters in __init_subclass__. Patch by Nate
  Soares.

- bpo-25532: inspect.unwrap() will now only try to unwrap an object
  sys.getrecursionlimit() times, to protect against objects which create a
  new object on every attribute access.

- bpo-30177: path.resolve(strict=False) no longer cuts the path after the
  first element not present in the filesystem.  Patch by Antoine Pietri.

Documentation
-------------

- bpo-31294: Fix incomplete code snippet in the ZeroMQSocketListener and
  ZeroMQSocketHandler examples and adapt them to Python 3.

- bpo-21649: Add RFC 7525 and Mozilla server side TLS links to SSL
  documentation.

- bpo-31128: Allow the pydoc server to bind to arbitrary hostnames.

- bpo-30803: Clarify doc on truth value testing. Original patch by Peter
  Thomassen.

- bpo-30176: Add missing attribute related constants in curses
  documentation.

- bpo-30052: the link targets for :func:`bytes` and :func:`bytearray` are
  now their respective type definitions, rather than the corresponding
  builtin function entries. Use :ref:`bytes <func-bytes>` and
  :ref:`bytearray <func-bytearray>` to reference the latter. In order to
  ensure this and future cross-reference updates are applied automatically,
  the daily documentation builds now disable the default output caching
  features in Sphinx.

- bpo-26985: Add missing info of code object in inspect documentation.

- bpo-19824: Improve the documentation for, and links to, template strings
  by emphasizing their utility for internationalization, and by clarifying
  some usage constraints. (See also: bpo-20314, bpo-12518)

- bpo-28929: Link the documentation to its source file on GitHub.

- bpo-25008: Document smtpd.py as effectively deprecated and add a pointer
  to aiosmtpd, a third-party asyncio-based replacement.

- bpo-26355: Add canonical header link on each page to corresponding major
  version of the documentation. Patch by Matthias Bussonnier.

- bpo-29349: Fix Python 2 syntax in code for building the documentation.

- bpo-23722: The data model reference and the porting section in the 3.6
  What's New guide now cover the additional ``__classcell__`` handling
  needed for custom metaclasses to fully support :pep:`487` and
  zero-argument ``super()``.

- bpo-28513: Documented command-line interface of zipfile.

Tests
-----

- bpo-29639: test.support.HOST is now "localhost", a new HOSTv4 constant has
  been added for your ``127.0.0.1`` needs, similar to the existing HOSTv6
  constant.

- bpo-31320: Silence traceback in test_ssl

- bpo-31346: Prefer PROTOCOL_TLS_CLIENT and PROTOCOL_TLS_SERVER protocols
  for SSLContext.

- bpo-25674: Remove sha256.tbs-internet.com ssl test

- bpo-30715: Address ALPN callback changes for OpenSSL 1.1.0f. The latest
  version behaves like OpenSSL 1.0.2 and no longer aborts handshake.

- bpo-30822: regrtest: Exclude tzdata from regrtest --all. When running the
  test suite using --use=all / -u all, exclude tzdata since it makes
  test_datetime too slow (15-20 min on some buildbots) which then times out
  on some buildbots. Fix also regrtest command line parser to allow passing
  -u extralargefile to run test_zipfile64.

- bpo-30695: Add the `set_nomemory(start, stop)` and `remove_mem_hooks()`
  functions to the _testcapi module.

- bpo-30357: test_thread: setUp() now uses support.threading_setup() and
  support.threading_cleanup() to wait until threads complete to avoid random
  side effects on following tests. Initial patch written by Grzegorz
  Grzywacz.

- bpo-30197: Enhanced functions swap_attr() and swap_item() in the
  test.support module. They now work when delete replaced attribute or item
  inside the with statement.  The old value of the attribute or item (or
  None if it doesn't exist) now will be assigned to the target of the "as"
  clause, if there is one.

- bpo-24932: Use proper command line parsing in _testembed

- bpo-28950: Disallow -j0 to be combined with -T/-l in regrtest command line
  arguments.

- bpo-28683: Fix the tests that bind() a unix socket and raise
  PermissionError on Android for a non-root user.

- bpo-26936: Fix the test_socket failures on Android - getservbyname(),
  getservbyport() and getaddrinfo() are broken on some Android API levels.

- bpo-28666: Now test.support.rmtree is able to remove unwritable or
  unreadable directories.

- bpo-23839: Various caches now are cleared before running every test file.

- bpo-26944: Fix test_posix for Android where 'id -G' is entirely wrong or
  missing the effective gid.

- bpo-28409: regrtest: fix the parser of command line arguments.

- bpo-28217: Adds _testconsole module to test console input.

- bpo-26939: Add the support.setswitchinterval() function to fix
  test_functools hanging on the Android armv7 qemu emulator.

Build
-----

- bpo-31354: Allow --with-lto to be used on all builds, not just `make
  profile-opt`.

- bpo-31370: Remove support for building --without-threads. This option is
  not really useful anymore in the 21st century. Removing lots of
  conditional paths allows us to simplify the code base, including in
  difficult to maintain low-level internal code.

- bpo-31341: Per :pep:`11`, support for the IRIX operating system was
  removed.

- bpo-30854: Fix compile error when compiling --without-threads. Patch by
  Masayuki Yamamoto.

- bpo-30687: Locate msbuild.exe on Windows when building rather than
  vcvarsall.bat

- bpo-20210: Support the *disabled* marker in Setup files. Extension modules
  listed after this marker are not built at all, neither by the Makefile nor
  by setup.py.

- bpo-29941: Add ``--with-assertions`` configure flag to explicitly enable C
  ``assert()`` checks. Defaults to off. ``--with-pydebug`` implies
  ``--with-assertions``.

- bpo-28787: Fix out-of-tree builds of Python when configured with
  ``--with--dtrace``.

- bpo-29243: Prevent unnecessary rebuilding of Python during ``make test``,
  ``make install`` and some other make targets when configured with
  ``--enable-optimizations``.

- bpo-23404: Don't regenerate generated files based on file modification
  time anymore: the action is now explicit. Replace ``make touch`` with
  ``make regen-all``.

- bpo-29643: Fix ``--enable-optimization`` didn't work.

- bpo-27593: sys.version and the platform module python_build(),
  python_branch(), and python_revision() functions now use git information
  rather than hg when building from a repo.

- bpo-29572: Update Windows build and OS X installers to use OpenSSL 1.0.2k.

- bpo-27659: Prohibit implicit C function declarations: use
  ``-Werror=implicit-function-declaration`` when possible (GCC and Clang,
  but it depends on the compiler version). Patch written by Chi Hsuan Yen.

- bpo-29384: Remove old Be OS helper scripts.

- bpo-26851: Set Android compilation and link flags.

- bpo-28768: Fix implicit declaration of function _setmode. Patch by
  Masayuki Yamamoto

- bpo-29080: Removes hard dependency on hg.exe from PCBuild/build.bat

- bpo-23903: Added missed names to PC/python3.def.

- bpo-28762: lockf() is available on Android API level 24, but the F_LOCK
  macro is not defined in android-ndk-r13.

- bpo-28538: Fix the compilation error that occurs because if_nameindex() is
  available on Android API level 24, but the if_nameindex structure is not
  defined.

- bpo-20211: Do not add the directory for installing C header files and the
  directory for installing object code libraries to the cross compilation
  search paths. Original patch by Thomas Petazzoni.

- bpo-28849: Do not define sys.implementation._multiarch on Android.

- bpo-10656: Fix out-of-tree building on AIX.  Patch by Tristan Carel and
  Michael Haubenwallner.

- bpo-26359: Rename --with-optimiations to --enable-optimizations.

- bpo-28444: Fix missing extensions modules when cross compiling.

- bpo-28208: Update Windows build and OS X installers to use SQLite 3.14.2.

- bpo-28248: Update Windows build and OS X installers to use OpenSSL 1.0.2j.

- bpo-21124: Fix building the _struct module on Cygwin by passing ``NULL``
  instead of ``&PyType_Type`` to PyVarObject_HEAD_INIT.  Patch by Masayuki
  Yamamoto.

- bpo-13756: Fix building extensions modules on Cygwin.  Patch by Roumen
  Petrov, based on original patch by Jason Tishler.

- bpo-21085: Add configure check for siginfo_t.si_band, which Cygwin does
  not provide. Patch by Masayuki Yamamoto with review and rebase by Erik
  Bray.

- bpo-28258: Fixed build with Estonian locale (python-config and distclean
  targets in Makefile).  Patch by Arfrever Frehtes Taifersar Arahesis.

- bpo-26661: setup.py now detects system libffi with multiarch wrapper.

- bpo-27979: A full copy of libffi is no longer bundled for use when
  building _ctypes on non-OSX UNIX platforms.  An installed copy of libffi
  is now required when building _ctypes on such platforms.

- bpo-15819: Remove redundant include search directory option for building
  outside the source tree.

- bpo-28676: Prevent missing 'getentropy' declaration warning on macOS.
  Patch by Gareth Rees.

Windows
-------

- bpo-31392: Update Windows build to use OpenSSL 1.1.0f

- bpo-30389: Adds detection of Visual Studio 2017 to distutils on Windows.

- bpo-31358: zlib is no longer bundled in the CPython source, instead it is
  downloaded on demand just like bz2, lzma, OpenSSL, Tcl/Tk, and SQLite.

- bpo-31340: Change to building with MSVC v141 (included with Visual Studio
  2017)

- bpo-30581: os.cpu_count() now returns the correct number of processors on
  Windows when the number of logical processors is greater than 64.

- bpo-30916: Pre-build OpenSSL, Tcl and Tk and include the binaries in the
  build.

- bpo-30731: Add a missing xmlns to python.manifest so that it matches the
  schema.

- bpo-30291: Allow requiring 64-bit interpreters from py.exe using -64
  suffix. Contributed by Steve (Gadget) Barnes.

- bpo-30362: Adds list options (-0, -0p) to py.exe launcher. Contributed by
  Steve Barnes.

- bpo-23451: Fix socket deprecation warnings in socketmodule.c. Patch by
  Segev Finer.

- bpo-30450: The build process on Windows no longer depends on Subversion,
  instead pulling external code from GitHub via a Python script.  If Python
  3.6 is not found on the system (via ``py -3.6``), NuGet is used to
  download a copy of 32-bit Python.

- bpo-29579: Removes readme.txt from the installer.

- bpo-25778: winreg does not truncate string correctly (Patch by Eryk Sun)

- bpo-28896: Deprecate WindowsRegistryFinder and disable it by default

- bpo-28522: Fixes mishandled buffer reallocation in getpathp.c

- bpo-28402: Adds signed catalog files for stdlib on Windows.

- bpo-28333: Enables Unicode for ps1/ps2 and input() prompts. (Patch by Eryk
  Sun)

- bpo-28251: Improvements to help manuals on Windows.

- bpo-28110: launcher.msi has different product codes between 32-bit and
  64-bit

- bpo-28161: Opening CON for write access fails

- bpo-28162: WindowsConsoleIO readall() fails if first line starts with
  Ctrl+Z

- bpo-28163: WindowsConsoleIO fileno() passes wrong flags to _open_osfhandle

- bpo-28164: _PyIO_get_console_type fails for various paths

- bpo-28137: Renames Windows path file to ._pth

- bpo-28138: Windows ._pth file should allow import site

IDLE
----

- bpo-31493: IDLE code context -- fix code update and font update timers.
  Canceling timers prevents a warning message when test_idle completes.

- bpo-31488: IDLE - Update non-key options in former extension classes. When
  applying configdialog changes, call .reload for each feature class. Change
  ParenMatch so updated options affect existing instances attached to
  existing editor windows.

- bpo-31477: IDLE - Improve rstrip entry in doc. Strip trailing whitespace
  strips more than blank spaces.  Multiline string literals are not skipped.

- bpo-31480: IDLE - make tests pass with zzdummy extension disabled by
  default.

- bpo-31421: Document how IDLE runs tkinter programs. IDLE calls tcl/tk
  update in the background in order to make live interaction and
  experimentation with tkinter applications much easier.

- bpo-31414: IDLE -- fix tk entry box tests by deleting first. Adding to an
  int entry is not the same as deleting and inserting because int('') will
  fail.

- bpo-31051: Rearrange IDLE configdialog GenPage into Window, Editor, and
  Help sections.

- bpo-30617: IDLE - Add docstrings and tests for outwin subclass of editor.
  Move some data and functions from the class to module level. Patch by
  Cheryl Sabella.

- bpo-31287: IDLE - Do not modify tkinter.message in test_configdialog.

- bpo-27099: Convert IDLE's built-in 'extensions' to regular features. About
  10 IDLE features were implemented as supposedly optional extensions. Their
  different behavior could be confusing or worse for users and not good for
  maintenance. Hence the conversion. The main difference for users is that
  user configurable key bindings for builtin features are now handled
  uniformly. Now, editing a binding in a keyset only affects its value in
  the keyset. All bindings are defined together in the system-specific
  default keysets in config-extensions.def. All custom keysets are saved as
  a whole in config-extension.cfg.  All take effect as soon as one clicks
  Apply or Ok. The affected events are '<<force-open-completions>>',
  '<<expand-word>>', '<<force-open-calltip>>', '<<flash-paren>>',
  '<<format-paragraph>>', '<<run-module>>', '<<check-module>>', and
  '<<zoom-height>>'.  Any (global) customizations made before 3.6.3 will not
  affect their keyset-specific customization after 3.6.3. and vice versa.
  Initial patch by Charles Wohlganger.

- bpo-31206: IDLE: Factor HighPage(Frame) class from ConfigDialog. Patch by
  Cheryl Sabella.

- bpo-31001: Add tests for configdialog highlight tab.  Patch by Cheryl
  Sabella.

- bpo-31205: IDLE: Factor KeysPage(Frame) class from ConfigDialog.  The
  slightly modified tests continue to pass.  Patch by Cheryl Sabella.

- bpo-31130: IDLE -- stop leaks in test_configdialog. Initial patch by
  Victor Stinner.

- bpo-31002: Add tests for configdialog keys tab. Patch by Cheryl Sabella.

- bpo-19903: IDLE: Calltips use `inspect.signature` instead of
  `inspect.getfullargspec`. This improves calltips for builtins converted to
  use Argument Clinic. Patch by Louie Lu.

- bpo-31083: IDLE - Add an outline of a TabPage class in configdialog.
  Update existing classes to match outline. Initial patch by Cheryl Sabella.

- bpo-31050: Factor GenPage(Frame) class from ConfigDialog. The slightly
  modified tests continue to pass. Patch by Cheryl Sabella.

- bpo-31004: IDLE - Factor FontPage(Frame) class from ConfigDialog. Slightly
  modified tests continue to pass. Fix General tests. Patch mostly by Cheryl
  Sabella.

- bpo-30781: IDLE - Use ttk widgets in ConfigDialog. Patches by Terry Jan
  Reedy and Cheryl Sabella.

- bpo-31060: IDLE - Finish rearranging methods of ConfigDialog Grouping
  methods pertaining to each tab and the buttons will aid writing tests and
  improving the tabs and will enable splitting the groups into classes.

- bpo-30853: IDLE -- Factor a VarTrace class out of ConfigDialog. Instance
  tracers manages pairs consisting of a tk variable and a callback function.
  When tracing is turned on, setting the variable calls the function.  Test
  coverage for the new class is 100%.

- bpo-31003: IDLE: Add more tests for General tab.

- bpo-30993: IDLE - Improve configdialog font page and tests. In
  configdialog: Document causal pathways in create_font_tab docstring.
  Simplify some attribute names. Move set_samples calls to var_changed_font
  (idea from Cheryl Sabella).  Move related functions to positions after the
  create widgets function. In test_configdialog: Fix test_font_set so not
  order dependent.  Fix renamed test_indent_scale so it tests the widget.
  Adjust tests for movement of set_samples call.  Add tests for load
  functions.  Put all font tests in one class and tab indent tests in
  another.  Except for two lines, these tests completely cover the related
  functions.

- bpo-30981: IDLE -- Add more configdialog font page tests.

- bpo-28523: IDLE: replace 'colour' with 'color' in configdialog.

- bpo-30917: Add tests for idlelib.config.IdleConf. Increase coverage from
  46% to 96%. Patch by Louie Lu.

- bpo-30934: Document coverage details for idlelib tests. Add section to
  idlelib/idle-test/README.txt. Include check that branches are taken both
  ways. Exclude IDLE-specific code that does not run during unit tests.

- bpo-30913: IDLE: Document ConfigDialog tk Vars, methods, and widgets in
  docstrings This will facilitate improving the dialog and splitting up the
  class. Original patch by Cheryl Sabella.

- bpo-30899: IDLE: Add tests for ConfigParser subclasses in config. Patch by
  Louie Lu.

- bpo-30881: IDLE: Add docstrings to browser.py. Patch by Cheryl Sabella.

- bpo-30851: IDLE: Remove unused variables in configdialog.  One is a
  duplicate, one is set but cannot be altered by users. Patch by Cheryl
  Sabella.

- bpo-30870: IDLE: In Settings dialog, select font with Up, Down keys as
  well as mouse. Initial patch by Louie Lu.

- bpo-8231: IDLE: call config.IdleConf.GetUserCfgDir only once.

- bpo-30779: IDLE: Factor ConfigChanges class from configdialog, put in
  config; test. * In config, put dump test code in a function; run it and
  unittest in   'if __name__ == '__main__'. * Add class config.ConfigChanges
  based on changes_class_v4.py on bpo issue. * Add class
  test_config.ChangesTest, partly using configdialog_tests_v1.py. * Revise
  configdialog to use ConfigChanges; see tracker msg297804. * Revise
  test_configdialog to match configdialog changes. * Remove configdialog
  functions unused or moved to ConfigChanges. Cheryl Sabella contributed
  parts of the patch.

- bpo-30777: IDLE: configdialog - Add docstrings and fix comments. Patch by
  Cheryl Sabella.

- bpo-30495: IDLE: Improve textview with docstrings, PEP8 names, and more
  tests. Patch by Cheryl Sabella.

- bpo-30723: IDLE: Make several improvements to parenmatch. Add 'parens'
  style to highlight both opener and closer. Make 'default' style, which is
  not default, a synonym for 'opener'. Make time-delay work the same with
  all styles. Add help for config dialog extensions tab, including help for
  parenmatch. Add new tests.  Original patch by Charles Wohlganger.

- bpo-30674: IDLE: add docstrings to grep module. Patch by Cheryl Sabella

- bpo-21519: IDLE's basic custom key entry dialog now detects duplicates
  properly. Original patch by Saimadhav Heblikar.

- bpo-29910: IDLE no longer deletes a character after commenting out a
  region by a key shortcut.  Add ``return 'break'`` for this and other
  potential conflicts between IDLE and default key bindings.

- bpo-30728: Review and change idlelib.configdialog names. Lowercase method
  and attribute names. Replace 'colour' with 'color', expand overly cryptic
  names, delete unneeded underscores. Replace ``import *`` with specific
  imports. Patches by Cheryl Sabella.

- bpo-6739: IDLE: Verify user-entered key sequences by trying to bind them
  with tk. Add tests for all 3 validation functions. Original patch by G
  Polo.  Tests added by Cheryl Sabella.

- bpo-15786: Fix several problems with IDLE's autocompletion box. The
  following should now work: clicking on selection box items; using the
  scrollbar; selecting an item by hitting Return. Hangs on MacOSX should no
  longer happen. Patch by Louie Lu.

- bpo-25514: Add doc subsubsection about IDLE failure to start. Popup
  no-connection message directs users to this section.

- bpo-30642: Fix reference leaks in IDLE tests. Patches by Louie Lu and
  Terry Jan Reedy.

- bpo-30495: Add docstrings for textview.py and use PEP8 names. Patches by
  Cheryl Sabella and Terry Jan Reedy.

- bpo-30290: Help-about: use pep8 names and add tests. Increase coverage to
  100%. Patches by Louie Lu, Cheryl Sabella, and Terry Jan Reedy.

- bpo-30303: Add _utest option to textview; add new tests. Increase coverage
  to 100%. Patches by Louie Lu and Terry Jan Reedy.

- bpo-29071: IDLE colors f-string prefixes (but not invalid ur prefixes).

- bpo-28572: Add 10% to coverage of IDLE's test_configdialog. Update and
  augment description of the configuration system.

Tools/Demos
-----------

- bpo-30983: gdb integration commands (py-bt, etc.) work on optimized shared
  builds now, too.  :pep:`523` introduced _PyEval_EvalFrameDefault which
  inlines PyEval_EvalFrameEx on non-debug shared builds.  This broke the
  ability to use py-bt, py-up, and a few other Python-specific gdb
  integrations. The problem is fixed by only looking for
  _PyEval_EvalFrameDefault frames in python-gdb.py.  Original patch by Bruno
  "Polaco" Penteado.

- bpo-29748: Added the slice index converter in Argument Clinic.

- bpo-24037: Argument Clinic now uses the converter `bool(accept={int})`
  rather than `int` for semantical booleans.  This avoids repeating the
  default value for Python and C and will help in converting to `bool` in
  future.

- bpo-29367: python-gdb.py now supports also ``method-wrapper``
  (``wrapperobject``) objects.

- bpo-28023: Fix python-gdb.py didn't support new dict implementation.

- bpo-15369: The pybench and pystone microbenchmark have been removed from
  Tools. Please use the new Python benchmark suite
  https://github.com/python/performance which is more reliable and includes
  a portable version of pybench working on Python 2 and Python 3.

- bpo-28102: The zipfile module CLI now prints usage to stderr. Patch by
  Stephen J. Turnbull.

C API
-----

- bpo-31338: Added the ``Py_UNREACHABLE()`` macro for code paths which are
  never expected to be reached.  This and a few other useful macros are now
  documented in the C API manual.

- bpo-30832: Remove own implementation for thread-local storage. CPython has
  provided the own implementation for thread-local storage (TLS) on
  Python/thread.c, it's used in the case which a platform has not supplied
  native TLS.  However, currently all supported platforms (Windows and
  pthreads) have provided native TLS and defined the Py_HAVE_NATIVE_TLS
  macro with unconditional in any case.

- bpo-30708: PyUnicode_AsWideCharString() now raises a ValueError if the
  second argument is NULL and the wchar_t\* string contains null characters.

- bpo-16500: Deprecate PyOS_AfterFork() and add PyOS_BeforeFork(),
  PyOS_AfterFork_Parent() and PyOS_AfterFork_Child().

- bpo-6532: The type of results of PyThread_start_new_thread() and
  PyThread_get_thread_ident(), and the id parameter of
  PyThreadState_SetAsyncExc() changed from "long" to "unsigned long".

- bpo-27867: Function PySlice_GetIndicesEx() is deprecated and replaced with
  a macro if Py_LIMITED_API is not set or set to the value between
  0x03050400 and 0x03060000 (not including) or 0x03060100 or higher.  Added
  functions PySlice_Unpack() and PySlice_AdjustIndices().

- bpo-29083: Fixed the declaration of some public API functions.
  PyArg_VaParse() and PyArg_VaParseTupleAndKeywords() were not available in
  limited API. PyArg_ValidateKeywordArguments(), PyArg_UnpackTuple() and
  Py_BuildValue() were not available in limited API of version < 3.3 when
  PY_SSIZE_T_CLEAN is defined.

- bpo-28769: The result of PyUnicode_AsUTF8AndSize() and PyUnicode_AsUTF8()
  is now of type ``const char *`` rather of ``char *``.

- bpo-29058: All stable API extensions added after Python 3.2 are now
  available only when Py_LIMITED_API is set to the PY_VERSION_HEX value of
  the minimum Python version supporting this API.

- bpo-28822: The index parameters *start* and *end* of PyUnicode_FindChar()
  are now adjusted to behave like ``str[start:end]``.

- bpo-28808: PyUnicode_CompareWithASCIIString() now never raises exceptions.

- bpo-28761: The fields name and doc of structures PyMemberDef, PyGetSetDef,
  PyStructSequence_Field, PyStructSequence_Desc, and wrapperbase are now of
  type ``const char *`` rather of ``char *``.

- bpo-28748: Private variable _Py_PackageContext is now of type ``const char
  *`` rather of ``char *``.

- bpo-19569: Compiler warnings are now emitted if use most of deprecated
  functions.

- bpo-28426: Deprecated undocumented functions PyUnicode_AsEncodedObject(),
  PyUnicode_AsDecodedObject(), PyUnicode_AsDecodedUnicode() and
  PyUnicode_AsEncodedUnicode().


What's New in Python 3.6.6 final?
=================================

*Release date: 2018-06-27*

There were no new changes in version 3.6.6.



What's New in Python 3.6.6 release candidate 1?
===============================================

*Release date: 2018-06-11*

Core and Builtins
-----------------

- bpo-33786: Fix asynchronous generators to handle GeneratorExit in athrow()
  correctly

- bpo-30654: Fixed reset of the SIGINT handler to SIG_DFL on interpreter
  shutdown even when there was a custom handler set previously. Patch by
  Philipp Kerling.

- bpo-33622: Fixed a leak when the garbage collector fails to add an object
  with the ``__del__`` method or referenced by it into the
  :data:`gc.garbage` list. :c:func:`PyGC_Collect` can now be called when an
  exception is set and preserves it.

- bpo-31849: Fix signed/unsigned comparison warning in pyhash.c.

- bpo-33391: Fix a leak in set_symmetric_difference().

- bpo-28055: Fix unaligned accesses in siphash24(). Patch by Rolf Eike Beer.

- bpo-33231: Fix potential memory leak in ``normalizestring()``.

- bpo-29922: Improved error messages in 'async with' when ``__aenter__()``
  or ``__aexit__()`` return non-awaitable object.

- bpo-33199: Fix ``ma_version_tag`` in dict implementation is uninitialized
  when copying from key-sharing dict.

- bpo-33041: Fixed jumping when the function contains an ``async for`` loop.

- bpo-32282: Fix an unnecessary ifdef in the include of VersionHelpers.h in
  socketmodule on Windows.

- bpo-21983: Fix a crash in `ctypes.cast()` in case the type argument is a
  ctypes structured data type. Patch by Eryk Sun and Oren Milman.

Library
-------

- bpo-30167: Prevent site.main() exception if PYTHONSTARTUP is set. Patch by
  Steve Weber.

- bpo-33812: Datetime instance d with non-None tzinfo, but with
  d.tzinfo.utcoffset(d) returning None is now treated as naive by the
  astimezone() method.

- bpo-30805: Avoid race condition with debug logging

- bpo-33767: The concatenation (``+``) and repetition (``*``) sequence
  operations now raise :exc:`TypeError` instead of :exc:`SystemError` when
  performed on :class:`mmap.mmap` objects.  Patch by Zackery Spytz.

- bpo-32684: Fix gather to propagate cancellation of itself even with
  return_exceptions.

- bpo-33674: Fix a race condition in SSLProtocol.connection_made() of
  asyncio.sslproto: start immediately the handshake instead of using
  call_soon(). Previously, data_received() could be called before the
  handshake started, causing the handshake to hang or fail.

- bpo-31647: Fixed bug where calling write_eof() on a
  _SelectorSocketTransport after it's already closed raises AttributeError.

- bpo-33672: Fix Task.__repr__ crash with Cython's bogus coroutines

- bpo-33469: Fix RuntimeError after closing loop that used run_in_executor

- bpo-11874: Use a better regex when breaking usage into wrappable parts.
  Avoids bogus assertion errors from custom metavar strings.

- bpo-30877: Fixed a bug in the Python implementation of the JSON decoder
  that prevented the cache of parsed strings from clearing after finishing
  the decoding. Based on patch by c-fos.

- bpo-33548: tempfile._candidate_tempdir_list should consider common TEMP
  locations

- bpo-33542: Prevent ``uuid.get_node`` from using a DUID instead of a MAC on
  Windows. Patch by Zvi Effron

- bpo-26819: Fix race condition with `ReadTransport.resume_reading` in
  Windows proactor event loop.

- bpo-28556: Minor fixes in typing module: add annotations to
  ``NamedTuple.__new__``, pass ``*args`` and ``**kwds`` in
  ``Generic.__new__``.  Original PRs by Paulius Šarka and Chad Dombrova.

- bpo-20087: Updated alias mapping with glibc 2.27 supported locales.

- bpo-33422: Fix trailing quotation marks getting deleted when looking up
  byte/string literals on pydoc. Patch by Andrés Delfino.

- bpo-33197: Update error message when constructing invalid
  inspect.Parameters Patch by Dong-hee Na.

- bpo-33383: Fixed crash in the get() method of the :mod:`dbm.ndbm` database
  object when it is called with a single argument.

- bpo-33329: Fix multiprocessing regression on newer glibcs

- bpo-991266: Fix quoting of the ``Comment`` attribute of
  :class:`http.cookies.SimpleCookie`.

- bpo-33131: Upgrade bundled version of pip to 10.0.1.

- bpo-33308: Fixed a crash in the :mod:`parser` module when converting an ST
  object to a tree of tuples or lists with ``line_info=False`` and
  ``col_info=True``.

- bpo-33263: Fix FD leak in `_SelectorSocketTransport`  Patch by Vlad
  Starostin.

- bpo-33256: Fix display of ``<module>`` call in the html produced by
  ``cgitb.html()``. Patch by Stéphane Blondon.

- bpo-33203: ``random.Random.choice()`` now raises ``IndexError`` for empty
  sequences consistently even when called from subclasses without a
  ``getrandbits()`` implementation.

- bpo-33224: Update difflib.mdiff() for :pep:`479`.  Convert an uncaught
  StopIteration in a generator into a return-statement.

- bpo-33209: End framing at the end of C implementation of
  :func:`pickle.Pickler.dump`.

- bpo-32861: The urllib.robotparser's ``__str__`` representation now
  includes wildcard entries and the "Crawl-delay" and "Request-rate" fields.
  Patch by Michael Lazar.

- bpo-33096: Allow ttk.Treeview.insert to insert iid that has a false
  boolean value. Note iid=0 and iid=False would be same. Patch by Garvit
  Khatri.

- bpo-33127: The ssl module now compiles with LibreSSL 2.7.1.

- bpo-33021: Release the GIL during fstat() calls, avoiding hang of all
  threads when calling mmap.mmap(), os.urandom(), and random.seed().  Patch
  by Nir Soffer.

- bpo-27683: Fix a regression in :mod:`ipaddress` that result of
  :meth:`hosts` is empty when the network is constructed by a tuple
  containing an integer mask and only 1 bit left for addresses.

- bpo-32844: Fix wrong redirection of a low descriptor (0 or 1) to stderr in
  subprocess if another low descriptor is closed.

- bpo-31908: Fix output of cover files for ``trace`` module command-line
  tool. Previously emitted cover files only when ``--missing`` option was
  used. Patch by Michael Selik.

- bpo-31457: If nested log adapters are used, the inner ``process()``
  methods are no longer omitted.

- bpo-16865: Support arrays >=2GiB in :mod:`ctypes`.  Patch by Segev Finer.

- bpo-31238: pydoc: the stop() method of the private ServerThread class now
  waits until DocServer.serve_until_quit() completes and then explicitly
  sets its docserver attribute to None to break a reference cycle.

Documentation
-------------

- bpo-33503: Fix broken pypi link

- bpo-33421: Add missing documentation for ``typing.AsyncContextManager``.

- bpo-33378: Add Korean language switcher for https://docs.python.org/3/

- bpo-33276: Clarify that the ``__path__`` attribute on modules cannot be
  just any value.

- bpo-33201: Modernize documentation for writing C extension types.

- bpo-33195: Deprecate ``Py_UNICODE`` usage in ``c-api/arg`` document.
  ``Py_UNICODE`` related APIs are deprecated since Python 3.3, but it is
  missed in the document.

- bpo-33126: Document PyBuffer_ToContiguous().

- bpo-27212: Modify documentation for the :func:`islice` recipe to consume
  initial values up to the start index.

- bpo-28247: Update :mod:`zipapp` documentation to describe how to make
  standalone applications.

- bpo-18802: Documentation changes for ipaddress.  Patch by Jon Foster and
  Berker Peksag.

- bpo-27428: Update documentation to clarify that ``WindowsRegistryFinder``
  implements ``MetaPathFinder``. (Patch by Himanshu Lakhara)

- bpo-8243: Add a note about curses.addch and curses.addstr exception
  behavior when writing outside a window, or pad.

- bpo-31432: Clarify meaning of CERT_NONE, CERT_OPTIONAL, and CERT_REQUIRED
  flags for ssl.SSLContext.verify_mode.

Tests
-----

- bpo-33655: Ignore test_posix_fallocate failures on BSD platforms that
  might be due to running on ZFS.

- bpo-19417: Add test_bdb.py.

Build
-----

- bpo-5755: Move ``-Wstrict-prototypes`` option to ``CFLAGS_NODIST`` from
  ``OPT``. This option emitted annoying warnings when building extension
  modules written in C++.

- bpo-33614: Ensures module definition files for the stable ABI on Windows
  are correctly regenerated.

- bpo-33522: Enable CI builds on Visual Studio Team Services at
  https://python.visualstudio.com/cpython

- bpo-33012: Add ``-Wno-cast-function-type`` for gcc 8 for silencing
  warnings about function casts like casting to PyCFunction in method
  definition lists.

- bpo-33394: Enable the verbose build for extension modules, when GNU make
  is passed macros on the command line.

Windows
-------

- bpo-33184: Update Windows installer to OpenSSL 1.0.2o.

macOS
-----

- bpo-33184: Update macOS installer build to use OpenSSL 1.0.2o.

IDLE
----

- bpo-33656: On Windows, add API call saying that tk scales for DPI. On
  Windows 8.1+ or 10, with DPI compatibility properties of the Python binary
  unchanged, and a monitor resolution greater than 96 DPI, this should make
  text and lines sharper.  It should otherwise have no effect.

- bpo-33768: Clicking on a context line moves that line to the top of the
  editor window.

- bpo-33763: IDLE: Use read-only text widget for code context instead of
  label widget.

- bpo-33664: Scroll IDLE editor text by lines. Previously, the mouse wheel
  and scrollbar slider moved text by a fixed number of pixels, resulting in
  partial lines at the top of the editor box.  The change also applies to
  the shell and grep output windows, but not to read-only text views.

- bpo-33679: Enable theme-specific color configuration for Code Context. Use
  the Highlights tab to see the setting for built-in themes or add settings
  to custom themes.

- bpo-33642: Display up to maxlines non-blank lines for Code Context. If
  there is no current context, show a single blank line.

- bpo-33628: IDLE: Cleanup codecontext.py and its test.

- bpo-33564: IDLE's code context now recognizes async as a block opener.

- bpo-29706: IDLE now colors async and await as keywords in 3.6. They become
  full keywords in 3.7.

- bpo-21474: Update word/identifier definition from ascii to unicode. In
  text and entry boxes, this affects selection by double-click, movement
  left/right by control-left/right, and deletion left/right by
  control-BACKSPACE/DEL.

- bpo-33204: IDLE: consistently color invalid string prefixes. A 'u' string
  prefix cannot be paired with either 'r' or 'f'. Consistently color as much
  of the prefix, starting at the right, as is valid. Revise and extend
  colorizer test.

- bpo-32831: Add docstrings and tests for codecontext.

Tools/Demos
-----------

- bpo-33189: :program:`pygettext.py` now recognizes only literal strings as
  docstrings and translatable strings, and rejects bytes literals and
  f-string expressions.

- bpo-31920: Fixed handling directories as arguments in the ``pygettext``
  script. Based on patch by Oleg Krasnikov.

- bpo-29673: Fix pystackv and pystack gdbinit macros.

- bpo-32885: Add an ``-n`` flag for ``Tools/scripts/pathfix.py`` to disable
  automatic backup creation (files with ``~`` suffix).

- bpo-31583: Fix 2to3 for using with --add-suffix option but without
  --output-dir option for relative path to files in current directory.

C API
-----

- bpo-32374: Document that m_traverse for multi-phase initialized modules
  can be called with m_state=NULL, and add a sanity check


What's New in Python 3.6.5 final?
=================================

*Release date: 2018-03-28*

Tests
-----

- bpo-32872: Avoid regrtest compatibility issue with namespace packages.

Build
-----

- bpo-33163: Upgrade pip to 9.0.3 and setuptools to v39.0.1.


What's New in Python 3.6.5 release candidate 1?
===============================================

*Release date: 2018-03-13*

Security
--------

- bpo-33001: Minimal fix to prevent buffer overrun in os.symlink on Windows

- bpo-32981: Regexes in difflib and poplib were vulnerable to catastrophic
  backtracking. These regexes formed potential DOS vectors (REDOS). They
  have been refactored. This resolves CVE-2018-1060 and CVE-2018-1061. Patch
  by Jamie Davis.

Core and Builtins
-----------------

- bpo-33026: Fixed jumping out of "with" block by setting f_lineno.

- bpo-17288: Prevent jumps from 'return' and 'exception' trace events.

- bpo-32889: Update Valgrind suppression list to account for the rename of
  ``Py_ADDRESS_IN_RANG`` to ``address_in_range``.

- bpo-32650: Pdb and other debuggers dependent on bdb.py will correctly step
  over (next command) native coroutines. Patch by Pablo Galindo.

- bpo-32685: Improve suggestion when the Python 2 form of print statement is
  either present on the same line as the header of a compound statement or
  else terminated by a semi-colon instead of a newline. Patch by Nitish
  Chandra.

- bpo-32583: Fix possible crashing in builtin Unicode decoders caused by
  write out-of-bound errors when using customized decode error handlers.

- bpo-26163: Improved frozenset() hash to create more distinct hash values
  when faced with datasets containing many similar values.

- bpo-27169: The ``__debug__`` constant is now optimized out at compile
  time. This fixes also bpo-22091.

- bpo-32329: ``sys.flags.hash_randomization`` is now properly set to 0 when
  hash randomization is turned off by ``PYTHONHASHSEED=0``.

- bpo-30416: The optimizer is now protected from spending much time doing
  complex calculations and consuming much memory for creating large
  constants in constant folding.

- bpo-18533: ``repr()`` on a dict containing its own ``values()`` or
  ``items()`` no longer raises ``RecursionError``; OrderedDict similarly.
  Instead, use ``...``, as for other recursive structures.  Patch by Ben
  North.

- bpo-32028: Leading whitespace is now correctly ignored when generating
  suggestions for converting Py2 print statements to Py3 builtin print
  function calls. Patch by Sanyam Khurana.

- bpo-32137: The repr of deeply nested dict now raises a RecursionError
  instead of crashing due to a stack overflow.

Library
-------

- bpo-33064: lib2to3 now properly supports trailing commas after ``*args``
  and ``**kwargs`` in function signatures.

- bpo-31804: Avoid failing in multiprocessing.Process if the standard
  streams are closed or None at exit.

- bpo-33037: Skip sending/receiving data after SSL transport closing.

- bpo-30353: Fix ctypes pass-by-value for structs on 64-bit Cygwin/MinGW.

- bpo-33009: Fix inspect.signature() for single-parameter partialmethods.

- bpo-32969: Expose several missing constants in zlib and fix corresponding
  documentation.

- bpo-32713: Fixed tarfile.itn handling of out-of-bounds float values. Patch
  by Joffrey Fuhrer.

- bpo-30622: The ssl module now detects missing NPN support in LibreSSL.

- bpo-32922: dbm.open() now encodes filename with the filesystem encoding
  rather than default encoding.

- bpo-32859: In ``os.dup2``, don't check every call whether the ``dup3``
  syscall exists or not.

- bpo-21060: Rewrite confusing message from setup.py upload from "No dist
  file created in earlier command" to the more helpful "Must create and
  upload files in one command".

- bpo-32857: In :mod:`tkinter`, ``after_cancel(None)`` now raises a
  :exc:`ValueError` instead of canceling the first scheduled function.
  Patch by Cheryl Sabella.

- bpo-32852: Make sure sys.argv remains as a list when running trace.

- bpo-32841: Fixed `asyncio.Condition` issue which silently ignored
  cancellation after notifying and cancelling a conditional lock. Patch by
  Bar Harel.

- bpo-31787: Fixed refleaks of ``__init__()`` methods in various modules.
  (Contributed by Oren Milman)

- bpo-30157: Fixed guessing quote and delimiter in csv.Sniffer.sniff() when
  only the last field is quoted.  Patch by Jake Davis.

- bpo-32394: socket: Remove TCP_FASTOPEN, TCP_KEEPCNT flags on older version
  Windows during run-time.

- bpo-32777: Fix a rare but potential pre-exec child process deadlock in
  subprocess on POSIX systems when marking file descriptors inheritable on
  exec in the child process.  This bug appears to have been introduced in
  3.4.

- bpo-32647: The ctypes module used to depend on indirect linking for
  dlopen. The shared extension is now explicitly linked against libdl on
  platforms with dl.

- bpo-32734: Fixed ``asyncio.Lock()`` safety issue which allowed acquiring
  and locking the same lock multiple times, without it being free. Patch by
  Bar Harel.

- bpo-32727: Do not include name field in SMTP envelope from address. Patch
  by Stéphane Wirtel

- bpo-27931: Fix email address header parsing error when the username is an
  empty quoted string. Patch by Xiang Zhang.

- bpo-32304: distutils' upload command no longer corrupts tar files ending
  with a CR byte, and no longer tries to convert CR to CRLF in any of the
  upload text fields.

- bpo-32502: uuid.uuid1 no longer raises an exception if a 64-bit hardware
  address is encountered.

- bpo-31848: Fix the error handling in Aifc_read.initfp() when the SSND
  chunk is not found. Patch by Zackery Spytz.

- bpo-32555: On FreeBSD and Solaris, os.strerror() now always decode the
  byte string from the current locale encoding, rather than using
  ASCII/surrogateescape in some cases.

- bpo-32521: The nis module is now compatible with new libnsl and headers
  location.

- bpo-32473: Improve ABCMeta._dump_registry() output readability

- bpo-32521: glibc has removed Sun RPC. Use replacement libtirpc headers and
  library in nis module.

- bpo-32228: Ensure that ``truncate()`` preserves the file position (as
  reported by ``tell()``) after writes longer than the buffer size.

- bpo-26133: Don't unsubscribe signals in asyncio UNIX event loop on
  interpreter shutdown.

- bpo-32185: The SSL module no longer sends IP addresses in SNI TLS
  extension on platforms with OpenSSL 1.0.2+ or inet_pton.

- bpo-32323: :func:`urllib.parse.urlsplit()` does not convert zone-id
  (scope) to lower case for scoped IPv6 addresses in hostnames now.

- bpo-32302: Fix bdist_wininst of distutils for CRT v142: it binary
  compatible with CRT v140.

- bpo-32255: A single empty field is now always quoted when written into a
  CSV file. This allows to distinguish an empty row from a row consisting of
  a single empty field. Patch by Licht Takeuchi.

- bpo-32277: Raise ``NotImplementedError`` instead of ``SystemError`` on
  platforms where ``chmod(..., follow_symlinks=False)`` is not supported.
  Patch by Anthony Sottile.

- bpo-32199: The getnode() ip getter now uses 'ip link' instead of 'ip link
  list'.

- bpo-27456: Ensure TCP_NODELAY is set on Linux. Tests by Victor Stinner.

- bpo-31900: The :func:`locale.localeconv` function now sets temporarily the
  ``LC_CTYPE`` locale to the ``LC_NUMERIC`` locale to decode
  ``decimal_point`` and ``thousands_sep`` byte strings if they are non-ASCII
  or longer than 1 byte, and the ``LC_NUMERIC`` locale is different than the
  ``LC_CTYPE`` locale. This temporary change affects other threads. Same
  change for the :meth:`str.format` method when formatting a number
  (:class:`int`, :class:`float`, :class:`float` and subclasses) with the
  ``n`` type (ex: ``'{:n}'.format(1234)``).

- bpo-31802: Importing native path module (``posixpath``, ``ntpath``) now
  works even if the ``os`` module still is not imported.

Documentation
-------------

- bpo-17232: Clarify docs for -O and -OO.  Patch by Terry Reedy.

- bpo-32800: Update link to w3c doc for xml default namespaces.

- bpo-8722: Document :meth:`__getattr__` behavior when property :meth:`get`
  method raises :exc:`AttributeError`.

- bpo-32614: Modify RE examples in documentation to use raw strings to
  prevent :exc:`DeprecationWarning` and add text to REGEX HOWTO to highlight
  the deprecation.

- bpo-31972: Improve docstrings for `pathlib.PurePath` subclasses.

- bpo-17799: Explain real behaviour of sys.settrace and sys.setprofile and
  their C-API counterparts regarding which type of events are received in
  each function. Patch by Pablo Galindo Salgado.

Tests
-----

- bpo-32517: Fix failing ``test_asyncio`` on macOS 10.12.2+ due to transport
  of ``KqueueSelector`` loop was not being closed.

- bpo-32721: Fix test_hashlib to not fail if the _md5 module is not built.

- bpo-32252: Fix faulthandler_suppress_crash_report() used to prevent core
  dump files when testing crashes. getrlimit() returns zero on success.

- bpo-31518: Debian Unstable has disabled TLS 1.0 and 1.1 for
  SSLv23_METHOD(). Change TLS/SSL protocol of some tests to PROTOCOL_TLS or
  PROTOCOL_TLSv1_2 to make them pass on Debian.

Build
-----

- bpo-32635: Fix segfault of the crypt module when libxcrypt is provided
  instead of libcrypt at the system.

Windows
-------

- bpo-33016: Fix potential use of uninitialized memory in
  nt._getfinalpathname

- bpo-32903: Fix a memory leak in os.chdir() on Windows if the current
  directory is set to a UNC path.

- bpo-31966: Fixed WindowsConsoleIO.write() for writing empty data.

- bpo-32409: Ensures activate.bat can handle Unicode contents.

- bpo-32457: Improves handling of denormalized executable path when
  launching Python.

- bpo-32370: Use the correct encoding for ipconfig output in the uuid
  module. Patch by Segev Finer.

- bpo-29248: Fix :func:`os.readlink` on Windows, which was mistakenly
  treating the ``PrintNameOffset`` field of the reparse data buffer as a
  number of characters instead of bytes. Patch by Craig Holmquist and SSE4.

- bpo-32588: Create standalone _distutils_findvs module.

macOS
-----

- bpo-32726: Provide an additional, more modern macOS installer variant that
  supports macOS 10.9+ systems in 64-bit mode only. Upgrade the supplied
  third-party libraries to OpenSSL 1.0.2n, XZ 5.2.3, and SQLite 3.22.0. The
  10.9+ installer now links with and supplies its own copy of Tcl/Tk 8.6.8.

IDLE
----

- bpo-32984: Set ``__file__`` while running a startup file.  Like Python,
  IDLE optionally runs one startup file in the Shell window before
  presenting the first interactive input prompt.  For IDLE, ``-s`` runs a
  file named in environmental variable  :envvar:`IDLESTARTUP` or
  :envvar:`PYTHONSTARTUP`; ``-r file`` runs ``file``.  Python sets
  ``__file__`` to the startup file name before running the file and unsets
  it before the first prompt.  IDLE now does the same when run normally,
  without the ``-n`` option.

- bpo-32940: Simplify and rename StringTranslatePseudoMapping in pyparse.

- bpo-32916: Change ``str`` to ``code`` in pyparse.

- bpo-32905: Remove unused code in pyparse module.

- bpo-32874: Add tests for pyparse.

- bpo-32837: Using the system and place-dependent default encoding for
  open() is a bad idea for IDLE's system and location-independent files.

- bpo-32826: Add "encoding=utf-8" to open() in IDLE's test_help_about. GUI
  test test_file_buttons() only looks at initial ascii-only lines, but
  failed on systems where open() defaults to 'ascii' because readline()
  internally reads and decodes far enough ahead to encounter a non-ascii
  character in CREDITS.txt.

- bpo-32765: Update configdialog General tab docstring to add new widgets to
  the widget list.

Tools/Demos
-----------

- bpo-24960: 2to3 and lib2to3 can now read pickled grammar files using
  pkgutil.get_data() rather than probing the filesystem. This lets 2to3 and
  lib2to3 work when run from a zipfile.

- bpo-32222: Fix pygettext not extracting docstrings for functions with type
  annotated arguments. Patch by Toby Harradine.

C API
-----

- bpo-29084: Undocumented C API for OrderedDict has been excluded from the
  limited C API. It was added by mistake and actually never worked in the
  limited C API.


What's New in Python 3.6.4 final?
=================================

*Release date: 2017-12-18*

There were no new code changes in version 3.6.4 since v3.6.4rc1.



What's New in Python 3.6.4 release candidate 1?
===============================================

*Release date: 2017-12-05*

Core and Builtins
-----------------

- bpo-32176: co_flags.CO_NOFREE is now always set correctly by the code
  object constructor based on freevars and cellvars, rather than needing to
  be set correctly by the caller. This ensures it will be cleared
  automatically when additional cell references are injected into a modified
  code object and function.

- bpo-31949: Fixed several issues in printing tracebacks
  (PyTraceBack_Print()). Setting sys.tracebacklimit to 0 or less now
  suppresses printing tracebacks. Setting sys.tracebacklimit to None now
  causes using the default limit. Setting sys.tracebacklimit to an integer
  larger than LONG_MAX now means using the limit LONG_MAX rather than the
  default limit. Fixed integer overflows in the case of more than ``2**31``
  traceback items on Windows. Fixed output errors handling.

- bpo-30696: Fix the interactive interpreter looping endlessly when no
  memory.

- bpo-20047: Bytearray methods partition() and rpartition() now accept only
  bytes-like objects as separator, as documented.  In particular they now
  raise TypeError rather of returning a bogus result when an integer is
  passed as a separator.

- bpo-31852: Fix a segmentation fault caused by a combination of the async
  soft keyword and continuation lines.

- bpo-21720: BytesWarning no longer emitted when the *fromlist* argument of
  ``__import__()`` or the ``__all__`` attribute of the module contain bytes
  instances.

- bpo-31825: Fixed OverflowError in the 'unicode-escape' codec and in
  codecs.escape_decode() when decode an escaped non-ascii byte.

- bpo-28603: Print the full context/cause chain of exceptions on interpreter
  exit, even if an exception in the chain is unhashable or compares equal to
  later ones. Patch by Zane Bitter.

- bpo-31786: Fix timeout rounding in the select module to round correctly
  negative timeouts between -1.0 and 0.0. The functions now block waiting
  for events as expected. Previously, the call was incorrectly non-blocking.
  Patch by Pablo Galindo.

- bpo-31642: Restored blocking "from package import module" by setting
  sys.modules["package.module"] to None.

- bpo-31626: Fixed a bug in debug memory allocator.  There was a write to
  freed memory after shrinking a memory block.

- bpo-31619: Fixed a ValueError when convert a string with large number of
  underscores to integer with binary base.

- bpo-31592: Fixed an assertion failure in Python parser in case of a bad
  `unicodedata.normalize()`. Patch by Oren Milman.

- bpo-31588: Raise a `TypeError` with a helpful error message when class
  creation fails due to a metaclass with a bad ``__prepare__()`` method.
  Patch by Oren Milman.

- bpo-31566: Fix an assertion failure in `_warnings.warn()` in case of a bad
  ``__name__`` global. Patch by Oren Milman.

- bpo-31505: Fix an assertion failure in `json`, in case
  `_json.make_encoder()` received a bad `encoder()` argument. Patch by Oren
  Milman.

- bpo-31492: Fix assertion failures in case of failing to import from a
  module with a bad ``__name__`` attribute, and in case of failing to access
  an attribute of such a module. Patch by Oren Milman.

- bpo-31490: Fix an assertion failure in `ctypes` class definition, in case
  the class has an attribute whose name is specified in ``_anonymous_`` but
  not in ``_fields_``. Patch by Oren Milman.

- bpo-31478: Fix an assertion failure in `_random.Random.seed()` in case the
  argument has a bad ``__abs__()`` method. Patch by Oren Milman.

- bpo-31315: Fix an assertion failure in imp.create_dynamic(), when
  spec.name is not a string. Patch by Oren Milman.

- bpo-31311: Fix a crash in the ``__setstate__()`` method of
  `ctypes._CData`, in case of a bad ``__dict__``. Patch by Oren Milman.

- bpo-31293: Fix crashes in true division and multiplication of a timedelta
  object by a float with a bad as_integer_ratio() method. Patch by Oren
  Milman.

- bpo-31285: Fix an assertion failure in `warnings.warn_explicit`, when the
  return value of the received loader's get_source() has a bad splitlines()
  method. Patch by Oren Milman.

- bpo-30817: `PyErr_PrintEx()` clears now the ignored exception that may be
  raised by `_PySys_SetObjectId()`, for example when no memory.

Library
-------

- bpo-28556: Two minor fixes for ``typing`` module: allow shallow copying
  instances of generic classes, improve interaction of ``__init_subclass__``
  with generics. Original PRs by Ivan Levkivskyi.

- bpo-27240: The header folding algorithm for the new email policies has
  been rewritten, which also fixes bpo-30788, bpo-31831, and bpo-32182.  In
  particular, RFC2231 folding is now done correctly.

- bpo-32186: io.FileIO.readall() and io.FileIO.read() now release the GIL
  when getting the file size. Fixed hang of all threads with inaccessible
  NFS server. Patch by Nir Soffer.

- bpo-12239: Make :meth:`msilib.SummaryInformation.GetProperty` return
  ``None`` when the value of property is ``VT_EMPTY``.  Initial patch by
  Mark Mc Mahon.

- bpo-31325: Fix wrong usage of :func:`collections.namedtuple` in the
  :meth:`RobotFileParser.parse() <urllib.robotparser.RobotFileParser.parse>`
  method. Initial patch by Robin Wellner.

- bpo-12382: :func:`msilib.OpenDatabase` now raises a better exception
  message when it couldn't open or create an MSI file.  Initial patch by
  William Tisäter.

- bpo-32110: ``codecs.StreamReader.read(n)`` now returns not more than *n*
  characters/bytes for non-negative *n*. This makes it compatible with
  ``read()`` methods of other file-like objects.

- bpo-32072: Fixed issues with binary plists: Fixed saving bytearrays.
  Identical objects will be saved only once. Equal references will be load
  as identical objects. Added support for saving and loading recursive data
  structures.

- bpo-32034: Make asyncio.IncompleteReadError and LimitOverrunError
  pickleable.

- bpo-32015: Fixed the looping of asyncio in the case of reconnection the
  socket during waiting async read/write from/to the socket.

- bpo-32011: Restored support of loading marshal files with the TYPE_INT64
  code. These files can be produced in Python 2.7.

- bpo-31970: Reduce performance overhead of asyncio debug mode.

- bpo-9678: Fixed determining the MAC address in the uuid module: Using
  ifconfig on NetBSD and OpenBSD. Using arp on Linux, FreeBSD, NetBSD and
  OpenBSD. Based on patch by Takayuki Shimizukawa.

- bpo-30057: Fix potential missed signal in signal.signal().

- bpo-31933: Fix Blake2 params leaf_size and node_offset on big endian
  platforms. Patch by Jack O'Connor.

- bpo-31927: Fixed compilation of the socket module on NetBSD 8.  Fixed
  assertion failure or reading arbitrary data when parse a AF_BLUETOOTH
  address on NetBSD and DragonFly BSD.

- bpo-27666: Fixed stack corruption in curses.box() and curses.ungetmouse()
  when the size of types chtype or mmask_t is less than the size of C long.
  curses.box() now accepts characters as arguments.  Based on patch by Steve
  Fink.

- bpo-31897: plistlib now catches more errors when read binary plists and
  raises InvalidFileException instead of unexpected exceptions.

- bpo-25720: Fix the method for checking pad state of curses WINDOW. Patch
  by Masayuki Yamamoto.

- bpo-31893: Fixed the layout of the kqueue_event structure on OpenBSD and
  NetBSD. Fixed the comparison of the kqueue_event objects.

- bpo-31891: Fixed building the curses module on NetBSD.

- bpo-28416: Instances of pickle.Pickler subclass with the persistent_id()
  method and pickle.Unpickler subclass with the persistent_load() method no
  longer create reference cycles.

- bpo-28326: Fix multiprocessing.Process when stdout and/or stderr is closed
  or None.

- bpo-31457: If nested log adapters are used, the inner ``process()``
  methods are no longer omitted.

- bpo-31457: The ``manager`` property on LoggerAdapter objects is now
  properly settable.

- bpo-31806: Fix timeout rounding in time.sleep(), threading.Lock.acquire()
  and socket.socket.settimeout() to round correctly negative timeouts
  between -1.0 and 0.0. The functions now block waiting for events as
  expected. Previously, the call was incorrectly non-blocking. Patch by
  Pablo Galindo.

- bpo-28603: traceback: Fix a TypeError that occurred during printing of
  exception tracebacks when either the current exception or an exception in
  its context/cause chain is unhashable. Patch by Zane Bitter.

- bpo-30058: Fixed buffer overflow in select.kqueue.control().

- bpo-31770: Prevent a crash when calling the ``__init__()`` method of a
  ``sqlite3.Cursor`` object more than once. Patch by Oren Milman.

- bpo-31672: ``idpattern`` in ``string.Template`` matched some non-ASCII
  characters. Now it uses ``-i`` regular expression local flag to avoid
  non-ASCII characters.

- bpo-31764: Prevent a crash in ``sqlite3.Cursor.close()`` in case the
  ``Cursor`` object is uninitialized. Patch by Oren Milman.

- bpo-31752: Fix possible crash in timedelta constructor called with custom
  integers.

- bpo-31701: On Windows, faulthandler.enable() now ignores MSC and COM
  exceptions.

- bpo-31728: Prevent crashes in `_elementtree` due to unsafe cleanup of
  `Element.text` and `Element.tail`. Patch by Oren Milman.

- bpo-31620: an empty asyncio.Queue now doesn't leak memory when queue.get
  pollers timeout

- bpo-31632: Fix method set_protocol() of class _SSLProtocolTransport in
  asyncio module. This method was previously modifying a wrong reference to
  the protocol.

- bpo-31675: Fixed memory leaks in Tkinter's methods splitlist() and split()
  when pass a string larger than 2 GiB.

- bpo-31673: Fixed typo in the name of Tkinter's method adderrorinfo().

- bpo-30806: Fix the string representation of a netrc object.

- bpo-15037: Added a workaround for getkey() in curses for ncurses 5.7 and
  earlier.

- bpo-25351: Avoid venv activate failures with undefined variables

- bpo-25532: inspect.unwrap() will now only try to unwrap an object
  sys.getrecursionlimit() times, to protect against objects which create a
  new object on every attribute access.

- bpo-30347: Stop crashes when concurrently iterate over itertools.groupby()
  iterators.

- bpo-31516: ``threading.current_thread()`` should not return a dummy thread
  at shutdown.

- bpo-31351: python -m ensurepip now exits with non-zero exit code if pip
  bootstrapping has failed.

- bpo-31482: ``random.seed()`` now works with bytes in version=1

- bpo-31334: Fix ``poll.poll([timeout])`` in the ``select`` module for
  arbitrary negative timeouts on all OSes where it can only be a
  non-negative integer or -1. Patch by Riccardo Coccioli.

- bpo-31310: multiprocessing's semaphore tracker should be launched again if
  crashed.

- bpo-31308: Make multiprocessing's forkserver process immune to Ctrl-C and
  other user interruptions. If it crashes, restart it when necessary.

Documentation
-------------

- bpo-32105: Added asyncio.BaseEventLoop.connect_accepted_socket
  versionadded marker.

- bpo-31537: Fix incorrect usage of ``get_history_length`` in readline
  documentation example code. Patch by Brad Smith.

- bpo-30085: The operator functions without double underscores are preferred
  for clarity. The one with underscores are only kept for
  back-compatibility.

Tests
-----

- bpo-31380: Skip test_httpservers test_undecodable_file on macOS: fails on
  APFS.

- bpo-31705: Skip test_socket.test_sha256() on Linux kernel older than 4.5.
  The test fails with ENOKEY on kernel 3.10 (on ppc64le). A fix was merged
  into the kernel 4.5.

- bpo-31174: Fix test_tools.test_unparse: DirectoryTestCase now stores the
  names sample to always test the same files. It prevents false alarms when
  hunting reference leaks.

- bpo-30695: Add the `set_nomemory(start, stop)` and `remove_mem_hooks()`
  functions to the _testcapi module.

Build
-----

- bpo-32059: ``detect_modules()`` in ``setup.py`` now also searches the
  sysroot paths when cross-compiling.

- bpo-31957: Fixes Windows SDK version detection when building for Windows.

- bpo-31609: Fixes quotes in PCbuild/clean.bat

- bpo-31934: Abort the build when building out of a not clean source tree.

- bpo-31926: Fixed Argument Clinic sometimes causing compilation errors when
  there was more than one function and/or method in a .c file with the same
  name.

- bpo-28791: Update Windows builds to use SQLite 3.21.0.

- bpo-28791: Update OS X installer to use SQLite 3.21.0.

- bpo-22140: Prevent double substitution of prefix in python-config.sh.

- bpo-31536: Avoid wholesale rebuild after `make regen-all` if nothing
  changed.

Windows
-------

- bpo-1102: Return ``None`` when ``View.Fetch()`` returns
  ``ERROR_NO_MORE_ITEMS`` instead of raising ``MSIError``. Initial patch by
  Anthony Tuininga.

- bpo-31944: Fixes Modify button in Apps and Features dialog.

macOS
-----

- bpo-31392: Update macOS installer to use OpenSSL 1.0.2m

IDLE
----

- bpo-32207: Improve tk event exception tracebacks in IDLE. When tk event
  handling is driven by IDLE's run loop, a confusing and distracting
  queue.EMPTY traceback context is no longer added to tk event exception
  tracebacks.  The traceback is now the same as when event handling is
  driven by user code.  Patch based on a suggestion by Serhiy Storchaka.

- bpo-32164: Delete unused file idlelib/tabbedpages.py. Use of TabbedPageSet
  in configdialog was replaced by ttk.Notebook.

- bpo-32100: IDLE: Fix old and new bugs in pathbrowser; improve tests. Patch
  mostly by Cheryl Sabella.

- bpo-31858: IDLE -- Restrict shell prompt manipulation to the shell. Editor
  and output windows only see an empty last prompt line.  This simplifies
  the code and fixes a minor bug when newline is inserted. Sys.ps1, if
  present, is read on Shell start-up, but is not set or changed.

- bpo-31860: The font sample in the IDLE configuration dialog is now
  editable. Changes persist while IDLE remains open

- bpo-31836: Test_code_module now passes if run after test_idle, which sets
  ps1. The code module uses sys.ps1 if present or sets it to '>>> ' if not.
  Test_code_module now properly tests both behaviors.  Ditto for ps2.

- bpo-28603: Fix a TypeError that caused a shell restart when printing a
  traceback that includes an exception that is unhashable. Patch by Zane
  Bitter.

- bpo-13802: Use non-Latin characters in the IDLE's Font settings sample.
  Even if one selects a font that defines a limited subset of the unicode
  Basic Multilingual Plane, tcl/tk will use other fonts that define a
  character. The expanded example give users of non-Latin characters a
  better idea of what they might see in IDLE's shell and editors. To make
  room for the expanded sample, frames on the Font tab are re-arranged. The
  Font/Tabs help explains a bit about the additions.

- bpo-31460: Simplify the API of IDLE's Module Browser. Passing a widget
  instead of an flist with a root widget opens the option of creating a
  browser frame that is only part of a window.  Passing a full file name
  instead of pieces assumed to come from a .py file opens the possibility of
  browsing python files that do not end in .py.

- bpo-31649: IDLE - Make _htest, _utest parameters keyword only.

- bpo-31559: Remove test order dependence in idle_test.test_browser.

- bpo-31459: Rename IDLE's module browser from Class Browser to Module
  Browser. The original module-level class and method browser became a
  module browser, with the addition of module-level functions, years ago.
  Nested classes and functions were added yesterday.  For
  back-compatibility, the virtual event <<open-class-browser>>, which
  appears on the Keys tab of the Settings dialog, is not changed. Patch by
  Cheryl Sabella.

- bpo-31500: Default fonts now are scaled on HiDPI displays.

- bpo-1612262: IDLE module browser now shows nested classes and functions.
  Original patches for code and tests by Guilherme Polo and Cheryl Sabella,
  respectively.

Tools/Demos
-----------

- bpo-30722: Make redemo work with Python 3.6 and newer versions. Also,
  remove the ``LOCALE`` option since it doesn't work with string patterns in
  Python 3. Patch by Christoph Sarnowski.

C API
-----

- bpo-20891: Fix PyGILState_Ensure(). When PyGILState_Ensure() is called in
  a non-Python thread before PyEval_InitThreads(), only call
  PyEval_InitThreads() after calling PyThreadState_New() to fix a crash.

- bpo-31532: Fix memory corruption due to allocator mix in getpath.c between
  Py_GetPath() and Py_SetPath()

- bpo-30697: The `PyExc_RecursionErrorInst` singleton is removed and
  `PyErr_NormalizeException()` does not use it anymore. This singleton is
  persistent and its members being never cleared may cause a segfault during
  finalization of the interpreter. See also issue #22898.


What's New in Python 3.6.3 final?
=================================

*Release date: 2017-10-03*

Library
-------

- bpo-31641: Re-allow arbitrary iterables in
  `concurrent.futures.as_completed()`. Fixes regression in 3.6.3rc1.

Build
-----

- bpo-31662: Fix typos in Windows ``uploadrelease.bat`` script. Fix Windows
  Doc build issues in ``Doc/make.bat``.

- bpo-31423: Fix building the PDF documentation with newer versions of
  Sphinx.


What's New in Python 3.6.3 release candidate 1?
===============================================

*Release date: 2017-09-18*

Security
--------

- bpo-29781: SSLObject.version() now correctly returns None when handshake
  over BIO has not been performed yet.

- bpo-30947: Upgrade libexpat embedded copy from version 2.2.1 to 2.2.3 to
  get security fixes.

Core and Builtins
-----------------

- bpo-31471: Fix an assertion failure in `subprocess.Popen()` on Windows, in
  case the env argument has a bad keys() method. Patch by Oren Milman.

- bpo-31418: Fix an assertion failure in `PyErr_WriteUnraisable()` in case
  of an exception with a bad ``__module__`` attribute. Patch by Oren Milman.

- bpo-31416: Fix assertion failures in case of a bad warnings.filters or
  warnings.defaultaction. Patch by Oren Milman.

- bpo-31411: Raise a TypeError instead of SystemError in case
  warnings.onceregistry is not a dictionary. Patch by Oren Milman.

- bpo-31373: Fix several possible instances of undefined behavior due to
  floating-point demotions.

- bpo-30465: Location information (``lineno`` and ``col_offset``) in
  f-strings is now (mostly) correct.  This fixes tools like flake8 from
  showing warnings on the wrong line (typically the first line of the file).

- bpo-31343: Include sys/sysmacros.h for major(), minor(), and makedev().
  GNU C libray plans to remove the functions from sys/types.h.

- bpo-31291: Fix an assertion failure in `zipimport.zipimporter.get_data` on
  Windows, when the return value of ``pathname.replace('/','\\')`` isn't a
  string. Patch by Oren Milman.

- bpo-31271: Fix an assertion failure in the write() method of
  `io.TextIOWrapper`, when the encoder doesn't return a bytes object. Patch
  by Oren Milman.

- bpo-31243: Fix a crash in some methods of `io.TextIOWrapper`, when the
  decoder's state is invalid. Patch by Oren Milman.

- bpo-30721: ``print`` now shows correct usage hint for using Python 2
  redirection syntax.  Patch by Sanyam Khurana.

- bpo-31070: Fix a race condition in importlib _get_module_lock().

- bpo-31095: Fix potential crash during GC caused by ``tp_dealloc`` which
  doesn't call ``PyObject_GC_UnTrack()``.

- bpo-31071: Avoid masking original TypeError in call with * unpacking when
  other arguments are passed.

- bpo-30978: str.format_map() now passes key lookup exceptions through.
  Previously any exception was replaced with a KeyError exception.

- bpo-30808: Use _Py_atomic API for concurrency-sensitive signal state.

- bpo-30876: Relative import from unloaded package now reimports the package
  instead of failing with SystemError.  Relative import from non-package now
  fails with ImportError rather than SystemError.

- bpo-30703: Improve signal delivery. Avoid using Py_AddPendingCall from
  signal handler, to avoid calling signal-unsafe functions. The tests I'm
  adding here fail without the rest of the patch, on Linux and OS X. This
  means our signal delivery logic had defects (some signals could be lost).

- bpo-30765: Avoid blocking in pthread_mutex_lock() when
  PyThread_acquire_lock() is asked not to block.

- bpo-31161: Make sure the 'Missing parentheses' syntax error message is
  only applied to SyntaxError, not to subclasses. Patch by Martijn Pieters.

- bpo-30814: Fixed a race condition when import a submodule from a package.

- bpo-30597: ``print`` now shows expected input in custom error message when
  used as a Python 2 statement. Patch by Sanyam Khurana.

Library
-------

- bpo-31499: xml.etree: Fix a crash when a parser is part of a reference
  cycle.

- bpo-28556: typing.get_type_hints now finds the right globalns for classes
  and modules by default (when no ``globalns`` was specified by the caller).

- bpo-28556: Speed improvements to the ``typing`` module.  Original PRs by
  Ivan Levkivskyi and Mitar.

- bpo-31544: The C accelerator module of ElementTree ignored exceptions
  raised when looking up TreeBuilder target methods in XMLParser().

- bpo-31234: socket.create_connection() now fixes manually a reference
  cycle: clear the variable storing the last exception on success.

- bpo-31457: LoggerAdapter objects can now be nested.

- bpo-31400: Improves SSL error handling to avoid losing error numbers.

- bpo-28958: ssl.SSLContext() now uses OpenSSL error information when a
  context cannot be instantiated.

- bpo-27340: SSLSocket.sendall() now uses memoryview to create slices of
  data. This fixes support for all bytes-like object. It is also more
  efficient and avoids costly copies.

- bpo-31178: Fix string concatenation bug in rare error path in the
  subprocess module

- bpo-31350: Micro-optimize :func:`asyncio._get_running_loop` to become up
  to 10% faster.

- bpo-31170: expat: Update libexpat from 2.2.3 to 2.2.4. Fix copying of
  partial characters for UTF-8 input (libexpat bug 115):
  https://github.com/libexpat/libexpat/issues/115

- bpo-29136: Add TLS 1.3 cipher suites and OP_NO_TLSv1_3.

- bpo-29212: Fix concurrent.futures.thread.ThreadPoolExecutor threads to
  have a non repr() based thread name by default when no thread_name_prefix
  is supplied. They will now identify themselves as
  "ThreadPoolExecutor-y_n".

- bpo-9146: Fix a segmentation fault in _hashopenssl when standard hash
  functions such as md5 are not available in the linked OpenSSL library.  As
  in some special FIPS-140 build environments.

- bpo-27144: The ``map()`` and ``as_completed()`` iterators in
  ``concurrent.futures`` now avoid keeping a reference to yielded objects.

- bpo-10746: Fix ctypes producing wrong :pep:`3118` type codes for integer
  types.

- bpo-22536: The subprocess module now sets the filename when
  FileNotFoundError is raised on POSIX systems due to the executable or cwd
  not being found.

- bpo-31249: concurrent.futures: WorkItem.run() used by ThreadPoolExecutor
  now breaks a reference cycle between an exception object and the WorkItem
  object.

- bpo-31247: xmlrpc.server now explicitly breaks reference cycles when using
  sys.exc_info() in code handling exceptions.

- bpo-30102: The ssl and hashlib modules now call
  OPENSSL_add_all_algorithms_noconf() on OpenSSL < 1.1.0. The function
  detects CPU features and enables optimizations on some CPU architectures
  such as POWER8. Patch is based on research from Gustavo Serra Scalet.

- bpo-31185: Fixed miscellaneous errors in asyncio speedup module.

- bpo-31135: ttk: fix the destroy() method of LabeledScale and OptionMenu
  classes. Call the parent destroy() method even if the used attribute
  doesn't exist. The LabeledScale.destroy() method now also explicitly
  clears label and scale attributes to help the garbage collector to destroy
  all widgets.

- bpo-31107: Fix `copyreg._slotnames()` mangled attribute calculation for
  classes whose name begins with an underscore. Patch by Shane Harvey.

- bpo-31061: Fixed a crash when using asyncio and threads.

- bpo-30502: Fix handling of long oids in ssl.  Based on patch by Christian
  Heimes.

- bpo-30119: ftplib.FTP.putline() now throws ValueError on commands that
  contains CR or LF. Patch by Dong-hee Na.

- bpo-30595: multiprocessing.Queue.get() with a timeout now polls its reader
  in non-blocking mode if it succeeded to acquire the lock but the acquire
  took longer than the timeout.

- bpo-29403: Fix ``unittest.mock``'s autospec to not fail on method-bound
  builtin functions.  Patch by Aaron Gallagher.

- bpo-30961: Fix decrementing a borrowed reference in tracemalloc.

- bpo-25684: Change ``ttk.OptionMenu`` radiobuttons to be unique across
  instances of ``OptionMenu``.

- bpo-30886: Fix multiprocessing.Queue.join_thread(): it now waits until the
  thread completes, even if the thread was started by the same process which
  created the queue.

- bpo-29854: Fix segfault in readline when using readline's history-size
  option.  Patch by Nir Soffer.

- bpo-30319: socket.close() now ignores ECONNRESET error.

- bpo-30828: Fix out of bounds write in
  `asyncio.CFuture.remove_done_callback()`.

- bpo-30807: signal.setitimer() may disable the timer when passed a tiny
  value. Tiny values (such as 1e-6) are valid non-zero values for
  setitimer(), which is specified as taking microsecond-resolution
  intervals. However, on some platform, our conversion routine could convert
  1e-6 into a zero interval, therefore disabling the timer instead of
  (re-)scheduling it.

- bpo-30441: Fix bug when modifying os.environ while iterating over it

- bpo-30532: Fix email header value parser dropping folding white space in
  certain cases.

- bpo-30879: os.listdir() and os.scandir() now emit bytes names when called
  with bytes-like argument.

- bpo-30746: Prohibited the '=' character in environment variable names in
  ``os.putenv()`` and ``os.spawn*()``.

- bpo-29755: Fixed the lgettext() family of functions in the gettext module.
  They now always return bytes.

Documentation
-------------

- bpo-31294: Fix incomplete code snippet in the ZeroMQSocketListener and
  ZeroMQSocketHandler examples and adapt them to Python 3.

- bpo-21649: Add RFC 7525 and Mozilla server side TLS links to SSL
  documentation.

- bpo-30803: Clarify doc on truth value testing. Original patch by Peter
  Thomassen.

Tests
-----

- bpo-31320: Silence traceback in test_ssl

- bpo-25674: Remove sha256.tbs-internet.com ssl test

- bpo-30715: Address ALPN callback changes for OpenSSL 1.1.0f. The latest
  version behaves like OpenSSL 1.0.2 and no longer aborts handshake.

- bpo-30822: regrtest: Exclude tzdata from regrtest --all. When running the
  test suite using --use=all / -u all, exclude tzdata since it makes
  test_datetime too slow (15-20 min on some buildbots) which then times out
  on some buildbots. Fix also regrtest command line parser to allow passing
  -u extralargefile to run test_zipfile64.

Build
-----

- bpo-30854: Fix compile error when compiling --without-threads. Patch by
  Masayuki Yamamoto.

Windows
-------

- bpo-30389: Adds detection of Visual Studio 2017 to distutils on Windows.

- bpo-31340: Change to building with MSVC v141 (included with Visual Studio
  2017)

- bpo-30581: os.cpu_count() now returns the correct number of processors on
  Windows when the number of logical processors is greater than 64.

- bpo-30731: Add a missing xmlns to python.manifest so that it matches the
  schema.

IDLE
----

- bpo-31493: IDLE code context -- fix code update and font update timers.
  Canceling timers prevents a warning message when test_idle completes.

- bpo-31488: IDLE - Update non-key options in former extension classes. When
  applying configdialog changes, call .reload for each feature class. Change
  ParenMatch so updated options affect existing instances attached to
  existing editor windows.

- bpo-31477: IDLE - Improve rstrip entry in doc. Strip trailing whitespace
  strips more than blank spaces.  Multiline string literals are not skipped.

- bpo-31480: IDLE - make tests pass with zzdummy extension disabled by
  default.

- bpo-31421: Document how IDLE runs tkinter programs. IDLE calls tcl/tk
  update in the background in order to make live interaction and
  experimentation with tkinter applications much easier.

- bpo-31414: IDLE -- fix tk entry box tests by deleting first. Adding to an
  int entry is not the same as deleting and inserting because int('') will
  fail.

- bpo-31051: Rearrange IDLE configdialog GenPage into Window, Editor, and
  Help sections.

- bpo-30617: IDLE - Add docstrings and tests for outwin subclass of editor.
  Move some data and functions from the class to module level. Patch by
  Cheryl Sabella.

- bpo-31287: IDLE - Do not modify tkinter.message in test_configdialog.

- bpo-27099: Convert IDLE's built-in 'extensions' to regular features. About
  10 IDLE features were implemented as supposedly optional extensions. Their
  different behavior could be confusing or worse for users and not good for
  maintenance. Hence the conversion. The main difference for users is that
  user configurable key bindings for builtin features are now handled
  uniformly. Now, editing a binding in a keyset only affects its value in
  the keyset. All bindings are defined together in the system-specific
  default keysets in config-extensions.def. All custom keysets are saved as
  a whole in config-extension.cfg.  All take effect as soon as one clicks
  Apply or Ok. The affected events are '<<force-open-completions>>',
  '<<expand-word>>', '<<force-open-calltip>>', '<<flash-paren>>',
  '<<format-paragraph>>', '<<run-module>>', '<<check-module>>', and
  '<<zoom-height>>'.  Any (global) customizations made before 3.6.3 will not
  affect their keyset-specific customization after 3.6.3. and vice versa.
  Initial patch by Charles Wohlganger.

- bpo-31206: IDLE: Factor HighPage(Frame) class from ConfigDialog. Patch by
  Cheryl Sabella.

- bpo-31001: Add tests for configdialog highlight tab.  Patch by Cheryl
  Sabella.

- bpo-31205: IDLE: Factor KeysPage(Frame) class from ConfigDialog.  The
  slightly modified tests continue to pass.  Patch by Cheryl Sabella.

- bpo-31130: IDLE -- stop leaks in test_configdialog. Initial patch by
  Victor Stinner.

- bpo-31002: Add tests for configdialog keys tab. Patch by Cheryl Sabella.

- bpo-19903: IDLE: Calltips use `inspect.signature` instead of
  `inspect.getfullargspec`. This improves calltips for builtins converted to
  use Argument Clinic. Patch by Louie Lu.

- bpo-31083: IDLE - Add an outline of a TabPage class in configdialog.
  Update existing classes to match outline. Initial patch by Cheryl Sabella.

- bpo-31050: Factor GenPage(Frame) class from ConfigDialog. The slightly
  modified tests continue to pass. Patch by Cheryl Sabella.

- bpo-31004: IDLE - Factor FontPage(Frame) class from ConfigDialog. Slightly
  modified tests continue to pass. Fix General tests. Patch mostly by Cheryl
  Sabella.

- bpo-30781: IDLE - Use ttk widgets in ConfigDialog. Patches by Terry Jan
  Reedy and Cheryl Sabella.

- bpo-31060: IDLE - Finish rearranging methods of ConfigDialog Grouping
  methods pertaining to each tab and the buttons will aid writing tests and
  improving the tabs and will enable splitting the groups into classes.

- bpo-30853: IDLE -- Factor a VarTrace class out of ConfigDialog. Instance
  tracers manages pairs consisting of a tk variable and a callback function.
  When tracing is turned on, setting the variable calls the function.  Test
  coverage for the new class is 100%.

- bpo-31003: IDLE: Add more tests for General tab.

- bpo-30993: IDLE - Improve configdialog font page and tests. In
  configdialog: Document causal pathways in create_font_tab docstring.
  Simplify some attribute names. Move set_samples calls to var_changed_font
  (idea from Cheryl Sabella).  Move related functions to positions after the
  create widgets function. In test_configdialog: Fix test_font_set so not
  order dependent.  Fix renamed test_indent_scale so it tests the widget.
  Adjust tests for movement of set_samples call.  Add tests for load
  functions.  Put all font tests in one class and tab indent tests in
  another.  Except for two lines, these tests completely cover the related
  functions.

- bpo-30981: IDLE -- Add more configdialog font page tests.

- bpo-28523: IDLE: replace 'colour' with 'color' in configdialog.

- bpo-30917: Add tests for idlelib.config.IdleConf. Increase coverage from
  46% to 96%. Patch by Louie Lu.

- bpo-30934: Document coverage details for idlelib tests. Add section to
  idlelib/idle-test/README.txt. Include check that branches are taken both
  ways. Exclude IDLE-specific code that does not run during unit tests.

- bpo-30913: IDLE: Document ConfigDialog tk Vars, methods, and widgets in
  docstrings This will facilitate improving the dialog and splitting up the
  class. Original patch by Cheryl Sabella.

- bpo-30899: IDLE: Add tests for ConfigParser subclasses in config. Patch by
  Louie Lu.

- bpo-30881: IDLE: Add docstrings to browser.py. Patch by Cheryl Sabella.

- bpo-30851: IDLE: Remove unused variables in configdialog.  One is a
  duplicate, one is set but cannot be altered by users. Patch by Cheryl
  Sabella.

- bpo-30870: IDLE: In Settings dialog, select font with Up, Down keys as
  well as mouse. Initial patch by Louie Lu.

- bpo-8231: IDLE: call config.IdleConf.GetUserCfgDir only once.

- bpo-30779: IDLE: Factor ConfigChanges class from configdialog, put in
  config; test. * In config, put dump test code in a function; run it and
  unittest in   'if __name__ == '__main__'. * Add class config.ConfigChanges
  based on changes_class_v4.py on bpo issue. * Add class
  test_config.ChangesTest, partly using configdialog_tests_v1.py. * Revise
  configdialog to use ConfigChanges; see tracker msg297804. * Revise
  test_configdialog to match configdialog changes. * Remove configdialog
  functions unused or moved to ConfigChanges. Cheryl Sabella contributed
  parts of the patch.

- bpo-30777: IDLE: configdialog - Add docstrings and fix comments. Patch by
  Cheryl Sabella.

- bpo-30495: IDLE: Improve textview with docstrings, PEP8 names, and more
  tests. Patch by Cheryl Sabella.

- bpo-30723: IDLE: Make several improvements to parenmatch. Add 'parens'
  style to highlight both opener and closer. Make 'default' style, which is
  not default, a synonym for 'opener'. Make time-delay work the same with
  all styles. Add help for config dialog extensions tab, including help for
  parenmatch. Add new tests.  Original patch by Charles Wohlganger.

- bpo-30674: IDLE: add docstrings to grep module. Patch by Cheryl Sabella

- bpo-21519: IDLE's basic custom key entry dialog now detects duplicates
  properly. Original patch by Saimadhav Heblikar.

- bpo-29910: IDLE no longer deletes a character after commenting out a
  region by a key shortcut.  Add ``return 'break'`` for this and other
  potential conflicts between IDLE and default key bindings.

- bpo-30728: Review and change idlelib.configdialog names. Lowercase method
  and attribute names. Replace 'colour' with 'color', expand overly cryptic
  names, delete unneeded underscores. Replace ``import *`` with specific
  imports. Patches by Cheryl Sabella.

- bpo-6739: IDLE: Verify user-entered key sequences by trying to bind them
  with tk. Add tests for all 3 validation functions. Original patch by G
  Polo.  Tests added by Cheryl Sabella.

Tools/Demos
-----------

- bpo-30983: gdb integration commands (py-bt, etc.) work on optimized shared
  builds now, too.  :pep:`523` introduced _PyEval_EvalFrameDefault which
  inlines PyEval_EvalFrameEx on non-debug shared builds.  This broke the
  ability to use py-bt, py-up, and a few other Python-specific gdb
  integrations. The problem is fixed by only looking for
  _PyEval_EvalFrameDefault frames in python-gdb.py.  Original patch by Bruno
  "Polaco" Penteado.


What's New in Python 3.6.2 final?
=================================

*Release date: 2017-07-17*

No changes since release candidate 2



What's New in Python 3.6.2 release candidate 2?
===============================================

*Release date: 2017-07-07*

Security
--------

- bpo-30730: Prevent environment variables injection in subprocess on
  Windows.  Prevent passing other environment variables and command
  arguments.

- bpo-30694: Upgrade expat copy from 2.2.0 to 2.2.1 to get fixes of multiple
  security vulnerabilities including: CVE-2017-9233 (External entity
  infinite loop DoS), CVE-2016-9063 (Integer overflow, re-fix),
  CVE-2016-0718 (Fix regression bugs from 2.2.0's fix to CVE-2016-0718) and
  CVE-2012-0876 (Counter hash flooding with SipHash). Note: the
  CVE-2016-5300 (Use os-specific entropy sources like getrandom) doesn't
  impact Python, since Python already gets entropy from the OS to set the
  expat secret using ``XML_SetHashSalt()``.

- bpo-30500: Fix urllib.parse.splithost() to correctly parse fragments. For
  example, ``splithost('//127.0.0.1#@evil.com/')`` now correctly returns the
  ``127.0.0.1`` host, instead of treating ``@evil.com`` as the host in an
  authentication (``login@host``).


What's New in Python 3.6.2 release candidate 1?
===============================================

*Release date: 2017-06-17*

Security
--------

- bpo-29591: Update expat copy from 2.1.1 to 2.2.0 to get fixes of
  CVE-2016-0718 and CVE-2016-4472. See
  https://sourceforge.net/p/expat/bugs/537/ for more information.

Core and Builtins
-----------------

- bpo-30682: Removed a too-strict assertion that failed for certain
  f-strings, such as eval("f'\\\n'") and eval("f'\\\r'").

- bpo-30604: Move co_extra_freefuncs to not be per-thread to avoid crashes

- bpo-29104: Fixed parsing backslashes in f-strings.

- bpo-27945: Fixed various segfaults with dict when input collections are
  mutated during searching, inserting or comparing.  Based on patches by
  Duane Griffin and Tim Mitchell.

- bpo-25794: Fixed type.__setattr__() and type.__delattr__() for
  non-interned attribute names.  Based on patch by Eryk Sun.

- bpo-30039: If a KeyboardInterrupt happens when the interpreter is in the
  middle of resuming a chain of nested 'yield from' or 'await' calls, it's
  now correctly delivered to the innermost frame.

- bpo-12414: sys.getsizeof() on a code object now returns the sizes which
  includes the code struct and sizes of objects which it references. Patch
  by Dong-hee Na.

- bpo-29949: Fix memory usage regression of set and frozenset object.

- bpo-29935: Fixed error messages in the index() method of tuple, list and
  deque when pass indices of wrong type.

- bpo-29859: Show correct error messages when any of the pthread_* calls in
  thread_pthread.h fails.

- bpo-28876: ``bool(range)`` works even if ``len(range)`` raises
  :exc:`OverflowError`.

- bpo-29600: Fix wrapping coroutine return values in StopIteration.

- bpo-28856: Fix an oversight that %b format for bytes should support
  objects follow the buffer protocol.

- bpo-29714: Fix a regression that bytes format may fail when containing
  zero bytes inside.

- bpo-29478: If max_line_length=None is specified while using the Compat32
  policy, it is no longer ignored.  Patch by Mircea Cosbuc.

Library
-------

- bpo-30616: Functional API of enum allows to create empty enums. Patched by
  Dong-hee Na

- bpo-30038: Fix race condition between signal delivery and wakeup file
  descriptor. Patch by Nathaniel Smith.

- bpo-23894: lib2to3 now recognizes ``rb'...'`` and ``f'...'`` strings.

- bpo-23890: unittest.TestCase.assertRaises() now manually breaks a
  reference cycle to not keep objects alive longer than expected.

- bpo-30149: inspect.signature() now supports callables with
  variable-argument parameters wrapped with partialmethod. Patch by Dong-hee
  Na.

- bpo-30645: Fix path calculation in imp.load_package(), fixing it for cases
  when a package is only shipped with bytecodes. Patch by Alexandru
  Ardelean.

- bpo-29931: Fixed comparison check for ipaddress.ip_interface objects.
  Patch by Sanjay Sundaresan.

- bpo-30605: re.compile() no longer raises a BytesWarning when compiling a
  bytes instance with misplaced inline modifier.  Patch by Roy Williams.

- bpo-24484: Avoid race condition in multiprocessing cleanup (#2159)

- bpo-28994: The traceback no longer displayed for SystemExit raised in a
  callback registered by atexit.

- bpo-30508: Don't log exceptions if Task/Future "cancel()" method was
  called.

- bpo-28556: Updates to typing module: Add generic AsyncContextManager, add
  support for ContextManager on all versions. Original PRs by Jelle Zijlstra
  and Ivan Levkivskyi

- bpo-29870: Fix ssl sockets leaks when connection is aborted in asyncio/ssl
  implementation. Patch by Michaël Sghaïer.

- bpo-29743: Closing transport during handshake process leaks open socket.
  Patch by Nikolay Kim

- bpo-27585: Fix waiter cancellation in asyncio.Lock. Patch by Mathieu
  Sornay.

- bpo-30418: On Windows, subprocess.Popen.communicate() now also ignore
  EINVAL on stdin.write() if the child process is still running but closed
  the pipe.

- bpo-29822: inspect.isabstract() now works during __init_subclass__.  Patch
  by Nate Soares.

- bpo-29581: ABCMeta.__new__ now accepts ``**kwargs``, allowing abstract
  base classes to use keyword parameters in __init_subclass__. Patch by Nate
  Soares.

- bpo-30557: faulthandler now correctly filters and displays exception codes
  on Windows

- bpo-30378: Fix the problem that logging.handlers.SysLogHandler cannot
  handle IPv6 addresses.

- bpo-29960: Preserve generator state when _random.Random.setstate() raises
  an exception. Patch by Bryan Olson.

- bpo-30414: multiprocessing.Queue._feed background running thread do not
  break from main loop on exception.

- bpo-30003: Fix handling escape characters in HZ codec.  Based on patch by
  Ma Lin.

- bpo-30301: Fix AttributeError when using SimpleQueue.empty() under *spawn*
  and *forkserver* start methods.

- bpo-30329: imaplib and poplib now catch the Windows socket WSAEINVAL error
  (code 10022) on shutdown(SHUT_RDWR): An invalid operation was attempted.
  This error occurs sometimes on SSL connections.

- bpo-30375: Warnings emitted when compile a regular expression now always
  point to the line in the user code.  Previously they could point into
  inners of the re module if emitted from inside of groups or conditionals.

- bpo-30048: Fixed ``Task.cancel()`` can be ignored when the task is running
  coroutine and the coroutine returned without any more ``await``.

- bpo-30266: contextlib.AbstractContextManager now supports
  anti-registration by setting __enter__ = None or __exit__ = None,
  following the pattern introduced in bpo-25958. Patch by Jelle Zijlstra.

- bpo-30298: Weaken the condition of deprecation warnings for inline
  modifiers. Now allowed several subsequential inline modifiers at the start
  of the pattern (e.g. ``'(?i)(?s)...'``).  In verbose mode whitespaces and
  comments now are allowed before and between inline modifiers (e.g. ``'(?x)
  (?i) (?s)...'``).

- bpo-29990: Fix range checking in GB18030 decoder.  Original patch by Ma
  Lin.

- bpo-26293: Change resulted because of zipfile breakage. (See also:
  bpo-29094)

- bpo-30243: Removed the __init__ methods of _json's scanner and encoder.
  Misusing them could cause memory leaks or crashes.  Now scanner and
  encoder objects are completely initialized in the __new__ methods.

- bpo-30185: Avoid KeyboardInterrupt tracebacks in forkserver helper process
  when Ctrl-C is received.

- bpo-28556: Various updates to typing module: add typing.NoReturn type, use
  WrapperDescriptorType, minor bug-fixes.  Original PRs by Jim
  Fasarakis-Hilliard and Ivan Levkivskyi.

- bpo-30205: Fix getsockname() for unbound AF_UNIX sockets on Linux.

- bpo-30070: Fixed leaks and crashes in errors handling in the parser
  module.

- bpo-30061: Fixed crashes in IOBase methods __next__() and readlines() when
  readline() or __next__() respectively return non-sizeable object. Fixed
  possible other errors caused by not checking results of PyObject_Size(),
  PySequence_Size(), or PyMapping_Size().

- bpo-30017: Allowed calling the close() method of the zip entry writer
  object multiple times.  Writing to a closed writer now always produces a
  ValueError.

- bpo-30068: _io._IOBase.readlines will check if it's closed first when hint
  is present.

- bpo-29694: Fixed race condition in pathlib mkdir with flags parents=True.
  Patch by Armin Rigo.

- bpo-29692: Fixed arbitrary unchaining of RuntimeError exceptions in
  contextlib.contextmanager.  Patch by Siddharth Velankar.

- bpo-29998: Pickling and copying ImportError now preserves name and path
  attributes.

- bpo-29953: Fixed memory leaks in the replace() method of datetime and time
  objects when pass out of bound fold argument.

- bpo-29942: Fix a crash in itertools.chain.from_iterable when encountering
  long runs of empty iterables.

- bpo-27863: Fixed multiple crashes in ElementTree caused by race conditions
  and wrong types.

- bpo-28699: Fixed a bug in pools in multiprocessing.pool that raising an
  exception at the very first of an iterable may swallow the exception or
  make the program hang. Patch by Davin Potts and Xiang Zhang.

- bpo-25803: Avoid incorrect errors raised by Path.mkdir(exist_ok=True) when
  the OS gives priority to errors such as EACCES over EEXIST.

- bpo-29861: Release references to tasks, their arguments and their results
  as soon as they are finished in multiprocessing.Pool.

- bpo-29884: faulthandler: Restore the old sigaltstack during teardown.
  Patch by Christophe Zeitouny.

- bpo-25455: Fixed crashes in repr of recursive buffered file-like objects.

- bpo-29800: Fix crashes in partial.__repr__ if the keys of partial.keywords
  are not strings.  Patch by Michael Seifert.

- bpo-29742: get_extra_info() raises exception if get called on closed ssl
  transport. Patch by Nikolay Kim.

- bpo-8256: Fixed possible failing or crashing input() if attributes
  "encoding" or "errors" of sys.stdin or sys.stdout are not set or are not
  strings.

- bpo-28298: Fix a bug that prevented array 'Q', 'L' and 'I' from accepting
  big intables (objects that have __int__) as elements.  Patch by Oren
  Milman.

- bpo-28231: The zipfile module now accepts path-like objects for external
  paths.

- bpo-26915: index() and count() methods of collections.abc.Sequence now
  check identity before checking equality when do comparisons.

- bpo-29615: SimpleXMLRPCDispatcher no longer chains KeyError (or any other
  exception) to exception(s) raised in the dispatched methods. Patch by Petr
  Motejlek.

- bpo-30177: path.resolve(strict=False) no longer cuts the path after the
  first element not present in the filesystem.  Patch by Antoine Pietri.

IDLE
----

- bpo-15786: Fix several problems with IDLE's autocompletion box. The
  following should now work: clicking on selection box items; using the
  scrollbar; selecting an item by hitting Return. Hangs on MacOSX should no
  longer happen. Patch by Louie Lu.

- bpo-25514: Add doc subsubsection about IDLE failure to start. Popup
  no-connection message directs users to this section.

- bpo-30642: Fix reference leaks in IDLE tests. Patches by Louie Lu and
  Terry Jan Reedy.

- bpo-30495: Add docstrings for textview.py and use PEP8 names. Patches by
  Cheryl Sabella and Terry Jan Reedy.

- bpo-30290: Help-about: use pep8 names and add tests. Increase coverage to
  100%. Patches by Louie Lu, Cheryl Sabella, and Terry Jan Reedy.

- bpo-30303: Add _utest option to textview; add new tests. Increase coverage
  to 100%. Patches by Louie Lu and Terry Jan Reedy.

C API
-----

- bpo-27867: Function PySlice_GetIndicesEx() no longer replaced with a macro
  if Py_LIMITED_API is not set.

Build
-----

- bpo-29941: Add ``--with-assertions`` configure flag to explicitly enable C
  ``assert()`` checks. Defaults to off. ``--with-pydebug`` implies
  ``--with-assertions``.

- bpo-28787: Fix out-of-tree builds of Python when configured with
  ``--with--dtrace``.

- bpo-29243: Prevent unnecessary rebuilding of Python during ``make test``,
  ``make install`` and some other make targets when configured with
  ``--enable-optimizations``.

- bpo-23404: Don't regenerate generated files based on file modification
  time anymore: the action is now explicit. Replace ``make touch`` with
  ``make regen-all``.

- bpo-29643: Fix ``--enable-optimization`` didn't work.

Documentation
-------------

- bpo-30176: Add missing attribute related constants in curses
  documentation.

- bpo-30052: the link targets for :func:`bytes` and :func:`bytearray` are
  now their respective type definitions, rather than the corresponding
  builtin function entries. Use :ref:`bytes <func-bytes>` and
  :ref:`bytearray <func-bytearray>` to reference the latter. In order to
  ensure this and future cross-reference updates are applied automatically,
  the daily documentation builds now disable the default output caching
  features in Sphinx.

- bpo-26985: Add missing info of code object in inspect documentation.

Tools/Demos
-----------

- bpo-29367: python-gdb.py now supports also ``method-wrapper``
  (``wrapperobject``) objects.

Tests
-----

- bpo-30357: test_thread: setUp() now uses support.threading_setup() and
  support.threading_cleanup() to wait until threads complete to avoid random
  side effects on following tests. Initial patch written by Grzegorz
  Grzywacz.

- bpo-30197: Enhanced functions swap_attr() and swap_item() in the
  test.support module. They now work when delete replaced attribute or item
  inside the with statement.  The old value of the attribute or item (or
  None if it doesn't exist) now will be assigned to the target of the "as"
  clause, if there is one.

Windows
-------

- bpo-30687: Locate msbuild.exe on Windows when building rather than
  vcvarsall.bat

- bpo-30450: The build process on Windows no longer depends on Subversion,
  instead pulling external code from GitHub via a Python script.  If Python
  3.6 is not found on the system (via ``py -3.6``), NuGet is used to
  download a copy of 32-bit Python.


What's New in Python 3.6.1 final?
=================================

*Release date: 2017-03-21*

Core and Builtins
-----------------

- bpo-29723: The ``sys.path[0]`` initialization change for bpo-29139 caused
  a regression by revealing an inconsistency in how sys.path is initialized
  when executing ``__main__`` from a zipfile, directory, or other import
  location. The interpreter now consistently avoids ever adding the import
  location's parent directory to ``sys.path``, and ensures no other
  ``sys.path`` entries are inadvertently modified when inserting the import
  location named on the command line.

Build
-----

- bpo-27593: fix format of git information used in sys.version

- Fix incompatible comment in python.h


What's New in Python 3.6.1 release candidate 1?
===============================================

*Release date: 2017-03-04*

Core and Builtins
-----------------

- bpo-28893: Set correct __cause__ for errors about invalid awaitables
  returned from __aiter__ and __anext__.

- bpo-29683: Fixes to memory allocation in _PyCode_SetExtra.  Patch by Brian
  Coleman.

- bpo-29684: Fix minor regression of PyEval_CallObjectWithKeywords. It
  should raise TypeError when kwargs is not a dict.  But it might cause segv
  when args=NULL and kwargs is not a dict.

- bpo-28598: Support __rmod__ for subclasses of str being called before
  str.__mod__. Patch by Martijn Pieters.

- bpo-29607: Fix stack_effect computation for CALL_FUNCTION_EX. Patch by
  Matthieu Dartiailh.

- bpo-29602: Fix incorrect handling of signed zeros in complex constructor
  for complex subclasses and for inputs having a __complex__ method. Patch
  by Serhiy Storchaka.

- bpo-29347: Fixed possibly dereferencing undefined pointers when creating
  weakref objects.

- bpo-29438: Fixed use-after-free problem in key sharing dict.

- bpo-29319: Prevent RunMainFromImporter overwriting sys.path[0].

- bpo-29337: Fixed possible BytesWarning when compare the code objects.
  Warnings could be emitted at compile time.

- bpo-29327: Fixed a crash when pass the iterable keyword argument to
  sorted().

- bpo-29034: Fix memory leak and use-after-free in os module
  (path_converter).

- bpo-29159: Fix regression in bytes(x) when x.__index__() raises Exception.

- bpo-28932: Do not include <sys/random.h> if it does not exist.

- bpo-25677: Correct the positioning of the syntax error caret for indented
  blocks. Based on patch by Michael Layzell.

- bpo-29000: Fixed bytes formatting of octals with zero padding in alternate
  form.

- bpo-26919: On Android, operating system data is now always encoded/decoded
  to/from UTF-8, instead of the locale encoding to avoid inconsistencies
  with os.fsencode() and os.fsdecode() which are already using UTF-8.

- bpo-28991: functools.lru_cache() was susceptible to an obscure reentrancy
  bug triggerable by a monkey-patched len() function.

- bpo-28739: f-string expressions are no longer accepted as docstrings and
  by ast.literal_eval() even if they do not include expressions.

- bpo-28512: Fixed setting the offset attribute of SyntaxError by
  PyErr_SyntaxLocationEx() and PyErr_SyntaxLocationObject().

- bpo-28918: Fix the cross compilation of xxlimited when Python has been
  built with Py_DEBUG defined.

- bpo-28731: Optimize _PyDict_NewPresized() to create correct size dict.
  Improve speed of dict literal with constant keys up to 30%.

Library
-------

- bpo-29169: Update zlib to 1.2.11.

- bpo-29623: Allow use of path-like object as a single argument in
  ConfigParser.read(). Patch by David Ellis.

- bpo-28963: Fix out of bound iteration in
  asyncio.Future.remove_done_callback implemented in C.

- bpo-29704: asyncio.subprocess.SubprocessStreamProtocol no longer closes
  before all pipes are closed.

- bpo-29271: Fix Task.current_task and Task.all_tasks implemented in C to
  accept None argument as their pure Python implementation.

- bpo-29703: Fix asyncio to support instantiation of new event loops in
  child processes.

- bpo-29376: Fix assertion error in threading._DummyThread.is_alive().

- bpo-28624: Add a test that checks that cwd parameter of Popen() accepts
  PathLike objects.  Patch by Sayan Chowdhury.

- bpo-28518: Start a transaction implicitly before a DML statement. Patch by
  Aviv Palivoda.

- bpo-29532: Altering a kwarg dictionary passed to functools.partial() no
  longer affects a partial object after creation.

- bpo-29110: Fix file object leak in aifc.open() when file is given as a
  filesystem path and is not in valid AIFF format. Patch by Anthony Zhang.

- bpo-28556: Various updates to typing module: typing.Counter,
  typing.ChainMap, improved ABC caching, etc. Original PRs by Jelle
  Zijlstra, Ivan Levkivskyi, Manuel Krebber, and Łukasz Langa.

- bpo-29100: Fix datetime.fromtimestamp() regression introduced in Python
  3.6.0: check minimum and maximum years.

- bpo-29519: Fix weakref spewing exceptions during interpreter shutdown when
  used with a rare combination of multiprocessing and custom codecs.

- bpo-29416: Prevent infinite loop in pathlib.Path.mkdir

- bpo-29444: Fixed out-of-bounds buffer access in the group() method of the
  match object. Based on patch by WGH.

- bpo-29335: Fix subprocess.Popen.wait() when the child process has exited
  to a stopped instead of terminated state (ex: when under ptrace).

- bpo-29290: Fix a regression in argparse that help messages would wrap at
  non-breaking spaces.

- bpo-28735: Fixed the comparison of mock.MagickMock with mock.ANY.

- bpo-29316: Restore the provisional status of typing module, add
  corresponding note to documentation. Patch by Ivan L.

- bpo-29219: Fixed infinite recursion in the repr of uninitialized
  ctypes.CDLL instances.

- bpo-29011: Fix an important omission by adding Deque to the typing module.

- bpo-28969: Fixed race condition in C implementation of
  functools.lru_cache. KeyError could be raised when cached function with
  full cache was simultaneously called from different threads with the same
  uncached arguments.

- bpo-29142: In urllib.request, suffixes in no_proxy environment variable
  with leading dots could match related hostnames again (e.g. .b.c matches
  a.b.c). Patch by Milan Oberkirch.

- bpo-28961: Fix unittest.mock._Call helper: don't ignore the name parameter
  anymore. Patch written by Jiajun Huang.

- bpo-29203: functools.lru_cache() now respects :pep:`468` and preserves the
  order of keyword arguments.  f(a=1, b=2) is now cached separately from
  f(b=2, a=1) since both calls could potentially give different results.

- bpo-15812: inspect.getframeinfo() now correctly shows the first line of a
  context. Patch by Sam Breese.

- bpo-29094: Offsets in a ZIP file created with extern file object and modes
  "w" and "x" now are relative to the start of the file.

- bpo-29085: Allow random.Random.seed() to use high quality OS randomness
  rather than the pid and time.

- bpo-29061: Fixed bug in secrets.randbelow() which would hang when given a
  negative input.  Patch by Brendan Donegan.

- bpo-29079: Prevent infinite loop in pathlib.resolve() on Windows

- bpo-13051: Fixed recursion errors in large or resized
  curses.textpad.Textbox.  Based on patch by Tycho Andersen.

- bpo-29119: Fix weakrefs in the pure python version of
  collections.OrderedDict move_to_end() method. Contributed by Andra
  Bogildea.

- bpo-9770: curses.ascii predicates now work correctly with negative
  integers.

- bpo-28427: old keys should not remove new values from WeakValueDictionary
  when collecting from another thread.

- bpo-28923: Remove editor artifacts from Tix.py.

- bpo-29055: Neaten-up empty population error on random.choice() by
  suppressing the upstream exception.

- bpo-28871: Fixed a crash when deallocate deep ElementTree.

- bpo-19542: Fix bugs in WeakValueDictionary.setdefault() and
  WeakValueDictionary.pop() when a GC collection happens in another thread.

- bpo-20191: Fixed a crash in resource.prlimit() when passing a sequence
  that doesn't own its elements as limits.

- bpo-28779: multiprocessing.set_forkserver_preload() would crash the
  forkserver process if a preloaded module instantiated some multiprocessing
  objects such as locks.

- bpo-28847: dbm.dumb now supports reading read-only files and no longer
  writes the index file when it is not changed.

- bpo-26937: The chown() method of the tarfile.TarFile class does not fail
  now when the grp module cannot be imported, as for example on Android
  platforms.

IDLE
----

- bpo-29071: IDLE colors f-string prefixes (but not invalid ur prefixes).

- bpo-28572: Add 10% to coverage of IDLE's test_configdialog. Update and
  augment description of the configuration system.

Windows
-------

- bpo-29579: Removes readme.txt from the installer

- bpo-29326: Ignores blank lines in ._pth files (Patch by Alexey Izbyshev)

- bpo-28164: Correctly handle special console filenames (patch by Eryk Sun)

- bpo-29409: Implement :pep:`529` for io.FileIO (Patch by Eryk Sun)

- bpo-29392: Prevent crash when passing invalid arguments into msvcrt
  module.

- bpo-25778: winreg does not truncate string correctly (Patch by Eryk Sun)

- bpo-28896: Deprecate WindowsRegistryFinder and disable it by default.

C API
-----

- bpo-27867: Function PySlice_GetIndicesEx() is replaced with a macro if
  Py_LIMITED_API is not set or set to the value between 0x03050400 and
  0x03060000 (not including) or 0x03060100 or higher.

- bpo-29083: Fixed the declaration of some public API functions.
  PyArg_VaParse() and PyArg_VaParseTupleAndKeywords() were not available in
  limited API. PyArg_ValidateKeywordArguments(), PyArg_UnpackTuple() and
  Py_BuildValue() were not available in limited API of version < 3.3 when
  PY_SSIZE_T_CLEAN is defined.

- bpo-29058: All stable API extensions added after Python 3.2 are now
  available only when Py_LIMITED_API is set to the PY_VERSION_HEX value of
  the minimum Python version supporting this API.

Documentation
-------------

- bpo-28929: Link the documentation to its source file on GitHub.

- bpo-25008: Document smtpd.py as effectively deprecated and add a pointer
  to aiosmtpd, a third-party asyncio-based replacement.

- bpo-26355: Add canonical header link on each page to corresponding major
  version of the documentation. Patch by Matthias Bussonnier.

- bpo-29349: Fix Python 2 syntax in code for building the documentation.

Tests
-----

- bpo-28087: Skip test_asyncore and test_eintr poll failures on macOS. Skip
  some tests of select.poll when running on macOS due to unresolved issues
  with the underlying system poll function on some macOS versions.

- bpo-29571: to match the behaviour of the ``re.LOCALE`` flag,
  test_re.test_locale_flag now uses ``locale.getpreferredencoding(False)``
  to determine the candidate encoding for the test regex (allowing it to
  correctly skip the test when the default locale encoding is a multi-byte
  encoding)

- bpo-28950: Disallow -j0 to be combined with -T/-l in regrtest command line
  arguments.

- bpo-28683: Fix the tests that bind() a unix socket and raise
  PermissionError on Android for a non-root user.

- bpo-26939: Add the support.setswitchinterval() function to fix
  test_functools hanging on the Android armv7 qemu emulator.

Build
-----

- bpo-27593: sys.version and the platform module python_build(),
  python_branch(), and python_revision() functions now use git information
  rather than hg when building from a repo.

- bpo-29572: Update Windows build and OS X installers to use OpenSSL 1.0.2k.

- bpo-26851: Set Android compilation and link flags.

- bpo-28768: Fix implicit declaration of function _setmode. Patch by
  Masayuki Yamamoto

- bpo-29080: Removes hard dependency on hg.exe from PCBuild/build.bat

- bpo-23903: Added missed names to PC/python3.def.

- bpo-28762: lockf() is available on Android API level 24, but the F_LOCK
  macro is not defined in android-ndk-r13.

- bpo-28538: Fix the compilation error that occurs because if_nameindex() is
  available on Android API level 24, but the if_nameindex structure is not
  defined.

- bpo-20211: Do not add the directory for installing C header files and the
  directory for installing object code libraries to the cross compilation
  search paths. Original patch by Thomas Petazzoni.

- bpo-28849: Do not define sys.implementation._multiarch on Android.


What's New in Python 3.6.0 final?
=================================

*Release date: 2016-12-23*

No changes since release candidate 2



What's New in Python 3.6.0 release candidate 2?
===============================================

*Release date: 2016-12-16*

Core and Builtins
-----------------

- bpo-28147: Fix a memory leak in split-table dictionaries: setattr() must
  not convert combined table into split table. Patch written by INADA Naoki.

- bpo-28990: Fix asyncio SSL hanging if connection is closed before
  handshake is completed. (Patch by HoHo-Ho)

Tools/Demos
-----------

- bpo-28770: Fix python-gdb.py for fastcalls.

Windows
-------

- bpo-28896: Deprecate WindowsRegistryFinder.

Build
-----

- bpo-28898: Prevent gdb build errors due to HAVE_LONG_LONG redefinition.


What's New in Python 3.6.0 release candidate 1?
===============================================

*Release date: 2016-12-06*

Core and Builtins
-----------------

- bpo-23722: Rather than silently producing a class that doesn't support
  zero-argument ``super()`` in methods, failing to pass the new
  ``__classcell__`` namespace entry up to ``type.__new__`` now results in a
  ``DeprecationWarning`` and a class that supports zero-argument
  ``super()``.

- bpo-28797: Modifying the class __dict__ inside the __set_name__ method of
  a descriptor that is used inside that class no longer prevents calling the
  __set_name__ method of other descriptors.

- bpo-28782: Fix a bug in the implementation ``yield from`` when checking if
  the next instruction is YIELD_FROM. Regression introduced by WORDCODE
  (issue #26647).

Library
-------

- bpo-27030: Unknown escapes in re.sub() replacement template are allowed
  again.  But they still are deprecated and will be disabled in 3.7.

- bpo-28835: Fix a regression introduced in warnings.catch_warnings(): call
  warnings.showwarning() if it was overridden inside the context manager.

- bpo-27172: To assist with upgrades from 2.7, the previously documented
  deprecation of ``inspect.getfullargspec()`` has been reversed. This
  decision may be revisited again after the Python 2.7 branch is no longer
  officially supported.

- bpo-26273: Add new :data:`socket.TCP_CONGESTION` (Linux 2.6.13) and
  :data:`socket.TCP_USER_TIMEOUT` (Linux 2.6.37) constants. Patch written by
  Omar Sandoval.

- bpo-24142: Reading a corrupt config file left configparser in an invalid
  state. Original patch by Florian Höch.

- bpo-28843: Fix asyncio C Task to handle exceptions __traceback__.

C API
-----

- bpo-28808: PyUnicode_CompareWithASCIIString() now never raises exceptions.

Documentation
-------------

- bpo-23722: The data model reference and the porting section in the What's
  New guide now cover the additional ``__classcell__`` handling needed for
  custom metaclasses to fully support :pep:`487` and zero-argument
  ``super()``.

Tools/Demos
-----------

- bpo-28023: Fix python-gdb.py didn't support new dict implementation.


What's New in Python 3.6.0 beta 4?
==================================

*Release date: 2016-11-21*

Core and Builtins
-----------------

- bpo-28532: Show sys.version when -V option is supplied twice.

- bpo-27100: The with-statement now checks for __enter__ before it checks
  for __exit__. This gives less confusing error messages when both methods
  are missing. Patch by Jonathan Ellington.

- bpo-28746: Fix the set_inheritable() file descriptor method on platforms
  that do not have the ioctl FIOCLEX and FIONCLEX commands.

- bpo-26920: Fix not getting the locale's charset upon initializing the
  interpreter, on platforms that do not have langinfo.

- bpo-28648: Fixed crash in Py_DecodeLocale() in debug build on Mac OS X
  when decode astral characters.  Patch by Xiang Zhang.

- bpo-19398: Extra slash no longer added to sys.path components in case of
  empty compile-time PYTHONPATH components.

- bpo-28665: Improve speed of the STORE_DEREF opcode by 40%.

- bpo-28583: PyDict_SetDefault didn't combine split table when needed. Patch
  by Xiang Zhang.

- bpo-27243: Change PendingDeprecationWarning -> DeprecationWarning. As it
  was agreed in the issue, __aiter__ returning an awaitable should result in
  PendingDeprecationWarning in 3.5 and in DeprecationWarning in 3.6.

- bpo-26182: Fix a refleak in code that raises DeprecationWarning.

- bpo-28721: Fix asynchronous generators aclose() and athrow() to handle
  StopAsyncIteration propagation properly.

Library
-------

- bpo-28752: Restored the __reduce__() methods of datetime objects.

- bpo-28727: Regular expression patterns, _sre.SRE_Pattern objects created
  by re.compile(), become comparable (only x==y and x!=y operators). This
  change should fix the issue #18383: don't duplicate warning filters when
  the warnings module is reloaded (thing usually only done in unit tests).

- bpo-20572: The subprocess.Popen.wait method's undocumented endtime
  parameter now raises a DeprecationWarning.

- bpo-25659: In ctypes, prevent a crash calling the from_buffer() and
  from_buffer_copy() methods on abstract classes like Array.

- bpo-19717: Makes Path.resolve() succeed on paths that do not exist. Patch
  by Vajrasky Kok

- bpo-28563: Fixed possible DoS and arbitrary code execution when handle
  plural form selections in the gettext module.  The expression parser now
  supports exact syntax supported by GNU gettext.

- bpo-28387: Fixed possible crash in _io.TextIOWrapper deallocator when the
  garbage collector is invoked in other thread.  Based on patch by Sebastian
  Cufre.

- bpo-28600: Optimize loop.call_soon.

- bpo-28613: Fix get_event_loop() return the current loop if called from
  coroutines/callbacks.

- bpo-28634: Fix asyncio.isfuture() to support unittest.Mock.

- bpo-26081: Fix refleak in _asyncio.Future.__iter__().throw.

- bpo-28639: Fix inspect.isawaitable to always return bool Patch by Justin
  Mayfield.

- bpo-28652: Make loop methods reject socket kinds they do not support.

- bpo-28653: Fix a refleak in functools.lru_cache.

- bpo-28703: Fix asyncio.iscoroutinefunction to handle Mock objects.

- bpo-28704: Fix create_unix_server to support Path-like objects (PEP 519).

- bpo-28720: Add collections.abc.AsyncGenerator.

Documentation
-------------

- bpo-28513: Documented command-line interface of zipfile.

Tests
-----

- bpo-28666: Now test.support.rmtree is able to remove unwritable or
  unreadable directories.

- bpo-23839: Various caches now are cleared before running every test file.

Build
-----

- bpo-10656: Fix out-of-tree building on AIX.  Patch by Tristan Carel and
  Michael Haubenwallner.

- bpo-26359: Rename --with-optimiations to --enable-optimizations.

- bpo-28676: Prevent missing 'getentropy' declaration warning on macOS.
  Patch by Gareth Rees.


What's New in Python 3.6.0 beta 3?
==================================

*Release date: 2016-10-31*

Core and Builtins
-----------------

- bpo-28128: Deprecation warning for invalid str and byte escape sequences
  now prints better information about where the error occurs. Patch by
  Serhiy Storchaka and Eric Smith.

- bpo-28509: dict.update() no longer allocate unnecessary large memory.

- bpo-28426: Fixed potential crash in PyUnicode_AsDecodedObject() in debug
  build.

- bpo-28517: Fixed of-by-one error in the peephole optimizer that caused
  keeping unreachable code.

- bpo-28214: Improved exception reporting for problematic __set_name__
  attributes.

- bpo-23782: Fixed possible memory leak in _PyTraceback_Add() and exception
  loss in PyTraceBack_Here().

- bpo-28471: Fix "Python memory allocator called without holding the GIL"
  crash in socket.setblocking.

Library
-------

- bpo-27517: LZMA compressor and decompressor no longer raise exceptions if
  given empty data twice.  Patch by Benjamin Fogle.

- bpo-28549: Fixed segfault in curses's addch() with ncurses6.

- bpo-28449: tarfile.open() with mode "r" or "r:" now tries to open a tar
  file with compression before trying to open it without compression.
  Otherwise it had 50% chance failed with ignore_zeros=True.

- bpo-23262: The webbrowser module now supports Firefox 36+ and derived
  browsers.  Based on patch by Oleg Broytman.

- bpo-27939: Fixed bugs in tkinter.ttk.LabeledScale and tkinter.Scale caused
  by representing the scale as float value internally in Tk.  tkinter.IntVar
  now works if float value is set to underlying Tk variable.

- bpo-18844: The various ways of specifying weights for random.choices() now
  produce the same result sequences.

- bpo-28255: calendar.TextCalendar().prmonth() no longer prints a space at
  the start of new line after printing a month's calendar.  Patch by Xiang
  Zhang.

- bpo-20491: The textwrap.TextWrapper class now honors non-breaking spaces.
  Based on patch by Kaarle Ritvanen.

- bpo-28353: os.fwalk() no longer fails on broken links.

- bpo-28430: Fix iterator of C implemented asyncio.Future doesn't accept
  non-None value is passed to it.send(val).

- bpo-27025: Generated names for Tkinter widgets now start by the "!" prefix
  for readability.

- bpo-25464: Fixed HList.header_exists() in tkinter.tix module by addin a
  workaround to Tix library bug.

- bpo-28488: shutil.make_archive() no longer adds entry "./" to ZIP archive.

- bpo-25953: re.sub() now raises an error for invalid numerical group
  reference in replacement template even if the pattern is not found in the
  string.  Error message for invalid group reference now includes the group
  index and the position of the reference. Based on patch by SilentGhost.

- bpo-18219: Optimize csv.DictWriter for large number of columns. Patch by
  Mariatta Wijaya.

- bpo-28448: Fix C implemented asyncio.Future didn't work on Windows.

- bpo-28480: Fix error building socket module when multithreading is
  disabled.

- bpo-24452: Make webbrowser support Chrome on Mac OS X.

- bpo-20766: Fix references leaked by pdb in the handling of SIGINT
  handlers.

- bpo-28492: Fix how StopIteration exception is raised in _asyncio.Future.

- bpo-28500: Fix asyncio to handle async gens GC from another thread.

- bpo-26923: Fix asyncio.Gather to refuse being cancelled once all children
  are done. Patch by Johannes Ebke.

- bpo-26796: Don't configure the number of workers for default threadpool
  executor. Initial patch by Hans Lawrenz.

- bpo-28544: Implement asyncio.Task in C.

Windows
-------

- bpo-28522: Fixes mishandled buffer reallocation in getpathp.c

Build
-----

- bpo-28444: Fix missing extensions modules when cross compiling.

- bpo-28208: Update Windows build and OS X installers to use SQLite 3.14.2.

- bpo-28248: Update Windows build and OS X installers to use OpenSSL 1.0.2j.

Tests
-----

- bpo-26944: Fix test_posix for Android where 'id -G' is entirely wrong or
  missing the effective gid.

- bpo-28409: regrtest: fix the parser of command line arguments.


What's New in Python 3.6.0 beta 2?
==================================

*Release date: 2016-10-10*

Core and Builtins
-----------------

- bpo-28183: Optimize and cleanup dict iteration.

- bpo-26081: Added C implementation of asyncio.Future. Original patch by
  Yury Selivanov.

- bpo-28379: Added sanity checks and tests for PyUnicode_CopyCharacters().
  Patch by Xiang Zhang.

- bpo-28376: The type of long range iterator is now registered as Iterator.
  Patch by Oren Milman.

- bpo-28376: Creating instances of range_iterator by calling range_iterator
  type now is deprecated.  Patch by Oren Milman.

- bpo-28376: The constructor of range_iterator now checks that step is not
  0. Patch by Oren Milman.

- bpo-26906: Resolving special methods of uninitialized type now causes
  implicit initialization of the type instead of a fail.

- bpo-18287: PyType_Ready() now checks that tp_name is not NULL. Original
  patch by Niklas Koep.

- bpo-24098: Fixed possible crash when AST is changed in process of
  compiling it.

- bpo-28201: Dict reduces possibility of 2nd conflict in hash table when
  hashes have same lower bits.

- bpo-28350: String constants with null character no longer interned.

- bpo-26617: Fix crash when GC runs during weakref callbacks.

- bpo-27942: String constants now interned recursively in tuples and
  frozensets.

- bpo-21578: Fixed misleading error message when ImportError called with
  invalid keyword args.

- bpo-28203: Fix incorrect type in complex(1.0, {2:3}) error message. Patch
  by Soumya Sharma.

- bpo-28086: Single var-positional argument of tuple subtype was passed
  unscathed to the C-defined function.  Now it is converted to exact tuple.

- bpo-28214: Now __set_name__ is looked up on the class instead of the
  instance.

- bpo-27955: Fallback on reading /dev/urandom device when the getrandom()
  syscall fails with EPERM, for example when blocked by SECCOMP.

- bpo-28192: Don't import readline in isolated mode.

- Upgrade internal unicode databases to Unicode version 9.0.0.

- bpo-28131: Fix a regression in zipimport's compile_source().  zipimport
  should use the same optimization level as the interpreter.

- bpo-28126: Replace Py_MEMCPY with memcpy(). Visual Studio can properly
  optimize memcpy().

- bpo-28120: Fix dict.pop() for splitted dictionary when trying to remove a
  "pending key" (Not yet inserted in split-table). Patch by Xiang Zhang.

- bpo-26182: Raise DeprecationWarning when async and await keywords are used
  as variable/attribute/class/function name.

Library
-------

- bpo-27998: Fixed bytes path support in os.scandir() on Windows. Patch by
  Eryk Sun.

- bpo-28317: The disassembler now decodes FORMAT_VALUE argument.

- bpo-26293: Fixed writing ZIP files that starts not from the start of the
  file.  Offsets in ZIP file now are relative to the start of the archive in
  conforming to the specification.

- bpo-28380: unittest.mock Mock autospec functions now properly support
  assert_called, assert_not_called, and assert_called_once.

- bpo-27181: remove statistics.geometric_mean and defer until 3.7.

- bpo-28229: lzma module now supports pathlib.

- bpo-28321: Fixed writing non-BMP characters with binary format in
  plistlib.

- bpo-28225: bz2 module now supports pathlib.  Initial patch by Ethan
  Furman.

- bpo-28227: gzip now supports pathlib.  Patch by Ethan Furman.

- bpo-27358: Optimized merging var-keyword arguments and improved error
  message when passing a non-mapping as a var-keyword argument.

- bpo-28257: Improved error message when passing a non-iterable as a
  var-positional argument.  Added opcode BUILD_TUPLE_UNPACK_WITH_CALL.

- bpo-28322: Fixed possible crashes when unpickle itertools objects from
  incorrect pickle data.  Based on patch by John Leitch.

- bpo-28228: imghdr now supports pathlib.

- bpo-28226: compileall now supports pathlib.

- bpo-28314: Fix function declaration (C flags) for the getiterator() method
  of xml.etree.ElementTree.Element.

- bpo-28148: Stop using localtime() and gmtime() in the time module.
  Introduced platform independent _PyTime_localtime API that is similar to
  POSIX localtime_r, but available on all platforms.  Patch by Ed Schouten.

- bpo-28253: Fixed calendar functions for extreme months: 0001-01 and
  9999-12. Methods itermonthdays() and itermonthdays2() are reimplemented so
  that they don't call itermonthdates() which can cause datetime.date
  under/overflow.

- bpo-28275: Fixed possible use after free in the decompress() methods of
  the LZMADecompressor and BZ2Decompressor classes. Original patch by John
  Leitch.

- bpo-27897: Fixed possible crash in sqlite3.Connection.create_collation()
  if pass invalid string-like object as a name.  Patch by Xiang Zhang.

- bpo-18844: random.choices() now has k as a keyword-only argument to
  improve the readability of common cases and come into line with the
  signature used in other languages.

- bpo-18893: Fix invalid exception handling in Lib/ctypes/macholib/dyld.py.
  Patch by Madison May.

- bpo-27611: Fixed support of default root window in the tkinter.tix module.
  Added the master parameter in the DisplayStyle constructor.

- bpo-27348: In the traceback module, restore the formatting of exception
  messages like "Exception: None".  This fixes a regression introduced in
  3.5a2.

- bpo-25651: Allow falsy values to be used for msg parameter of subTest().

- bpo-27778: Fix a memory leak in os.getrandom() when the getrandom() is
  interrupted by a signal and a signal handler raises a Python exception.

- bpo-28200: Fix memory leak on Windows in the os module (fix
  path_converter() function).

- bpo-25400: RobotFileParser now correctly returns default values for
  crawl_delay and request_rate.  Initial patch by Peter Wirtz.

- bpo-27932: Prevent memory leak in win32_ver().

- Fix UnboundLocalError in socket._sendfile_use_sendfile.

- bpo-28075: Check for ERROR_ACCESS_DENIED in Windows implementation of
  os.stat().  Patch by Eryk Sun.

- bpo-22493: Warning message emitted by using inline flags in the middle of
  regular expression now contains a (truncated) regex pattern. Patch by Tim
  Graham.

- bpo-25270: Prevent codecs.escape_encode() from raising SystemError when an
  empty bytestring is passed.

- bpo-28181: Get antigravity over HTTPS. Patch by Kaartic Sivaraam.

- bpo-25895: Enable WebSocket URL schemes in urllib.parse.urljoin. Patch by
  Gergely Imreh and Markus Holtermann.

- bpo-28114: Fix a crash in parse_envlist() when env contains byte strings.
  Patch by Eryk Sun.

- bpo-27599: Fixed buffer overrun in binascii.b2a_qp() and
  binascii.a2b_qp().

- bpo-27906: Fix socket accept exhaustion during high TCP traffic. Patch by
  Kevin Conway.

- bpo-28174: Handle when SO_REUSEPORT isn't properly supported. Patch by
  Seth Michael Larson.

- bpo-26654: Inspect functools.partial in asyncio.Handle.__repr__. Patch by
  iceboy.

- bpo-26909: Fix slow pipes IO in asyncio. Patch by INADA Naoki.

- bpo-28176: Fix callbacks race in asyncio.SelectorLoop.sock_connect.

- bpo-27759: Fix selectors incorrectly retain invalid file descriptors.
  Patch by Mark Williams.

- bpo-28368: Refuse monitoring processes if the child watcher has no loop
  attached. Patch by Vincent Michel.

- bpo-28369: Raise RuntimeError when transport's FD is used with add_reader,
  add_writer, etc.

- bpo-28370: Speedup asyncio.StreamReader.readexactly. Patch by Коренберг
  Марк.

- bpo-28371: Deprecate passing asyncio.Handles to run_in_executor.

- bpo-28372: Fix asyncio to support formatting of non-python coroutines.

- bpo-28399: Remove UNIX socket from FS before binding. Patch by Коренберг
  Марк.

- bpo-27972: Prohibit Tasks to await on themselves.

Windows
-------

- bpo-28402: Adds signed catalog files for stdlib on Windows.

- bpo-28333: Enables Unicode for ps1/ps2 and input() prompts. (Patch by Eryk
  Sun)

- bpo-28251: Improvements to help manuals on Windows.

- bpo-28110: launcher.msi has different product codes between 32-bit and
  64-bit

- bpo-28161: Opening CON for write access fails

- bpo-28162: WindowsConsoleIO readall() fails if first line starts with
  Ctrl+Z

- bpo-28163: WindowsConsoleIO fileno() passes wrong flags to _open_osfhandle

- bpo-28164: _PyIO_get_console_type fails for various paths

- bpo-28137: Renames Windows path file to ._pth

- bpo-28138: Windows ._pth file should allow import site

C API
-----

- bpo-28426: Deprecated undocumented functions PyUnicode_AsEncodedObject(),
  PyUnicode_AsDecodedObject(), PyUnicode_AsDecodedUnicode() and
  PyUnicode_AsEncodedUnicode().

Build
-----

- bpo-28258: Fixed build with Estonian locale (python-config and distclean
  targets in Makefile).  Patch by Arfrever Frehtes Taifersar Arahesis.

- bpo-26661: setup.py now detects system libffi with multiarch wrapper.

- bpo-15819: Remove redundant include search directory option for building
  outside the source tree.

Tests
-----

- bpo-28217: Adds _testconsole module to test console input.


What's New in Python 3.6.0 beta 1?
==================================

*Release date: 2016-09-12*

Core and Builtins
-----------------

- bpo-23722: The __class__ cell used by zero-argument super() is now
  initialized from type.__new__ rather than __build_class__, so class
  methods relying on that will now work correctly when called from metaclass
  methods during class creation. Patch by Martin Teichmann.

- bpo-25221: Fix corrupted result from PyLong_FromLong(0) when Python is
  compiled with NSMALLPOSINTS = 0.

- bpo-27080: Implement formatting support for :pep:`515`.  Initial patch by
  Chris Angelico.

- bpo-27199: In tarfile, expose copyfileobj bufsize to improve throughput.
  Patch by Jason Fried.

- bpo-27948: In f-strings, only allow backslashes inside the braces (where
  the expressions are).  This is a breaking change from the 3.6 alpha
  releases, where backslashes are allowed anywhere in an f-string.  Also,
  require that expressions inside f-strings be enclosed within literal
  braces, and not escapes like ``f'\x7b"hi"\x7d'``.

- bpo-28046: Remove platform-specific directories from sys.path.

- bpo-28071: Add early-out for differencing from an empty set.

- bpo-25758: Prevents zipimport from unnecessarily encoding a filename
  (patch by Eryk Sun)

- bpo-25856: The __module__ attribute of extension classes and functions now
  is interned. This leads to more compact pickle data with protocol 4.

- bpo-27213: Rework CALL_FUNCTION* opcodes to produce shorter and more
  efficient bytecode. Patch by Demur Rumed, design by Serhiy Storchaka,
  reviewed by Serhiy Storchaka and Victor Stinner.

- bpo-26331: Implement tokenizing support for :pep:`515`. Patch by Georg
  Brandl.

- bpo-27999: Make "global after use" a SyntaxError, and ditto for nonlocal.
  Patch by Ivan Levkivskyi.

- bpo-28003: Implement :pep:`525` -- Asynchronous Generators.

- bpo-27985: Implement :pep:`526` -- Syntax for Variable Annotations. Patch
  by Ivan Levkivskyi.

- bpo-26058: Add a new private version to the builtin dict type, incremented
  at each dictionary creation and at each dictionary change. Implementation
  of the PEP 509.

- bpo-27364: A backslash-character pair that is not a valid escape sequence
  now generates a DeprecationWarning.  Patch by Emanuel Barry.

- bpo-27350: `dict` implementation is changed like PyPy. It is more compact
  and preserves insertion order. (Concept developed by Raymond Hettinger and
  patch by Inada Naoki.)

- bpo-27911: Remove unnecessary error checks in
  ``exec_builtin_or_dynamic()``.

- bpo-27078: Added BUILD_STRING opcode.  Optimized f-strings evaluation.

- bpo-17884: Python now requires systems with inttypes.h and stdint.h

- bpo-27961: Require platforms to support ``long long``. Python hasn't
  compiled without ``long long`` for years, so this is basically a
  formality.

- bpo-27355: Removed support for Windows CE.  It was never finished, and
  Windows CE is no longer a relevant platform for Python.

- Implement :pep:`523`.

- bpo-27870: A left shift of zero by a large integer no longer attempts to
  allocate large amounts of memory.

- bpo-25402: In int-to-decimal-string conversion, improve the estimate of
  the intermediate memory required, and remove an unnecessarily strict
  overflow check. Patch by Serhiy Storchaka.

- bpo-27214: In long_invert, be more careful about modifying object returned
  by long_add, and remove an unnecessary check for small longs. Thanks Oren
  Milman for analysis and patch.

- bpo-27506: Support passing the bytes/bytearray.translate() "delete"
  argument by keyword.

- bpo-27812: Properly clear out a generator's frame's backreference to the
  generator to prevent crashes in frame.clear().

- bpo-27811: Fix a crash when a coroutine that has not been awaited is
  finalized with warnings-as-errors enabled.

- bpo-27587: Fix another issue found by PVS-Studio: Null pointer check after
  use of 'def' in _PyState_AddModule(). Initial patch by Christian Heimes.

- bpo-27792: The modulo operation applied to ``bool`` and other ``int``
  subclasses now always returns an ``int``. Previously the return type
  depended on the input values. Patch by Xiang Zhang.

- bpo-26984: int() now always returns an instance of exact int.

- bpo-25604: Fix a minor bug in integer true division; this bug could
  potentially have caused off-by-one-ulp results on platforms with
  unreliable ldexp implementations.

- bpo-24254: Make class definition namespace ordered by default.

- bpo-27662: Fix an overflow check in ``List_New``: the original code was
  checking against ``Py_SIZE_MAX`` instead of the correct upper bound of
  ``Py_SSIZE_T_MAX``. Patch by Xiang Zhang.

- bpo-27782: Multi-phase extension module import now correctly allows the
  ``m_methods`` field to be used to add module level functions to instances
  of non-module types returned from ``Py_create_mod``. Patch by Xiang Zhang.

- bpo-27936: The round() function accepted a second None argument for some
  types but not for others.  Fixed the inconsistency by accepting None for
  all numeric types.

- bpo-27487: Warn if a submodule argument to "python -m" or
  runpy.run_module() is found in sys.modules after parent packages are
  imported, but before the submodule is executed.

- bpo-27157: Make only type() itself accept the one-argument form. Patch by
  Eryk Sun and Emanuel Barry.

- bpo-27558: Fix a SystemError in the implementation of "raise" statement.
  In a brand new thread, raise a RuntimeError since there is no active
  exception to reraise. Patch written by Xiang Zhang.

- bpo-28008: Implement :pep:`530` -- asynchronous comprehensions.

- bpo-27942: Fix memory leak in codeobject.c

Library
-------

- bpo-28732: Fix crash in os.spawnv() with no elements in args

- bpo-28485: Always raise ValueError for negative
  compileall.compile_dir(workers=...) parameter, even when multithreading is
  unavailable.

- bpo-28037: Use sqlite3_get_autocommit() instead of setting
  Connection->inTransaction manually.

- bpo-25283: Attributes tm_gmtoff and tm_zone are now available on all
  platforms in the return values of time.localtime() and time.gmtime().

- bpo-24454: Regular expression match object groups are now accessible using
  __getitem__. "mo[x]" is equivalent to "mo.group(x)".

- bpo-10740: sqlite3 no longer implicitly commit an open transaction before
  DDL statements.

- bpo-17941: Add a *module* parameter to collections.namedtuple().

- bpo-22493: Inline flags now should be used only at the start of the
  regular expression. Deprecation warning is emitted if uses them in the
  middle of the regular expression.

- bpo-26885: xmlrpc now supports unmarshalling additional data types used by
  Apache XML-RPC implementation for numerics and None.

- bpo-28070: Fixed parsing inline verbose flag in regular expressions.

- bpo-19500: Add client-side SSL session resumption to the ssl module.

- bpo-28022: Deprecate ssl-related arguments in favor of SSLContext. The
  deprecation include manual creation of SSLSocket and certfile/keyfile (or
  similar) in ftplib, httplib, imaplib, smtplib, poplib and urllib.

- bpo-28043: SSLContext has improved default settings: OP_NO_SSLv2,
  OP_NO_SSLv3, OP_NO_COMPRESSION, OP_CIPHER_SERVER_PREFERENCE,
  OP_SINGLE_DH_USE, OP_SINGLE_ECDH_USE and HIGH ciphers without MD5.

- bpo-24693: Changed some RuntimeError's in the zipfile module to more
  appropriate types. Improved some error messages and debugging output.

- bpo-17909: ``json.load`` and ``json.loads`` now support binary input
  encoded as UTF-8, UTF-16 or UTF-32. Patch by Serhiy Storchaka.

- bpo-27137: the pure Python fallback implementation of
  ``functools.partial`` now matches the behaviour of its accelerated C
  counterpart for subclassing, pickling and text representation purposes.
  Patch by Emanuel Barry and Serhiy Storchaka.

- Fix possible integer overflows and crashes in the mmap module with unusual
  usage patterns.

- bpo-1703178: Fix the ability to pass the --link-objects option to the
  distutils build_ext command.

- bpo-28019: itertools.count() no longer rounds non-integer step in range
  between 1.0 and 2.0 to 1.

- bpo-18401: Pdb now supports the 'readrc' keyword argument to control
  whether .pdbrc files should be read.  Patch by Martin Matusiak and Sam
  Kimbrel.

- bpo-25969: Update the lib2to3 grammar to handle the unpacking
  generalizations added in 3.5.

- bpo-14977: mailcap now respects the order of the lines in the mailcap
  files ("first match"), as required by RFC 1542.  Patch by Michael Lazar.

- bpo-28082: Convert re flag constants to IntFlag.

- bpo-28025: Convert all ssl module constants to IntEnum and IntFlags.
  SSLContext properties now return flags and enums.

- bpo-23591: Add Flag, IntFlag, and auto() to enum module.

- bpo-433028: Added support of modifier spans in regular expressions.

- bpo-24594: Validates persist parameter when opening MSI database

- bpo-17582: xml.etree.ElementTree nows preserves whitespaces in attributes
  (Patch by Duane Griffin.  Reviewed and approved by Stefan Behnel.)

- bpo-28047: Fixed calculation of line length used for the base64 CTE in the
  new email policies.

- bpo-27576: Fix call order in OrderedDict.__init__().

- email.generator.DecodedGenerator now supports the policy keyword.

- bpo-28027: Remove undocumented modules from ``Lib/plat-*``: IN, CDROM,
  DLFCN, TYPES, CDIO, and STROPTS.

- bpo-27445: Don't pass str(_charset) to MIMEText.set_payload(). Patch by
  Claude Paroz.

- bpo-24277: The new email API is no longer provisional, and the docs have
  been reorganized and rewritten to emphasize the new API.

- bpo-22450: urllib now includes an ``Accept: */*`` header among the default
  headers. This makes the results of REST API requests more consistent and
  predictable especially when proxy servers are involved.

- lib2to3.pgen3.driver.load_grammar() now creates a stable cache file
  between runs given the same Grammar.txt input regardless of the hash
  randomization setting.

- bpo-28005: Allow ImportErrors in encoding implementation to propagate.

- bpo-26667: Support path-like objects in importlib.util.

- bpo-27570: Avoid zero-length memcpy() etc calls with null source pointers
  in the "ctypes" and "array" modules.

- bpo-22233: Break email header lines *only* on the RFC specified CR and LF
  characters, not on arbitrary unicode line breaks.  This also fixes a bug
  in HTTP header parsing.

- bpo-27331: The email.mime classes now all accept an optional policy
  keyword.

- bpo-27988: Fix email iter_attachments incorrect mutation of payload list.

- bpo-16113: Add SHA-3 and SHAKE support to hashlib module.

- Eliminate a tautological-pointer-compare warning in _scproxy.c.

- bpo-27776: The :func:`os.urandom` function does now block on Linux 3.17
  and newer until the system urandom entropy pool is initialized to increase
  the security. This change is part of the :pep:`524`.

- bpo-27778: Expose the Linux ``getrandom()`` syscall as a new
  :func:`os.getrandom` function. This change is part of the :pep:`524`.

- bpo-27691: Fix ssl module's parsing of GEN_RID subject alternative name
  fields in X.509 certs.

- bpo-18844: Add random.choices().

- bpo-25761: Improved error reporting about truncated pickle data in C
  implementation of unpickler.  UnpicklingError is now raised instead of
  AttributeError and ValueError in some cases.

- bpo-26798: Add BLAKE2 (blake2b and blake2s) to hashlib.

- bpo-26032: Optimized globbing in pathlib by using os.scandir(); it is now
  about 1.5--4 times faster.

- bpo-25596: Optimized glob() and iglob() functions in the glob module; they
  are now about 3--6 times faster.

- bpo-27928: Add scrypt (password-based key derivation function) to hashlib
  module (requires OpenSSL 1.1.0).

- bpo-27850: Remove 3DES from ssl module's default cipher list to counter
  measure sweet32 attack (CVE-2016-2183).

- bpo-27766: Add ChaCha20 Poly1305 to ssl module's default cipher list.
  (Required OpenSSL 1.1.0 or LibreSSL).

- bpo-25387: Check return value of winsound.MessageBeep.

- bpo-27866: Add SSLContext.get_ciphers() method to get a list of all
  enabled ciphers.

- bpo-27744: Add AF_ALG (Linux Kernel crypto) to socket module.

- bpo-26470: Port ssl and hashlib module to OpenSSL 1.1.0.

- bpo-11620: Fix support for SND_MEMORY in winsound.PlaySound.  Based on a
  patch by Tim Lesher.

- bpo-11734: Add support for IEEE 754 half-precision floats to the struct
  module. Based on a patch by Eli Stevens.

- bpo-27919: Deprecated ``extra_path`` distribution option in distutils
  packaging.

- bpo-23229: Add new ``cmath`` constants: ``cmath.inf`` and ``cmath.nan`` to
  match ``math.inf`` and ``math.nan``, and also ``cmath.infj`` and
  ``cmath.nanj`` to match the format used by complex repr.

- bpo-27842: The csv.DictReader now returns rows of type OrderedDict.
  (Contributed by Steve Holden.)

- Remove support for passing a file descriptor to os.access. It never worked
  but previously didn't raise.

- bpo-12885: Fix error when distutils encounters symlink.

- bpo-27881: Fixed possible bugs when setting
  sqlite3.Connection.isolation_level. Based on patch by Xiang Zhang.

- bpo-27861: Fixed a crash in sqlite3.Connection.cursor() when a factory
  creates not a cursor.  Patch by Xiang Zhang.

- bpo-19884: Avoid spurious output on OS X with Gnu Readline.

- bpo-27706: Restore deterministic behavior of random.Random().seed() for
  string seeds using seeding version 1.  Allows sequences of calls to
  random() to exactly match those obtained in Python 2. Patch by Nofar
  Schnider.

- bpo-10513: Fix a regression in Connection.commit().  Statements should not
  be reset after a commit.

- bpo-12319: Chunked transfer encoding support added to
  http.client.HTTPConnection requests.  The
  urllib.request.AbstractHTTPHandler class does not enforce a Content-Length
  header any more.  If a HTTP request has a file or iterable body, but no
  Content-Length header, the library now falls back to use chunked
  transfer-encoding.

- A new version of typing.py from https://github.com/python/typing: -
  Collection (only for 3.6) (Issue #27598) - Add FrozenSet to __all__
  (upstream #261) - fix crash in _get_type_vars() (upstream #259) - Remove
  the dict constraint in ForwardRef._eval_type (upstream #252)

- bpo-27832: Make ``_normalize`` parameter to ``Fraction`` constructor
  keyword-only, so that ``Fraction(2, 3, 4)`` now raises ``TypeError``.

- bpo-27539: Fix unnormalised ``Fraction.__pow__`` result in the case of
  negative exponent and negative base.

- bpo-21718: cursor.description is now available for queries using CTEs.

- bpo-27819: In distutils sdists, simply produce the "gztar" (gzipped tar
  format) distributions on all platforms unless "formats" is supplied.

- bpo-2466: posixpath.ismount now correctly recognizes mount points which
  the user does not have permission to access.

- bpo-9998: On Linux, ctypes.util.find_library now looks in LD_LIBRARY_PATH
  for shared libraries.

- bpo-27573: exit message for code.interact is now configurable.

- bpo-27930: Improved behaviour of logging.handlers.QueueListener. Thanks to
  Paulo Andrade and Petr Viktorin for the analysis and patch.

- bpo-6766: Distributed reference counting added to multiprocessing to
  support nesting of shared values / proxy objects.

- bpo-21201: Improves readability of multiprocessing error message.  Thanks
  to Wojciech Walczak for patch.

- asyncio: Add set_protocol / get_protocol to Transports.

- bpo-27456: asyncio: Set TCP_NODELAY by default.

IDLE
----

- bpo-15308: Add 'interrupt execution' (^C) to Shell menu. Patch by Roger
  Serwy, updated by Bayard Randel.

- bpo-27922: Stop IDLE tests from 'flashing' gui widgets on the screen.

- bpo-27891: Consistently group and sort imports within idlelib modules.

- bpo-17642: add larger font sizes for classroom projection.

- Add version to title of IDLE help window.

- bpo-25564: In section on IDLE -- console differences, mention that using
  exec means that __builtins__ is defined for each statement.

- bpo-27821: Fix 3.6.0a3 regression that prevented custom key sets from
  being selected when no custom theme was defined.

C API
-----

- bpo-26900: Excluded underscored names and other private API from limited
  API.

- bpo-26027: Add support for path-like objects in PyUnicode_FSConverter() &
  PyUnicode_FSDecoder().

Tests
-----

- bpo-27427: Additional tests for the math module. Patch by Francisco Couzo.

- bpo-27953: Skip math and cmath tests that fail on OS X 10.4 due to a poor
  libm implementation of tan.

- bpo-26040: Improve test_math and test_cmath coverage and rigour. Patch by
  Jeff Allen.

- bpo-27787: Call gc.collect() before checking each test for "dangling
  threads", since the dangling threads are weak references.

Build
-----

- bpo-27566: Fix clean target in freeze makefile (patch by Lisa Roach)

- bpo-27705: Update message in validate_ucrtbase.py

- bpo-27976: Deprecate building _ctypes with the bundled copy of libffi on
  non-OSX UNIX platforms.

- bpo-27983: Cause lack of llvm-profdata tool when using clang as required
  for PGO linking to be a configure time error rather than make time when
  ``--with-optimizations`` is enabled.  Also improve our ability to find the
  llvm-profdata tool on MacOS and some Linuxes.

- bpo-21590: Support for DTrace and SystemTap probes.

- bpo-26307: The profile-opt build now applies PGO to the built-in modules.

- bpo-26359: Add the --with-optimizations flag to turn on LTO and PGO build
  support when available.

- bpo-27917: Set platform triplets for Android builds.

- bpo-25825: Update references to the $(LIBPL) installation path on AIX.
  This path was changed in 3.2a4.

- Update OS X installer to use SQLite 3.14.1 and XZ 5.2.2.

- bpo-21122: Fix LTO builds on OS X.

- bpo-17128: Build OS X installer with a private copy of OpenSSL. Also
  provide a sample Install Certificates command script to install a set of
  root certificates from the third-party certifi module.

Tools/Demos
-----------

- bpo-27952: Get Tools/scripts/fixcid.py working with Python 3 and the
  current "re" module, avoid invalid Python backslash escapes, and fix a bug
  parsing escaped C quote signs.

Windows
-------

- bpo-28065: Update xz dependency to 5.2.2 and build it from source.

- bpo-25144: Ensures TargetDir is set before continuing with custom install.

- bpo-1602: Windows console doesn't input or print Unicode (PEP 528)

- bpo-27781: Change file system encoding on Windows to UTF-8 (PEP 529)

- bpo-27731: Opt-out of MAX_PATH on Windows 10

- bpo-6135: Adds encoding and errors parameters to subprocess.

- bpo-27959: Adds oem encoding, alias ansi to mbcs, move aliasmbcs to codec
  lookup.

- bpo-27982: The functions of the winsound module now accept keyword
  arguments.

- bpo-20366: Build full text search support into SQLite on Windows.

- bpo-27756: Adds new icons for Python files and processes on Windows.
  Designs by Cherry Wang.

- bpo-27883: Update sqlite to 3.14.1.0 on Windows.


What's New in Python 3.6.0 alpha 4?
===================================

*Release date: 2016-08-15*

Core and Builtins
-----------------

- bpo-27704: Optimized creating bytes and bytearray from byte-like objects
  and iterables. Speed up to 3 times for short objects.  Original patch by
  Naoki Inada.

- bpo-26823: Large sections of repeated lines in tracebacks are now
  abbreviated as "[Previous line repeated {count} more times]" by the
  builtin traceback rendering. Patch by Emanuel Barry.

- bpo-27574: Decreased an overhead of parsing keyword arguments in functions
  implemented with using Argument Clinic.

- bpo-22557: Now importing already imported modules is up to 2.5 times
  faster.

- bpo-17596: Include <wincrypt.h> to help with Min GW building.

- bpo-17599: On Windows, rename the privately defined REPARSE_DATA_BUFFER
  structure to avoid conflicting with the definition from Min GW.

- bpo-27507: Add integer overflow check in bytearray.extend().  Patch by
  Xiang Zhang.

- bpo-27581: Don't rely on wrapping for overflow check in
  PySequence_Tuple().  Patch by Xiang Zhang.

- bpo-1621: Avoid signed integer overflow in list and tuple operations.
  Patch by Xiang Zhang.

- bpo-27419: Standard __import__() no longer look up "__import__" in globals
  or builtins for importing submodules or "from import".  Fixed a crash if
  raise a warning about unabling to resolve package from __spec__ or
  __package__.

- bpo-27083: Respect the PYTHONCASEOK environment variable under Windows.

- bpo-27514: Make having too many statically nested blocks a SyntaxError
  instead of SystemError.

- bpo-27366: Implemented :pep:`487` (Simpler customization of class
  creation). Upon subclassing, the __init_subclass__ classmethod is called
  on the base class. Descriptors are initialized with __set_name__ after
  class creation.

Library
-------

- bpo-26027: Add :pep:`519`/__fspath__() support to the os and os.path
  modules. Includes code from Jelle Zijlstra. (See also: bpo-27524)

- bpo-27598: Add Collections to collections.abc. Patch by Ivan Levkivskyi,
  docs by Neil Girdhar.

- bpo-25958: Support "anti-registration" of special methods from various
  ABCs, like __hash__, __iter__ or __len__.  All these (and several more)
  can be set to None in an implementation class and the behavior will be as
  if the method is not defined at all. (Previously, this mechanism existed
  only for __hash__, to make mutable classes unhashable.)  Code contributed
  by Andrew Barnert and Ivan Levkivskyi.

- bpo-16764: Support keyword arguments to zlib.decompress().  Patch by Xiang
  Zhang.

- bpo-27736: Prevent segfault after interpreter re-initialization due to ref
  count problem introduced in code for Issue #27038 in 3.6.0a3. Patch by
  Xiang Zhang.

- bpo-25628: The *verbose* and *rename* parameters for
  collections.namedtuple are now keyword-only.

- bpo-12345: Add mathematical constant tau to math and cmath. See also
  :pep:`628`.

- bpo-26823: traceback.StackSummary.format now abbreviates large sections of
  repeated lines as "[Previous line repeated {count} more times]" (this
  change then further affects other traceback display operations in the
  module). Patch by Emanuel Barry.

- bpo-27664: Add to concurrent.futures.thread.ThreadPoolExecutor() the
  ability to specify a thread name prefix.

- bpo-27181: Add geometric_mean and harmonic_mean to statistics module.

- bpo-27573: code.interact now prints an message when exiting.

- bpo-6422: Add autorange method to timeit.Timer objects.

- bpo-27773: Correct some memory management errors server_hostname in
  _ssl.wrap_socket().

- bpo-26750: unittest.mock.create_autospec() now works properly for
  subclasses of property() and other data descriptors.  Removes the never
  publicly used, never documented unittest.mock.DescriptorTypes tuple.

- bpo-26754: Undocumented support of general bytes-like objects as path in
  compile() and similar functions is now deprecated.

- bpo-26800: Undocumented support of general bytes-like objects as paths in
  os functions is now deprecated.

- bpo-26981: Add _order_ compatibility shim to enum.Enum for Python 2/3 code
  bases.

- bpo-27661: Added tzinfo keyword argument to datetime.combine.

- In the curses module, raise an error if window.getstr() or window.instr()
  is passed a negative value.

- bpo-27783: Fix possible usage of uninitialized memory in
  operator.methodcaller.

- bpo-27774: Fix possible Py_DECREF on unowned object in _sre.

- bpo-27760: Fix possible integer overflow in binascii.b2a_qp.

- bpo-27758: Fix possible integer overflow in the _csv module for large
  record lengths.

- bpo-27568: Prevent HTTPoxy attack (CVE-2016-1000110). Ignore the
  HTTP_PROXY variable when REQUEST_METHOD environment is set, which
  indicates that the script is in CGI mode.

- bpo-7063: Remove dead code from the "array" module's slice handling. Patch
  by Chuck.

- bpo-27656: Do not assume sched.h defines any SCHED_* constants.

- bpo-27130: In the "zlib" module, fix handling of large buffers (typically
  4 GiB) when compressing and decompressing.  Previously, inputs were
  limited to 4 GiB, and compression and decompression operations did not
  properly handle results of 4 GiB.

- bpo-24773: Implemented :pep:`495` (Local Time Disambiguation).

- Expose the EPOLLEXCLUSIVE constant (when it is defined) in the select
  module.

- bpo-27567: Expose the EPOLLRDHUP and POLLRDHUP constants in the select
  module.

- bpo-1621: Avoid signed int negation overflow in the "audioop" module.

- bpo-27533: Release GIL in nt._isdir

- bpo-17711: Fixed unpickling by the persistent ID with protocol 0. Original
  patch by Alexandre Vassalotti.

- bpo-27522: Avoid an unintentional reference cycle in email.feedparser.

- bpo-27512: Fix a segfault when os.fspath() called an __fspath__() method
  that raised an exception. Patch by Xiang Zhang.

IDLE
----

- bpo-27714: text_textview and test_autocomplete now pass when re-run in the
  same process.  This occurs when test_idle fails when run with the -w
  option but without -jn.  Fix warning from test_config.

- bpo-27621: Put query response validation error messages in the query box
  itself instead of in a separate messagebox.  Redo tests to match. Add Mac
  OSX refinements. Original patch by Mark Roseman.

- bpo-27620: Escape key now closes Query box as cancelled.

- bpo-27609: IDLE: tab after initial whitespace should tab, not
  autocomplete. This fixes problem with writing docstrings at least twice
  indented.

- bpo-27609: Explicitly return None when there are also non-None returns. In
  a few cases, reverse a condition and eliminate a return.

- bpo-25507: IDLE no longer runs buggy code because of its tkinter imports.
  Users must include the same imports required to run directly in Python.

- bpo-27173: Add 'IDLE Modern Unix' to the built-in key sets. Make the
  default key set depend on the platform. Add tests for the changes to the
  config module.

- bpo-27452: add line counter and crc to IDLE configHandler test dump.

Tests
-----

- bpo-25805: Skip a test in test_pkgutil as needed that doesn't work when
  ``__name__ == __main__``. Patch by SilentGhost.

- bpo-27472: Add test.support.unix_shell as the path to the default shell.

- bpo-27369: In test_pyexpat, avoid testing an error message detail that
  changed in Expat 2.2.0.

- bpo-27594: Prevent assertion error when running test_ast with coverage
  enabled: ensure code object has a valid first line number. Patch suggested
  by Ivan Levkivskyi.

Windows
-------

- bpo-27647: Update bundled Tcl/Tk to 8.6.6.

- bpo-27610: Adds :pep:`514` metadata to Windows installer

- bpo-27469: Adds a shell extension to the launcher so that drag and drop
  works correctly.

- bpo-27309: Enables proper Windows styles in python[w].exe manifest.

Build
-----

- bpo-27713: Suppress spurious build warnings when updating importlib's
  bootstrap files. Patch by Xiang Zhang

- bpo-25825: Correct the references to Modules/python.exp, which is required
  on AIX.  The references were accidentally changed in 3.5.0a1.

- bpo-27453: CPP invocation in configure must use CPPFLAGS. Patch by Chi
  Hsuan Yen.

- bpo-27641: The configure script now inserts comments into the makefile to
  prevent the pgen and _freeze_importlib executables from being
  cross-compiled.

- bpo-26662: Set PYTHON_FOR_GEN in configure as the Python program to be
  used for file generation during the build.

- bpo-10910: Avoid C++ compilation errors on FreeBSD and OS X. Also update
  FreedBSD version checks for the original ctype UTF-8 workaround.


What's New in Python 3.6.0 alpha 3?
===================================

*Release date: 2016-07-11*

Security
--------

- bpo-27278: Fix os.urandom() implementation using getrandom() on Linux.
  Truncate size to INT_MAX and loop until we collected enough random bytes,
  instead of casting a directly Py_ssize_t to int.

- bpo-22636: Avoid shell injection problems with ctypes.util.find_library().

Core and Builtins
-----------------

- bpo-27473: Fixed possible integer overflow in bytes and bytearray
  concatenations. Patch by Xiang Zhang.

- bpo-23034: The output of a special Python build with defined COUNT_ALLOCS,
  SHOW_ALLOC_COUNT or SHOW_TRACK_COUNT macros is now off by  default.  It
  can be re-enabled using the "-X showalloccount" option.  It now outputs to
  stderr instead of stdout.

- bpo-27443: __length_hint__() of bytearray iterators no longer return a
  negative integer for a resized bytearray.

- bpo-27007: The fromhex() class methods of bytes and bytearray subclasses
  now return an instance of corresponding subclass.

Library
-------

- bpo-26844: Fix error message for imp.find_module() to refer to 'path'
  instead of 'name'. Patch by Lev Maximov.

- bpo-23804: Fix SSL zero-length recv() calls to not block and not raise an
  error about unclean EOF.

- bpo-27466: Change time format returned by http.cookie.time2netscape,
  confirming the netscape cookie format and making it consistent with
  documentation.

- bpo-21708: Deprecated dbm.dumb behavior that differs from common dbm
  behavior: creating a database in 'r' and 'w' modes and modifying a
  database in 'r' mode.

- bpo-26721: Change the socketserver.StreamRequestHandler.wfile attribute to
  implement BufferedIOBase. In particular, the write() method no longer does
  partial writes.

- bpo-22115: Added methods trace_add, trace_remove and trace_info in the
  tkinter.Variable class.  They replace old methods trace_variable, trace,
  trace_vdelete and trace_vinfo that use obsolete Tcl commands and might not
  work in future versions of Tcl.  Fixed old tracing methods:
  trace_vdelete() with wrong mode no longer break tracing, trace_vinfo() now
  always returns a list of pairs of strings, tracing in the "u" mode now
  works.

- bpo-26243: Only the level argument to zlib.compress() is keyword argument
  now.  The first argument is positional-only.

- bpo-27038: Expose the DirEntry type as os.DirEntry. Code patch by Jelle
  Zijlstra.

- bpo-27186: Update os.fspath()/PyOS_FSPath() to check the return value of
  __fspath__() to be either str or bytes.

- bpo-18726: All optional parameters of the dump(), dumps(), load() and
  loads() functions and JSONEncoder and JSONDecoder class constructors in
  the json module are now keyword-only.

- bpo-27319: Methods selection_set(), selection_add(), selection_remove()
  and selection_toggle() of ttk.TreeView now allow passing multiple items as
  multiple arguments instead of passing them as a tuple.  Deprecated
  undocumented ability of calling the selection() method with arguments.

- bpo-27079: Fixed curses.ascii functions isblank(), iscntrl() and
  ispunct().

- bpo-27294: Numerical state in the repr for Tkinter event objects is now
  represented as a combination of known flags.

- bpo-27177: Match objects in the re module now support index-like objects
  as group indices.  Based on patches by Jeroen Demeyer and Xiang Zhang.

- bpo-26754: Some functions (compile() etc) accepted a filename argument
  encoded as an iterable of integers. Now only strings and byte-like objects
  are accepted.

- bpo-26536: socket.ioctl now supports SIO_LOOPBACK_FAST_PATH. Patch by
  Daniel Stokes.

- bpo-27048: Prevents distutils failing on Windows when environment
  variables contain non-ASCII characters

- bpo-27330: Fixed possible leaks in the ctypes module.

- bpo-27238: Got rid of bare excepts in the turtle module.  Original patch
  by Jelle Zijlstra.

- bpo-27122: When an exception is raised within the context being managed by
  a contextlib.ExitStack() and one of the exit stack generators catches and
  raises it in a chain, do not re-raise the original exception when exiting,
  let the new chained one through.  This avoids the :pep:`479` bug described
  in issue25782.

- bpo-16864: sqlite3.Cursor.lastrowid now supports REPLACE statement.
  Initial patch by Alex LordThorsen.

- bpo-26386: Fixed ttk.TreeView selection operations with item id's
  containing spaces.

- bpo-8637: Honor a pager set by the env var MANPAGER (in preference to one
  set by the env var PAGER).

- bpo-16182: Fix various functions in the "readline" module to use the
  locale encoding, and fix get_begidx() and get_endidx() to return code
  point indexes.

- bpo-27392: Add loop.connect_accepted_socket(). Patch by Jim Fulton.

IDLE
----

- bpo-27477: IDLE search dialogs now use ttk widgets.

- bpo-27173: Add 'IDLE Modern Unix' to the built-in key sets. Make the
  default key set depend on the platform. Add tests for the changes to the
  config module.

- bpo-27452: make command line "idle-test> python test_help.py" work.
  __file__ is relative when python is started in the file's directory.

- bpo-27452: add line counter and crc to IDLE configHandler test dump.

- bpo-27380: IDLE: add query.py with base Query dialog and ttk widgets.
  Module had subclasses SectionName, ModuleName, and HelpSource, which are
  used to get information from users by configdialog and file =>Load Module.
  Each subclass has itw own validity checks.  Using ModuleName allows users
  to edit bad module names instead of starting over. Add tests and delete
  the two files combined into the new one.

- bpo-27372: Test_idle no longer changes the locale.

- bpo-27365: Allow non-ascii chars in IDLE NEWS.txt, for contributor names.

- bpo-27245: IDLE: Cleanly delete custom themes and key bindings.
  Previously, when IDLE was started from a console or by import, a cascade
  of warnings was emitted. Patch by Serhiy Storchaka.

- bpo-24137: Run IDLE, test_idle, and htest with tkinter default root
  disabled.  Fix code and tests that fail with this restriction.  Fix htests
  to not create a second and redundant root and mainloop.

- bpo-27310: Fix IDLE.app failure to launch on OS X due to vestigial import.

C API
-----

- bpo-26754: PyUnicode_FSDecoder() accepted a filename argument encoded as
  an iterable of integers. Now only strings and byte-like objects are
  accepted.

Build
-----

- bpo-28066: Fix the logic that searches build directories for generated
  include files when building outside the source tree.

- bpo-27442: Expose the Android API level that python was built against, in
  sysconfig.get_config_vars() as 'ANDROID_API_LEVEL'.

- bpo-27434: The interpreter that runs the cross-build, found in PATH, must
  now be of the same feature version (e.g. 3.6) as the source being built.

- bpo-26930: Update Windows builds to use OpenSSL 1.0.2h.

- bpo-23968: Rename the platform directory from plat-$(MACHDEP) to
  plat-$(PLATFORM_TRIPLET). Rename the config directory (LIBPL) from
  config-$(LDVERSION) to config-$(LDVERSION)-$(PLATFORM_TRIPLET). Install
  the platform specific _sysconfigdata module into the platform directory
  and rename it to include the ABIFLAGS.

- Don't use largefile support for GNU/Hurd.

Tools/Demos
-----------

- bpo-27332: Fixed the type of the first argument of module-level functions
  generated by Argument Clinic.  Patch by Petr Viktorin.

- bpo-27418: Fixed Tools/importbench/importbench.py.

Documentation
-------------

- bpo-19489: Moved the search box from the sidebar to the header and footer
  of each page. Patch by Ammar Askar.

- bpo-27285: Update documentation to reflect the deprecation of ``pyvenv``
  and normalize on the term "virtual environment". Patch by Steve Piercy.

Tests
-----

- bpo-27027: Added test.support.is_android that is True when this is an
  Android build.


What's New in Python 3.6.0 alpha 2?
===================================

*Release date: 2016-06-13*

Security
--------

- bpo-26556: Update expat to 2.1.1, fixes CVE-2015-1283.

- Fix TLS stripping vulnerability in smtplib, CVE-2016-0772. Reported by
  Team Oststrom.

- bpo-26839: On Linux, :func:`os.urandom` now calls ``getrandom()`` with
  ``GRND_NONBLOCK`` to fall back on reading ``/dev/urandom`` if the urandom
  entropy pool is not initialized yet. Patch written by Colm Buckley.

Core and Builtins
-----------------

- bpo-27095: Simplified MAKE_FUNCTION and removed MAKE_CLOSURE opcodes.
  Patch by Demur Rumed.

- bpo-27190: Raise NotSupportedError if sqlite3 is older than 3.3.1. Patch
  by Dave Sawyer.

- bpo-27286: Fixed compiling BUILD_MAP_UNPACK_WITH_CALL opcode.  Calling
  function with generalized unpacking (PEP 448) and conflicting keyword
  names could cause undefined behavior.

- bpo-27140: Added BUILD_CONST_KEY_MAP opcode.

- bpo-27186: Add support for os.PathLike objects to open() (part of
  :pep:`519`).

- bpo-27066: Fixed SystemError if a custom opener (for open()) returns a
  negative number without setting an exception.

- bpo-26983: float() now always return an instance of exact float. The
  deprecation warning is emitted if __float__ returns an instance of a
  strict subclass of float.  In a future versions of Python this can be an
  error.

- bpo-27097: Python interpreter is now about 7% faster due to optimized
  instruction decoding.  Based on patch by Demur Rumed.

- bpo-26647: Python interpreter now uses 16-bit wordcode instead of
  bytecode. Patch by Demur Rumed.

- bpo-23275: Allow assigning to an empty target list in round brackets: () =
  iterable.

- bpo-27243: Update the __aiter__ protocol: instead of returning an
  awaitable that resolves to an asynchronous iterator, the asynchronous
  iterator should be returned directly.  Doing the former will trigger a
  PendingDeprecationWarning.

Library
-------

- Comment out socket (SO_REUSEPORT) and posix (O_SHLOCK, O_EXLOCK) constants
  exposed on the API which are not implemented on GNU/Hurd. They would not
  work at runtime anyway.

- bpo-27025: Generated names for Tkinter widgets are now more meaningful and
  recognizable.

- bpo-25455: Fixed crashes in repr of recursive ElementTree.Element and
  functools.partial objects.

- bpo-27294: Improved repr for Tkinter event objects.

- bpo-20508: Improve exception message of IPv{4,6}Network.__getitem__. Patch
  by Gareth Rees.

- bpo-21386: Implement missing IPv4Address.is_global property.  It was
  documented since 07a5610bae9d.  Initial patch by Roger Luethi.

- bpo-27029: Removed deprecated support of universal newlines mode from
  ZipFile.open().

- bpo-27030: Unknown escapes consisting of ``'\'`` and an ASCII letter in
  regular expressions now are errors.  The re.LOCALE flag now can be used
  only with bytes patterns.

- bpo-27186: Add os.PathLike support to DirEntry (part of :pep:`519`).
  Initial patch by Jelle Zijlstra.

- bpo-20900: distutils register command now decodes HTTP responses
  correctly.  Initial patch by ingrid.

- bpo-27186: Add os.PathLike support to pathlib, removing its provisional
  status (part of PEP 519). Initial patch by Dusty Phillips.

- bpo-27186: Add support for os.PathLike objects to os.fsencode() and
  os.fsdecode() (part of :pep:`519`).

- bpo-27186: Introduce os.PathLike and os.fspath() (part of :pep:`519`).

- A new version of typing.py provides several new classes and features:
  @overload outside stubs, Reversible, DefaultDict, Text, ContextManager,
  Type[], NewType(), TYPE_CHECKING, and numerous bug fixes (note that some
  of the new features are not yet implemented in mypy or other static
  analyzers). Also classes for :pep:`492` (Awaitable, AsyncIterable,
  AsyncIterator) have been added (in fact they made it into 3.5.1 but were
  never mentioned).

- bpo-25738: Stop http.server.BaseHTTPRequestHandler.send_error() from
  sending a message body for 205 Reset Content.  Also, don't send Content
  header fields in responses that don't have a body.  Patch by Susumu
  Koshiba.

- bpo-21313: Fix the "platform" module to tolerate when sys.version contains
  truncated build information.

- bpo-23883: Added missing APIs to __all__ to match the documented APIs for
  the following modules: cgi, mailbox, mimetypes, plistlib and smtpd.
  Patches by Jacek Kołodziej.

- bpo-27164: In the zlib module, allow decompressing raw Deflate streams
  with a predefined zdict.  Based on patch by Xiang Zhang.

- bpo-24291: Fix wsgiref.simple_server.WSGIRequestHandler to completely
  write data to the client.  Previously it could do partial writes and
  truncate data.  Also, wsgiref.handler.ServerHandler can now handle stdout
  doing partial writes, but this is deprecated.

- bpo-21272: Use _sysconfigdata.py to initialize distutils.sysconfig.

- bpo-19611: :mod:`inspect` now reports the implicit ``.0`` parameters
  generated by the compiler for comprehension and generator expression
  scopes as if they were positional-only parameters called ``implicit0``.
  Patch by Jelle Zijlstra.

- bpo-26809: Add ``__all__`` to :mod:`string`.  Patch by Emanuel Barry.

- bpo-26373: subprocess.Popen.communicate now correctly ignores
  BrokenPipeError when the child process dies before .communicate() is
  called in more/all circumstances.

- signal, socket, and ssl module IntEnum constant name lookups now return a
  consistent name for values having multiple names.  Ex: signal.Signals(6)
  now refers to itself as signal.SIGALRM rather than flipping between that
  and signal.SIGIOT based on the interpreter's hash randomization seed.

- bpo-27167: Clarify the subprocess.CalledProcessError error message text
  when the child process died due to a signal.

- bpo-25931: Don't define socketserver.Forking* names on platforms such as
  Windows that do not support os.fork().

- bpo-21776: distutils.upload now correctly handles HTTPError. Initial patch
  by Claudiu Popa.

- bpo-26526: Replace custom parse tree validation in the parser module with
  a simple DFA validator.

- bpo-27114: Fix SSLContext._load_windows_store_certs fails with
  PermissionError

- bpo-18383: Avoid creating duplicate filters when using filterwarnings and
  simplefilter. Based on patch by Alex Shkop.

- bpo-23026: winreg.QueryValueEx() now return an integer for REG_QWORD type.

- bpo-26741: subprocess.Popen destructor now emits a ResourceWarning warning
  if the child process is still running.

- bpo-27056: Optimize pickle.load() and pickle.loads(), up to 10% faster to
  deserialize a lot of small objects.

- bpo-21271: New keyword only parameters in reset_mock call.

IDLE
----

- bpo-5124: Paste with text selected now replaces the selection on X11. This
  matches how paste works on Windows, Mac, most modern Linux apps, and ttk
  widgets. Original patch by Serhiy Storchaka.

- bpo-24750: Switch all scrollbars in IDLE to ttk versions. Where needed,
  minimal tests are added to cover changes.

- bpo-24759: IDLE requires tk 8.5 and availability ttk widgets. Delete now
  unneeded tk version tests and code for older versions. Add test for IDLE
  syntax colorizer.

- bpo-27239: idlelib.macosx.isXyzTk functions initialize as needed.

- bpo-27262: move Aqua unbinding code, which enable context menus, to
  macosx.

- bpo-24759: Make clear in idlelib.idle_test.__init__ that the directory is
  a private implementation of test.test_idle and tool for maintainers.

- bpo-27196: Stop 'ThemeChanged' warnings when running IDLE tests. These
  persisted after other warnings were suppressed in #20567. Apply Serhiy
  Storchaka's update_idletasks solution to four test files. Record this
  additional advice in idle_test/README.txt

- bpo-20567: Revise idle_test/README.txt with advice about avoiding tk
  warning messages from tests.  Apply advice to several IDLE tests.

- bpo-24225: Update idlelib/README.txt with new file names and event
  handlers.

- bpo-27156: Remove obsolete code not used by IDLE.

- bpo-27117: Make colorizer htest and turtledemo work with dark themes. Move
  code for configuring text widget colors to a new function.

- bpo-24225: Rename many `idlelib/*.py` and `idle_test/test_*.py` files.
  Edit files to replace old names with new names when the old name referred
  to the module rather than the class it contained. See the issue and IDLE
  section in What's New in 3.6 for more.

- bpo-26673: When tk reports font size as 0, change to size 10. Such fonts
  on Linux prevented the configuration dialog from opening.

- bpo-21939: Add test for IDLE's percolator. Original patch by Saimadhav
  Heblikar.

- bpo-21676: Add test for IDLE's replace dialog. Original patch by Saimadhav
  Heblikar.

- bpo-18410: Add test for IDLE's search dialog. Original patch by Westley
  Martínez.

- bpo-21703: Add test for undo delegator.  Patch mostly by Saimadhav
  Heblikar .

- bpo-27044: Add ConfigDialog.remove_var_callbacks to stop memory leaks.

- bpo-23977: Add more asserts to test_delegator.

Documentation
-------------

- bpo-16484: Change the default PYTHONDOCS URL to "https:", and fix the
  resulting links to use lowercase.  Patch by Sean Rodman, test by Kaushik
  Nadikuditi.

- bpo-24136: Document the new :pep:`448` unpacking syntax of 3.5.

- bpo-22558: Add remaining doc links to source code for Python-coded
  modules. Patch by Yoni Lavi.

Tests
-----

- bpo-25285: regrtest now uses subprocesses when the -j1 command line option
  is used: each test file runs in a fresh child process. Before, the -j1
  option was ignored.

- bpo-25285: Tools/buildbot/test.bat script now uses -j1 by default to run
  each test file in fresh child process.

Windows
-------

- bpo-27064: The py.exe launcher now defaults to Python 3. The Windows
  launcher ``py.exe`` no longer prefers an installed Python 2 version over
  Python 3 by default when used interactively.

- bpo-17500: Remove unused and outdated icons. (See also:
  https://github.com/python/pythondotorg/issues/945)

Build
-----

- bpo-27229: Fix the cross-compiling pgen rule for in-tree builds.  Patch by
  Xavier de Gaye.

- bpo-26930: Update OS X 10.5+ 32-bit-only installer to build and link with
  OpenSSL 1.0.2h.

C API
-----

- bpo-27186: Add the PyOS_FSPath() function (part of :pep:`519`).

- bpo-26282: PyArg_ParseTupleAndKeywords() now supports positional-only
  parameters.

Tools/Demos
-----------

- bpo-26282: Argument Clinic now supports positional-only and keyword
  parameters in the same function.


What's New in Python 3.6.0 alpha 1?
===================================

*Release date: 2016-05-16*

Security
--------

- bpo-26657: Fix directory traversal vulnerability with http.server on
  Windows.  This fixes a regression that was introduced in 3.3.4rc1 and
  3.4.0rc1.  Based on patch by Philipp Hagemeister.

- bpo-26313: ssl.py _load_windows_store_certs fails if windows cert store is
  empty. Patch by Baji.

- bpo-25939: On Windows open the cert store readonly in
  ssl.enum_certificates.

Core and Builtins
-----------------

- bpo-20041: Fixed TypeError when frame.f_trace is set to None. Patch by
  Xavier de Gaye.

- bpo-26168: Fixed possible refleaks in failing Py_BuildValue() with the "N"
  format unit.

- bpo-26991: Fix possible refleak when creating a function with annotations.

- bpo-27039: Fixed bytearray.remove() for values greater than 127.  Based on
  patch by Joe Jevnik.

- bpo-23640: int.from_bytes() no longer bypasses constructors for
  subclasses.

- bpo-27005: Optimized the float.fromhex() class method for exact float. It
  is now 2 times faster.

- bpo-18531: Single var-keyword argument of dict subtype was passed
  unscathed to the C-defined function.  Now it is converted to exact dict.

- bpo-26811: gc.get_objects() no longer contains a broken tuple with NULL
  pointer.

- bpo-20120: Use RawConfigParser for .pypirc parsing, removing support for
  interpolation unintentionally added with move to Python 3. Behavior no
  longer does any interpolation in .pypirc files, matching behavior in
  Python 2.7 and Setuptools 19.0.

- bpo-26249: Memory functions of the :c:func:`PyMem_Malloc` domain
  (:c:data:`PYMEM_DOMAIN_MEM`) now use the :ref:`pymalloc allocator
  <pymalloc>` rather than system :c:func:`malloc`. Applications calling
  :c:func:`PyMem_Malloc` without holding the GIL can now crash: use
  ``PYTHONMALLOC=debug`` environment variable to validate the usage of
  memory allocators in your application.

- bpo-26802: Optimize function calls only using unpacking like
  ``func(*tuple)`` (no other positional argument, no keyword): avoid copying
  the tuple. Patch written by Joe Jevnik.

- bpo-26659: Make the builtin slice type support cycle collection.

- bpo-26718: super.__init__ no longer leaks memory if called multiple times.
  NOTE: A direct call of super.__init__ is not endorsed!

- bpo-27138: Fix the doc comment for FileFinder.find_spec().

- bpo-27147: Mention :pep:`420` in the importlib docs.

- bpo-25339: PYTHONIOENCODING now has priority over locale in setting the
  error handler for stdin and stdout.

- bpo-26494: Fixed crash on iterating exhausting iterators. Affected classes
  are generic sequence iterators, iterators of str, bytes, bytearray, list,
  tuple, set, frozenset, dict, OrderedDict, corresponding views and
  os.scandir() iterator.

- bpo-26574: Optimize ``bytes.replace(b'', b'.')`` and
  ``bytearray.replace(b'', b'.')``. Patch written by Josh Snider.

- bpo-26581: If coding cookie is specified multiple times on a line in
  Python source code file, only the first one is taken to account.

- bpo-19711: Add tests for reloading namespace packages.

- bpo-21099: Switch applicable importlib tests to use :pep:`451` API.

- bpo-26563: Debug hooks on Python memory allocators now raise a fatal error
  if functions of the :c:func:`PyMem_Malloc` family are called without
  holding the GIL.

- bpo-26564: On error, the debug hooks on Python memory allocators now use
  the :mod:`tracemalloc` module to get the traceback where a memory block
  was allocated.

- bpo-26558: The debug hooks on Python memory allocator
  :c:func:`PyObject_Malloc` now detect when functions are called without
  holding the GIL.

- bpo-26516: Add :envvar:`PYTHONMALLOC` environment variable to set the
  Python memory allocators and/or install debug hooks.

- bpo-26516: The :c:func:`PyMem_SetupDebugHooks` function can now also be
  used on Python compiled in release mode.

- bpo-26516: The :envvar:`PYTHONMALLOCSTATS` environment variable can now
  also be used on Python compiled in release mode. It now has no effect if
  set to an empty string.

- bpo-26516: In debug mode, debug hooks are now also installed on Python
  memory allocators when Python is configured without pymalloc.

- bpo-26464: Fix str.translate() when string is ASCII and first replacements
  removes character, but next replacement uses a non-ASCII character or a
  string longer than 1 character. Regression introduced in Python 3.5.0.

- bpo-22836: Ensure exception reports from PyErr_Display() and
  PyErr_WriteUnraisable() are sensible even when formatting them produces
  secondary errors.  This affects the reports produced by
  sys.__excepthook__() and when __del__() raises an exception.

- bpo-26302: Correct behavior to reject comma as a legal character for
  cookie names.

- bpo-26136: Upgrade the warning when a generator raises StopIteration from
  PendingDeprecationWarning to DeprecationWarning.  Patch by Anish Shah.

- bpo-26204: The compiler now ignores all constant statements: bytes, str,
  int, float, complex, name constants (None, False, True), Ellipsis and
  ast.Constant; not only str and int. For example, ``1.0`` is now ignored in
  ``def f(): 1.0``.

- bpo-4806: Avoid masking the original TypeError exception when using star
  (``*``) unpacking in function calls.  Based on patch by Hagen Fürstenau
  and Daniel Urban.

- bpo-26146: Add a new kind of AST node: ``ast.Constant``. It can be used by
  external AST optimizers, but the compiler does not emit directly such
  node.

- bpo-23601: Sped-up allocation of dict key objects by using Python's small
  object allocator.  (Contributed by Julian Taylor.)

- bpo-18018: Import raises ImportError instead of SystemError if a relative
  import is attempted without a known parent package.

- bpo-25843: When compiling code, don't merge constants if they are equal
  but have a different types. For example, ``f1, f2 = lambda: 1, lambda:
  1.0`` is now correctly compiled to two different functions: ``f1()``
  returns ``1`` (``int``) and ``f2()`` returns ``1.0`` (``float``), even if
  ``1`` and ``1.0`` are equal.

- bpo-26107: The format of the ``co_lnotab`` attribute of code objects
  changes to support negative line number delta.

- bpo-26154: Add a new private _PyThreadState_UncheckedGet() function to get
  the current Python thread state, but don't issue a fatal error if it is
  NULL. This new function must be used instead of accessing directly the
  _PyThreadState_Current variable.  The variable is no more exposed since
  Python 3.5.1 to hide the exact implementation of atomic C types, to avoid
  compiler issues.

- bpo-25791: If __package__ != __spec__.parent or if neither __package__ or
  __spec__ are defined then ImportWarning is raised.

- bpo-22995: [UPDATE] Comment out the one of the pickleability tests in
  _PyObject_GetState() due to regressions observed in Cython-based projects.

- bpo-25961: Disallowed null characters in the type name.

- bpo-25973: Fix segfault when an invalid nonlocal statement binds a name
  starting with two underscores.

- bpo-22995: Instances of extension types with a state that aren't
  subclasses of list or dict and haven't implemented any pickle-related
  methods (__reduce__, __reduce_ex__, __getnewargs__, __getnewargs_ex__, or
  __getstate__), can no longer be pickled.  Including memoryview.

- bpo-20440: Massive replacing unsafe attribute setting code with special
  macro Py_SETREF.

- bpo-25766: Special method __bytes__() now works in str subclasses.

- bpo-25421: __sizeof__ methods of builtin types now use dynamic basic size.
  This allows sys.getsize() to work correctly with their subclasses with
  __slots__ defined.

- bpo-25709: Fixed problem with in-place string concatenation and utf-8
  cache.

- bpo-5319: New Py_FinalizeEx() API allowing Python to set an exit status of
  120 on failure to flush buffered streams.

- bpo-25485: telnetlib.Telnet is now a context manager.

- bpo-24097: Fixed crash in object.__reduce__() if slot name is freed inside
  __getattr__.

- bpo-24731: Fixed crash on converting objects with special methods
  __bytes__, __trunc__, and __float__ returning instances of subclasses of
  bytes, int, and float to subclasses of bytes, int, and float
  correspondingly.

- bpo-25630: Fix a possible segfault during argument parsing in functions
  that accept filesystem paths.

- bpo-23564: Fixed a partially broken sanity check in the _posixsubprocess
  internals regarding how fds_to_pass were passed to the child.  The bug had
  no actual impact as subprocess.py already avoided it.

- bpo-25388: Fixed tokenizer crash when processing undecodable source code
  with a null byte.

- bpo-25462: The hash of the key now is calculated only once in most
  operations in C implementation of OrderedDict.

- bpo-22995: Default implementation of __reduce__ and __reduce_ex__ now
  rejects builtin types with not defined __new__.

- bpo-24802: Avoid buffer overreads when int(), float(), compile(), exec()
  and eval() are passed bytes-like objects.  These objects are not
  necessarily terminated by a null byte, but the functions assumed they
  were.

- bpo-25555: Fix parser and AST: fill lineno and col_offset of "arg" node
  when compiling AST from Python objects.

- bpo-24726: Fixed a crash and leaking NULL in repr() of OrderedDict that
  was mutated by direct calls of dict methods.

- bpo-25449: Iterating OrderedDict with keys with unstable hash now raises
  KeyError in C implementations as well as in Python implementation.

- bpo-25395: Fixed crash when highly nested OrderedDict structures were
  garbage collected.

- bpo-25401: Optimize bytes.fromhex() and bytearray.fromhex(): they are now
  between 2x and 3.5x faster.

- bpo-25399: Optimize bytearray % args using the new private _PyBytesWriter
  API. Formatting is now between 2.5 and 5 times faster.

- bpo-25274: sys.setrecursionlimit() now raises a RecursionError if the new
  recursion limit is too low depending at the current recursion depth.
  Modify also the "lower-water mark" formula to make it monotonic. This mark
  is used to decide when the overflowed flag of the thread state is reset.

- bpo-24402: Fix input() to prompt to the redirected stdout when
  sys.stdout.fileno() fails.

- bpo-25349: Optimize bytes % args using the new private _PyBytesWriter API.
  Formatting is now up to 2 times faster.

- bpo-24806: Prevent builtin types that are not allowed to be subclassed
  from being subclassed through multiple inheritance.

- bpo-25301: The UTF-8 decoder is now up to 15 times as fast for error
  handlers: ``ignore``, ``replace`` and ``surrogateescape``.

- bpo-24848: Fixed a number of bugs in UTF-7 decoding of misformed data.

- bpo-25267: The UTF-8 encoder is now up to 75 times as fast for error
  handlers: ``ignore``, ``replace``, ``surrogateescape``, ``surrogatepass``.
  Patch co-written with Serhiy Storchaka.

- bpo-25280: Import trace messages emitted in verbose (-v) mode are no
  longer formatted twice.

- bpo-25227: Optimize ASCII and latin1 encoders with the ``surrogateescape``
  error handler: the encoders are now up to 3 times as fast. Initial patch
  written by Serhiy Storchaka.

- bpo-25003: On Solaris 11.3 or newer, os.urandom() now uses the getrandom()
  function instead of the getentropy() function. The getentropy() function
  is blocking to generate very good quality entropy, os.urandom() doesn't
  need such high-quality entropy.

- bpo-9232: Modify Python's grammar to allow trailing commas in the argument
  list of a function declaration.  For example, "def f(\*, a = 3,): pass" is
  now legal. Patch from Mark Dickinson.

- bpo-24965: Implement :pep:`498` "Literal String Interpolation". This
  allows you to embed expressions inside f-strings, which are converted to
  normal strings at run time. Given x=3, then f'value={x}' == 'value=3'.
  Patch by Eric V. Smith.

- bpo-26478: Fix semantic bugs when using binary operators with dictionary
  views and tuples.

- bpo-26171: Fix possible integer overflow and heap corruption in
  zipimporter.get_data().

- bpo-25660: Fix TAB key behaviour in REPL with readline.

- bpo-26288: Optimize PyLong_AsDouble.

- bpo-26289: Optimize floor and modulo division for single-digit longs.
  Microbenchmarks show 2-2.5x improvement.  Built-in 'divmod' function is
  now also ~10% faster. (See also: bpo-26315)

- bpo-25887: Raise a RuntimeError when a coroutine object is awaited more
  than once.

Library
-------

- bpo-27057: Fix os.set_inheritable() on Android, ioctl() is blocked by
  SELinux and fails with EACCESS. The function now falls back to fcntl().
  Patch written by Michał Bednarski.

- bpo-27014: Fix infinite recursion using typing.py.  Thanks to Kalle Tuure!

- bpo-27031: Removed dummy methods in Tkinter widget classes: tk_menuBar()
  and tk_bindForTraversal().

- bpo-14132: Fix urllib.request redirect handling when the target only has a
  query string.  Original fix by Ján Janech.

- bpo-17214: The "urllib.request" module now percent-encodes non-ASCII bytes
  found in redirect target URLs.  Some servers send Location header fields
  with non-ASCII bytes, but "http.client" requires the request target to be
  ASCII-encodable, otherwise a UnicodeEncodeError is raised.  Based on patch
  by Christian Heimes.

- bpo-27033: The default value of the decode_data parameter for
  smtpd.SMTPChannel and smtpd.SMTPServer constructors is changed to False.

- bpo-27034: Removed deprecated class asynchat.fifo.

- bpo-26870: Added readline.set_auto_history(), which can stop entries being
  automatically added to the history list.  Based on patch by Tyler
  Crompton.

- bpo-26039: zipfile.ZipFile.open() can now be used to write data into a ZIP
  file, as well as for extracting data.  Patch by Thomas Kluyver.

- bpo-26892: Honor debuglevel flag in urllib.request.HTTPHandler. Patch
  contributed by Chi Hsuan Yen.

- bpo-22274: In the subprocess module, allow stderr to be redirected to
  stdout even when stdout is not redirected.  Patch by Akira Li.

- bpo-26807: mock_open 'files' no longer error on readline at end of file.
  Patch from Yolanda Robla.

- bpo-25745: Fixed leaking a userptr in curses panel destructor.

- bpo-26977: Removed unnecessary, and ignored, call to sum of squares helper
  in statistics.pvariance.

- bpo-26002: Use bisect in statistics.median instead of a linear search.
  Patch by Upendra Kuma.

- bpo-25974: Make use of new Decimal.as_integer_ratio() method in statistics
  module. Patch by Stefan Krah.

- bpo-26996: Add secrets module as described in :pep:`506`.

- bpo-26881: The modulefinder module now supports extended opcode arguments.

- bpo-23815: Fixed crashes related to directly created instances of types in
  _tkinter and curses.panel modules.

- bpo-17765: weakref.ref() no longer silently ignores keyword arguments.
  Patch by Georg Brandl.

- bpo-26873: xmlrpc now raises ResponseError on unsupported type tags
  instead of silently return incorrect result.

- bpo-26915: The __contains__ methods in the collections ABCs now check for
  identity before checking equality.  This better matches the behavior of
  the concrete classes, allows sensible handling of NaNs, and makes it
  easier to reason about container invariants.

- bpo-26711: Fixed the comparison of plistlib.Data with other types.

- bpo-24114: Fix an uninitialized variable in `ctypes.util`. The bug only
  occurs on SunOS when the ctypes implementation searches for the `crle`
  program.  Patch by Xiang Zhang.  Tested on SunOS by Kees Bos.

- bpo-26864: In urllib.request, change the proxy bypass host checking
  against no_proxy to be case-insensitive, and to not match unrelated host
  names that happen to have a bypassed hostname as a suffix.  Patch by Xiang
  Zhang.

- bpo-24902: Print server URL on http.server startup.  Initial patch by
  Felix Kaiser.

- bpo-25788: fileinput.hook_encoded() now supports an "errors" argument for
  passing to open.  Original patch by Joseph Hackman.

- bpo-26634: recursive_repr() now sets __qualname__ of wrapper.  Patch by
  Xiang Zhang.

- bpo-26804: urllib.request will prefer lower_case proxy environment
  variables over UPPER_CASE or Mixed_Case ones. Patch contributed by
  Hans-Peter Jansen.

- bpo-26837: assertSequenceEqual() now correctly outputs non-stringified
  differing items (like bytes in the -b mode).  This affects
  assertListEqual() and assertTupleEqual().

- bpo-26041: Remove "will be removed in Python 3.7" from deprecation
  messages of platform.dist() and platform.linux_distribution(). Patch by
  Kumaripaba Miyurusara Athukorala.

- bpo-26822: itemgetter, attrgetter and methodcaller objects no longer
  silently ignore keyword arguments.

- bpo-26733: Disassembling a class now disassembles class and static
  methods. Patch by Xiang Zhang.

- bpo-26801: Fix error handling in :func:`shutil.get_terminal_size`, catch
  :exc:`AttributeError` instead of :exc:`NameError`. Patch written by
  Emanuel Barry.

- bpo-24838: tarfile's ustar and gnu formats now correctly calculate name
  and link field limits for multibyte character encodings like utf-8.

- bpo-26717: Stop encoding Latin-1-ized WSGI paths with UTF-8.  Patch by
  Anthony Sottile.

- bpo-26782: Add STARTUPINFO to subprocess.__all__ on Windows.

- bpo-26404: Add context manager to socketserver.  Patch by Aviv Palivoda.

- bpo-26735: Fix :func:`os.urandom` on Solaris 11.3 and newer when reading
  more than 1,024 bytes: call ``getrandom()`` multiple times with a limit of
  1024 bytes per call.

- bpo-26585: Eliminate http.server._quote_html() and use
  html.escape(quote=False).  Patch by Xiang Zhang.

- bpo-26685: Raise OSError if closing a socket fails.

- bpo-16329: Add .webm to mimetypes.types_map.  Patch by Giampaolo Rodola'.

- bpo-13952: Add .csv to mimetypes.types_map.  Patch by Geoff Wilson.

- bpo-26587: the site module now allows .pth files to specify files to be
  added to sys.path (e.g. zip files).

- bpo-25609: Introduce contextlib.AbstractContextManager and
  typing.ContextManager.

- bpo-26709: Fixed Y2038 problem in loading binary PLists.

- bpo-23735: Handle terminal resizing with Readline 6.3+ by installing our
  own SIGWINCH handler.  Patch by Eric Price.

- bpo-25951: Change SSLSocket.sendall() to return None, as explicitly
  documented for plain socket objects.  Patch by Aviv Palivoda.

- bpo-26586: In http.server, respond with "413 Request header fields too
  large" if there are too many header fields to parse, rather than killing
  the connection and raising an unhandled exception.  Patch by Xiang Zhang.

- bpo-26676: Added missing XMLPullParser to ElementTree.__all__.

- bpo-22854: Change BufferedReader.writable() and BufferedWriter.readable()
  to always return False.

- bpo-26492: Exhausted iterator of array.array now conforms with the
  behavior of iterators of other mutable sequences: it lefts exhausted even
  if iterated array is extended.

- bpo-26641: doctest.DocFileTest and doctest.testfile() now support packages
  (module splitted into multiple directories) for the package parameter.

- bpo-25195: Fix a regression in mock.MagicMock. _Call is a subclass of
  tuple (changeset 3603bae63c13 only works for classes) so we need to
  implement __ne__ ourselves.  Patch by Andrew Plummer.

- bpo-26644: Raise ValueError rather than SystemError when a negative length
  is passed to SSLSocket.recv() or read().

- bpo-23804: Fix SSL recv(0) and read(0) methods to return zero bytes
  instead of up to 1024.

- bpo-26616: Fixed a bug in datetime.astimezone() method.

- bpo-26637: The :mod:`importlib` module now emits an :exc:`ImportError`
  rather than a :exc:`TypeError` if :func:`__import__` is tried during the
  Python shutdown process but :data:`sys.path` is already cleared (set to
  ``None``).

- bpo-21925: :func:`warnings.formatwarning` now catches exceptions when
  calling :func:`linecache.getline` and
  :func:`tracemalloc.get_object_traceback` to be able to log
  :exc:`ResourceWarning` emitted late during the Python shutdown process.

- bpo-23848: On Windows, faulthandler.enable() now also installs an
  exception handler to dump the traceback of all Python threads on any
  Windows exception, not only on UNIX signals (SIGSEGV, SIGFPE, SIGABRT).

- bpo-26530: Add C functions :c:func:`_PyTraceMalloc_Track` and
  :c:func:`_PyTraceMalloc_Untrack` to track memory blocks using the
  :mod:`tracemalloc` module. Add :c:func:`_PyTraceMalloc_GetTraceback` to
  get the traceback of an object.

- bpo-26588: The _tracemalloc now supports tracing memory allocations of
  multiple address spaces (domains).

- bpo-24266: Ctrl+C during Readline history search now cancels the search
  mode when compiled with Readline 7.

- bpo-26590: Implement a safe finalizer for the _socket.socket type. It now
  releases the GIL to close the socket.

- bpo-18787: spwd.getspnam() now raises a PermissionError if the user
  doesn't have privileges.

- bpo-26560: Avoid potential ValueError in BaseHandler.start_response.
  Initial patch by Peter Inglesby.

- bpo-26567: Add a new function :c:func:`PyErr_ResourceWarning` function to
  pass the destroyed object. Add a *source* attribute to
  :class:`warnings.WarningMessage`. Add warnings._showwarnmsg() which uses
  tracemalloc to get the traceback where source object was allocated.

- bpo-26569: Fix :func:`pyclbr.readmodule` and :func:`pyclbr.readmodule_ex`
  to support importing packages.

- bpo-26499: Account for remaining Content-Length in HTTPResponse.readline()
  and read1(). Based on patch by Silent Ghost. Also document that
  HTTPResponse now supports these methods.

- bpo-25320: Handle sockets in directories unittest discovery is scanning.
  Patch from Victor van den Elzen.

- bpo-16181: cookiejar.http2time() now returns None if year is higher than
  datetime.MAXYEAR.

- bpo-26513: Fixes platform module detection of Windows Server

- bpo-23718: Fixed parsing time in week 0 before Jan 1.  Original patch by
  Tamás Bence Gedai.

- bpo-26323: Add Mock.assert_called() and Mock.assert_called_once() methods
  to unittest.mock. Patch written by Amit Saha.

- bpo-20589: Invoking Path.owner() and Path.group() on Windows now raise
  NotImplementedError instead of ImportError.

- bpo-26177: Fixed the keys() method for Canvas and Scrollbar widgets.

- bpo-15068: Got rid of excessive buffering in fileinput. The bufsize
  parameter is now deprecated and ignored.

- bpo-19475: Added an optional argument timespec to the datetime isoformat()
  method to choose the precision of the time component.

- bpo-2202: Fix UnboundLocalError in
  AbstractDigestAuthHandler.get_algorithm_impls. Initial patch by Mathieu
  Dupuy.

- bpo-26167: Minimized overhead in copy.copy() and copy.deepcopy().
  Optimized copying and deepcopying bytearrays, NotImplemented, slices,
  short lists, tuples, dicts, sets.

- bpo-25718: Fixed pickling and copying the accumulate() iterator with total
  is None.

- bpo-26475: Fixed debugging output for regular expressions with the (?x)
  flag.

- bpo-26482: Allowed pickling recursive dequeues.

- bpo-26335: Make mmap.write() return the number of bytes written like other
  write methods.  Patch by Jakub Stasiak.

- bpo-26457: Fixed the subnets() methods in IP network classes for the case
  when resulting prefix length is equal to maximal prefix length. Based on
  patch by Xiang Zhang.

- bpo-26385: Remove the file if the internal open() call in
  NamedTemporaryFile() fails. Patch by Silent Ghost.

- bpo-26402: Fix XML-RPC client to retry when the server shuts down a
  persistent connection.  This was a regression related to the new
  http.client.RemoteDisconnected exception in 3.5.0a4.

- bpo-25913: Leading ``<~`` is optional now in base64.a85decode() with
  adobe=True.  Patch by Swati Jaiswal.

- bpo-26186: Remove an invalid type check in importlib.util.LazyLoader.

- bpo-26367: importlib.__import__() raises ImportError like
  builtins.__import__() when ``level`` is specified but without an
  accompanying package specified.

- bpo-26309: In the "socketserver" module, shut down the request (closing
  the connected socket) when verify_request() returns false.  Patch by Aviv
  Palivoda.

- bpo-23430: Change the socketserver module to only catch exceptions raised
  from a request handler that are derived from Exception (instead of
  BaseException). Therefore SystemExit and KeyboardInterrupt no longer
  trigger the handle_error() method, and will now to stop a single-threaded
  server.

- bpo-25995: os.walk() no longer uses FDs proportional to the tree depth.

- bpo-25994: Added the close() method and the support of the context manager
  protocol for the os.scandir() iterator.

- bpo-23992: multiprocessing: make MapResult not fail-fast upon exception.

- bpo-26243: Support keyword arguments to zlib.compress().  Patch by Aviv
  Palivoda.

- bpo-26117: The os.scandir() iterator now closes file descriptor not only
  when the iteration is finished, but when it was failed with error.

- bpo-25949: __dict__ for an OrderedDict instance is now created only when
  needed.

- bpo-25911: Restored support of bytes paths in os.walk() on Windows.

- bpo-26045: Add UTF-8 suggestion to error message when posting a
  non-Latin-1 string with http.client.

- bpo-26039: Added zipfile.ZipInfo.from_file() and zipinfo.ZipInfo.is_dir().
  Patch by Thomas Kluyver.

- bpo-12923: Reset FancyURLopener's redirect counter even if there is an
  exception. Based on patches by Brian Brazil and Daniel Rocco.

- bpo-25945: Fixed a crash when unpickle the functools.partial object with
  wrong state. Fixed a leak in failed functools.partial constructor. "args"
  and "keywords" attributes of functools.partial have now always types tuple
  and dict correspondingly.

- bpo-26202: copy.deepcopy() now correctly copies range() objects with
  non-atomic attributes.

- bpo-23076: Path.glob() now raises a ValueError if it's called with an
  invalid pattern. Patch by Thomas Nyberg.

- bpo-19883: Fixed possible integer overflows in zipimport.

- bpo-26227: On Windows, getnameinfo(), gethostbyaddr() and
  gethostbyname_ex() functions of the socket module now decode the hostname
  from the ANSI code page rather than UTF-8.

- bpo-26099: The site module now writes an error into stderr if
  sitecustomize module can be imported but executing the module raise an
  ImportError. Same change for usercustomize.

- bpo-26147: xmlrpc now works with strings not encodable with used non-UTF-8
  encoding.

- bpo-25935: Garbage collector now breaks reference loops with OrderedDict.

- bpo-16620: Fixed AttributeError in msilib.Directory.glob().

- bpo-26013: Added compatibility with broken protocol 2 pickles created in
  old Python 3 versions (3.4.3 and lower).

- bpo-26129: Deprecated accepting non-integers in grp.getgrgid().

- bpo-25850: Use cross-compilation by default for 64-bit Windows.

- bpo-25822: Add docstrings to the fields of urllib.parse results. Patch
  contributed by Swati Jaiswal.

- bpo-22642: Convert trace module option parsing mechanism to argparse.
  Patch contributed by SilentGhost.

- bpo-24705: Fix sysconfig._parse_makefile not expanding ${} vars appearing
  before $() vars.

- bpo-26069: Remove the deprecated apis in the trace module.

- bpo-22138: Fix mock.patch behavior when patching descriptors. Restore
  original values after patching. Patch contributed by Sean McCully.

- bpo-25672: In the ssl module, enable the SSL_MODE_RELEASE_BUFFERS mode
  option if it is safe to do so.

- bpo-26012: Don't traverse into symlinks for ``**`` pattern in
  pathlib.Path.[r]glob().

- bpo-24120: Ignore PermissionError when traversing a tree with
  pathlib.Path.[r]glob(). Patch by Ulrich Petri.

- bpo-21815: Accept ] characters in the data portion of imap responses, in
  order to handle the flags with square brackets accepted and produced by
  servers such as gmail.

- bpo-25447: fileinput now uses sys.stdin as-is if it does not have a buffer
  attribute (restores backward compatibility).

- bpo-25971: Optimized creating Fractions from floats by 2 times and from
  Decimals by 3 times.

- bpo-25802: Document as deprecated the remaining implementations of
  importlib.abc.Loader.load_module().

- bpo-25928: Add Decimal.as_integer_ratio().

- bpo-25447: Copying the lru_cache() wrapper object now always works,
  independently from the type of the wrapped object (by returning the
  original object unchanged).

- bpo-25768: Have the functions in compileall return booleans instead of
  ints and add proper documentation and tests for the return values.

- bpo-24103: Fixed possible use after free in ElementTree.XMLPullParser.

- bpo-25860: os.fwalk() no longer skips remaining directories when error
  occurs. Original patch by Samson Lee.

- bpo-25914: Fixed and simplified OrderedDict.__sizeof__.

- bpo-25869: Optimized deepcopying ElementTree; it is now 20 times faster.

- bpo-25873: Optimized iterating ElementTree.  Iterating elements
  Element.iter() is now 40% faster, iterating text Element.itertext() is now
  up to 2.5 times faster.

- bpo-25902: Fixed various refcount issues in ElementTree iteration.

- bpo-22227: The TarFile iterator is reimplemented using generator. This
  implementation is simpler that using class.

- bpo-25638: Optimized ElementTree.iterparse(); it is now 2x faster.
  Optimized ElementTree parsing; it is now 10% faster.

- bpo-25761: Improved detecting errors in broken pickle data.

- bpo-25717: Restore the previous behaviour of tolerating most fstat()
  errors when opening files.  This was a regression in 3.5a1, and stopped
  anonymous temporary files from working in special cases.

- bpo-24903: Fix regression in number of arguments compileall accepts when
  '-d' is specified.  The check on the number of arguments has been dropped
  completely as it never worked correctly anyway.

- bpo-25764: In the subprocess module, preserve any exception caused by
  fork() failure when preexec_fn is used.

- bpo-25771: Tweak the exception message for importlib.util.resolve_name()
  when 'package' isn't specified but necessary.

- bpo-6478: _strptime's regexp cache now is reset after changing timezone
  with time.tzset().

- bpo-14285: When executing a package with the "python -m package" option,
  and package initialization fails, a proper traceback is now reported.  The
  "runpy" module now lets exceptions from package initialization pass back
  to the caller, rather than raising ImportError.

- bpo-19771: Also in runpy and the "-m" option, omit the irrelevant message
  ". . . is a package and cannot be directly executed" if the package could
  not even be initialized (e.g. due to a bad ``*.pyc`` file).

- bpo-25177: Fixed problem with the mean of very small and very large
  numbers. As a side effect, statistics.mean and statistics.variance should
  be significantly faster.

- bpo-25718: Fixed copying object with state with boolean value is false.

- bpo-10131: Fixed deep copying of minidom documents.  Based on patch by
  Marian Ganisin.

- bpo-7990: dir() on ElementTree.Element now lists properties: "tag",
  "text", "tail" and "attrib".  Original patch by Santoso Wijaya.

- bpo-25725: Fixed a reference leak in pickle.loads() when unpickling
  invalid data including tuple instructions.

- bpo-25663: In the Readline completer, avoid listing duplicate global
  names, and search the global namespace before searching builtins.

- bpo-25688: Fixed file leak in ElementTree.iterparse() raising an error.

- bpo-23914: Fixed SystemError raised by unpickler on broken pickle data.

- bpo-25691: Fixed crash on deleting ElementTree.Element attributes.

- bpo-25624: ZipFile now always writes a ZIP_STORED header for directory
  entries.  Patch by Dingyuan Wang.

- bpo-25626: Change three zlib functions to accept sizes that fit in
  Py_ssize_t, but internally cap those sizes to UINT_MAX.  This resolves a
  regression in 3.5 where GzipFile.read() failed to read chunks larger than
  2 or 4 GiB.  The change affects the zlib.Decompress.decompress()
  max_length parameter, the zlib.decompress() bufsize parameter, and the
  zlib.Decompress.flush() length parameter.

- bpo-25583: Avoid incorrect errors raised by os.makedirs(exist_ok=True)
  when the OS gives priority to errors such as EACCES over EEXIST.

- bpo-25593: Change semantics of EventLoop.stop() in asyncio.

- bpo-6973: When we know a subprocess.Popen process has died, do not allow
  the send_signal(), terminate(), or kill() methods to do anything as they
  could potentially signal a different process.

- bpo-23883: Added missing APIs to __all__ to match the documented APIs for
  the following modules: calendar, csv, enum, fileinput, ftplib, logging,
  optparse, tarfile, threading and wave.  Also added a
  test.support.check__all__() helper. Patches by Jacek Kołodziej, Mauro S.
  M. Rodrigues and Joel Taddei.

- bpo-25590: In the Readline completer, only call getattr() once per
  attribute.  Also complete names of attributes such as properties and slots
  which are listed by dir() but not yet created on an instance.

- bpo-25498: Fix a crash when garbage-collecting ctypes objects created by
  wrapping a memoryview.  This was a regression made in 3.5a1.  Based on
  patch by Eryksun.

- bpo-25584: Added "escape" to the __all__ list in the glob module.

- bpo-25584: Fixed recursive glob() with patterns starting with ``**``.

- bpo-25446: Fix regression in smtplib's AUTH LOGIN support.

- bpo-18010: Fix the pydoc web server's module search function to handle
  exceptions from importing packages.

- bpo-25554: Got rid of circular references in regular expression parsing.

- bpo-18973: Command-line interface of the calendar module now uses argparse
  instead of optparse.

- bpo-25510: fileinput.FileInput.readline() now returns b'' instead of '' at
  the end if the FileInput was opened with binary mode. Patch by Ryosuke
  Ito.

- bpo-25503: Fixed inspect.getdoc() for inherited docstrings of properties.
  Original patch by John Mark Vandenberg.

- bpo-25515: Always use os.urandom as a source of randomness in uuid.uuid4.

- bpo-21827: Fixed textwrap.dedent() for the case when largest common
  whitespace is a substring of smallest leading whitespace. Based on patch
  by Robert Li.

- bpo-25447: The lru_cache() wrapper objects now can be copied and pickled
  (by returning the original object unchanged).

- bpo-25390: typing: Don't crash on Union[str, Pattern].

- bpo-25441: asyncio: Raise error from drain() when socket is closed.

- bpo-25410: Cleaned up and fixed minor bugs in C implementation of
  OrderedDict.

- bpo-25411: Improved Unicode support in SMTPHandler through better use of
  the email package. Thanks to user simon04 for the patch.

- Move the imp module from a PendingDeprecationWarning to
  DeprecationWarning.

- bpo-25407: Remove mentions of the formatter module being removed in Python
  3.6.

- bpo-25406: Fixed a bug in C implementation of OrderedDict.move_to_end()
  that caused segmentation fault or hang in iterating after moving several
  items to the start of ordered dict.

- bpo-25382: pickletools.dis() now outputs implicit memo index for the
  MEMOIZE opcode.

- bpo-25357: Add an optional newline parameter to binascii.b2a_base64().
  base64.b64encode() uses it to avoid a memory copy.

- bpo-24164: Objects that need calling ``__new__`` with keyword arguments,
  can now be pickled using pickle protocols older than protocol version 4.

- bpo-25364: zipfile now works in threads disabled builds.

- bpo-25328: smtpd's SMTPChannel now correctly raises a ValueError if both
  decode_data and enable_SMTPUTF8 are set to true.

- bpo-16099: RobotFileParser now supports Crawl-delay and Request-rate
  extensions.  Patch by Nikolay Bogoychev.

- bpo-25316: distutils raises OSError instead of DistutilsPlatformError when
  MSVC is not installed.

- bpo-25380: Fixed protocol for the STACK_GLOBAL opcode in
  pickletools.opcodes.

- bpo-23972: Updates asyncio datagram create method allowing reuseport and
  reuseaddr socket options to be set prior to binding the socket. Mirroring
  the existing asyncio create_server method the reuseaddr option for
  datagram sockets defaults to True if the O/S is 'posix' (except if the
  platform is Cygwin). Patch by Chris Laws.

- bpo-25304: Add asyncio.run_coroutine_threadsafe().  This lets you submit a
  coroutine to a loop from another thread, returning a
  concurrent.futures.Future.  By Vincent Michel.

- bpo-25232: Fix CGIRequestHandler to split the query from the URL at the
  first question mark (?) rather than the last. Patch from Xiang Zhang.

- bpo-24657: Prevent CGIRequestHandler from collapsing slashes in the query
  part of the URL as if it were a path. Patch from Xiang Zhang.

- bpo-25287: Don't add crypt.METHOD_CRYPT to crypt.methods if it's not
  supported. Check if it is supported, it may not be supported on OpenBSD
  for example.

- bpo-23600: Default implementation of tzinfo.fromutc() was returning wrong
  results in some cases.

- bpo-25203: Failed readline.set_completer_delims() no longer left the
  module in inconsistent state.

- bpo-25011: rlcompleter now omits private and special attribute names
  unless the prefix starts with underscores.

- bpo-25209: rlcompleter now can add a space or a colon after completed
  keyword.

- bpo-22241: timezone.utc name is now plain 'UTC', not 'UTC-00:00'.

- bpo-23517: fromtimestamp() and utcfromtimestamp() methods of
  datetime.datetime now round microseconds to nearest with ties going to
  nearest even integer (ROUND_HALF_EVEN), as round(float), instead of
  rounding towards -Infinity (ROUND_FLOOR).

- bpo-23552: Timeit now warns when there is substantial (4x) variance
  between best and worst times. Patch from Serhiy Storchaka.

- bpo-24633: site-packages/README -> README.txt.

- bpo-24879: help() and pydoc can now list named tuple fields in the order
  they were defined rather than alphabetically.  The ordering is determined
  by the _fields attribute if present.

- bpo-24874: Improve speed of itertools.cycle() and make its pickle more
  compact.

- Fix crash in itertools.cycle.__setstate__() when the first argument wasn't
  a list.

- bpo-20059: urllib.parse raises ValueError on all invalid ports. Patch by
  Martin Panter.

- bpo-24360: Improve __repr__ of argparse.Namespace() for invalid
  identifiers.  Patch by Matthias Bussonnier.

- bpo-23426: run_setup was broken in distutils. Patch from Alexander
  Belopolsky.

- bpo-13938: 2to3 converts StringTypes to a tuple. Patch from Mark Hammond.

- bpo-2091: open() accepted a 'U' mode string containing '+', but 'U' can
  only be used with 'r'. Patch from Jeff Balogh and John O'Connor.

- bpo-8585: improved tests for zipimporter2. Patch from Mark Lawrence.

- bpo-18622: unittest.mock.mock_open().reset_mock would recurse infinitely.
  Patch from Nicola Palumbo and Laurent De Buyst.

- bpo-24426: Fast searching optimization in regular expressions now works
  for patterns that starts with capturing groups.  Fast searching
  optimization now can't be disabled at compile time.

- bpo-23661: unittest.mock side_effects can now be exceptions again. This
  was a regression vs Python 3.4. Patch from Ignacio Rossi

- bpo-13248: Remove deprecated inspect.getmoduleinfo function.

- bpo-25578: Fix (another) memory leak in SSLSocket.getpeercer().

- bpo-25530: Disable the vulnerable SSLv3 protocol by default when creating
  ssl.SSLContext.

- bpo-25569: Fix memory leak in SSLSocket.getpeercert().

- bpo-25471: Sockets returned from accept() shouldn't appear to be
  nonblocking.

- bpo-25319: When threading.Event is reinitialized, the underlying condition
  should use a regular lock rather than a recursive lock.

- Skip getaddrinfo if host is already resolved. Patch by A. Jesse Jiryu
  Davis.

- bpo-26050: Add asyncio.StreamReader.readuntil() method. Patch by Марк
  Коренберг.

- bpo-25924: Avoid unnecessary serialization of getaddrinfo(3) calls on OS X
  versions 10.5 or higher.  Original patch by A. Jesse Jiryu Davis.

- bpo-26406: Avoid unnecessary serialization of getaddrinfo(3) calls on
  current versions of OpenBSD and NetBSD.  Patch by A. Jesse Jiryu Davis.

- bpo-26848: Fix asyncio/subprocess.communicate() to handle empty input.
  Patch by Jack O'Connor.

- bpo-27040: Add loop.get_exception_handler method

- bpo-27041: asyncio: Add loop.create_future method

IDLE
----

- bpo-20640: Add tests for idlelib.configHelpSourceEdit. Patch by Saimadhav
  Heblikar.

- In the 'IDLE-console differences' section of the IDLE doc, clarify how
  running with IDLE affects sys.modules and the standard streams.

- bpo-25507: fix incorrect change in IOBinding that prevented printing.
  Augment IOBinding htest to include all major IOBinding functions.

- bpo-25905: Revert unwanted conversion of ' to ’ RIGHT SINGLE QUOTATION
  MARK in README.txt and open this and NEWS.txt with 'ascii'. Re-encode
  CREDITS.txt to utf-8 and open it with 'utf-8'.

- bpo-15348: Stop the debugger engine (normally in a user process) before
  closing the debugger window (running in the IDLE process). This prevents
  the RuntimeErrors that were being caught and ignored.

- bpo-24455: Prevent IDLE from hanging when a) closing the shell while the
  debugger is active (15347); b) closing the debugger with the [X] button
  (15348); and c) activating the debugger when already active (24455). The
  patch by Mark Roseman does this by making two changes. 1. Suspend and
  resume the gui.interaction method with the tcl vwait mechanism intended
  for this purpose (instead of root.mainloop & .quit). 2. In gui.run, allow
  any existing interaction to terminate first.

- Change 'The program' to 'Your program' in an IDLE 'kill program?' message
  to make it clearer that the program referred to is the currently running
  user program, not IDLE itself.

- bpo-24750: Improve the appearance of the IDLE editor window status bar.
  Patch by Mark Roseman.

- bpo-25313: Change the handling of new built-in text color themes to better
  address the compatibility problem introduced by the addition of IDLE Dark.
  Consistently use the revised idleConf.CurrentTheme everywhere in idlelib.

- bpo-24782: Extension configuration is now a tab in the IDLE Preferences
  dialog rather than a separate dialog.  The former tabs are now a sorted
  list.  Patch by Mark Roseman.

- bpo-22726: Re-activate the config dialog help button with some content
  about the other buttons and the new IDLE Dark theme.

- bpo-24820: IDLE now has an 'IDLE Dark' built-in text color theme. It is
  more or less IDLE Classic inverted, with a cobalt blue background.
  Strings, comments, keywords, ... are still green, red, orange, ... . To
  use it with IDLEs released before November 2015, hit the 'Save as New
  Custom Theme' button and enter a new name, such as 'Custom Dark'.  The
  custom theme will work with any IDLE release, and can be modified.

- bpo-25224: README.txt is now an idlelib index for IDLE developers and
  curious users. The previous user content is now in the IDLE doc chapter.
  'IDLE' now means 'Integrated Development and Learning Environment'.

- bpo-24820: Users can now set breakpoint colors in Settings -> Custom
  Highlighting. Original patch by Mark Roseman.

- bpo-24972: Inactive selection background now matches active selection
  background, as configured by users, on all systems.  Found items are now
  always highlighted on Windows.  Initial patch by Mark Roseman.

- bpo-24570: Idle: make calltip and completion boxes appear on Macs affected
  by a tk regression.  Initial patch by Mark Roseman.

- bpo-24988: Idle ScrolledList context menus (used in debugger) now work on
  Mac Aqua. Patch by Mark Roseman.

- bpo-24801: Make right-click for context menu work on Mac Aqua. Patch by
  Mark Roseman.

- bpo-25173: Associate tkinter messageboxes with a specific widget. For Mac
  OSX, make them a 'sheet'.  Patch by Mark Roseman.

- bpo-25198: Enhance the initial html viewer now used for Idle Help.
  Properly indent fixed-pitch text (patch by Mark Roseman). Give code
  snippet a very Sphinx-like light blueish-gray background. Re-use initial
  width and height set by users for shell and editor. When the Table of
  Contents (TOC) menu is used, put the section header at the top of the
  screen.

- bpo-25225: Condense and rewrite Idle doc section on text colors.

- bpo-21995: Explain some differences between IDLE and console Python.

- bpo-22820: Explain need for *print* when running file from Idle editor.

- bpo-25224: Doc: augment Idle feature list and no-subprocess section.

- bpo-25219: Update doc for Idle command line options. Some were missing and
  notes were not correct.

- bpo-24861: Most of idlelib is private and subject to change. Use
  idleib.idle.* to start Idle. See idlelib.__init__.__doc__.

- bpo-25199: Idle: add synchronization comments for future maintainers.

- bpo-16893: Replace help.txt with help.html for Idle doc display. The new
  idlelib/help.html is rstripped Doc/build/html/library/idle.html. It looks
  better than help.txt and will better document Idle as released. The
  tkinter html viewer that works for this file was written by Rose Roseman.
  The now unused EditorWindow.HelpDialog class and helt.txt file are
  deprecated.

- bpo-24199: Deprecate unused idlelib.idlever with possible removal in 3.6.

- bpo-24790: Remove extraneous code (which also create 2 & 3 conflicts).

Documentation
-------------

- bpo-26736: Used HTTPS for external links in the documentation if possible.

- bpo-6953: Rework the Readline module documentation to group related
  functions together, and add more details such as what underlying Readline
  functions and variables are accessed.

- bpo-23606: Adds note to ctypes documentation regarding cdll.msvcrt.

- bpo-24952: Clarify the default size argument of stack_size() in the
  "threading" and "_thread" modules. Patch from Mattip.

- bpo-26014: Update 3.x packaging documentation: * "See also" links to the
  new docs are now provided in the legacy pages * links to setuptools
  documentation have been updated

Tests
-----

- bpo-21916: Added tests for the turtle module.  Patch by ingrid, Gregory
  Loyse and Jelle Zijlstra.

- bpo-26295: When using "python3 -m test --testdir=TESTDIR", regrtest
  doesn't add "test." prefix to test module names.

- bpo-26523: The multiprocessing thread pool (multiprocessing.dummy.Pool)
  was untested.

- bpo-26015: Added new tests for pickling iterators of mutable sequences.

- bpo-26325: Added test.support.check_no_resource_warning() to check that no
  ResourceWarning is emitted.

- bpo-25940: Changed test_ssl to use its internal local server more.  This
  avoids relying on svn.python.org, which recently changed root certificate.

- bpo-25616: Tests for OrderedDict are extracted from test_collections into
  separate file test_ordered_dict.

- bpo-25449: Added tests for OrderedDict subclasses.

- bpo-25188: Add -P/--pgo to test.regrtest to suppress error output when
  running the test suite for the purposes of a PGO build. Initial patch by
  Alecsandru Patrascu.

- bpo-22806: Add ``python -m test --list-tests`` command to list tests.

- bpo-18174: ``python -m test --huntrleaks ...`` now also checks for leak of
  file descriptors. Patch written by Richard Oudkerk.

- bpo-25260: Fix ``python -m test --coverage`` on Windows. Remove the list
  of ignored directories.

- ``PCbuild\rt.bat`` now accepts an unlimited number of arguments to pass
  along to regrtest.py.  Previously there was a limit of 9.

- bpo-26583: Skip test_timestamp_overflow in test_import if bytecode files
  cannot be written.

Build
-----

- bpo-21277: Don't try to link _ctypes with a ffi_convenience library.

- bpo-26884: Fix linking extension modules for cross builds. Patch by Xavier
  de Gaye.

- bpo-26932: Fixed support of RTLD_* constants defined as enum values, not
  via macros (in particular on Android).  Patch by Chi Hsuan Yen.

- bpo-22359: Disable the rules for running _freeze_importlib and pgen when
  cross-compiling.  The output of these programs is normally saved with the
  source code anyway, and is still regenerated when doing a native build.
  Patch by Xavier de Gaye.

- bpo-21668: Link audioop, _datetime, _ctypes_test modules to libm, except
  on Mac OS X. Patch written by Chi Hsuan Yen.

- bpo-25702: A --with-lto configure option has been added that will enable
  link time optimizations at build time during a make profile-opt. Some
  compilers and toolchains are known to not produce stable code when using
  LTO, be sure to test things thoroughly before relying on it. It can
  provide a few % speed up over profile-opt alone.

- bpo-26624: Adds validation of ucrtbase[d].dll version with warning for old
  versions.

- bpo-17603: Avoid error about nonexistent fileblocks.o file by using a
  lower-level check for st_blocks in struct stat.

- bpo-26079: Fixing the build output folder for tix-8.4.3.6. Patch by Bjoern
  Thiel.

- bpo-26465: Update Windows builds to use OpenSSL 1.0.2g.

- bpo-25348: Added ``--pgo`` and ``--pgo-job`` arguments to
  ``PCbuild\build.bat`` for building with Profile-Guided Optimization.  The
  old ``PCbuild\build_pgo.bat`` script is removed.

- bpo-25827: Add support for building with ICC to ``configure``, including a
  new ``--with-icc`` flag.

- bpo-25696: Fix installation of Python on UNIX with make -j9.

- bpo-24986: It is now possible to build Python on Windows without errors
  when external libraries are not available.

- bpo-24421: Compile Modules/_math.c once, before building extensions.
  Previously it could fail to compile properly if the math and cmath builds
  were concurrent.

- bpo-26465: Update OS X 10.5+ 32-bit-only installer to build and link with
  OpenSSL 1.0.2g.

- bpo-26268: Update Windows builds to use OpenSSL 1.0.2f.

- bpo-25136: Support Apple Xcode 7's new textual SDK stub libraries.

- bpo-24324: Do not enable unreachable code warnings when using gcc as the
  option does not work correctly in older versions of gcc and has been
  silently removed as of gcc-4.5.

Windows
-------

- bpo-27053: Updates make_zip.py to correctly generate library ZIP file.

- bpo-26268: Update the prepare_ssl.py script to handle OpenSSL releases
  that don't include the contents of the include directory (that is, 1.0.2e
  and later).

- bpo-26071: bdist_wininst created binaries fail to start and find 32bit
  Python

- bpo-26073: Update the list of magic numbers in launcher

- bpo-26065: Excludes venv from library when generating embeddable distro.

- bpo-25022: Removed very outdated PC/example_nt/ directory.

Tools/Demos
-----------

- bpo-26799: Fix python-gdb.py: don't get C types once when the Python code
  is loaded, but get C types on demand. The C types can change if
  python-gdb.py is loaded before the Python executable. Patch written by
  Thomas Ilsche.

- bpo-26271: Fix the Freeze tool to properly use flags passed through
  configure. Patch by Daniel Shaulov.

- bpo-26489: Add dictionary unpacking support to Tools/parser/unparse.py.
  Patch by Guo Ci Teo.

- bpo-26316: Fix variable name typo in Argument Clinic.

- bpo-25440: Fix output of python-config --extension-suffix.

- bpo-25154: The pyvenv script has been deprecated in favour of `python3 -m
  venv`.

C API
-----

- bpo-26312: SystemError is now raised in all programming bugs with using
  PyArg_ParseTupleAndKeywords().  RuntimeError did raised before in some
  programming bugs.

- bpo-26198: ValueError is now raised instead of TypeError on buffer
  overflow in parsing "es#" and "et#" format units.  SystemError is now
  raised instead of TypeError on programmatical error in parsing format
  string.


What's New in Python 3.5.5 final?
=================================

*Release date: 2018-02-04*

There were no new changes in version 3.5.5.



What's New in Python 3.5.5 release candidate 1?
===============================================

*Release date: 2018-01-23*

Security
--------

- bpo-32551: The ``sys.path[0]`` initialization change for bpo-29139 caused
  a regression by revealing an inconsistency in how sys.path is initialized
  when executing ``__main__`` from a zipfile, directory, or other import
  location. This is considered a potential security issue, as it may lead to
  privileged processes unexpectedly loading code from user controlled
  directories in situations where that was not previously the case. The
  interpreter now consistently avoids ever adding the import location's
  parent directory to ``sys.path``, and ensures no other ``sys.path``
  entries are inadvertently modified when inserting the import location
  named on the command line. (Originally reported as bpo-29723 against
  Python 3.6rc1, but it was missed at the time that the then upcoming Python
  3.5.4 release would also be affected)

- bpo-30657: Fixed possible integer overflow in PyBytes_DecodeEscape,
  CVE-2017-1000158. Original patch by Jay Bosamiya; rebased to Python 3 by
  Miro Hrončok.

- bpo-30947: Upgrade libexpat embedded copy from version 2.2.1 to 2.2.3 to
  get security fixes.

Core and Builtins
-----------------

- bpo-31095: Fix potential crash during GC caused by ``tp_dealloc`` which
  doesn't call ``PyObject_GC_UnTrack()``.

Library
-------

- bpo-32072: Fixed issues with binary plists: Fixed saving bytearrays.
  Identical objects will be saved only once. Equal references will be load
  as identical objects. Added support for saving and loading recursive data
  structures.

- bpo-31170: expat: Update libexpat from 2.2.3 to 2.2.4. Fix copying of
  partial characters for UTF-8 input (libexpat bug 115):
  https://github.com/libexpat/libexpat/issues/115


What's New in Python 3.5.4 final?
=================================

*Release date: 2017-08-07*

Library
-------

- bpo-30119: ftplib.FTP.putline() now throws ValueError on commands that
  contains CR or LF. Patch by Dong-hee Na.


What's New in Python 3.5.4 release candidate 1?
===============================================

*Release date: 2017-07-23*

Security
--------

- bpo-30730: Prevent environment variables injection in subprocess on
  Windows.  Prevent passing other environment variables and command
  arguments.

- bpo-30694: Upgrade expat copy from 2.2.0 to 2.2.1 to get fixes of multiple
  security vulnerabilities including: CVE-2017-9233 (External entity
  infinite loop DoS), CVE-2016-9063 (Integer overflow, re-fix),
  CVE-2016-0718 (Fix regression bugs from 2.2.0's fix to CVE-2016-0718) and
  CVE-2012-0876 (Counter hash flooding with SipHash). Note: the
  CVE-2016-5300 (Use os-specific entropy sources like getrandom) doesn't
  impact Python, since Python already gets entropy from the OS to set the
  expat secret using ``XML_SetHashSalt()``.

- bpo-30500: Fix urllib.parse.splithost() to correctly parse fragments. For
  example, ``splithost('//127.0.0.1#@evil.com/')`` now correctly returns the
  ``127.0.0.1`` host, instead of treating ``@evil.com`` as the host in an
  authentication (``login@host``).

- bpo-29591: Update expat copy from 2.1.1 to 2.2.0 to get fixes of
  CVE-2016-0718 and CVE-2016-4472. See
  https://sourceforge.net/p/expat/bugs/537/ for more information.

Core and Builtins
-----------------

- bpo-30876: Relative import from unloaded package now reimports the package
  instead of failing with SystemError.  Relative import from non-package now
  fails with ImportError rather than SystemError.

- bpo-30765: Avoid blocking in pthread_mutex_lock() when
  PyThread_acquire_lock() is asked not to block.

- bpo-27945: Fixed various segfaults with dict when input collections are
  mutated during searching, inserting or comparing.  Based on patches by
  Duane Griffin and Tim Mitchell.

- bpo-25794: Fixed type.__setattr__() and type.__delattr__() for
  non-interned attribute names.  Based on patch by Eryk Sun.

- bpo-29935: Fixed error messages in the index() method of tuple, list and
  deque when pass indices of wrong type.

- bpo-28876: ``bool(range)`` works even if ``len(range)`` raises
  :exc:`OverflowError`.

- bpo-29600: Fix wrapping coroutine return values in StopIteration.

- bpo-29537: Restore runtime compatibility with bytecode files generated by
  CPython 3.5.0 to 3.5.2, and adjust the eval loop to avoid the problems
  that could be caused by the malformed variant of the
  BUILD_MAP_UNPACK_WITH_CALL opcode that they may contain. Patch by Petr
  Viktorin, Serhiy Storchaka, and Nick Coghlan.

- bpo-28598: Support __rmod__ for subclasses of str being called before
  str.__mod__. Patch by Martijn Pieters.

- bpo-29602: Fix incorrect handling of signed zeros in complex constructor
  for complex subclasses and for inputs having a __complex__ method. Patch
  by Serhiy Storchaka.

- bpo-29347: Fixed possibly dereferencing undefined pointers when creating
  weakref objects.

- bpo-29438: Fixed use-after-free problem in key sharing dict.

- bpo-29319: Prevent RunMainFromImporter overwriting sys.path[0].

- bpo-29337: Fixed possible BytesWarning when compare the code objects.
  Warnings could be emitted at compile time.

- bpo-29478: If max_line_length=None is specified while using the Compat32
  policy, it is no longer ignored.  Patch by Mircea Cosbuc.

Library
-------

- bpo-29403: Fix ``unittest.mock``'s autospec to not fail on method-bound
  builtin functions.  Patch by Aaron Gallagher.

- bpo-30961: Fix decrementing a borrowed reference in tracemalloc.

- bpo-30886: Fix multiprocessing.Queue.join_thread(): it now waits until the
  thread completes, even if the thread was started by the same process which
  created the queue.

- bpo-29854: Fix segfault in readline when using readline's history-size
  option.  Patch by Nir Soffer.

- bpo-30807: signal.setitimer() may disable the timer when passed a tiny
  value. Tiny values (such as 1e-6) are valid non-zero values for
  setitimer(), which is specified as taking microsecond-resolution
  intervals. However, on some platform, our conversion routine could convert
  1e-6 into a zero interval, therefore disabling the timer instead of
  (re-)scheduling it.

- bpo-30441: Fix bug when modifying os.environ while iterating over it

- bpo-30532: Fix email header value parser dropping folding white space in
  certain cases.

- bpo-29169: Update zlib to 1.2.11.

- bpo-30879: os.listdir() and os.scandir() now emit bytes names when called
  with bytes-like argument.

- bpo-30746: Prohibited the '=' character in environment variable names in
  ``os.putenv()`` and ``os.spawn*()``.

- bpo-29755: Fixed the lgettext() family of functions in the gettext module.
  They now always return bytes.

- bpo-30645: Fix path calculation in imp.load_package(), fixing it for cases
  when a package is only shipped with bytecodes. Patch by Alexandru
  Ardelean.

- bpo-23890: unittest.TestCase.assertRaises() now manually breaks a
  reference cycle to not keep objects alive longer than expected.

- bpo-30149: inspect.signature() now supports callables with
  variable-argument parameters wrapped with partialmethod. Patch by Dong-hee
  Na.

- bpo-29931: Fixed comparison check for ipaddress.ip_interface objects.
  Patch by Sanjay Sundaresan.

- bpo-24484: Avoid race condition in multiprocessing cleanup.

- bpo-28994: The traceback no longer displayed for SystemExit raised in a
  callback registered by atexit.

- bpo-30508: Don't log exceptions if Task/Future "cancel()" method was
  called.

- bpo-28556: Updates to typing module: Add generic AsyncContextManager, add
  support for ContextManager on all versions. Original PRs by Jelle Zijlstra
  and Ivan Levkivskyi

- bpo-29870: Fix ssl sockets leaks when connection is aborted in asyncio/ssl
  implementation. Patch by Michaël Sghaïer.

- bpo-29743: Closing transport during handshake process leaks open socket.
  Patch by Nikolay Kim

- bpo-27585: Fix waiter cancellation in asyncio.Lock. Patch by Mathieu
  Sornay.

- bpo-30418: On Windows, subprocess.Popen.communicate() now also ignore
  EINVAL on stdin.write() if the child process is still running but closed
  the pipe.

- bpo-30378: Fix the problem that logging.handlers.SysLogHandler cannot
  handle IPv6 addresses.

- bpo-29960: Preserve generator state when _random.Random.setstate() raises
  an exception. Patch by Bryan Olson.

- bpo-30414: multiprocessing.Queue._feed background running thread do not
  break from main loop on exception.

- bpo-30003: Fix handling escape characters in HZ codec.  Based on patch by
  Ma Lin.

- bpo-30301: Fix AttributeError when using SimpleQueue.empty() under *spawn*
  and *forkserver* start methods.

- bpo-30329: imaplib and poplib now catch the Windows socket WSAEINVAL error
  (code 10022) on shutdown(SHUT_RDWR): An invalid operation was attempted.
  This error occurs sometimes on SSL connections.

- bpo-30375: Warnings emitted when compile a regular expression now always
  point to the line in the user code.  Previously they could point into
  inners of the re module if emitted from inside of groups or conditionals.

- bpo-30048: Fixed ``Task.cancel()`` can be ignored when the task is running
  coroutine and the coroutine returned without any more ``await``.

- bpo-29990: Fix range checking in GB18030 decoder.  Original patch by Ma
  Lin.

- bpo-26293: Change resulted because of zipfile breakage. (See also:
  bpo-29094)

- bpo-30243: Removed the __init__ methods of _json's scanner and encoder.
  Misusing them could cause memory leaks or crashes.  Now scanner and
  encoder objects are completely initialized in the __new__ methods.

- bpo-30185: Avoid KeyboardInterrupt tracebacks in forkserver helper process
  when Ctrl-C is received.

- bpo-28556: Various updates to typing module: add typing.NoReturn type, use
  WrapperDescriptorType, minor bug-fixes.  Original PRs by Jim
  Fasarakis-Hilliard and Ivan Levkivskyi.

- bpo-30205: Fix getsockname() for unbound AF_UNIX sockets on Linux.

- bpo-30070: Fixed leaks and crashes in errors handling in the parser
  module.

- bpo-30061: Fixed crashes in IOBase methods __next__() and readlines() when
  readline() or __next__() respectively return non-sizeable object. Fixed
  possible other errors caused by not checking results of PyObject_Size(),
  PySequence_Size(), or PyMapping_Size().

- bpo-30068: _io._IOBase.readlines will check if it's closed first when hint
  is present.

- bpo-29694: Fixed race condition in pathlib mkdir with flags parents=True.
  Patch by Armin Rigo.

- bpo-29692: Fixed arbitrary unchaining of RuntimeError exceptions in
  contextlib.contextmanager.  Patch by Siddharth Velankar.

- bpo-29998: Pickling and copying ImportError now preserves name and path
  attributes.

- bpo-29942: Fix a crash in itertools.chain.from_iterable when encountering
  long runs of empty iterables.

- bpo-27863: Fixed multiple crashes in ElementTree caused by race conditions
  and wrong types.

- bpo-28699: Fixed a bug in pools in multiprocessing.pool that raising an
  exception at the very first of an iterable may swallow the exception or
  make the program hang. Patch by Davin Potts and Xiang Zhang.

- bpo-25803: Avoid incorrect errors raised by Path.mkdir(exist_ok=True) when
  the OS gives priority to errors such as EACCES over EEXIST.

- bpo-29861: Release references to tasks, their arguments and their results
  as soon as they are finished in multiprocessing.Pool.

- bpo-29884: faulthandler: Restore the old sigaltstack during teardown.
  Patch by Christophe Zeitouny.

- bpo-25455: Fixed crashes in repr of recursive buffered file-like objects.

- bpo-29800: Fix crashes in partial.__repr__ if the keys of partial.keywords
  are not strings.  Patch by Michael Seifert.

- bpo-29742: get_extra_info() raises exception if get called on closed ssl
  transport. Patch by Nikolay Kim.

- bpo-8256: Fixed possible failing or crashing input() if attributes
  "encoding" or "errors" of sys.stdin or sys.stdout are not set or are not
  strings.

- bpo-28298: Fix a bug that prevented array 'Q', 'L' and 'I' from accepting
  big intables (objects that have __int__) as elements.  Patch by Oren
  Milman.

- bpo-29615: SimpleXMLRPCDispatcher no longer chains KeyError (or any other
  exception) to exception(s) raised in the dispatched methods. Patch by Petr
  Motejlek.

- bpo-29704: asyncio.subprocess.SubprocessStreamProtocol no longer closes
  before all pipes are closed.

- bpo-29703: Fix asyncio to support instantiation of new event loops in
  child processes.

- bpo-29376: Fix assertion error in threading._DummyThread.is_alive().

- bpo-29110: Fix file object leak in aifc.open() when file is given as a
  filesystem path and is not in valid AIFF format. Patch by Anthony Zhang.

- bpo-28961: Fix unittest.mock._Call helper: don't ignore the name parameter
  anymore. Patch written by Jiajun Huang.

- bpo-29532: Altering a kwarg dictionary passed to functools.partial() no
  longer affects a partial object after creation.

- bpo-28556: Various updates to typing module: typing.Counter,
  typing.ChainMap, improved ABC caching, etc. Original PRs by Jelle
  Zijlstra, Ivan Levkivskyi, Manuel Krebber, and Łukasz Langa.

- bpo-29100: Fix datetime.fromtimestamp() regression introduced in Python
  3.6.0: check minimum and maximum years.

- bpo-29519: Fix weakref spewing exceptions during interpreter shutdown when
  used with a rare combination of multiprocessing and custom codecs.

- bpo-29416: Prevent infinite loop in pathlib.Path.mkdir

- bpo-29444: Fixed out-of-bounds buffer access in the group() method of the
  match object. Based on patch by WGH.

- bpo-29335: Fix subprocess.Popen.wait() when the child process has exited
  to a stopped instead of terminated state (ex: when under ptrace).

- bpo-29290: Fix a regression in argparse that help messages would wrap at
  non-breaking spaces.

- bpo-28735: Fixed the comparison of mock.MagickMock with mock.ANY.

- bpo-29011: Fix an important omission by adding Deque to the typing module.

- bpo-29219: Fixed infinite recursion in the repr of uninitialized
  ctypes.CDLL instances.

- bpo-28969: Fixed race condition in C implementation of
  functools.lru_cache. KeyError could be raised when cached function with
  full cache was simultaneously called from different threads with the same
  uncached arguments.

- bpo-29142: In urllib.request, suffixes in no_proxy environment variable
  with leading dots could match related hostnames again (e.g. .b.c matches
  a.b.c). Patch by Milan Oberkirch.

Documentation
-------------

- bpo-30176: Add missing attribute related constants in curses
  documentation.

- bpo-26985: Add missing info of code object in inspect documentation.

- bpo-28929: Link the documentation to its source file on GitHub.

- bpo-25008: Document smtpd.py as effectively deprecated and add a pointer
  to aiosmtpd, a third-party asyncio-based replacement.

- bpo-26355: Add canonical header link on each page to corresponding major
  version of the documentation. Patch by Matthias Bussonnier.

- bpo-29349: Fix Python 2 syntax in code for building the documentation.

Tests
-----

- bpo-30822: Fix regrtest command line parser to allow passing -u
  extralargefile to run test_zipfile64.

- bpo-30383: regrtest: Enhance regrtest and backport features from the
  master branch. Add options: --coverage, --testdir, --list-tests (list test
  files, don't run them), --list-cases (list test identifiers, don't run
  them, :issue:`30523`), --matchfile (load a list of test filters from a
  text file, :issue:`30540`), --slowest (alias to --slow). Enhance output:
  add timestamp, test result, currently running tests, "Tests result: xxx"
  summary with total duration, etc. Fix reference leak hunting in regrtest,
  --huntrleaks: regrtest now warms up caches, create explicitly all internal
  singletons which are created on demand to prevent false positives when
  checking for reference leaks. (:issue:`30675`).

- bpo-30357: test_thread: setUp() now uses support.threading_setup() and
  support.threading_cleanup() to wait until threads complete to avoid random
  side effects on following tests. Initial patch written by Grzegorz
  Grzywacz.

- bpo-28087: Skip test_asyncore and test_eintr poll failures on macOS. Skip
  some tests of select.poll when running on macOS due to unresolved issues
  with the underlying system poll function on some macOS versions.

- bpo-30197: Enhanced functions swap_attr() and swap_item() in the
  test.support module. They now work when delete replaced attribute or item
  inside the with statement.  The old value of the attribute or item (or
  None if it doesn't exist) now will be assigned to the target of the "as"
  clause, if there is one.

- bpo-29571: to match the behaviour of the ``re.LOCALE`` flag,
  test_re.test_locale_flag now uses ``locale.getpreferredencoding(False)``
  to determine the candidate encoding for the test regex (allowing it to
  correctly skip the test when the default locale encoding is a multi-byte
  encoding)

Build
-----

- bpo-29243: Prevent unnecessary rebuilding of Python during ``make test``,
  ``make install`` and some other make targets when configured with
  ``--enable-optimizations``.

- bpo-23404: Don't regenerate generated files based on file modification
  time anymore: the action is now explicit. Replace ``make touch`` with
  ``make regen-all``.

- bpo-29643: Fix ``--enable-optimization`` didn't work.

Windows
-------

- bpo-30687: Locate msbuild.exe on Windows when building rather than
  vcvarsall.bat

- bpo-29392: Prevent crash when passing invalid arguments into msvcrt
  module.

C API
-----

- bpo-27867: Function PySlice_GetIndicesEx() is replaced with a macro if
  Py_LIMITED_API is set to the value between 0x03050400 and 0x03060000 (not
  including) or 0x03060100 or higher.

- bpo-29083: Fixed the declaration of some public API functions.
  PyArg_VaParse() and PyArg_VaParseTupleAndKeywords() were not available in
  limited API. PyArg_ValidateKeywordArguments(), PyArg_UnpackTuple() and
  Py_BuildValue() were not available in limited API of version < 3.3 when
  PY_SSIZE_T_CLEAN is defined.


What's New in Python 3.5.3 final?
=================================

*Release date: 2017-01-17*

There were no code changes between 3.5.3rc1 and 3.5.3 final.



What's New in Python 3.5.3 release candidate 1?
===============================================

*Release date: 2017-01-02*

Security
--------

- bpo-27278: Fix os.urandom() implementation using getrandom() on Linux.
  Truncate size to INT_MAX and loop until we collected enough random bytes,
  instead of casting a directly Py_ssize_t to int.

- bpo-22636: Avoid shell injection problems with ctypes.util.find_library().

Core and Builtins
-----------------

- bpo-29073: bytearray formatting no longer truncates on first null byte.

- bpo-28932: Do not include <sys/random.h> if it does not exist.

- bpo-28147: Fix a memory leak in split-table dictionaries: setattr() must
  not convert combined table into split table.

- bpo-25677: Correct the positioning of the syntax error caret for indented
  blocks. Based on patch by Michael Layzell.

- bpo-29000: Fixed bytes formatting of octals with zero padding in alternate
  form.

- bpo-28512: Fixed setting the offset attribute of SyntaxError by
  PyErr_SyntaxLocationEx() and PyErr_SyntaxLocationObject().

- bpo-28991: functools.lru_cache() was susceptible to an obscure reentrancy
  bug caused by a monkey-patched len() function.

- bpo-28648: Fixed crash in Py_DecodeLocale() in debug build on Mac OS X
  when decode astral characters.  Patch by Xiang Zhang.

- bpo-19398: Extra slash no longer added to sys.path components in case of
  empty compile-time PYTHONPATH components.

- bpo-28426: Fixed potential crash in PyUnicode_AsDecodedObject() in debug
  build.

- bpo-23782: Fixed possible memory leak in _PyTraceback_Add() and exception
  loss in PyTraceBack_Here().

- bpo-28379: Added sanity checks and tests for PyUnicode_CopyCharacters().
  Patch by Xiang Zhang.

- bpo-28376: The type of long range iterator is now registered as Iterator.
  Patch by Oren Milman.

- bpo-28376: The constructor of range_iterator now checks that step is not
  0. Patch by Oren Milman.

- bpo-26906: Resolving special methods of uninitialized type now causes
  implicit initialization of the type instead of a fail.

- bpo-18287: PyType_Ready() now checks that tp_name is not NULL. Original
  patch by Niklas Koep.

- bpo-24098: Fixed possible crash when AST is changed in process of
  compiling it.

- bpo-28350: String constants with null character no longer interned.

- bpo-26617: Fix crash when GC runs during weakref callbacks.

- bpo-27942: String constants now interned recursively in tuples and
  frozensets.

- bpo-21578: Fixed misleading error message when ImportError called with
  invalid keyword args.

- bpo-28203: Fix incorrect type in error message from ``complex(1.0,
  {2:3})``. Patch by Soumya Sharma.

- bpo-27955: Fallback on reading /dev/urandom device when the getrandom()
  syscall fails with EPERM, for example when blocked by SECCOMP.

- bpo-28131: Fix a regression in zipimport's compile_source().  zipimport
  should use the same optimization level as the interpreter.

- bpo-25221: Fix corrupted result from PyLong_FromLong(0) when Python is
  compiled with NSMALLPOSINTS = 0.

- bpo-25758: Prevents zipimport from unnecessarily encoding a filename
  (patch by Eryk Sun)

- bpo-28189: dictitems_contains no longer swallows compare errors. (Patch by
  Xiang Zhang)

- bpo-27812: Properly clear out a generator's frame's backreference to the
  generator to prevent crashes in frame.clear().

- bpo-27811: Fix a crash when a coroutine that has not been awaited is
  finalized with warnings-as-errors enabled.

- bpo-27587: Fix another issue found by PVS-Studio: Null pointer check after
  use of 'def' in _PyState_AddModule(). Initial patch by Christian Heimes.

- bpo-26020: set literal evaluation order did not match documented
  behaviour.

- bpo-27782: Multi-phase extension module import now correctly allows the
  ``m_methods`` field to be used to add module level functions to instances
  of non-module types returned from ``Py_create_mod``. Patch by Xiang Zhang.

- bpo-27936: The round() function accepted a second None argument for some
  types but not for others.  Fixed the inconsistency by accepting None for
  all numeric types.

- bpo-27487: Warn if a submodule argument to "python -m" or
  runpy.run_module() is found in sys.modules after parent packages are
  imported, but before the submodule is executed.

- bpo-27558: Fix a SystemError in the implementation of "raise" statement.
  In a brand new thread, raise a RuntimeError since there is no active
  exception to reraise. Patch written by Xiang Zhang.

- bpo-27419: Standard __import__() no longer look up "__import__" in globals
  or builtins for importing submodules or "from import".  Fixed handling an
  error of non-string package name.

- bpo-27083: Respect the PYTHONCASEOK environment variable under Windows.

- bpo-27514: Make having too many statically nested blocks a SyntaxError
  instead of SystemError.

- bpo-27473: Fixed possible integer overflow in bytes and bytearray
  concatenations. Patch by Xiang Zhang.

- bpo-27507: Add integer overflow check in bytearray.extend().  Patch by
  Xiang Zhang.

- bpo-27581: Don't rely on wrapping for overflow check in
  PySequence_Tuple().  Patch by Xiang Zhang.

- bpo-27443: __length_hint__() of bytearray iterators no longer return a
  negative integer for a resized bytearray.

- bpo-27942: Fix memory leak in codeobject.c

Library
-------

- bpo-15812: inspect.getframeinfo() now correctly shows the first line of a
  context. Patch by Sam Breese.

- bpo-29094: Offsets in a ZIP file created with extern file object and modes
  "w" and "x" now are relative to the start of the file.

- bpo-13051: Fixed recursion errors in large or resized
  curses.textpad.Textbox.  Based on patch by Tycho Andersen.

- bpo-29119: Fix weakrefs in the pure python version of
  collections.OrderedDict move_to_end() method. Contributed by Andra
  Bogildea.

- bpo-9770: curses.ascii predicates now work correctly with negative
  integers.

- bpo-28427: old keys should not remove new values from WeakValueDictionary
  when collecting from another thread.

- bpo-28923: Remove editor artifacts from Tix.py.

- bpo-28871: Fixed a crash when deallocate deep ElementTree.

- bpo-19542: Fix bugs in WeakValueDictionary.setdefault() and
  WeakValueDictionary.pop() when a GC collection happens in another thread.

- bpo-20191: Fixed a crash in resource.prlimit() when pass a sequence that
  doesn't own its elements as limits.

- bpo-28779: multiprocessing.set_forkserver_preload() would crash the
  forkserver process if a preloaded module instantiated some multiprocessing
  objects such as locks.

- bpo-28847: dbm.dumb now supports reading read-only files and no longer
  writes the index file when it is not changed.

- bpo-25659: In ctypes, prevent a crash calling the from_buffer() and
  from_buffer_copy() methods on abstract classes like Array.

- bpo-28732: Fix crash in os.spawnv() with no elements in args

- bpo-28485: Always raise ValueError for negative
  compileall.compile_dir(workers=...) parameter, even when multithreading is
  unavailable.

- bpo-28387: Fixed possible crash in _io.TextIOWrapper deallocator when the
  garbage collector is invoked in other thread.  Based on patch by Sebastian
  Cufre.

- bpo-27517: LZMA compressor and decompressor no longer raise exceptions if
  given empty data twice.  Patch by Benjamin Fogle.

- bpo-28549: Fixed segfault in curses's addch() with ncurses6.

- bpo-28449: tarfile.open() with mode "r" or "r:" now tries to open a tar
  file with compression before trying to open it without compression.
  Otherwise it had 50% chance failed with ignore_zeros=True.

- bpo-23262: The webbrowser module now supports Firefox 36+ and derived
  browsers.  Based on patch by Oleg Broytman.

- bpo-27939: Fixed bugs in tkinter.ttk.LabeledScale and tkinter.Scale caused
  by representing the scale as float value internally in Tk.  tkinter.IntVar
  now works if float value is set to underlying Tk variable.

- bpo-28255: calendar.TextCalendar().prmonth() no longer prints a space at
  the start of new line after printing a month's calendar.  Patch by Xiang
  Zhang.

- bpo-20491: The textwrap.TextWrapper class now honors non-breaking spaces.
  Based on patch by Kaarle Ritvanen.

- bpo-28353: os.fwalk() no longer fails on broken links.

- bpo-25464: Fixed HList.header_exists() in tkinter.tix module by addin a
  workaround to Tix library bug.

- bpo-28488: shutil.make_archive() no longer add entry "./" to ZIP archive.

- bpo-24452: Make webbrowser support Chrome on Mac OS X.

- bpo-20766: Fix references leaked by pdb in the handling of SIGINT
  handlers.

- bpo-26293: Fixed writing ZIP files that starts not from the start of the
  file.  Offsets in ZIP file now are relative to the start of the archive in
  conforming to the specification.

- bpo-28321: Fixed writing non-BMP characters with binary format in
  plistlib.

- bpo-28322: Fixed possible crashes when unpickle itertools objects from
  incorrect pickle data.  Based on patch by John Leitch.

- Fix possible integer overflows and crashes in the mmap module with unusual
  usage patterns.

- bpo-1703178: Fix the ability to pass the --link-objects option to the
  distutils build_ext command.

- bpo-28253: Fixed calendar functions for extreme months: 0001-01 and
  9999-12. Methods itermonthdays() and itermonthdays2() are reimplemented so
  that they don't call itermonthdates() which can cause datetime.date
  under/overflow.

- bpo-28275: Fixed possible use after free in the decompress() methods of
  the LZMADecompressor and BZ2Decompressor classes. Original patch by John
  Leitch.

- bpo-27897: Fixed possible crash in sqlite3.Connection.create_collation()
  if pass invalid string-like object as a name.  Patch by Xiang Zhang.

- bpo-18893: Fix invalid exception handling in Lib/ctypes/macholib/dyld.py.
  Patch by Madison May.

- bpo-27611: Fixed support of default root window in the tkinter.tix module.

- bpo-27348: In the traceback module, restore the formatting of exception
  messages like "Exception: None".  This fixes a regression introduced in
  3.5a2.

- bpo-25651: Allow falsy values to be used for msg parameter of subTest().

- bpo-27932: Prevent memory leak in win32_ver().

- Fix UnboundLocalError in socket._sendfile_use_sendfile.

- bpo-28075: Check for ERROR_ACCESS_DENIED in Windows implementation of
  os.stat().  Patch by Eryk Sun.

- bpo-25270: Prevent codecs.escape_encode() from raising SystemError when an
  empty bytestring is passed.

- bpo-28181: Get antigravity over HTTPS. Patch by Kaartic Sivaraam.

- bpo-25895: Enable WebSocket URL schemes in urllib.parse.urljoin. Patch by
  Gergely Imreh and Markus Holtermann.

- bpo-27599: Fixed buffer overrun in binascii.b2a_qp() and
  binascii.a2b_qp().

- bpo-19003: m email.generator now replaces only ``\r`` and/or ``\n`` line
  endings, per the RFC, instead of all unicode line endings.

- bpo-28019: itertools.count() no longer rounds non-integer step in range
  between 1.0 and 2.0 to 1.

- bpo-25969: Update the lib2to3 grammar to handle the unpacking
  generalizations added in 3.5.

- bpo-14977: mailcap now respects the order of the lines in the mailcap
  files ("first match"), as required by RFC 1542.  Patch by Michael Lazar.

- bpo-24594: Validates persist parameter when opening MSI database

- bpo-17582: xml.etree.ElementTree nows preserves whitespaces in attributes
  (Patch by Duane Griffin.  Reviewed and approved by Stefan Behnel.)

- bpo-28047: Fixed calculation of line length used for the base64 CTE in the
  new email policies.

- bpo-27445: Don't pass str(_charset) to MIMEText.set_payload(). Patch by
  Claude Paroz.

- bpo-22450: urllib now includes an ``Accept: */*`` header among the default
  headers. This makes the results of REST API requests more consistent and
  predictable especially when proxy servers are involved.

- lib2to3.pgen3.driver.load_grammar() now creates a stable cache file
  between runs given the same Grammar.txt input regardless of the hash
  randomization setting.

- bpo-27570: Avoid zero-length memcpy() etc calls with null source pointers
  in the "ctypes" and "array" modules.

- bpo-22233: Break email header lines *only* on the RFC specified CR and LF
  characters, not on arbitrary unicode line breaks.  This also fixes a bug
  in HTTP header parsing.

- bpo-27988: Fix email iter_attachments incorrect mutation of payload list.

- bpo-27691: Fix ssl module's parsing of GEN_RID subject alternative name
  fields in X.509 certs.

- bpo-27850: Remove 3DES from ssl module's default cipher list to counter
  measure sweet32 attack (CVE-2016-2183).

- bpo-27766: Add ChaCha20 Poly1305 to ssl module's default cipher list.
  (Required OpenSSL 1.1.0 or LibreSSL).

- bpo-26470: Port ssl and hashlib module to OpenSSL 1.1.0.

- Remove support for passing a file descriptor to os.access. It never worked
  but previously didn't raise.

- bpo-12885: Fix error when distutils encounters symlink.

- bpo-27881: Fixed possible bugs when setting
  sqlite3.Connection.isolation_level. Based on patch by Xiang Zhang.

- bpo-27861: Fixed a crash in sqlite3.Connection.cursor() when a factory
  creates not a cursor.  Patch by Xiang Zhang.

- bpo-19884: Avoid spurious output on OS X with Gnu Readline.

- bpo-27706: Restore deterministic behavior of random.Random().seed() for
  string seeds using seeding version 1.  Allows sequences of calls to
  random() to exactly match those obtained in Python 2. Patch by Nofar
  Schnider.

- bpo-10513: Fix a regression in Connection.commit().  Statements should not
  be reset after a commit.

- A new version of typing.py from https://github.com/python/typing:
  Collection (only for 3.6) (Issue #27598). Add FrozenSet to __all__
  (upstream #261). Fix crash in _get_type_vars() (upstream #259). Remove the
  dict constraint in ForwardRef._eval_type (upstream #252).

- bpo-27539: Fix unnormalised ``Fraction.__pow__`` result in the case of
  negative exponent and negative base.

- bpo-21718: cursor.description is now available for queries using CTEs.

- bpo-2466: posixpath.ismount now correctly recognizes mount points which
  the user does not have permission to access.

- bpo-27773: Correct some memory management errors server_hostname in
  _ssl.wrap_socket().

- bpo-26750: unittest.mock.create_autospec() now works properly for
  subclasses of property() and other data descriptors.

- In the curses module, raise an error if window.getstr() or window.instr()
  is passed a negative value.

- bpo-27783: Fix possible usage of uninitialized memory in
  operator.methodcaller.

- bpo-27774: Fix possible Py_DECREF on unowned object in _sre.

- bpo-27760: Fix possible integer overflow in binascii.b2a_qp.

- bpo-27758: Fix possible integer overflow in the _csv module for large
  record lengths.

- bpo-27568: Prevent HTTPoxy attack (CVE-2016-1000110). Ignore the
  HTTP_PROXY variable when REQUEST_METHOD environment is set, which
  indicates that the script is in CGI mode.

- bpo-27656: Do not assume sched.h defines any SCHED_* constants.

- bpo-27130: In the "zlib" module, fix handling of large buffers (typically
  4 GiB) when compressing and decompressing.  Previously, inputs were
  limited to 4 GiB, and compression and decompression operations did not
  properly handle results of 4 GiB.

- bpo-27533: Release GIL in nt._isdir

- bpo-17711: Fixed unpickling by the persistent ID with protocol 0. Original
  patch by Alexandre Vassalotti.

- bpo-27522: Avoid an unintentional reference cycle in email.feedparser.

- bpo-26844: Fix error message for imp.find_module() to refer to 'path'
  instead of 'name'. Patch by Lev Maximov.

- bpo-23804: Fix SSL zero-length recv() calls to not block and not raise an
  error about unclean EOF.

- bpo-27466: Change time format returned by http.cookie.time2netscape,
  confirming the netscape cookie format and making it consistent with
  documentation.

- bpo-26664: Fix activate.fish by removing mis-use of ``$``.

- bpo-22115: Fixed tracing Tkinter variables: trace_vdelete() with wrong
  mode no longer break tracing, trace_vinfo() now always returns a list of
  pairs of strings, tracing in the "u" mode now works.

- Fix a scoping issue in importlib.util.LazyLoader which triggered an
  UnboundLocalError when lazy-loading a module that was already put into
  sys.modules.

- bpo-27079: Fixed curses.ascii functions isblank(), iscntrl() and
  ispunct().

- bpo-26754: Some functions (compile() etc) accepted a filename argument
  encoded as an iterable of integers. Now only strings and byte-like objects
  are accepted.

- bpo-27048: Prevents distutils failing on Windows when environment
  variables contain non-ASCII characters

- bpo-27330: Fixed possible leaks in the ctypes module.

- bpo-27238: Got rid of bare excepts in the turtle module.  Original patch
  by Jelle Zijlstra.

- bpo-27122: When an exception is raised within the context being managed by
  a contextlib.ExitStack() and one of the exit stack generators catches and
  raises it in a chain, do not re-raise the original exception when exiting,
  let the new chained one through.  This avoids the :pep:`479` bug described
  in issue25782.

- bpo-26386: Fixed ttk.TreeView selection operations with item id's
  containing spaces.

- bpo-16182: Fix various functions in the "readline" module to use the
  locale encoding, and fix get_begidx() and get_endidx() to return code
  point indexes.

- bpo-27392: Add loop.connect_accepted_socket(). Patch by Jim Fulton.

- bpo-27930: Improved behaviour of logging.handlers.QueueListener. Thanks to
  Paulo Andrade and Petr Viktorin for the analysis and patch.

- bpo-21201: Improves readability of multiprocessing error message.  Thanks
  to Wojciech Walczak for patch.

- bpo-27456: asyncio: Set TCP_NODELAY by default.

- bpo-27906: Fix socket accept exhaustion during high TCP traffic. Patch by
  Kevin Conway.

- bpo-28174: Handle when SO_REUSEPORT isn't properly supported. Patch by
  Seth Michael Larson.

- bpo-26654: Inspect functools.partial in asyncio.Handle.__repr__. Patch by
  iceboy.

- bpo-26909: Fix slow pipes IO in asyncio. Patch by INADA Naoki.

- bpo-28176: Fix callbacks race in asyncio.SelectorLoop.sock_connect.

- bpo-27759: Fix selectors incorrectly retain invalid file descriptors.
  Patch by Mark Williams.

- bpo-28368: Refuse monitoring processes if the child watcher has no loop
  attached. Patch by Vincent Michel.

- bpo-28369: Raise RuntimeError when transport's FD is used with add_reader,
  add_writer, etc.

- bpo-28370: Speedup asyncio.StreamReader.readexactly. Patch by Коренберг
  Марк.

- bpo-28371: Deprecate passing asyncio.Handles to run_in_executor.

- bpo-28372: Fix asyncio to support formatting of non-python coroutines.

- bpo-28399: Remove UNIX socket from FS before binding. Patch by Коренберг
  Марк.

- bpo-27972: Prohibit Tasks to await on themselves.

- bpo-26923: Fix asyncio.Gather to refuse being cancelled once all children
  are done. Patch by Johannes Ebke.

- bpo-26796: Don't configure the number of workers for default threadpool
  executor. Initial patch by Hans Lawrenz.

- bpo-28600: Optimize loop.call_soon().

- bpo-28613: Fix get_event_loop() return the current loop if called from
  coroutines/callbacks.

- bpo-28639: Fix inspect.isawaitable to always return bool Patch by Justin
  Mayfield.

- bpo-28652: Make loop methods reject socket kinds they do not support.

- bpo-28653: Fix a refleak in functools.lru_cache.

- bpo-28703: Fix asyncio.iscoroutinefunction to handle Mock objects.

- bpo-24142: Reading a corrupt config file left the parser in an invalid
  state.  Original patch by Florian Höch.

- bpo-28990: Fix SSL hanging if connection is closed before handshake
  completed. (Patch by HoHo-Ho)

IDLE
----

- bpo-15308: Add 'interrupt execution' (^C) to Shell menu. Patch by Roger
  Serwy, updated by Bayard Randel.

- bpo-27922: Stop IDLE tests from 'flashing' gui widgets on the screen.

- Add version to title of IDLE help window.

- bpo-25564: In section on IDLE -- console differences, mention that using
  exec means that __builtins__ is defined for each statement.

- bpo-27714: text_textview and test_autocomplete now pass when re-run in the
  same process.  This occurs when test_idle fails when run with the -w
  option but without -jn.  Fix warning from test_config.

- bpo-25507: IDLE no longer runs buggy code because of its tkinter imports.
  Users must include the same imports required to run directly in Python.

- bpo-27452: add line counter and crc to IDLE configHandler test dump.

- bpo-27365: Allow non-ascii chars in IDLE NEWS.txt, for contributor names.

- bpo-27245: IDLE: Cleanly delete custom themes and key bindings.
  Previously, when IDLE was started from a console or by import, a cascade
  of warnings was emitted. Patch by Serhiy Storchaka.

C API
-----

- bpo-28808: PyUnicode_CompareWithASCIIString() now never raises exceptions.

- bpo-26754: PyUnicode_FSDecoder() accepted a filename argument encoded as
  an iterable of integers. Now only strings and bytes-like objects are
  accepted.

Documentation
-------------

- bpo-28513: Documented command-line interface of zipfile.

Tests
-----

- bpo-28950: Disallow -j0 to be combined with -T/-l/-M in regrtest command
  line arguments.

- bpo-28666: Now test.support.rmtree is able to remove unwritable or
  unreadable directories.

- bpo-23839: Various caches now are cleared before running every test file.

- bpo-28409: regrtest: fix the parser of command line arguments.

- bpo-27787: Call gc.collect() before checking each test for "dangling
  threads", since the dangling threads are weak references.

- bpo-27369: In test_pyexpat, avoid testing an error message detail that
  changed in Expat 2.2.0.

Tools/Demos
-----------

- bpo-27952: Get Tools/scripts/fixcid.py working with Python 3 and the
  current "re" module, avoid invalid Python backslash escapes, and fix a bug
  parsing escaped C quote signs.

- bpo-27332: Fixed the type of the first argument of module-level functions
  generated by Argument Clinic.  Patch by Petr Viktorin.

- bpo-27418: Fixed Tools/importbench/importbench.py.

Windows
-------

- bpo-28251: Improvements to help manuals on Windows.

- bpo-28110: launcher.msi has different product codes between 32-bit and
  64-bit

- bpo-25144: Ensures TargetDir is set before continuing with custom install.

- bpo-27469: Adds a shell extension to the launcher so that drag and drop
  works correctly.

- bpo-27309: Enabled proper Windows styles in python[w].exe manifest.

Build
-----

- bpo-29080: Removes hard dependency on hg.exe from PCBuild/build.bat

- bpo-23903: Added missed names to PC/python3.def.

- bpo-10656: Fix out-of-tree building on AIX.  Patch by Tristan Carel and
  Michael Haubenwallner.

- bpo-26359: Rename --with-optimiations to --enable-optimizations.

- bpo-28444: Fix missing extensions modules when cross compiling.

- bpo-28248: Update Windows build and OS X installers to use OpenSSL 1.0.2j.

- bpo-28258: Fixed build with Estonian locale (python-config and distclean
  targets in Makefile).  Patch by Arfrever Frehtes Taifersar Arahesis.

- bpo-26661: setup.py now detects system libffi with multiarch wrapper.

- bpo-28066: Fix the logic that searches build directories for generated
  include files when building outside the source tree.

- bpo-15819: Remove redundant include search directory option for building
  outside the source tree.

- bpo-27566: Fix clean target in freeze makefile (patch by Lisa Roach)

- bpo-27705: Update message in validate_ucrtbase.py

- bpo-27983: Cause lack of llvm-profdata tool when using clang as required
  for PGO linking to be a configure time error rather than make time when
  --with-optimizations is enabled.  Also improve our ability to find the
  llvm-profdata tool on MacOS and some Linuxes.

- bpo-26307: The profile-opt build now applies PGO to the built-in modules.

- bpo-26359: Add the --with-optimizations configure flag.

- bpo-27713: Suppress spurious build warnings when updating importlib's
  bootstrap files. Patch by Xiang Zhang

- bpo-25825: Correct the references to Modules/python.exp and ld_so_aix,
  which are required on AIX.  This updates references to an installation
  path that was changed in 3.2a4, and undoes changed references to the build
  tree that were made in 3.5.0a1.

- bpo-27453: CPP invocation in configure must use CPPFLAGS. Patch by Chi
  Hsuan Yen.

- bpo-27641: The configure script now inserts comments into the makefile to
  prevent the pgen and _freeze_importlib executables from being
  cross-compiled.

- bpo-26662: Set PYTHON_FOR_GEN in configure as the Python program to be
  used for file generation during the build.

- bpo-10910: Avoid C++ compilation errors on FreeBSD and OS X. Also update
  FreedBSD version checks for the original ctype UTF-8 workaround.

- bpo-28676: Prevent missing 'getentropy' declaration warning on macOS.
  Patch by Gareth Rees.


What's New in Python 3.5.2 final?
=================================

*Release date: 2016-06-26*

Core and Builtins
-----------------

- bpo-26930: Update Windows builds to use OpenSSL 1.0.2h.

Tests
-----

- bpo-26867: Ubuntu's openssl OP_NO_SSLv3 is forced on by default; fix test.

IDLE
----

- bpo-27365: Allow non-ascii in idlelib/NEWS.txt - minimal part for 3.5.2.


What's New in Python 3.5.2 release candidate 1?
===============================================

*Release date: 2016-06-12*

Security
--------

- bpo-26556: Update expat to 2.1.1, fixes CVE-2015-1283.

- Fix TLS stripping vulnerability in smtplib, CVE-2016-0772. Reported by
  Team Oststrom

- bpo-26839: On Linux, :func:`os.urandom` now calls ``getrandom()`` with
  ``GRND_NONBLOCK`` to fall back on reading ``/dev/urandom`` if the urandom
  entropy pool is not initialized yet. Patch written by Colm Buckley.

- bpo-26657: Fix directory traversal vulnerability with http.server on
  Windows.  This fixes a regression that was introduced in 3.3.4rc1 and
  3.4.0rc1.  Based on patch by Philipp Hagemeister.

- bpo-26313: ssl.py _load_windows_store_certs fails if windows cert store is
  empty. Patch by Baji.

- bpo-25939: On Windows open the cert store readonly in
  ssl.enum_certificates.

Core and Builtins
-----------------

- bpo-27066: Fixed SystemError if a custom opener (for open()) returns a
  negative number without setting an exception.

- bpo-20041: Fixed TypeError when frame.f_trace is set to None. Patch by
  Xavier de Gaye.

- bpo-26168: Fixed possible refleaks in failing Py_BuildValue() with the "N"
  format unit.

- bpo-26991: Fix possible refleak when creating a function with annotations.

- bpo-27039: Fixed bytearray.remove() for values greater than 127.  Patch by
  Joe Jevnik.

- bpo-23640: int.from_bytes() no longer bypasses constructors for
  subclasses.

- bpo-26811: gc.get_objects() no longer contains a broken tuple with NULL
  pointer.

- bpo-20120: Use RawConfigParser for .pypirc parsing, removing support for
  interpolation unintentionally added with move to Python 3. Behavior no
  longer does any interpolation in .pypirc files, matching behavior in
  Python 2.7 and Setuptools 19.0.

- bpo-26659: Make the builtin slice type support cycle collection.

- bpo-26718: super.__init__ no longer leaks memory if called multiple times.
  NOTE: A direct call of super.__init__ is not endorsed!

- bpo-25339: PYTHONIOENCODING now has priority over locale in setting the
  error handler for stdin and stdout.

- bpo-26494: Fixed crash on iterating exhausting iterators. Affected classes
  are generic sequence iterators, iterators of str, bytes, bytearray, list,
  tuple, set, frozenset, dict, OrderedDict, corresponding views and
  os.scandir() iterator.

- bpo-26581: If coding cookie is specified multiple times on a line in
  Python source code file, only the first one is taken to account.

- bpo-26464: Fix str.translate() when string is ASCII and first replacements
  removes character, but next replacement uses a non-ASCII character or a
  string longer than 1 character. Regression introduced in Python 3.5.0.

- bpo-22836: Ensure exception reports from PyErr_Display() and
  PyErr_WriteUnraisable() are sensible even when formatting them produces
  secondary errors.  This affects the reports produced by
  sys.__excepthook__() and when __del__() raises an exception.

- bpo-26302: Correct behavior to reject comma as a legal character for
  cookie names.

- bpo-4806: Avoid masking the original TypeError exception when using star
  (``*``) unpacking in function calls.  Based on patch by Hagen Fürstenau
  and Daniel Urban.

- bpo-27138: Fix the doc comment for FileFinder.find_spec().

- bpo-26154: Add a new private _PyThreadState_UncheckedGet() function to get
  the current Python thread state, but don't issue a fatal error if it is
  NULL. This new function must be used instead of accessing directly the
  _PyThreadState_Current variable.  The variable is no more exposed since
  Python 3.5.1 to hide the exact implementation of atomic C types, to avoid
  compiler issues.

- bpo-26194: Deque.insert() gave odd results for bounded deques that had
  reached their maximum size.  Now an IndexError will be raised when
  attempting to insert into a full deque.

- bpo-25843: When compiling code, don't merge constants if they are equal
  but have a different types. For example, ``f1, f2 = lambda: 1, lambda:
  1.0`` is now correctly compiled to two different functions: ``f1()``
  returns ``1`` (``int``) and ``f2()`` returns ``1.0`` (``int``), even if
  ``1`` and ``1.0`` are equal.

- bpo-22995: [UPDATE] Comment out the one of the pickleability tests in
  _PyObject_GetState() due to regressions observed in Cython-based projects.

- bpo-25961: Disallowed null characters in the type name.

- bpo-25973: Fix segfault when an invalid nonlocal statement binds a name
  starting with two underscores.

- bpo-22995: Instances of extension types with a state that aren't
  subclasses of list or dict and haven't implemented any pickle-related
  methods (__reduce__, __reduce_ex__, __getnewargs__, __getnewargs_ex__, or
  __getstate__), can no longer be pickled.  Including memoryview.

- bpo-20440: Massive replacing unsafe attribute setting code with special
  macro Py_SETREF.

- bpo-25766: Special method __bytes__() now works in str subclasses.

- bpo-25421: __sizeof__ methods of builtin types now use dynamic basic size.
  This allows sys.getsize() to work correctly with their subclasses with
  __slots__ defined.

- bpo-25709: Fixed problem with in-place string concatenation and utf-8
  cache.

- bpo-27147: Mention :pep:`420` in the importlib docs.

- bpo-24097: Fixed crash in object.__reduce__() if slot name is freed inside
  __getattr__.

- bpo-24731: Fixed crash on converting objects with special methods
  __bytes__, __trunc__, and __float__ returning instances of subclasses of
  bytes, int, and float to subclasses of bytes, int, and float
  correspondingly.

- bpo-26478: Fix semantic bugs when using binary operators with dictionary
  views and tuples.

- bpo-26171: Fix possible integer overflow and heap corruption in
  zipimporter.get_data().

- bpo-25660: Fix TAB key behaviour in REPL with readline.

- bpo-25887: Raise a RuntimeError when a coroutine object is awaited more
  than once.

- bpo-27243: Update the __aiter__ protocol: instead of returning an
  awaitable that resolves to an asynchronous iterator, the asynchronous
  iterator should be returned directly.  Doing the former will trigger a
  PendingDeprecationWarning.

Library
-------

- bpo-21386: Implement missing IPv4Address.is_global property.  It was
  documented since 07a5610bae9d.  Initial patch by Roger Luethi.

- bpo-20900: distutils register command now decodes HTTP responses
  correctly.  Initial patch by ingrid.

- A new version of typing.py provides several new classes and features:
  @overload outside stubs, Reversible, DefaultDict, Text, ContextManager,
  Type[], NewType(), TYPE_CHECKING, and numerous bug fixes (note that some
  of the new features are not yet implemented in mypy or other static
  analyzers). Also classes for :pep:`492` (Awaitable, AsyncIterable,
  AsyncIterator) have been added (in fact they made it into 3.5.1 but were
  never mentioned).

- bpo-25738: Stop http.server.BaseHTTPRequestHandler.send_error() from
  sending a message body for 205 Reset Content.  Also, don't send Content
  header fields in responses that don't have a body.  Patch by Susumu
  Koshiba.

- bpo-21313: Fix the "platform" module to tolerate when sys.version contains
  truncated build information.

- bpo-27164: In the zlib module, allow decompressing raw Deflate streams
  with a predefined zdict.  Based on patch by Xiang Zhang.

- bpo-24291: Fix wsgiref.simple_server.WSGIRequestHandler to completely
  write data to the client.  Previously it could do partial writes and
  truncate data.  Also, wsgiref.handler.ServerHandler can now handle stdout
  doing partial writes, but this is deprecated.

- bpo-26809: Add ``__all__`` to :mod:`string`.  Patch by Emanuel Barry.

- bpo-26373: subprocess.Popen.communicate now correctly ignores
  BrokenPipeError when the child process dies before .communicate() is
  called in more/all circumstances.

- bpo-21776: distutils.upload now correctly handles HTTPError. Initial patch
  by Claudiu Popa.

- bpo-27114: Fix SSLContext._load_windows_store_certs fails with
  PermissionError

- bpo-18383: Avoid creating duplicate filters when using filterwarnings and
  simplefilter. Based on patch by Alex Shkop.

- bpo-27057: Fix os.set_inheritable() on Android, ioctl() is blocked by
  SELinux and fails with EACCESS. The function now falls back to fcntl().
  Patch written by Michał Bednarski.

- bpo-27014: Fix infinite recursion using typing.py.  Thanks to Kalle Tuure!

- bpo-14132: Fix urllib.request redirect handling when the target only has a
  query string.  Original fix by Ján Janech.

- bpo-17214: The "urllib.request" module now percent-encodes non-ASCII bytes
  found in redirect target URLs.  Some servers send Location header fields
  with non-ASCII bytes, but "http.client" requires the request target to be
  ASCII-encodable, otherwise a UnicodeEncodeError is raised.  Based on patch
  by Christian Heimes.

- bpo-26892: Honor debuglevel flag in urllib.request.HTTPHandler. Patch
  contributed by Chi Hsuan Yen.

- bpo-22274: In the subprocess module, allow stderr to be redirected to
  stdout even when stdout is not redirected.  Patch by Akira Li.

- bpo-26807: mock_open 'files' no longer error on readline at end of file.
  Patch from Yolanda Robla.

- bpo-25745: Fixed leaking a userptr in curses panel destructor.

- bpo-26977: Removed unnecessary, and ignored, call to sum of squares helper
  in statistics.pvariance.

- bpo-26881: The modulefinder module now supports extended opcode arguments.

- bpo-23815: Fixed crashes related to directly created instances of types in
  _tkinter and curses.panel modules.

- bpo-17765: weakref.ref() no longer silently ignores keyword arguments.
  Patch by Georg Brandl.

- bpo-26873: xmlrpc now raises ResponseError on unsupported type tags
  instead of silently return incorrect result.

- bpo-26711: Fixed the comparison of plistlib.Data with other types.

- bpo-24114: Fix an uninitialized variable in `ctypes.util`. The bug only
  occurs on SunOS when the ctypes implementation searches for the `crle`
  program.  Patch by Xiang Zhang.  Tested on SunOS by Kees Bos.

- bpo-26864: In urllib.request, change the proxy bypass host checking
  against no_proxy to be case-insensitive, and to not match unrelated host
  names that happen to have a bypassed hostname as a suffix.  Patch by Xiang
  Zhang.

- bpo-26634: recursive_repr() now sets __qualname__ of wrapper.  Patch by
  Xiang Zhang.

- bpo-26804: urllib.request will prefer lower_case proxy environment
  variables over UPPER_CASE or Mixed_Case ones. Patch contributed by
  Hans-Peter Jansen.

- bpo-26837: assertSequenceEqual() now correctly outputs non-stringified
  differing items (like bytes in the -b mode).  This affects
  assertListEqual() and assertTupleEqual().

- bpo-26041: Remove "will be removed in Python 3.7" from deprecation
  messages of platform.dist() and platform.linux_distribution(). Patch by
  Kumaripaba Miyurusara Athukorala.

- bpo-26822: itemgetter, attrgetter and methodcaller objects no longer
  silently ignore keyword arguments.

- bpo-26733: Disassembling a class now disassembles class and static
  methods. Patch by Xiang Zhang.

- bpo-26801: Fix error handling in :func:`shutil.get_terminal_size`, catch
  :exc:`AttributeError` instead of :exc:`NameError`. Patch written by
  Emanuel Barry.

- bpo-24838: tarfile's ustar and gnu formats now correctly calculate name
  and link field limits for multibyte character encodings like utf-8.

- bpo-26717: Stop encoding Latin-1-ized WSGI paths with UTF-8.  Patch by
  Anthony Sottile.

- bpo-26735: Fix :func:`os.urandom` on Solaris 11.3 and newer when reading
  more than 1,024 bytes: call ``getrandom()`` multiple times with a limit of
  1024 bytes per call.

- bpo-16329: Add .webm to mimetypes.types_map.  Patch by Giampaolo Rodola'.

- bpo-13952: Add .csv to mimetypes.types_map.  Patch by Geoff Wilson.

- bpo-26709: Fixed Y2038 problem in loading binary PLists.

- bpo-23735: Handle terminal resizing with Readline 6.3+ by installing our
  own SIGWINCH handler.  Patch by Eric Price.

- bpo-26586: In http.server, respond with "413 Request header fields too
  large" if there are too many header fields to parse, rather than killing
  the connection and raising an unhandled exception.  Patch by Xiang Zhang.

- bpo-22854: Change BufferedReader.writable() and BufferedWriter.readable()
  to always return False.

- bpo-25195: Fix a regression in mock.MagicMock. _Call is a subclass of
  tuple (changeset 3603bae63c13 only works for classes) so we need to
  implement __ne__ ourselves.  Patch by Andrew Plummer.

- bpo-26644: Raise ValueError rather than SystemError when a negative length
  is passed to SSLSocket.recv() or read().

- bpo-23804: Fix SSL recv(0) and read(0) methods to return zero bytes
  instead of up to 1024.

- bpo-26616: Fixed a bug in datetime.astimezone() method.

- bpo-21925: :func:`warnings.formatwarning` now catches exceptions on
  ``linecache.getline(...)`` to be able to log :exc:`ResourceWarning`
  emitted late during the Python shutdown process.

- bpo-24266: Ctrl+C during Readline history search now cancels the search
  mode when compiled with Readline 7.

- bpo-26560: Avoid potential ValueError in BaseHandler.start_response.
  Initial patch by Peter Inglesby.

- bpo-26569: Fix :func:`pyclbr.readmodule` and :func:`pyclbr.readmodule_ex`
  to support importing packages.

- bpo-26499: Account for remaining Content-Length in HTTPResponse.readline()
  and read1(). Based on patch by Silent Ghost. Also document that
  HTTPResponse now supports these methods.

- bpo-25320: Handle sockets in directories unittest discovery is scanning.
  Patch from Victor van den Elzen.

- bpo-16181: cookiejar.http2time() now returns None if year is higher than
  datetime.MAXYEAR.

- bpo-26513: Fixes platform module detection of Windows Server

- bpo-23718: Fixed parsing time in week 0 before Jan 1.  Original patch by
  Tamás Bence Gedai.

- bpo-20589: Invoking Path.owner() and Path.group() on Windows now raise
  NotImplementedError instead of ImportError.

- bpo-26177: Fixed the keys() method for Canvas and Scrollbar widgets.

- bpo-15068: Got rid of excessive buffering in the fileinput module. The
  bufsize parameter is no longer used.

- bpo-2202: Fix UnboundLocalError in
  AbstractDigestAuthHandler.get_algorithm_impls. Initial patch by Mathieu
  Dupuy.

- bpo-25718: Fixed pickling and copying the accumulate() iterator with total
  is None.

- bpo-26475: Fixed debugging output for regular expressions with the (?x)
  flag.

- bpo-26457: Fixed the subnets() methods in IP network classes for the case
  when resulting prefix length is equal to maximal prefix length. Based on
  patch by Xiang Zhang.

- bpo-26385: Remove the file if the internal open() call in
  NamedTemporaryFile() fails. Patch by Silent Ghost.

- bpo-26402: Fix XML-RPC client to retry when the server shuts down a
  persistent connection.  This was a regression related to the new
  http.client.RemoteDisconnected exception in 3.5.0a4.

- bpo-25913: Leading ``<~`` is optional now in base64.a85decode() with
  adobe=True.  Patch by Swati Jaiswal.

- bpo-26186: Remove an invalid type check in importlib.util.LazyLoader.

- bpo-26367: importlib.__import__() raises SystemError like
  builtins.__import__() when ``level`` is specified but without an
  accompanying package specified.

- bpo-26309: In the "socketserver" module, shut down the request (closing
  the connected socket) when verify_request() returns false.  Patch by Aviv
  Palivoda.

- bpo-25995: os.walk() no longer uses FDs proportional to the tree depth.

- bpo-26117: The os.scandir() iterator now closes file descriptor not only
  when the iteration is finished, but when it was failed with error.

- bpo-25911: Restored support of bytes paths in os.walk() on Windows.

- bpo-26045: Add UTF-8 suggestion to error message when posting a
  non-Latin-1 string with http.client.

- bpo-12923: Reset FancyURLopener's redirect counter even if there is an
  exception. Based on patches by Brian Brazil and Daniel Rocco.

- bpo-25945: Fixed a crash when unpickle the functools.partial object with
  wrong state. Fixed a leak in failed functools.partial constructor. "args"
  and "keywords" attributes of functools.partial have now always types tuple
  and dict correspondingly.

- bpo-26202: copy.deepcopy() now correctly copies range() objects with
  non-atomic attributes.

- bpo-23076: Path.glob() now raises a ValueError if it's called with an
  invalid pattern. Patch by Thomas Nyberg.

- bpo-19883: Fixed possible integer overflows in zipimport.

- bpo-26227: On Windows, getnameinfo(), gethostbyaddr() and
  gethostbyname_ex() functions of the socket module now decode the hostname
  from the ANSI code page rather than UTF-8.

- bpo-26147: xmlrpc now works with strings not encodable with used non-UTF-8
  encoding.

- bpo-25935: Garbage collector now breaks reference loops with OrderedDict.

- bpo-16620: Fixed AttributeError in msilib.Directory.glob().

- bpo-26013: Added compatibility with broken protocol 2 pickles created in
  old Python 3 versions (3.4.3 and lower).

- bpo-25850: Use cross-compilation by default for 64-bit Windows.

- bpo-17633: Improve zipimport's support for namespace packages.

- bpo-24705: Fix sysconfig._parse_makefile not expanding ${} vars appearing
  before $() vars.

- bpo-22138: Fix mock.patch behavior when patching descriptors. Restore
  original values after patching. Patch contributed by Sean McCully.

- bpo-25672: In the ssl module, enable the SSL_MODE_RELEASE_BUFFERS mode
  option if it is safe to do so.

- bpo-26012: Don't traverse into symlinks for ``**`` pattern in
  pathlib.Path.[r]glob().

- bpo-24120: Ignore PermissionError when traversing a tree with
  pathlib.Path.[r]glob(). Patch by Ulrich Petri.

- bpo-25447: fileinput now uses sys.stdin as-is if it does not have a buffer
  attribute (restores backward compatibility).

- bpo-25447: Copying the lru_cache() wrapper object now always works,
  independently from the type of the wrapped object (by returning the
  original object unchanged).

- bpo-24103: Fixed possible use after free in ElementTree.XMLPullParser.

- bpo-25860: os.fwalk() no longer skips remaining directories when error
  occurs. Original patch by Samson Lee.

- bpo-25914: Fixed and simplified OrderedDict.__sizeof__.

- bpo-25902: Fixed various refcount issues in ElementTree iteration.

- bpo-25717: Restore the previous behaviour of tolerating most fstat()
  errors when opening files.  This was a regression in 3.5a1, and stopped
  anonymous temporary files from working in special cases.

- bpo-24903: Fix regression in number of arguments compileall accepts when
  '-d' is specified.  The check on the number of arguments has been dropped
  completely as it never worked correctly anyway.

- bpo-25764: In the subprocess module, preserve any exception caused by
  fork() failure when preexec_fn is used.

- bpo-6478: _strptime's regexp cache now is reset after changing timezone
  with time.tzset().

- bpo-14285: When executing a package with the "python -m package" option,
  and package initialization fails, a proper traceback is now reported.  The
  "runpy" module now lets exceptions from package initialization pass back
  to the caller, rather than raising ImportError.

- bpo-19771: Also in runpy and the "-m" option, omit the irrelevant message
  ". . . is a package and cannot be directly executed" if the package could
  not even be initialized (e.g. due to a bad ``*.pyc`` file).

- bpo-25177: Fixed problem with the mean of very small and very large
  numbers. As a side effect, statistics.mean and statistics.variance should
  be significantly faster.

- bpo-25718: Fixed copying object with state with boolean value is false.

- bpo-10131: Fixed deep copying of minidom documents.  Based on patch by
  Marian Ganisin.

- bpo-25725: Fixed a reference leak in pickle.loads() when unpickling
  invalid data including tuple instructions.

- bpo-25663: In the Readline completer, avoid listing duplicate global
  names, and search the global namespace before searching builtins.

- bpo-25688: Fixed file leak in ElementTree.iterparse() raising an error.

- bpo-23914: Fixed SystemError raised by unpickler on broken pickle data.

- bpo-25691: Fixed crash on deleting ElementTree.Element attributes.

- bpo-25624: ZipFile now always writes a ZIP_STORED header for directory
  entries.  Patch by Dingyuan Wang.

- Skip getaddrinfo if host is already resolved. Patch by A. Jesse Jiryu
  Davis.

- bpo-26050: Add asyncio.StreamReader.readuntil() method. Patch by Марк
  Коренберг.

- bpo-25924: Avoid unnecessary serialization of getaddrinfo(3) calls on OS X
  versions 10.5 or higher.  Original patch by A. Jesse Jiryu Davis.

- bpo-26406: Avoid unnecessary serialization of getaddrinfo(3) calls on
  current versions of OpenBSD and NetBSD.  Patch by A. Jesse Jiryu Davis.

- bpo-26848: Fix asyncio/subprocess.communicate() to handle empty input.
  Patch by Jack O'Connor.

- bpo-27040: Add loop.get_exception_handler method

- bpo-27041: asyncio: Add loop.create_future method

- bpo-27223: asyncio: Fix _read_ready and _write_ready to respect
  _conn_lost. Patch by Łukasz Langa.

- bpo-22970: asyncio: Fix inconsistency cancelling Condition.wait. Patch by
  David Coles.

IDLE
----

- bpo-5124: Paste with text selected now replaces the selection on X11. This
  matches how paste works on Windows, Mac, most modern Linux apps, and ttk
  widgets. Original patch by Serhiy Storchaka.

- bpo-24759: Make clear in idlelib.idle_test.__init__ that the directory is
  a private implementation of test.test_idle and tool for maintainers.

- bpo-27196: Stop 'ThemeChanged' warnings when running IDLE tests. These
  persisted after other warnings were suppressed in #20567. Apply Serhiy
  Storchaka's update_idletasks solution to four test files. Record this
  additional advice in idle_test/README.txt

- bpo-20567: Revise idle_test/README.txt with advice about avoiding tk
  warning messages from tests.  Apply advice to several IDLE tests.

- bpo-27117: Make colorizer htest and turtledemo work with dark themes. Move
  code for configuring text widget colors to a new function.

- bpo-26673: When tk reports font size as 0, change to size 10. Such fonts
  on Linux prevented the configuration dialog from opening.

- bpo-21939: Add test for IDLE's percolator. Original patch by Saimadhav
  Heblikar.

- bpo-21676: Add test for IDLE's replace dialog. Original patch by Saimadhav
  Heblikar.

- bpo-18410: Add test for IDLE's search dialog. Original patch by Westley
  Martínez.

- bpo-21703: Add test for IDLE's undo delegator. Original patch by Saimadhav
  Heblikar .

- bpo-27044: Add ConfigDialog.remove_var_callbacks to stop memory leaks.

- bpo-23977: Add more asserts to test_delegator.

- bpo-20640: Add tests for idlelib.configHelpSourceEdit. Patch by Saimadhav
  Heblikar.

- In the 'IDLE-console differences' section of the IDLE doc, clarify how
  running with IDLE affects sys.modules and the standard streams.

- bpo-25507: fix incorrect change in IOBinding that prevented printing.
  Augment IOBinding htest to include all major IOBinding functions.

- bpo-25905: Revert unwanted conversion of ' to ’ RIGHT SINGLE QUOTATION
  MARK in README.txt and open this and NEWS.txt with 'ascii'. Re-encode
  CREDITS.txt to utf-8 and open it with 'utf-8'.

Documentation
-------------

- bpo-19489: Moved the search box from the sidebar to the header and footer
  of each page. Patch by Ammar Askar.

- bpo-24136: Document the new :pep:`448` unpacking syntax of 3.5.

- bpo-26736: Used HTTPS for external links in the documentation if possible.

- bpo-6953: Rework the Readline module documentation to group related
  functions together, and add more details such as what underlying Readline
  functions and variables are accessed.

- bpo-23606: Adds note to ctypes documentation regarding cdll.msvcrt.

- bpo-25500: Fix documentation to not claim that __import__ is searched for
  in the global scope.

- bpo-26014: Update 3.x packaging documentation: * "See also" links to the
  new docs are now provided in the legacy pages * links to setuptools
  documentation have been updated

Tests
-----

- bpo-21916: Added tests for the turtle module.  Patch by ingrid, Gregory
  Loyse and Jelle Zijlstra.

- bpo-26523: The multiprocessing thread pool (multiprocessing.dummy.Pool)
  was untested.

- bpo-26015: Added new tests for pickling iterators of mutable sequences.

- bpo-26325: Added test.support.check_no_resource_warning() to check that no
  ResourceWarning is emitted.

- bpo-25940: Changed test_ssl to use self-signed.pythontest.net.  This
  avoids relying on svn.python.org, which recently changed root certificate.

- bpo-25616: Tests for OrderedDict are extracted from test_collections into
  separate file test_ordered_dict.

- bpo-26583: Skip test_timestamp_overflow in test_import if bytecode files
  cannot be written.

Build
-----

- bpo-26884: Fix linking extension modules for cross builds. Patch by Xavier
  de Gaye.

- bpo-22359: Disable the rules for running _freeze_importlib and pgen when
  cross-compiling.  The output of these programs is normally saved with the
  source code anyway, and is still regenerated when doing a native build.
  Patch by Xavier de Gaye.

- bpo-27229: Fix the cross-compiling pgen rule for in-tree builds.  Patch by
  Xavier de Gaye.

- bpo-21668: Link audioop, _datetime, _ctypes_test modules to libm, except
  on Mac OS X. Patch written by Xavier de Gaye.

- bpo-25702: A --with-lto configure option has been added that will enable
  link time optimizations at build time during a make profile-opt. Some
  compilers and toolchains are known to not produce stable code when using
  LTO, be sure to test things thoroughly before relying on it. It can
  provide a few % speed up over profile-opt alone.

- bpo-26624: Adds validation of ucrtbase[d].dll version with warning for old
  versions.

- bpo-17603: Avoid error about nonexistent fileblocks.o file by using a
  lower-level check for st_blocks in struct stat.

- bpo-26079: Fixing the build output folder for tix-8.4.3.6. Patch by Bjoern
  Thiel.

- bpo-26465: Update Windows builds to use OpenSSL 1.0.2g.

- bpo-24421: Compile Modules/_math.c once, before building extensions.
  Previously it could fail to compile properly if the math and cmath builds
  were concurrent.

- bpo-25348: Added ``--pgo`` and ``--pgo-job`` arguments to
  ``PCbuild\build.bat`` for building with Profile-Guided Optimization.  The
  old ``PCbuild\build_pgo.bat`` script is now deprecated, and simply calls
  ``PCbuild\build.bat --pgo %*``.

- bpo-25827: Add support for building with ICC to ``configure``, including a
  new ``--with-icc`` flag.

- bpo-25696: Fix installation of Python on UNIX with make -j9.

- bpo-26930: Update OS X 10.5+ 32-bit-only installer to build and link with
  OpenSSL 1.0.2h.

- bpo-26268: Update Windows builds to use OpenSSL 1.0.2f.

- bpo-25136: Support Apple Xcode 7's new textual SDK stub libraries.

- bpo-24324: Do not enable unreachable code warnings when using gcc as the
  option does not work correctly in older versions of gcc and has been
  silently removed as of gcc-4.5.

Windows
-------

- bpo-27053: Updates make_zip.py to correctly generate library ZIP file.

- bpo-26268: Update the prepare_ssl.py script to handle OpenSSL releases
  that don't include the contents of the include directory (that is, 1.0.2e
  and later).

- bpo-26071: bdist_wininst created binaries fail to start and find 32bit
  Python

- bpo-26073: Update the list of magic numbers in launcher

- bpo-26065: Excludes venv from library when generating embeddable distro.

- bpo-17500: Remove unused and outdated icons. (See also:
  https://github.com/python/pythondotorg/issues/945)

Tools/Demos
-----------

- bpo-26799: Fix python-gdb.py: don't get C types once when the Python code
  is loaded, but get C types on demand. The C types can change if
  python-gdb.py is loaded before the Python executable. Patch written by
  Thomas Ilsche.

- bpo-26271: Fix the Freeze tool to properly use flags passed through
  configure. Patch by Daniel Shaulov.

- bpo-26489: Add dictionary unpacking support to Tools/parser/unparse.py.
  Patch by Guo Ci Teo.

- bpo-26316: Fix variable name typo in Argument Clinic.


What's New in Python 3.5.1 final?
=================================

*Release date: 2015-12-06*

Core and Builtins
-----------------

- bpo-25709: Fixed problem with in-place string concatenation and utf-8
  cache.

Windows
-------

- bpo-25715: Python 3.5.1 installer shows wrong upgrade path and incorrect
  logic for launcher detection.


What's New in Python 3.5.1 release candidate 1?
===============================================

*Release date: 2015-11-22*

Core and Builtins
-----------------

- bpo-25630: Fix a possible segfault during argument parsing in functions
  that accept filesystem paths.

- bpo-23564: Fixed a partially broken sanity check in the _posixsubprocess
  internals regarding how fds_to_pass were passed to the child.  The bug had
  no actual impact as subprocess.py already avoided it.

- bpo-25388: Fixed tokenizer crash when processing undecodable source code
  with a null byte.

- bpo-25462: The hash of the key now is calculated only once in most
  operations in C implementation of OrderedDict.

- bpo-22995: Default implementation of __reduce__ and __reduce_ex__ now
  rejects builtin types with not defined __new__.

- bpo-25555: Fix parser and AST: fill lineno and col_offset of "arg" node
  when compiling AST from Python objects.

- bpo-24802: Avoid buffer overreads when int(), float(), compile(), exec()
  and eval() are passed bytes-like objects.  These objects are not
  necessarily terminated by a null byte, but the functions assumed they
  were.

- bpo-24726: Fixed a crash and leaking NULL in repr() of OrderedDict that
  was mutated by direct calls of dict methods.

- bpo-25449: Iterating OrderedDict with keys with unstable hash now raises
  KeyError in C implementations as well as in Python implementation.

- bpo-25395: Fixed crash when highly nested OrderedDict structures were
  garbage collected.

- bpo-25274: sys.setrecursionlimit() now raises a RecursionError if the new
  recursion limit is too low depending at the current recursion depth.
  Modify also the "lower-water mark" formula to make it monotonic. This mark
  is used to decide when the overflowed flag of the thread state is reset.

- bpo-24402: Fix input() to prompt to the redirected stdout when
  sys.stdout.fileno() fails.

- bpo-24806: Prevent builtin types that are not allowed to be subclassed
  from being subclassed through multiple inheritance.

- bpo-24848: Fixed a number of bugs in UTF-7 decoding of misformed data.

- bpo-25280: Import trace messages emitted in verbose (-v) mode are no
  longer formatted twice.

- bpo-25003: On Solaris 11.3 or newer, os.urandom() now uses the getrandom()
  function instead of the getentropy() function. The getentropy() function
  is blocking to generate very good quality entropy, os.urandom() doesn't
  need such high-quality entropy.

- bpo-25182: The stdprinter (used as sys.stderr before the io module is
  imported at startup) now uses the backslashreplace error handler.

- bpo-25131: Make the line number and column offset of set/dict literals and
  comprehensions correspond to the opening brace.

- bpo-25150: Hide the private _Py_atomic_xxx symbols from the public
  Python.h header to fix a compilation error with OpenMP.
  PyThreadState_GET() becomes an alias to PyThreadState_Get() to avoid ABI
  incompatibilities.

Library
-------

- bpo-25626: Change three zlib functions to accept sizes that fit in
  Py_ssize_t, but internally cap those sizes to UINT_MAX.  This resolves a
  regression in 3.5 where GzipFile.read() failed to read chunks larger than
  2 or 4 GiB.  The change affects the zlib.Decompress.decompress()
  max_length parameter, the zlib.decompress() bufsize parameter, and the
  zlib.Decompress.flush() length parameter.

- bpo-25583: Avoid incorrect errors raised by os.makedirs(exist_ok=True)
  when the OS gives priority to errors such as EACCES over EEXIST.

- bpo-25593: Change semantics of EventLoop.stop() in asyncio.

- bpo-6973: When we know a subprocess.Popen process has died, do not allow
  the send_signal(), terminate(), or kill() methods to do anything as they
  could potentially signal a different process.

- bpo-25590: In the Readline completer, only call getattr() once per
  attribute.

- bpo-25498: Fix a crash when garbage-collecting ctypes objects created by
  wrapping a memoryview.  This was a regression made in 3.5a1.  Based on
  patch by Eryksun.

- bpo-25584: Added "escape" to the __all__ list in the glob module.

- bpo-25584: Fixed recursive glob() with patterns starting with ``**``.

- bpo-25446: Fix regression in smtplib's AUTH LOGIN support.

- bpo-18010: Fix the pydoc web server's module search function to handle
  exceptions from importing packages.

- bpo-25554: Got rid of circular references in regular expression parsing.

- bpo-25510: fileinput.FileInput.readline() now returns b'' instead of '' at
  the end if the FileInput was opened with binary mode. Patch by Ryosuke
  Ito.

- bpo-25503: Fixed inspect.getdoc() for inherited docstrings of properties.
  Original patch by John Mark Vandenberg.

- bpo-25515: Always use os.urandom as a source of randomness in uuid.uuid4.

- bpo-21827: Fixed textwrap.dedent() for the case when largest common
  whitespace is a substring of smallest leading whitespace. Based on patch
  by Robert Li.

- bpo-25447: The lru_cache() wrapper objects now can be copied and pickled
  (by returning the original object unchanged).

- bpo-25390: typing: Don't crash on Union[str, Pattern].

- bpo-25441: asyncio: Raise error from drain() when socket is closed.

- bpo-25410: Cleaned up and fixed minor bugs in C implementation of
  OrderedDict.

- bpo-25411: Improved Unicode support in SMTPHandler through better use of
  the email package. Thanks to user simon04 for the patch.

- bpo-25407: Remove mentions of the formatter module being removed in Python
  3.6.

- bpo-25406: Fixed a bug in C implementation of OrderedDict.move_to_end()
  that caused segmentation fault or hang in iterating after moving several
  items to the start of ordered dict.

- bpo-25364: zipfile now works in threads disabled builds.

- bpo-25328: smtpd's SMTPChannel now correctly raises a ValueError if both
  decode_data and enable_SMTPUTF8 are set to true.

- bpo-25316: distutils raises OSError instead of DistutilsPlatformError when
  MSVC is not installed.

- bpo-25380: Fixed protocol for the STACK_GLOBAL opcode in
  pickletools.opcodes.

- bpo-23972: Updates asyncio datagram create method allowing reuseport and
  reuseaddr socket options to be set prior to binding the socket. Mirroring
  the existing asyncio create_server method the reuseaddr option for
  datagram sockets defaults to True if the O/S is 'posix' (except if the
  platform is Cygwin). Patch by Chris Laws.

- bpo-25304: Add asyncio.run_coroutine_threadsafe().  This lets you submit a
  coroutine to a loop from another thread, returning a
  concurrent.futures.Future.  By Vincent Michel.

- bpo-25232: Fix CGIRequestHandler to split the query from the URL at the
  first question mark (?) rather than the last. Patch from Xiang Zhang.

- bpo-24657: Prevent CGIRequestHandler from collapsing slashes in the query
  part of the URL as if it were a path. Patch from Xiang Zhang.

- bpo-24483: C implementation of functools.lru_cache() now calculates key's
  hash only once.

- bpo-22958: Constructor and update method of weakref.WeakValueDictionary
  now accept the self and the dict keyword arguments.

- bpo-22609: Constructor of collections.UserDict now accepts the self
  keyword argument.

- bpo-25111: Fixed comparison of traceback.FrameSummary.

- bpo-25262: Added support for BINBYTES8 opcode in Python implementation of
  unpickler. Highest 32 bits of 64-bit size for BINUNICODE8 and BINBYTES8
  opcodes no longer silently ignored on 32-bit platforms in C
  implementation.

- bpo-25034: Fix string.Formatter problem with auto-numbering and nested
  format_specs. Patch by Anthon van der Neut.

- bpo-25233: Rewrite the guts of asyncio.Queue and asyncio.Semaphore to be
  more understandable and correct.

- bpo-25203: Failed readline.set_completer_delims() no longer left the
  module in inconsistent state.

- bpo-23600: Default implementation of tzinfo.fromutc() was returning wrong
  results in some cases.

- bpo-23329: Allow the ssl module to be built with older versions of
  LibreSSL.

- Prevent overflow in _Unpickler_Read.

- bpo-25047: The XML encoding declaration written by Element Tree now
  respects the letter case given by the user. This restores the ability to
  write encoding names in uppercase like "UTF-8", which worked in Python 2.

- bpo-25135: Make deque_clear() safer by emptying the deque before clearing.
  This helps avoid possible reentrancy issues.

- bpo-19143: platform module now reads Windows version from kernel32.dll to
  avoid compatibility shims.

- bpo-25092: Fix datetime.strftime() failure when errno was already set to
  EINVAL.

- bpo-23517: Fix rounding in fromtimestamp() and utcfromtimestamp() methods
  of datetime.datetime: microseconds are now rounded to nearest with ties
  going to nearest even integer (ROUND_HALF_EVEN), instead of being rounding
  towards minus infinity (ROUND_FLOOR). It's important that these methods
  use the same rounding mode than datetime.timedelta to keep the property:
  (datetime(1970,1,1) + timedelta(seconds=t)) ==
  datetime.utcfromtimestamp(t). It also the rounding mode used by
  round(float) for example.

- bpo-25155: Fix datetime.datetime.now() and datetime.datetime.utcnow() on
  Windows to support date after year 2038. It was a regression introduced in
  Python 3.5.0.

- bpo-25108: Omitted internal frames in traceback functions print_stack(),
  format_stack(), and extract_stack() called without arguments.

- bpo-25118: Fix a regression of Python 3.5.0 in os.waitpid() on Windows.

- bpo-24684: socket.socket.getaddrinfo() now calls
  PyUnicode_AsEncodedString() instead of calling the encode() method of the
  host, to handle correctly custom string with an encode() method which
  doesn't return a byte string. The encoder of the IDNA codec is now called
  directly instead of calling the encode() method of the string.

- bpo-25060: Correctly compute stack usage of the BUILD_MAP opcode.

- bpo-24857: Comparing call_args to a long sequence now correctly returns a
  boolean result instead of raising an exception.  Patch by A Kaptur.

- bpo-23144: Make sure that HTMLParser.feed() returns all the data, even
  when convert_charrefs is True.

- bpo-24982: shutil.make_archive() with the "zip" format now adds entries
  for directories (including empty directories) in ZIP file.

- bpo-25019: Fixed a crash caused by setting non-string key of expat parser.
  Based on patch by John Leitch.

- bpo-16180: Exit pdb if file has syntax error, instead of trapping user in
  an infinite loop.  Patch by Xavier de Gaye.

- bpo-24891: Fix a race condition at Python startup if the file descriptor
  of stdin (0), stdout (1) or stderr (2) is closed while Python is creating
  sys.stdin, sys.stdout and sys.stderr objects. These attributes are now set
  to None if the creation of the object failed, instead of raising an
  OSError exception. Initial patch written by Marco Paolini.

- bpo-24992: Fix error handling and a race condition (related to garbage
  collection) in collections.OrderedDict constructor.

- bpo-24881: Fixed setting binary mode in Python implementation of FileIO on
  Windows and Cygwin.  Patch from Akira Li.

- bpo-25578: Fix (another) memory leak in SSLSocket.getpeercer().

- bpo-25530: Disable the vulnerable SSLv3 protocol by default when creating
  ssl.SSLContext.

- bpo-25569: Fix memory leak in SSLSocket.getpeercert().

- bpo-25471: Sockets returned from accept() shouldn't appear to be
  nonblocking.

- bpo-25319: When threading.Event is reinitialized, the underlying condition
  should use a regular lock rather than a recursive lock.

- bpo-21112: Fix regression in unittest.expectedFailure on subclasses. Patch
  from Berker Peksag.

- bpo-24764: cgi.FieldStorage.read_multi() now ignores the Content-Length
  header in part headers. Patch written by Peter Landry and reviewed by
  Pierre Quentel.

- bpo-24913: Fix overrun error in deque.index(). Found by John Leitch and
  Bryce Darling.

- bpo-24774: Fix docstring in http.server.test. Patch from Chiu-Hsiang Hsu.

- bpo-21159: Improve message in
  configparser.InterpolationMissingOptionError. Patch from Łukasz Langa.

- bpo-20362: Honour TestCase.longMessage correctly in assertRegex. Patch
  from Ilia Kurenkov.

- bpo-23572: Fixed functools.singledispatch on classes with falsy
  metaclasses.  Patch by Ethan Furman.

- asyncio: ensure_future() now accepts awaitable objects.

IDLE
----

- bpo-15348: Stop the debugger engine (normally in a user process) before
  closing the debugger window (running in the IDLE process). This prevents
  the RuntimeErrors that were being caught and ignored.

- bpo-24455: Prevent IDLE from hanging when a) closing the shell while the
  debugger is active (15347); b) closing the debugger with the [X] button
  (15348); and c) activating the debugger when already active (24455). The
  patch by Mark Roseman does this by making two changes. 1. Suspend and
  resume the gui.interaction method with the tcl vwait mechanism intended
  for this purpose (instead of root.mainloop & .quit). 2. In gui.run, allow
  any existing interaction to terminate first.

- Change 'The program' to 'Your program' in an IDLE 'kill program?' message
  to make it clearer that the program referred to is the currently running
  user program, not IDLE itself.

- bpo-24750: Improve the appearance of the IDLE editor window status bar.
  Patch by Mark Roseman.

- bpo-25313: Change the handling of new built-in text color themes to better
  address the compatibility problem introduced by the addition of IDLE Dark.
  Consistently use the revised idleConf.CurrentTheme everywhere in idlelib.

- bpo-24782: Extension configuration is now a tab in the IDLE Preferences
  dialog rather than a separate dialog.  The former tabs are now a sorted
  list.  Patch by Mark Roseman.

- bpo-22726: Re-activate the config dialog help button with some content
  about the other buttons and the new IDLE Dark theme.

- bpo-24820: IDLE now has an 'IDLE Dark' built-in text color theme. It is
  more or less IDLE Classic inverted, with a cobalt blue background.
  Strings, comments, keywords, ... are still green, red, orange, ... . To
  use it with IDLEs released before November 2015, hit the 'Save as New
  Custom Theme' button and enter a new name, such as 'Custom Dark'.  The
  custom theme will work with any IDLE release, and can be modified.

- bpo-25224: README.txt is now an idlelib index for IDLE developers and
  curious users. The previous user content is now in the IDLE doc chapter.
  'IDLE' now means 'Integrated Development and Learning Environment'.

- bpo-24820: Users can now set breakpoint colors in Settings -> Custom
  Highlighting. Original patch by Mark Roseman.

- bpo-24972: Inactive selection background now matches active selection
  background, as configured by users, on all systems.  Found items are now
  always highlighted on Windows.  Initial patch by Mark Roseman.

- bpo-24570: Idle: make calltip and completion boxes appear on Macs affected
  by a tk regression.  Initial patch by Mark Roseman.

- bpo-24988: Idle ScrolledList context menus (used in debugger) now work on
  Mac Aqua. Patch by Mark Roseman.

- bpo-24801: Make right-click for context menu work on Mac Aqua. Patch by
  Mark Roseman.

- bpo-25173: Associate tkinter messageboxes with a specific widget. For Mac
  OSX, make them a 'sheet'.  Patch by Mark Roseman.

- bpo-25198: Enhance the initial html viewer now used for Idle Help.
  Properly indent fixed-pitch text (patch by Mark Roseman). Give code
  snippet a very Sphinx-like light blueish-gray background. Re-use initial
  width and height set by users for shell and editor. When the Table of
  Contents (TOC) menu is used, put the section header at the top of the
  screen.

- bpo-25225: Condense and rewrite Idle doc section on text colors.

- bpo-21995: Explain some differences between IDLE and console Python.

- bpo-22820: Explain need for *print* when running file from Idle editor.

- bpo-25224: Doc: augment Idle feature list and no-subprocess section.

- bpo-25219: Update doc for Idle command line options. Some were missing and
  notes were not correct.

- bpo-24861: Most of idlelib is private and subject to change. Use
  idleib.idle.* to start Idle. See idlelib.__init__.__doc__.

- bpo-25199: Idle: add synchronization comments for future maintainers.

- bpo-16893: Replace help.txt with help.html for Idle doc display. The new
  idlelib/help.html is rstripped Doc/build/html/library/idle.html. It looks
  better than help.txt and will better document Idle as released. The
  tkinter html viewer that works for this file was written by Mark Roseman.
  The now unused EditorWindow.HelpDialog class and helt.txt file are
  deprecated.

- bpo-24199: Deprecate unused idlelib.idlever with possible removal in 3.6.

- bpo-24790: Remove extraneous code (which also create 2 & 3 conflicts).

Documentation
-------------

- bpo-22558: Add remaining doc links to source code for Python-coded
  modules. Patch by Yoni Lavi.

- bpo-12067: Rewrite Comparisons section in the Expressions chapter of the
  language reference. Some of the details of comparing mixed types were
  incorrect or ambiguous. NotImplemented is only relevant at a lower level
  than the Expressions chapter. Added details of comparing range() objects,
  and default behaviour and consistency suggestions for user-defined
  classes. Patch from Andy Maier.

- bpo-24952: Clarify the default size argument of stack_size() in the
  "threading" and "_thread" modules. Patch from Mattip.

- bpo-23725: Overhaul tempfile docs. Note deprecated status of mktemp. Patch
  from Zbigniew Jędrzejewski-Szmek.

- bpo-24808: Update the types of some PyTypeObject fields.  Patch by Joseph
  Weston.

- bpo-22812: Fix unittest discovery examples. Patch from Pam McA'Nulty.

Tests
-----

- bpo-25449: Added tests for OrderedDict subclasses.

- bpo-25099: Make test_compileall not fail when an entry on sys.path cannot
  be written to (commonly seen in administrative installs on Windows).

- bpo-23919: Prevents assert dialogs appearing in the test suite.

- ``PCbuild\rt.bat`` now accepts an unlimited number of arguments to pass
  along to regrtest.py.  Previously there was a limit of 9.

Build
-----

- bpo-24915: Add LLVM support for PGO builds and use the test suite to
  generate the profile data. Initial patch by Alecsandru Patrascu of Intel.

- bpo-24910: Windows MSIs now have unique display names.

- bpo-24986: It is now possible to build Python on Windows without errors
  when external libraries are not available.

Windows
-------

- bpo-25450: Updates shortcuts to start Python in installation directory.

- bpo-25164: Changes default all-users install directory to match per-user
  directory.

- bpo-25143: Improves installer error messages for unsupported platforms.

- bpo-25163: Display correct directory in installer when using non-default
  settings.

- bpo-25361: Disables use of SSE2 instructions in Windows 32-bit build

- bpo-25089: Adds logging to installer for case where launcher is not
  selected on upgrade.

- bpo-25165: Windows uninstallation should not remove launcher if other
  versions remain

- bpo-25112: py.exe launcher is missing icons

- bpo-25102: Windows installer does not precompile for -O or -OO.

- bpo-25081: Makes Back button in installer go back to upgrade page when
  upgrading.

- bpo-25091: Increases font size of the installer.

- bpo-25126: Clarifies that the non-web installer will download some
  components.

- bpo-25213: Restores requestedExecutionLevel to manifest to disable UAC
  virtualization.

- bpo-25022: Removed very outdated PC/example_nt/ directory.

Tools/Demos
-----------

- bpo-25440: Fix output of python-config --extension-suffix.


What's New in Python 3.5.0 final?
=================================

*Release date: 2015-09-13*

Build
-----

- bpo-25071: Windows installer should not require TargetDir parameter when
  installing quietly.


What's New in Python 3.5.0 release candidate 4?
===============================================

*Release date: 2015-09-09*

Library
-------

- bpo-25029: Fixes MemoryError in test_strptime.

Build
-----

- bpo-25027: Reverts partial-static build options and adds vcruntime140.dll
  to Windows installation.


What's New in Python 3.5.0 release candidate 3?
===============================================

*Release date: 2015-09-07*

Core and Builtins
-----------------

- bpo-24305: Prevent import subsystem stack frames from being counted by the
  warnings.warn(stacklevel=) parameter.

- bpo-24912: Prevent __class__ assignment to immutable built-in objects.

- bpo-24975: Fix AST compilation for :pep:`448` syntax.

Library
-------

- bpo-24917: time_strftime() buffer over-read.

- bpo-24748: To resolve a compatibility problem found with py2exe and
  pywin32, imp.load_dynamic() once again ignores previously loaded modules
  to support Python modules replacing themselves with extension modules.
  Patch by Petr Viktorin.

- bpo-24635: Fixed a bug in typing.py where isinstance([], typing.Iterable)
  would return True once, then False on subsequent calls.

- bpo-24989: Fixed buffer overread in BytesIO.readline() if a position is
  set beyond size.  Based on patch by John Leitch.

- bpo-24913: Fix overrun error in deque.index(). Found by John Leitch and
  Bryce Darling.


What's New in Python 3.5.0 release candidate 2?
===============================================

*Release date: 2015-08-25*

Core and Builtins
-----------------

- bpo-24769: Interpreter now starts properly when dynamic loading is
  disabled.  Patch by Petr Viktorin.

- bpo-21167: NAN operations are now handled correctly when python is
  compiled with ICC even if -fp-model strict is not specified.

- bpo-24492: A "package" lacking a __name__ attribute when trying to perform
  a ``from .. import ...`` statement will trigger an ImportError instead of
  an AttributeError.

Library
-------

- bpo-24847: Removes vcruntime140.dll dependency from Tcl/Tk.

- bpo-24839: platform._syscmd_ver raises DeprecationWarning

- bpo-24867: Fix Task.get_stack() for 'async def' coroutines


What's New in Python 3.5.0 release candidate 1?
===============================================

*Release date: 2015-08-09*

Core and Builtins
-----------------

- bpo-24667: Resize odict in all cases that the underlying dict resizes.

Library
-------

- bpo-24824: Signatures of codecs.encode() and codecs.decode() now are
  compatible with pydoc.

- bpo-24634: Importing uuid should not try to load libc on Windows

- bpo-24798: _msvccompiler.py doesn't properly support manifests

- bpo-4395: Better testing and documentation of binary operators. Patch by
  Martin Panter.

- bpo-23973: Update typing.py from GitHub repo.

- bpo-23004: mock_open() now reads binary data correctly when the type of
  read_data is bytes.  Initial patch by Aaron Hill.

- bpo-23888: Handle fractional time in cookie expiry. Patch by ssh.

- bpo-23652: Make it possible to compile the select module against the libc
  headers from the Linux Standard Base, which do not include some EPOLL
  macros.  Patch by Matt Frank.

- bpo-22932: Fix timezones in email.utils.formatdate. Patch from Dmitry
  Shachnev.

- bpo-23779: imaplib raises TypeError if authenticator tries to abort. Patch
  from Craig Holmquist.

- bpo-23319: Fix ctypes.BigEndianStructure, swap correctly bytes. Patch
  written by Matthieu Gautier.

- bpo-23254: Document how to close the TCPServer listening socket. Patch
  from Martin Panter.

- bpo-19450: Update Windows and OS X installer builds to use SQLite 3.8.11.

- bpo-17527: Add PATCH to wsgiref.validator. Patch from Luca Sbardella.

- bpo-24791: Fix grammar regression for call syntax: 'g(\*a or b)'.

IDLE
----

- bpo-23672: Allow Idle to edit and run files with astral chars in name.
  Patch by Mohd Sanad Zaki Rizvi.

- bpo-24745: Idle editor default font. Switch from Courier to
  platform-sensitive TkFixedFont.  This should not affect current customized
  font selections.  If there is a problem, edit
  $HOME/.idlerc/config-main.cfg and remove 'fontxxx' entries from [Editor
  Window].  Patch by Mark Roseman.

- bpo-21192: Idle editor. When a file is run, put its name in the restart
  bar. Do not print false prompts. Original patch by Adnan Umer.

- bpo-13884: Idle menus. Remove tearoff lines. Patch by Roger Serwy.

Documentation
-------------

- bpo-24129: Clarify the reference documentation for name resolution. This
  includes removing the assumption that readers will be familiar with the
  name resolution scheme Python used prior to the introduction of lexical
  scoping for function namespaces. Patch by Ivan Levkivskyi.

- bpo-20769: Improve reload() docs. Patch by Dorian Pula.

- bpo-23589: Remove duplicate sentence from the FAQ.  Patch by Yongzhi Pan.

- bpo-24729: Correct IO tutorial to match implementation regarding encoding
  parameter to open function.

Tests
-----

- bpo-24751: When running regrtest with the ``-w`` command line option, a
  test run is no longer marked as a failure if all tests succeed when
  re-run.


What's New in Python 3.5.0 beta 4?
==================================

*Release date: 2015-07-26*

Core and Builtins
-----------------

- bpo-23573: Restored optimization of bytes.rfind() and bytearray.rfind()
  for single-byte argument on Linux.

- bpo-24569: Make :pep:`448` dictionary evaluation more consistent.

- bpo-24583: Fix crash when set is mutated while being updated.

- bpo-24407: Fix crash when dict is mutated while being updated.

- bpo-24619: New approach for tokenizing async/await. As a consequence, it
  is now possible to have one-line 'async def foo(): await ..' functions.

- bpo-24687: Plug refleak on SyntaxError in function parameters annotations.

- bpo-15944: memoryview: Allow arbitrary formats when casting to bytes.
  Patch by Martin Panter.

Library
-------

- bpo-23441: rcompleter now prints a tab character instead of displaying
  possible completions for an empty word.  Initial patch by Martin Sekera.

- bpo-24683: Fixed crashes in _json functions called with arguments of
  inappropriate type.

- bpo-21697: shutil.copytree() now correctly handles symbolic links that
  point to directories.  Patch by Eduardo Seabra and Thomas Kluyver.

- bpo-14373: Fixed segmentation fault when gc.collect() is called during
  constructing lru_cache (C implementation).

- bpo-24695: Fix a regression in traceback.print_exception().  If
  exc_traceback is None we shouldn't print a traceback header like described
  in the documentation.

- bpo-24620: Random.setstate() now validates the value of state last
  element.

- bpo-22485: Fixed an issue that caused `inspect.getsource` to return
  incorrect results on nested functions.

- bpo-22153: Improve unittest docs. Patch from Martin Panter and evilzero.

- bpo-24580: Symbolic group references to open group in re patterns now are
  explicitly forbidden as well as numeric group references.

- bpo-24206: Fixed __eq__ and __ne__ methods of inspect classes.

- bpo-24631: Fixed regression in the timeit module with multiline setup.

- bpo-18622: unittest.mock.mock_open().reset_mock would recurse infinitely.
  Patch from Nicola Palumbo and Laurent De Buyst.

- bpo-23661: unittest.mock side_effects can now be exceptions again. This
  was a regression vs Python 3.4. Patch from Ignacio Rossi

- bpo-24608: chunk.Chunk.read() now always returns bytes, not str.

- bpo-18684: Fixed reading out of the buffer in the re module.

- bpo-24259: tarfile now raises a ReadError if an archive is truncated
  inside a data segment.

- bpo-15014: SMTP.auth() and SMTP.login() now support RFC 4954's optional
  initial-response argument to the SMTP AUTH command.

- bpo-24669: Fix inspect.getsource() for 'async def' functions. Patch by Kai
  Groner.

- bpo-24688: ast.get_docstring() for 'async def' functions.

Build
-----

- bpo-24603: Update Windows builds and OS X 10.5 installer to use OpenSSL
  1.0.2d.


What's New in Python 3.5.0 beta 3?
==================================

*Release date: 2015-07-05*

Core and Builtins
-----------------

- bpo-24467: Fixed possible buffer over-read in bytearray. The bytearray
  object now always allocates place for trailing null byte and it's buffer
  now is always null-terminated.

- Upgrade to Unicode 8.0.0.

- bpo-24345: Add Py_tp_finalize slot for the stable ABI.

- bpo-24400: Introduce a distinct type for :pep:`492` coroutines; add
  types.CoroutineType, inspect.getcoroutinestate,
  inspect.getcoroutinelocals; coroutines no longer use CO_GENERATOR flag;
  sys.set_coroutine_wrapper works only for 'async def' coroutines;
  inspect.iscoroutine no longer uses collections.abc.Coroutine, it's
  intended to test for pure 'async def' coroutines only; add new opcode:
  GET_YIELD_FROM_ITER; fix generators wrapper used in types.coroutine to be
  instance of collections.abc.Generator; collections.abc.Awaitable and
  collections.abc.Coroutine can no longer be used to detect generator-based
  coroutines--use inspect.isawaitable instead.

- bpo-24450: Add gi_yieldfrom to generators and cr_await to coroutines.
  Contributed by Benno Leslie and Yury Selivanov.

- bpo-19235: Add new RecursionError exception. Patch by Georg Brandl.

Library
-------

- bpo-21750: mock_open.read_data can now be read from each instance, as it
  could in Python 3.3.

- bpo-24552: Fix use after free in an error case of the _pickle module.

- bpo-24514: tarfile now tolerates number fields consisting of only
  whitespace.

- bpo-19176: Fixed doctype() related bugs in C implementation of
  ElementTree. A deprecation warning no longer issued by XMLParser subclass
  with default doctype() method.  Direct call of doctype() now issues a
  warning.  Parser's doctype() now is not called if target's doctype() is
  called.  Based on patch by Martin Panter.

- bpo-20387: Restore semantic round-trip correctness in tokenize/untokenize
  for tab-indented blocks.

- bpo-24456: Fixed possible buffer over-read in adpcm2lin() and lin2adpcm()
  functions of the audioop module.

- bpo-24336: The contextmanager decorator now works with functions with
  keyword arguments called "func" and "self".  Patch by Martin Panter.

- bpo-24522: Fix possible integer overflow in json accelerator module.

- bpo-24489: ensure a previously set C errno doesn't disturb cmath.polar().

- bpo-24408: Fixed AttributeError in measure() and metrics() methods of
  tkinter.Font.

- bpo-14373: C implementation of functools.lru_cache() now can be used with
  methods.

- bpo-24347: Set KeyError if PyDict_GetItemWithError returns NULL.

- bpo-24348: Drop superfluous incref/decref.

- bpo-24359: Check for changed OrderedDict size during iteration.

- bpo-24368: Support keyword arguments in OrderedDict methods.

- bpo-24362: Simplify the C OrderedDict fast nodes resize logic.

- bpo-24377: Fix a ref leak in OrderedDict.__repr__.

- bpo-24369: Defend against key-changes during iteration.

Tests
-----

- bpo-24373: _testmultiphase and xxlimited now use tp_traverse and
  tp_finalize to avoid reference leaks encountered when combining tp_dealloc
  with PyType_FromSpec (see issue #16690 for details)

Documentation
-------------

- bpo-24458: Update documentation to cover multi-phase initialization for
  extension modules (PEP 489). Patch by Petr Viktorin.

- bpo-24351: Clarify what is meant by "identifier" in the context of
  string.Template instances.

Build
-----

- bpo-24432: Update Windows builds and OS X 10.5 installer to use OpenSSL
  1.0.2c.


What's New in Python 3.5.0 beta 2?
==================================

*Release date: 2015-05-31*

Core and Builtins
-----------------

- bpo-24284: The startswith and endswith methods of the str class no longer
  return True when finding the empty string and the indexes are completely
  out of range.

- bpo-24115: Update uses of PyObject_IsTrue(), PyObject_Not(),
  PyObject_IsInstance(), PyObject_RichCompareBool() and _PyDict_Contains()
  to check for and handle errors correctly.

- bpo-24328: Fix importing one character extension modules.

- bpo-11205: In dictionary displays, evaluate the key before the value.

- bpo-24285: Fixed regression that prevented importing extension modules
  from inside packages. Patch by Petr Viktorin.

Library
-------

- bpo-23247: Fix a crash in the StreamWriter.reset() of CJK codecs.

- bpo-24270: Add math.isclose() and cmath.isclose() functions as per
  :pep:`485`. Contributed by Chris Barker and Tal Einat.

- bpo-5633: Fixed timeit when the statement is a string and the setup is
  not.

- bpo-24326: Fixed audioop.ratecv() with non-default weightB argument.
  Original patch by David Moore.

- bpo-16991: Add a C implementation of OrderedDict.

- bpo-23934: Fix inspect.signature to fail correctly for builtin types
  lacking signature information.  Initial patch by James Powell.


What's New in Python 3.5.0 beta 1?
==================================

*Release date: 2015-05-24*

Core and Builtins
-----------------

- bpo-24276: Fixed optimization of property descriptor getter.

- bpo-24268: PEP 489: Multi-phase extension module initialization. Patch by
  Petr Viktorin.

- bpo-23955: Add pyvenv.cfg option to suppress registry/environment lookup
  for generating sys.path on Windows.

- bpo-24257: Fixed system error in the comparison of faked
  types.SimpleNamespace.

- bpo-22939: Fixed integer overflow in iterator object.  Patch by Clement
  Rouault.

- bpo-23985: Fix a possible buffer overrun when deleting a slice from the
  front of a bytearray and then appending some other bytes data.

- bpo-24102: Fixed exception type checking in standard error handlers.

- bpo-15027: The UTF-32 encoder is now 3x to 7x faster.

- bpo-23290: Optimize set_merge() for cases where the target is empty.
  (Contributed by Serhiy Storchaka.)

- bpo-2292: PEP 448: Additional Unpacking Generalizations.

- bpo-24096: Make warnings.warn_explicit more robust against mutation of the
  warnings.filters list.

- bpo-23996: Avoid a crash when a delegated generator raises an unnormalized
  StopIteration exception.  Patch by Stefan Behnel.

- bpo-23910: Optimize property() getter calls.  Patch by Joe Jevnik.

- bpo-23911: Move path-based importlib bootstrap code to a separate frozen
  module.

- bpo-24192: Fix namespace package imports.

- bpo-24022: Fix tokenizer crash when processing undecodable source code.

- bpo-9951: Added a hex() method to bytes, bytearray, and memoryview.

- bpo-22906: PEP 479: Change StopIteration handling inside generators.

- bpo-24017: PEP 492: Coroutines with async and await syntax.

Library
-------

- bpo-14373: Added C implementation of functools.lru_cache().  Based on
  patches by Matt Joiner and Alexey Kachayev.

- bpo-24230: The tempfile module now accepts bytes for prefix, suffix and
  dir parameters and returns bytes in such situations (matching the os
  module APIs).

- bpo-22189: collections.UserString now supports __getnewargs__(),
  __rmod__(), casefold(), format_map(), isprintable(), and maketrans().
  Patch by Joe Jevnik.

- bpo-24244: Prevents termination when an invalid format string is
  encountered on Windows in strftime.

- bpo-23973: PEP 484: Add the typing module.

- bpo-23086: The collections.abc.Sequence() abstract base class added
  *start* and *stop* parameters to the index() mixin. Patch by Devin
  Jeanpierre.

- bpo-20035: Replaced the ``tkinter._fix`` module used for setting up the
  Tcl/Tk environment on Windows with a private function in the ``_tkinter``
  module that makes no permanent changes to the environment.

- bpo-24257: Fixed segmentation fault in sqlite3.Row constructor with faked
  cursor type.

- bpo-15836: assertRaises(), assertRaisesRegex(), assertWarns() and
  assertWarnsRegex() assertments now check the type of the first argument to
  prevent possible user error.  Based on patch by Daniel Wagner-Hall.

- bpo-9858: Add missing method stubs to _io.RawIOBase.  Patch by Laura
  Rupprecht.

- bpo-22955: attrgetter, itemgetter and methodcaller objects in the operator
  module now support pickling.  Added readable and evaluable repr for these
  objects. Based on patch by Josh Rosenberg.

- bpo-22107: tempfile.gettempdir() and tempfile.mkdtemp() now try again when
  a directory with the chosen name already exists on Windows as well as on
  Unix. tempfile.mkstemp() now fails early if parent directory is not valid
  (not exists or is a file) on Windows.

- bpo-23780: Improved error message in os.path.join() with single argument.

- bpo-6598: Increased time precision and random number range in
  email.utils.make_msgid() to strengthen the uniqueness of the message ID.

- bpo-24091: Fixed various crashes in corner cases in C implementation of
  ElementTree.

- bpo-21931: msilib.FCICreate() now raises TypeError in the case of a bad
  argument instead of a ValueError with a bogus FCI error number. Patch by
  Jeffrey Armstrong.

- bpo-13866: *quote_via* argument added to urllib.parse.urlencode.

- bpo-20098: New mangle_from policy option for email, default True for
  compat32, but False for all other policies.

- bpo-24211: The email library now supports RFC 6532: it can generate
  headers using utf-8 instead of encoded words.

- bpo-16314: Added support for the LZMA compression in distutils.

- bpo-21804: poplib now supports RFC 6856 (UTF8).

- bpo-18682: Optimized pprint functions for builtin scalar types.

- bpo-22027: smtplib now supports RFC 6531 (SMTPUTF8).

- bpo-23488: Random generator objects now consume 2x less memory on 64-bit.

- bpo-1322: platform.dist() and platform.linux_distribution() functions are
  now deprecated.  Initial patch by Vajrasky Kok.

- bpo-22486: Added the math.gcd() function.  The fractions.gcd() function
  now is deprecated.  Based on patch by Mark Dickinson.

- bpo-24064: Property() docstrings are now writeable. (Patch by Berker
  Peksag.)

- bpo-22681: Added support for the koi8_t encoding.

- bpo-22682: Added support for the kz1048 encoding.

- bpo-23796: peek and read1 methods of BufferedReader now raise ValueError
  if they called on a closed object. Patch by John Hergenroeder.

- bpo-21795: smtpd now supports the 8BITMIME extension whenever the new
  *decode_data* constructor argument is set to False.

- bpo-24155: optimize heapq.heapify() for better cache performance when
  heapifying large lists.

- bpo-21800: imaplib now supports RFC 5161 (enable), RFC 6855
  (utf8/internationalized email) and automatically encodes non-ASCII
  usernames and passwords to UTF8.

- bpo-20274: When calling a _sqlite.Connection, it now complains if passed
  any keyword arguments.  Previously it silently ignored them.

- bpo-20274: Remove ignored and erroneous "kwargs" parameters from three
  METH_VARARGS methods on _sqlite.Connection.

- bpo-24134: assertRaises(), assertRaisesRegex(), assertWarns() and
  assertWarnsRegex() checks now emits a deprecation warning when callable is
  None or keyword arguments except msg is passed in the context manager
  mode.

- bpo-24018: Add a collections.abc.Generator abstract base class.
  Contributed by Stefan Behnel.

- bpo-23880: Tkinter's getint() and getdouble() now support Tcl_Obj.
  Tkinter's getdouble() now supports any numbers (in particular int).

- bpo-22619: Added negative limit support in the traceback module. Based on
  patch by Dmitry Kazakov.

- bpo-24094: Fix possible crash in json.encode with poorly behaved dict
  subclasses.

- bpo-9246: On POSIX, os.getcwd() now supports paths longer than 1025 bytes.
  Patch written by William Orr.

- bpo-17445: add difflib.diff_bytes() to support comparison of byte strings
  (fixes a regression from Python 2).

- bpo-23917: Fall back to sequential compilation when ProcessPoolExecutor
  doesn't exist. Patch by Claudiu Popa.

- bpo-23008: Fixed resolving attributes with boolean value is False in
  pydoc.

- Fix asyncio issue 235: LifoQueue and PriorityQueue's put didn't increment
  unfinished tasks (this bug was introduced when JoinableQueue was merged
  with Queue).

- bpo-23908: os functions now reject paths with embedded null character on
  Windows instead of silently truncating them.

- bpo-23728: binascii.crc_hqx() could return an integer outside of the range
  0-0xffff for empty data.

- bpo-23887: urllib.error.HTTPError now has a proper repr() representation.
  Patch by Berker Peksag.

- asyncio: New event loop APIs: set_task_factory() and get_task_factory().

- asyncio: async() function is deprecated in favour of ensure_future().

- bpo-24178: asyncio.Lock, Condition, Semaphore, and BoundedSemaphore
  support new 'async with' syntax.  Contributed by Yury Selivanov.

- bpo-24179: Support 'async for' for asyncio.StreamReader. Contributed by
  Yury Selivanov.

- bpo-24184: Add AsyncIterator and AsyncIterable ABCs to collections.abc.
  Contributed by Yury Selivanov.

- bpo-22547: Implement informative __repr__ for inspect.BoundArguments.
  Contributed by Yury Selivanov.

- bpo-24190: Implement inspect.BoundArgument.apply_defaults() method.
  Contributed by Yury Selivanov.

- bpo-20691: Add 'follow_wrapped' argument to
  inspect.Signature.from_callable() and inspect.signature(). Contributed by
  Yury Selivanov.

- bpo-24248: Deprecate inspect.Signature.from_function() and
  inspect.Signature.from_builtin().

- bpo-23898: Fix inspect.classify_class_attrs() to support attributes with
  overloaded __eq__ and __bool__.  Patch by Mike Bayer.

- bpo-24298: Fix inspect.signature() to correctly unwrap wrappers around
  bound methods.

IDLE
----

- bpo-23184: remove unused names and imports in idlelib. Initial patch by Al
  Sweigart.

Tests
-----

- bpo-21520: test_zipfile no longer fails if the word 'bad' appears anywhere
  in the name of the current directory.

- bpo-9517: Move script_helper into the support package. Patch by Christie
  Wilson.

Documentation
-------------

- bpo-22155: Add File Handlers subsection with createfilehandler to tkinter
  doc.  Remove obsolete example from FAQ.  Patch by Martin Panter.

- bpo-24029: Document the name binding behavior for submodule imports.

- bpo-24077: Fix typo in man page for -I command option: -s, not -S

Tools/Demos
-----------

- bpo-24000: Improved Argument Clinic's mapping of converters to legacy
  "format units". Updated the documentation to match.

- bpo-24001: Argument Clinic converters now use accept={type} instead of
  types={'type'} to specify the types the converter accepts.

- bpo-23330: h2py now supports arbitrary filenames in #include.

- bpo-24031: make patchcheck now supports git checkouts, too.


What's New in Python 3.5.0 alpha 4?
===================================

*Release date: 2015-04-19*

Core and Builtins
-----------------

- bpo-22980: Under Linux, GNU/KFreeBSD and the Hurd, C extensions now
  include the architecture triplet in the extension name, to make it easy to
  test builds for different ABIs in the same working tree.  Under OS X, the
  extension name now includes :pep:`3149`-style information.

- bpo-22631: Added Linux-specific socket constant CAN_RAW_FD_FRAMES. Patch
  courtesy of Joe Jevnik.

- bpo-23731: Implement :pep:`488`: removal of .pyo files.

- bpo-23726: Don't enable GC for user subclasses of non-GC types that don't
  add any new fields.  Patch by Eugene Toder.

- bpo-23309: Avoid a deadlock at shutdown if a daemon thread is aborted
  while it is holding a lock to a buffered I/O object, and the main thread
  tries to use the same I/O object (typically stdout or stderr).  A fatal
  error is emitted instead.

- bpo-22977: Fixed formatting Windows error messages on Wine. Patch by
  Martin Panter.

- bpo-23466: %c, %o, %x, and %X in bytes formatting now raise TypeError on
  non-integer input.

- bpo-24044: Fix possible null pointer dereference in list.sort in out of
  memory conditions.

- bpo-21354: PyCFunction_New function is exposed by python DLL again.

Library
-------

- bpo-23840: tokenize.open() now closes the temporary binary file on error
  to fix a resource warning.

- bpo-16914: new debuglevel 2 in smtplib adds timestamps to debug output.

- bpo-7159: urllib.request now supports sending auth credentials
  automatically after the first 401.  This enhancement is a superset of the
  enhancement from issue #19494 and supersedes that change.

- bpo-23703: Fix a regression in urljoin() introduced in 901e4e52b20a. Patch
  by Demian Brecht.

- bpo-4254: Adds _curses.update_lines_cols().  Patch by Arnon Yaari

- bpo-19933: Provide default argument for ndigits in round. Patch by
  Vajrasky Kok.

- bpo-23193: Add a numeric_owner parameter to tarfile.TarFile.extract and
  tarfile.TarFile.extractall. Patch by Michael Vogt and Eric Smith.

- bpo-23342: Add a subprocess.run() function than returns a CalledProcess
  instance for a more consistent API than the existing call* functions.

- bpo-21217: inspect.getsourcelines() now tries to compute the start and end
  lines from the code object, fixing an issue when a lambda function is used
  as decorator argument. Patch by Thomas Ballinger and Allison Kaptur.

- bpo-24521: Fix possible integer overflows in the pickle module.

- bpo-22931: Allow '[' and ']' in cookie values.

- The keywords attribute of functools.partial is now always a dictionary.

- bpo-23811: Add missing newline to the PyCompileError error message. Patch
  by Alex Shkop.

- bpo-21116: Avoid blowing memory when allocating a multiprocessing shared
  array that's larger than 50% of the available RAM.  Patch by Médéric
  Boquien.

- bpo-22982: Improve BOM handling when seeking to multiple positions of a
  writable text file.

- bpo-23464: Removed deprecated asyncio JoinableQueue.

- bpo-23529: Limit the size of decompressed data when reading from GzipFile,
  BZ2File or LZMAFile.  This defeats denial of service attacks using
  compressed bombs (i.e. compressed payloads which decompress to a huge
  size).  Patch by Martin Panter and Nikolaus Rath.

- bpo-21859: Added Python implementation of io.FileIO.

- bpo-23865: close() methods in multiple modules now are idempotent and more
  robust at shutdown. If they need to release multiple resources, all are
  released even if errors occur.

- bpo-23400: Raise same exception on both Python 2 and 3 if sem_open is not
  available. Patch by Davin Potts.

- bpo-10838: The subprocess now module includes SubprocessError and
  TimeoutError in its list of exported names for the users wild enough to
  use ``from subprocess import *``.

- bpo-23411: Added DefragResult, ParseResult, SplitResult,
  DefragResultBytes, ParseResultBytes, and SplitResultBytes to
  urllib.parse.__all__. Patch by Martin Panter.

- bpo-23881: urllib.request.ftpwrapper constructor now closes the socket if
  the FTP connection failed to fix a ResourceWarning.

- bpo-23853: :meth:`socket.socket.sendall` does no more reset the socket
  timeout each time data is sent successfully. The socket timeout is now the
  maximum total duration to send all data.

- bpo-22721: An order of multiline pprint output of set or dict containing
  orderable and non-orderable elements no longer depends on iteration order
  of set or dict.

- bpo-15133: _tkinter.tkapp.getboolean() now supports Tcl_Obj and always
  returns bool. tkinter.BooleanVar now validates input values (accepted
  bool, int, str, and Tcl_Obj).  tkinter.BooleanVar.get() now always returns
  bool.

- bpo-10590: xml.sax.parseString() now supports string argument.

- bpo-23338: Fixed formatting ctypes error messages on Cygwin. Patch by
  Makoto Kato.

- bpo-15582: inspect.getdoc() now follows inheritance chains.

- bpo-2175: SAX parsers now support a character stream of InputSource
  object.

- bpo-16840: Tkinter now supports 64-bit integers added in Tcl 8.4 and
  arbitrary precision integers added in Tcl 8.5.

- bpo-23834: Fix socket.sendto(), use the C Py_ssize_t type to store the
  result of sendto() instead of the C int type.

- bpo-23618: :meth:`socket.socket.connect` now waits until the connection
  completes instead of raising :exc:`InterruptedError` if the connection is
  interrupted by signals, signal handlers don't raise an exception and the
  socket is blocking or has a timeout. :meth:`socket.socket.connect` still
  raise :exc:`InterruptedError` for non-blocking sockets.

- bpo-21526: Tkinter now supports new boolean type in Tcl 8.5.

- bpo-23836: Fix the faulthandler module to handle reentrant calls to its
  signal handlers.

- bpo-23838: linecache now clears the cache and returns an empty result on
  MemoryError.

- bpo-10395: Added os.path.commonpath(). Implemented in posixpath and
  ntpath. Based on patch by Rafik Draoui.

- bpo-23611: Serializing more "lookupable" objects (such as unbound methods
  or nested classes) now are supported with pickle protocols < 4.

- bpo-13583: sqlite3.Row now supports slice indexing.

- bpo-18473: Fixed 2to3 and 3to2 compatible pickle mappings.  Fixed
  ambiguous reverse mappings.  Added many new mappings.  Import mapping is
  no longer applied to modules already mapped with full name mapping.

- bpo-23485: select.select() is now retried automatically with the
  recomputed timeout when interrupted by a signal, except if the signal
  handler raises an exception. This change is part of the :pep:`475`.

- bpo-23752: When built from an existing file descriptor, io.FileIO() now
  only calls fstat() once. Before fstat() was called twice, which was not
  necessary.

- bpo-23704: collections.deque() objects now support __add__, __mul__, and
  __imul__().

- bpo-23171: csv.Writer.writerow() now supports arbitrary iterables.

- bpo-23745: The new email header parser now handles duplicate MIME
  parameter names without error, similar to how get_param behaves.

- bpo-22117: Fix os.utime(), it now rounds the timestamp towards minus
  infinity (-inf) instead of rounding towards zero.

- bpo-23310: Fix MagicMock's initializer to work with __methods__, just like
  configure_mock().  Patch by Kasia Jachim.

Build
-----

- bpo-23817: FreeBSD now uses "1.0" in the SOVERSION as other operating
  systems, instead of just "1".

- bpo-23501: Argument Clinic now generates code into separate files by
  default.

Tests
-----

- bpo-23799: Added test.support.start_threads() for running and cleaning up
  multiple threads.

- bpo-22390: test.regrtest now emits a warning if temporary files or
  directories are left after running a test.

Tools/Demos
-----------

- bpo-18128: pygettext now uses standard +NNNN format in the
  POT-Creation-Date header.

- bpo-23935: Argument Clinic's understanding of format units accepting
  bytes, bytearrays, and buffers is now consistent with both the
  documentation and the implementation.

- bpo-23944: Argument Clinic now wraps long impl prototypes at column 78.

- bpo-20586: Argument Clinic now ensures that functions without docstrings
  have signatures.

- bpo-23492: Argument Clinic now generates argument parsing code with
  PyArg_Parse instead of PyArg_ParseTuple if possible.

- bpo-23500: Argument Clinic is now smarter about generating the "#ifndef"
  (empty) definition of the methoddef macro: it's only generated once, even
  if Argument Clinic processes the same symbol multiple times, and it's
  emitted at the end of all processing rather than immediately after the
  first use.

C API
-----

- bpo-23998: PyImport_ReInitLock() now checks for lock allocation error


What's New in Python 3.5.0 alpha 3?
===================================

*Release date: 2015-03-28*

Core and Builtins
-----------------

- bpo-23573: Increased performance of string search operations (str.find,
  str.index, str.count, the in operator, str.split, str.partition) with
  arguments of different kinds (UCS1, UCS2, UCS4).

- bpo-23753: Python doesn't support anymore platforms without stat() or
  fstat(), these functions are always required.

- bpo-23681: The -b option now affects comparisons of bytes with int.

- bpo-23632: Memoryviews now allow tuple indexing (including for
  multi-dimensional memoryviews).

- bpo-23192: Fixed generator lambdas.  Patch by Bruno Cauet.

- bpo-23629: Fix the default __sizeof__ implementation for variable-sized
  objects.

Library
-------

- bpo-14260: The groupindex attribute of regular expression pattern object
  now is non-modifiable mapping.

- bpo-23792: Ignore KeyboardInterrupt when the pydoc pager is active. This
  mimics the behavior of the standard unix pagers, and prevents pipepager
  from shutting down while the pager itself is still running.

- bpo-23775: pprint() of OrderedDict now outputs the same representation as
  repr().

- bpo-23765: Removed IsBadStringPtr calls in ctypes

- bpo-22364: Improved some re error messages using regex for hints.

- bpo-23742: ntpath.expandvars() no longer loses unbalanced single quotes.

- bpo-21717: The zipfile.ZipFile.open function now supports 'x' (exclusive
  creation) mode.

- bpo-21802: The reader in BufferedRWPair now is closed even when closing
  writer failed in BufferedRWPair.close().

- bpo-23622: Unknown escapes in regular expressions that consist of ``'\'``
  and ASCII letter now raise a deprecation warning and will be forbidden in
  Python 3.6.

- bpo-23671: string.Template now allows specifying the "self" parameter as a
  keyword argument.  string.Formatter now allows specifying the "self" and
  the "format_string" parameters as keyword arguments.

- bpo-23502: The pprint module now supports mapping proxies.

- bpo-17530: pprint now wraps long bytes objects and bytearrays.

- bpo-22687: Fixed some corner cases in breaking words in tetxtwrap. Got rid
  of quadratic complexity in breaking long words.

- bpo-4727: The copy module now uses pickle protocol 4 (PEP 3154) and
  supports copying of instances of classes whose __new__ method takes
  keyword-only arguments.

- bpo-23491: Added a zipapp module to support creating executable zip file
  archives of Python code. Registered ".pyz" and ".pyzw" extensions on
  Windows for these archives (PEP 441).

- bpo-23657: Avoid explicit checks for str in zipapp, adding support for
  pathlib.Path objects as arguments.

- bpo-23688: Added support of arbitrary bytes-like objects and avoided
  unnecessary copying of memoryview in gzip.GzipFile.write(). Original patch
  by Wolfgang Maier.

- bpo-23252: Added support for writing ZIP files to unseekable streams.

- bpo-23647: Increase imaplib's MAXLINE to accommodate modern mailbox sizes.

- bpo-23539: If body is None, http.client.HTTPConnection.request now sets
  Content-Length to 0 for PUT, POST, and PATCH headers to avoid 411 errors
  from some web servers.

- bpo-22351: The nntplib.NNTP constructor no longer leaves the connection
  and socket open until the garbage collector cleans them up.  Patch by
  Martin Panter.

- bpo-23704: collections.deque() objects now support methods for index(),
  insert(), and copy().  This allows deques to be registered as a
  MutableSequence and it improves their substitutability for lists.

- bpo-23715: :func:`signal.sigwaitinfo` and :func:`signal.sigtimedwait` are
  now retried when interrupted by a signal not in the *sigset* parameter, if
  the signal handler does not raise an exception. signal.sigtimedwait()
  recomputes the timeout with a monotonic clock when it is retried.

- bpo-23001: Few functions in modules mmap, ossaudiodev, socket, ssl, and
  codecs, that accepted only read-only bytes-like object now accept writable
  bytes-like object too.

- bpo-23646: If time.sleep() is interrupted by a signal, the sleep is now
  retried with the recomputed delay, except if the signal handler raises an
  exception (PEP 475).

- bpo-23136: _strptime now uniformly handles all days in week 0, including
  Dec 30 of previous year.  Based on patch by Jim Carroll.

- bpo-23700: Iterator of NamedTemporaryFile now keeps a reference to
  NamedTemporaryFile instance.  Patch by Bohuslav Kabrda.

- bpo-22903: The fake test case created by unittest.loader when it fails
  importing a test module is now picklable.

- bpo-22181: On Linux, os.urandom() now uses the new getrandom() syscall if
  available, syscall introduced in the Linux kernel 3.17. It is more
  reliable and more secure, because it avoids the need of a file descriptor
  and waits until the kernel has enough entropy.

- bpo-2211: Updated the implementation of the http.cookies.Morsel class.
  Setting attributes key, value and coded_value directly now is deprecated.
  update() and setdefault() now transform and check keys.  Comparing for
  equality now takes into account attributes key, value and coded_value.
  copy() now returns a Morsel, not a dict.  repr() now contains all
  attributes. Optimized checking keys and quoting values.  Added new tests.
  Original patch by Demian Brecht.

- bpo-18983: Allow selection of output units in timeit. Patch by Julian
  Gindi.

- bpo-23631: Fix traceback.format_list when a traceback has been mutated.

- bpo-23568: Add rdivmod support to MagicMock() objects. Patch by Håkan
  Lövdahl.

- bpo-2052: Add charset parameter to HtmlDiff.make_file().

- bpo-23668: Support os.truncate and os.ftruncate on Windows.

- bpo-23138: Fixed parsing cookies with absent keys or values in cookiejar.
  Patch by Demian Brecht.

- bpo-23051: multiprocessing.Pool methods imap() and imap_unordered() now
  handle exceptions raised by an iterator.  Patch by Alon Diamant and Davin
  Potts.

- bpo-23581: Add matmul support to MagicMock. Patch by Håkan Lövdahl.

- bpo-23566: enable(), register(), dump_traceback() and
  dump_traceback_later() functions of faulthandler now accept file
  descriptors. Patch by Wei Wu.

- bpo-22928: Disabled HTTP header injections in http.client. Original patch
  by Demian Brecht.

- bpo-23615: Modules bz2, tarfile and tokenize now can be reloaded with
  imp.reload(). Patch by Thomas Kluyver.

- bpo-23605: os.walk() now calls os.scandir() instead of os.listdir(). The
  usage of os.scandir() reduces the number of calls to os.stat(). Initial
  patch written by Ben Hoyt.

Build
-----

- bpo-23585: make patchcheck will ensure the interpreter is built.

Tests
-----

- bpo-23583: Added tests for standard IO streams in IDLE.

- bpo-22289: Prevent test_urllib2net failures due to ftp connection timeout.

Tools/Demos
-----------

- bpo-22826: The result of open() in Tools/freeze/bkfile.py is now better
  compatible with regular files (in particular it now supports the context
  management protocol).


What's New in Python 3.5.0 alpha 2?
===================================

*Release date: 2015-03-09*

Core and Builtins
-----------------

- bpo-23571: PyObject_Call() and PyCFunction_Call() now raise a SystemError
  if a function returns a result and raises an exception. The SystemError is
  chained to the previous exception.

Library
-------

- bpo-22524: New os.scandir() function, part of the :pep:`471`:
  "os.scandir() function -- a better and faster directory iterator". Patch
  written by Ben Hoyt.

- bpo-23103: Reduced the memory consumption of IPv4Address and IPv6Address.

- bpo-21793: BaseHTTPRequestHandler again logs response code as numeric, not
  as stringified enum.  Patch by Demian Brecht.

- bpo-23476: In the ssl module, enable OpenSSL's X509_V_FLAG_TRUSTED_FIRST
  flag on certificate stores when it is available.

- bpo-23576: Avoid stalling in SSL reads when EOF has been reached in the
  SSL layer but the underlying connection hasn't been closed.

- bpo-23504: Added an __all__ to the types module.

- bpo-23563: Optimized utility functions in urllib.parse.

- bpo-7830: Flatten nested functools.partial.

- bpo-20204: Added the __module__ attribute to _tkinter classes.

- bpo-19980: Improved help() for non-recognized strings.  help('') now shows
  the help on str.  help('help') now shows the help on help(). Original
  patch by Mark Lawrence.

- bpo-23521: Corrected pure python implementation of timedelta division.
  Eliminated OverflowError from ``timedelta * float`` for some floats;
  Corrected rounding in timedelta true division.

- bpo-21619: Popen objects no longer leave a zombie after exit in the with
  statement if the pipe was broken.  Patch by Martin Panter.

- bpo-22936: Make it possible to show local variables in tracebacks for both
  the traceback module and unittest.

- bpo-15955: Add an option to limit the output size in bz2.decompress().
  Patch by Nikolaus Rath.

- bpo-6639: Module-level turtle functions no longer raise TclError after
  closing the window.

- bpo-814253: Group references and conditional group references now work in
  lookbehind assertions in regular expressions. (See also: bpo-9179)

- bpo-23215: Multibyte codecs with custom error handlers that ignores errors
  consumed too much memory and raised SystemError or MemoryError. Original
  patch by Aleksi Torhamo.

- bpo-5700: io.FileIO() called flush() after closing the file. flush() was
  not called in close() if closefd=False.

- bpo-23374: Fixed pydoc failure with non-ASCII files when stdout encoding
  differs from file system encoding (e.g. on Mac OS).

- bpo-23481: Remove RC4 from the SSL module's default cipher list.

- bpo-21548: Fix pydoc.synopsis() and pydoc.apropos() on modules with empty
  docstrings.

- bpo-22885: Fixed arbitrary code execution vulnerability in the dbm.dumb
  module. Original patch by Claudiu Popa.

- bpo-23239: ssl.match_hostname() now supports matching of IP addresses.

- bpo-23146: Fix mishandling of absolute Windows paths with forward slashes
  in pathlib.

- bpo-23096: Pickle representation of floats with protocol 0 now is the same
  for both Python and C implementations.

- bpo-19105: pprint now more efficiently uses free space at the right.

- bpo-14910: Add allow_abbrev parameter to argparse.ArgumentParser. Patch by
  Jonathan Paugh, Steven Bethard, paul j3 and Daniel Eriksson.

- bpo-21717: tarfile.open() now supports 'x' (exclusive creation) mode.

- bpo-23344: marshal.dumps() is now 20-25% faster on average.

- bpo-20416: marshal.dumps() with protocols 3 and 4 is now 40-50% faster on
  average.

- bpo-23421: Fixed compression in tarfile CLI.  Patch by wdv4758h.

- bpo-23367: Fix possible overflows in the unicodedata module.

- bpo-23361: Fix possible overflow in Windows subprocess creation code.

- logging.handlers.QueueListener now takes a respect_handler_level keyword
  argument which, if set to True, will pass messages to handlers taking
  handler levels into account.

- bpo-19705: turtledemo now has a visual sorting algorithm demo.  Original
  patch from Jason Yeo.

- bpo-23801: Fix issue where cgi.FieldStorage did not always ignore the
  entire preamble to a multipart body.

Build
-----

- bpo-23445: pydebug builds now use "gcc -Og" where possible, to make the
  resulting executable faster.

- bpo-23686: Update OS X 10.5 installer build to use OpenSSL 1.0.2a.

C API
-----

- bpo-20204: Deprecation warning is now raised for builtin types without the
  __module__ attribute.

Windows
-------

- bpo-23465: Implement :pep:`486` - Make the Python Launcher aware of
  virtual environments. Patch by Paul Moore.

- bpo-23437: Make user scripts directory versioned on Windows. Patch by Paul
  Moore.


What's New in Python 3.5.0 alpha 1?
===================================

*Release date: 2015-02-08*

Core and Builtins
-----------------

- bpo-23285: PEP 475 - EINTR handling.

- bpo-22735: Fix many edge cases (including crashes) involving custom mro()
  implementations.

- bpo-22896: Avoid using PyObject_AsCharBuffer(), PyObject_AsReadBuffer()
  and PyObject_AsWriteBuffer().

- bpo-21295: Revert some changes (issue #16795) to AST line numbers and
  column offsets that constituted a regression.

- bpo-22986: Allow changing an object's __class__ between a dynamic type and
  static type in some cases.

- bpo-15859: PyUnicode_EncodeFSDefault(), PyUnicode_EncodeMBCS() and
  PyUnicode_EncodeCodePage() now raise an exception if the object is not a
  Unicode object. For PyUnicode_EncodeFSDefault(), it was already the case
  on platforms other than Windows. Patch written by Campbell Barton.

- bpo-21408: The default __ne__() now returns NotImplemented if __eq__()
  returned NotImplemented.  Original patch by Martin Panter.

- bpo-23321: Fixed a crash in str.decode() when error handler returned
  replacement string longer than malformed input data.

- bpo-22286: The "backslashreplace" error handlers now works with decoding
  and translating.

- bpo-23253: Delay-load ShellExecute[AW] in os.startfile for reduced startup
  overhead on Windows.

- bpo-22038: pyatomic.h now uses stdatomic.h or GCC built-in functions for
  atomic memory access if available. Patch written by Vitor de Lima and
  Gustavo Temple.

- bpo-20284: %-interpolation (aka printf) formatting added for bytes and
  bytearray.

- bpo-23048: Fix jumping out of an infinite while loop in the pdb.

- bpo-20335: bytes constructor now raises TypeError when encoding or errors
  is specified with non-string argument.  Based on patch by Renaud Blanch.

- bpo-22834: If the current working directory ends up being set to a
  non-existent directory then import will no longer raise FileNotFoundError.

- bpo-22869: Move the interpreter startup & shutdown code to a new dedicated
  pylifecycle.c module

- bpo-22847: Improve method cache efficiency.

- bpo-22335: Fix crash when trying to enlarge a bytearray to 0x7fffffff
  bytes on a 32-bit platform.

- bpo-22653: Fix an assertion failure in debug mode when doing a reentrant
  dict insertion in debug mode.

- bpo-22643: Fix integer overflow in Unicode case operations (upper, lower,
  title, swapcase, casefold).

- bpo-17636: Circular imports involving relative imports are now supported.

- bpo-22604: Fix assertion error in debug mode when dividing a complex
  number by (nan+0j).

- bpo-21052: Do not raise ImportWarning when sys.path_hooks or sys.meta_path
  are set to None.

- bpo-16518: Use 'bytes-like object required' in error messages that
  previously used the far more cryptic "'x' does not support the buffer
  protocol.

- bpo-22470: Fixed integer overflow issues in "backslashreplace",
  "xmlcharrefreplace", and "surrogatepass" error handlers.

- bpo-22540: speed up `PyObject_IsInstance` and `PyObject_IsSubclass` in the
  common case that the second argument has metaclass `type`.

- bpo-18711: Add a new `PyErr_FormatV` function, similar to `PyErr_Format`
  but accepting a `va_list` argument.

- bpo-22520: Fix overflow checking when generating the repr of a unicode
  object.

- bpo-22519: Fix overflow checking in PyBytes_Repr.

- bpo-22518: Fix integer overflow issues in latin-1 encoding.

- bpo-16324: _charset parameter of MIMEText now also accepts
  email.charset.Charset instances. Initial patch by Claude Paroz.

- bpo-1764286: Fix inspect.getsource() to support decorated functions. Patch
  by Claudiu Popa.

- bpo-18554: os.__all__ includes posix functions.

- bpo-21391: Use os.path.abspath in the shutil module.

- bpo-11471: avoid generating a JUMP_FORWARD instruction at the end of an
  if-block if there is no else-clause.  Original patch by Eugene Toder.

- bpo-22215: Now ValueError is raised instead of TypeError when str or bytes
  argument contains not permitted null character or byte.

- bpo-22258: Fix the internal function set_inheritable() on Illumos. This
  platform exposes the function ``ioctl(FIOCLEX)``, but calling it fails
  with errno is ENOTTY: "Inappropriate ioctl for device". set_inheritable()
  now falls back to the slower ``fcntl()`` (``F_GETFD`` and then
  ``F_SETFD``).

- bpo-21389: Displaying the __qualname__ of the underlying function in the
  repr of a bound method.

- bpo-22206: Using pthread, PyThread_create_key() now sets errno to ENOMEM
  and returns -1 (error) on integer overflow.

- bpo-20184: Argument Clinic based signature introspection added for 30 of
  the builtin functions.

- bpo-22116: C functions and methods (of the 'builtin_function_or_method'
  type) can now be weakref'ed.  Patch by Wei Wu.

- bpo-22077: Improve index error messages for bytearrays, bytes, lists, and
  tuples by adding 'or slices'. Added ', not <typename>' for bytearrays.
  Original patch by Claudiu Popa.

- bpo-20179: Apply Argument Clinic to bytes and bytearray. Patch by Tal
  Einat.

- bpo-22082: Clear interned strings in slotdefs.

- Upgrade Unicode database to Unicode 7.0.0.

- bpo-21897: Fix a crash with the f_locals attribute with closure variables
  when frame.clear() has been called.

- bpo-21205: Add a new ``__qualname__`` attribute to generator, the
  qualified name, and use it in the representation of a generator
  (``repr(gen)``). The default name of the generator (``__name__``
  attribute) is now get from the function instead of the code. Use
  ``gen.gi_code.co_name`` to get the name of the code.

- bpo-21669: With the aid of heuristics in SyntaxError.__init__, the parser
  now attempts to generate more meaningful (or at least more search engine
  friendly) error messages when "exec" and "print" are used as statements.

- bpo-21642: In the conditional if-else expression, allow an integer written
  with no space between itself and the ``else`` keyword (e.g. ``True if
  42else False``) to be valid syntax.

- bpo-21523: Fix over-pessimistic computation of the stack effect of some
  opcodes in the compiler.  This also fixes a quadratic compilation time
  issue noticeable when compiling code with a large number of "and" and "or"
  operators.

- bpo-21418: Fix a crash in the builtin function super() when called without
  argument and without current frame (ex: embedded Python).

- bpo-21425: Fix flushing of standard streams in the interactive
  interpreter.

- bpo-21435: In rare cases, when running finalizers on objects in cyclic
  trash a bad pointer dereference could occur due to a subtle flaw in
  internal iteration logic.

- bpo-21377: PyBytes_Concat() now tries to concatenate in-place when the
  first argument has a reference count of 1.  Patch by Nikolaus Rath.

- bpo-20355: -W command line options now have higher priority than the
  PYTHONWARNINGS environment variable.  Patch by Arfrever.

- bpo-21274: Define PATH_MAX for GNU/Hurd in Python/pythonrun.c.

- bpo-20904: Support setting FPU precision on m68k.

- bpo-21209: Fix sending tuples to custom generator objects with the yield
  from syntax.

- bpo-21193: pow(a, b, c) now raises ValueError rather than TypeError when b
  is negative. Patch by Josh Rosenberg.

- bpo-21176: PEP 465: Add the '@' operator for matrix multiplication.

- bpo-21134: Fix segfault when str is called on an uninitialized
  UnicodeEncodeError, UnicodeDecodeError, or UnicodeTranslateError object.

- bpo-19537: Fix PyUnicode_DATA() alignment under m68k.  Patch by Andreas
  Schwab.

- bpo-20929: Add a type cast to avoid shifting a negative number.

- bpo-20731: Properly position in source code files even if they are opened
  in text mode. Patch by Serhiy Storchaka.

- bpo-20637: Key-sharing now also works for instance dictionaries of
  subclasses.  Patch by Peter Ingebretson.

- bpo-8297: Attributes missing from modules now include the module name in
  the error text.  Original patch by ysj.ray.

- bpo-19995: %c, %o, %x, and %X now raise TypeError on non-integer input.

- bpo-19655: The ASDL parser - used by the build process to generate code
  for managing the Python AST in C - was rewritten. The new parser is self
  contained and does not require to carry long the spark.py parser-generator
  library; spark.py was removed from the source base.

- bpo-12546: Allow ``\x00`` to be used as a fill character when using str,
  int, float, and complex __format__ methods.

- bpo-20480: Add ipaddress.reverse_pointer. Patch by Leon Weber.

- bpo-13598: Modify string.Formatter to support auto-numbering of
  replacement fields. It now matches the behavior of str.format() in this
  regard. Patches by Phil Elson and Ramchandra Apte.

- bpo-8931: Make alternate formatting ('#') for type 'c' raise an exception.
  In versions prior to 3.5, '#' with 'c' had no effect. Now specifying it is
  an error. Patch by Torsten Landschoff.

- bpo-23165: Perform overflow checks before allocating memory in the
  _Py_char2wchar function.

Library
-------

- bpo-23399: pyvenv creates relative symlinks where possible.

- bpo-20289: cgi.FieldStorage() now supports the context management
  protocol.

- bpo-13128: Print response headers for CONNECT requests when debuglevel >
  0. Patch by Demian Brecht.

- bpo-15381: Optimized io.BytesIO to make less allocations and copyings.

- bpo-22818: Splitting on a pattern that could match an empty string now
  raises a warning.  Patterns that can only match empty strings are now
  rejected.

- bpo-23099: Closing io.BytesIO with exported buffer is rejected now to
  prevent corrupting exported buffer.

- bpo-23326: Removed __ne__ implementations.  Since fixing default __ne__
  implementation in issue #21408 they are redundant.

- bpo-23363: Fix possible overflow in itertools.permutations.

- bpo-23364: Fix possible overflow in itertools.product.

- bpo-23366: Fixed possible integer overflow in itertools.combinations.

- bpo-23369: Fixed possible integer overflow in
  _json.encode_basestring_ascii.

- bpo-23353: Fix the exception handling of generators in
  PyEval_EvalFrameEx(). At entry, save or swap the exception state even if
  PyEval_EvalFrameEx() is called with throwflag=0. At exit, the exception
  state is now always restored or swapped, not only if why is WHY_YIELD or
  WHY_RETURN. Patch co-written with Antoine Pitrou.

- bpo-14099: Restored support of writing ZIP files to tellable but
  non-seekable streams.

- bpo-14099: Writing to ZipFile and reading multiple ZipExtFiles is
  threadsafe now.

- bpo-19361: JSON decoder now raises JSONDecodeError instead of ValueError.

- bpo-18518: timeit now rejects statements which can't be compiled outside a
  function or a loop (e.g. "return" or "break").

- bpo-23094: Fixed readline with frames in Python implementation of pickle.

- bpo-23268: Fixed bugs in the comparison of ipaddress classes.

- bpo-21408: Removed incorrect implementations of __ne__() which didn't
  returned NotImplemented if __eq__() returned NotImplemented.  The default
  __ne__() now works correctly.

- bpo-19996: :class:`email.feedparser.FeedParser` now handles (malformed)
  headers with no key rather than assuming the body has started.

- bpo-20188: Support Application-Layer Protocol Negotiation (ALPN) in the
  ssl module.

- bpo-23133: Pickling of ipaddress objects now produces more compact and
  portable representation.

- bpo-23248: Update ssl error codes from latest OpenSSL git master.

- bpo-23266: Much faster implementation of ipaddress.collapse_addresses()
  when there are many non-consecutive addresses.

- bpo-23098: 64-bit dev_t is now supported in the os module.

- bpo-21817: When an exception is raised in a task submitted to a
  ProcessPoolExecutor, the remote traceback is now displayed in the parent
  process.  Patch by Claudiu Popa.

- bpo-15955: Add an option to limit output size when decompressing LZMA
  data.  Patch by Nikolaus Rath and Martin Panter.

- bpo-23250: In the http.cookies module, capitalize "HttpOnly" and "Secure"
  as they are written in the standard.

- bpo-23063: In the distutils' check command, fix parsing of reST with code
  or code-block directives.

- bpo-23209: selectors.BaseSelector.get_key() now raises a RuntimeError if
  the selector is closed. And selectors.BaseSelector.close() now clears its
  internal reference to the selector mapping to break a reference cycle.
  Initial patch written by Martin Richard. (See also: bpo-23225)

- bpo-17911: Provide a way to seed the linecache for a PEP-302 module
  without actually loading the code.

- bpo-17911: Provide a new object API for traceback, including the ability
  to not lookup lines at all until the traceback is actually rendered,
  without any trace of the original objects being kept alive.

- bpo-19777: Provide a home() classmethod on Path objects.  Contributed by
  Victor Salgado and Mayank Tripathi.

- bpo-23206: Make ``json.dumps(..., ensure_ascii=False)`` as fast as the
  default case of ``ensure_ascii=True``.  Patch by Naoki Inada.

- bpo-23185: Add math.inf and math.nan constants.

- bpo-23186: Add ssl.SSLObject.shared_ciphers() and
  ssl.SSLSocket.shared_ciphers() to fetch the client's list ciphers sent at
  handshake.

- bpo-23143: Remove compatibility with OpenSSLs older than 0.9.8.

- bpo-23132: Improve performance and introspection support of comparison
  methods created by functool.total_ordering.

- bpo-19776: Add an expanduser() method on Path objects.

- bpo-23112: Fix SimpleHTTPServer to correctly carry the query string and
  fragment when it redirects to add a trailing slash.

- bpo-21793: Added http.HTTPStatus enums (i.e. HTTPStatus.OK,
  HTTPStatus.NOT_FOUND). Patch by Demian Brecht.

- bpo-23093: In the io, module allow more operations to work on detached
  streams.

- bpo-23111: In the ftplib, make ssl.PROTOCOL_SSLv23 the default protocol
  version.

- bpo-22585: On OpenBSD 5.6 and newer, os.urandom() now calls getentropy(),
  instead of reading /dev/urandom, to get pseudo-random bytes.

- bpo-19104: pprint now produces evaluable output for wrapped strings.

- bpo-23071: Added missing names to codecs.__all__.  Patch by Martin Panter.

- bpo-22783: Pickling now uses the NEWOBJ opcode instead of the NEWOBJ_EX
  opcode if possible.

- bpo-15513: Added a __sizeof__ implementation for pickle classes.

- bpo-19858: pickletools.optimize() now aware of the MEMOIZE opcode, can
  produce more compact result and no longer produces invalid output if input
  data contains MEMOIZE opcodes together with PUT or BINPUT opcodes.

- bpo-22095: Fixed HTTPConnection.set_tunnel with default port.  The port
  value in the host header was set to "None".  Patch by Demian Brecht.

- bpo-23016: A warning no longer produces an AttributeError when the program
  is run with pythonw.exe.

- bpo-21775: shutil.copytree(): fix crash when copying to VFAT. An exception
  handler assumed that OSError objects always have a 'winerror' attribute.
  That is not the case, so the exception handler itself raised
  AttributeError when run on Linux (and, presumably, any other non-Windows
  OS). Patch by Greg Ward.

- bpo-1218234: Fix inspect.getsource() to load updated source of reloaded
  module. Initial patch by Berker Peksag.

- bpo-21740: Support wrapped callables in doctest. Patch by Claudiu Popa.

- bpo-23009: Make sure selectors.EpollSelector.select() works when no FD is
  registered.

- bpo-22959: In the constructor of http.client.HTTPSConnection, prefer the
  context's check_hostname attribute over the *check_hostname* parameter.

- bpo-22696: Add function :func:`sys.is_finalizing` to know about
  interpreter shutdown.

- bpo-16043: Add a default limit for the amount of data
  xmlrpclib.gzip_decode will return. This resolves CVE-2013-1753.

- bpo-14099: ZipFile.open() no longer reopen the underlying file.  Objects
  returned by ZipFile.open() can now operate independently of the ZipFile
  even if the ZipFile was created by passing in a file-like object as the
  first argument to the constructor.

- bpo-22966: Fix __pycache__ pyc file name clobber when pyc_compile is asked
  to compile a source file containing multiple dots in the source file name.

- bpo-21971: Update turtledemo doc and add module to the index.

- bpo-21032: Fixed socket leak if HTTPConnection.getresponse() fails.
  Original patch by Martin Panter.

- bpo-22407: Deprecated the use of re.LOCALE flag with str patterns or
  re.ASCII. It was newer worked.

- bpo-22902: The "ip" command is now used on Linux to determine MAC address
  in uuid.getnode().  Pach by Bruno Cauet.

- bpo-22960: Add a context argument to xmlrpclib.ServerProxy constructor.

- bpo-22389: Add contextlib.redirect_stderr().

- bpo-21356: Make ssl.RAND_egd() optional to support LibreSSL. The
  availability of the function is checked during the compilation. Patch
  written by Bernard Spil.

- bpo-22915: SAX parser now supports files opened with file descriptor or
  bytes path.

- bpo-22609: Constructors and update methods of mapping classes in the
  collections module now accept the self keyword argument.

- bpo-22940: Add readline.append_history_file.

- bpo-19676: Added the "namereplace" error handler.

- bpo-22788: Add *context* parameter to logging.handlers.HTTPHandler.

- bpo-22921: Allow SSLContext to take the *hostname* parameter even if
  OpenSSL doesn't support SNI.

- bpo-22894: TestCase.subTest() would cause the test suite to be stopped
  when in failfast mode, even in the absence of failures.

- bpo-22796: HTTP cookie parsing is now stricter, in order to protect
  against potential injection attacks.

- bpo-22370: Windows detection in pathlib is now more robust.

- bpo-22841: Reject coroutines in asyncio add_signal_handler(). Patch by
  Ludovic.Gasc.

- bpo-19494: Added urllib.request.HTTPBasicPriorAuthHandler. Patch by Matej
  Cepl.

- bpo-22578: Added attributes to the re.error class.

- bpo-22849: Fix possible double free in the io.TextIOWrapper constructor.

- bpo-12728: Different Unicode characters having the same uppercase but
  different lowercase are now matched in case-insensitive regular
  expressions.

- bpo-22821: Fixed fcntl() with integer argument on 64-bit big-endian
  platforms.

- bpo-21650: Add an `--sort-keys` option to json.tool CLI.

- bpo-22824: Updated reprlib output format for sets to use set literals.
  Patch contributed by Berker Peksag.

- bpo-22824: Updated reprlib output format for arrays to display empty
  arrays without an unnecessary empty list.  Suggested by Serhiy Storchaka.

- bpo-22406: Fixed the uu_codec codec incorrectly ported to 3.x. Based on
  patch by Martin Panter.

- bpo-17293: uuid.getnode() now determines MAC address on AIX using netstat.
  Based on patch by Aivars Kalvāns.

- bpo-22769: Fixed ttk.Treeview.tag_has() when called without arguments.

- bpo-22417: Verify certificates by default in httplib (PEP 476).

- bpo-22775: Fixed unpickling of http.cookies.SimpleCookie with protocol 2
  and above. Patch by Tim Graham.

- bpo-22776: Brought excluded code into the scope of a try block in
  SysLogHandler.emit().

- bpo-22665: Add missing get_terminal_size and SameFileError to
  shutil.__all__.

- bpo-6623: Remove deprecated Netrc class in the ftplib module. Patch by
  Matt Chaput.

- bpo-17381: Fixed handling of case-insensitive ranges in regular
  expressions.

- bpo-22410: Module level functions in the re module now cache compiled
  locale-dependent regular expressions taking into account the locale.

- bpo-22759: Query methods on pathlib.Path() (exists(), is_dir(), etc.) now
  return False when the underlying stat call raises NotADirectoryError.

- bpo-8876: distutils now falls back to copying files when hard linking
  doesn't work. This allows use with special filesystems such as VirtualBox
  shared folders.

- bpo-22217: Implemented reprs of classes in the zipfile module.

- bpo-22457: Honour load_tests in the start_dir of discovery.

- bpo-18216: gettext now raises an error when a .mo file has an unsupported
  major version number.  Patch by Aaron Hill.

- bpo-13918: Provide a locale.delocalize() function which can remove
  locale-specific number formatting from a string representing a number,
  without then converting it to a specific type.  Patch by Cédric Krier.

- bpo-22676: Make the pickling of global objects which don't have a
  __module__ attribute less slow.

- bpo-18853: Fixed ResourceWarning in shlex.__nain__.

- bpo-9351: Defaults set with set_defaults on an argparse subparser are no
  longer ignored when also set on the parent parser.

- bpo-7559: unittest test loading ImportErrors are reported as import errors
  with their import exception rather than as attribute errors after the
  import has already failed.

- bpo-19746: Make it possible to examine the errors from unittest discovery
  without executing the test suite. The new `errors` attribute on TestLoader
  exposes these non-fatal errors encountered during discovery.

- bpo-21991: Make email.headerregistry's header 'params' attributes be
  read-only (MappingProxyType).  Previously the dictionary was modifiable
  but a new one was created on each access of the attribute.

- bpo-22638: SSLv3 is now disabled throughout the standard library. It can
  still be enabled by instantiating a SSLContext manually.

- bpo-22641: In asyncio, the default SSL context for client connections is
  now created using ssl.create_default_context(), for stronger security.

- bpo-17401: Include closefd in io.FileIO repr.

- bpo-21338: Add silent mode for compileall. quiet parameters of
  compile_{dir, file, path} functions now have a multilevel value. Also, -q
  option of the CLI now have a multilevel value. Patch by Thomas Kluyver.

- bpo-20152: Convert the array and cmath modules to Argument Clinic.

- bpo-18643: Add socket.socketpair() on Windows.

- bpo-22435: Fix a file descriptor leak when socketserver bind fails.

- bpo-13096: Fixed segfault in CTypes POINTER handling of large values.

- bpo-11694: Raise ConversionError in xdrlib as documented.  Patch by Filip
  Gruszczyński and Claudiu Popa.

- bpo-19380: Optimized parsing of regular expressions.

- bpo-1519638: Now unmatched groups are replaced with empty strings in
  re.sub() and re.subn().

- bpo-18615: sndhdr.what/whathdr now return a namedtuple.

- bpo-22462: Fix pyexpat's creation of a dummy frame to make it appear in
  exception tracebacks.

- bpo-21965: Add support for in-memory SSL to the ssl module.  Patch by
  Geert Jansen.

- bpo-21173: Fix len() on a WeakKeyDictionary when .clear() was called with
  an iterator alive.

- bpo-11866: Eliminated race condition in the computation of names for new
  threads.

- bpo-21905: Avoid RuntimeError in pickle.whichmodule() when sys.modules is
  mutated while iterating.  Patch by Olivier Grisel.

- bpo-11271: concurrent.futures.Executor.map() now takes a *chunksize*
  argument to allow batching of tasks in child processes and improve
  performance of ProcessPoolExecutor.  Patch by Dan O'Reilly.

- bpo-21883: os.path.join() and os.path.relpath() now raise a TypeError with
  more helpful error message for unsupported or mismatched types of
  arguments.

- bpo-22219: The zipfile module CLI now adds entries for directories
  (including empty directories) in ZIP file.

- bpo-22449: In the ssl.SSLContext.load_default_certs, consult the
  environmental variables SSL_CERT_DIR and SSL_CERT_FILE on Windows.

- bpo-22508: The email.__version__ variable has been removed; the email code
  is no longer shipped separately from the stdlib, and __version__ hasn't
  been updated in several releases.

- bpo-20076: Added non derived UTF-8 aliases to locale aliases table.

- bpo-20079: Added locales supported in glibc 2.18 to locale alias table.

- bpo-20218: Added convenience methods read_text/write_text and read_bytes/
  write_bytes to pathlib.Path objects.

- bpo-22396: On 32-bit AIX platform, don't expose os.posix_fadvise() nor
  os.posix_fallocate() because their prototypes in system headers are wrong.

- bpo-22517: When an io.BufferedRWPair object is deallocated, clear its
  weakrefs.

- bpo-22437: Number of capturing groups in regular expression is no longer
  limited by 100.

- bpo-17442: InteractiveInterpreter now displays the full chained traceback
  in its showtraceback method, to match the built in interactive
  interpreter.

- bpo-23392: Added tests for marshal C API that works with FILE*.

- bpo-10510: distutils register and upload methods now use HTML standards
  compliant CRLF line endings.

- bpo-9850: Fixed macpath.join() for empty first component.  Patch by Oleg
  Oshmyan.

- bpo-5309: distutils' build and build_ext commands now accept a ``-j``
  option to enable parallel building of extension modules.

- bpo-22448: Improve canceled timer handles cleanup to prevent unbound
  memory usage. Patch by Joshua Moore-Oliva.

- bpo-22427: TemporaryDirectory no longer attempts to clean up twice when
  used in the with statement in generator.

- bpo-22362: Forbidden ambiguous octal escapes out of range 0-0o377 in
  regular expressions.

- bpo-20912: Now directories added to ZIP file have correct Unix and MS-DOS
  directory attributes.

- bpo-21866: ZipFile.close() no longer writes ZIP64 central directory
  records if allowZip64 is false.

- bpo-22278: Fix urljoin problem with relative urls, a regression observed
  after changes to issue22118 were submitted.

- bpo-22415: Fixed debugging output of the GROUPREF_EXISTS opcode in the re
  module. Removed trailing spaces in debugging output.

- bpo-22423: Unhandled exception in thread no longer causes unhandled
  AttributeError when sys.stderr is None.

- bpo-21332: Ensure that ``bufsize=1`` in subprocess.Popen() selects line
  buffering, rather than block buffering.  Patch by Akira Li.

- bpo-21091: Fix API bug: email.message.EmailMessage.is_attachment is now a
  method.

- bpo-21079: Fix email.message.EmailMessage.is_attachment to return the
  correct result when the header has parameters as well as a value.

- bpo-22247: Add NNTPError to nntplib.__all__.

- bpo-22366: urllib.request.urlopen will accept a context object
  (SSLContext) as an argument which will then be used for HTTPS connection.
  Patch by Alex Gaynor.

- bpo-4180: The warnings registries are now reset when the filters are
  modified.

- bpo-22419: Limit the length of incoming HTTP request in wsgiref server to
  65536 bytes and send a 414 error code for higher lengths. Patch
  contributed by Devin Cook.

- Lax cookie parsing in http.cookies could be a security issue when combined
  with non-standard cookie handling in some web browsers.  Reported by
  Sergey Bobrov.

- bpo-20537: logging methods now accept an exception instance as well as a
  Boolean value or exception tuple. Thanks to Yury Selivanov for the patch.

- bpo-22384: An exception in Tkinter callback no longer crashes the program
  when it is run with pythonw.exe.

- bpo-22168: Prevent turtle AttributeError with non-default Canvas on OS X.

- bpo-21147: sqlite3 now raises an exception if the request contains a null
  character instead of truncating it.  Based on patch by Victor Stinner.

- bpo-13968: The glob module now supports recursive search in subdirectories
  using the ``**`` pattern.

- bpo-21951: Fixed a crash in Tkinter on AIX when called Tcl command with
  empty string or tuple argument.

- bpo-21951: Tkinter now most likely raises MemoryError instead of crash if
  the memory allocation fails.

- bpo-22338: Fix a crash in the json module on memory allocation failure.

- bpo-12410: imaplib.IMAP4 now supports the context management protocol.
  Original patch by Tarek Ziadé.

- bpo-21270: We now override tuple methods in mock.call objects so that they
  can be used as normal call attributes.

- bpo-16662: load_tests() is now unconditionally run when it is present in a
  package's __init__.py.  TestLoader.loadTestsFromModule() still accepts
  use_load_tests, but it is deprecated and ignored.  A new keyword-only
  attribute `pattern` is added and documented.  Patch given by Robert
  Collins, tweaked by Barry Warsaw.

- bpo-22226: First letter no longer is stripped from the "status" key in the
  result of Treeview.heading().

- bpo-19524: Fixed resource leak in the HTTP connection when an invalid
  response is received.  Patch by Martin Panter.

- bpo-20421: Add a .version() method to SSL sockets exposing the actual
  protocol version in use.

- bpo-19546: configparser exceptions no longer expose implementation
  details. Chained KeyErrors are removed, which leads to cleaner tracebacks.
  Patch by Claudiu Popa.

- bpo-22051: turtledemo no longer reloads examples to re-run them.
  Initialization of variables and gui setup should be done in main(), which
  is called each time a demo is run, but not on import.

- bpo-21933: Turtledemo users can change the code font size with a menu
  selection or control(command) '-' or '+' or control-mousewheel. Original
  patch by Lita Cho.

- bpo-21597: The separator between the turtledemo text pane and the drawing
  canvas can now be grabbed and dragged with a mouse.  The code text pane
  can be widened to easily view or copy the full width of the text.  The
  canvas can be widened on small screens.  Original patches by Jan Kanis and
  Lita Cho.

- bpo-18132: Turtledemo buttons no longer disappear when the window is
  shrunk.  Original patches by Jan Kanis and Lita Cho.

- bpo-22043: time.monotonic() is now always available.
  ``threading.Lock.acquire()``, ``threading.RLock.acquire()`` and socket
  operations now use a monotonic clock, instead of the system clock, when a
  timeout is used.

- bpo-21527: Add a default number of workers to ThreadPoolExecutor equal to
  5 times the number of CPUs.  Patch by Claudiu Popa.

- bpo-22216: smtplib now resets its state more completely after a quit.  The
  most obvious consequence of the previous behavior was a STARTTLS failure
  during a connect/starttls/quit/connect/starttls sequence.

- bpo-22098: ctypes' BigEndianStructure and LittleEndianStructure now define
  an empty __slots__ so that subclasses don't always get an instance dict.
  Patch by Claudiu Popa.

- bpo-22185: Fix an occasional RuntimeError in threading.Condition.wait()
  caused by mutation of the waiters queue without holding the lock.  Patch
  by Doug Zongker.

- bpo-22287: On UNIX, _PyTime_gettimeofday() now uses
  clock_gettime(CLOCK_REALTIME) if available. As a side effect, Python now
  depends on the librt library on Solaris and on Linux (only with glibc
  older than 2.17).

- bpo-22182: Use e.args to unpack exceptions correctly in
  distutils.file_util.move_file. Patch by Claudiu Popa.

- The webbrowser module now uses subprocess's start_new_session=True rather
  than a potentially risky preexec_fn=os.setsid call.

- bpo-22042: signal.set_wakeup_fd(fd) now raises an exception if the file
  descriptor is in blocking mode.

- bpo-16808: inspect.stack() now returns a named tuple instead of a tuple.
  Patch by Daniel Shahaf.

- bpo-22236: Fixed Tkinter images copying operations in NoDefaultRoot mode.

- bpo-2527: Add a *globals* argument to timeit functions, in order to
  override the globals namespace in which the timed code is executed. Patch
  by Ben Roberts.

- bpo-22118: Switch urllib.parse to use RFC 3986 semantics for the
  resolution of relative URLs, rather than RFCs 1808 and 2396. Patch by
  Demian Brecht.

- bpo-21549: Added the "members" parameter to TarFile.list().

- bpo-19628: Allow compileall recursion depth to be specified with a -r
  option.

- bpo-15696: Add a __sizeof__ implementation for mmap objects on Windows.

- bpo-22068: Avoided reference loops with Variables and Fonts in Tkinter.

- bpo-22165: SimpleHTTPRequestHandler now supports undecodable file names.

- bpo-15381: Optimized line reading in io.BytesIO.

- bpo-8797: Raise HTTPError on failed Basic Authentication immediately.
  Initial patch by Sam Bull.

- bpo-20729: Restored the use of lazy iterkeys()/itervalues()/iteritems() in
  the mailbox module.

- bpo-21448: Changed FeedParser feed() to avoid O(N\ :sup:`2`) behavior when
  parsing long line. Original patch by Raymond Hettinger.

- bpo-22184: The functools LRU Cache decorator factory now gives an earlier
  and clearer error message when the user forgets the required parameters.

- bpo-17923: glob() patterns ending with a slash no longer match non-dirs on
  AIX.  Based on patch by Delhallt.

- bpo-21725: Added support for RFC 6531 (SMTPUTF8) in smtpd.

- bpo-22176: Update the ctypes module's libffi to v3.1.  This release adds
  support for the Linux AArch64 and POWERPC ELF ABIv2 little endian
  architectures.

- bpo-5411: Added support for the "xztar" format in the shutil module.

- bpo-21121: Don't force 3rd party C extensions to be built with
  -Werror=declaration-after-statement.

- bpo-21975: Fixed crash when using uninitialized sqlite3.Row (in particular
  when unpickling pickled sqlite3.Row).  sqlite3.Row is now initialized in
  the __new__() method.

- bpo-20170: Convert posixmodule to use Argument Clinic.

- bpo-21539: Add an *exists_ok* argument to `Pathlib.mkdir()` to mimic
  `mkdir -p` and `os.makedirs()` functionality.  When true, ignore
  FileExistsErrors.  Patch by Berker Peksag.

- bpo-22127: Bypass IDNA for pure-ASCII host names in the socket module (in
  particular for numeric IPs).

- bpo-21047: set the default value for the *convert_charrefs* argument of
  HTMLParser to True.  Patch by Berker Peksag.

- Add an __all__ to html.entities.

- bpo-15114: the strict mode and argument of HTMLParser, HTMLParser.error,
  and the HTMLParserError exception have been removed.

- bpo-22085: Dropped support of Tk 8.3 in Tkinter.

- bpo-21580: Now Tkinter correctly handles bytes arguments passed to Tk. In
  particular this allows initializing images from binary data.

- bpo-22003: When initialized from a bytes object, io.BytesIO() now defers
  making a copy until it is mutated, improving performance and memory use on
  some use cases. Patch by David Wilson.

- bpo-22018: On Windows, signal.set_wakeup_fd() now also supports sockets. A
  side effect is that Python depends to the WinSock library.

- bpo-22054: Add os.get_blocking() and os.set_blocking() functions to get
  and set the blocking mode of a file descriptor (False if the O_NONBLOCK
  flag is set, True otherwise). These functions are not available on
  Windows.

- bpo-17172: Make turtledemo start as active on OS X even when run with
  subprocess. Patch by Lita Cho.

- bpo-21704: Fix build error for _multiprocessing when semaphores are not
  available. Patch by Arfrever Frehtes Taifersar Arahesis.

- bpo-20173: Convert sha1, sha256, sha512 and md5 to ArgumentClinic. Patch
  by Vajrasky Kok.

- Fix repr(_socket.socket) on Windows 64-bit: don't fail with OverflowError
  on closed socket. repr(socket.socket) already works fine.

- bpo-22033: Reprs of most Python implemented classes now contain actual
  class name instead of hardcoded one.

- bpo-21947: The dis module can now disassemble generator-iterator objects
  based on their gi_code attribute. Patch by Clement Rouault.

- bpo-16133: The asynchat.async_chat.handle_read() method now ignores
  BlockingIOError exceptions.

- bpo-22044: Fixed premature DECREF in call_tzinfo_method. Patch by Tom
  Flanagan.

- bpo-19884: readline: Disable the meta modifier key if stdout is not a
  terminal to not write the ANSI sequence ``"\033[1034h"`` into stdout. This
  sequence is used on some terminal (ex: TERM=xterm-256color") to enable
  support of 8 bit characters.

- bpo-4350: Removed a number of out-of-dated and non-working for a long time
  Tkinter methods.

- bpo-6167: Scrollbar.activate() now returns the name of active element if
  the argument is not specified.  Scrollbar.set() now always accepts only 2
  arguments.

- bpo-15275: Clean up and speed up the ntpath module.

- bpo-21888: plistlib's load() and loads() now work if the fmt parameter is
  specified.

- bpo-22032: __qualname__ instead of __name__ is now always used to format
  fully qualified class names of Python implemented classes.

- bpo-22031: Reprs now always use hexadecimal format with the "0x" prefix
  when contain an id in form " at 0x...".

- bpo-22018: signal.set_wakeup_fd() now raises an OSError instead of a
  ValueError on ``fstat()`` failure.

- bpo-21044: tarfile.open() now handles fileobj with an integer 'name'
  attribute.  Based on patch by Antoine Pietri.

- bpo-21966: Respect -q command-line option when code module is ran.

- bpo-19076: Don't pass the redundant 'file' argument to self.error().

- bpo-16382: Improve exception message of warnings.warn() for bad category.
  Initial patch by Phil Elson.

- bpo-21932: os.read() now uses a :c:func:`Py_ssize_t` type instead of
  :c:type:`int` for the size to support reading more than 2 GB at once. On
  Windows, the size is truncated to INT_MAX. As any call to os.read(), the
  OS may read less bytes than the number of requested bytes.

- bpo-21942: Fixed source file viewing in pydoc's server mode on Windows.

- bpo-11259: asynchat.async_chat().set_terminator() now raises a ValueError
  if the number of received bytes is negative.

- bpo-12523: asynchat.async_chat.push() now raises a TypeError if it doesn't
  get a bytes string

- bpo-21707: Add missing kwonlyargcount argument to
  ModuleFinder.replace_paths_in_code().

- bpo-20639: calling Path.with_suffix('') allows removing the suffix again.
  Patch by July Tikhonov.

- bpo-21714: Disallow the construction of invalid paths using
  Path.with_name().  Original patch by Antony Lee.

- bpo-15014: Added 'auth' method to smtplib to make implementing auth
  mechanisms simpler, and used it internally in the login method.

- bpo-21151: Fixed a segfault in the winreg module when ``None`` is passed
  as a ``REG_BINARY`` value to SetValueEx.  Patch by John Ehresman.

- bpo-21090: io.FileIO.readall() does not ignore I/O errors anymore. Before,
  it ignored I/O errors if at least the first C call read() succeed.

- bpo-5800: headers parameter of wsgiref.headers.Headers is now optional.
  Initial patch by Pablo Torres Navarrete and SilentGhost.

- bpo-21781: ssl.RAND_add() now supports strings longer than 2 GB.

- bpo-21679: Prevent extraneous fstat() calls during open().  Patch by
  Bohuslav Kabrda.

- bpo-21863: cProfile now displays the module name of C extension functions,
  in addition to their own name.

- bpo-11453: asyncore: emit a ResourceWarning when an unclosed file_wrapper
  object is destroyed. The destructor now closes the file if needed. The
  close() method can now be called twice: the second call does nothing.

- bpo-21858: Better handling of Python exceptions in the sqlite3 module.

- bpo-21476: Make sure the email.parser.BytesParser TextIOWrapper is
  discarded after parsing, so the input file isn't unexpectedly closed.

- bpo-20295: imghdr now recognizes OpenEXR format images.

- bpo-21729: Used the "with" statement in the dbm.dumb module to ensure
  files closing. Patch by Claudiu Popa.

- bpo-21491: socketserver: Fix a race condition in child processes reaping.

- bpo-21719: Added the ``st_file_attributes`` field to os.stat_result on
  Windows.

- bpo-21832: Require named tuple inputs to be exact strings.

- bpo-21722: The distutils "upload" command now exits with a non-zero return
  code when uploading fails.  Patch by Martin Dengler.

- bpo-21723: asyncio.Queue: support any type of number (ex: float) for the
  maximum size. Patch written by Vajrasky Kok.

- bpo-21711: support for "site-python" directories has now been removed from
  the site module (it was deprecated in 3.4).

- bpo-17552: new socket.sendfile() method allowing a file to be sent over a
  socket by using high-performance os.sendfile() on UNIX. Patch by Giampaolo
  Rodola'.

- bpo-18039: dbm.dump.open() now always creates a new database when the flag
  has the value 'n'.  Patch by Claudiu Popa.

- bpo-21326: Add a new is_closed() method to asyncio.BaseEventLoop.
  run_forever() and run_until_complete() methods of asyncio.BaseEventLoop
  now raise an exception if the event loop was closed.

- bpo-21766: Prevent a security hole in CGIHTTPServer by URL unquoting paths
  before checking for a CGI script at that path.

- bpo-21310: Fixed possible resource leak in failed open().

- bpo-21256: Printout of keyword args should be in deterministic order in a
  mock function call. This will help to write better doctests.

- bpo-21677: Fixed chaining nonnormalized exceptions in io close() methods.

- bpo-11709: Fix the pydoc.help function to not fail when sys.stdin is not a
  valid file.

- bpo-21515: tempfile.TemporaryFile now uses os.O_TMPFILE flag is available.

- bpo-13223: Fix pydoc.writedoc so that the HTML documentation for methods
  that use 'self' in the example code is generated correctly.

- bpo-21463: In urllib.request, fix pruning of the FTP cache.

- bpo-21618: The subprocess module could fail to close open fds that were
  inherited by the calling process and already higher than POSIX resource
  limits would otherwise allow.  On systems with a functioning /proc/self/fd
  or /dev/fd interface the max is now ignored and all fds are closed.

- bpo-20383: Introduce importlib.util.module_from_spec() as the preferred
  way to create a new module.

- bpo-21552: Fixed possible integer overflow of too long string lengths in
  the tkinter module on 64-bit platforms.

- bpo-14315: The zipfile module now ignores extra fields in the central
  directory that are too short to be parsed instead of letting a
  struct.unpack error bubble up as this "bad data" appears in many real
  world zip files in the wild and is ignored by other zip tools.

- bpo-13742: Added "key" and "reverse" parameters to heapq.merge(). (First
  draft of patch contributed by Simon Sapin.)

- bpo-21402: tkinter.ttk now works when default root window is not set.

- bpo-3015: _tkinter.create() now creates tkapp object with wantobject=1 by
  default.

- bpo-10203: sqlite3.Row now truly supports sequence protocol.  In
  particular it supports reverse() and negative indices.  Original patch by
  Claudiu Popa.

- bpo-18807: If copying (no symlinks) specified for a venv, then the python
  interpreter aliases (python, python3) are now created by copying rather
  than symlinking.

- bpo-20197: Added support for the WebP image type in the imghdr module.
  Patch by Fabrice Aneche and Claudiu Popa.

- bpo-21513: Speedup some properties of IP addresses (IPv4Address,
  IPv6Address) such as .is_private or .is_multicast.

- bpo-21137: Improve the repr for threading.Lock() and its variants by
  showing the "locked" or "unlocked" status.  Patch by Berker Peksag.

- bpo-21538: The plistlib module now supports loading of binary plist files
  when reference or offset size is not a power of two.

- bpo-21455: Add a default backlog to socket.listen().

- bpo-21525: Most Tkinter methods which accepted tuples now accept lists
  too.

- bpo-22166: With the assistance of a new internal _codecs._forget_codec
  helping function, test_codecs now clears the encoding caches to avoid the
  appearance of a reference leak

- bpo-22236: Tkinter tests now don't reuse default root window.  New root
  window is created for every test class.

- bpo-10744: Fix :pep:`3118` format strings on ctypes objects with a
  nontrivial shape.

- bpo-20826: Optimize ipaddress.collapse_addresses().

- bpo-21487: Optimize ipaddress.summarize_address_range() and
  ipaddress.{IPv4Network,IPv6Network}.subnets().

- bpo-21486: Optimize parsing of netmasks in ipaddress.IPv4Network and
  ipaddress.IPv6Network.

- bpo-13916: Disallowed the surrogatepass error handler for non UTF-\*
  encodings.

- bpo-20998: Fixed re.fullmatch() of repeated single character pattern with
  ignore case. Original patch by Matthew Barnett.

- bpo-21075: fileinput.FileInput now reads bytes from standard stream if
  binary mode is specified.  Patch by Sam Kimbrel.

- bpo-19775: Add a samefile() method to pathlib Path objects.  Initial patch
  by Vajrasky Kok.

- bpo-21226: Set up modules properly in PyImport_ExecCodeModuleObject (and
  friends).

- bpo-21398: Fix a unicode error in the pydoc pager when the documentation
  contains characters not encodable to the stdout encoding.

- bpo-16531: ipaddress.IPv4Network and ipaddress.IPv6Network now accept an
  (address, netmask) tuple argument, so as to easily construct network
  objects from existing addresses.

- bpo-21156: importlib.abc.InspectLoader.source_to_code() is now a
  staticmethod.

- bpo-21424: Simplified and optimized heaqp.nlargest() and nmsmallest() to
  make fewer tuple comparisons.

- bpo-21396: Fix TextIOWrapper(..., write_through=True) to not force a
  flush() on the underlying binary stream.  Patch by akira.

- bpo-18314: Unlink now removes junctions on Windows. Patch by Kim Gräsman

- bpo-21088: Bugfix for curses.window.addch() regression in 3.4.0. In
  porting to Argument Clinic, the first two arguments were reversed.

- bpo-21407: _decimal: The module now supports function signatures.

- bpo-10650: Remove the non-standard 'watchexp' parameter from the
  Decimal.quantize() method in the Python version.  It had never been
  present in the C version.

- bpo-21469: Reduced the risk of false positives in robotparser by checking
  to make sure that robots.txt has been read or does not exist prior to
  returning True in can_fetch().

- bpo-19414: Have the OrderedDict mark deleted links as unusable. This gives
  an early failure if the link is deleted during iteration.

- bpo-21421: Add __slots__ to the MappingViews ABC. Patch by Josh Rosenberg.

- bpo-21101: Eliminate double hashing in the C speed-up code for
  collections.Counter().

- bpo-21321: itertools.islice() now releases the reference to the source
  iterator when the slice is exhausted.  Patch by Anton Afanasyev.

- bpo-21057: TextIOWrapper now allows the underlying binary stream's read()
  or read1() method to return an arbitrary bytes-like object (such as a
  memoryview). Patch by Nikolaus Rath.

- bpo-20951: SSLSocket.send() now raises either SSLWantReadError or
  SSLWantWriteError on a non-blocking socket if the operation would block.
  Previously, it would return 0.  Patch by Nikolaus Rath.

- bpo-13248: removed previously deprecated asyncore.dispatcher __getattr__
  cheap inheritance hack.

- bpo-9815: assertRaises now tries to clear references to local variables in
  the exception's traceback.

- bpo-19940: ssl.cert_time_to_seconds() now interprets the given time string
  in the UTC timezone (as specified in RFC 5280), not the local timezone.

- bpo-13204: Calling sys.flags.__new__ would crash the interpreter, now it
  raises a TypeError.

- bpo-19385: Make operations on a closed dbm.dumb database always raise the
  same exception.

- bpo-21207: Detect when the os.urandom cached fd has been closed or
  replaced, and open it anew.

- bpo-21291: subprocess's Popen.wait() is now thread safe so that multiple
  threads may be calling wait() or poll() on a Popen instance at the same
  time without losing the Popen.returncode value.

- bpo-21127: Path objects can now be instantiated from str subclass
  instances (such as ``numpy.str_``).

- bpo-15002: urllib.response object to use _TemporaryFileWrapper (and
  _TemporaryFileCloser) facility. Provides a better way to handle file
  descriptor close. Patch contributed by Christian Theune.

- bpo-12220: mindom now raises a custom ValueError indicating it doesn't
  support spaces in URIs instead of letting a 'split' ValueError bubble up.

- bpo-21068: The ssl.PROTOCOL* constants are now enum members.

- bpo-21276: posixmodule: Don't define USE_XATTRS on KFreeBSD and the Hurd.

- bpo-21262: New method assert_not_called for Mock. It raises AssertionError
  if the mock has been called.

- bpo-21238: New keyword argument `unsafe` to Mock. It raises
  `AttributeError` incase of an attribute startswith assert or assret.

- bpo-20896: ssl.get_server_certificate() now uses PROTOCOL_SSLv23, not
  PROTOCOL_SSLv3, for maximum compatibility.

- bpo-21239: patch.stopall() didn't work deterministically when the same
  name was patched more than once.

- bpo-21203: Updated fileConfig and dictConfig to remove inconsistencies.
  Thanks to Jure Koren for the patch.

- bpo-21222: Passing name keyword argument to mock.create_autospec now
  works.

- bpo-21197: Add lib64 -> lib symlink in venvs on 64-bit non-OS X POSIX.

- bpo-17498: Some SMTP servers disconnect after certain errors, violating
  strict RFC conformance.  Instead of losing the error code when we issue
  the subsequent RSET, smtplib now returns the error code and defers raising
  the SMTPServerDisconnected error until the next command is issued.

- bpo-17826: setting an iterable side_effect on a mock function created by
  create_autospec now works. Patch by Kushal Das.

- bpo-7776: Fix ``Host:`` header and reconnection when using
  http.client.HTTPConnection.set_tunnel(). Patch by Nikolaus Rath.

- bpo-20968: unittest.mock.MagicMock now supports division. Patch by
  Johannes Baiter.

- bpo-21529: Fix arbitrary memory access in JSONDecoder.raw_decode with a
  negative second parameter. Bug reported by Guido Vranken. (See also:
  CVE-2014-4616)

- bpo-21169: getpass now handles non-ascii characters that the input stream
  encoding cannot encode by re-encoding using the replace error handler.

- bpo-21171: Fixed undocumented filter API of the rot13 codec. Patch by
  Berker Peksag.

- bpo-20539: Improved math.factorial error message for large positive inputs
  and changed exception type (OverflowError -> ValueError) for large
  negative inputs.

- bpo-21172: isinstance check relaxed from dict to collections.Mapping.

- bpo-21155: asyncio.EventLoop.create_unix_server() now raises a ValueError
  if path and sock are specified at the same time.

- bpo-21136: Avoid unnecessary normalization of Fractions resulting from
  power and other operations.  Patch by Raymond Hettinger.

- bpo-17621: Introduce importlib.util.LazyLoader.

- bpo-21076: signal module constants were turned into enums. Patch by
  Giampaolo Rodola'.

- bpo-20636: Improved the repr of Tkinter widgets.

- bpo-19505: The items, keys, and values views of OrderedDict now support
  reverse iteration using reversed().

- bpo-21149: Improved thread-safety in logging cleanup during interpreter
  shutdown. Thanks to Devin Jeanpierre for the patch.

- bpo-21058: Fix a leak of file descriptor in
  :func:`tempfile.NamedTemporaryFile`, close the file descriptor if
  :func:`io.open` fails

- bpo-21200: Return None from pkgutil.get_loader() when __spec__ is missing.

- bpo-21013: Enhance ssl.create_default_context() when used for server side
  sockets to provide better security by default.

- bpo-20145: `assertRaisesRegex` and `assertWarnsRegex` now raise a
  TypeError if the second argument is not a string or compiled regex.

- bpo-20633: Replace relative import by absolute import.

- bpo-20980: Stop wrapping exception when using ThreadPool.

- bpo-21082: In os.makedirs, do not set the process-wide umask. Note this
  changes behavior of makedirs when exist_ok=True.

- bpo-20990: Fix issues found by pyflakes for multiprocessing.

- bpo-21015: SSL contexts will now automatically select an elliptic curve
  for ECDH key exchange on OpenSSL 1.0.2 and later, and otherwise default to
  "prime256v1".

- bpo-21000: Improve the command-line interface of json.tool.

- bpo-20995: Enhance default ciphers used by the ssl module to enable better
  security and prioritize perfect forward secrecy.

- bpo-20884: Don't assume that __file__ is defined on importlib.__init__.

- bpo-21499: Ignore __builtins__ in several test_importlib.test_api tests.

- bpo-20627: xmlrpc.client.ServerProxy is now a context manager.

- bpo-19165: The formatter module now raises DeprecationWarning instead of
  PendingDeprecationWarning.

- bpo-13936: Remove the ability of datetime.time instances to be considered
  false in boolean contexts.

- bpo-18931: selectors module now supports /dev/poll on Solaris. Patch by
  Giampaolo Rodola'.

- bpo-19977: When the ``LC_TYPE`` locale is the POSIX locale (``C`` locale),
  :py:data:`sys.stdin` and :py:data:`sys.stdout` are now using the
  ``surrogateescape`` error handler, instead of the ``strict`` error
  handler.

- bpo-20574: Implement incremental decoder for cp65001 code (Windows code
  page 65001, Microsoft UTF-8).

- bpo-20879: Delay the initialization of encoding and decoding tables for
  base32, ascii85 and base85 codecs in the base64 module, and delay the
  initialization of the unquote_to_bytes() table of the urllib.parse module,
  to not waste memory if these modules are not used.

- bpo-19157: Include the broadcast address in the usuable hosts for IPv6 in
  ipaddress.

- bpo-11599: When an external command (e.g. compiler) fails, distutils now
  prints out the whole command line (instead of just the command name) if
  the environment variable DISTUTILS_DEBUG is set.

- bpo-4931: distutils should not produce unhelpful "error: None" messages
  anymore. distutils.util.grok_environment_error is kept but doc-deprecated.

- bpo-20875: Prevent possible gzip "'read' is not defined" NameError. Patch
  by Claudiu Popa.

- bpo-11558: ``email.message.Message.attach`` now returns a more useful
  error message if ``attach`` is called on a message for which
  ``is_multipart`` is False.

- bpo-20283: RE pattern methods now accept the string keyword parameters as
  documented. The pattern and source keyword parameters are left as
  deprecated aliases.

- bpo-20778: Fix modulefinder to work with bytecode-only modules.

- bpo-20791: copy.copy() now doesn't make a copy when the input is a bytes
  object. Initial patch by Peter Otten.

- bpo-19748: On AIX, time.mktime() now raises an OverflowError for year
  outsize range [1902; 2037].

- bpo-19573: inspect.signature: Use enum for parameter kind constants.

- bpo-20726: inspect.signature: Make Signature and Parameter picklable.

- bpo-17373: Add inspect.Signature.from_callable method.

- bpo-20378: Improve repr of inspect.Signature and inspect.Parameter.

- bpo-20816: Fix inspect.getcallargs() to raise correct TypeError for
  missing keyword-only arguments. Patch by Jeremiah Lowin.

- bpo-20817: Fix inspect.getcallargs() to fail correctly if more than 3
  arguments are missing. Patch by Jeremiah Lowin.

- bpo-6676: Ensure a meaningful exception is raised when attempting to parse
  more than one XML document per pyexpat xmlparser instance. (Original
  patches by Hirokazu Yamamoto and Amaury Forgeot d'Arc, with suggested
  wording by David Gutteridge)

- bpo-21117: Fix inspect.signature to better support functools.partial. Due
  to the specifics of functools.partial implementation,
  positional-or-keyword arguments passed as keyword arguments become
  keyword-only.

- bpo-20334: inspect.Signature and inspect.Parameter are now hashable.
  Thanks to Antony Lee for bug reports and suggestions.

- bpo-15916: doctest.DocTestSuite returns an empty unittest.TestSuite
  instead of raising ValueError if it finds no tests

- bpo-21209: Fix asyncio.tasks.CoroWrapper to workaround a bug in yield-from
  implementation in CPythons prior to 3.4.1.

- asyncio: Add gi_{frame,running,code} properties to CoroWrapper (upstream
  issue #163).

- bpo-21311: Avoid exception in _osx_support with non-standard compiler
  configurations. Patch by John Szakmeister.

- bpo-11571: Ensure that the turtle window becomes the topmost window when
  launched on OS X.

- bpo-21801: Validate that __signature__ is None or an instance of
  Signature.

- bpo-21923: Prevent AttributeError in
  distutils.sysconfig.customize_compiler due to possible uninitialized
  _config_vars.

- bpo-21323: Fix http.server to again handle scripts in CGI subdirectories,
  broken by the fix for security issue #19435.  Patch by Zach Byrne.

- bpo-22733: Fix ffi_prep_args not zero-extending argument values correctly
  on 64-bit Windows.

- bpo-23302: Default to TCP_NODELAY=1 upon establishing an HTTPConnection.
  Removed use of hard-coded MSS as it's an optimization that's no longer
  needed with Nagle disabled.

IDLE
----

- bpo-20577: Configuration of the max line length for the FormatParagraph
  extension has been moved from the General tab of the Idle preferences
  dialog to the FormatParagraph tab of the Config Extensions dialog. Patch
  by Tal Einat.

- bpo-16893: Update Idle doc chapter to match current Idle and add new
  information.

- bpo-3068: Add Idle extension configuration dialog to Options menu. Changes
  are written to HOME/.idlerc/config-extensions.cfg. Original patch by Tal
  Einat.

- bpo-16233: A module browser (File : Class Browser, Alt+C) requires an
  editor window with a filename.  When Class Browser is requested otherwise,
  from a shell, output window, or 'Untitled' editor, Idle no longer displays
  an error box. It now pops up an Open Module box (Alt+M). If a valid name
  is entered and a module is opened, a corresponding browser is also opened.

- bpo-4832: Save As to type Python files automatically adds .py to the name
  you enter (even if your system does not display it).  Some systems
  automatically add .txt when type is Text files.

- bpo-21986: Code objects are not normally pickled by the pickle module. To
  match this, they are no longer pickled when running under Idle.

- bpo-17390: Adjust Editor window title; remove 'Python', move version to
  end.

- bpo-14105: Idle debugger breakpoints no longer disappear when inserting or
  deleting lines.

- bpo-17172: Turtledemo can now be run from Idle. Currently, the entry is on
  the Help menu, but it may move to Run. Patch by Ramchandra Apt and Lita
  Cho.

- bpo-21765: Add support for non-ascii identifiers to HyperParser.

- bpo-21940: Add unittest for WidgetRedirector. Initial patch by Saimadhav
  Heblikar.

- bpo-18592: Add unittest for SearchDialogBase. Patch by Phil Webster.

- bpo-21694: Add unittest for ParenMatch. Patch by Saimadhav Heblikar.

- bpo-21686: add unittest for HyperParser. Original patch by Saimadhav
  Heblikar.

- bpo-12387: Add missing upper(lower)case versions of default Windows key
  bindings for Idle so Caps Lock does not disable them. Patch by Roger
  Serwy.

- bpo-21695: Closing a Find-in-files output window while the search is still
  in progress no longer closes Idle.

- bpo-18910: Add unittest for textView. Patch by Phil Webster.

- bpo-18292: Add unittest for AutoExpand. Patch by Saihadhav Heblikar.

- bpo-18409: Add unittest for AutoComplete. Patch by Phil Webster.

- bpo-21477: htest.py - Improve framework, complete set of tests. Patches by
  Saimadhav Heblikar

- bpo-18104: Add idlelib/idle_test/htest.py with a few sample tests to begin
  consolidating and improving human-validated tests of Idle. Change other
  files as needed to work with htest.  Running the module as __main__ runs
  all tests.

- bpo-21139: Change default paragraph width to 72, the :pep:`8`
  recommendation.

- bpo-21284: Paragraph reformat test passes after user changes reformat
  width.

- bpo-17654: Ensure IDLE menus are customized properly on OS X for
  non-framework builds and for all variants of Tk.

- bpo-23180: Rename IDLE "Windows" menu item to "Window". Patch by Al
  Sweigart.

Build
-----

- bpo-15506: Use standard PKG_PROG_PKG_CONFIG autoconf macro in the
  configure script.

- bpo-22935: Allow the ssl module to be compiled if openssl doesn't support
  SSL 3.

- bpo-22592: Drop support of the Borland C compiler to build Python. The
  distutils module still supports it to build extensions.

- bpo-22591: Drop support of MS-DOS, especially of the DJGPP compiler
  (MS-DOS port of GCC).

- bpo-16537: Check whether self.extensions is empty in setup.py. Patch by
  Jonathan Hosmer.

- bpo-22359: Remove incorrect uses of recursive make.  Patch by Jonas
  Wagner.

- bpo-21958: Define HAVE_ROUND when building with Visual Studio 2013 and
  above.  Patch by Zachary Turner.

- bpo-18093: the programs that embed the CPython runtime are now in a
  separate "Programs" directory, rather than being kept in the Modules
  directory.

- bpo-15759: "make suspicious", "make linkcheck" and "make doctest" in Doc/
  now display special message when and only when there are failures.

- bpo-21141: The Windows build process no longer attempts to find Perl,
  instead relying on OpenSSL source being configured and ready to build.
  The ``PCbuild\build_ssl.py`` script has been re-written and re-named to
  ``PCbuild\prepare_ssl.py``, and takes care of configuring OpenSSL source
  for both 32 and 64 bit platforms.  OpenSSL sources obtained from
  svn.python.org will always be pre-configured and ready to build.

- bpo-21037: Add a build option to enable AddressSanitizer support.

- bpo-19962: The Windows build process now creates "python.bat" in the root
  of the source tree, which passes all arguments through to the most
  recently built interpreter.

- bpo-21285: Refactor and fix curses configure check to always search in a
  ncursesw directory.

- bpo-15234: For BerkeleyDB and Sqlite, only add the found library and
  include directories if they aren't already being searched. This avoids an
  explicit runtime library dependency.

- bpo-17861: Tools/scripts/generate_opcode_h.py automatically regenerates
  Include/opcode.h from Lib/opcode.py if the latter gets any change.

- bpo-20644: OS X installer build support for documentation build changes in
  3.4.1: assume externally supplied sphinx-build is available in /usr/bin.

- bpo-20022: Eliminate use of deprecated bundlebuilder in OS X builds.

- bpo-15968: Incorporated Tcl, Tk, and Tix builds into the Windows build
  solution.

- bpo-17095: Fix Modules/Setup *shared* support.

- bpo-21811: Anticipated fixes to support OS X versions > 10.9.

- bpo-21166: Prevent possible segfaults and other random failures of python
  --generate-posix-vars in pybuilddir.txt build target.

- bpo-18096: Fix library order returned by python-config.

- bpo-17219: Add library build dir for Python extension cross-builds.

- bpo-22919: Windows build updated to support VC 14.0 (Visual Studio 2015),
  which will be used for the official release.

- bpo-21236: Build _msi.pyd with cabinet.lib instead of fci.lib

- bpo-17128: Use private version of OpenSSL for OS X 10.5+ installer.

C API
-----

- bpo-14203: Remove obsolete support for view==NULL in PyBuffer_FillInfo(),
  bytearray_getbuffer(), bytesiobuf_getbuffer() and array_buffer_getbuf().
  All functions now raise BufferError in that case.

- bpo-22445: PyBuffer_IsContiguous() now implements precise contiguity
  tests, compatible with NumPy's NPY_RELAXED_STRIDES_CHECKING compilation
  flag.  Previously the function reported false negatives for corner cases.

- bpo-22079: PyType_Ready() now checks that statically allocated type has no
  dynamically allocated bases.

- bpo-22453: Removed non-documented macro PyObject_REPR().

- bpo-18395: Rename ``_Py_char2wchar()`` to :c:func:`Py_DecodeLocale`,
  rename ``_Py_wchar2char()`` to :c:func:`Py_EncodeLocale`, and document
  these functions.

- bpo-21233: Add new C functions: PyMem_RawCalloc(), PyMem_Calloc(),
  PyObject_Calloc(), _PyObject_GC_Calloc(). bytes(int) is now using
  ``calloc()`` instead of ``malloc()`` for large objects which is faster and
  use less memory.

- bpo-20942: PyImport_ImportFrozenModuleObject() no longer sets __file__ to
  match what importlib does; this affects _frozen_importlib as well as any
  module loaded using imp.init_frozen().

Documentation
-------------

- bpo-19548: Update the codecs module documentation to better cover the
  distinction between text encodings and other codecs, together with other
  clarifications. Patch by Martin Panter.

- bpo-22394: Doc/Makefile now supports ``make venv PYTHON=../python`` to
  create a venv for generating the documentation, e.g., ``make html
  PYTHON=venv/bin/python3``.

- bpo-21514: The documentation of the json module now refers to new JSON RFC
  7159 instead of obsoleted RFC 4627.

- bpo-21777: The binary sequence methods on bytes and bytearray are now
  documented explicitly, rather than assuming users will be able to derive
  the expected behaviour from the behaviour of the corresponding str
  methods.

- bpo-6916: undocument deprecated asynchat.fifo class.

- bpo-17386: Expanded functionality of the ``Doc/make.bat`` script to make
  it much more comparable to ``Doc/Makefile``.

- bpo-21312: Update the thread_foobar.h template file to include newer
  threading APIs. Patch by Jack McCracken.

- bpo-21043: Remove the recommendation for specific CA organizations and to
  mention the ability to load the OS certificates.

- bpo-20765: Add missing documentation for PurePath.with_name() and
  PurePath.with_suffix().

- bpo-19407: New package installation and distribution guides based on the
  Python Packaging Authority tools. Existing guides have been retained as
  legacy links from the distutils docs, as they still contain some required
  reference material for tool developers that isn't recorded anywhere else.

- bpo-19697: Document cases where __main__.__spec__ is None.

Tests
-----

- bpo-18982: Add tests for CLI of the calendar module.

- bpo-19548: Added some additional checks to test_codecs to ensure that
  statements in the updated documentation remain accurate. Patch by Martin
  Panter.

- bpo-22838: All test_re tests now work with unittest test discovery.

- bpo-22173: Update lib2to3 tests to use unittest test discovery.

- bpo-16000: Convert test_curses to use unittest.

- bpo-21456: Skip two tests in test_urllib2net.py if _ssl module not
  present. Patch by Remi Pointel.

- bpo-20746: Fix test_pdb to run in refleak mode (-R).  Patch by Xavier de
  Gaye.

- bpo-22060: test_ctypes has been somewhat cleaned up and simplified; it now
  uses unittest test discovery to find its tests.

- bpo-22104: regrtest.py no longer holds a reference to the suite of tests
  loaded from test modules that don't define test_main().

- bpo-22111: Assorted cleanups in test_imaplib.  Patch by Milan Oberkirch.

- bpo-22002: Added ``load_package_tests`` function to test.support and used
  it to implement/augment test discovery in test_asyncio, test_email,
  test_importlib, test_json, and test_tools.

- bpo-21976: Fix test_ssl to accept LibreSSL version strings.  Thanks to
  William Orr.

- bpo-21918: Converted test_tools from a module to a package containing
  separate test files for each tested script.

- bpo-9554: Use modern unittest features in test_argparse. Initial patch by
  Denver Coneybeare and Radu Voicilas.

- bpo-20155: Changed HTTP method names in failing tests in test_httpservers
  so that packet filtering software (specifically Windows Base Filtering
  Engine) does not interfere with the transaction semantics expected by the
  tests.

- bpo-19493: Refactored the ctypes test package to skip tests explicitly
  rather than silently.

- bpo-18492: All resources are now allowed when tests are not run by
  regrtest.py.

- bpo-21634: Fix pystone micro-benchmark: use floor division instead of true
  division to benchmark integers instead of floating point numbers. Set
  pystone version to 1.2. Patch written by Lennart Regebro.

- bpo-21605: Added tests for Tkinter images.

- bpo-21493: Added test for ntpath.expanduser().  Original patch by Claudiu
  Popa.

- bpo-19925: Added tests for the spwd module. Original patch by Vajrasky
  Kok.

- bpo-21522: Added Tkinter tests for Listbox.itemconfigure(),
  PanedWindow.paneconfigure(), and Menu.entryconfigure().

- bpo-17756: Fix test_code test when run from the installed location.

- bpo-17752: Fix distutils tests when run from the installed location.

- bpo-18604: Consolidated checks for GUI availability.  All platforms now at
  least check whether Tk can be instantiated when the GUI resource is
  requested.

- bpo-21275: Fix a socket test on KFreeBSD.

- bpo-21223: Pass test_site/test_startup_imports when some of the extensions
  are built as builtins.

- bpo-20635: Added tests for Tk geometry managers.

- Add test case for freeze.

- bpo-20743: Fix a reference leak in test_tcl.

- bpo-21097: Move test_namespace_pkgs into test_importlib.

- bpo-21503: Use test_both() consistently in test_importlib.

- bpo-20939: Avoid various network test failures due to new redirect of
  http://www.python.org/ to https://www.python.org: use
  http://www.example.com instead.

- bpo-20668: asyncio tests no longer rely on tests.txt file. (Patch by
  Vajrasky Kok)

- bpo-21093: Prevent failures of ctypes test_macholib on OS X if a copy of
  libz exists in $HOME/lib or /usr/local/lib.

- bpo-22770: Prevent some Tk segfaults on OS X when running gui tests.

- bpo-23211: Workaround test_logging failure on some OS X 10.6 systems.

- bpo-23345: Prevent test_ssl failures with large OpenSSL patch level values
  (like 0.9.8zc).

Tools/Demos
-----------

- bpo-22314: pydoc now works when the LINES environment variable is set.

- bpo-22615: Argument Clinic now supports the "type" argument for the int
  converter. This permits using the int converter with enums and typedefs.

- bpo-20076: The makelocalealias.py script no longer ignores UTF-8 mapping.

- bpo-20079: The makelocalealias.py script now can parse the SUPPORTED file
  from glibc sources and supports command line options for source paths.

- bpo-22201: Command-line interface of the zipfile module now correctly
  extracts ZIP files with directory entries.  Patch by Ryan Wilson.

- bpo-22120: For functions using an unsigned integer return converter,
  Argument Clinic now generates a cast to that type for the comparison to -1
  in the generated code.  (This suppresses a compilation warning.)

- bpo-18974: Tools/scripts/diff.py now uses argparse instead of optparse.

- bpo-21906: Make Tools/scripts/md5sum.py work in Python 3. Patch by Zachary
  Ware.

- bpo-21629: Fix Argument Clinic's "--converters" feature.

- Add support for ``yield from`` to 2to3.

- Add support for the :pep:`465` matrix multiplication operator to 2to3.

- bpo-16047: Fix module exception list and __file__ handling in freeze.
  Patch by Meador Inge.

- bpo-11824: Consider ABI tags in freeze. Patch by Meador Inge.

- bpo-20535: PYTHONWARNING no longer affects the run_tests.py script. Patch
  by Arfrever Frehtes Taifersar Arahesis.

Windows
-------

- bpo-23260: Update Windows installer

- The bundled version of Tcl/Tk has been updated to 8.6.3.  The most visible
  result of this change is the addition of new native file dialogs when
  running on Windows Vista or newer.  See Tcl/Tk's TIP 432 for more
  information.  Also, this version of Tcl/Tk includes support for Windows
  10.

- bpo-17896: The Windows build scripts now expect external library sources
  to be in ``PCbuild\..\externals`` rather than ``PCbuild\..\..``.

- bpo-17717: The Windows build scripts now use a copy of NASM pulled from
  svn.python.org to build OpenSSL.

- bpo-21907: Improved the batch scripts provided for building Python.

- bpo-22644: The bundled version of OpenSSL has been updated to 1.0.1j.

- bpo-10747: Use versioned labels in the Windows start menu. Patch by Olive
  Kilburn.

- bpo-22980: .pyd files with a version and platform tag (for example,
  ".cp35-win32.pyd") will now be loaded in preference to those without tags.


**(For information about older versions, consult the HISTORY file.)**
