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

For full details, see the :ref:`changelog <changelog>`.

Important deprecations, removals or restrictions:

• PEP 623, Remove wstr from Unicode
• PEP 632, Remove the distutils package.

• 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'?

• 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`.)

• :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`.)

• None yet.

• The :class:`array.array` class now supports subscripting, making it a :term:`generic type`. (Contributed by Jelle Zijlstra in :gh:`98658`.)

• 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`.)

• 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`.)

• 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`.)

• 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`.)

• :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`.)

• 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`.)

• 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`.)

• The Unicode database has been updated to version 15.0.0. (Contributed by Benjamin Peterson in :gh:`96734`).

The :class:`tempfile.NamedTemporaryFile` function has a new optional parameter delete_on_close (Contributed by Evgeny Zorin in :gh:`58451`.)

• 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`.)

• 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`.)

• 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`.)

• Remove the Tools/demo/ directory which contained old demo scripts. A copy can be found in the old-demos project. (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. (Contributed by Victor Stinner in :gh:`97669`.)

• :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`.)

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`)

• 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`).

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`)

• 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`.)

• 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: 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. (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`.)

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

• 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`.)

• 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`.)

• 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`.)

• Add :c:macro:`Py_SETREF` and :c:macro:`Py_XSETREF` macros to the limited C API. (Contributed by Victor Stinner in :gh:`99574`.)

• 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`.)

• 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.)

• 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`.)