path: root/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
======================

* :class:`types.MappingProxyType` instances are now hashable if the underlying
  mapping is hashable.
  (Contributed by Serhiy Storchaka in :gh:`87995`.)


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

* None yet.


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

dis
---

* Pseudo instruction opcodes (which are used by the compiler but
  do not appear in executable bytecode) are now exposed in the
  :mod:`dis` module.
  :data:`~dis.HAVE_ARGUMENT` is still relevant to real opcodes,
  but it is not useful for pseudo instrcutions. Use the new
  :data:`~dis.hasarg` collection instead.
  (Contributed by Irit Katriel in :gh:`94216`.)

os
--

* Add :data:`os.PIDFD_NONBLOCK` to open a file descriptor
  for a process with :func:`os.pidfd_open` in non-blocking mode.
  (Contributed by Kumar Aditya in :gh:`93312`.)


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`.)


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

* Removed the :opcode:`LOAD_METHOD` instruction. It has been merged into
  :opcode:`LOAD_ATTR`. :opcode:`LOAD_ATTR` will now behave like the old
  :opcode:`LOAD_METHOD` instruction if the low bit of its oparg is set.
  (Contributed by Ken Jin in :gh:`93429`.)


Deprecated
==========


Pending Removal in Python 3.13
==============================

The following modules and APIs have been deprecated in earlier Python releases,
and will be removed in Python 3.13.

Modules (see :pep:`594`):

* :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`
* :mod:`xdrlib`

APIs:

* :class:`configparser.LegacyInterpolation` (:gh:`90765`)
* :func:`locale.getdefaultlocale` (:gh:`90817`)
* :meth:`turtle.RawTurtle.settiltangle` (:gh:`50096`)
* :func:`unittest.findTestCases` (:gh:`50096`)
* :func:`unittest.makeSuite` (:gh:`50096`)
* :func:`unittest.getTestCaseNames` (:gh:`50096`)
* :class:`webbrowser.MacOSX` (:gh:`86421`)

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.

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

* 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`)


Removed
=======

* Removed many old deprecated :mod:`unittest` features:

  - A number of :class:`~unittest.TestCase` method aliases:

    ============================ =============================== ===============
       Deprecated alias           Method Name                     Deprecated in
    ============================ =============================== ===============
     ``failUnless``               :meth:`.assertTrue`             3.1
     ``failIf``                   :meth:`.assertFalse`            3.1
     ``failUnlessEqual``          :meth:`.assertEqual`            3.1
     ``failIfEqual``              :meth:`.assertNotEqual`         3.1
     ``failUnlessAlmostEqual``    :meth:`.assertAlmostEqual`      3.1
     ``failIfAlmostEqual``        :meth:`.assertNotAlmostEqual`   3.1
     ``failUnlessRaises``         :meth:`.assertRaises`           3.1
     ``assert_``                  :meth:`.assertTrue`             3.2
     ``assertEquals``             :meth:`.assertEqual`            3.2
     ``assertNotEquals``          :meth:`.assertNotEqual`         3.2
     ``assertAlmostEquals``       :meth:`.assertAlmostEqual`      3.2
     ``assertNotAlmostEquals``    :meth:`.assertNotAlmostEqual`   3.2
     ``assertRegexpMatches``      :meth:`.assertRegex`            3.2
     ``assertRaisesRegexp``       :meth:`.assertRaisesRegex`      3.2
     ``assertNotRegexpMatches``   :meth:`.assertNotRegex`         3.5
    ============================ =============================== ===============

    You can use https://github.com/isidentical/teyit to automatically modernise
    your unit tests.

  - Undocumented and broken :class:`~unittest.TestCase` method
    ``assertDictContainsSubset`` (deprecated in Python 3.2).

  - Undocumented :meth:`TestLoader.loadTestsFromModule
    <unittest.TestLoader.loadTestsFromModule>` parameter *use_load_tests*
    (deprecated and ignored since Python 3.2).

  - An alias of the :class:`~unittest.TextTestResult` class:
    ``_TextTestResult`` (deprecated in Python 3.2).

  (Contributed by Serhiy Storchaka in :issue:`45162`.)

* Several names deprecated in the :mod:`configparser` way back in 3.2 have
  been removed per :gh:`89336`:

  * :class:`configparser.ParsingError` no longer has a ``filename`` attribute
    or argument. Use the ``source`` attribute and argument instead.
  * :mod:`configparser` no longer has a ``SafeConfigParser`` class. Use the
    shorter :class:`~configparser.ConfigParser` name instead.
  * :class:`configparser.ConfigParser` no longer has a ``readfp`` method.
    Use :meth:`~configparser.ConfigParser.read_file` instead.

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

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

  If a shared cache must be used, open the database in URI mode using the
  ``cache=shared`` query parameter.

  The ``sqlite3.OptimizedUnicode`` text factory has been an alias for
  :class:`str` since Python 3.3. Code that previously set the text factory to
  ``OptimizedUnicode`` can either use ``str`` explicitly, or rely on the
  default value which is also ``str``.

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

* The ``--experimental-isolated-subinterpreters`` configure flag
  (and corresponding ``EXPERIMENTAL_ISOLATED_SUBINTERPRETERS``)
  have been removed.

* Remove ``io.OpenWrapper`` and ``_pyio.OpenWrapper``, deprecated in Python
  3.10: just use :func:`open` instead. The :func:`open` (:func:`io.open`)
  function is a built-in function. Since Python 3.10, :func:`_pyio.open` is
  also a static method.
  (Contributed by Victor Stinner in :gh:`94169`.)

* Remove the :func:`ssl.RAND_pseudo_bytes` function, deprecated in Python 3.6:
  use :func:`os.urandom` or :func:`ssl.RAND_bytes` instead.
  (Contributed by Victor Stinner in :gh:`94199`.)

* :mod:`gzip`: Remove the ``filename`` attribute of :class:`gzip.GzipFile`,
  deprecated since Python 2.6, use the :attr:`~gzip.GzipFile.name` attribute
  instead. In write mode, the ``filename`` attribute added ``'.gz'`` file
  extension if it was not present.
  (Contributed by Victor Stinner in :gh:`94196`.)

* Remove the :func:`ssl.match_hostname` function. The
  :func:`ssl.match_hostname` was deprecated in Python 3.7. OpenSSL performs
  hostname matching since Python 3.7, Python no longer uses the
  :func:`ssl.match_hostname` function.
  (Contributed by Victor Stinner in :gh:`94199`.)

* Remove the :func:`locale.format` function, deprecated in Python 3.7:
  use :func:`locale.format_string` instead.
  (Contributed by Victor Stinner in :gh:`94226`.)

* :mod:`hashlib`: Remove the pure Python implementation of
  :func:`hashlib.pbkdf2_hmac()`, deprecated in Python 3.10. Python 3.10 and
  newer requires OpenSSL 1.1.1 (:pep:`644`): this OpenSSL version provides
  a C implementation of :func:`~hashlib.pbkdf2_hmac()` which is faster.
  (Contributed by Victor Stinner in :gh:`94199`.)

* :mod:`xml.etree`: Remove the ``ElementTree.Element.copy()`` method of the
  pure Python implementation, deprecated in Python 3.10, use the
  :func:`copy.copy` function instead.  The C implementation of :mod:`xml.etree`
  has no ``copy()`` method, only a ``__copy__()`` method.
  (Contributed by Victor Stinner in :gh:`94383`.)

* :mod:`zipimport`: Remove ``find_loader()`` and ``find_module()`` methods,
  deprecated in Python 3.10: use the ``find_spec()`` method instead.  See
  :pep:`451` for the rationale.
  (Contributed by Victor Stinner in :gh:`94379`.)


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.)

* :class:`argparse.ArgumentParser` changed encoding and error handler
  for reading arguments from file (e.g. ``fromfile_prefix_chars`` option)
  from default text encoding (e.g. :func:`locale.getpreferredencoding(False) <locale.getpreferredencoding>`)
  to :term:`filesystem encoding and error handler`.
  Argument files should be encoded in UTF-8 instead of ANSI Codepage on Windows.

* :func:`shlex.split`: Passing ``None`` for *s* argument now raises an
  exception, rather than reading :data:`sys.stdin`. The feature was deprecated
  in Python 3.9.
  (Contributed by Victor Stinner in :gh:`94352`.)


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
----------

* Deprecate global configuration variable:

  * :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:`PyConfig.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_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.
  (Contributed by Victor Stinner in :gh:`77782`.)


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`.)