path: root/Doc/whatsnew/3.13.rst

****************************
  What's New In Python 3.13
****************************

:Editor: TBD

.. Rules for maintenance:

   * Anyone can add text to this document.  Do not spend very much time
   on the wording of your changes, because your text will probably
   get rewritten to some degree.

   * The maintainer will go through Misc/NEWS periodically and add
   changes; it's therefore more important to add your changes to
   Misc/NEWS than to this file.

   * This is not a complete list of every single change; completeness
   is the purpose of Misc/NEWS.  Some changes I consider too small
   or esoteric to include.  If such a change is added to the text,
   I'll just remove it.  (This is another reason you shouldn't spend
   too much time on writing your addition.)

   * If you want to draw your new text to the attention of the
   maintainer, add 'XXX' to the beginning of the paragraph or
   section.

   * It's OK to just add a fragmentary note about a change.  For
   example: "XXX Describe the transmogrify() function added to the
   socket module."  The maintainer will research the change and
   write the necessary text.

   * You can comment out your additions if you like, but it's not
   necessary (especially when a final release is some months away).

   * Credit the author of a patch or bugfix.   Just the name is
   sufficient; the e-mail address isn't necessary.

   * It's helpful to add the issue number as a comment:

   XXX Describe the transmogrify() function added to the socket
   module.
   (Contributed by P.Y. Developer in :gh:`12345`.)

   This saves the maintainer the effort of going through the VCS log
   when researching a change.

This article explains the new features in Python 3.13, compared to 3.12.

For full details, see the :ref:`changelog <changelog>`.

.. note::

   Prerelease users should be aware that this document is currently in draft
   form. It will be updated substantially as Python 3.13 moves towards release,
   so it's worth checking back even after reading earlier versions.


Summary -- Release highlights
=============================

.. This section singles out the most important changes in Python 3.13.
   Brevity is key.


.. PEP-sized items next.

Important deprecations, removals or restrictions:

* :ref:`PEP 594 <whatsnew313-pep594>`: The remaining 19 "dead batteries"
  have been removed from the standard library:
  :mod:`!aifc`, :mod:`!audioop`, :mod:`!cgi`, :mod:`!cgitb`, :mod:`!chunk`,
  :mod:`!crypt`, :mod:`!imghdr`, :mod:`!mailcap`, :mod:`!msilib`, :mod:`!nis`,
  :mod:`!nntplib`, :mod:`!ossaudiodev`, :mod:`!pipes`, :mod:`!sndhdr`, :mod:`!spwd`,
  :mod:`!sunau`, :mod:`!telnetlib`, :mod:`!uu` and :mod:`!xdrlib`.

* :pep:`602` ("Annual Release Cycle for Python") has been updated:

  * Python 3.9 - 3.12 have one and a half years of full support,
    followed by three and a half years of security fixes.
  * Python 3.13 and later have two years of full support,
    followed by three years of security fixes.


New Features
============



Other Language Changes
======================

* Allow the *count* argument of :meth:`str.replace` to be a keyword.
  (Contributed by Hugo van Kemenade in :gh:`106487`.)

* Compiler now strip indents from docstrings.
  This will reduce the size of :term:`bytecode cache <bytecode>` (e.g. ``.pyc`` file).
  For example, cache file size for ``sqlalchemy.orm.session`` in SQLAlchemy 2.0
  is reduced by about 5%.
  This change will affect tools using docstrings, like :mod:`doctest`.
  (Contributed by Inada Naoki in :gh:`81283`.)

* The :func:`compile` built-in can now accept a new flag,
  ``ast.PyCF_OPTIMIZED_AST``, which is similar to ``ast.PyCF_ONLY_AST``
  except that the returned ``AST`` is optimized according to the value
  of the ``optimize`` argument.
  (Contributed by Irit Katriel in :gh:`108113`).

* :mod:`multiprocessing`, :mod:`concurrent.futures`, :mod:`compileall`:
  Replace :func:`os.cpu_count` with :func:`os.process_cpu_count` to select the
  default number of worker threads and processes. Get the CPU affinity
  if supported.
  (Contributed by Victor Stinner in :gh:`109649`.)

* :func:`os.path.realpath` now resolves MS-DOS style file names even if
  the file is not accessible.
  (Contributed by Moonsik Park in :gh:`82367`.)

* Fixed a bug where a :keyword:`global` declaration in an :keyword:`except` block
  is rejected when the global is used in the :keyword:`else` block.
  (Contributed by Irit Katriel in :gh:`111123`.)

* Added a new environment variable :envvar:`PYTHON_FROZEN_MODULES`. It
  determines whether or not frozen modules are ignored by the import machinery,
  equivalent of the :option:`-X frozen_modules <-X>` command-line option.
  (Contributed by Yilei Yang in :gh:`111374`.)

New Modules
===========

* None yet.


Improved Modules
================

ast
---

* :func:`ast.parse` now accepts an optional argument ``optimize``
  which is passed on to the :func:`compile` built-in. This makes it
  possible to obtain an optimized ``AST``.
  (Contributed by Irit Katriel in :gh:`108113`).

array
-----

* Add ``'w'`` type code (``Py_UCS4``) that can be used for Unicode strings.
  It can be used instead of ``'u'`` type code, which is deprecated.
  (Contributed by Inada Naoki in :gh:`80480`.)

asyncio
-------

* :meth:`asyncio.loop.create_unix_server` will now automatically remove
  the Unix socket when the server is closed.
  (Contributed by Pierre Ossman in :gh:`111246`.)

copy
----

* Add :func:`copy.replace` function which allows to create a modified copy of
  an object, which is especially useful for immutable objects.
  It supports named tuples created with the factory function
  :func:`collections.namedtuple`, :class:`~dataclasses.dataclass` instances,
  various :mod:`datetime` objects, :class:`~inspect.Signature` objects,
  :class:`~inspect.Parameter` objects, :ref:`code object <code-objects>`, and
  any user classes which define the :meth:`!__replace__` method.
  (Contributed by Serhiy Storchaka in :gh:`108751`.)

dbm
---

* Add :meth:`dbm.gnu.gdbm.clear` and :meth:`dbm.ndbm.ndbm.clear`  methods that remove all items
  from the database.
  (Contributed by Donghee Na in :gh:`107122`.)

doctest
-------

* The :meth:`doctest.DocTestRunner.run` method now counts the number of skipped
  tests. Add :attr:`doctest.DocTestRunner.skips` and
  :attr:`doctest.TestResults.skipped` attributes.
  (Contributed by Victor Stinner in :gh:`108794`.)

io
--

The :class:`io.IOBase` finalizer now logs the ``close()`` method errors with
:data:`sys.unraisablehook`. Previously, errors were ignored silently by default,
and only logged in :ref:`Python Development Mode <devmode>` or on :ref:`Python
built on debug mode <debug-build>`.
(Contributed by Victor Stinner in :gh:`62948`.)

ipaddress
---------

* Add the :attr:`ipaddress.IPv4Address.ipv6_mapped` property, which returns the IPv4-mapped IPv6 address.
  (Contributed by Charles Machalow in :gh:`109466`.)

opcode
------

* Move ``opcode.ENABLE_SPECIALIZATION`` to ``_opcode.ENABLE_SPECIALIZATION``.
  This field was added in 3.12, it was never documented and is not intended for
  external usage. (Contributed by Irit Katriel in :gh:`105481`.)

* Removed ``opcode.is_pseudo``, ``opcode.MIN_PSEUDO_OPCODE`` and
  ``opcode.MAX_PSEUDO_OPCODE``, which were added in 3.12, were never
  documented or exposed through ``dis``, and were not intended to be
  used externally.

os
--

* Add :func:`os.process_cpu_count` function to get the number of logical CPUs
  usable by the calling thread of the current process.
  (Contributed by Victor Stinner in :gh:`109649`.)

* Add a low level interface for Linux's timer notification file descriptors
  via :func:`os.timerfd_create`,
  :func:`os.timerfd_settime`, :func:`os.timerfd_settime_ns`,
  :func:`os.timerfd_gettime`, and :func:`os.timerfd_gettime_ns`,
  :const:`os.TFD_NONBLOCK`, :const:`os.TFD_CLOEXEC`,
  :const:`os.TFD_TIMER_ABSTIME`, and :const:`os.TFD_TIMER_CANCEL_ON_SET`
  (Contributed by Masaru Tsuchiyama in :gh:`108277`.)

* :func:`os.cpu_count` and :func:`os.process_cpu_count` can be overridden through
  the new environment variable :envvar:`PYTHON_CPU_COUNT` or the new command-line option
  :option:`-X cpu_count <-X>`. This option is useful for users who need to limit
  CPU resources of a container system without having to modify the container (application code).
  (Contributed by Donghee Na in :gh:`109595`)

pathlib
-------

* Add :exc:`pathlib.UnsupportedOperation`, which is raised instead of
  :exc:`NotImplementedError` when a path operation isn't supported.
  (Contributed by Barney Gale in :gh:`89812`.)

* Add :meth:`pathlib.Path.from_uri`, a new constructor to create a :class:`pathlib.Path`
  object from a 'file' URI (``file:/``).
  (Contributed by Barney Gale in :gh:`107465`.)

* Add support for recursive wildcards in :meth:`pathlib.PurePath.match`.
  (Contributed by Barney Gale in :gh:`73435`.)

* Add *follow_symlinks* keyword-only argument to :meth:`pathlib.Path.glob`,
  :meth:`~pathlib.Path.rglob`, :meth:`~pathlib.Path.is_file`, and
  :meth:`~pathlib.Path.is_dir`.
  (Contributed by Barney Gale in :gh:`77609` and :gh:`105793`.)

pdb
---

* Add ability to move between chained exceptions during post mortem debugging in :func:`~pdb.pm` using
  the new ``exceptions [exc_number]`` command for Pdb. (Contributed by Matthias
  Bussonnier in :gh:`106676`.)

* Expressions/Statements whose prefix is a pdb command are now correctly
  identified and executed.
  (Contributed by Tian Gao in :gh:`108464`.)

sqlite3
-------

* A :exc:`ResourceWarning` is now emitted if a :class:`sqlite3.Connection`
  object is not :meth:`closed <sqlite3.Connection.close>` explicitly.
  (Contributed by Erlend E. Aasland in :gh:`105539`.)

tkinter
-------

* Add :mod:`tkinter` widget methods:
  :meth:`!tk_busy_hold`, :meth:`!tk_busy_configure`,
  :meth:`!tk_busy_cget`, :meth:`!tk_busy_forget`,
  :meth:`!tk_busy_current`, and :meth:`!tk_busy_status`.
  (Contributed by Miguel, klappnase and Serhiy Storchaka in :gh:`72684`.)

traceback
---------

* Add *show_group* parameter to :func:`traceback.TracebackException.format_exception_only`
  to format the nested exceptions of a :exc:`BaseExceptionGroup` instance, recursively.
  (Contributed by Irit Katriel in :gh:`105292`.)

typing
------

* Add :func:`typing.get_protocol_members` to return the set of members
  defining a :class:`typing.Protocol`. Add :func:`typing.is_protocol` to
  check whether a class is a :class:`typing.Protocol`. (Contributed by Jelle Zijlstra in
  :gh:`104873`.)

venv
----

* Add support for adding source control management (SCM) ignore files to a
  virtual environment's directory. By default, Git is supported. This is
  implemented as opt-in via the API which can be extended to support other SCMs
  (:class:`venv.EnvBuilder` and :func:`venv.create`), and opt-out via the CLI
  (using ``--without-scm-ignore-files``). (Contributed by Brett Cannon in
  :gh:`108125`.)

Optimizations
=============

* :func:`textwrap.indent` is now ~30% faster than before for large input.
  (Contributed by Inada Naoki in :gh:`107369`.)


Deprecated
==========

* :mod:`array`: :mod:`array`'s ``'u'`` format code, deprecated in docs since Python 3.3,
  emits :exc:`DeprecationWarning` since 3.13
  and will be removed in Python 3.16.
  Use the ``'w'`` format code instead.
  (contributed by Hugo van Kemenade in :gh:`80480`)

* :mod:`ctypes`: Deprecate undocumented :func:`!ctypes.SetPointerType`
  and :func:`!ctypes.ARRAY` functions.
  Replace ``ctypes.ARRAY(item_type, size)`` with ``item_type * size``.
  (Contributed by Victor Stinner in :gh:`105733`.)

* :mod:`getopt` and :mod:`optparse` modules: They are now
  :term:`soft deprecated`: the :mod:`argparse` should be used for new projects.
  Previously, the :mod:`optparse` module was already deprecated, its removal
  was not scheduled, and no warnings was emitted: so there is no change in
  practice.
  (Contributed by Victor Stinner in :gh:`106535`.)

* :mod:`http.server`: :class:`http.server.CGIHTTPRequestHandler` now emits a
  :exc:`DeprecationWarning` as it will be removed in 3.15.  Process based CGI
  http servers have been out of favor for a very long time.  This code was
  outdated, unmaintained, and rarely used.  It has a high potential for both
  security and functionality bugs.  This includes removal of the ``--cgi``
  flag to the ``python -m http.server`` command line in 3.15.

* :mod:`typing`:

  * Creating a :class:`typing.NamedTuple` class using keyword arguments to denote
    the fields (``NT = NamedTuple("NT", x=int, y=int)``) is deprecated, and will
    be disallowed in Python 3.15. Use the class-based syntax or the functional
    syntax instead. (Contributed by Alex Waygood in :gh:`105566`.)

  * When using the functional syntax to create a :class:`typing.NamedTuple`
    class or a :class:`typing.TypedDict` class, failing to pass a value to the
    'fields' parameter (``NT = NamedTuple("NT")`` or ``TD = TypedDict("TD")``) is
    deprecated. Passing ``None`` to the 'fields' parameter
    (``NT = NamedTuple("NT", None)`` or ``TD = TypedDict("TD", None)``) is also
    deprecated. Both will be disallowed in Python 3.15. To create a NamedTuple
    class with 0 fields, use ``class NT(NamedTuple): pass`` or
    ``NT = NamedTuple("NT", [])``. To create a TypedDict class with 0 fields, use
    ``class TD(TypedDict): pass`` or ``TD = TypedDict("TD", {})``.
    (Contributed by Alex Waygood in :gh:`105566` and :gh:`105570`.)

  * :func:`typing.no_type_check_decorator` is deprecated, and scheduled for
    removal in Python 3.15. After eight years in the :mod:`typing` module, it
    has yet to be supported by any major type checkers.
    (Contributed by Alex Waygood in :gh:`106309`.)

  * :data:`typing.AnyStr` is deprecated. In Python 3.16, it will be removed from
    ``typing.__all__``, and a :exc:`DeprecationWarning` will be emitted when it
    is imported or accessed. It will be removed entirely in Python 3.18. Use
    the new :ref:`type parameter syntax <type-params>` instead.
    (Contributed by Michael The in :gh:`107116`.)

* :mod:`wave`: Deprecate the ``getmark()``, ``setmark()`` and ``getmarkers()``
  methods of the :class:`wave.Wave_read` and :class:`wave.Wave_write` classes.
  They will be removed in Python 3.15.
  (Contributed by Victor Stinner in :gh:`105096`.)

* Passing more than one positional argument to :func:`sqlite3.connect` and the
  :class:`sqlite3.Connection` constructor is deprecated. The remaining
  parameters will become keyword-only in Python 3.15.

  Deprecate passing name, number of arguments, and the callable as keyword
  arguments, for the following :class:`sqlite3.Connection` APIs:

  * :meth:`~sqlite3.Connection.create_function`
  * :meth:`~sqlite3.Connection.create_aggregate`

  Deprecate passing the callback callable by keyword for the following
  :class:`sqlite3.Connection` APIs:

  * :meth:`~sqlite3.Connection.set_authorizer`
  * :meth:`~sqlite3.Connection.set_progress_handler`
  * :meth:`~sqlite3.Connection.set_trace_callback`

  The affected parameters will become positional-only in Python 3.15.

  (Contributed by Erlend E. Aasland in :gh:`107948` and :gh:`108278`.)

* The ``dis.HAVE_ARGUMENT`` separator is deprecated. Check membership
  in :data:`~dis.hasarg` instead.
  (Contributed by Irit Katriel in :gh:`109319`.)

* Deprecate non-standard format specifier "N" for :class:`decimal.Decimal`.
  It was not documented and only supported in the C implementation.
  (Contributed by Serhiy Storchaka in :gh:`89902`.)

* Emit deprecation warning for non-integer numbers in :mod:`gettext` functions
  and methods that consider plural forms even if the translation was not found.
  (Contributed by Serhiy Storchaka in :gh:`88434`.)

* Calling :meth:`frame.clear` on a suspended frame raises :exc:`RuntimeError`
  (as has always been the case for an executing frame).
  (Contributed by Irit Katriel in :gh:`79932`.)

* Assignment to a function's ``__code__`` attribute where the new code
  object's type does not match the function's type, is deprecated. The
  different types are: plain function, generator, async generator and
  coroutine.
  (Contributed by Irit Katriel in :gh:`81137`.)


Pending Removal in Python 3.14
------------------------------

* :mod:`argparse`: The *type*, *choices*, and *metavar* parameters
  of :class:`!argparse.BooleanOptionalAction` are deprecated
  and will be removed in 3.14.
  (Contributed by Nikita Sobolev in :gh:`92248`.)

* :mod:`ast`: The following features have been deprecated in documentation
  since Python 3.8, now cause a :exc:`DeprecationWarning` to be emitted at
  runtime when they are accessed or used, and will be removed in Python 3.14:

  * :class:`!ast.Num`
  * :class:`!ast.Str`
  * :class:`!ast.Bytes`
  * :class:`!ast.NameConstant`
  * :class:`!ast.Ellipsis`

  Use :class:`ast.Constant` instead.
  (Contributed by Serhiy Storchaka in :gh:`90953`.)

* :mod:`collections.abc`: Deprecated :class:`~collections.abc.ByteString`.
  Prefer :class:`!Sequence` or :class:`~collections.abc.Buffer`.
  For use in typing, prefer a union, like ``bytes | bytearray``,
  or :class:`collections.abc.Buffer`.
  (Contributed by Shantanu Jain in :gh:`91896`.)

* :mod:`email`: Deprecated the *isdst* parameter in :func:`email.utils.localtime`.
  (Contributed by Alan Williams in :gh:`72346`.)

* :mod:`importlib`: ``__package__`` and ``__cached__`` will cease to be set or
  taken into consideration by the import system (:gh:`97879`).

* :mod:`importlib.abc` deprecated classes:

  * :class:`!importlib.abc.ResourceReader`
  * :class:`!importlib.abc.Traversable`
  * :class:`!importlib.abc.TraversableResources`

  Use :mod:`importlib.resources.abc` classes instead:

  * :class:`importlib.resources.abc.Traversable`
  * :class:`importlib.resources.abc.TraversableResources`

  (Contributed by Jason R. Coombs and Hugo van Kemenade in :gh:`93963`.)

* :mod:`itertools` had undocumented, inefficient, historically buggy,
  and inconsistent support for copy, deepcopy, and pickle operations.
  This will be removed in 3.14 for a significant reduction in code
  volume and maintenance burden.
  (Contributed by Raymond Hettinger in :gh:`101588`.)

* :mod:`multiprocessing`: The default start method will change to a safer one on
  Linux, BSDs, and other non-macOS POSIX platforms where ``'fork'`` is currently
  the default (:gh:`84559`). Adding a runtime warning about this was deemed too
  disruptive as the majority of code is not expected to care. Use the
  :func:`~multiprocessing.get_context` or
  :func:`~multiprocessing.set_start_method` APIs to explicitly specify when
  your code *requires* ``'fork'``.  See :ref:`multiprocessing-start-methods`.

* :mod:`pathlib`: :meth:`~pathlib.PurePath.is_relative_to`,
  :meth:`~pathlib.PurePath.relative_to`: passing additional arguments is
  deprecated.

* :func:`pkgutil.find_loader` and :func:`pkgutil.get_loader`
  now raise :exc:`DeprecationWarning`;
  use :func:`importlib.util.find_spec` instead.
  (Contributed by Nikita Sobolev in :gh:`97850`.)

* :mod:`pty`:

  * ``master_open()``: use :func:`pty.openpty`.
  * ``slave_open()``: use :func:`pty.openpty`.

* :func:`shutil.rmtree` *onerror* parameter is deprecated in 3.12,
  and will be removed in 3.14: use the *onexc* parameter instead.

* :mod:`sqlite3`:

  * :data:`~sqlite3.version` and :data:`~sqlite3.version_info`.

  * :meth:`~sqlite3.Cursor.execute` and :meth:`~sqlite3.Cursor.executemany`
    if :ref:`named placeholders <sqlite3-placeholders>` are used and
    *parameters* is a sequence instead of a :class:`dict`.

  * date and datetime adapter, date and timestamp converter:
    see the :mod:`sqlite3` documentation for suggested replacement recipes.

* :class:`types.CodeType`: Accessing ``co_lnotab`` was deprecated in :pep:`626`
  since 3.10 and was planned to be removed in 3.12,
  but it only got a proper :exc:`DeprecationWarning` in 3.12.
  May be removed in 3.14.
  (Contributed by Nikita Sobolev in :gh:`101866`.)

* :mod:`typing`: :class:`~typing.ByteString`, deprecated since Python 3.9,
  now causes a :exc:`DeprecationWarning` to be emitted when it is used.

* :class:`!urllib.parse.Quoter` is deprecated: it was not intended to be a
  public API.
  (Contributed by Gregory P. Smith in :gh:`88168`.)

* :mod:`xml.etree.ElementTree`: Testing the truth value of an
  :class:`~xml.etree.ElementTree.Element` is deprecated and will raise an
  exception in Python 3.14.

Pending Removal in Python 3.15
------------------------------

* :class:`http.server.CGIHTTPRequestHandler` will be removed along with its
  related ``--cgi`` flag to ``python -m http.server``.  It was obsolete and
  rarely used.  No direct replacement exists.  *Anything* is better than CGI
  to interface a web server with a request handler.

* :class:`locale`: :func:`locale.getdefaultlocale` was deprecated in Python 3.11
  and originally planned for removal in Python 3.13 (:gh:`90817`),
  but removal has been postponed to Python 3.15.
  Use :func:`locale.setlocale()`, :func:`locale.getencoding()` and
  :func:`locale.getlocale()` instead.
  (Contributed by Hugo van Kemenade in :gh:`111187`.)

* :class:`typing.NamedTuple`:

  * The undocumented keyword argument syntax for creating NamedTuple classes
    (``NT = NamedTuple("NT", x=int)``) is deprecated, and will be disallowed in
    3.15. Use the class-based syntax or the functional syntax instead.

  * When using the functional syntax to create a NamedTuple class, failing to
    pass a value to the 'fields' parameter (``NT = NamedTuple("NT")``) is
    deprecated. Passing ``None`` to the 'fields' parameter
    (``NT = NamedTuple("NT", None)``) is also deprecated. Both will be
    disallowed in Python 3.15. To create a NamedTuple class with 0 fields, use
    ``class NT(NamedTuple): pass`` or ``NT = NamedTuple("NT", [])``.

* :class:`typing.TypedDict`: When using the functional syntax to create a
  TypedDict class, failing to pass a value to the 'fields' parameter (``TD =
  TypedDict("TD")``) is deprecated. Passing ``None`` to the 'fields' parameter
  (``TD = TypedDict("TD", None)``) is also deprecated. Both will be disallowed
  in Python 3.15. To create a TypedDict class with 0 fields, use ``class
  TD(TypedDict): pass`` or ``TD = TypedDict("TD", {})``.

* :mod:`wave`: Deprecate the ``getmark()``, ``setmark()`` and ``getmarkers()``
  methods of the :class:`wave.Wave_read` and :class:`wave.Wave_write` classes.
  They will be removed in Python 3.15.
  (Contributed by Victor Stinner in :gh:`105096`.)

* Passing any arguments to :func:`threading.RLock` is now deprecated.
  C version allows any numbers of args and kwargs,
  but they are just ignored. Python version does not allow any arguments.
  All arguments will be removed from :func:`threading.RLock` in Python 3.15.
  (Contributed by Nikita Sobolev in :gh:`102029`.)

Pending Removal in Python 3.16
------------------------------

* :class:`array.array` ``'u'`` type (:c:type:`wchar_t`):
  use the ``'w'`` type instead (``Py_UCS4``).

Pending Removal in Future Versions
----------------------------------

The following APIs were deprecated in earlier Python versions and will be removed,
although there is currently no date scheduled for their removal.

* :mod:`argparse`: Nesting argument groups and nesting mutually exclusive
  groups are deprecated.

* :mod:`builtins`:

  * ``~bool``, bitwise inversion on bool.
  * ``bool(NotImplemented)``.
  * Generators: ``throw(type, exc, tb)`` and ``athrow(type, exc, tb)``
    signature is deprecated: use ``throw(exc)`` and ``athrow(exc)`` instead,
    the single argument signature.
  * Currently Python accepts numeric literals immediately followed by keywords,
    for example ``0in x``, ``1or x``, ``0if 1else 2``.  It allows confusing and
    ambiguous expressions like ``[0x1for x in y]`` (which can be interpreted as
    ``[0x1 for x in y]`` or ``[0x1f or x in y]``).  A syntax warning is raised
    if the numeric literal is immediately followed by one of keywords
    :keyword:`and`, :keyword:`else`, :keyword:`for`, :keyword:`if`,
    :keyword:`in`, :keyword:`is` and :keyword:`or`.  In a future release it
    will be changed to a syntax error. (:gh:`87999`)
  * Support for ``__index__()`` and ``__int__()`` method returning non-int type:
    these methods will be required to return an instance of a strict subclass of
    :class:`int`.
  * Support for ``__float__()`` method returning a strict subclass of
    :class:`float`: these methods will be required to return an instance of
    :class:`float`.
  * Support for ``__complex__()`` method returning a strict subclass of
    :class:`complex`: these methods will be required to return an instance of
    :class:`complex`.
  * Delegation of ``int()`` to ``__trunc__()`` method.

* :mod:`calendar`: ``calendar.January`` and ``calendar.February`` constants are
  deprecated and replaced by :data:`calendar.JANUARY` and
  :data:`calendar.FEBRUARY`.
  (Contributed by Prince Roshan in :gh:`103636`.)

* :mod:`datetime`:

  * :meth:`~datetime.datetime.utcnow`:
    use ``datetime.datetime.now(tz=datetime.UTC)``.
  * :meth:`~datetime.datetime.utcfromtimestamp`:
    use ``datetime.datetime.fromtimestamp(timestamp, tz=datetime.UTC)``.

* :mod:`gettext`: Plural value must be an integer.

* :mod:`importlib`:

  * ``load_module()`` method: use ``exec_module()`` instead.
  * :func:`~importlib.util.cache_from_source` *debug_override* parameter is
    deprecated: use the *optimization* parameter instead.

* :mod:`importlib.metadata`:

  * ``EntryPoints`` tuple interface.
  * Implicit ``None`` on return values.

* :mod:`mailbox`: Use of StringIO input and text mode is deprecated, use
  BytesIO and binary mode instead.

* :mod:`os`: Calling :func:`os.register_at_fork` in multi-threaded process.

* :class:`!pydoc.ErrorDuringImport`: A tuple value for *exc_info* parameter is
  deprecated, use an exception instance.

* :mod:`re`: More strict rules are now applied for numerical group references
  and group names in regular expressions.  Only sequence of ASCII digits is now
  accepted as a numerical reference.  The group name in bytes patterns and
  replacement strings can now only contain ASCII letters and digits and
  underscore.
  (Contributed by Serhiy Storchaka in :gh:`91760`.)

* :mod:`ssl` options and protocols:

  * :class:`ssl.SSLContext` without protocol argument is deprecated.
  * :class:`ssl.SSLContext`: :meth:`~ssl.SSLContext.set_npn_protocols` and
    :meth:`!~ssl.SSLContext.selected_npn_protocol` are deprecated: use ALPN
    instead.
  * ``ssl.OP_NO_SSL*`` options
  * ``ssl.OP_NO_TLS*`` options
  * ``ssl.PROTOCOL_SSLv3``
  * ``ssl.PROTOCOL_TLS``
  * ``ssl.PROTOCOL_TLSv1``
  * ``ssl.PROTOCOL_TLSv1_1``
  * ``ssl.PROTOCOL_TLSv1_2``
  * ``ssl.TLSVersion.SSLv3``
  * ``ssl.TLSVersion.TLSv1``
  * ``ssl.TLSVersion.TLSv1_1``

* :mod:`!sre_compile`, :mod:`!sre_constants` and :mod:`!sre_parse` modules.

* ``types.CodeType.co_lnotab``: use the ``co_lines`` attribute instead.

* :class:`typing.Text` (:gh:`92332`).

* :func:`sysconfig.is_python_build` *check_home* parameter is deprecated and
  ignored.

* :mod:`threading` methods:

  * :meth:`!threading.Condition.notifyAll`: use :meth:`~threading.Condition.notify_all`.
  * :meth:`!threading.Event.isSet`: use :meth:`~threading.Event.is_set`.
  * :meth:`!threading.Thread.isDaemon`, :meth:`threading.Thread.setDaemon`:
    use :attr:`threading.Thread.daemon` attribute.
  * :meth:`!threading.Thread.getName`, :meth:`threading.Thread.setName`:
    use :attr:`threading.Thread.name` attribute.
  * :meth:`!threading.currentThread`: use :meth:`threading.current_thread`.
  * :meth:`!threading.activeCount`: use :meth:`threading.active_count`.

* :class:`unittest.IsolatedAsyncioTestCase`: it is deprecated to return a value
  that is not None from a test case.

* :mod:`urllib.request`: :class:`~urllib.request.URLopener` and
  :class:`~urllib.request.FancyURLopener` style of invoking requests is
  deprecated. Use newer :func:`~urllib.request.urlopen` functions and methods.

* :func:`!urllib.parse.to_bytes`.

* :mod:`urllib.parse` deprecated functions: :func:`~urllib.parse.urlparse` instead

  * ``splitattr()``
  * ``splithost()``
  * ``splitnport()``
  * ``splitpasswd()``
  * ``splitport()``
  * ``splitquery()``
  * ``splittag()``
  * ``splittype()``
  * ``splituser()``
  * ``splitvalue()``

* :mod:`wsgiref`: ``SimpleHandler.stdout.write()`` should not do partial
  writes.

* :meth:`zipimport.zipimporter.load_module` is deprecated:
  use :meth:`~zipimport.zipimporter.exec_module` instead.


Removed
=======

.. _whatsnew313-pep594:

PEP 594: dead batteries
-----------------------

* :pep:`594` removed 19 modules from the standard library,
  deprecated in Python 3.11:

  * :mod:`!aifc`.
    (Contributed by Victor Stinner in :gh:`104773`.)

  * :mod:`!audioop`.
    (Contributed by Victor Stinner in :gh:`104773`.)

  * :mod:`!chunk`.
    (Contributed by Victor Stinner in :gh:`104773`.)

  * :mod:`!cgi` and :mod:`!cgitb`.

    * ``cgi.FieldStorage`` can typically be replaced with
      :func:`urllib.parse.parse_qsl` for ``GET`` and ``HEAD`` requests,
      and the :mod:`email.message` module or `multipart
      <https://pypi.org/project/multipart/>`__ PyPI project for ``POST`` and
      ``PUT``.

    * ``cgi.parse()`` can be replaced by calling :func:`urllib.parse.parse_qs`
      directly on the desired query string, except for ``multipart/form-data``
      input, which can be handled as described for ``cgi.parse_multipart()``.

    * ``cgi.parse_header()`` can be replaced with the functionality in the
      :mod:`email` package, which implements the same MIME RFCs. For example,
      with :class:`email.message.EmailMessage`::

          from email.message import EmailMessage
          msg = EmailMessage()
          msg['content-type'] = 'application/json; charset="utf8"'
          main, params = msg.get_content_type(), msg['content-type'].params

    * ``cgi.parse_multipart()`` can be replaced with the functionality in the
      :mod:`email` package (e.g. :class:`email.message.EmailMessage` and
      :class:`email.message.Message`) which implements the same MIME RFCs, or
      with the `multipart <https://pypi.org/project/multipart/>`__ PyPI project.

    (Contributed by Victor Stinner in :gh:`104773`.)

  * :mod:`!crypt` module and its private :mod:`!_crypt` extension.
    The :mod:`hashlib` module is a potential replacement for certain use cases.
    Otherwise, the following PyPI projects can be used:

    * `bcrypt <https://pypi.org/project/bcrypt/>`_:
      Modern password hashing for your software and your servers.
    * `passlib <https://pypi.org/project/passlib/>`_:
      Comprehensive password hashing framework supporting over 30 schemes.
    * `argon2-cffi <https://pypi.org/project/argon2-cffi/>`_:
      The secure Argon2 password hashing algorithm.
    * `legacycrypt <https://pypi.org/project/legacycrypt/>`_:
      Wrapper to the POSIX crypt library call and associated functionality.

    (Contributed by Victor Stinner in :gh:`104773`.)

  * :mod:`!imghdr`: use the projects
    `filetype <https://pypi.org/project/filetype/>`_,
    `puremagic <https://pypi.org/project/puremagic/>`_,
    or `python-magic <https://pypi.org/project/python-magic/>`_ instead.
    (Contributed by Victor Stinner in :gh:`104773`.)

  * :mod:`!mailcap`.
    The :mod:`mimetypes` module provides an alternative.
    (Contributed by Victor Stinner in :gh:`104773`.)

  * :mod:`!msilib`.
    (Contributed by Zachary Ware in :gh:`104773`.)

  * :mod:`!nis`.
    (Contributed by Victor Stinner in :gh:`104773`.)

  * :mod:`!nntplib`:
    the `PyPI nntplib project <https://pypi.org/project/nntplib/>`_
    can be used instead.
    (Contributed by Victor Stinner in :gh:`104773`.)

  * :mod:`!ossaudiodev`: use the
    `pygame project <https://www.pygame.org/>`_ for audio playback.
    (Contributed by Victor Stinner in :gh:`104780`.)

  * :mod:`!pipes`: use the :mod:`subprocess` module instead.
    (Contributed by Victor Stinner in :gh:`104773`.)

  * :mod:`!sndhdr`: use the projects
    `filetype <https://pypi.org/project/filetype/>`_,
    `puremagic <https://pypi.org/project/puremagic/>`_, or
    `python-magic <https://pypi.org/project/python-magic/>`_ instead.
    (Contributed by Victor Stinner in :gh:`104773`.)

  * :mod:`!spwd`:
    the `python-pam project <https://pypi.org/project/python-pam/>`_
    can be used instead.
    (Contributed by Victor Stinner in :gh:`104773`.)

  * :mod:`!sunau`.
    (Contributed by Victor Stinner in :gh:`104773`.)

  * :mod:`!telnetlib`, use the projects
    `telnetlib3 <https://pypi.org/project/telnetlib3/>`_ or
    `Exscript <https://pypi.org/project/Exscript/>`_ instead.
    (Contributed by Victor Stinner in :gh:`104773`.)

  * :mod:`!uu`: the :mod:`base64` module is a modern alternative.
    (Contributed by Victor Stinner in :gh:`104773`.)

  * :mod:`!xdrlib`.
    (Contributed by Victor Stinner in :gh:`104773`.)

2to3
----

* Remove the ``2to3`` program and the :mod:`!lib2to3` module,
  deprecated in Python 3.11.
  (Contributed by Victor Stinner in :gh:`104780`.)

configparser
------------

* Remove the undocumented :class:`!configparser.LegacyInterpolation` class,
  deprecated in the docstring since Python 3.2,
  and with a deprecation warning since Python 3.11.
  (Contributed by Hugo van Kemenade in :gh:`104886`.)

importlib
---------

* Remove :mod:`importlib.resources` deprecated methods:

  * ``contents()``
  * ``is_resource()``
  * ``open_binary()``
  * ``open_text()``
  * ``path()``
  * ``read_binary()``
  * ``read_text()``

  Use :func:`importlib.resources.files()` instead.  Refer to `importlib-resources: Migrating from Legacy
  <https://importlib-resources.readthedocs.io/en/latest/using.html#migrating-from-legacy>`_
  for migration advice.
  (Contributed by Jason R. Coombs in :gh:`106532`.)

locale
------

* Remove ``locale.resetlocale()`` function deprecated in Python 3.11:
  use ``locale.setlocale(locale.LC_ALL, "")`` instead.
  (Contributed by Victor Stinner in :gh:`104783`.)

logging
-------

* :mod:`logging`: Remove undocumented and untested ``Logger.warn()`` and
  ``LoggerAdapter.warn()`` methods and ``logging.warn()`` function. Deprecated
  since Python 3.3, they were aliases to the :meth:`logging.Logger.warning`
  method, :meth:`!logging.LoggerAdapter.warning` method and
  :func:`logging.warning` function.
  (Contributed by Victor Stinner in :gh:`105376`.)

pathlib
-------

* Remove support for using :class:`pathlib.Path` objects as context managers.
  This functionality was deprecated and made a no-op in Python 3.9.

re
--

* Remove undocumented, never working, and deprecated ``re.template`` function
  and ``re.TEMPLATE`` flag (and ``re.T`` alias).
  (Contributed by Serhiy Storchaka and Nikita Sobolev in :gh:`105687`.)

tkinter
-------

* Remove the :mod:`!tkinter.tix` module, deprecated in Python 3.6.  The
  third-party Tix library which the module wrapped is unmaintained.
  (Contributed by Zachary Ware in :gh:`75552`.)

turtle
------

* Remove the :meth:`!turtle.RawTurtle.settiltangle` method,
  deprecated in docs since Python 3.1
  and with a deprecation warning since Python 3.11.
  (Contributed by Hugo van Kemenade in :gh:`104876`.)

typing
------

* Namespaces ``typing.io`` and ``typing.re``, deprecated in Python 3.8,
  are now removed. The items in those namespaces can be imported directly
  from :mod:`typing`. (Contributed by Sebastian Rittau in :gh:`92871`.)

* Remove support for the keyword-argument method of creating
  :class:`typing.TypedDict` types, deprecated in Python 3.11.
  (Contributed by Tomas Roun in :gh:`104786`.)

unittest
--------

* Removed the following :mod:`unittest` functions, deprecated in Python 3.11:

  * :func:`!unittest.findTestCases`
  * :func:`!unittest.makeSuite`
  * :func:`!unittest.getTestCaseNames`

  Use :class:`~unittest.TestLoader` methods instead:

  * :meth:`unittest.TestLoader.loadTestsFromModule`
  * :meth:`unittest.TestLoader.loadTestsFromTestCase`
  * :meth:`unittest.TestLoader.getTestCaseNames`

  (Contributed by Hugo van Kemenade in :gh:`104835`.)

* Remove the untested and undocumented :meth:`!unittest.TestProgram.usageExit`
  method, deprecated in Python 3.11.
  (Contributed by Hugo van Kemenade in :gh:`104992`.)

urllib
------

* Remove *cafile*, *capath* and *cadefault* parameters of the
  :func:`urllib.request.urlopen` function, deprecated in Python 3.6: use the
  *context* parameter instead. Please use
  :meth:`ssl.SSLContext.load_cert_chain` instead, or let
  :func:`ssl.create_default_context` select the system's trusted CA
  certificates for you.
  (Contributed by Victor Stinner in :gh:`105382`.)

webbrowser
----------

* Remove the untested and undocumented :mod:`webbrowser` :class:`!MacOSX` class,
  deprecated in Python 3.11.
  Use the :class:`!MacOSXOSAScript` class (introduced in Python 3.2) instead.
  (Contributed by Hugo van Kemenade in :gh:`104804`.)

* Remove deprecated ``webbrowser.MacOSXOSAScript._name`` attribute.
  Use :attr:`webbrowser.MacOSXOSAScript.name <webbrowser.controller.name>`
  attribute instead.
  (Contributed by Nikita Sobolev in :gh:`105546`.)

Others
------

* None yet

CPython bytecode changes
========================

* The oparg of ``YIELD_VALUE`` is now ``1`` if the yield is part of a
  yield-from or await, and ``0`` otherwise. The oparg of ``RESUME`` was
  changed to add a bit indicating whether the except-depth is 1, which
  is needed to optimize closing of generators.
  (Contributed by Irit Katriel in :gh:`111354`.)

Porting to Python 3.13
======================

This section lists previously described changes and other bugfixes
that may require changes to your code.

Changes in the Python API
-------------------------

* :meth:`!tkinter.Text.count` now always returns an integer if one or less
  counting options are specified.
  Previously it could return a single count as a 1-tuple, an integer (only if
  option ``"update"`` was specified) or ``None`` if no items found.
  The result is now the same if ``wantobjects`` is set to ``0``.
  (Contributed by Serhiy Storchaka in :gh:`97928`.)

* Functions :c:func:`PyDict_GetItem`, :c:func:`PyDict_GetItemString`,
  :c:func:`PyMapping_HasKey`, :c:func:`PyMapping_HasKeyString`,
  :c:func:`PyObject_HasAttr`, :c:func:`PyObject_HasAttrString`, and
  :c:func:`PySys_GetObject`, which clear all errors occurred during calling
  the function, report now them using :func:`sys.unraisablehook`.
  You can consider to replace these functions with other functions as
  recomended in the documentation.
  (Contributed by Serhiy Storchaka in :gh:`106672`.)


Build Changes
=============

* Autoconf 2.71 and aclocal 1.16.4 is now required to regenerate
  the :file:`configure` script.
  (Contributed by Christian Heimes in :gh:`89886`.)

* SQLite 3.15.2 or newer is required to build the :mod:`sqlite3` extension module.
  (Contributed by Erlend Aasland in :gh:`105875`.)

* Python built with :file:`configure` :option:`--with-trace-refs` (tracing
  references) is now ABI compatible with Python release build and
  :ref:`debug build <debug-build>`.
  (Contributed by Victor Stinner in :gh:`108634`.)

* Building CPython now requires a compiler with support for the C11 atomic
  library, GCC built-in atomic functions, or MSVC interlocked intrinsics.

* The ``errno``, ``md5``, ``resource``, ``winsound``, ``_ctypes_test``,
  ``_multiprocessing.posixshmem``, ``_scproxy``, ``_stat``,
  ``_testimportmultiple`` and ``_uuid`` C extensions are now built with the
  :ref:`limited C API <limited-c-api>`.
  (Contributed by Victor Stinner in :gh:`85283`.)


C API Changes
=============

New Features
------------

* You no longer have to define the ``PY_SSIZE_T_CLEAN`` macro before including
  :file:`Python.h` when using ``#`` formats in
  :ref:`format codes <arg-parsing-string-and-buffers>`.
  APIs accepting the format codes always use ``Py_ssize_t`` for ``#`` formats.
  (Contributed by Inada Naoki in :gh:`104922`.)

* Add :c:func:`PyImport_AddModuleRef`: similar to
  :c:func:`PyImport_AddModule`, but return a :term:`strong reference` instead
  of a :term:`borrowed reference`.
  (Contributed by Victor Stinner in :gh:`105922`.)

* Add :c:func:`PyWeakref_GetRef` function: similar to
  :c:func:`PyWeakref_GetObject` but returns a :term:`strong reference`, or
  ``NULL`` if the referent is no longer live.
  (Contributed by Victor Stinner in :gh:`105927`.)

* Add :c:func:`PyObject_GetOptionalAttr` and
  :c:func:`PyObject_GetOptionalAttrString`, variants of
  :c:func:`PyObject_GetAttr` and :c:func:`PyObject_GetAttrString` which
  don't raise :exc:`AttributeError` if the attribute is not found.
  These variants are more convenient and faster if the missing attribute
  should not be treated as a failure.
  (Contributed by Serhiy Storchaka in :gh:`106521`.)

* Add :c:func:`PyMapping_GetOptionalItem` and
  :c:func:`PyMapping_GetOptionalItemString`: variants of
  :c:func:`PyObject_GetItem` and :c:func:`PyMapping_GetItemString` which don't
  raise :exc:`KeyError` if the key is not found.
  These variants are more convenient and faster if the missing key should not
  be treated as a failure.
  (Contributed by Serhiy Storchaka in :gh:`106307`.)

* Add fixed variants of functions which silently ignore errors:

  - :c:func:`PyObject_HasAttrWithError` replaces :c:func:`PyObject_HasAttr`.
  - :c:func:`PyObject_HasAttrStringWithError` replaces :c:func:`PyObject_HasAttrString`.
  - :c:func:`PyMapping_HasKeyWithError` replaces :c:func:`PyMapping_HasKey`.
  - :c:func:`PyMapping_HasKeyStringWithError` replaces :c:func:`PyMapping_HasKeyString`.

  New functions return not only ``1`` for true and ``0`` for false, but also
  ``-1`` for error.

  (Contributed by Serhiy Storchaka in :gh:`108511`.)

* If Python is built in :ref:`debug mode <debug-build>` or :option:`with
  assertions <--with-assertions>`, :c:func:`PyTuple_SET_ITEM` and
  :c:func:`PyList_SET_ITEM` now check the index argument with an assertion.
  (Contributed by Victor Stinner in :gh:`106168`.)

* Add :c:func:`PyModule_Add` function: similar to
  :c:func:`PyModule_AddObjectRef` and :c:func:`PyModule_AddObject` but
  always steals a reference to the value.
  (Contributed by Serhiy Storchaka in :gh:`86493`.)

* Added :c:func:`PyDict_GetItemRef` and :c:func:`PyDict_GetItemStringRef`
  functions: similar to :c:func:`PyDict_GetItemWithError` but returning a
  :term:`strong reference` instead of a :term:`borrowed reference`. Moreover,
  these functions return -1 on error and so checking ``PyErr_Occurred()`` is
  not needed.
  (Contributed by Victor Stinner in :gh:`106004`.)

* Added :c:func:`PyDict_ContainsString` function: same as
  :c:func:`PyDict_Contains`, but *key* is specified as a :c:expr:`const char*`
  UTF-8 encoded bytes string, rather than a :c:expr:`PyObject*`.
  (Contributed by Victor Stinner in :gh:`108314`.)

* Add :c:func:`Py_IsFinalizing` function: check if the main Python interpreter is
  :term:`shutting down <interpreter shutdown>`.
  (Contributed by Victor Stinner in :gh:`108014`.)

* Add :c:func:`PyLong_AsInt` function: similar to :c:func:`PyLong_AsLong`, but
  store the result in a C :c:expr:`int` instead of a C :c:expr:`long`.
  Previously, it was known as the private function :c:func:`!_PyLong_AsInt`
  (with an underscore prefix).
  (Contributed by Victor Stinner in :gh:`108014`.)

* Python built with :file:`configure` :option:`--with-trace-refs` (tracing
  references) now supports the :ref:`Limited API <limited-c-api>`.
  (Contributed by Victor Stinner in :gh:`108634`.)

* Add :c:func:`PyObject_VisitManagedDict` and
  :c:func:`PyObject_ClearManagedDict` functions which must be called by the
  traverse and clear functions of a type using
  :c:macro:`Py_TPFLAGS_MANAGED_DICT` flag.  The `pythoncapi-compat project
  <https://github.com/python/pythoncapi-compat/>`__ can be used to get these
  functions on Python 3.11 and 3.12.
  (Contributed by Victor Stinner in :gh:`107073`.)

* Add :c:func:`PyUnicode_EqualToUTF8AndSize` and :c:func:`PyUnicode_EqualToUTF8`
  functions: compare Unicode object with a :c:expr:`const char*` UTF-8 encoded
  string and return true (``1``) if they are equal, or false (``0``) otherwise.
  These functions do not raise exceptions.
  (Contributed by Serhiy Storchaka in :gh:`110289`.)

* Add :c:func:`PyThreadState_GetUnchecked()` function: similar to
  :c:func:`PyThreadState_Get()`, but don't kill the process with a fatal error
  if it is NULL. The caller is responsible to check if the result is NULL.
  Previously, the function was private and known as
  ``_PyThreadState_UncheckedGet()``.
  (Contributed by Victor Stinner in :gh:`108867`.)

* Add :c:func:`PySys_AuditTuple` function: similar to :c:func:`PySys_Audit`,
  but pass event arguments as a Python :class:`tuple` object.
  (Contributed by Victor Stinner in :gh:`85283`.)

* :c:func:`PyArg_ParseTupleAndKeywords` now supports non-ASCII keyword
  parameter names.
  (Contributed by Serhiy Storchaka in :gh:`110815`.)

* Add :c:func:`PyMem_RawMalloc`, :c:func:`PyMem_RawCalloc`,
  :c:func:`PyMem_RawRealloc` and :c:func:`PyMem_RawFree` to the limited C API
  (version 3.13).
  (Contributed by Victor Stinner in :gh:`85283`.)

* Add :c:func:`PySys_Audit` and :c:func:`PySys_AuditTuple` functions to the
  limited C API.
  (Contributed by Victor Stinner in :gh:`85283`.)

* Add :c:func:`PyErr_FormatUnraisable` function: similar to
  :c:func:`PyErr_WriteUnraisable`, but allow to customize the warning mesage.
  (Contributed by Serhiy Storchaka in :gh:`108082`.)


Porting to Python 3.13
----------------------

* ``Python.h`` no longer includes the ``<ieeefp.h>`` standard header. It was
  included for the ``finite()`` function which is now provided by the
  ``<math.h>`` header. It should now be included explicitly if needed. Remove
  also the ``HAVE_IEEEFP_H`` macro.
  (Contributed by Victor Stinner in :gh:`108765`.)

* ``Python.h`` no longer includes the ``<unistd.h>`` standard header file. If
  needed, it should now be included explicitly. For example, it provides the
  functions: ``read()``, ``write()``, ``close()``, ``isatty()``, ``lseek()``,
  ``getpid()``, ``getcwd()``, ``sysconf()``, ``getpagesize()``, ``alarm()`` and
  ``pause()``.
  As a consequence, ``_POSIX_SEMAPHORES`` and ``_POSIX_THREADS`` macros are no
  longer defined by ``Python.h``. The ``HAVE_UNISTD_H`` and ``HAVE_PTHREAD_H``
  macros defined by ``Python.h`` can be used to decide if ``<unistd.h>`` and
  ``<pthread.h>`` header files can be included.
  (Contributed by Victor Stinner in :gh:`108765`.)

* ``Python.h`` no longer includes these standard header files: ``<time.h>``,
  ``<sys/select.h>`` and ``<sys/time.h>``. If needed, they should now be
  included explicitly. For example, ``<time.h>`` provides the ``clock()`` and
  ``gmtime()`` functions, ``<sys/select.h>`` provides the ``select()``
  function, and ``<sys/time.h>`` provides the ``futimes()``, ``gettimeofday()``
  and ``setitimer()`` functions.
  (Contributed by Victor Stinner in :gh:`108765`.)

* ``Python.h`` no longer includes the ``<ctype.h>`` standard header file. If
  needed, it should now be included explicitly. For example, it provides
  ``isalpha()`` and ``tolower()`` functions which are locale dependent. Python
  provides locale independent functions, like :c:func:`!Py_ISALPHA` and
  :c:func:`!Py_TOLOWER`.
  (Contributed by Victor Stinner in :gh:`108765`.)

* If the :c:macro:`Py_LIMITED_API` macro is defined, :c:macro:`!Py_BUILD_CORE`,
  :c:macro:`!Py_BUILD_CORE_BUILTIN` and :c:macro:`!Py_BUILD_CORE_MODULE` macros
  are now undefined by ``<Python.h>``.
  (Contributed by Victor Stinner in :gh:`85283`.)

* The old trashcan macros ``Py_TRASHCAN_SAFE_BEGIN`` and ``Py_TRASHCAN_SAFE_END``
  were removed. They should be replaced by the new macros ``Py_TRASHCAN_BEGIN``
  and ``Py_TRASHCAN_END``.

  A tp_dealloc function that has the old macros, such as::

    static void
    mytype_dealloc(mytype *p)
    {
        PyObject_GC_UnTrack(p);
        Py_TRASHCAN_SAFE_BEGIN(p);
        ...
        Py_TRASHCAN_SAFE_END
    }

  should migrate to the new macros as follows::

    static void
    mytype_dealloc(mytype *p)
    {
        PyObject_GC_UnTrack(p);
        Py_TRASHCAN_BEGIN(p, mytype_dealloc)
        ...
        Py_TRASHCAN_END
    }

  Note that ``Py_TRASHCAN_BEGIN`` has a second argument which
  should be the deallocation function it is in.

* On Windows, ``Python.h`` no longer includes the ``<stddef.h>`` standard
  header file. If needed, it should now be included explicitly. For example, it
  provides ``offsetof()`` function, and ``size_t`` and ``ptrdiff_t`` types.
  Including ``<stddef.h>`` explicitly was already needed by all other
  platforms, the ``HAVE_STDDEF_H`` macro is only defined on Windows.
  (Contributed by Victor Stinner in :gh:`108765`.)


Deprecated
----------

* Passing optional arguments *maxsplit*, *count* and *flags* in module-level
  functions :func:`re.split`, :func:`re.sub` and :func:`re.subn` as positional
  arguments is now deprecated.
  In future Python versions these parameters will be
  :ref:`keyword-only <keyword-only_parameter>`.
  (Contributed by Serhiy Storchaka in :gh:`56166`.)

* Deprecate the old ``Py_UNICODE`` and ``PY_UNICODE_TYPE`` types: use directly
  the :c:type:`wchar_t` type instead. Since Python 3.3, ``Py_UNICODE`` and
  ``PY_UNICODE_TYPE`` are just aliases to :c:type:`wchar_t`.
  (Contributed by Victor Stinner in :gh:`105156`.)

* Deprecate old Python initialization functions:

  * :c:func:`PySys_ResetWarnOptions`:
    clear :data:`sys.warnoptions` and :data:`!warnings.filters` instead.
  * :c:func:`Py_GetExecPrefix`: get :data:`sys.exec_prefix` instead.
  * :c:func:`Py_GetPath`: get :data:`sys.path` instead.
  * :c:func:`Py_GetPrefix`: get :data:`sys.prefix` instead.
  * :c:func:`Py_GetProgramFullPath`: get :data:`sys.executable` instead.
  * :c:func:`Py_GetProgramName`: get :data:`sys.executable` instead.
  * :c:func:`Py_GetPythonHome`: get :c:member:`PyConfig.home` or
    :envvar:`PYTHONHOME` environment variable instead.

  Functions scheduled for removal in Python 3.15.
  (Contributed by Victor Stinner in :gh:`105145`.)

* Deprecate the :c:func:`PyImport_ImportModuleNoBlock` function which is just
  an alias to :c:func:`PyImport_ImportModule` since Python 3.3.
  Scheduled for removal in Python 3.15.
  (Contributed by Victor Stinner in :gh:`105396`.)

* Deprecate the :c:func:`PyWeakref_GetObject` and
  :c:func:`PyWeakref_GET_OBJECT` functions, which return a :term:`borrowed
  reference`: use the new :c:func:`PyWeakref_GetRef` function instead, it
  returns a :term:`strong reference`. The `pythoncapi-compat project
  <https://github.com/python/pythoncapi-compat/>`__ can be used to get
  :c:func:`PyWeakref_GetRef` on Python 3.12 and older.
  (Contributed by Victor Stinner in :gh:`105927`.)

Removed
-------

* Removed chained :class:`classmethod` descriptors (introduced in
  :issue:`19072`).  This can no longer be used to wrap other descriptors
  such as :class:`property`.  The core design of this feature was flawed
  and caused a number of downstream problems.  To "pass-through" a
  :class:`classmethod`, consider using the :attr:`!__wrapped__`
  attribute that was added in Python 3.10.  (Contributed by Raymond
  Hettinger in :gh:`89519`.)

* Remove many APIs (functions, macros, variables) with names prefixed by
  ``_Py`` or ``_PY`` (considered as private API). If your project is affected
  by one of these removals and you consider that the removed API should remain
  available, please open a new issue to request a public C API and
  add ``cc @vstinner`` to the issue to notify Victor Stinner.
  (Contributed by Victor Stinner in :gh:`106320`.)

* Remove functions deprecated in Python 3.9.

  * ``PyEval_CallObject()``, ``PyEval_CallObjectWithKeywords()``: use
    :c:func:`PyObject_CallNoArgs` or :c:func:`PyObject_Call` instead.
    Warning: :c:func:`PyObject_Call` positional arguments must be a
    :class:`tuple` and must not be *NULL*, keyword arguments must be a
    :class:`dict` or *NULL*, whereas removed functions checked arguments type
    and accepted *NULL* positional and keyword arguments.
    To replace ``PyEval_CallObjectWithKeywords(func, NULL, kwargs)`` with
    :c:func:`PyObject_Call`, pass an empty tuple as positional arguments using
    :c:func:`PyTuple_New(0) <PyTuple_New>`.
  * ``PyEval_CallFunction()``: use :c:func:`PyObject_CallFunction` instead.
  * ``PyEval_CallMethod()``: use :c:func:`PyObject_CallMethod` instead.
  * ``PyCFunction_Call()``: use :c:func:`PyObject_Call` instead.

  (Contributed by Victor Stinner in :gh:`105107`.)

* Remove old buffer protocols deprecated in Python 3.0. Use :ref:`bufferobjects` instead.

  * :c:func:`!PyObject_CheckReadBuffer`: Use :c:func:`PyObject_CheckBuffer` to
    test if the object supports the buffer protocol.
    Note that :c:func:`PyObject_CheckBuffer` doesn't guarantee that
    :c:func:`PyObject_GetBuffer` will succeed.
    To test if the object is actually readable, see the next example
    of :c:func:`PyObject_GetBuffer`.

  * :c:func:`!PyObject_AsCharBuffer`, :c:func:`!PyObject_AsReadBuffer`:
    :c:func:`PyObject_GetBuffer` and :c:func:`PyBuffer_Release` instead:

    .. code-block:: c

       Py_buffer view;
       if (PyObject_GetBuffer(obj, &view, PyBUF_SIMPLE) < 0) {
           return NULL;
       }
       // Use `view.buf` and `view.len` to read from the buffer.
       // You may need to cast buf as `(const char*)view.buf`.
       PyBuffer_Release(&view);

  * :c:func:`!PyObject_AsWriteBuffer`: Use
    :c:func:`PyObject_GetBuffer` and :c:func:`PyBuffer_Release` instead:

    .. code-block:: c

       Py_buffer view;
       if (PyObject_GetBuffer(obj, &view, PyBUF_WRITABLE) < 0) {
           return NULL;
       }
       // Use `view.buf` and `view.len` to write to the buffer.
       PyBuffer_Release(&view);

  (Contributed by Inada Naoki in :gh:`85275`.)

* Remove the following old functions to configure the Python initialization,
  deprecated in Python 3.11:

  * ``PySys_AddWarnOptionUnicode()``: use :c:member:`PyConfig.warnoptions` instead.
  * ``PySys_AddWarnOption()``: use :c:member:`PyConfig.warnoptions` instead.
  * ``PySys_AddXOption()``: use :c:member:`PyConfig.xoptions` instead.
  * ``PySys_HasWarnOptions()``: use :c:member:`PyConfig.xoptions` instead.
  * ``PySys_SetArgvEx()``: set :c:member:`PyConfig.argv` instead.
  * ``PySys_SetArgv()``: set :c:member:`PyConfig.argv` instead.
  * ``PySys_SetPath()``: set :c:member:`PyConfig.module_search_paths` instead.
  * ``Py_SetPath()``: set :c:member:`PyConfig.module_search_paths` instead.
  * ``Py_SetProgramName()``: set :c:member:`PyConfig.program_name` instead.
  * ``Py_SetPythonHome()``: set :c:member:`PyConfig.home` instead.
  * ``Py_SetStandardStreamEncoding()``: set :c:member:`PyConfig.stdio_encoding`
    instead, and set also maybe :c:member:`PyConfig.legacy_windows_stdio` (on
    Windows).
  * ``_Py_SetProgramFullPath()``: set :c:member:`PyConfig.executable` instead.

  Use the new :c:type:`PyConfig` API of the :ref:`Python Initialization
  Configuration <init-config>` instead (:pep:`587`), added to Python 3.8.
  (Contributed by Victor Stinner in :gh:`105145`.)

* Remove the old trashcan macros ``Py_TRASHCAN_SAFE_BEGIN`` and
  ``Py_TRASHCAN_SAFE_END``.  They should be replaced by the new macros
  ``Py_TRASHCAN_BEGIN`` and ``Py_TRASHCAN_END``.  The new macros were
  added in Python 3.8 and the old macros were deprecated in Python 3.11.
  (Contributed by Irit Katriel in :gh:`105111`.)

* Remove ``PyEval_InitThreads()`` and ``PyEval_ThreadsInitialized()``
  functions, deprecated in Python 3.9. Since Python 3.7, ``Py_Initialize()``
  always creates the GIL: calling ``PyEval_InitThreads()`` did nothing and
  ``PyEval_ThreadsInitialized()`` always returned non-zero.
  (Contributed by Victor Stinner in :gh:`105182`.)

* Remove ``PyEval_AcquireLock()`` and ``PyEval_ReleaseLock()`` functions,
  deprecated in Python 3.2. They didn't update the current thread state.
  They can be replaced with:

  * :c:func:`PyEval_SaveThread` and :c:func:`PyEval_RestoreThread`;
  * low-level :c:func:`PyEval_AcquireThread` and :c:func:`PyEval_RestoreThread`;
  * or :c:func:`PyGILState_Ensure` and :c:func:`PyGILState_Release`.

  (Contributed by Victor Stinner in :gh:`105182`.)

* Remove the old aliases to functions calling functions which were kept for
  backward compatibility with Python 3.8 provisional API:

  * ``_PyObject_CallMethodNoArgs()``: use ``PyObject_CallMethodNoArgs()``
  * ``_PyObject_CallMethodOneArg()``: use ``PyObject_CallMethodOneArg()``
  * ``_PyObject_CallOneArg()``: use ``PyObject_CallOneArg()``
  * ``_PyObject_FastCallDict()``: use ``PyObject_VectorcallDict()``
  * ``_PyObject_Vectorcall()``: use ``PyObject_Vectorcall()``
  * ``_PyObject_VectorcallMethod()``: use ``PyObject_VectorcallMethod()``
  * ``_PyVectorcall_Function()``: use ``PyVectorcall_Function()``

  Just remove the underscore prefix to update your code.
  (Contributed by Victor Stinner in :gh:`106084`.)

* Remove private ``_PyObject_FastCall()`` function:
  use ``PyObject_Vectorcall()`` which is available since Python 3.8
  (:pep:`590`).
  (Contributed by Victor Stinner in :gh:`106023`.)

* Remove ``cpython/pytime.h`` header file: it only contained private functions.
  (Contributed by Victor Stinner in :gh:`106316`.)

* Remove ``_PyInterpreterState_Get()`` alias to
  :c:func:`PyInterpreterState_Get()` which was kept for backward compatibility
  with Python 3.8. The `pythoncapi-compat project
  <https://github.com/python/pythoncapi-compat/>`__ can be used to get
  :c:func:`PyInterpreterState_Get()` on Python 3.8 and older.
  (Contributed by Victor Stinner in :gh:`106320`.)

* The :c:func:`PyModule_AddObject` function is now :term:`soft deprecated`:
  :c:func:`PyModule_Add` or :c:func:`PyModule_AddObjectRef` functions should
  be used instead.
  (Contributed by Serhiy Storchaka in :gh:`86493`.)

Pending Removal in Python 3.14
------------------------------

* Creating immutable types (:c:macro:`Py_TPFLAGS_IMMUTABLETYPE`) with mutable
  bases using the C API.
* Global configuration variables:

  * :c:var:`Py_DebugFlag`: use :c:member:`PyConfig.parser_debug`
  * :c:var:`Py_VerboseFlag`: use :c:member:`PyConfig.verbose`
  * :c:var:`Py_QuietFlag`: use :c:member:`PyConfig.quiet`
  * :c:var:`Py_InteractiveFlag`: use :c:member:`PyConfig.interactive`
  * :c:var:`Py_InspectFlag`: use :c:member:`PyConfig.inspect`
  * :c:var:`Py_OptimizeFlag`: use :c:member:`PyConfig.optimization_level`
  * :c:var:`Py_NoSiteFlag`: use :c:member:`PyConfig.site_import`
  * :c:var:`Py_BytesWarningFlag`: use :c:member:`PyConfig.bytes_warning`
  * :c:var:`Py_FrozenFlag`: use :c:member:`PyConfig.pathconfig_warnings`
  * :c:var:`Py_IgnoreEnvironmentFlag`: use :c:member:`PyConfig.use_environment`
  * :c:var:`Py_DontWriteBytecodeFlag`: use :c:member:`PyConfig.write_bytecode`
  * :c:var:`Py_NoUserSiteDirectory`: use :c:member:`PyConfig.user_site_directory`
  * :c:var:`Py_UnbufferedStdioFlag`: use :c:member:`PyConfig.buffered_stdio`
  * :c:var:`Py_HashRandomizationFlag`: use :c:member:`PyConfig.use_hash_seed`
    and :c:member:`PyConfig.hash_seed`
  * :c:var:`Py_IsolatedFlag`: use :c:member:`PyConfig.isolated`
  * :c:var:`Py_LegacyWindowsFSEncodingFlag`: use :c:member:`PyPreConfig.legacy_windows_fs_encoding`
  * :c:var:`Py_LegacyWindowsStdioFlag`: use :c:member:`PyConfig.legacy_windows_stdio`
  * :c:var:`!Py_FileSystemDefaultEncoding`: use :c:member:`PyConfig.filesystem_encoding`
  * :c:var:`!Py_HasFileSystemDefaultEncoding`: use :c:member:`PyConfig.filesystem_encoding`
  * :c:var:`!Py_FileSystemDefaultEncodeErrors`: use :c:member:`PyConfig.filesystem_errors`
  * :c:var:`!Py_UTF8Mode`: use :c:member:`PyPreConfig.utf8_mode` (see :c:func:`Py_PreInitialize`)

  The :c:func:`Py_InitializeFromConfig` API should be used with
  :c:type:`PyConfig` instead.

Pending Removal in Python 3.15
------------------------------

* :c:func:`PyImport_ImportModuleNoBlock`: use :c:func:`PyImport_ImportModule`.
* :c:func:`PyWeakref_GET_OBJECT`: use :c:func:`PyWeakref_GetRef` instead.
* :c:func:`PyWeakref_GetObject`: use :c:func:`PyWeakref_GetRef` instead.
* :c:type:`!Py_UNICODE_WIDE` type: use :c:type:`wchar_t` instead.
* :c:type:`Py_UNICODE` type: use :c:type:`wchar_t` instead.
* Python initialization functions:

  * :c:func:`PySys_ResetWarnOptions`: clear :data:`sys.warnoptions` and
    :data:`!warnings.filters` instead.
  * :c:func:`Py_GetExecPrefix`: get :data:`sys.exec_prefix` instead.
  * :c:func:`Py_GetPath`: get :data:`sys.path` instead.
  * :c:func:`Py_GetPrefix`: get :data:`sys.prefix` instead.
  * :c:func:`Py_GetProgramFullPath`: get :data:`sys.executable` instead.
  * :c:func:`Py_GetProgramName`: get :data:`sys.executable` instead.
  * :c:func:`Py_GetPythonHome`: get :c:member:`PyConfig.home` or
    :envvar:`PYTHONHOME` environment variable instead.

Pending Removal in Future Versions
----------------------------------

The following APIs were deprecated in earlier Python versions and will be
removed, although there is currently no date scheduled for their removal.

* :c:macro:`Py_TPFLAGS_HAVE_FINALIZE`: no needed since Python 3.8.
* :c:func:`PyErr_Fetch`: use :c:func:`PyErr_GetRaisedException`.
* :c:func:`PyErr_NormalizeException`: use :c:func:`PyErr_GetRaisedException`.
* :c:func:`PyErr_Restore`: use :c:func:`PyErr_SetRaisedException`.
* :c:func:`PyModule_GetFilename`: use :c:func:`PyModule_GetFilenameObject`.
* :c:func:`PyOS_AfterFork`: use :c:func:`PyOS_AfterFork_Child()`.
* :c:func:`PySlice_GetIndicesEx`.
* :c:func:`!PyUnicode_AsDecodedObject`.
* :c:func:`!PyUnicode_AsDecodedUnicode`.
* :c:func:`!PyUnicode_AsEncodedObject`.
* :c:func:`!PyUnicode_AsEncodedUnicode`.
* :c:func:`PyUnicode_READY`: not needed since Python 3.12.
* :c:func:`!_PyErr_ChainExceptions`.
* :c:member:`!PyBytesObject.ob_shash` member:
  call :c:func:`PyObject_Hash` instead.
* :c:member:`!PyDictObject.ma_version_tag` member.
* TLS API:

  * :c:func:`PyThread_create_key`: use :c:func:`PyThread_tss_alloc`.
  * :c:func:`PyThread_delete_key`: use :c:func:`PyThread_tss_free`.
  * :c:func:`PyThread_set_key_value`: use :c:func:`PyThread_tss_set`.
  * :c:func:`PyThread_get_key_value`: use :c:func:`PyThread_tss_get`.
  * :c:func:`PyThread_delete_key_value`: use :c:func:`PyThread_tss_delete`.
  * :c:func:`PyThread_ReInitTLS`: no longer needed.

* Remove undocumented ``PY_TIMEOUT_MAX`` constant from the limited C API.
  (Contributed by Victor Stinner in :gh:`110014`.)


Regression Test Changes
=======================

* Python built with :file:`configure` :option:`--with-pydebug` now
  supports a :option:`-X presite=package.module <-X>` command-line
  option. If used, it specifies a module that should be imported early
  in the lifecycle of the interpreter, before ``site.py`` is executed.
  (Contributed by Łukasz Langa in :gh:`110769`.)