cpython/Doc/whatsnew/3.14.rst

****************************
  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.



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



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



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

* None yet.


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

ast
---

Added :func:`ast.compare` for comparing two ASTs.
(Contributed by Batuhan Taskaya and Jeremy Hylton in :issue:`15987`.)

os
--

* Added the :data:`os.environ.refresh() <os.environ>` method to update
  :data:`os.environ` 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`.)

pathlib
-------

* Add :meth:`pathlib.Path.copy`, which copies the content of one file to
  another, like :func:`shutil.copyfile`.
  (Contributed by Barney Gale in :gh:`73991`.)
* Add :meth:`pathlib.Path.copytree`, which copies one directory tree to
  another.
  (Contributed by Barney Gale in :gh:`73991`.)

symtable
--------

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

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

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


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




Deprecated
==========

* 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`.)


Removed
=======

argparse
--------

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

ast
---

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

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

  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
  ``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:

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

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


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*.

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.

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`.)

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`.)


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

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


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


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_Discard`.
  * :c:func:`PyUnicodeWriter_Finish`.
  * :c:func:`PyUnicodeWriter_WriteChar`.
  * :c:func:`PyUnicodeWriter_WriteUTF8`.
  * :c:func:`PyUnicodeWriter_WriteWideChar`.
  * :c:func:`PyUnicodeWriter_WriteStr`.
  * :c:func:`PyUnicodeWriter_WriteRepr`.
  * :c:func:`PyUnicodeWriter_WriteSubstring`.
  * :c:func:`PyUnicodeWriter_Format`.
  * :c:func:`PyUnicodeWriter_DecodeUTF8Stateful`.

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

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

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


Deprecated
----------

* 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`.)

Removed
-------

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