****************************
  What's new in Python 3.14
****************************

: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 3.14, compared to 3.13.

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 3.14 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 3.14.
   Brevity is key.


.. PEP-sized items next.

* :ref:`PEP 649: deferred evaluation of annotations <whatsnew314-pep649>`
* :ref:`PEP 741: Python Configuration C API <whatsnew314-pep741>`
* :ref:`PEP 761: Discontinuation of PGP signatures <whatsnew314-pep761>`
* :ref:`A new type of interpreter  <whatsnew314-tail-call>`


Incompatible changes
====================

On platforms other than macOS and Windows, the default :ref:`start
method <multiprocessing-start-methods>` for :mod:`multiprocessing`
and :class:`~concurrent.futures.ProcessPoolExecutor` switches from
*fork* to *forkserver*.

See :ref:`(1) <whatsnew314-concurrent-futures-start-method>` and
:ref:`(2) <whatsnew314-multiprocessing-start-method>` for details.

If you encounter :exc:`NameError`\s or pickling errors coming out of
:mod:`multiprocessing` or :mod:`concurrent.futures`, see the
:ref:`forkserver restrictions <multiprocessing-programming-forkserver>`.


New features
============

.. _whatsnew314-pep649:

PEP 649: deferred evaluation of annotations
-------------------------------------------

The :term:`annotations <annotation>` on functions, classes, and modules are no
longer evaluated eagerly. Instead, annotations are stored in special-purpose
:term:`annotate functions <annotate function>` and evaluated only when
necessary. This is specified in :pep:`649` and :pep:`749`.

This change is designed to make annotations in Python more performant and more
usable in most circumstances. The runtime cost for defining annotations is
minimized, but it remains possible to introspect annotations at runtime.
It is usually no longer necessary to enclose annotations in strings if they
contain forward references.

The new :mod:`annotationlib` module provides tools for inspecting deferred
annotations. Annotations may be evaluated in the :attr:`~annotationlib.Format.VALUE`
format (which evaluates annotations to runtime values, similar to the behavior in
earlier Python versions), the :attr:`~annotationlib.Format.FORWARDREF` format
(which replaces undefined names with special markers), and the
:attr:`~annotationlib.Format.STRING` format (which returns annotations as strings).

This example shows how these formats behave:

.. doctest::

   >>> from annotationlib import get_annotations, Format
   >>> def func(arg: Undefined):
   ...     pass
   >>> get_annotations(func, format=Format.VALUE)
   Traceback (most recent call last):
     ...
   NameError: name 'Undefined' is not defined
   >>> get_annotations(func, format=Format.FORWARDREF)
   {'arg': ForwardRef('Undefined')}
   >>> get_annotations(func, format=Format.STRING)
   {'arg': 'Undefined'}

Implications for annotated code
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

If you define annotations in your code (for example, for use with a static type
checker), then this change probably does not affect you: you can keep
writing annotations the same way you did with previous versions of Python.

You will likely be able to remove quoted strings in annotations, which are frequently
used for forward references. Similarly, if you use ``from __future__ import annotations``
to avoid having to write strings in annotations, you may well be able to
remove that import. However, if you rely on third-party libraries that read annotations,
those libraries may need changes to support unquoted annotations before they
work as expected.

Implications for readers of ``__annotations__``
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

If your code reads the ``__annotations__`` attribute on objects, you may want
to make changes in order to support code that relies on deferred evaluation of
annotations. For example, you may want to use :func:`annotationlib.get_annotations`
with the :attr:`~annotationlib.Format.FORWARDREF` format, as the :mod:`dataclasses`
module now does.

Related changes
^^^^^^^^^^^^^^^

The changes in Python 3.14 are designed to rework how ``__annotations__``
works at runtime while minimizing breakage to code that contains
annotations in source code and to code that reads ``__annotations__``. However,
if you rely on undocumented details of the annotation behavior or on private
functions in the standard library, there are many ways in which your code may
not work in Python 3.14. To safeguard your code against future changes,
use only the documented functionality of the :mod:`annotationlib` module.

``from __future__ import annotations``
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

In Python 3.7, :pep:`563` introduced the ``from __future__ import annotations``
directive, which turns all annotations into strings. This directive is now
considered deprecated and it is expected to be removed in a future version of Python.
However, this removal will not happen until after Python 3.13, the last version of
Python without deferred evaluation of annotations, reaches its end of life in 2029.
In Python 3.14, the behavior of code using ``from __future__ import annotations``
is unchanged.


Improved error messages
-----------------------

* When unpacking assignment fails due to incorrect number of variables, the
  error message prints the received number of values in more cases than before.
  (Contributed by Tushar Sadhwani in :gh:`122239`.)

  .. code-block:: python

     >>> x, y, z = 1, 2, 3, 4
     Traceback (most recent call last):
       File "<stdin>", line 1, in <module>
         x, y, z = 1, 2, 3, 4
         ^^^^^^^
     ValueError: too many values to unpack (expected 3, got 4)


* If a statement (:keyword:`pass`, :keyword:`del`, :keyword:`return`,
  :keyword:`yield`, :keyword:`raise`, :keyword:`break`, :keyword:`continue`,
  :keyword:`assert`, :keyword:`import`, :keyword:`from`) is passed to the
  :ref:`if_expr` after :keyword:`else`, or one of :keyword:`pass`,
  :keyword:`break`, or :keyword:`continue` is passed before :keyword:`if`, then the
  error message highlights where the :token:`~python-grammar:expression` is
  required. (Contributed by Sergey Miryanov in :gh:`129515`.)

  .. code-block:: pycon

     >>> x = 1 if True else pass
     Traceback (most recent call last):
       File "<string>", line 1
         x = 1 if True else pass
                            ^^^^
     SyntaxError: expected expression after 'else', but statement is given

     >>> x = continue if True else break
     Traceback (most recent call last):
       File "<string>", line 1
         x = continue if True else break
             ^^^^^^^^
     SyntaxError: expected expression before 'if', but statement is given


* When incorrectly closed strings are detected, the error message suggests
  that the string may be intended to be part of the string. (Contributed by
  Pablo Galindo in :gh:`88535`.)

  .. code-block:: python

    >>> "The interesting object "The important object" is very important"
    Traceback (most recent call last):
    SyntaxError: invalid syntax. Is this intended to be part of the string?


.. _whatsnew314-pep741:

PEP 741: Python Configuration C API
-----------------------------------

Add a :ref:`PyInitConfig C API <pyinitconfig_api>` to configure the Python
initialization without relying on C structures and the ability to make
ABI-compatible changes in the future.

Complete the :pep:`587` :ref:`PyConfig C API <pyconfig_api>` by adding
:c:func:`PyInitConfig_AddModule` which can be used to add a built-in extension
module; feature previously referred to as the “inittab”.

Add :c:func:`PyConfig_Get` and :c:func:`PyConfig_Set` functions to get and set
the current runtime configuration.

PEP 587 “Python Initialization Configuration” unified all the ways to configure
the Python initialization. This PEP unifies also the configuration of the
Python preinitialization and the Python initialization in a single API.
Moreover, this PEP only provides a single choice to embed Python, instead of
having two “Python” and “Isolated” choices (PEP 587), to simplify the API
further.

The lower level PEP 587 PyConfig API remains available for use cases with an
intentionally higher level of coupling to CPython implementation details (such
as emulating the full functionality of CPython’s CLI, including its
configuration mechanisms).

(Contributed by Victor Stinner in :gh:`107954`.)

.. seealso::
   :pep:`741`.

.. _whatsnew314-tail-call:

A new type of interpreter
-------------------------

A new type of interpreter has been added to CPython.
It uses tail calls between small C functions that implement individual
Python opcodes, rather than one large C case statement.
For certain newer compilers, this interpreter provides
significantly better performance. Preliminary numbers on our machines suggest
anywhere from -3% to 30% faster Python code, and a geometric mean of 9-15%
faster on ``pyperformance`` depending on platform and architecture. The
baseline is Python 3.14 built with Clang 19 without this new interpreter.

This interpreter currently only works with Clang 19 and newer
on x86-64 and AArch64 architectures. However, we expect
that a future release of GCC will support this as well.

This feature is opt-in for now. We highly recommend enabling profile-guided
optimization with the new interpreter as it is the only configuration we have
tested and can validate its improved performance.
For further information on how to build Python, see
:option:`--with-tail-call-interp`.

.. note::

   This is not to be confused with `tail call optimization`__ of Python
   functions, which is currently not implemented in CPython.

   This new interpreter type is an internal implementation detail of the CPython
   interpreter.  It doesn't change the visible behavior of Python programs at
   all.  It can improve their performance, but doesn't change anything else.

   __ https://en.wikipedia.org/wiki/Tail_call

(Contributed by Ken Jin in :gh:`128563`, with ideas on how to implement this
in CPython by Mark Shannon, Garrett Gu, Haoran Xu, and Josh Haberman.)


Other language changes
======================

* The :func:`map` built-in now has an optional keyword-only *strict* flag
  like :func:`zip` to check that all the iterables are of equal length.
  (Contributed by Wannes Boeykens in :gh:`119793`.)

* Incorrect usage of :keyword:`await` and asynchronous comprehensions
  is now detected even if the code is optimized away by the :option:`-O`
  command-line option. For example, ``python -O -c 'assert await 1'``
  now produces a :exc:`SyntaxError`. (Contributed by Jelle Zijlstra in :gh:`121637`.)

* Writes to ``__debug__`` are now detected even if the code is optimized
  away by the :option:`-O` command-line option. For example,
  ``python -O -c 'assert (__debug__ := 1)'`` now produces a
  :exc:`SyntaxError`. (Contributed by Irit Katriel in :gh:`122245`.)

* Add class methods :meth:`float.from_number` and :meth:`complex.from_number`
  to convert a number to :class:`float` or :class:`complex` type correspondingly.
  They raise an error if the argument is a string.
  (Contributed by Serhiy Storchaka in :gh:`84978`.)

* Implement mixed-mode arithmetic rules combining real and complex numbers as
  specified by C standards since C99.
  (Contributed by Sergey B Kirpichev in :gh:`69639`.)

* All Windows code pages are now supported as "cpXXX" codecs on Windows.
  (Contributed by Serhiy Storchaka in :gh:`123803`.)

* :class:`super` objects are now :mod:`pickleable <pickle>` and
  :mod:`copyable <copy>`.
  (Contributed by Serhiy Storchaka in :gh:`125767`.)

* The :class:`memoryview` type now supports subscription,
  making it a :term:`generic type`.
  (Contributed by Brian Schubert in :gh:`126012`.)

* Support underscore and comma as thousands separators in the fractional part
  for floating-point presentation types of the new-style string formatting
  (with :func:`format` or :ref:`f-strings`).
  (Contrubuted by Sergey B Kirpichev in :gh:`87790`.)

* ``\B`` in :mod:`regular expression <re>` now matches empty input string.
  Now it is always the opposite of ``\b``.
  (Contributed by Serhiy Storchaka in :gh:`124130`.)

* iOS and macOS apps can now be configured to redirect ``stdout`` and
  ``stderr`` content to the system log. (Contributed by Russell Keith-Magee in
  :gh:`127592`.)

* The iOS testbed is now able to stream test output while the test is running.
  The testbed can also be used to run the test suite of projects other than
  CPython itself. (Contributed by Russell Keith-Magee in :gh:`127592`.)

New modules
===========

* :mod:`annotationlib`: For introspecting :term:`annotations <annotation>`.
  See :pep:`749` for more details.
  (Contributed by Jelle Zijlstra in :gh:`119180`.)


Improved modules
================

argparse
--------

* The default value of the :ref:`program name <prog>` for
  :class:`argparse.ArgumentParser` now reflects the way the Python
  interpreter was instructed to find the ``__main__`` module code.
  (Contributed by Serhiy Storchaka and Alyssa Coghlan in :gh:`66436`.)

* Introduced the optional *suggest_on_error* parameter to
  :class:`argparse.ArgumentParser`, enabling suggestions for argument choices
  and subparser names if mistyped by the user.
  (Contributed by Savannah Ostrowski in :gh:`124456`.)

ast
---

* Add :func:`ast.compare` for comparing two ASTs.
  (Contributed by Batuhan Taskaya and Jeremy Hylton in :gh:`60191`.)

* Add support for :func:`copy.replace` for AST nodes.
  (Contributed by Bénédikt Tran in :gh:`121141`.)

* Docstrings are now removed from an optimized AST in optimization level 2.
  (Contributed by Irit Katriel in :gh:`123958`.)

* The ``repr()`` output for AST nodes now includes more information.
  (Contributed by Tomas R in :gh:`116022`.)

* :func:`ast.parse`, when called with an AST as input, now always verifies
  that the root node type is appropriate.
  (Contributed by Irit Katriel in :gh:`130139`.)


calendar
--------

* By default, today's date is highlighted in color in :mod:`calendar`'s
  :ref:`command-line <calendar-cli>` text output.
  This can be controlled via the :envvar:`PYTHON_COLORS` environment
  variable as well as the canonical |NO_COLOR|_
  and |FORCE_COLOR|_ environment variables.
  See also :ref:`using-on-controlling-color`.
  (Contributed by Hugo van Kemenade in :gh:`128317`.)


concurrent.futures
------------------

* Add :class:`~concurrent.futures.InterpreterPoolExecutor`,
  which exposes "subinterpreters (multiple Python interpreters in the
  same process) to Python code.  This is separate from the proposed API
  in :pep:`734`.
  (Contributed by Eric Snow in :gh:`124548`.)

.. _whatsnew314-concurrent-futures-start-method:

* The default :class:`~concurrent.futures.ProcessPoolExecutor`
  :ref:`start method <multiprocessing-start-methods>` changed
  from :ref:`fork <multiprocessing-start-method-fork>` to :ref:`forkserver
  <multiprocessing-start-method-forkserver>` on platforms other than macOS and
  Windows where it was already :ref:`spawn <multiprocessing-start-method-spawn>`.

  If the threading incompatible *fork* method is required, you must explicitly
  request it by supplying a multiprocessing context *mp_context* to
  :class:`~concurrent.futures.ProcessPoolExecutor`.

  See :ref:`forkserver restrictions <multiprocessing-programming-forkserver>`
  for information and differences with the *fork* method and how this change
  may affect existing code with mutable global shared variables and/or shared
  objects that can not be automatically :mod:`pickled <pickle>`.

  (Contributed by Gregory P. Smith in :gh:`84559`.)


contextvars
-----------

* Support context manager protocol by :class:`contextvars.Token`.
  (Contributed by Andrew Svetlov in :gh:`129889`.)


ctypes
------

* The layout of :ref:`bit fields <ctypes-bit-fields-in-structures-unions>`
  in :class:`~ctypes.Structure` and :class:`~ctypes.Union`
  now matches platform defaults (GCC/Clang or MSVC) more closely.
  In particular, fields no longer overlap.
  (Contributed by Matthias Görgens in :gh:`97702`.)

* The :attr:`.Structure._layout_` class attribute can now be set
  to help match a non-default ABI.
  (Contributed by Petr Viktorin in :gh:`97702`.)

* On Windows, the :exc:`~ctypes.COMError` exception is now public.
  (Contributed by Jun Komoda in :gh:`126686`.)

* On Windows, the :func:`~ctypes.CopyComPointer` function is now public.
  (Contributed by Jun Komoda in :gh:`127275`.)

* :func:`ctypes.memoryview_at` now exists to create a
  :class:`memoryview` object that refers to the supplied pointer and
  length. This works like :func:`ctypes.string_at` except it avoids a
  buffer copy, and is typically useful when implementing pure Python
  callback functions that are passed dynamically-sized buffers.
  (Contributed by Rian Hunter in :gh:`112018`.)

* Complex types, :class:`~ctypes.c_float_complex`,
  :class:`~ctypes.c_double_complex` and :class:`~ctypes.c_longdouble_complex`,
  are now available if both the compiler and the ``libffi`` library support
  complex C types.
  (Contributed by Sergey B Kirpichev in :gh:`61103`).

* Add :func:`ctypes.util.dllist` for listing the shared libraries
  loaded by the current process.
  (Contributed by Brian Ward in :gh:`119349`.)

datetime
--------

* Add :meth:`datetime.time.strptime` and :meth:`datetime.date.strptime`.
  (Contributed by Wannes Boeykens in :gh:`41431`.)

decimal
-------

* Add alternative :class:`~decimal.Decimal` constructor
  :meth:`Decimal.from_number() <decimal.Decimal.from_number>`.
  (Contributed by Serhiy Storchaka in :gh:`121798`.)

difflib
-------

* Comparison pages with highlighted changes generated by the
  :class:`difflib.HtmlDiff` class now support dark mode.
  (Contributed by Jiahao Li in :gh:`129939`.)

dis
---

* Add support for rendering full source location information of
  :class:`instructions <dis.Instruction>`, rather than only the line number.
  This feature is added to the following interfaces via the *show_positions*
  keyword argument:

  - :class:`dis.Bytecode`
  - :func:`dis.dis`
  - :func:`dis.distb`
  - :func:`dis.disassemble`

  This feature is also exposed via :option:`dis --show-positions`.
  (Contributed by Bénédikt Tran in :gh:`123165`.)

* Add the :option:`dis --specialized` command-line option to
  show specialized bytecode.
  (Contributed by Bénédikt Tran in :gh:`127413`.)


errno
-----

* Add :data:`errno.EHWPOISON` error code.
  (Contributed by James Roy in :gh:`126585`.)


fractions
---------

* Add support for converting any objects that have the
  :meth:`!as_integer_ratio` method to a :class:`~fractions.Fraction`.
  (Contributed by Serhiy Storchaka in :gh:`82017`.)

* Add alternative :class:`~fractions.Fraction` constructor
  :meth:`Fraction.from_number() <fractions.Fraction.from_number>`.
  (Contributed by Serhiy Storchaka in :gh:`121797`.)


functools
---------

* Add support to :func:`functools.partial` and
  :func:`functools.partialmethod` for :data:`functools.Placeholder` sentinels
  to reserve a place for positional arguments.
  (Contributed by Dominykas Grigonis in :gh:`119127`.)

* Allow the *initial* parameter of :func:`functools.reduce` to be passed
  as a keyword argument.
  (Contributed by Sayandip Dutta in :gh:`125916`.)


getopt
------

* Add support for options with optional arguments.
  (Contributed by Serhiy Storchaka in :gh:`126374`.)

* Add support for returning intermixed options and non-option arguments in order.
  (Contributed by Serhiy Storchaka in :gh:`126390`.)

http
----

* Directory lists and error pages generated by the :mod:`http.server`
  module allow the browser to apply its default dark mode.
  (Contributed by Yorik Hansen in :gh:`123430`.)


imaplib
-------

* Add :meth:`IMAP4.idle() <imaplib.IMAP4.idle>`, implementing the IMAP4
  ``IDLE`` command as defined in :rfc:`2177`.
  (Contributed by Forest in :gh:`55454`.)


inspect
-------

* :func:`inspect.signature` takes a new argument *annotation_format* to control
  the :class:`annotationlib.Format` used for representing annotations.
  (Contributed by Jelle Zijlstra in :gh:`101552`.)

* :meth:`inspect.Signature.format` takes a new argument *unquote_annotations*.
  If true, string :term:`annotations <annotation>` are displayed without surrounding quotes.
  (Contributed by Jelle Zijlstra in :gh:`101552`.)

* Add function :func:`inspect.ispackage` to determine whether an object is a
  :term:`package` or not.
  (Contributed by Zhikang Yan in :gh:`125634`.)


io
--

* Reading text from a non-blocking stream with ``read`` may now raise a
  :exc:`BlockingIOError` if the operation cannot immediately return bytes.
  (Contributed by Giovanni Siragusa in :gh:`109523`.)


json
----

* Add notes for JSON serialization errors that allow to identify the source
  of the error.
  (Contributed by Serhiy Storchaka in :gh:`122163`.)

* Enable the :mod:`json` module to work as a script using the :option:`-m`
  switch: :program:`python -m json`.
  See the :ref:`JSON command-line interface <json-commandline>` documentation.
  (Contributed by Trey Hunner in :gh:`122873`.)


mimetypes
---------

* Add MS and :rfc:`8081` MIME types for fonts:

  * Embedded OpenType: ``application/vnd.ms-fontobject``
  * OpenType Layout (OTF) ``font/otf``
  * TrueType: ``font/ttf``
  * WOFF 1.0 ``font/woff``
  * WOFF 2.0 ``font/woff2``

  (Contributed by Sahil Prajapati and Hugo van Kemenade in :gh:`84852`.)

* Add :rfc:`9559` MIME types for Matroska audiovisual data container
  structures, containing:

  * audio with no video: ``audio/matroska`` (``.mka``)
  * video: ``video/matroska`` (``.mkv``)
  * stereoscopic video: ``video/matroska-3d`` (``.mk3d``)

  (Contributed by Hugo van Kemenade in :gh:`89416`.)

* Add MIME types for images with RFCs:

  * :rfc:`1494`: CCITT Group 3 (``.g3``)
  * :rfc:`3362`: Real-time Facsimile, T.38 (``.t38``)
  * :rfc:`3745`: JPEG 2000 (``.jp2``), extension (``.jpx``) and compound (``.jpm``)
  * :rfc:`3950`: Tag Image File Format Fax eXtended, TIFF-FX (``.tfx``)
  * :rfc:`4047`: Flexible Image Transport System (``.fits``)
  * :rfc:`7903`: Enhanced Metafile (``.emf``) and Windows Metafile (``.wmf``)

  (Contributed by Hugo van Kemenade in :gh:`85957`.)

* More MIME type changes:

  * :rfc:`2361`: Change type for ``.avi`` to ``video/vnd.avi``
    and for ``.wav`` to ``audio/vnd.wave``
  * :rfc:`4337`: Add MPEG-4 ``audio/mp4`` (``.m4a``))
  * :rfc:`5334`: Add Ogg media (``.oga``, ``.ogg`` and ``.ogx``)
  * :rfc:`9639`: Add FLAC ``audio/flac`` (``.flac``)
  * De facto: Add WebM ``audio/webm`` (``.weba``)
  * `ECMA-376
    <https://ecma-international.org/publications-and-standards/standards/ecma-376/>`__:
    Add ``.docx``, ``.pptx`` and ``.xlsx`` types
  * `OASIS
    <https://docs.oasis-open.org/office/v1.2/cs01/OpenDocument-v1.2-cs01-part1.html#Appendix_C>`__:
    Add OpenDocument ``.odg``, ``.odp``, ``.ods`` and ``.odt`` types
  * `W3C <https://www.w3.org/TR/epub-33/#app-media-type>`__:
    Add EPUB ``application/epub+zip`` (``.epub``)

  (Contributed by Hugo van Kemenade in :gh:`129965`.)


multiprocessing
---------------

.. _whatsnew314-multiprocessing-start-method:

* The default :ref:`start method <multiprocessing-start-methods>` changed
  from :ref:`fork <multiprocessing-start-method-fork>` to :ref:`forkserver
  <multiprocessing-start-method-forkserver>` on platforms other than macOS and
  Windows where it was already :ref:`spawn <multiprocessing-start-method-spawn>`.

  If the threading incompatible *fork* method is required, you must explicitly
  request it via a context from :func:`multiprocessing.get_context` (preferred)
  or change the default via :func:`multiprocessing.set_start_method`.

  See :ref:`forkserver restrictions <multiprocessing-programming-forkserver>`
  for information and differences with the *fork* method and how this change
  may affect existing code with mutable global shared variables and/or shared
  objects that can not be automatically :mod:`pickled <pickle>`.

  (Contributed by Gregory P. Smith in :gh:`84559`.)

* :mod:`multiprocessing`'s ``"forkserver"`` start method now authenticates
  its control socket to avoid solely relying on filesystem permissions
  to restrict what other processes could cause the forkserver to spawn workers
  and run code.
  (Contributed by Gregory P. Smith for :gh:`97514`.)

* The :ref:`multiprocessing proxy objects <multiprocessing-proxy_objects>`
  for *list* and *dict* types gain previously overlooked missing methods:

   * :meth:`!clear` and :meth:`!copy` for proxies of :class:`list`.
   * :meth:`~dict.fromkeys`, ``reversed(d)``, ``d | {}``, ``{} | d``,
     ``d |= {'b': 2}`` for proxies of :class:`dict`.

  (Contributed by Roy Hyunjin Han for :gh:`103134`.)

* Add support for shared :class:`set` objects via
  :meth:`SyncManager.set() <multiprocessing.managers.SyncManager.set>`.
  The :func:`set` in :func:`multiprocessing.Manager` method is now available.
  (Contributed by Mingyu Park in :gh:`129949`.)


operator
--------

* Two new functions :func:`operator.is_none` and :func:`operator.is_not_none`
  have been added, such that ``operator.is_none(obj)`` is equivalent
  to ``obj is None`` and ``operator.is_not_none(obj)`` is equivalent
  to ``obj is not None``.
  (Contributed by Raymond Hettinger and Nico Mexis in :gh:`115808`.)


os
--

* Add the :func:`os.reload_environ` function to update :data:`os.environ` and
  :data:`os.environb` with changes to the environment made by
  :func:`os.putenv`, by :func:`os.unsetenv`, or made outside Python in the
  same process.
  (Contributed by Victor Stinner in :gh:`120057`.)

* Add the :data:`~os.SCHED_DEADLINE` and :data:`~os.SCHED_NORMAL` constants
  to the :mod:`os` module.
  (Contributed by James Roy in :gh:`127688`.)

* Add the :func:`os.readinto` function to read into a
  :ref:`buffer object <bufferobjects>` from a file descriptor.
  (Contributed by Cody Maloney in :gh:`129205`.)


pathlib
-------

* Add methods to :class:`pathlib.Path` to recursively copy or move files and
  directories:

  * :meth:`~pathlib.Path.copy` copies a file or directory tree to a destination.
  * :meth:`~pathlib.Path.copy_into` copies *into* a destination directory.
  * :meth:`~pathlib.Path.move` moves a file or directory tree to a destination.
  * :meth:`~pathlib.Path.move_into` moves *into* a destination directory.

  (Contributed by Barney Gale in :gh:`73991`.)

* Add :attr:`pathlib.Path.info` attribute, which stores an object
  implementing the :class:`pathlib.types.PathInfo` protocol (also new). The
  object supports querying the file type and internally caching
  :func:`~os.stat` results. Path objects generated by
  :meth:`~pathlib.Path.iterdir` are initialized with file type information
  gleaned from scanning the parent directory.
  (Contributed by Barney Gale in :gh:`125413`.)


pdb
---

* Hardcoded breakpoints (:func:`breakpoint` and :func:`pdb.set_trace`) now
  reuse the most recent :class:`~pdb.Pdb` instance that calls
  :meth:`~pdb.Pdb.set_trace`, instead of creating a new one each time.
  As a result, all the instance specific data like :pdbcmd:`display` and
  :pdbcmd:`commands` are preserved across hardcoded breakpoints.
  (Contributed by Tian Gao in :gh:`121450`.)

* Add a new argument *mode* to :class:`pdb.Pdb`. Disable the ``restart``
  command when :mod:`pdb` is in ``inline`` mode.
  (Contributed by Tian Gao in :gh:`123757`.)

* A confirmation prompt will be shown when the user tries to quit :mod:`pdb`
  in ``inline`` mode. ``y``, ``Y``, ``<Enter>`` or ``EOF`` will confirm
  the quit and call :func:`sys.exit`, instead of raising :exc:`bdb.BdbQuit`.
  (Contributed by Tian Gao in :gh:`124704`.)

* Inline breakpoints like :func:`breakpoint` or :func:`pdb.set_trace` will
  always stop the program at calling frame, ignoring the ``skip`` pattern
  (if any).
  (Contributed by Tian Gao in :gh:`130493`.)

* ``<tab>`` at the beginning of the line in :mod:`pdb` multi-line input will
  fill in a 4-space indentation now, instead of inserting a ``\t`` character.
  (Contributed by Tian Gao in :gh:`130471`.)


pickle
------

* Set the default protocol version on the :mod:`pickle` module to 5.
  For more details, see :ref:`pickle protocols <pickle-protocols>`.

* Add notes for pickle serialization errors that allow to identify the source
  of the error.
  (Contributed by Serhiy Storchaka in :gh:`122213`.)


platform
--------

* Add :func:`platform.invalidate_caches` to invalidate the cached results.
  (Contributed by Bénédikt Tran in :gh:`122549`.)


pydoc
-----

* :term:`Annotations <annotation>` in help output are now usually
  displayed in a format closer to that in the original source.
  (Contributed by Jelle Zijlstra in :gh:`101552`.)


ssl
---

* Indicate through :data:`ssl.HAS_PHA` whether the :mod:`ssl` module supports
  TLSv1.3 post-handshake client authentication (PHA).
  (Contributed by Will Childs-Klein in :gh:`128036`.)


symtable
--------

* Expose the following :class:`symtable.Symbol` methods:

  * :meth:`~symtable.Symbol.is_comp_cell`
  * :meth:`~symtable.Symbol.is_comp_iter`
  * :meth:`~symtable.Symbol.is_free_class`

  (Contributed by Bénédikt Tran in :gh:`120029`.)


sys
---

* The previously undocumented special function :func:`sys.getobjects`,
  which only exists in specialized builds of Python, may now return objects
  from other interpreters than the one it's called in.

* Add :func:`sys._is_immortal` for determining if an object is :term:`immortal`.
  (Contributed by Peter Bierma in :gh:`128509`.)

* On FreeBSD, :data:`sys.platform` doesn't contain the major version anymore.
  It is always ``'freebsd'``, instead of ``'freebsd13'`` or ``'freebsd14'``.


sys.monitoring
--------------

* Two new events are added: :monitoring-event:`BRANCH_LEFT` and
  :monitoring-event:`BRANCH_RIGHT`. The ``BRANCH`` event is deprecated.

threading
---------

* :meth:`threading.Thread.start` now sets the operating system thread name
  to :attr:`threading.Thread.name`.
  (Contributed by Victor Stinner in :gh:`59705`.)

tkinter
-------

* Make tkinter widget methods :meth:`!after` and :meth:`!after_idle` accept
  arguments passed by keyword.
  (Contributed by Zhikang Yan in :gh:`126899`.)


turtle
------

* Add context managers for :func:`turtle.fill`, :func:`turtle.poly`
  and :func:`turtle.no_animation`.
  (Contributed by Marie Roald and Yngve Mardal Moe in :gh:`126350`.)


unicodedata
-----------

* The Unicode database has been updated to Unicode 16.0.0.


unittest
--------

* :mod:`unittest` output is now colored by default.
  This can be controlled via the :envvar:`PYTHON_COLORS` environment
  variable as well as the canonical |NO_COLOR|_
  and |FORCE_COLOR|_ environment variables.
  See also :ref:`using-on-controlling-color`.
  (Contributed by Hugo van Kemenade in :gh:`127221`.)

* unittest discovery supports :term:`namespace package` as start
  directory again. It was removed in Python 3.11.
  (Contributed by Jacob Walls in :gh:`80958`.)

* A number of new methods were added in the :class:`~unittest.TestCase` class
  that provide more specialized tests.

  - :meth:`~unittest.TestCase.assertHasAttr` and
    :meth:`~unittest.TestCase.assertNotHasAttr` check whether the object
    has a particular attribute.
  - :meth:`~unittest.TestCase.assertIsSubclass` and
    :meth:`~unittest.TestCase.assertNotIsSubclass` check whether the object
    is a subclass of a particular class, or of one of a tuple of classes.
  - :meth:`~unittest.TestCase.assertStartsWith`,
    :meth:`~unittest.TestCase.assertNotStartsWith`,
    :meth:`~unittest.TestCase.assertEndsWith` and
    :meth:`~unittest.TestCase.assertNotEndsWith` check whether the Unicode
    or byte string starts or ends with particular string(s).

  (Contributed by Serhiy Storchaka in :gh:`71339`.)


urllib
------

* Upgrade HTTP digest authentication algorithm for :mod:`urllib.request` by
  supporting SHA-256 digest authentication as specified in :rfc:`7616`.
  (Contributed by Calvin Bui in :gh:`128193`.)


uuid
----

* Add support for UUID versions 6, 7, and 8 via :func:`uuid.uuid6`,
  :func:`uuid.uuid7`, and :func:`uuid.uuid8` respectively, as specified
  in :rfc:`9562`.
  (Contributed by Bénédikt Tran in :gh:`89083`.)

* :const:`uuid.NIL` and :const:`uuid.MAX` are now available to represent the
  Nil and Max UUID formats as defined by :rfc:`9562`.
  (Contributed by Nick Pope in :gh:`128427`.)


zipinfo
-------

* Added :func:`ZipInfo._for_archive <zipfile.ZipInfo._for_archive>`
  to resolve suitable defaults for a :class:`~zipfile.ZipInfo` object
  as used by :func:`ZipFile.writestr <zipfile.ZipFile.writestr>`.
  (Contributed by Bénédikt Tran in :gh:`123424`.)

* :meth:`zipfile.ZipFile.writestr` now respect ``SOURCE_DATE_EPOCH`` that
  distributions can set centrally and have build tools consume this in order
  to produce reproducible output.
  (Contributed by Jiahao Li in :gh:`91279`.)

.. Add improved modules above alphabetically, not here at the end.

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

asyncio
-------

* :mod:`asyncio` now uses double linked list implementation for native tasks
  which speeds up execution by 10% on standard pyperformance benchmarks and
  reduces memory usage.
  (Contributed by Kumar Aditya in :gh:`107803`.)

* :mod:`asyncio` has new utility functions for introspecting and printing
  the program's call graph: :func:`asyncio.capture_call_graph` and
  :func:`asyncio.print_call_graph`.
  (Contributed by Yury Selivanov, Pablo Galindo Salgado, and Łukasz Langa
  in :gh:`91048`.)

base64
------

* Improve the performance of :func:`base64.b16decode` by up to ten times,
  and reduce the import time of :mod:`base64` by up to six times.
  (Contributed by Bénédikt Tran, Chris Markiewicz, and Adam Turner in :gh:`118761`.)


io
---
* :mod:`io` which provides the built-in :func:`open` makes less system calls
  when opening regular files as well as reading whole files. Reading a small
  operating system cached file in full is up to 15% faster.
  :func:`pathlib.Path.read_bytes` has the most optimizations for reading a
  file's bytes in full. (Contributed by Cody Maloney and Victor Stinner in
  :gh:`120754` and :gh:`90102`.)


uuid
----

* Improve generation of :class:`~uuid.UUID` objects via their dedicated
  functions:

  * :func:`~uuid.uuid3` and :func:`~uuid.uuid5` are both roughly 40% faster
    for 16-byte names and 20% faster for 1024-byte names. Performance for
    longer names remains unchanged.
  * :func:`~uuid.uuid4` and :func:`~uuid.uuid8` are 30% and 40% faster
    respectively.

  (Contributed by Bénédikt Tran in :gh:`128150`.)


Deprecated
==========

* :mod:`argparse`:

  * Passing the undocumented keyword argument *prefix_chars* to
    :meth:`~argparse.ArgumentParser.add_argument_group` is now
    deprecated.
    (Contributed by Savannah Ostrowski in :gh:`125563`.)
  * Deprecated the :class:`argparse.FileType` type converter.
    Anything with resource management should be done downstream after the
    arguments are parsed.
    (Contributed by Serhiy Storchaka in :gh:`58032`.)

* :mod:`asyncio`:

  * :func:`!asyncio.iscoroutinefunction` is deprecated
    and will be removed in Python 3.16;
    use :func:`inspect.iscoroutinefunction` instead.
    (Contributed by Jiahao Li and Kumar Aditya in :gh:`122875`.)

  * :mod:`asyncio` policy system is deprecated and will be removed in Python 3.16.
    In particular, the following classes and functions are deprecated:

    * :class:`asyncio.AbstractEventLoopPolicy`
    * :class:`asyncio.DefaultEventLoopPolicy`
    * :class:`asyncio.WindowsSelectorEventLoopPolicy`
    * :class:`asyncio.WindowsProactorEventLoopPolicy`
    * :func:`asyncio.get_event_loop_policy`
    * :func:`asyncio.set_event_loop_policy`
    * :func:`asyncio.set_event_loop`

    Users should use :func:`asyncio.run` or :class:`asyncio.Runner` with
    *loop_factory* to use the desired event loop implementation.

    For example, to use :class:`asyncio.SelectorEventLoop` on Windows::

      import asyncio

      async def main():
          ...

      asyncio.run(main(), loop_factory=asyncio.SelectorEventLoop)

    (Contributed by Kumar Aditya in :gh:`127949`.)

* :mod:`builtins`:
  Passing a complex number as the *real* or *imag* argument in the
  :func:`complex` constructor is now deprecated; it should only be passed
  as a single positional argument.
  (Contributed by Serhiy Storchaka in :gh:`109218`.)

* :mod:`functools`:
  Calling the Python implementation of :func:`functools.reduce` with *function*
  or *sequence* as keyword arguments is now deprecated.
  (Contributed by Kirill Podoprigora in :gh:`121676`.)

* :mod:`os`:
  :term:`Soft deprecate <soft deprecated>` :func:`os.popen` and
  :func:`os.spawn* <os.spawnl>` functions. They should no longer be used to
  write new code.  The :mod:`subprocess` module is recommended instead.
  (Contributed by Victor Stinner in :gh:`120743`.)

* :mod:`pdb`:
  The undocumented ``pdb.Pdb.curframe_locals`` attribute is now a deprecated
  read-only property. The low overhead dynamic frame locals access added in
  Python 3.13 by PEP 667 means the frame locals cache reference previously
  stored in this attribute is no longer needed. Derived debuggers should access
  ``pdb.Pdb.curframe.f_locals`` directly in Python 3.13 and later versions.
  (Contributed by Tian Gao in :gh:`124369` and :gh:`125951`.)

* :mod:`symtable`:
  Deprecate :meth:`symtable.Class.get_methods` due to the lack of interest.
  (Contributed by Bénédikt Tran in :gh:`119698`.)

* :mod:`urllib.parse`:
  Accepting objects with false values (like ``0`` and ``[]``) except empty
  strings, byte-like objects and ``None`` in :mod:`urllib.parse` functions
  :func:`~urllib.parse.parse_qsl` and :func:`~urllib.parse.parse_qs` is now
  deprecated.
  (Contributed by Serhiy Storchaka in :gh:`116897`.)

.. Add deprecations above alphabetically, not here at the end.

.. include:: ../deprecations/pending-removal-in-3.15.rst

.. include:: ../deprecations/pending-removal-in-3.16.rst

.. include:: ../deprecations/pending-removal-in-future.rst

Removed
=======

argparse
--------

* Remove the *type*, *choices*, and *metavar* parameters
  of :class:`!argparse.BooleanOptionalAction`.
  They were deprecated since 3.12.

* Calling :meth:`~argparse.ArgumentParser.add_argument_group` on an argument
  group, and calling :meth:`~argparse.ArgumentParser.add_argument_group` or
  :meth:`~argparse.ArgumentParser.add_mutually_exclusive_group` on a mutually
  exclusive group now raise exceptions. This nesting was never supported,
  often failed to work correctly, and was unintentionally exposed through
  inheritance. This functionality has been deprecated since Python 3.11.
  (Contributed by Savannah Ostrowski in :gh:`127186`.)

ast
---

* Remove the following classes. They were all deprecated since Python 3.8,
  and have emitted deprecation warnings since Python 3.12:

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

  Use :class:`ast.Constant` instead. As a consequence of these removals,
  user-defined ``visit_Num``, ``visit_Str``, ``visit_Bytes``,
  ``visit_NameConstant`` and ``visit_Ellipsis`` methods on custom
  :class:`ast.NodeVisitor` subclasses will no longer be called when the
  :class:`!NodeVisitor` subclass is visiting an AST. Define a ``visit_Constant``
  method instead.

  Also, remove the following deprecated properties on :class:`ast.Constant`,
  which were present for compatibility with the now-removed AST classes:

  * :attr:`!ast.Constant.n`
  * :attr:`!ast.Constant.s`

  Use :attr:`!ast.Constant.value` instead.
  (Contributed by Alex Waygood in :gh:`119562`.)

asyncio
-------

* Remove the following classes and functions. They were all deprecated and
  emitted deprecation warnings since Python 3.12:

  * :func:`!asyncio.get_child_watcher`
  * :func:`!asyncio.set_child_watcher`
  * :meth:`!asyncio.AbstractEventLoopPolicy.get_child_watcher`
  * :meth:`!asyncio.AbstractEventLoopPolicy.set_child_watcher`
  * :class:`!asyncio.AbstractChildWatcher`
  * :class:`!asyncio.FastChildWatcher`
  * :class:`!asyncio.MultiLoopChildWatcher`
  * :class:`!asyncio.PidfdChildWatcher`
  * :class:`!asyncio.SafeChildWatcher`
  * :class:`!asyncio.ThreadedChildWatcher`

  (Contributed by Kumar Aditya in :gh:`120804`.)

* Removed implicit creation of event loop by :func:`asyncio.get_event_loop`.
  It now raises a :exc:`RuntimeError` if there is no current event loop.
  (Contributed by Kumar Aditya in :gh:`126353`.)

  There's a few patterns that use :func:`asyncio.get_event_loop`, most
  of them can be replaced with :func:`asyncio.run`.

  If you're running an async function, simply use :func:`asyncio.run`.

  Before::

    async def main():
        ...


    loop = asyncio.get_event_loop()
    try:
        loop.run_until_complete(main())
    finally:
        loop.close()

  After::

    async def main():
        ...

    asyncio.run(main())

  If you need to start something, e.g. a server listening on a socket
  and then run forever, use :func:`asyncio.run` and an
  :class:`asyncio.Event`.

  Before::

    def start_server(loop):
        ...

    loop = asyncio.get_event_loop()
    try:
        start_server(loop)
        loop.run_forever()
    finally:
        loop.close()

  After::

    def start_server(loop):
        ...

    async def main():
        start_server(asyncio.get_running_loop())
        await asyncio.Event().wait()

    asyncio.run(main())

  If you need to run something in an event loop, then run some blocking
  code around it, use :class:`asyncio.Runner`.

  Before::

    async def operation_one():
        ...

    def blocking_code():
        ...

    async def operation_two():
        ...

    loop = asyncio.get_event_loop()
    try:
        loop.run_until_complete(operation_one())
        blocking_code()
        loop.run_until_complete(operation_two())
    finally:
        loop.close()

  After::

    async def operation_one():
        ...

    def blocking_code():
        ...

    async def operation_two():
        ...

    with asyncio.Runner() as runner:
        runner.run(operation_one())
        blocking_code()
        runner.run(operation_two())



collections.abc
---------------

* Remove :class:`!collections.abc.ByteString`. It had previously raised a
  :exc:`DeprecationWarning` since Python 3.12.

email
-----

* Remove the *isdst* parameter from :func:`email.utils.localtime`.
  (Contributed by Hugo van Kemenade in :gh:`118798`.)

importlib
---------

* Remove deprecated :mod:`importlib.abc` 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`.)

itertools
---------

* Remove :mod:`itertools` support for copy, deepcopy, and pickle operations.
  These had previously raised a :exc:`DeprecationWarning` since Python 3.12.
  (Contributed by Raymond Hettinger in :gh:`101588`.)

pathlib
-------

* Remove support for passing additional keyword arguments to
  :class:`pathlib.Path`. In previous versions, any such arguments are ignored.
* Remove support for passing additional positional arguments to
  :meth:`pathlib.PurePath.relative_to` and
  :meth:`~pathlib.PurePath.is_relative_to`. In previous versions, any such
  arguments are joined onto *other*.

pkgutil
-------

* Remove deprecated :func:`!pkgutil.get_loader` and :func:`!pkgutil.find_loader`.
  These had previously raised a :exc:`DeprecationWarning` since Python 3.12.
  (Contributed by Bénédikt Tran in :gh:`97850`.)

pty
---

* Remove deprecated :func:`!pty.master_open` and :func:`!pty.slave_open`.
  They had previously raised a :exc:`DeprecationWarning` since Python 3.12.
  Use :func:`pty.openpty` instead.
  (Contributed by Nikita Sobolev in :gh:`118824`.)

sqlite3
-------

* Remove :data:`!version` and :data:`!version_info` from :mod:`sqlite3`.
  (Contributed by Hugo van Kemenade in :gh:`118924`.)

* Disallow using a sequence of parameters with named placeholders.
  This had previously raised a :exc:`DeprecationWarning` since Python 3.12;
  it will now raise a :exc:`sqlite3.ProgrammingError`.
  (Contributed by Erlend E. Aasland in :gh:`118928` and :gh:`101693`.)

typing
------

* Remove :class:`!typing.ByteString`. It had previously raised a
  :exc:`DeprecationWarning` since Python 3.12.

* :class:`typing.TypeAliasType` now supports star unpacking.

urllib
------

* Remove deprecated :class:`!Quoter` class from :mod:`urllib.parse`.
  It had previously raised a :exc:`DeprecationWarning` since Python 3.11.
  (Contributed by Nikita Sobolev in :gh:`118827`.)
* Remove deprecated :class:`!URLopener` and :class:`!FancyURLopener` classes
  from :mod:`urllib.request`. They had previously raised a
  :exc:`DeprecationWarning` since Python 3.3.

  ``myopener.open()`` can be replaced with :func:`~urllib.request.urlopen`,
  and ``myopener.retrieve()`` can be replaced with
  :func:`~urllib.request.urlretrieve`. Customizations to the opener
  classes can be replaced by passing customized handlers to
  :func:`~urllib.request.build_opener`.
  (Contributed by Barney Gale in :gh:`84850`.)

Others
------

* Using :data:`NotImplemented` in a boolean context will now raise a :exc:`TypeError`.
  It had previously raised a :exc:`DeprecationWarning` since Python 3.9. (Contributed
  by Jelle Zijlstra in :gh:`118767`.)

* The :func:`int` built-in no longer delegates to
  :meth:`~object.__trunc__`. Classes that want to support conversion to
  integer must implement either :meth:`~object.__int__` or
  :meth:`~object.__index__`. (Contributed by Mark Dickinson in :gh:`119743`.)


CPython Bytecode Changes
========================

* Replaced the opcode ``BINARY_SUBSCR`` by :opcode:`BINARY_OP` with oparg ``NB_SUBSCR``.
  (Contributed by Irit Katriel in :gh:`100239`.)

Porting to Python 3.14
======================

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

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

* :class:`functools.partial` is now a method descriptor.
  Wrap it in :func:`staticmethod` if you want to preserve the old behavior.
  (Contributed by Serhiy Storchaka and Dominykas Grigonis in :gh:`121027`.)

* The :func:`locale.nl_langinfo` function now sets temporarily the ``LC_CTYPE``
  locale in some cases.
  This temporary change affects other threads.
  (Contributed by Serhiy Storchaka in :gh:`69998`.)


Build changes
=============

* GNU Autoconf 2.72 is now required to generate :file:`configure`.
  (Contributed by Erlend Aasland in :gh:`115765`.)

.. _whatsnew314-pep761:

PEP 761: Discontinuation of PGP signatures
------------------------------------------

PGP signatures will not be available for CPython 3.14 and onwards.
Users verifying artifacts must use `Sigstore verification materials`_ for
verifying CPython artifacts. This change in release process is specified
in :pep:`761`.

.. _Sigstore verification materials: https://www.python.org/downloads/metadata/sigstore/


C API changes
=============

New features
------------

* Add :c:func:`PyLong_GetSign` function to get the sign of :class:`int` objects.
  (Contributed by Sergey B Kirpichev in :gh:`116560`.)

* Add a new :c:type:`PyUnicodeWriter` API to create a Python :class:`str`
  object:

  * :c:func:`PyUnicodeWriter_Create`
  * :c:func:`PyUnicodeWriter_DecodeUTF8Stateful`
  * :c:func:`PyUnicodeWriter_Discard`
  * :c:func:`PyUnicodeWriter_Finish`
  * :c:func:`PyUnicodeWriter_Format`
  * :c:func:`PyUnicodeWriter_WriteChar`
  * :c:func:`PyUnicodeWriter_WriteRepr`
  * :c:func:`PyUnicodeWriter_WriteStr`
  * :c:func:`PyUnicodeWriter_WriteSubstring`
  * :c:func:`PyUnicodeWriter_WriteUCS4`
  * :c:func:`PyUnicodeWriter_WriteUTF8`
  * :c:func:`PyUnicodeWriter_WriteWideChar`

  (Contributed by Victor Stinner in :gh:`119182`.)

* Add :c:func:`PyIter_NextItem` to replace :c:func:`PyIter_Next`,
  which has an ambiguous return value.
  (Contributed by Irit Katriel and Erlend Aasland in :gh:`105201`.)

* Add :c:func:`PyLong_IsPositive`, :c:func:`PyLong_IsNegative`
  and :c:func:`PyLong_IsZero` for checking if :c:type:`PyLongObject`
  is positive, negative, or zero, respectively.
  (Contributed by James Roy and Sergey B Kirpichev in :gh:`126061`.)

* Add new functions to convert C ``<stdint.h>`` numbers from/to Python
  :class:`int`:

  * :c:func:`PyLong_AsInt32`
  * :c:func:`PyLong_AsInt64`
  * :c:func:`PyLong_AsUInt32`
  * :c:func:`PyLong_AsUInt64`
  * :c:func:`PyLong_FromInt32`
  * :c:func:`PyLong_FromInt64`
  * :c:func:`PyLong_FromUInt32`
  * :c:func:`PyLong_FromUInt64`

  (Contributed by Victor Stinner in :gh:`120389`.)

* Add :c:func:`PyBytes_Join(sep, iterable) <PyBytes_Join>` function,
  similar to ``sep.join(iterable)`` in Python.
  (Contributed by Victor Stinner in :gh:`121645`.)

* Add :c:func:`Py_HashBuffer` to compute and return the hash value of a buffer.
  (Contributed by Antoine Pitrou and Victor Stinner in :gh:`122854`.)

* Add functions to get and set the current runtime Python configuration
  (:pep:`741`):

  * :c:func:`PyConfig_Get`
  * :c:func:`PyConfig_GetInt`
  * :c:func:`PyConfig_Set`
  * :c:func:`PyConfig_Names`

  (Contributed by Victor Stinner in :gh:`107954`.)

* Add functions to configure the Python initialization (:pep:`741`):

  * :c:func:`Py_InitializeFromInitConfig`
  * :c:func:`PyInitConfig_AddModule`
  * :c:func:`PyInitConfig_Create`
  * :c:func:`PyInitConfig_Free`
  * :c:func:`PyInitConfig_FreeStrList`
  * :c:func:`PyInitConfig_GetError`
  * :c:func:`PyInitConfig_GetExitCode`
  * :c:func:`PyInitConfig_GetInt`
  * :c:func:`PyInitConfig_GetStr`
  * :c:func:`PyInitConfig_GetStrList`
  * :c:func:`PyInitConfig_HasOption`
  * :c:func:`PyInitConfig_SetInt`
  * :c:func:`PyInitConfig_SetStr`
  * :c:func:`PyInitConfig_SetStrList`

  (Contributed by Victor Stinner in :gh:`107954`.)

* Add a new import and export API for Python :class:`int` objects (:pep:`757`):

  * :c:func:`PyLong_GetNativeLayout`;
  * :c:func:`PyLong_Export`;
  * :c:func:`PyLong_FreeExport`;
  * :c:func:`PyLongWriter_Create`;
  * :c:func:`PyLongWriter_Finish`;
  * :c:func:`PyLongWriter_Discard`.

  (Contributed by Sergey B Kirpichev and Victor Stinner in :gh:`102471`.)

* Add :c:func:`PyType_GetBaseByToken` and :c:data:`Py_tp_token` slot for easier
  superclass identification, which attempts to resolve the `type checking issue
  <https://peps.python.org/pep-0630/#type-checking>`__ mentioned in :pep:`630`
  (:gh:`124153`).

* Add :c:func:`PyUnicode_Equal` function to the limited C API:
  test if two strings are equal.
  (Contributed by Victor Stinner in :gh:`124502`.)

* Add :c:func:`PyType_Freeze` function to make a type immutable.
  (Contributed by Victor Stinner in :gh:`121654`.)

* Add :c:func:`PyUnstable_Object_EnableDeferredRefcount` for enabling
  deferred reference counting, as outlined in :pep:`703`.

* Add :c:func:`PyMonitoring_FireBranchLeftEvent` and
  :c:func:`PyMonitoring_FireBranchRightEvent` for generating
  :monitoring-event:`BRANCH_LEFT` and :monitoring-event:`BRANCH_RIGHT`
  events, respectively.

* Add :c:func:`Py_fopen` function to open a file. Similar to the
  :c:func:`!fopen` function, but the *path* parameter is a Python object and an
  exception is set on error. Add also :c:func:`Py_fclose` function to close a
  file.
  (Contributed by Victor Stinner in :gh:`127350`.)

* Add macros :c:func:`Py_PACK_VERSION` and :c:func:`Py_PACK_FULL_VERSION` for
  bit-packing Python version numbers.
  (Contributed by Petr Viktorin in :gh:`128629`.)

* Add :c:func:`PyUnstable_IsImmortal` for determining whether an object is :term:`immortal`,
  for debugging purposes.

* Add :c:func:`PyImport_ImportModuleAttr` and
  :c:func:`PyImport_ImportModuleAttrString` helper functions to import a module
  and get an attribute of the module.
  (Contributed by Victor Stinner in :gh:`128911`.)

* Add support for a new ``p`` format unit in :c:func:`Py_BuildValue` that allows to
  take a C integer and produce a Python :class:`bool` object. (Contributed by
  Pablo Galindo in :issue:`45325`.)


Limited C API changes
---------------------

* In the limited C API 3.14 and newer, :c:func:`Py_TYPE` and
  :c:func:`Py_REFCNT` are now implemented as an opaque function call to hide
  implementation details.
  (Contributed by Victor Stinner in :gh:`120600` and :gh:`124127`.)

* Remove :c:func:`PySequence_Fast` from the limited C API, since this function
  has to be used with :c:macro:`PySequence_Fast_GET_ITEM` which never worked
  in the limited C API.
  (Contributed by Victor Stinner in :gh:`91417`.)


Porting to Python 3.14
----------------------

* :c:func:`Py_Finalize` now deletes all interned strings. This
  is backwards incompatible to any C-Extension that holds onto an interned
  string after a call to :c:func:`Py_Finalize` and is then reused after a
  call to :c:func:`Py_Initialize`.  Any issues arising from this behavior will
  normally result in crashes during the execution of the subsequent call to
  :c:func:`Py_Initialize` from accessing uninitialized memory. To fix, use
  an address sanitizer to identify any use-after-free coming from
  an interned string and deallocate it during module shutdown.
  (Contributed by Eddie Elizondo in :gh:`113601`.)

* The :ref:`Unicode Exception Objects <unicodeexceptions>` C API
  now raises a :exc:`TypeError` if its exception argument is not
  a :exc:`UnicodeError` object.
  (Contributed by Bénédikt Tran in :gh:`127691`.)

* Private functions promoted to public C APIs:

  * ``_PyBytes_Join()``: :c:func:`PyBytes_Join`.
  * ``_PyLong_IsNegative()``: :c:func:`PyLong_IsNegative`.
  * ``_PyLong_IsPositive()``: :c:func:`PyLong_IsPositive`.
  * ``_PyLong_IsZero()``: :c:func:`PyLong_IsZero`.
  * ``_PyLong_Sign()``: :c:func:`PyLong_GetSign`.
  * ``_PyUnicodeWriter_Dealloc()``: :c:func:`PyUnicodeWriter_Discard`.
  * ``_PyUnicodeWriter_Finish()``: :c:func:`PyUnicodeWriter_Finish`.
  * ``_PyUnicodeWriter_Init()``: use :c:func:`PyUnicodeWriter_Create`.
  * ``_PyUnicodeWriter_Prepare()``: (no replacement).
  * ``_PyUnicodeWriter_PrepareKind()``: (no replacement).
  * ``_PyUnicodeWriter_WriteChar()``: :c:func:`PyUnicodeWriter_WriteChar`.
  * ``_PyUnicodeWriter_WriteStr()``: :c:func:`PyUnicodeWriter_WriteStr`.
  * ``_PyUnicodeWriter_WriteSubstring()``: :c:func:`PyUnicodeWriter_WriteSubstring`.
  * ``_PyUnicode_EQ()``: :c:func:`PyUnicode_Equal`.
  * ``_PyUnicode_Equal()``: :c:func:`PyUnicode_Equal`.
  * ``_Py_GetConfig()``: :c:func:`PyConfig_Get` and :c:func:`PyConfig_GetInt`.
  * ``_Py_HashBytes()``: :c:func:`Py_HashBuffer`.
  * ``_Py_fopen_obj()``: :c:func:`Py_fopen`.

  The `pythoncapi-compat project`_ can be used to get most of these new
  functions on Python 3.13 and older.

.. _pythoncapi-compat project: https://github.com/python/pythoncapi-compat/


.. _whatsnew314-c-api-deprecated:

Deprecated
----------

* The :c:macro:`!Py_HUGE_VAL` macro is :term:`soft deprecated`,
  use :c:macro:`!Py_INFINITY` instead.
  (Contributed by Sergey B Kirpichev in :gh:`120026`.)

* Macros :c:macro:`!Py_IS_NAN`, :c:macro:`!Py_IS_INFINITY`
  and :c:macro:`!Py_IS_FINITE` are :term:`soft deprecated`,
  use instead :c:macro:`!isnan`, :c:macro:`!isinf` and
  :c:macro:`!isfinite` available from :file:`math.h`
  since C99.  (Contributed by Sergey B Kirpichev in :gh:`119613`.)

* The previously undocumented function :c:func:`PySequence_In` is :term:`soft deprecated`.
  Use :c:func:`PySequence_Contains` instead.
  (Contributed by Yuki Kobayashi in :gh:`127896`.)

.. Add C API deprecations above alphabetically, not here at the end.

* The ``PyMonitoring_FireBranchEvent`` function is deprecated and should
  be replaced with calls to :c:func:`PyMonitoring_FireBranchLeftEvent`
  and :c:func:`PyMonitoring_FireBranchRightEvent`.

* The following private functions are deprecated and planned for removal in
  Python 3.18:

  * :c:func:`!_PyBytes_Join`: use :c:func:`PyBytes_Join`.
  * :c:func:`!_PyDict_GetItemStringWithError`: use :c:func:`PyDict_GetItemStringRef`.
  * :c:func:`!_PyDict_Pop()`: use :c:func:`PyDict_Pop`.
  * :c:func:`!_PyLong_Sign()`: use :c:func:`PyLong_GetSign`.
  * :c:func:`!_PyLong_FromDigits` and :c:func:`!_PyLong_New`:
    use :c:func:`PyLongWriter_Create`.
  * :c:func:`!_PyThreadState_UncheckedGet`: use :c:func:`PyThreadState_GetUnchecked`.
  * :c:func:`!_PyUnicode_AsString`: use :c:func:`PyUnicode_AsUTF8`.
  * :c:func:`!_PyUnicodeWriter_Init`:
    replace ``_PyUnicodeWriter_Init(&writer)`` with
    :c:func:`writer = PyUnicodeWriter_Create(0) <PyUnicodeWriter_Create>`.
  * :c:func:`!_PyUnicodeWriter_Finish`:
    replace ``_PyUnicodeWriter_Finish(&writer)`` with
    :c:func:`PyUnicodeWriter_Finish(writer) <PyUnicodeWriter_Finish>`.
  * :c:func:`!_PyUnicodeWriter_Dealloc`:
    replace ``_PyUnicodeWriter_Dealloc(&writer)`` with
    :c:func:`PyUnicodeWriter_Discard(writer) <PyUnicodeWriter_Discard>`.
  * :c:func:`!_PyUnicodeWriter_WriteChar`:
    replace ``_PyUnicodeWriter_WriteChar(&writer, ch)`` with
    :c:func:`PyUnicodeWriter_WriteChar(writer, ch) <PyUnicodeWriter_WriteChar>`.
  * :c:func:`!_PyUnicodeWriter_WriteStr`:
    replace ``_PyUnicodeWriter_WriteStr(&writer, str)`` with
    :c:func:`PyUnicodeWriter_WriteStr(writer, str) <PyUnicodeWriter_WriteStr>`.
  * :c:func:`!_PyUnicodeWriter_WriteSubstring`:
    replace ``_PyUnicodeWriter_WriteSubstring(&writer, str, start, end)`` with
    :c:func:`PyUnicodeWriter_WriteSubstring(writer, str, start, end) <PyUnicodeWriter_WriteSubstring>`.
  * :c:func:`!_PyUnicodeWriter_WriteASCIIString`:
    replace ``_PyUnicodeWriter_WriteASCIIString(&writer, str)`` with
    :c:func:`PyUnicodeWriter_WriteUTF8(writer, str) <PyUnicodeWriter_WriteUTF8>`.
  * :c:func:`!_PyUnicodeWriter_WriteLatin1String`:
    replace ``_PyUnicodeWriter_WriteLatin1String(&writer, str)`` with
    :c:func:`PyUnicodeWriter_WriteUTF8(writer, str) <PyUnicodeWriter_WriteUTF8>`.
  * :c:func:`!_Py_HashPointer`: use :c:func:`Py_HashPointer`.
  * :c:func:`!_Py_fopen_obj`: use :c:func:`Py_fopen`.

  The `pythoncapi-compat project`_ can be used to get these new public
  functions on Python 3.13 and older.
  (Contributed by Victor Stinner in :gh:`128863`.)

.. include:: ../deprecations/c-api-pending-removal-in-3.15.rst

.. include:: ../deprecations/c-api-pending-removal-in-3.18.rst

.. include:: ../deprecations/c-api-pending-removal-in-future.rst


.. _whatsnew314-c-api-removed:

Removed
-------

* Creating :c:data:`immutable types <Py_TPFLAGS_IMMUTABLETYPE>` with mutable
  bases was deprecated since 3.12 and now raises a :exc:`TypeError`.

* Remove ``PyDictObject.ma_version_tag`` member which was deprecated since
  Python 3.12. Use the :c:func:`PyDict_AddWatcher` API instead.
  (Contributed by Sam Gross in :gh:`124296`.)

* Remove the private ``_Py_InitializeMain()`` function. It was a
  :term:`provisional API` added to Python 3.8 by :pep:`587`.
  (Contributed by Victor Stinner in :gh:`129033`.)
