This article explains the new features in Python 3.13, compared to 3.12.

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

Important deprecations, removals or restrictions:

• :ref:`PEP 594 <whatsnew313-pep594>`: The remaining 19 "dead batteries" have been removed from the standard library: :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` and :mod:`!xdrlib`.
• PEP 602 ("Annual Release Cycle for Python") has been updated:
  • Python 3.9 - 3.12 have one and a half years of full support, followed by three and a half years of security fixes.
  • Python 3.13 and later have two years of full support, followed by three years of security fixes.

Interpreter improvements:

• A basic :ref:`JIT compiler <whatsnew313-jit-compiler>` was added. It is currently disabled by default (though we may turn it on later). Performance improvements are modest -- we expect to be improving this over the next few releases.

• The interpreter now colorizes error messages when displaying tracebacks by default. This feature can be controlled via the new :envvar:`PYTHON_COLORS` environment variable as well as the canonical NO_COLOR and FORCE_COLOR environment variables. See also :ref:`using-on-controlling-color`. (Contributed by Pablo Galindo Salgado in :gh:`112730`.)

• Allow the count argument of :meth:`str.replace` to be a keyword. (Contributed by Hugo van Kemenade in :gh:`106487`.)
• Compiler now strip indents from docstrings. This will reduce the size of :term:`bytecode cache <bytecode>` (e.g. .pyc file). For example, cache file size for sqlalchemy.orm.session in SQLAlchemy 2.0 is reduced by about 5%. This change will affect tools using docstrings, like :mod:`doctest`. (Contributed by Inada Naoki in :gh:`81283`.)
• The :func:`compile` built-in can now accept a new flag, ast.PyCF_OPTIMIZED_AST, which is similar to ast.PyCF_ONLY_AST except that the returned AST is optimized according to the value of the optimize argument. (Contributed by Irit Katriel in :gh:`108113`).
• :mod:`multiprocessing`, :mod:`concurrent.futures`, :mod:`compileall`: Replace :func:`os.cpu_count` with :func:`os.process_cpu_count` to select the default number of worker threads and processes. Get the CPU affinity if supported. (Contributed by Victor Stinner in :gh:`109649`.)
• :func:`os.path.realpath` now resolves MS-DOS style file names even if the file is not accessible. (Contributed by Moonsik Park in :gh:`82367`.)
• Fixed a bug where a :keyword:`global` declaration in an :keyword:`except` block is rejected when the global is used in the :keyword:`else` block. (Contributed by Irit Katriel in :gh:`111123`.)
• Many functions now emit a warning if a boolean value is passed as a file descriptor argument. This can help catch some errors earlier. (Contributed by Serhiy Storchaka in :gh:`82626`.)
• Added a new environment variable :envvar:`PYTHON_FROZEN_MODULES`. It determines whether or not frozen modules are ignored by the import machinery, equivalent of the :option:`-X frozen_modules <-X>` command-line option. (Contributed by Yilei Yang in :gh:`111374`.)
• The new :envvar:`PYTHON_HISTORY` environment variable can be used to change the location of a .python_history file. (Contributed by Levi Sabah, Zackery Spytz and Hugo van Kemenade in :gh:`73965`.)

• None yet.

• Add parameter deprecated in methods :meth:`~argparse.ArgumentParser.add_argument` and :meth:`!add_parser` which allows to deprecate command-line options, positional arguments and subcommands. (Contributed by Serhiy Storchaka in :gh:`83648`).

• Add 'w' type code (Py_UCS4) that can be used for Unicode strings. It can be used instead of 'u' type code, which is deprecated. (Contributed by Inada Naoki in :gh:`80480`.)

• :func:`ast.parse` now accepts an optional argument optimize which is passed on to the :func:`compile` built-in. This makes it possible to obtain an optimized AST. (Contributed by Irit Katriel in :gh:`108113`.)

• :meth:`asyncio.loop.create_unix_server` will now automatically remove the Unix socket when the server is closed. (Contributed by Pierre Ossman in :gh:`111246`.)

• Add :func:`copy.replace` function which allows to create a modified copy of an object, which is especially useful for immutable objects. It supports named tuples created with the factory function :func:`collections.namedtuple`, :class:`~dataclasses.dataclass` instances, various :mod:`datetime` objects, :class:`~inspect.Signature` objects, :class:`~inspect.Parameter` objects, :ref:`code object <code-objects>`, and any user classes which define the :meth:`!__replace__` method. (Contributed by Serhiy Storchaka in :gh:`108751`.)

• Add :meth:`dbm.gnu.gdbm.clear` and :meth:`dbm.ndbm.ndbm.clear` methods that remove all items from the database. (Contributed by Donghee Na in :gh:`107122`.)

• Change the output of :mod:`dis` module functions to show logical labels for jump targets and exception handlers, rather than offsets. The offsets can be added with the new -O command line option or the show_offsets parameter. (Contributed by Irit Katriel in :gh:`112137`.)

• The :meth:`doctest.DocTestRunner.run` method now counts the number of skipped tests. Add :attr:`doctest.DocTestRunner.skips` and :attr:`doctest.TestResults.skipped` attributes. (Contributed by Victor Stinner in :gh:`108794`.)

• :func:`email.utils.getaddresses` and :func:`email.utils.parseaddr` now return ('', '') 2-tuples in more situations where invalid email addresses are encountered instead of potentially inaccurate values. Add optional strict parameter to these two functions: use strict=False to get the old behavior, accept malformed inputs. getattr(email.utils, 'supports_strict_parsing', False) can be use to check if the strict parameter is available. (Contributed by Thomas Dwyer and Victor Stinner for :gh:`102988` to improve the CVE-2023-27043 fix.)

• Formatting for objects of type :class:`fractions.Fraction` now supports the standard format specification mini-language rules for fill, alignment, sign handling, minimum width and grouping. (Contributed by Mark Dickinson in :gh:`111320`.)

• Add :func:`glob.translate` function that converts a path specification with shell-style wildcards to a regular expression. (Contributed by Barney Gale in :gh:`72904`.)

The :class:`io.IOBase` finalizer now logs the close() method errors with :data:`sys.unraisablehook`. Previously, errors were ignored silently by default, and only logged in :ref:`Python Development Mode <devmode>` or on :ref:`Python built on debug mode <debug-build>`. (Contributed by Victor Stinner in :gh:`62948`.)

• Add the :attr:`ipaddress.IPv4Address.ipv6_mapped` property, which returns the IPv4-mapped IPv6 address. (Contributed by Charles Machalow in :gh:`109466`.)

• Add the allow_code parameter in module functions. Passing allow_code=False prevents serialization and de-serialization of code objects which are incompatible between Python versions. (Contributed by Serhiy Storchaka in :gh:`113626`.)

• The :class:`mmap.mmap` class now has an :meth:`~mmap.mmap.seekable` method that can be used when a seekable file-like object is required. The :meth:`~mmap.mmap.seek` method now returns the new absolute position. (Contributed by Donghee Na and Sylvie Liberman in :gh:`111835`.)
• :class:`mmap.mmap` now has a trackfd parameter on Unix; if it is False, the file descriptor specified by fileno will not be duplicated. (Contributed by Zackery Spytz and Petr Viktorin in :gh:`78502`.)

• Move opcode.ENABLE_SPECIALIZATION to _opcode.ENABLE_SPECIALIZATION. This field was added in 3.12, it was never documented and is not intended for external usage. (Contributed by Irit Katriel in :gh:`105481`.)
• Removed opcode.is_pseudo, opcode.MIN_PSEUDO_OPCODE and opcode.MAX_PSEUDO_OPCODE, which were added in 3.12, were never documented or exposed through dis, and were not intended to be used externally.

• Add :func:`os.process_cpu_count` function to get the number of logical CPUs usable by the calling thread of the current process. (Contributed by Victor Stinner in :gh:`109649`.)
• Add a low level interface for Linux's timer notification file descriptors via :func:`os.timerfd_create`, :func:`os.timerfd_settime`, :func:`os.timerfd_settime_ns`, :func:`os.timerfd_gettime`, and :func:`os.timerfd_gettime_ns`, :const:`os.TFD_NONBLOCK`, :const:`os.TFD_CLOEXEC`, :const:`os.TFD_TIMER_ABSTIME`, and :const:`os.TFD_TIMER_CANCEL_ON_SET` (Contributed by Masaru Tsuchiyama in :gh:`108277`.)
• :func:`os.cpu_count` and :func:`os.process_cpu_count` can be overridden through the new environment variable :envvar:`PYTHON_CPU_COUNT` or the new command-line option :option:`-X cpu_count <-X>`. This option is useful for users who need to limit CPU resources of a container system without having to modify the container (application code). (Contributed by Donghee Na in :gh:`109595`.)
• Add support of :func:`os.lchmod` and the follow_symlinks argument in :func:`os.chmod` on Windows. Note that the default value of follow_symlinks in :func:`!os.lchmod` is False on Windows. (Contributed by Serhiy Storchaka in :gh:`59616`.)
• Add support of :func:`os.fchmod` and a file descriptor in :func:`os.chmod` on Windows. (Contributed by Serhiy Storchaka in :gh:`113191`.)
• :func:`os.posix_spawn` now accepts env=None, which makes the newly spawned process use the current process environment. (Contributed by Jakub Kulik in :gh:`113119`.)
• :func:`os.posix_spawn` gains an :attr:`os.POSIX_SPAWN_CLOSEFROM` attribute for use in file_actions= on platforms that support :c:func:`!posix_spawn_file_actions_addclosefrom_np`. (Contributed by Jakub Kulik in :gh:`113117`.)

• Add :func:`os.path.isreserved` to check if a path is reserved on the current system. This function is only available on Windows. (Contributed by Barney Gale in :gh:`88569`.)
• On Windows, :func:`os.path.isabs` no longer considers paths starting with exactly one (back)slash to be absolute. (Contributed by Barney Gale and Jon Foster in :gh:`44626`.)

• Add :exc:`pathlib.UnsupportedOperation`, which is raised instead of :exc:`NotImplementedError` when a path operation isn't supported. (Contributed by Barney Gale in :gh:`89812`.)
• Add :meth:`pathlib.Path.from_uri`, a new constructor to create a :class:`pathlib.Path` object from a 'file' URI (file://). (Contributed by Barney Gale in :gh:`107465`.)
• Add :meth:`pathlib.PurePath.full_match` for matching paths with shell-style wildcards, including the recursive wildcard "**". (Contributed by Barney Gale in :gh:`73435`.)
• Add follow_symlinks keyword-only argument to :meth:`pathlib.Path.glob`, :meth:`~pathlib.Path.rglob`, :meth:`~pathlib.Path.is_file`, :meth:`~pathlib.Path.is_dir`, :meth:`~pathlib.Path.owner`, :meth:`~pathlib.Path.group`. (Contributed by Barney Gale in :gh:`77609` and :gh:`105793`, and Kamil Turek in :gh:`107962`).
• Return files and directories from :meth:`pathlib.Path.glob` and :meth:`~pathlib.Path.rglob` when given a pattern that ends with "**". In earlier versions, only directories were returned. (Contributed by Barney Gale in :gh:`70303`).

• Add ability to move between chained exceptions during post mortem debugging in :func:`~pdb.pm` using the new exceptions [exc_number] command for Pdb. (Contributed by Matthias Bussonnier in :gh:`106676`.)
• Expressions/statements whose prefix is a pdb command are now correctly identified and executed. (Contributed by Tian Gao in :gh:`108464`.)
• sys.path[0] will no longer be replaced by the directory of the script being debugged when sys.flags.safe_path is set (via the :option:`-P` command line option or :envvar:`PYTHONSAFEPATH` environment variable). (Contributed by Tian Gao and Christian Walther in :gh:`111762`.)

• Rename :exc:`!re.error` to :exc:`re.PatternError` for improved clarity. :exc:`!re.error` is kept for backward compatibility.

• A :exc:`ResourceWarning` is now emitted if a :class:`sqlite3.Connection` object is not :meth:`closed <sqlite3.Connection.close>` explicitly. (Contributed by Erlend E. Aasland in :gh:`105539`.)
• Add filter keyword-only parameter to :meth:`sqlite3.Connection.iterdump` for filtering database objects to dump. (Contributed by Mariusz Felisiak in :gh:`91602`.)

• The :mod:`subprocess` module now uses the :func:`os.posix_spawn` function in more situations. Notably in the default case of close_fds=True on more recent versions of platforms including Linux, FreeBSD, and Solaris where the C library provides :c:func:`!posix_spawn_file_actions_addclosefrom_np`. On Linux this should perform similar to our existing Linux :c:func:`!vfork` based code. A private control knob :attr:`!subprocess._USE_POSIX_SPAWN` can be set to False if you need to force :mod:`subprocess` not to ever use :func:`os.posix_spawn`. Please report your reason and platform details in the CPython issue tracker if you set this so that we can improve our API selection logic for everyone. (Contributed by Jakub Kulik in :gh:`113117`.)

• Add the :func:`sys._is_interned` function to test if the string was interned. This function is not guaranteed to exist in all implementations of Python. (Contributed by Serhiy Storchaka in :gh:`78573`.)

• Add :mod:`tkinter` widget methods: :meth:`!tk_busy_hold`, :meth:`!tk_busy_configure`, :meth:`!tk_busy_cget`, :meth:`!tk_busy_forget`, :meth:`!tk_busy_current`, and :meth:`!tk_busy_status`. (Contributed by Miguel, klappnase and Serhiy Storchaka in :gh:`72684`.)
• The :mod:`tkinter` widget method :meth:`!wm_attributes` now accepts the attribute name without the minus prefix to get window attributes, e.g. w.wm_attributes('alpha') and allows to specify attributes and values to set as keyword arguments, e.g. w.wm_attributes(alpha=0.5). Add new optional keyword-only parameter return_python_dict: calling w.wm_attributes(return_python_dict=True) returns the attributes as a dict instead of a tuple. (Contributed by Serhiy Storchaka in :gh:`43457`.)
• Add support of the "vsapi" element type in the :meth:`~tkinter.ttk.Style.element_create` method of :class:`tkinter.ttk.Style`. (Contributed by Serhiy Storchaka in :gh:`68166`.)

• Add show_group parameter to :func:`traceback.TracebackException.format_exception_only` to format the nested exceptions of a :exc:`BaseExceptionGroup` instance, recursively. (Contributed by Irit Katriel in :gh:`105292`.)
• Add the field exc_type_str to :class:`~traceback.TracebackException`, which holds a string display of the exc_type. Deprecate the field exc_type which holds the type object itself. Add parameter save_exc_type (default True) to indicate whether exc_type should be saved. (Contributed by Irit Katriel in :gh:`112332`.)

• Add :func:`typing.get_protocol_members` to return the set of members defining a :class:`typing.Protocol`. Add :func:`typing.is_protocol` to check whether a class is a :class:`typing.Protocol`. (Contributed by Jelle Zijlstra in :gh:`104873`.)

• The Unicode database has been updated to version 15.1.0. (Contributed by James Gerity in :gh:`109559`.)

• Add support for adding source control management (SCM) ignore files to a virtual environment's directory. By default, Git is supported. This is implemented as opt-in via the API which can be extended to support other SCMs (:class:`venv.EnvBuilder` and :func:`venv.create`), and opt-out via the CLI (using --without-scm-ignore-files). (Contributed by Brett Cannon in :gh:`108125`.)

• The new :func:`warnings.deprecated` decorator provides a way to communicate deprecations to :term:`static type checkers <static type checker>` and to warn on usage of deprecated classes and functions. A runtime deprecation warning may also be emitted when a decorated function or class is used at runtime. See PEP 702. (Contributed by Jelle Zijlstra in :gh:`104003`.)

• Add the :meth:`!close` method for the iterator returned by :func:`~xml.etree.ElementTree.iterparse` for explicit cleaning up. (Contributed by Serhiy Storchaka in :gh:`69893`.)

• :func:`textwrap.indent` is now ~30% faster than before for large input. (Contributed by Inada Naoki in :gh:`107369`.)
• The :mod:`subprocess` module uses :func:`os.posix_spawn` in more situations including the default where close_fds=True on many modern platforms. This should provide a noteworthy performance increase launching processes on FreeBSD and Solaris. See the subprocess section above for details. (Contributed by Jakub Kulik in :gh:`113117`.)

When CPython is configured using the --enable-experimental-jit option, a just-in-time compiler is added which can speed up some Python programs.

The internal architecture is roughly as follows.

• We start with specialized Tier 1 bytecode. See :ref:`What's new in 3.11 <whatsnew311-pep659>` for details.
• When the Tier 1 bytecode gets hot enough, it gets translated to a new, purely internal Tier 2 IR, a.k.a. micro-ops ("uops").
• The Tier 2 IR uses the same stack-based VM as Tier 1, but the instruction format is better suited to translation to machine code.
• We have several optimization passes for Tier 2 IR, which are applied before it is interpreted or translated to machine code.
• There is a Tier 2 interpreter, but it is mostly intended for debugging the earlier stages of the optimization pipeline. If the JIT is not enabled, the Tier 2 interpreter can be invoked by passing Python the -X uops option or by setting the PYTHON_UOPS environment variable to 1.
• When the --enable-experimental-jit option is used, the optimized Tier 2 IR is translated to machine code, which is then executed. This does not require additional runtime options.
• The machine code translation process uses an architecture called copy-and-patch. It has no runtime dependencies, but there is a new build-time dependency on LLVM.

(JIT by Brandt Bucher, inspired by a paper by Haoran Xu and Fredrik Kjolstad. Tier 2 IR by Mark Shannon and Guido van Rossum. Tier 2 optimizer by Ken Jin.)

• :mod:`array`: :mod:`array`'s 'u' format code, deprecated in docs since Python 3.3, emits :exc:`DeprecationWarning` since 3.13 and will be removed in Python 3.16. Use the 'w' format code instead. (contributed by Hugo van Kemenade in :gh:`80480`)

• :mod:`ctypes`: Deprecate undocumented :func:`!ctypes.SetPointerType` and :func:`!ctypes.ARRAY` functions. Replace ctypes.ARRAY(item_type, size) with item_type * size. (Contributed by Victor Stinner in :gh:`105733`.)

• :mod:`decimal`: Deprecate non-standard format specifier "N" for :class:`decimal.Decimal`. It was not documented and only supported in the C implementation. (Contributed by Serhiy Storchaka in :gh:`89902`.)

• :mod:`dis`: The dis.HAVE_ARGUMENT separator is deprecated. Check membership in :data:`~dis.hasarg` instead. (Contributed by Irit Katriel in :gh:`109319`.)

• :mod:`getopt` and :mod:`optparse` modules: They are now :term:`soft deprecated`: the :mod:`argparse` module should be used for new projects. Previously, the :mod:`optparse` module was already deprecated, its removal was not scheduled, and no warnings was emitted: so there is no change in practice. (Contributed by Victor Stinner in :gh:`106535`.)

• :mod:`gettext`: Emit deprecation warning for non-integer numbers in :mod:`gettext` functions and methods that consider plural forms even if the translation was not found. (Contributed by Serhiy Storchaka in :gh:`88434`.)

• :mod:`http.server`: :class:`http.server.CGIHTTPRequestHandler` now emits a :exc:`DeprecationWarning` as it will be removed in 3.15. Process-based CGI HTTP servers have been out of favor for a very long time. This code was outdated, unmaintained, and rarely used. It has a high potential for both security and functionality bugs. This includes removal of the --cgi flag to the python -m http.server command line in 3.15.

• :mod:`pathlib`: :meth:`pathlib.PurePath.is_reserved` is deprecated and scheduled for removal in Python 3.15. Use :func:`os.path.isreserved` to detect reserved paths on Windows.

• :mod:`pydoc`: Deprecate undocumented :func:`!pydoc.ispackage` function. (Contributed by Zackery Spytz in :gh:`64020`.)

• :mod:`sqlite3`: Passing more than one positional argument to :func:`sqlite3.connect` and the :class:`sqlite3.Connection` constructor is deprecated. The remaining parameters will become keyword-only in Python 3.15.

  Deprecate passing name, number of arguments, and the callable as keyword arguments for the following :class:`sqlite3.Connection` APIs:

  • :meth:`~sqlite3.Connection.create_function`
  • :meth:`~sqlite3.Connection.create_aggregate`

  Deprecate passing the callback callable by keyword for the following :class:`sqlite3.Connection` APIs:

  • :meth:`~sqlite3.Connection.set_authorizer`
  • :meth:`~sqlite3.Connection.set_progress_handler`
  • :meth:`~sqlite3.Connection.set_trace_callback`

  The affected parameters will become positional-only in Python 3.15.

  (Contributed by Erlend E. Aasland in :gh:`107948` and :gh:`108278`.)

• :mod:`sys`: :func:`sys._enablelegacywindowsfsencoding` function. Replace it with the :envvar:`PYTHONLEGACYWINDOWSFSENCODING` environment variable. (Contributed by Inada Naoki in :gh:`73427`.)

• :mod:`traceback`: The field exc_type of :class:`traceback.TracebackException` is deprecated. Use exc_type_str instead.

• :mod:`typing`:

  • Creating a :class:`typing.NamedTuple` class using keyword arguments to denote the fields (NT = NamedTuple("NT", x=int, y=int)) is deprecated, and will be disallowed in Python 3.15. Use the class-based syntax or the functional syntax instead. (Contributed by Alex Waygood in :gh:`105566`.)
  • When using the functional syntax to create a :class:`typing.NamedTuple` class or a :class:`typing.TypedDict` class, failing to pass a value to the 'fields' parameter (NT = NamedTuple("NT") or TD = TypedDict("TD")) is deprecated. Passing None to the 'fields' parameter (NT = NamedTuple("NT", None) or TD = TypedDict("TD", None)) is also deprecated. Both will be disallowed in Python 3.15. To create a NamedTuple class with 0 fields, use class NT(NamedTuple): pass or NT = NamedTuple("NT", []). To create a TypedDict class with 0 fields, use class TD(TypedDict): pass or TD = TypedDict("TD", {}). (Contributed by Alex Waygood in :gh:`105566` and :gh:`105570`.)
  • :func:`typing.no_type_check_decorator` is deprecated, and scheduled for removal in Python 3.15. After eight years in the :mod:`typing` module, it has yet to be supported by any major type checkers. (Contributed by Alex Waygood in :gh:`106309`.)
  • :data:`typing.AnyStr` is deprecated. In Python 3.16, it will be removed from typing.__all__, and a :exc:`DeprecationWarning` will be emitted when it is imported or accessed. It will be removed entirely in Python 3.18. Use the new :ref:`type parameter syntax <type-params>` instead. (Contributed by Michael The in :gh:`107116`.)

• :mod:`wave`: Deprecate the getmark(), setmark() and getmarkers() methods of the :class:`wave.Wave_read` and :class:`wave.Wave_write` classes. They will be removed in Python 3.15. (Contributed by Victor Stinner in :gh:`105096`.)

• Calling :meth:`frame.clear` on a suspended frame raises :exc:`RuntimeError` (as has always been the case for an executing frame). (Contributed by Irit Katriel in :gh:`79932`.)

• Assignment to a function's :attr:`~function.__code__` attribute where the new code object's type does not match the function's type, is deprecated. The different types are: plain function, generator, async generator and coroutine. (Contributed by Irit Katriel in :gh:`81137`.)

• :mod:`argparse`: The type, choices, and metavar parameters of :class:`!argparse.BooleanOptionalAction` are deprecated and will be removed in 3.14. (Contributed by Nikita Sobolev in :gh:`92248`.)

• :mod:`ast`: The following features have been deprecated in documentation since Python 3.8, now cause a :exc:`DeprecationWarning` to be emitted at runtime when they are accessed or used, and will be removed in Python 3.14:

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

  Use :class:`ast.Constant` instead. (Contributed by Serhiy Storchaka in :gh:`90953`.)

• :mod:`collections.abc`: Deprecated :class:`~collections.abc.ByteString`. Prefer :class:`!Sequence` or :class:`~collections.abc.Buffer`. For use in typing, prefer a union, like bytes | bytearray, or :class:`collections.abc.Buffer`. (Contributed by Shantanu Jain in :gh:`91896`.)

• :mod:`email`: Deprecated the isdst parameter in :func:`email.utils.localtime`. (Contributed by Alan Williams in :gh:`72346`.)

• :mod:`importlib`: __package__ and __cached__ will cease to be set or taken into consideration by the import system (:gh:`97879`).

• :mod:`importlib.abc` deprecated classes:

  • :class:`!importlib.abc.ResourceReader`
  • :class:`!importlib.abc.Traversable`
  • :class:`!importlib.abc.TraversableResources`

  Use :mod:`importlib.resources.abc` classes instead:

  • :class:`importlib.resources.abc.Traversable`
  • :class:`importlib.resources.abc.TraversableResources`

  (Contributed by Jason R. Coombs and Hugo van Kemenade in :gh:`93963`.)

• :mod:`itertools` had undocumented, inefficient, historically buggy, and inconsistent support for copy, deepcopy, and pickle operations. This will be removed in 3.14 for a significant reduction in code volume and maintenance burden. (Contributed by Raymond Hettinger in :gh:`101588`.)

• :mod:`multiprocessing`: The default start method will change to a safer one on Linux, BSDs, and other non-macOS POSIX platforms where 'fork' is currently the default (:gh:`84559`). Adding a runtime warning about this was deemed too disruptive as the majority of code is not expected to care. Use the :func:`~multiprocessing.get_context` or :func:`~multiprocessing.set_start_method` APIs to explicitly specify when your code requires 'fork'. See :ref:`multiprocessing-start-methods`.

• :mod:`pathlib`: :meth:`~pathlib.PurePath.is_relative_to` and :meth:`~pathlib.PurePath.relative_to`: passing additional arguments is deprecated.

• :mod:`pkgutil`: :func:`~pkgutil.find_loader` and :func:`~pkgutil.get_loader` now raise :exc:`DeprecationWarning`; use :func:`importlib.util.find_spec` instead. (Contributed by Nikita Sobolev in :gh:`97850`.)

• :mod:`pty`:

  • master_open(): use :func:`pty.openpty`.
  • slave_open(): use :func:`pty.openpty`.

• :func:`shutil.rmtree` onerror parameter is deprecated in 3.12, and will be removed in 3.14: use the onexc parameter instead.

• :mod:`sqlite3`:

  • :data:`~sqlite3.version` and :data:`~sqlite3.version_info`.
  • :meth:`~sqlite3.Cursor.execute` and :meth:`~sqlite3.Cursor.executemany` if :ref:`named placeholders <sqlite3-placeholders>` are used and parameters is a sequence instead of a :class:`dict`.
  • date and datetime adapter, date and timestamp converter: see the :mod:`sqlite3` documentation for suggested replacement recipes.

• :class:`types.CodeType`: Accessing :attr:`~codeobject.co_lnotab` was deprecated in PEP 626 since 3.10 and was planned to be removed in 3.12, but it only got a proper :exc:`DeprecationWarning` in 3.12. May be removed in 3.14. (Contributed by Nikita Sobolev in :gh:`101866`.)

• :mod:`typing`: :class:`~typing.ByteString`, deprecated since Python 3.9, now causes a :exc:`DeprecationWarning` to be emitted when it is used.

• :class:`!urllib.parse.Quoter` is deprecated: it was not intended to be a public API. (Contributed by Gregory P. Smith in :gh:`88168`.)

• :mod:`xml.etree.ElementTree`: Testing the truth value of an :class:`~xml.etree.ElementTree.Element` is deprecated and will raise an exception in Python 3.14.

• :class:`http.server.CGIHTTPRequestHandler` will be removed along with its related --cgi flag to python -m http.server. It was obsolete and rarely used. No direct replacement exists. Anything is better than CGI to interface a web server with a request handler.
• :class:`locale`: :func:`locale.getdefaultlocale` was deprecated in Python 3.11 and originally planned for removal in Python 3.13 (:gh:`90817`), but removal has been postponed to Python 3.15. Use :func:`locale.setlocale()`, :func:`locale.getencoding()` and :func:`locale.getlocale()` instead. (Contributed by Hugo van Kemenade in :gh:`111187`.)
• :mod:`pathlib`: :meth:`pathlib.PurePath.is_reserved` is deprecated and scheduled for removal in Python 3.15. Use :func:`os.path.isreserved` to detect reserved paths on Windows.
• :mod:`threading`: Passing any arguments to :func:`threading.RLock` is now deprecated. C version allows any numbers of args and kwargs, but they are just ignored. Python version does not allow any arguments. All arguments will be removed from :func:`threading.RLock` in Python 3.15. (Contributed by Nikita Sobolev in :gh:`102029`.)
• :class:`typing.NamedTuple`:
  • The undocumented keyword argument syntax for creating NamedTuple classes (NT = NamedTuple("NT", x=int)) is deprecated, and will be disallowed in 3.15. Use the class-based syntax or the functional syntax instead.
  • When using the functional syntax to create a NamedTuple class, failing to pass a value to the 'fields' parameter (NT = NamedTuple("NT")) is deprecated. Passing None to the 'fields' parameter (NT = NamedTuple("NT", None)) is also deprecated. Both will be disallowed in Python 3.15. To create a NamedTuple class with 0 fields, use class NT(NamedTuple): pass or NT = NamedTuple("NT", []).
• :class:`typing.TypedDict`: When using the functional syntax to create a TypedDict class, failing to pass a value to the 'fields' parameter (TD = TypedDict("TD")) is deprecated. Passing None to the 'fields' parameter (TD = TypedDict("TD", None)) is also deprecated. Both will be disallowed in Python 3.15. To create a TypedDict class with 0 fields, use class TD(TypedDict): pass or TD = TypedDict("TD", {}).
• :mod:`wave`: Deprecate the getmark(), setmark() and getmarkers() methods of the :class:`wave.Wave_read` and :class:`wave.Wave_write` classes. They will be removed in Python 3.15. (Contributed by Victor Stinner in :gh:`105096`.)

• :class:`array.array` 'u' type (:c:type:`wchar_t`): use the 'w' type instead (Py_UCS4).

The following APIs were deprecated in earlier Python versions and will be removed, although there is currently no date scheduled for their removal.

• :mod:`argparse`: Nesting argument groups and nesting mutually exclusive groups are deprecated.
• :mod:`builtins`:
  • ~bool, bitwise inversion on bool.
  • bool(NotImplemented).
  • Generators: throw(type, exc, tb) and athrow(type, exc, tb) signature is deprecated: use throw(exc) and athrow(exc) instead, the single argument signature.
  • 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`)
  • Support for __index__() and __int__() method returning non-int type: these methods will be required to return an instance of a strict subclass of :class:`int`.
  • Support for __float__() method returning a strict subclass of :class:`float`: these methods will be required to return an instance of :class:`float`.
  • Support for __complex__() method returning a strict subclass of :class:`complex`: these methods will be required to return an instance of :class:`complex`.
  • Delegation of int() to __trunc__() method.
• :mod:`calendar`: calendar.January and calendar.February constants are deprecated and replaced by :data:`calendar.JANUARY` and :data:`calendar.FEBRUARY`. (Contributed by Prince Roshan in :gh:`103636`.)
• :attr:`codeobject.co_lnotab`: use the :meth:`codeobject.co_lines` method instead.
• :mod:`datetime`:
  • :meth:`~datetime.datetime.utcnow`: use datetime.datetime.now(tz=datetime.UTC).
  • :meth:`~datetime.datetime.utcfromtimestamp`: use datetime.datetime.fromtimestamp(timestamp, tz=datetime.UTC).
• :mod:`gettext`: Plural value must be an integer.
• :mod:`importlib`:
  • load_module() method: use exec_module() instead.
  • :func:`~importlib.util.cache_from_source` debug_override parameter is deprecated: use the optimization parameter instead.
• :mod:`importlib.metadata`:
  • EntryPoints tuple interface.
  • Implicit None on return values.
• :mod:`mailbox`: Use of StringIO input and text mode is deprecated, use BytesIO and binary mode instead.
• :mod:`os`: Calling :func:`os.register_at_fork` in multi-threaded process.
• :class:`!pydoc.ErrorDuringImport`: A tuple value for exc_info parameter is deprecated, use an exception instance.
• :mod:`re`: 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`.)
• :mod:`!sre_compile`, :mod:`!sre_constants` and :mod:`!sre_parse` modules.
• :mod:`ssl` options and protocols:
  • :class:`ssl.SSLContext` without protocol argument is deprecated.
  • :class:`ssl.SSLContext`: :meth:`~ssl.SSLContext.set_npn_protocols` and :meth:`!selected_npn_protocol` are deprecated: use ALPN instead.
  • ssl.OP_NO_SSL* options
  • ssl.OP_NO_TLS* options
  • ssl.PROTOCOL_SSLv3
  • ssl.PROTOCOL_TLS
  • ssl.PROTOCOL_TLSv1
  • ssl.PROTOCOL_TLSv1_1
  • ssl.PROTOCOL_TLSv1_2
  • ssl.TLSVersion.SSLv3
  • ssl.TLSVersion.TLSv1
  • ssl.TLSVersion.TLSv1_1
• :func:`sysconfig.is_python_build` check_home parameter is deprecated and ignored.
• :mod:`threading` methods:
  • :meth:`!threading.Condition.notifyAll`: use :meth:`~threading.Condition.notify_all`.
  • :meth:`!threading.Event.isSet`: use :meth:`~threading.Event.is_set`.
  • :meth:`!threading.Thread.isDaemon`, :meth:`threading.Thread.setDaemon`: use :attr:`threading.Thread.daemon` attribute.
  • :meth:`!threading.Thread.getName`, :meth:`threading.Thread.setName`: use :attr:`threading.Thread.name` attribute.
  • :meth:`!threading.currentThread`: use :meth:`threading.current_thread`.
  • :meth:`!threading.activeCount`: use :meth:`threading.active_count`.
• :class:`typing.Text` (:gh:`92332`).
• :class:`unittest.IsolatedAsyncioTestCase`: it is deprecated to return a value that is not None from a test case.
• :mod:`urllib.parse` deprecated functions: :func:`~urllib.parse.urlparse` instead
  • splitattr()
  • splithost()
  • splitnport()
  • splitpasswd()
  • splitport()
  • splitquery()
  • splittag()
  • splittype()
  • splituser()
  • splitvalue()
  • to_bytes()
• :mod:`urllib.request`: :class:`~urllib.request.URLopener` and :class:`~urllib.request.FancyURLopener` style of invoking requests is deprecated. Use newer :func:`~urllib.request.urlopen` functions and methods.
• :mod:`wsgiref`: SimpleHandler.stdout.write() should not do partial writes.
• :meth:`zipimport.zipimporter.load_module` is deprecated: use :meth:`~zipimport.zipimporter.exec_module` instead.

• PEP 594 removed 19 modules from the standard library, deprecated in Python 3.11:

  • :mod:`!aifc`. (Contributed by Victor Stinner in :gh:`104773`.)

  • :mod:`!audioop`. (Contributed by Victor Stinner in :gh:`104773`.)

  • :mod:`!chunk`. (Contributed by Victor Stinner in :gh:`104773`.)

  • :mod:`!cgi` and :mod:`!cgitb`.

    • cgi.FieldStorage can typically be replaced with :func:`urllib.parse.parse_qsl` for GET and HEAD requests, and the :mod:`email.message` module or multipart PyPI project for POST and PUT.

    • cgi.parse() can be replaced by calling :func:`urllib.parse.parse_qs` directly on the desired query string, except for multipart/form-data input, which can be handled as described for cgi.parse_multipart().

    • cgi.parse_header() can be replaced with the functionality in the :mod:`email` package, which implements the same MIME RFCs. For example, with :class:`email.message.EmailMessage`:

      from email.message import EmailMessage
      msg = EmailMessage()
      msg['content-type'] = 'application/json; charset="utf8"'
      main, params = msg.get_content_type(), msg['content-type'].params
      

    • cgi.parse_multipart() can be replaced with the functionality in the :mod:`email` package (e.g. :class:`email.message.EmailMessage` and :class:`email.message.Message`) which implements the same MIME RFCs, or with the multipart PyPI project.

    (Contributed by Victor Stinner in :gh:`104773`.)

  • :mod:`!crypt` module and its private :mod:`!_crypt` extension. The :mod:`hashlib` module is a potential replacement for certain use cases. Otherwise, the following PyPI projects can be used:

    • bcrypt: Modern password hashing for your software and your servers.
    • passlib: Comprehensive password hashing framework supporting over 30 schemes.
    • argon2-cffi: The secure Argon2 password hashing algorithm.
    • legacycrypt: Wrapper to the POSIX crypt library call and associated functionality.

    (Contributed by Victor Stinner in :gh:`104773`.)

  • :mod:`!imghdr`: use the projects filetype, puremagic, or python-magic instead. (Contributed by Victor Stinner in :gh:`104773`.)

  • :mod:`!mailcap`. The :mod:`mimetypes` module provides an alternative. (Contributed by Victor Stinner in :gh:`104773`.)

  • :mod:`!msilib`. (Contributed by Zachary Ware in :gh:`104773`.)

  • :mod:`!nis`. (Contributed by Victor Stinner in :gh:`104773`.)

  • :mod:`!nntplib`: the PyPI nntplib project can be used instead. (Contributed by Victor Stinner in :gh:`104773`.)

  • :mod:`!ossaudiodev`: use the pygame project for audio playback. (Contributed by Victor Stinner in :gh:`104780`.)

  • :mod:`!pipes`: use the :mod:`subprocess` module instead. (Contributed by Victor Stinner in :gh:`104773`.)

  • :mod:`!sndhdr`: use the projects filetype, puremagic, or python-magic instead. (Contributed by Victor Stinner in :gh:`104773`.)

  • :mod:`!spwd`: the python-pam project can be used instead. (Contributed by Victor Stinner in :gh:`104773`.)

  • :mod:`!sunau`. (Contributed by Victor Stinner in :gh:`104773`.)

  • :mod:`!telnetlib`, use the projects telnetlib3 or Exscript instead. (Contributed by Victor Stinner in :gh:`104773`.)

  • :mod:`!uu`: the :mod:`base64` module is a modern alternative. (Contributed by Victor Stinner in :gh:`104773`.)

  • :mod:`!xdrlib`. (Contributed by Victor Stinner in :gh:`104773`.)

• Remove the 2to3 program and the :mod:`!lib2to3` module, deprecated in Python 3.11. (Contributed by Victor Stinner in :gh:`104780`.)

• Remove the undocumented :class:`!configparser.LegacyInterpolation` class, deprecated in the docstring since Python 3.2, and with a deprecation warning since Python 3.11. (Contributed by Hugo van Kemenade in :gh:`104886`.)

• Remove :mod:`importlib.resources` deprecated methods:

  • contents()
  • is_resource()
  • open_binary()
  • open_text()
  • path()
  • read_binary()
  • read_text()

  Use :func:`importlib.resources.files()` instead. Refer to importlib-resources: Migrating from Legacy for migration advice. (Contributed by Jason R. Coombs in :gh:`106532`.)

• Remove deprecated :meth:`~object.__getitem__` access for :class:`!importlib.metadata.EntryPoint` objects. (Contributed by Jason R. Coombs in :gh:`113175`.)

• Remove locale.resetlocale() function deprecated in Python 3.11: use locale.setlocale(locale.LC_ALL, "") instead. (Contributed by Victor Stinner in :gh:`104783`.)

• :mod:`logging`: Remove undocumented and untested Logger.warn() and LoggerAdapter.warn() methods and logging.warn() function. Deprecated since Python 3.3, they were aliases to the :meth:`logging.Logger.warning` method, :meth:`!logging.LoggerAdapter.warning` method and :func:`logging.warning` function. (Contributed by Victor Stinner in :gh:`105376`.)

• Remove support for using :class:`pathlib.Path` objects as context managers. This functionality was deprecated and made a no-op in Python 3.9.

• Remove undocumented, never working, and deprecated re.template function and re.TEMPLATE flag (and re.T alias). (Contributed by Serhiy Storchaka and Nikita Sobolev in :gh:`105687`.)

• Remove the :mod:`!tkinter.tix` module, deprecated in Python 3.6. The third-party Tix library which the module wrapped is unmaintained. (Contributed by Zachary Ware in :gh:`75552`.)

• Remove the :meth:`!turtle.RawTurtle.settiltangle` method, deprecated in docs since Python 3.1 and with a deprecation warning since Python 3.11. (Contributed by Hugo van Kemenade in :gh:`104876`.)

• Namespaces typing.io and typing.re, deprecated in Python 3.8, are now removed. The items in those namespaces can be imported directly from :mod:`typing`. (Contributed by Sebastian Rittau in :gh:`92871`.)
• Remove support for the keyword-argument method of creating :class:`typing.TypedDict` types, deprecated in Python 3.11. (Contributed by Tomas Roun in :gh:`104786`.)

• Removed the following :mod:`unittest` functions, deprecated in Python 3.11:

  • :func:`!unittest.findTestCases`
  • :func:`!unittest.makeSuite`
  • :func:`!unittest.getTestCaseNames`

  Use :class:`~unittest.TestLoader` methods instead:

  • :meth:`unittest.TestLoader.loadTestsFromModule`
  • :meth:`unittest.TestLoader.loadTestsFromTestCase`
  • :meth:`unittest.TestLoader.getTestCaseNames`

  (Contributed by Hugo van Kemenade in :gh:`104835`.)

• Remove the untested and undocumented :meth:`!unittest.TestProgram.usageExit` method, deprecated in Python 3.11. (Contributed by Hugo van Kemenade in :gh:`104992`.)

• Remove cafile, capath and cadefault parameters of the :func:`urllib.request.urlopen` function, deprecated in Python 3.6: use the context parameter instead. Please use :meth:`ssl.SSLContext.load_cert_chain` instead, or let :func:`ssl.create_default_context` select the system's trusted CA certificates for you. (Contributed by Victor Stinner in :gh:`105382`.)

• Remove the untested and undocumented :mod:`webbrowser` :class:`!MacOSX` class, deprecated in Python 3.11. Use the :class:`!MacOSXOSAScript` class (introduced in Python 3.2) instead. (Contributed by Hugo van Kemenade in :gh:`104804`.)
• Remove deprecated webbrowser.MacOSXOSAScript._name attribute. Use :attr:`webbrowser.MacOSXOSAScript.name <webbrowser.controller.name>` attribute instead. (Contributed by Nikita Sobolev in :gh:`105546`.)

• None yet

• The oparg of YIELD_VALUE is now 1 if the yield is part of a yield-from or await, and 0 otherwise. The oparg of RESUME was changed to add a bit indicating whether the except-depth is 1, which is needed to optimize closing of generators. (Contributed by Irit Katriel in :gh:`111354`.)

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

• :meth:`!tkinter.Text.count` now always returns an integer if one or less counting options are specified. Previously it could return a single count as a 1-tuple, an integer (only if option "update" was specified) or None if no items found. The result is now the same if wantobjects is set to 0. (Contributed by Serhiy Storchaka in :gh:`97928`.)

• Functions :c:func:`PyDict_GetItem`, :c:func:`PyDict_GetItemString`, :c:func:`PyMapping_HasKey`, :c:func:`PyMapping_HasKeyString`, :c:func:`PyObject_HasAttr`, :c:func:`PyObject_HasAttrString`, and :c:func:`PySys_GetObject`, which clear all errors which occurred when calling them, now report them using :func:`sys.unraisablehook`. You may replace them with other functions as recommended in the documentation. (Contributed by Serhiy Storchaka in :gh:`106672`.)

• An :exc:`OSError` is now raised by :func:`getpass.getuser` for any failure to retrieve a username, instead of :exc:`ImportError` on non-Unix platforms or :exc:`KeyError` on Unix platforms where the password database is empty.

• The :mod:`threading` module now expects the :mod:`!_thread` module to have an _is_main_interpreter attribute. It is a function with no arguments that return True if the current interpreter is the main interpreter.

  Any library or application that provides a custom _thread module must provide _is_main_interpreter(), just like the module's other "private" attributes. (See :gh:`112826`.)

• :class:`mailbox.Maildir` now ignores files with a leading dot. (Contributed by Zackery Spytz in :gh:`65559`.)

• :meth:`pathlib.Path.glob` and :meth:`~pathlib.Path.rglob` now return both files and directories if a pattern that ends with "**" is given, rather than directories only. Users may add a trailing slash to match only directories.

• Autoconf 2.71 and aclocal 1.16.4 is now required to regenerate the :file:`configure` script. (Contributed by Christian Heimes in :gh:`89886`.)
• SQLite 3.15.2 or newer is required to build the :mod:`sqlite3` extension module. (Contributed by Erlend Aasland in :gh:`105875`.)
• Python built with :file:`configure` :option:`--with-trace-refs` (tracing references) is now ABI compatible with the Python release build and :ref:`debug build <debug-build>`. (Contributed by Victor Stinner in :gh:`108634`.)
• Building CPython now requires a compiler with support for the C11 atomic library, GCC built-in atomic functions, or MSVC interlocked intrinsics.
• The errno, md5, resource, winsound, _ctypes_test, _multiprocessing.posixshmem, _scproxy, _stat, _testimportmultiple and _uuid C extensions are now built with the :ref:`limited C API <limited-c-api>`. (Contributed by Victor Stinner in :gh:`85283`.)

• You no longer have to define the PY_SSIZE_T_CLEAN macro before including :file:`Python.h` when using # formats in :ref:`format codes <arg-parsing-string-and-buffers>`. APIs accepting the format codes always use Py_ssize_t for # formats. (Contributed by Inada Naoki in :gh:`104922`.)

• The keywords parameter of :c:func:`PyArg_ParseTupleAndKeywords` and :c:func:`PyArg_VaParseTupleAndKeywords` now has type :c:expr:`char * const *` in C and :c:expr:`const char * const *` in C++, instead of :c:expr:`char **`. It makes these functions compatible with arguments of type :c:expr:`const char * const *`, :c:expr:`const char **` or :c:expr:`char * const *` in C++ and :c:expr:`char * const *` in C without an explicit type cast. This can be overridden with the :c:macro:`PY_CXX_CONST` macro. (Contributed by Serhiy Storchaka in :gh:`65210`.)

• Add :c:func:`PyImport_AddModuleRef`: similar to :c:func:`PyImport_AddModule`, but return a :term:`strong reference` instead of a :term:`borrowed reference`. (Contributed by Victor Stinner in :gh:`105922`.)

• Add :c:func:`PyWeakref_GetRef` function: similar to :c:func:`PyWeakref_GetObject` but returns a :term:`strong reference`, or NULL if the referent is no longer live. (Contributed by Victor Stinner in :gh:`105927`.)

• Add :c:func:`PyObject_GetOptionalAttr` and :c:func:`PyObject_GetOptionalAttrString`, variants of :c:func:`PyObject_GetAttr` and :c:func:`PyObject_GetAttrString` which don't raise :exc:`AttributeError` if the attribute is not found. These variants are more convenient and faster if the missing attribute should not be treated as a failure. (Contributed by Serhiy Storchaka in :gh:`106521`.)

• Add :c:func:`PyMapping_GetOptionalItem` and :c:func:`PyMapping_GetOptionalItemString`: variants of :c:func:`PyObject_GetItem` and :c:func:`PyMapping_GetItemString` which don't raise :exc:`KeyError` if the key is not found. These variants are more convenient and faster if the missing key should not be treated as a failure. (Contributed by Serhiy Storchaka in :gh:`106307`.)

• Add fixed variants of functions which silently ignore errors:

  • :c:func:`PyObject_HasAttrWithError` replaces :c:func:`PyObject_HasAttr`.
  • :c:func:`PyObject_HasAttrStringWithError` replaces :c:func:`PyObject_HasAttrString`.
  • :c:func:`PyMapping_HasKeyWithError` replaces :c:func:`PyMapping_HasKey`.
  • :c:func:`PyMapping_HasKeyStringWithError` replaces :c:func:`PyMapping_HasKeyString`.

  New functions return not only 1 for true and 0 for false, but also -1 for error.

  (Contributed by Serhiy Storchaka in :gh:`108511`.)

• If Python is built in :ref:`debug mode <debug-build>` or :option:`with assertions <--with-assertions>`, :c:func:`PyTuple_SET_ITEM` and :c:func:`PyList_SET_ITEM` now check the index argument with an assertion. (Contributed by Victor Stinner in :gh:`106168`.)

• Add :c:func:`PyModule_Add` function: similar to :c:func:`PyModule_AddObjectRef` and :c:func:`PyModule_AddObject` but always steals a reference to the value. (Contributed by Serhiy Storchaka in :gh:`86493`.)

• Add :c:func:`PyDict_GetItemRef` and :c:func:`PyDict_GetItemStringRef` functions: similar to :c:func:`PyDict_GetItemWithError` but returning a :term:`strong reference` instead of a :term:`borrowed reference`. Moreover, these functions return -1 on error and so checking PyErr_Occurred() is not needed. (Contributed by Victor Stinner in :gh:`106004`.)

• Added :c:func:`PyDict_SetDefaultRef`, which is similar to :c:func:`PyDict_SetDefault` but returns a :term:`strong reference` instead of a :term:`borrowed reference`. This function returns -1 on error, 0 on insertion, and 1 if the key was already present in the dictionary. (Contributed by Sam Gross in :gh:`112066`.)

• Add :c:func:`PyDict_ContainsString` function: same as :c:func:`PyDict_Contains`, but key is specified as a :c:expr:`const char*` UTF-8 encoded bytes string, rather than a :c:expr:`PyObject*`. (Contributed by Victor Stinner in :gh:`108314`.)

• Added :c:func:`PyList_GetItemRef` function: similar to :c:func:`PyList_GetItem` but returns a :term:`strong reference` instead of a :term:`borrowed reference`.

• Add :c:func:`Py_IsFinalizing` function: check if the main Python interpreter is :term:`shutting down <interpreter shutdown>`. (Contributed by Victor Stinner in :gh:`108014`.)

• Add :c:func:`PyLong_AsInt` function: similar to :c:func:`PyLong_AsLong`, but store the result in a C :c:expr:`int` instead of a C :c:expr:`long`. Previously, it was known as the private function :c:func:`!_PyLong_AsInt` (with an underscore prefix). (Contributed by Victor Stinner in :gh:`108014`.)

• Python built with :file:`configure` :option:`--with-trace-refs` (tracing references) now supports the :ref:`Limited API <limited-c-api>`. (Contributed by Victor Stinner in :gh:`108634`.)

• Add :c:func:`PyObject_VisitManagedDict` and :c:func:`PyObject_ClearManagedDict` functions which must be called by the traverse and clear functions of a type using :c:macro:`Py_TPFLAGS_MANAGED_DICT` flag. The pythoncapi-compat project can be used to get these functions on Python 3.11 and 3.12. (Contributed by Victor Stinner in :gh:`107073`.)

• Add :c:func:`PyUnicode_EqualToUTF8AndSize` and :c:func:`PyUnicode_EqualToUTF8` functions: compare Unicode object with a :c:expr:`const char*` UTF-8 encoded string and return true (1) if they are equal, or false (0) otherwise. These functions do not raise exceptions. (Contributed by Serhiy Storchaka in :gh:`110289`.)

• Add :c:func:`PyThreadState_GetUnchecked()` function: similar to :c:func:`PyThreadState_Get()`, but don't kill the process with a fatal error if it is NULL. The caller is responsible to check if the result is NULL. Previously, the function was private and known as _PyThreadState_UncheckedGet(). (Contributed by Victor Stinner in :gh:`108867`.)

• Add :c:func:`PySys_AuditTuple` function: similar to :c:func:`PySys_Audit`, but pass event arguments as a Python :class:`tuple` object. (Contributed by Victor Stinner in :gh:`85283`.)

• :c:func:`PyArg_ParseTupleAndKeywords` now supports non-ASCII keyword parameter names. (Contributed by Serhiy Storchaka in :gh:`110815`.)

• Add :c:func:`PyMem_RawMalloc`, :c:func:`PyMem_RawCalloc`, :c:func:`PyMem_RawRealloc` and :c:func:`PyMem_RawFree` to the limited C API (version 3.13). (Contributed by Victor Stinner in :gh:`85283`.)

• Add :c:func:`PySys_Audit` and :c:func:`PySys_AuditTuple` functions to the limited C API. (Contributed by Victor Stinner in :gh:`85283`.)

• Add :c:func:`PyErr_FormatUnraisable` function: similar to :c:func:`PyErr_WriteUnraisable`, but allow customizing the warning message. (Contributed by Serhiy Storchaka in :gh:`108082`.)

• Add :c:func:`PyList_Extend` and :c:func:`PyList_Clear` functions: similar to Python list.extend() and list.clear() methods. (Contributed by Victor Stinner in :gh:`111138`.)

• Add :c:func:`PyDict_Pop` and :c:func:`PyDict_PopString` functions: remove a key from a dictionary and optionally return the removed value. This is similar to :meth:`dict.pop`, but without the default value and not raising :exc:`KeyError` if the key is missing. (Contributed by Stefan Behnel and Victor Stinner in :gh:`111262`.)

• Add :c:func:`Py_HashPointer` function to hash a pointer. (Contributed by Victor Stinner in :gh:`111545`.)

• Python.h no longer includes the <ieeefp.h> standard header. It was included for the finite() function which is now provided by the <math.h> header. It should now be included explicitly if needed. Remove also the HAVE_IEEEFP_H macro. (Contributed by Victor Stinner in :gh:`108765`.)

• Python.h no longer includes these standard header files: <time.h>, <sys/select.h> and <sys/time.h>. If needed, they should now be included explicitly. For example, <time.h> provides the clock() and gmtime() functions, <sys/select.h> provides the select() function, and <sys/time.h> provides the futimes(), gettimeofday() and setitimer() functions. (Contributed by Victor Stinner in :gh:`108765`.)

• If the :c:macro:`Py_LIMITED_API` macro is defined, :c:macro:`!Py_BUILD_CORE`, :c:macro:`!Py_BUILD_CORE_BUILTIN` and :c:macro:`!Py_BUILD_CORE_MODULE` macros are now undefined by <Python.h>. (Contributed by Victor Stinner in :gh:`85283`.)

• The old trashcan macros Py_TRASHCAN_SAFE_BEGIN and Py_TRASHCAN_SAFE_END were removed. They should be replaced by the new macros Py_TRASHCAN_BEGIN and Py_TRASHCAN_END.

  A tp_dealloc function that has the old macros, such as:

  static void
  mytype_dealloc(mytype *p)
  {
      PyObject_GC_UnTrack(p);
      Py_TRASHCAN_SAFE_BEGIN(p);
      ...
      Py_TRASHCAN_SAFE_END
  }
  

  should migrate to the new macros as follows:

  static void
  mytype_dealloc(mytype *p)
  {
      PyObject_GC_UnTrack(p);
      Py_TRASHCAN_BEGIN(p, mytype_dealloc)
      ...
      Py_TRASHCAN_END
  }
  

  Note that Py_TRASHCAN_BEGIN has a second argument which should be the deallocation function it is in.

• On Windows, Python.h no longer includes the <stddef.h> standard header file. If needed, it should now be included explicitly. For example, it provides offsetof() function, and size_t and ptrdiff_t types. Including <stddef.h> explicitly was already needed by all other platforms, the HAVE_STDDEF_H macro is only defined on Windows. (Contributed by Victor Stinner in :gh:`108765`.)

• Passing optional arguments maxsplit, count and flags in module-level functions :func:`re.split`, :func:`re.sub` and :func:`re.subn` as positional arguments is now deprecated. In future Python versions these parameters will be :ref:`keyword-only <keyword-only_parameter>`. (Contributed by Serhiy Storchaka in :gh:`56166`.)

• Deprecate the old Py_UNICODE and PY_UNICODE_TYPE types: use directly the :c:type:`wchar_t` type instead. Since Python 3.3, Py_UNICODE and PY_UNICODE_TYPE are just aliases to :c:type:`wchar_t`. (Contributed by Victor Stinner in :gh:`105156`.)

• Deprecate old Python initialization functions:

  • :c:func:`PySys_ResetWarnOptions`: clear :data:`sys.warnoptions` and :data:`!warnings.filters` instead.
  • :c:func:`Py_GetExecPrefix`: get :data:`sys.exec_prefix` instead.
  • :c:func:`Py_GetPath`: get :data:`sys.path` instead.
  • :c:func:`Py_GetPrefix`: get :data:`sys.prefix` instead.
  • :c:func:`Py_GetProgramFullPath`: get :data:`sys.executable` instead.
  • :c:func:`Py_GetProgramName`: get :data:`sys.executable` instead.
  • :c:func:`Py_GetPythonHome`: get :c:member:`PyConfig.home` or :envvar:`PYTHONHOME` environment variable instead.

  Functions scheduled for removal in Python 3.15. (Contributed by Victor Stinner in :gh:`105145`.)

• Deprecate the :c:func:`PyImport_ImportModuleNoBlock` function which is just an alias to :c:func:`PyImport_ImportModule` since Python 3.3. Scheduled for removal in Python 3.15. (Contributed by Victor Stinner in :gh:`105396`.)

• Deprecate the :c:func:`PyWeakref_GetObject` and :c:func:`PyWeakref_GET_OBJECT` functions, which return a :term:`borrowed reference`: use the new :c:func:`PyWeakref_GetRef` function instead, it returns a :term:`strong reference`. The pythoncapi-compat project can be used to get :c:func:`PyWeakref_GetRef` on Python 3.12 and older. (Contributed by Victor Stinner in :gh:`105927`.)

• Removed chained :class:`classmethod` descriptors (introduced in :gh:`63272`). This can no longer be used to wrap other descriptors such as :class:`property`. The core design of this feature was flawed and caused a number of downstream problems. To "pass-through" a :class:`classmethod`, consider using the :attr:`!__wrapped__` attribute that was added in Python 3.10. (Contributed by Raymond Hettinger in :gh:`89519`.)

• Remove many APIs (functions, macros, variables) with names prefixed by _Py or _PY (considered as private API). If your project is affected by one of these removals and you consider that the removed API should remain available, please open a new issue to request a public C API and add cc @vstinner to the issue to notify Victor Stinner. (Contributed by Victor Stinner in :gh:`106320`.)

• Remove functions deprecated in Python 3.9:

  • PyEval_CallObject(), PyEval_CallObjectWithKeywords(): use :c:func:`PyObject_CallNoArgs` or :c:func:`PyObject_Call` instead. Warning: :c:func:`PyObject_Call` positional arguments must be a :class:`tuple` and must not be NULL, keyword arguments must be a :class:`dict` or NULL, whereas removed functions checked arguments type and accepted NULL positional and keyword arguments. To replace PyEval_CallObjectWithKeywords(func, NULL, kwargs) with :c:func:`PyObject_Call`, pass an empty tuple as positional arguments using :c:func:`PyTuple_New(0) <PyTuple_New>`.
  • PyEval_CallFunction(): use :c:func:`PyObject_CallFunction` instead.
  • PyEval_CallMethod(): use :c:func:`PyObject_CallMethod` instead.
  • PyCFunction_Call(): use :c:func:`PyObject_Call` instead.

  (Contributed by Victor Stinner in :gh:`105107`.)

• Remove old buffer protocols deprecated in Python 3.0. Use :ref:`bufferobjects` instead.

  • :c:func:`!PyObject_CheckReadBuffer`: Use :c:func:`PyObject_CheckBuffer` to test if the object supports the buffer protocol. Note that :c:func:`PyObject_CheckBuffer` doesn't guarantee that :c:func:`PyObject_GetBuffer` will succeed. To test if the object is actually readable, see the next example of :c:func:`PyObject_GetBuffer`.

  • :c:func:`!PyObject_AsCharBuffer`, :c:func:`!PyObject_AsReadBuffer`: :c:func:`PyObject_GetBuffer` and :c:func:`PyBuffer_Release` instead:

    Py_buffer view;
    if (PyObject_GetBuffer(obj, &view, PyBUF_SIMPLE) < 0) {
        return NULL;
    }
    // Use `view.buf` and `view.len` to read from the buffer.
    // You may need to cast buf as `(const char*)view.buf`.
    PyBuffer_Release(&view);

  • :c:func:`!PyObject_AsWriteBuffer`: Use :c:func:`PyObject_GetBuffer` and :c:func:`PyBuffer_Release` instead:

    Py_buffer view;
    if (PyObject_GetBuffer(obj, &view, PyBUF_WRITABLE) < 0) {
        return NULL;
    }
    // Use `view.buf` and `view.len` to write to the buffer.
    PyBuffer_Release(&view);

  (Contributed by Inada Naoki in :gh:`85275`.)

• Remove the following old functions to configure the Python initialization, deprecated in Python 3.11:

  • PySys_AddWarnOptionUnicode(): use :c:member:`PyConfig.warnoptions` instead.
  • PySys_AddWarnOption(): use :c:member:`PyConfig.warnoptions` instead.
  • PySys_AddXOption(): use :c:member:`PyConfig.xoptions` instead.
  • PySys_HasWarnOptions(): use :c:member:`PyConfig.xoptions` instead.
  • PySys_SetArgvEx(): set :c:member:`PyConfig.argv` instead.
  • PySys_SetArgv(): set :c:member:`PyConfig.argv` instead.
  • PySys_SetPath(): set :c:member:`PyConfig.module_search_paths` instead.
  • Py_SetPath(): set :c:member:`PyConfig.module_search_paths` instead.
  • Py_SetProgramName(): set :c:member:`PyConfig.program_name` instead.
  • Py_SetPythonHome(): set :c:member:`PyConfig.home` instead.
  • Py_SetStandardStreamEncoding(): set :c:member:`PyConfig.stdio_encoding` instead, and set also maybe :c:member:`PyConfig.legacy_windows_stdio` (on Windows).
  • _Py_SetProgramFullPath(): set :c:member:`PyConfig.executable` instead.

  Use the new :c:type:`PyConfig` API of the :ref:`Python Initialization Configuration <init-config>` instead (PEP 587), added to Python 3.8. (Contributed by Victor Stinner in :gh:`105145`.)

• Remove the old trashcan macros Py_TRASHCAN_SAFE_BEGIN and Py_TRASHCAN_SAFE_END. They should be replaced by the new macros Py_TRASHCAN_BEGIN and Py_TRASHCAN_END. The new macros were added in Python 3.8 and the old macros were deprecated in Python 3.11. (Contributed by Irit Katriel in :gh:`105111`.)

• Remove PyEval_InitThreads() and PyEval_ThreadsInitialized() functions, deprecated in Python 3.9. Since Python 3.7, Py_Initialize() always creates the GIL: calling PyEval_InitThreads() did nothing and PyEval_ThreadsInitialized() always returned non-zero. (Contributed by Victor Stinner in :gh:`105182`.)

• Remove PyEval_AcquireLock() and PyEval_ReleaseLock() functions, deprecated in Python 3.2. They didn't update the current thread state. They can be replaced with:

  • :c:func:`PyEval_SaveThread` and :c:func:`PyEval_RestoreThread`;
  • low-level :c:func:`PyEval_AcquireThread` and :c:func:`PyEval_RestoreThread`;
  • or :c:func:`PyGILState_Ensure` and :c:func:`PyGILState_Release`.

  (Contributed by Victor Stinner in :gh:`105182`.)

• Remove private _PyObject_FastCall() function: use PyObject_Vectorcall() which is available since Python 3.8 (PEP 590). (Contributed by Victor Stinner in :gh:`106023`.)

• Remove cpython/pytime.h header file: it only contained private functions. (Contributed by Victor Stinner in :gh:`106316`.)

• Remove _PyInterpreterState_Get() alias to :c:func:`PyInterpreterState_Get()` which was kept for backward compatibility with Python 3.8. The pythoncapi-compat project can be used to get :c:func:`PyInterpreterState_Get()` on Python 3.8 and older. (Contributed by Victor Stinner in :gh:`106320`.)

• The :c:func:`PyModule_AddObject` function is now :term:`soft deprecated`: :c:func:`PyModule_Add` or :c:func:`PyModule_AddObjectRef` functions should be used instead. (Contributed by Serhiy Storchaka in :gh:`86493`.)

• Creating immutable types (:c:macro:`Py_TPFLAGS_IMMUTABLETYPE`) with mutable bases using the C API.

• Global configuration variables:

  • :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:`PyPreConfig.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_HasFileSystemDefaultEncoding`: 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.

• :c:func:`PyImport_ImportModuleNoBlock`: use :c:func:`PyImport_ImportModule`.
• :c:func:`PyWeakref_GET_OBJECT`: use :c:func:`PyWeakref_GetRef` instead.
• :c:func:`PyWeakref_GetObject`: use :c:func:`PyWeakref_GetRef` instead.
• :c:type:`!Py_UNICODE_WIDE` type: use :c:type:`wchar_t` instead.
• :c:type:`Py_UNICODE` type: use :c:type:`wchar_t` instead.
• Python initialization functions:
  • :c:func:`PySys_ResetWarnOptions`: clear :data:`sys.warnoptions` and :data:`!warnings.filters` instead.
  • :c:func:`Py_GetExecPrefix`: get :data:`sys.exec_prefix` instead.
  • :c:func:`Py_GetPath`: get :data:`sys.path` instead.
  • :c:func:`Py_GetPrefix`: get :data:`sys.prefix` instead.
  • :c:func:`Py_GetProgramFullPath`: get :data:`sys.executable` instead.
  • :c:func:`Py_GetProgramName`: get :data:`sys.executable` instead.
  • :c:func:`Py_GetPythonHome`: get :c:member:`PyConfig.home` or :envvar:`PYTHONHOME` environment variable instead.

The following APIs were deprecated in earlier Python versions and will be removed, although there is currently no date scheduled for their removal.

• :c:macro:`Py_TPFLAGS_HAVE_FINALIZE`: no needed since Python 3.8.
• :c:func:`PyErr_Fetch`: use :c:func:`PyErr_GetRaisedException`.
• :c:func:`PyErr_NormalizeException`: use :c:func:`PyErr_GetRaisedException`.
• :c:func:`PyErr_Restore`: use :c:func:`PyErr_SetRaisedException`.
• :c:func:`PyModule_GetFilename`: use :c:func:`PyModule_GetFilenameObject`.
• :c:func:`PyOS_AfterFork`: use :c:func:`PyOS_AfterFork_Child()`.
• :c:func:`PySlice_GetIndicesEx`.
• :c:func:`!PyUnicode_AsDecodedObject`.
• :c:func:`!PyUnicode_AsDecodedUnicode`.
• :c:func:`!PyUnicode_AsEncodedObject`.
• :c:func:`!PyUnicode_AsEncodedUnicode`.
• :c:func:`PyUnicode_READY`: not needed since Python 3.12.
• :c:func:`!_PyErr_ChainExceptions`.
• :c:member:`!PyBytesObject.ob_shash` member: call :c:func:`PyObject_Hash` instead.
• :c:member:`!PyDictObject.ma_version_tag` member.
• TLS API:
  • :c:func:`PyThread_create_key`: use :c:func:`PyThread_tss_alloc`.
  • :c:func:`PyThread_delete_key`: use :c:func:`PyThread_tss_free`.
  • :c:func:`PyThread_set_key_value`: use :c:func:`PyThread_tss_set`.
  • :c:func:`PyThread_get_key_value`: use :c:func:`PyThread_tss_get`.
  • :c:func:`PyThread_delete_key_value`: use :c:func:`PyThread_tss_delete`.
  • :c:func:`PyThread_ReInitTLS`: no longer needed.
• Remove undocumented PY_TIMEOUT_MAX constant from the limited C API. (Contributed by Victor Stinner in :gh:`110014`.)

• Python built with :file:`configure` :option:`--with-pydebug` now supports a :option:`-X presite=package.module <-X>` command-line option. If used, it specifies a module that should be imported early in the lifecycle of the interpreter, before site.py is executed. (Contributed by Łukasz Langa in :gh:`110769`.)