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****************************
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 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 3.12, 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
* :pep:`632`, Remove the ``distutils`` package.
Improved Error Messages
=======================
* Modules from the standard library are now potentially suggested as part of
the error messages displayed by the interpreter when a :exc:`NameError` is
raised to the top level. Contributed by Pablo Galindo in :gh:`98254`.
>>> sys.version_info
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'sys' is not defined. Did you forget to import 'sys'?
* Improve the error suggestion for :exc:`NameError` exceptions for instances.
Now if a :exc:`NameError` is raised in a method and the instance has an
attribute that's exactly equal to the name in the exception, the suggestion
will include ``self.<NAME>`` instead of the closest match in the method
scope. Contributed by Pablo Galindo in :gh:`99139`.
>>> class A:
... def __init__(self):
... self.blech = 1
...
... def foo(self):
... somethin = blech
>>> A().foo()
Traceback (most recent call last):
File "<stdin>", line 1
somethin = blech
^^^^^
NameError: name 'blech' is not defined. Did you mean: 'self.blech'?
* Improve the :exc:`SyntaxError` error message when the user types ``import x
from y`` instead of ``from y import x``. Contributed by Pablo Galindo in :gh:`98931`.
>>> import a.y.z from b.y.z
Traceback (most recent call last):
File "<stdin>", line 1
import a.y.z from b.y.z
^^^^^^^^^^^^^^^^^^^^^^^
SyntaxError: Did you mean to use 'from ... import ...' instead?
* :exc:`ImportError` exceptions raised from failed ``from <module> import
<name>`` statements now include suggestions for the value of ``<name>`` based on the
available names in ``<module>``. Contributed by Pablo Galindo in :gh:`91058`.
>>> from collections import chainmap
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: cannot import name 'chainmap' from 'collections'. Did you mean: 'ChainMap'?
New Features
============
* Add :ref:`perf_profiling` through the new
environment variable :envvar:`PYTHONPERFSUPPORT`,
the new command-line option :option:`-X perf <-X>`,
as well as the new :func:`sys.activate_stack_trampoline`,
:func:`sys.deactivate_stack_trampoline`,
and :func:`sys.is_stack_trampoline_active` APIs.
(Design by Pablo Galindo. Contributed by Pablo Galindo and Christian Heimes
with contributions from Gregory P. Smith [Google] and Mark Shannon
in :gh:`96123`.)
Other Language Changes
======================
* :class:`types.MappingProxyType` instances are now hashable if the underlying
mapping is hashable.
(Contributed by Serhiy Storchaka in :gh:`87995`.)
* :class:`memoryview` now supports the half-float type (the "e" format code).
(Contributed by Dong-hee Na and Antoine Pitrou in :gh:`90751`.)
* The parser now raises :exc:`SyntaxError` when parsing source code containing
null bytes. (Contributed by Pablo Galindo in :gh:`96670`.)
* :func:`ast.parse` now raises :exc:`SyntaxError` instead of :exc:`ValueError`
when parsing source code containing null bytes. (Contributed by Pablo Galindo
in :gh:`96670`.)
* The Garbage Collector now runs only on the eval breaker mechanism of the
Python bytecode evaluation loop instead on object allocations. The GC can
also run when :c:func:`PyErr_CheckSignals` is called so C extensions that
need to run for a long time without executing any Python code also have a
chance to execute the GC periodically. (Contributed by Pablo Galindo in
:gh:`97922`.)
* A backslash-character pair that is not a valid escape sequence now generates
a :exc:`SyntaxWarning`, instead of :exc:`DeprecationWarning`.
For example, ``re.compile("\d+\.\d+")`` now emits a :exc:`SyntaxWarning`
(``"\d"`` is an invalid escape sequence), use raw strings for regular
expression: ``re.compile(r"\d+\.\d+")``.
In a future Python version, :exc:`SyntaxError` will eventually be raised,
instead of :exc:`SyntaxWarning`.
(Contributed by Victor Stinner in :gh:`98401`.)
* Octal escapes with value larger than ``0o377`` (ex: ``"\477"``), deprecated
in Python 3.11, now produce a :exc:`SyntaxWarning`, instead of
:exc:`DeprecationWarning`.
In a future Python version they will be eventually a :exc:`SyntaxError`.
(Contributed by Victor Stinner in :gh:`98401`.)
* All builtin and extension callables expecting boolean parameters now accept
arguments of any type instead of just :class:`bool` and :class:`int`.
(Contributed by Serhiy Storchaka in :gh:`60203`.)
New Modules
===========
* None yet.
Improved Modules
================
array
-----
* The :class:`array.array` class now supports subscripting, making it a
:term:`generic type`. (Contributed by Jelle Zijlstra in :gh:`98658`.)
asyncio
-------
* On Linux, :mod:`asyncio` uses :class:`~asyncio.PidfdChildWatcher` by default
if :func:`os.pidfd_open` is available and functional instead of
:class:`~asyncio.ThreadedChildWatcher`.
(Contributed by Kumar Aditya in :gh:`98024`.)
* The child watcher classes :class:`~asyncio.MultiLoopChildWatcher`,
:class:`~asyncio.FastChildWatcher`, :class:`~asyncio.AbstractChildWatcher`
and :class:`~asyncio.SafeChildWatcher` are deprecated and
will be removed in Python 3.14. It is recommended to not manually
configure a child watcher as the event loop now uses the best available
child watcher for each platform (:class:`~asyncio.PidfdChildWatcher`
if supported and :class:`~asyncio.ThreadedChildWatcher` otherwise).
(Contributed by Kumar Aditya in :gh:`94597`.)
* :func:`asyncio.set_child_watcher`, :func:`asyncio.get_child_watcher`,
:meth:`asyncio.AbstractEventLoopPolicy.set_child_watcher` and
:meth:`asyncio.AbstractEventLoopPolicy.get_child_watcher` are deprecated
and will be removed in Python 3.14.
(Contributed by Kumar Aditya in :gh:`94597`.)
* Add *loop_factory* parameter to :func:`asyncio.run` to allow specifying
a custom event loop factory.
(Contributed by Kumar Aditya in :gh:`99388`.)
pathlib
-------
* Add :meth:`~pathlib.Path.walk` for walking the directory trees and generating
all file or directory names within them, similar to :func:`os.walk`.
(Contributed by Stanislav Zmiev in :gh:`90385`.)
* Add *walk_up* optional parameter to :meth:`pathlib.PurePath.relative_to`
to allow the insertion of ``..`` entries in the result; this behavior is
more consistent with :func:`os.path.relpath`.
(Contributed by Domenico Ragusa in :issue:`40358`.)
* Add :meth:`pathlib.Path.is_junction` as a proxy to :func:`os.path.isjunction`.
(Contributed by Charles Machalow in :gh:`99547`.)
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 instructions. 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`.)
* Add :func:`os.path.isjunction` to check if a given path is a junction.
(Contributed by Charles Machalow in :gh:`99547`.)
* :class:`os.DirEntry` now includes an :meth:`os.DirEntry.is_junction`
method to check if the entry is a junction.
(Contributed by Charles Machalow in :gh:`99547`.)
shutil
------
* :func:`shutil.make_archive` now passes the *root_dir* argument to custom
archivers which support it.
In this case it no longer temporarily changes the current working directory
of the process to *root_dir* to perform archiving.
(Contributed by Serhiy Storchaka in :gh:`74696`.)
sqlite3
-------
* Add a :ref:`command-line interface <sqlite3-cli>`.
(Contributed by Erlend E. Aasland in :gh:`77617`.)
* Add the :attr:`~sqlite3.Connection.autocommit` attribute
to :class:`~sqlite3.Connection`
and the *autocommit* parameter to :func:`~sqlite3.connect`
to control :pep:`249`-compliant
:ref:`transaction handling <sqlite3-transaction-control-autocommit>`.
(Contributed by Erlend E. Aasland in :gh:`83638`.)
threading
---------
* Add :func:`threading.settrace_all_threads` and
:func:`threading.setprofile_all_threads` that allow to set tracing and
profiling functions in all running threads in addition to the calling one.
(Contributed by Pablo Galindo in :gh:`93503`.)
unicodedata
-----------
* The Unicode database has been updated to version 15.0.0. (Contributed by
Benjamin Peterson in :gh:`96734`).
tempfile
--------
The :class:`tempfile.NamedTemporaryFile` function has a new optional parameter
*delete_on_close* (Contributed by Evgeny Zorin in :gh:`58451`.)
sys
---
* Add :func:`sys.activate_stack_trampoline` and
:func:`sys.deactivate_stack_trampoline` for activating and deactivating
stack profiler trampolines,
and :func:`sys.is_stack_trampoline_active` for querying if stack profiler
trampolines are active.
(Contributed by Pablo Galindo and Christian Heimes
with contributions from Gregory P. Smith [Google] and Mark Shannon
in :gh:`96123`.)
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`.)
* Added experimental support for using the BOLT binary optimizer in the build
process, which improves performance by 1-5%.
(Contributed by Kevin Modzelewski in :gh:`90536`.)
* Speed up the regular expression substitution (functions :func:`re.sub` and
:func:`re.subn` and corresponding :class:`re.Pattern` methods) for
replacement strings containing group references by 2--3 times.
(Contributed by Serhiy Storchaka in :gh:`91524`.)
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`.)
Demos and Tools
===============
* Remove the ``Tools/demo/`` directory which contained old demo scripts. A copy
can be found in the `old-demos project
<https://github.com/gvanrossum/old-demos>`_.
(Contributed by Victor Stinner in :gh:`97681`.)
* Remove outdated example scripts of the ``Tools/scripts/`` directory.
A copy can be found in the `old-demos project
<https://github.com/gvanrossum/old-demos>`_.
(Contributed by Victor Stinner in :gh:`97669`.)
Deprecated
==========
* :class:`typing.Hashable` and :class:`typing.Sized` aliases for :class:`collections.abc.Hashable`
and :class:`collections.abc.Sized`. (:gh:`94309`.)
* The :mod:`sqlite3` :ref:`default adapters and converters
<sqlite3-default-converters>` are now deprecated.
Instead, use the :ref:`sqlite3-adapter-converter-recipes`
and tailor them to your needs.
(Contributed by Erlend E. Aasland in :gh:`90016`.)
* The 3-arg signatures (type, value, traceback) of :meth:`~coroutine.throw`,
:meth:`~generator.throw` and :meth:`~agen.athrow` are deprecated and
may be removed in a future version of Python. Use the single-arg versions
of these functions instead. (Contributed by Ofey Chan in :gh:`89874`.)
* :exc:`DeprecationWarning` is now raised when ``__package__`` on a
module differs from ``__spec__.parent`` (previously it was
:exc:`ImportWarning`).
(Contributed by Brett Cannon in :gh:`65961`.)
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 Python 3.14
==============================
* Deprecated the following :mod:`importlib.abc` classes, scheduled for removal in
Python 3.14:
* :class:`importlib.abc.ResourceReader`
* :class:`importlib.abc.Traversable`
* :class:`importlib.abc.TraversableResources`
Use :mod:`importlib.resources.abc` classes instead:
* :class:`importlib.resources.abc.TraversableResources`
* :class:`importlib.resources.abc.Traversable`
* :class:`importlib.resources.abc.TraversableResources`
(Contributed by Jason R. Coombs and Hugo van Kemenade in :gh:`93963`.)
* Creating :c:data:`immutable types <Py_TPFLAGS_IMMUTABLETYPE>` with mutable
bases using the C API.
* ``__package__`` and ``__cached__`` will cease to be set or taken
into consideration by the import system (:gh:`97879`).
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
=======
* Remove the ``distutils`` package. It was deprecated in Python 3.10 by
:pep:`632` "Deprecate distutils module". For projects still using
``distutils`` and cannot be updated to something else, the ``setuptools``
project can be installed: it still provides ``distutils``.
(Contributed by Victor Stinner in :gh:`92584`.)
* 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`.)
* ``smtpd`` has been removed according to the schedule in :pep:`594`,
having been deprecated in Python 3.4.7 and 3.5.4.
Use aiosmtpd_ PyPI module or any other
:mod:`asyncio`-based server instead.
(Contributed by Oleg Iarygin in :gh:`93243`.)
.. _aiosmtpd: https://pypi.org/project/aiosmtpd/
* ``asynchat`` and ``asyncore`` have been removed
according to the schedule in :pep:`594`,
having been deprecated in Python 3.6.
Use :mod:`asyncio` instead.
(Contributed by Nikita Sobolev in :gh:`96580`.)
* 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`.)
* Remove the :func:`ssl.wrap_socket` function, deprecated in Python 3.7:
instead, create a :class:`ssl.SSLContext` object and call its
:class:`ssl.SSLContext.wrap_socket` method. Any package that still uses
:func:`ssl.wrap_socket` is broken and insecure. The function neither sends a
SNI TLS extension nor validates server hostname. Code is subject to `CWE-295
<https://cwe.mitre.org/data/definitions/295.html>`_: Improper Certificate
Validation.
(Contributed by Victor Stinner in :gh:`94199`.)
* Many previously deprecated cleanups in :mod:`importlib` have now been
completed:
* References to, and support for ``module_repr()`` has been eradicated.
* ``importlib.util.set_package`` has been removed.
(Contributed by Brett Cannon in :gh:`65961`.)
* Removed the ``suspicious`` rule from the documentation Makefile, and
removed ``Doc/tools/rstlint.py``, both in favor of `sphinx-lint
<https://github.com/sphinx-contrib/sphinx-lint>`_.
(Contributed by Julien Palard in :gh:`98179`.)
* Remove the *keyfile*, *certfile* and *check_hostname* parameters, deprecated
since Python 3.6, in modules: :mod:`ftplib`, :mod:`http.client`,
:mod:`imaplib`, :mod:`poplib` and :mod:`smtplib`. Use the *context* parameter
(*ssl_context* in :mod:`imaplib`) instead.
(Contributed by Victor Stinner in :gh:`94172`.)
* :mod:`ftplib`: Remove the ``FTP_TLS.ssl_version`` class attribute: use the
*context* parameter instead.
(Contributed by Victor Stinner in :gh:`94172`.)
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.
* Removed the ``asyncore``-based ``smtpd`` module deprecated in Python 3.4.7
and 3.5.4. A recommended replacement is the
:mod:`asyncio`-based aiosmtpd_ PyPI module.
* :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`.)
* The :mod:`os` module no longer accepts bytes-like paths, like
:class:`bytearray` and :class:`memoryview` types: only the exact
:class:`bytes` type is accepted for bytes strings.
(Contributed by Victor Stinner in :gh:`98393`.)
* :func:`syslog.openlog` and :func:`syslog.closelog` now fail if used in subinterpreters.
:func:`syslog.syslog` may still be used in subinterpreters,
but now only if :func:`syslog.openlog` has already been called in the main interpreter.
These new restrictions do not apply to the main interpreter,
so only a very small set of users might be affected.
This change helps with interpreter isolation. Furthermore, :mod:`syslog` is a wrapper
around process-global resources, which are best managed from the main interpreter.
(Contributed by Dong-hee Na in :gh:`99127`.)
* :func:`asyncio.get_event_loop` and many other :mod:`asyncio` functions like
:func:`~asyncio.ensure_future`, :func:`~asyncio.shield` or
:func:`~asyncio.gather`, and also the
:meth:`~asyncio.BaseDefaultEventLoopPolicy.get_event_loop` method of
:class:`~asyncio.BaseDefaultEventLoopPolicy` now raise a :exc:`RuntimeError`
if called when there is no running event loop and the current event loop was
not set.
Previously they implicitly created and set a new current event loop.
:exc:`DeprecationWarning` is no longer emitted if there is no running
event loop but the current event loop is set in the policy.
(Contributed by Serhiy Storchaka in :gh:`93453`.)
Build Changes
=============
* Python no longer uses ``setup.py`` to build shared C extension modules.
Build parameters like headers and libraries are detected in ``configure``
script. Extensions are built by ``Makefile``. Most extensions use
``pkg-config`` and fall back to manual detection.
(Contributed by Christian Heimes in :gh:`93939`.)
* ``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`.)
* CPython now uses the ThinLTO option as the default link time optimization policy
if the Clang compiler accepts the flag.
(Contributed by Dong-hee Na in :gh:`89536`.)
* Add ``COMPILEALL_OPTS`` variable in Makefile to override :mod:`compileall`
options (default: ``-j0``) in ``make install``. Also merged the 3
``compileall`` commands into a single command to build .pyc files for all
optimization levels (0, 1, 2) at once.
(Contributed by Victor Stinner in :gh:`99289`.)
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`.)
* API for creating objects that can be called using
:ref:`the vectorcall protocol <vectorcall>` was added to the
:ref:`Limited API <stable>`:
* :const:`Py_TPFLAGS_HAVE_VECTORCALL`
* :c:func:`PyVectorcall_NARGS`
* :c:func:`PyVectorcall_Call`
* :c:type:`vectorcallfunc`
The :const:`Py_TPFLAGS_HAVE_VECTORCALL` flag is now removed from a class
when the class's :py:meth:`~object.__call__` method is reassigned.
This makes vectorcall safe to use with mutable types (i.e. heap types
without the :const:`immutable <Py_TPFLAGS_IMMUTABLETYPE>` flag).
Mutable types that do not override :c:member:`~PyTypeObject.tp_call` now
inherit the ``Py_TPFLAGS_HAVE_VECTORCALL`` flag.
(Contributed by Petr Viktorin in :gh:`93274`.)
The :const:`Py_TPFLAGS_MANAGED_DICT` and :const:`Py_TPFLAGS_MANAGED_WEAKREF`
flags have been added. This allows extensions classes to support object
``__dict__`` and weakrefs with less bookkeeping,
using less memory and with faster access.
* API for performing calls using
:ref:`the vectorcall protocol <vectorcall>` was added to the
:ref:`Limited API <stable>`:
* :c:func:`PyObject_Vectorcall`
* :c:func:`PyObject_VectorcallMethod`
* :const:`PY_VECTORCALL_ARGUMENTS_OFFSET`
This means that both the incoming and outgoing ends of the vector call
protocol are now available in the :ref:`Limited API <stable>`. (Contributed
by Wenzel Jakob in :gh:`98586`.)
* Added two new public functions,
:c:func:`PyEval_SetProfileAllThreads` and
:c:func:`PyEval_SetTraceAllThreads`, that allow to set tracing and profiling
functions in all running threads in addition to the calling one. (Contributed
by Pablo Galindo in :gh:`93503`.)
* Added new function :c:func:`PyFunction_SetVectorcall` to the C API
which sets the vectorcall field of a given :c:type:`PyFunctionObject`.
(Contributed by Andrew Frost in :gh:`92257`.)
* The C API now permits registering callbacks via :c:func:`PyDict_AddWatcher`,
:c:func:`PyDict_AddWatch` and related APIs to be called whenever a dictionary
is modified. This is intended for use by optimizing interpreters, JIT
compilers, or debuggers.
(Contributed by Carl Meyer in :gh:`91052`.)
* Added :c:func:`PyType_AddWatcher` and :c:func:`PyType_Watch` API to register
callbacks to receive notification on changes to a type.
(Contributed by Carl Meyer in :gh:`91051`.)
* Added :c:func:`PyCode_AddWatcher` and :c:func:`PyCode_ClearWatcher`
APIs to register callbacks to receive notification on creation and
destruction of code objects.
(Contributed by Itamar Ostricher in :gh:`91054`.)
* Add :c:func:`PyFrame_GetVar` and :c:func:`PyFrame_GetVarString` functions to
get a frame variable by its name.
(Contributed by Victor Stinner in :gh:`91248`.)
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``.
* ``tp_weaklist`` for all static builtin types is always ``NULL``.
This is an internal-only field on ``PyTypeObject``
but we're pointing out the change in case someone happens to be
accessing the field directly anyway. To avoid breakage, consider
using the existing public C-API instead, or, if necessary, the
(internal-only) ``_PyObject_GET_WEAKREFS_LISTPTR()`` macro.
* This internal-only :c:member:`PyTypeObject.tp_subclasses` may now not be
a valid object pointer. Its type was changed to :c:expr:`void *` to
reflect this. We mention this in case someone happens to be accessing the
internal-only field directly.
To get a list of subclasses, call the Python method
:py:meth:`~class.__subclasses__` (using :c:func:`PyObject_CallMethod`,
for example).
* An unrecognized format character in :c:func:`PyUnicode_FromFormat` and
:c:func:`PyUnicode_FromFormatV` now sets a :exc:`SystemError`.
In previous versions it caused all the rest of the format string to be
copied as-is to the result string, and any extra arguments discarded.
(Contributed by Serhiy Storchaka in :gh:`95781`.)
* Fixed wrong sign placement in :c:func:`PyUnicode_FromFormat` and
:c:func:`PyUnicode_FromFormatV`.
(Contributed by Philip Georgi in :gh:`95504`.)
* Extension classes wanting to add a ``__dict__`` or weak reference slot
should use :const:`Py_TPFLAGS_MANAGED_DICT` and
:const:`Py_TPFLAGS_MANAGED_WEAKREF` instead of ``tp_dictoffset`` and
``tp_weaklistoffset``, respectively.
The use of ``tp_dictoffset`` and ``tp_weaklistoffset`` is still
supported, but does not fully support multiple inheritance
(:gh:`95589`), and performance may be worse.
Classes declaring :const:`Py_TPFLAGS_MANAGED_DICT` should call
:c:func:`_PyObject_VisitManagedDict` and :c:func:`_PyObject_ClearManagedDict`
to traverse and clear their instance's dictionaries.
To clear weakrefs, call :c:func:`PyObject_ClearWeakRefs`, as before.
* The :c:func:`PyUnicode_FSDecoder` function no longer accepts bytes-like
paths, like :class:`bytearray` and :class:`memoryview` types: only the exact
:class:`bytes` type is accepted for bytes strings.
(Contributed by Victor Stinner in :gh:`98393`.)
* The :c:macro:`Py_CLEAR`, :c:macro:`Py_SETREF` and :c:macro:`Py_XSETREF`
macros now only evaluate their arguments once. If an argument has side
effects, these side effects are no longer duplicated.
(Contributed by Victor Stinner in :gh:`98724`.)
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`.)
* Creating :c:data:`immutable types <Py_TPFLAGS_IMMUTABLETYPE>` with mutable
bases is deprecated and will be disabled in Python 3.14.
* The ``structmember.h`` header is deprecated, though it continues to be
available and there are no plans to remove it.
Its contents are now available just by including ``Python.h``,
with a ``Py`` prefix added if it was missing:
- :c:struct:`PyMemberDef`, :c:func:`PyMember_GetOne` and
:c:func:`PyMember_SetOne`
- Type macros like :c:macro:`Py_T_INT`, :c:macro:`Py_T_DOUBLE`, etc.
(previously ``T_INT``, ``T_DOUBLE``, etc.)
- The flags :c:macro:`Py_READONLY` (previously ``READONLY``) and
:c:macro:`Py_AUDIT_READ` (previously all uppercase)
Several items are not exposed from ``Python.h``:
- :c:macro:`T_OBJECT` (use :c:macro:`Py_T_OBJECT_EX`)
- :c:macro:`T_NONE` (previously undocumented, and pretty quirky)
- The macro ``WRITE_RESTRICTED`` which does nothing.
- The macros ``RESTRICTED`` and ``READ_RESTRICTED``, equivalents of
:c:macro:`Py_AUDIT_READ`.
- In some configurations, ``<stddef.h>`` is not included from ``Python.h``.
It should be included manually when using ``offsetof()``.
The deprecated header continues to provide its original
contents under the original names.
Your old code can stay unchanged, unless the extra include and non-namespaced
macros bother you greatly.
(Contributed in :gh:`47146` by Petr Viktorin, based on
earlier work by Alexander Belopolsky and Matthias Braun.)
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`.)
* Remove ``_use_broken_old_ctypes_structure_semantics_`` flag
from :mod:`ctypes` module.
(Contributed by Nikita Sobolev in :gh:`99285`.)
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