cpython/Doc/whatsnew/3.12.rst

****************************
  What's New In Python 3.12
****************************

:Release: |release|
:Date: |today|

.. 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 bug/patch number as a comment:

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

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

This article explains the new features in Python 3.12, compared to 3.11.

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 3.12 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 3.12.
   Brevity is key.


.. PEP-sized items next.

Important deprecations, removals or restrictions:

* :pep:`623`, Remove wstr from Unicode


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



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



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

* None yet.


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


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

* Removed ``wstr`` and ``wstr_length`` members from Unicode objects.
  It reduces object size by 8 or 16 bytes on 64bit platform. (:pep:`623`)
  (Contributed by Inada Naoki in :gh:`92536`.)


Deprecated
==========



Removed
=======

* The following undocumented :mod:`sqlite3` features, deprecated in Python
  3.10, are now removed:

  * ``sqlite3.enable_shared_cache()``
  * ``sqlite3.OptimizedUnicode``

  (Contributed by Erlend E. Aasland in :gh:`92548`)


Porting to Python 3.12
======================

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

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

* 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`.)

* Removed randrange() functionality deprecated since Python 3.10.  Formerly,
  randrange(10.0) losslessly converted to randrange(10). Now, it raises a
  TypeError. Also, the exception raised for non-integral values such as
  randrange(10.5) or randrange('10') has been changed from ValueError to
  TypeError.  This also prevents bugs where ``randrange(1e25)`` would silently
  select from a larger range than ``randrange(10**25)``.
  (Originally suggested by Serhiy Storchaka gh-86388.)


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

* ``va_start()`` with two parameters, like ``va_start(args, format),``
  is now required to build Python.
  ``va_start()`` is no longer called with a single parameter.
  (Contributed by Kumar Aditya in :gh:`93207`.)


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

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

* Added the new limited C API function :c:func:`PyType_FromMetaclass`,
  which generalizes the existing :c:func:`PyType_FromModuleAndSpec` using
  an additional metaclass argument.
  (Contributed by Wenzel Jakob in :gh:`93012`.)

Porting to Python 3.12
----------------------

* Legacy Unicode APIs based on ``Py_UNICODE*`` representation has been removed.
  Please migrate to APIs based on UTF-8 or ``wchar_t*``.

* Argument parsing functions like :c:func:`PyArg_ParseTuple` doesn't support
  ``Py_UNICODE*`` based format (e.g. ``u``, ``Z``) anymore. Please migrate
  to other formats for Unicode like ``s``, ``z``, ``es``, and ``U``.

Deprecated
----------

Removed
-------

* Remove the ``token.h`` header file. There was never any public tokenizer C
  API. The ``token.h`` header file was only designed to be used by Python
  internals.
  (Contributed by Victor Stinner in :gh:`92651`.)

* Leagcy Unicode APIs has been removed. See :pep:`623` for detail.

   * :c:macro:`PyUnicode_WCHAR_KIND`
   * :c:func:`PyUnicode_AS_UNICODE`
   * :c:func:`PyUnicode_AsUnicode`
   * :c:func:`PyUnicode_AsUnicodeAndSize`
   * :c:func:`PyUnicode_AS_DATA`
   * :c:func:`PyUnicode_FromUnicode`
   * :c:func:`PyUnicode_GET_SIZE`
   * :c:func:`PyUnicode_GetSize`
   * :c:func:`PyUnicode_GET_DATA_SIZE`

* Remove the ``PyUnicode_InternImmortal()`` function and the
  ``SSTATE_INTERNED_IMMORTAL`` macro.
  (Contributed by Victor Stinner in :gh:`85858`.)