# What’s New In Python 3.13

Editor:

  TBD

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

For full details, see the changelog.

Note

Prerelease users should be aware that this document is currently in draft form. It will be updated substantially as Python 3.13 moves towards release, so it’s worth checking back even after reading earlier versions.

## Summary – Release highlights

Important deprecations, removals or restrictions:

- PEP 594: The remaining 19 “dead batteries” have been removed from the standard library: `aifc`, `audioop`, `cgi`, `cgitb`, `chunk`, `crypt`, `imghdr`, `mailcap`, `msilib`, `nis`, `nntplib`, `ossaudiodev`, `pipes`, `sndhdr`, `spwd`, `sunau`, `telnetlib`, `uu` and `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 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.

## New Features

### Improved Error Messages

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

- When an incorrect keyword argument is passed to a function, the error message now potentially suggests the correct keyword argument. (Contributed by Pablo Galindo Salgado and Shantanu Jain in gh-107944.)

      >>> "better error messages!".split(max_split=1)
      Traceback (most recent call last):
        File "<stdin>", line 1, in <module>
          "better error messages!".split(max_split=1)
          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
      TypeError: split() got an unexpected keyword argument 'max_split'. Did you mean 'maxsplit'?

## Other Language Changes

- Allow the count argument of `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 bytecode cache (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 `doctest`. (Contributed by Inada Naoki in gh-81283.)

- The `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).

- `multiprocessing`, `concurrent.futures`, `compileall`: Replace `os.cpu_count()` with `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.)

- `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 `global` declaration in an `except` block is rejected when the global is used in the `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 `PYTHON_FROZEN_MODULES`. It determines whether or not frozen modules are ignored by the import machinery, equivalent of the `-X frozen_modules` command-line option. (Contributed by Yilei Yang in gh-111374.)

- The new `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.)

## New Modules

- None yet.

## Improved Modules

### argparse

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

### array

- 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.)

- Add `clear()` method in order to implement `MutableSequence`. (Contributed by Mike Zimin in gh-114894.)

### ast

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

### asyncio

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

### copy

- Add `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 `collections.namedtuple()`, `dataclass` instances, various `datetime` objects, `Signature` objects, `Parameter` objects, code object, and any user classes which define the `__replace__()` method. (Contributed by Serhiy Storchaka in gh-108751.)

### dbm

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

### dis

- Change the output of `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.)

### dbm

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

- Add new `dbm.sqlite3` backend, and make it the default `dbm` backend. (Contributed by Raymond Hettinger and Erlend E. Aasland in gh-100414.)

### doctest

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

### email

- `email.utils.getaddresses()` and `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.)

### fractions

- Formatting for objects of type `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.)

### glob

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

### io

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

### ipaddress

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

### marshal

- 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.)

### mmap

- The `mmap.mmap` class now has an `seekable()` method that can be used when a seekable file-like object is required. The `seek()` method now returns the new absolute position. (Contributed by Donghee Na and Sylvie Liberman in gh-111835.)

- `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.)

### opcode

- 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.

### os

- Add `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 `os.timerfd_create()`, `os.timerfd_settime()`, `os.timerfd_settime_ns()`, `os.timerfd_gettime()`, and `os.timerfd_gettime_ns()`, `os.TFD_NONBLOCK`, `os.TFD_CLOEXEC`, `os.TFD_TIMER_ABSTIME`, and `os.TFD_TIMER_CANCEL_ON_SET` (Contributed by Masaru Tsuchiyama in gh-108277.)

- `os.cpu_count()` and `os.process_cpu_count()` can be overridden through the new environment variable `PYTHON_CPU_COUNT` or the new command-line option `-X cpu_count`. 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 `os.lchmod()` and the follow_symlinks argument in `os.chmod()` on Windows. Note that the default value of follow_symlinks in `os.lchmod()` is `False` on Windows. (Contributed by Serhiy Storchaka in gh-59616.)

- Add support of `os.fchmod()` and a file descriptor in `os.chmod()` on Windows. (Contributed by Serhiy Storchaka in gh-113191.)

- `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.)

- `os.posix_spawn()` gains an `os.POSIX_SPAWN_CLOSEFROM` attribute for use in `file_actions=` on platforms that support `posix_spawn_file_actions_addclosefrom_np()`. (Contributed by Jakub Kulik in gh-113117.)

### os.path

- Add `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, `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.)

### pathlib

- Add `pathlib.UnsupportedOperation`, which is raised instead of `NotImplementedError` when a path operation isn’t supported. (Contributed by Barney Gale in gh-89812.)

- Add `pathlib.Path.from_uri()`, a new constructor to create a `pathlib.Path` object from a ‘file’ URI (`file://`). (Contributed by Barney Gale in gh-107465.)

- Add `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 `pathlib.Path.glob()`, `rglob()`, `is_file()`, `is_dir()`, `owner()`, `group()`. (Contributed by Barney Gale in gh-77609 and gh-105793, and Kamil Turek in gh-107962).

- Return files and directories from `pathlib.Path.glob()` and `rglob()` when given a pattern that ends with “`**`”. In earlier versions, only directories were returned. (Contributed by Barney Gale in gh-70303).

### pdb

- Add ability to move between chained exceptions during post mortem debugging in `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 `-P` command line option or `PYTHONSAFEPATH` environment variable). (Contributed by Tian Gao and Christian Walther in gh-111762.)

### queue

- Add `queue.Queue.shutdown()` (along with `queue.ShutDown`) for queue termination. (Contributed by Laurie Opperman and Yves Duprat in gh-104750.)

### re

- Rename `re.error` to `re.PatternError` for improved clarity. `re.error` is kept for backward compatibility.

### sqlite3

- A `ResourceWarning` is now emitted if a `sqlite3.Connection` object is not `closed` explicitly. (Contributed by Erlend E. Aasland in gh-105539.)

- Add filter keyword-only parameter to `sqlite3.Connection.iterdump()` for filtering database objects to dump. (Contributed by Mariusz Felisiak in gh-91602.)

### subprocess

- The `subprocess` module now uses the `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 `posix_spawn_file_actions_addclosefrom_np()`. On Linux this should perform similar to our existing Linux `vfork()` based code. A private control knob `subprocess._USE_POSIX_SPAWN` can be set to `False` if you need to force `subprocess` not to ever use `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.)

### sys

- Add the `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.)

### tkinter

- Add `tkinter` widget methods: `tk_busy_hold()`, `tk_busy_configure()`, `tk_busy_cget()`, `tk_busy_forget()`, `tk_busy_current()`, and `tk_busy_status()`. (Contributed by Miguel, klappnase and Serhiy Storchaka in gh-72684.)

- The `tkinter` widget method `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 new optional keyword-only parameter return_ints in the `Text.count()` method. Passing `return_ints=True` makes it always returning the single count as an integer instead of a 1-tuple or `None`. (Contributed by Serhiy Storchaka in gh-97928.)

- Add support of the “vsapi” element type in the `element_create()` method of `tkinter.ttk.Style`. (Contributed by Serhiy Storchaka in gh-68166.)

### traceback

- Add show_group parameter to `traceback.TracebackException.format_exception_only()` to format the nested exceptions of a `BaseExceptionGroup` instance, recursively. (Contributed by Irit Katriel in gh-105292.)

- Add the field exc_type_str to `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.)

### typing

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

### unicodedata

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

### venv

- 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 (`venv.EnvBuilder` and `venv.create()`), and opt-out via the CLI (using `--without-scm-ignore-files`). (Contributed by Brett Cannon in gh-108125.)

### warnings

- The new `warnings.deprecated()` decorator provides a way to communicate deprecations to static type checkers 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.)

### xml.etree.ElementTree

- Add the `close()` method for the iterator returned by `iterparse()` for explicit cleaning up. (Contributed by Serhiy Storchaka in gh-69893.)

## Optimizations

- `textwrap.indent()` is now ~30% faster than before for large input. (Contributed by Inada Naoki in gh-107369.)

- The `subprocess` module uses `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.)

## Experimental JIT Compiler

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 What’s new in 3.11 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.)

## Deprecated

- `array`: `array`’s `'u'` format code, deprecated in docs since Python 3.3, emits `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)

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

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

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

- `getopt` and `optparse` modules: They are now soft deprecated: the `argparse` module should be used for new projects. Previously, the `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.)

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

- `http.server`: `http.server.CGIHTTPRequestHandler` now emits a `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.

- `pathlib`: `pathlib.PurePath.is_reserved()` is deprecated and scheduled for removal in Python 3.15. Use `os.path.isreserved()` to detect reserved paths on Windows.

- `pydoc`: Deprecate undocumented `pydoc.ispackage()` function. (Contributed by Zackery Spytz in gh-64020.)

- `sqlite3`: Passing more than one positional argument to `sqlite3.connect()` and the `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 `sqlite3.Connection` APIs:

  - `create_function()`

  - `create_aggregate()`

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

  - `set_authorizer()`

  - `set_progress_handler()`

  - `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.)

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

- `traceback`: The field exc_type of `traceback.TracebackException` is deprecated. Use exc_type_str instead.

- `typing`:

  - Creating a `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 `typing.NamedTuple` class or a `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.)

  - `typing.no_type_check_decorator()` is deprecated, and scheduled for removal in Python 3.15. After eight years in the `typing` module, it has yet to be supported by any major type checkers. (Contributed by Alex Waygood in gh-106309.)

  - `typing.AnyStr` is deprecated. In Python 3.16, it will be removed from `typing.__all__`, and a `DeprecationWarning` will be emitted when it is imported or accessed. It will be removed entirely in Python 3.18. Use the new type parameter syntax instead. (Contributed by Michael The in gh-107116.)

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

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

- Assignment to a function’s `__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.)

### Pending Removal in Python 3.14

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

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

  - `ast.Num`

  - `ast.Str`

  - `ast.Bytes`

  - `ast.NameConstant`

  - `ast.Ellipsis`

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

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

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

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

- `importlib.abc` deprecated classes:

  - `importlib.abc.ResourceReader`

  - `importlib.abc.Traversable`

  - `importlib.abc.TraversableResources`

  Use `importlib.resources.abc` classes instead:

  - `importlib.resources.abc.Traversable`

  - `importlib.resources.abc.TraversableResources`

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

- `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.)

- `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 `get_context()` or `set_start_method()` APIs to explicitly specify when your code requires `'fork'`. See Contexts and start methods.

- `pathlib`: `is_relative_to()` and `relative_to()`: passing additional arguments is deprecated.

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

- `pty`:

  - `master_open()`: use `pty.openpty()`.

  - `slave_open()`: use `pty.openpty()`.

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

- `sqlite3`:

  - `version` and `version_info`.

  - `execute()` and `executemany()` if named placeholders are used and parameters is a sequence instead of a `dict`.

  - date and datetime adapter, date and timestamp converter: see the `sqlite3` documentation for suggested replacement recipes.

- `types.CodeType`: Accessing `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 `DeprecationWarning` in 3.12. May be removed in 3.14. (Contributed by Nikita Sobolev in gh-101866.)

- `typing`: `ByteString`, deprecated since Python 3.9, now causes a `DeprecationWarning` to be emitted when it is used.

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

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

### Pending Removal in Python 3.15

- `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.

- `locale`: `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 `locale.setlocale()`, `locale.getencoding()` and `locale.getlocale()` instead. (Contributed by Hugo van Kemenade in gh-111187.)

- `pathlib`: `pathlib.PurePath.is_reserved()` is deprecated and scheduled for removal in Python 3.15. Use `os.path.isreserved()` to detect reserved paths on Windows.

- `threading`: Passing any arguments to `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 `threading.RLock()` in Python 3.15. (Contributed by Nikita Sobolev in gh-102029.)

- `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", [])`.

- `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", {})`.

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

### Pending Removal in Python 3.16

- `array.array` `'u'` type (`wchar_t`): use the `'w'` type instead (`Py_UCS4`).

### Pending Removal in Future Versions

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

- `argparse`: Nesting argument groups and nesting mutually exclusive groups are deprecated.

- `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 `and`, `else`, `for`, `if`, `in`, `is` and `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 `int`.

  - Support for `__float__()` method returning a strict subclass of `float`: these methods will be required to return an instance of `float`.

  - Support for `__complex__()` method returning a strict subclass of `complex`: these methods will be required to return an instance of `complex`.

  - Delegation of `int()` to `__trunc__()` method.

- `calendar`: `calendar.January` and `calendar.February` constants are deprecated and replaced by `calendar.JANUARY` and `calendar.FEBRUARY`. (Contributed by Prince Roshan in gh-103636.)

- `codeobject.co_lnotab`: use the `codeobject.co_lines()` method instead.

- `datetime`:

  - `utcnow()`: use `datetime.datetime.now(tz=datetime.UTC)`.

  - `utcfromtimestamp()`: use `datetime.datetime.fromtimestamp(timestamp, tz=datetime.UTC)`.

- `gettext`: Plural value must be an integer.

- `importlib`:

  - `load_module()` method: use `exec_module()` instead.

  - `cache_from_source()` debug_override parameter is deprecated: use the optimization parameter instead.

- `importlib.metadata`:

  - `EntryPoints` tuple interface.

  - Implicit `None` on return values.

- `mailbox`: Use of StringIO input and text mode is deprecated, use BytesIO and binary mode instead.

- `os`: Calling `os.register_at_fork()` in multi-threaded process.

- `pydoc.ErrorDuringImport`: A tuple value for exc_info parameter is deprecated, use an exception instance.

- `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.)

- `sre_compile`, `sre_constants` and `sre_parse` modules.

- `ssl` options and protocols:

  - `ssl.SSLContext` without protocol argument is deprecated.

  - `ssl.SSLContext`: `set_npn_protocols()` and `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`

- `sysconfig.is_python_build()` check_home parameter is deprecated and ignored.

- `threading` methods:

  - `threading.Condition.notifyAll()`: use `notify_all()`.

  - `threading.Event.isSet()`: use `is_set()`.

  - `threading.Thread.isDaemon()`, `threading.Thread.setDaemon()`: use `threading.Thread.daemon` attribute.

  - `threading.Thread.getName()`, `threading.Thread.setName()`: use `threading.Thread.name` attribute.

  - `threading.currentThread()`: use `threading.current_thread()`.

  - `threading.activeCount()`: use `threading.active_count()`.

- `typing.Text` (gh-92332).

- `unittest.IsolatedAsyncioTestCase`: it is deprecated to return a value that is not `None` from a test case.

- `urllib.parse` deprecated functions: `urlparse()` instead

  - `splitattr()`

  - `splithost()`

  - `splitnport()`

  - `splitpasswd()`

  - `splitport()`

  - `splitquery()`

  - `splittag()`

  - `splittype()`

  - `splituser()`

  - `splitvalue()`

  - `to_bytes()`

- `urllib.request`: `URLopener` and `FancyURLopener` style of invoking requests is deprecated. Use newer `urlopen()` functions and methods.

- `wsgiref`: `SimpleHandler.stdout.write()` should not do partial writes.

- `zipimport.zipimporter.load_module()` is deprecated: use `exec_module()` instead.

## Removed

### PEP 594: dead batteries

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

  - `aifc`. (Contributed by Victor Stinner in gh-104773.)

  - `audioop`. (Contributed by Victor Stinner in gh-104773.)

  - `chunk`. (Contributed by Victor Stinner in gh-104773.)

  - `cgi` and `cgitb`.

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

    - `cgi.parse()` can be replaced by calling `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 `email` package, which implements the same MIME RFCs. For example, with `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 `email` package (e.g. `email.message.EmailMessage` and `email.message.Message`) which implements the same MIME RFCs, or with the multipart PyPI project.

    (Contributed by Victor Stinner in gh-104773.)

  - `crypt` module and its private `_crypt` extension. The `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.)

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

  - `mailcap`. The `mimetypes` module provides an alternative. (Contributed by Victor Stinner in gh-104773.)

  - `msilib`. (Contributed by Zachary Ware in gh-104773.)

  - `nis`. (Contributed by Victor Stinner in gh-104773.)

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

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

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

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

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

  - `sunau`. (Contributed by Victor Stinner in gh-104773.)

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

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

  - `xdrlib`. (Contributed by Victor Stinner in gh-104773.)

### 2to3

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

### configparser

- Remove the undocumented `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.)

### importlib

- Remove `importlib.resources` deprecated methods:

  - `contents()`

  - `is_resource()`

  - `open_binary()`

  - `open_text()`

  - `path()`

  - `read_binary()`

  - `read_text()`

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

- Remove deprecated `__getitem__()` access for `importlib.metadata.EntryPoint` objects. (Contributed by Jason R. Coombs in gh-113175.)

### locale

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

### logging

- `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 `logging.Logger.warning()` method, `logging.LoggerAdapter.warning()` method and `logging.warning()` function. (Contributed by Victor Stinner in gh-105376.)

### pathlib

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

### re

- 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.)

### tkinter

- Remove the `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.)

### turtle

- Remove the `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.)

### typing

- Namespaces `typing.io` and `typing.re`, deprecated in Python 3.8, are now removed. The items in those namespaces can be imported directly from `typing`. (Contributed by Sebastian Rittau in gh-92871.)

- Remove support for the keyword-argument method of creating `typing.TypedDict` types, deprecated in Python 3.11. (Contributed by Tomas Roun in gh-104786.)

### unittest

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

  - `unittest.findTestCases()`

  - `unittest.makeSuite()`

  - `unittest.getTestCaseNames()`

  Use `TestLoader` methods instead:

  - `unittest.TestLoader.loadTestsFromModule()`

  - `unittest.TestLoader.loadTestsFromTestCase()`

  - `unittest.TestLoader.getTestCaseNames()`

  (Contributed by Hugo van Kemenade in gh-104835.)

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

### urllib

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

### webbrowser

- Remove the untested and undocumented `webbrowser` `MacOSX` class, deprecated in Python 3.11. Use the `MacOSXOSAScript` class (introduced in Python 3.2) instead. (Contributed by Hugo van Kemenade in gh-104804.)

- Remove deprecated `webbrowser.MacOSXOSAScript._name` attribute. Use `webbrowser.MacOSXOSAScript.name` attribute instead. (Contributed by Nikita Sobolev in gh-105546.)

### Others

- None yet

## CPython bytecode changes

- 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.)

## Porting to Python 3.13

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

### Changes in the Python API

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

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

- The `threading` module now expects the `_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.)

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

- `pathlib.Path.glob()` and `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.

## Build Changes

- Autoconf 2.71 and aclocal 1.16.4 is now required to regenerate the `configure` script. (Contributed by Christian Heimes in gh-89886.)

- SQLite 3.15.2 or newer is required to build the `sqlite3` extension module. (Contributed by Erlend Aasland in gh-105875.)

- Python built with `configure` `--with-trace-refs` (tracing references) is now ABI compatible with the Python release build and 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 limited C API. (Contributed by Victor Stinner in gh-85283.)

- `wasm32-wasi` is now a tier 2 platform. (Contributed by Brett Cannon in gh-115192.)

- `wasm32-emscripten` is no longer a supported platform. (Contributed by Brett Cannon in gh-115192.)

## C API Changes

### New Features

- You no longer have to define the `PY_SSIZE_T_CLEAN` macro before including `Python.h` when using `#` formats in format codes. APIs accepting the format codes always use `Py_ssize_t` for `#` formats. (Contributed by Inada Naoki in gh-104922.)

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

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

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

- Add `PyObject_GetOptionalAttr()` and `PyObject_GetOptionalAttrString()`, variants of `PyObject_GetAttr()` and `PyObject_GetAttrString()` which don’t raise `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 `PyMapping_GetOptionalItem()` and `PyMapping_GetOptionalItemString()`: variants of `PyObject_GetItem()` and `PyMapping_GetItemString()` which don’t raise `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:

  - `PyObject_HasAttrWithError()` replaces `PyObject_HasAttr()`.

  - `PyObject_HasAttrStringWithError()` replaces `PyObject_HasAttrString()`.

  - `PyMapping_HasKeyWithError()` replaces `PyMapping_HasKey()`.

  - `PyMapping_HasKeyStringWithError()` replaces `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 debug mode or `with assertions`, `PyTuple_SET_ITEM()` and `PyList_SET_ITEM()` now check the index argument with an assertion. (Contributed by Victor Stinner in gh-106168.)

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

- Add `PyDict_GetItemRef()` and `PyDict_GetItemStringRef()` functions: similar to `PyDict_GetItemWithError()` but returning a strong reference instead of a 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 `PyDict_SetDefaultRef()`, which is similar to `PyDict_SetDefault()` but returns a strong reference instead of a 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 `PyDict_ContainsString()` function: same as `PyDict_Contains()`, but key is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*. (Contributed by Victor Stinner in gh-108314.)

- Added `PyList_GetItemRef()` function: similar to `PyList_GetItem()` but returns a strong reference instead of a borrowed reference.

- Add `Py_IsFinalizing()` function: check if the main Python interpreter is shutting down. (Contributed by Victor Stinner in gh-108014.)

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

- Python built with `configure` `--with-trace-refs` (tracing references) now supports the Limited API. (Contributed by Victor Stinner in gh-108634.)

- Add `PyObject_VisitManagedDict()` and `PyObject_ClearManagedDict()` functions which must be called by the traverse and clear functions of a type using `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 `PyUnicode_EqualToUTF8AndSize()` and `PyUnicode_EqualToUTF8()` functions: compare Unicode object with a 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 `PyThreadState_GetUnchecked()` function: similar to `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 `PySys_AuditTuple()` function: similar to `PySys_Audit()`, but pass event arguments as a Python `tuple` object. (Contributed by Victor Stinner in gh-85283.)

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

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

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

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

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

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

- Add `Py_HashPointer()` function to hash a pointer. (Contributed by Victor Stinner in gh-111545.)

- Add PyTime C API:

  - `PyTime_t` type.

  - `PyTime_MIN` and `PyTime_MAX` constants.

  - `PyTime_AsSecondsDouble()` `PyTime_Monotonic()`, `PyTime_PerfCounter()`, and `PyTime_Time()` functions.

  (Contributed by Victor Stinner and Petr Viktorin in gh-110850.)

- Add `PyLong_AsNativeBytes()`, `PyLong_FromNativeBytes()` and `PyLong_FromUnsignedNativeBytes()` functions to simplify converting between native integer types and Python `int` objects. (Contributed by Steve Dower in gh-111140.)

### Porting to Python 3.13

- `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 `Py_LIMITED_API` macro is defined, `Py_BUILD_CORE`, `Py_BUILD_CORE_BUILTIN` and `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.)

### Deprecated

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

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

- Deprecate old Python initialization functions:

  - `PySys_ResetWarnOptions()`: clear `sys.warnoptions` and `warnings.filters` instead.

  - `Py_GetExecPrefix()`: get `sys.exec_prefix` instead.

  - `Py_GetPath()`: get `sys.path` instead.

  - `Py_GetPrefix()`: get `sys.prefix` instead.

  - `Py_GetProgramFullPath()`: get `sys.executable` instead.

  - `Py_GetProgramName()`: get `sys.executable` instead.

  - `Py_GetPythonHome()`: get `PyConfig.home` or `PYTHONHOME` environment variable instead.

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

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

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

### Removed

- Removed chained `classmethod` descriptors (introduced in gh-63272). This can no longer be used to wrap other descriptors such as `property`. The core design of this feature was flawed and caused a number of downstream problems. To “pass-through” a `classmethod`, consider using the `__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 `PyObject_CallNoArgs()` or `PyObject_Call()` instead. Warning: `PyObject_Call()` positional arguments must be a `tuple` and must not be `NULL`, keyword arguments must be a `dict` or `NULL`, whereas removed functions checked arguments type and accepted `NULL` positional and keyword arguments. To replace `PyEval_CallObjectWithKeywords(func, NULL, kwargs)` with `PyObject_Call()`, pass an empty tuple as positional arguments using `PyTuple_New(0)`.

  - `PyEval_CallFunction()`: use `PyObject_CallFunction()` instead.

  - `PyEval_CallMethod()`: use `PyObject_CallMethod()` instead.

  - `PyCFunction_Call()`: use `PyObject_Call()` instead.

  (Contributed by Victor Stinner in gh-105107.)

- Remove old buffer protocols deprecated in Python 3.0. Use Buffer Protocol instead.

  - `PyObject_CheckReadBuffer()`: Use `PyObject_CheckBuffer()` to test if the object supports the buffer protocol. Note that `PyObject_CheckBuffer()` doesn’t guarantee that `PyObject_GetBuffer()` will succeed. To test if the object is actually readable, see the next example of `PyObject_GetBuffer()`.

  - `PyObject_AsCharBuffer()`, `PyObject_AsReadBuffer()`: `PyObject_GetBuffer()` and `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);

  - `PyObject_AsWriteBuffer()`: Use `PyObject_GetBuffer()` and `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 `PyConfig.warnoptions` instead.

  - `PySys_AddWarnOption()`: use `PyConfig.warnoptions` instead.

  - `PySys_AddXOption()`: use `PyConfig.xoptions` instead.

  - `PySys_HasWarnOptions()`: use `PyConfig.xoptions` instead.

  - `PySys_SetArgvEx()`: set `PyConfig.argv` instead.

  - `PySys_SetArgv()`: set `PyConfig.argv` instead.

  - `PySys_SetPath()`: set `PyConfig.module_search_paths` instead.

  - `Py_SetPath()`: set `PyConfig.module_search_paths` instead.

  - `Py_SetProgramName()`: set `PyConfig.program_name` instead.

  - `Py_SetPythonHome()`: set `PyConfig.home` instead.

  - `Py_SetStandardStreamEncoding()`: set `PyConfig.stdio_encoding` instead, and set also maybe `PyConfig.legacy_windows_stdio` (on Windows).

  - `_Py_SetProgramFullPath()`: set `PyConfig.executable` instead.

  Use the new `PyConfig` API of the Python Initialization Configuration 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:

  - `PyEval_SaveThread()` and `PyEval_RestoreThread()`;

  - low-level `PyEval_AcquireThread()` and `PyEval_RestoreThread()`;

  - or `PyGILState_Ensure()` and `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 `PyInterpreterState_Get()` which was kept for backward compatibility with Python 3.8. The pythoncapi-compat project can be used to get `PyInterpreterState_Get()` on Python 3.8 and older. (Contributed by Victor Stinner in gh-106320.)

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

### Pending Removal in Python 3.14

- Creating immutable types (`Py_TPFLAGS_IMMUTABLETYPE`) with mutable bases using the C API.

- Global configuration variables:

  - `Py_DebugFlag`: use `PyConfig.parser_debug`

  - `Py_VerboseFlag`: use `PyConfig.verbose`

  - `Py_QuietFlag`: use `PyConfig.quiet`

  - `Py_InteractiveFlag`: use `PyConfig.interactive`

  - `Py_InspectFlag`: use `PyConfig.inspect`

  - `Py_OptimizeFlag`: use `PyConfig.optimization_level`

  - `Py_NoSiteFlag`: use `PyConfig.site_import`

  - `Py_BytesWarningFlag`: use `PyConfig.bytes_warning`

  - `Py_FrozenFlag`: use `PyConfig.pathconfig_warnings`

  - `Py_IgnoreEnvironmentFlag`: use `PyConfig.use_environment`

  - `Py_DontWriteBytecodeFlag`: use `PyConfig.write_bytecode`

  - `Py_NoUserSiteDirectory`: use `PyConfig.user_site_directory`

  - `Py_UnbufferedStdioFlag`: use `PyConfig.buffered_stdio`

  - `Py_HashRandomizationFlag`: use `PyConfig.use_hash_seed` and `PyConfig.hash_seed`

  - `Py_IsolatedFlag`: use `PyConfig.isolated`

  - `Py_LegacyWindowsFSEncodingFlag`: use `PyPreConfig.legacy_windows_fs_encoding`

  - `Py_LegacyWindowsStdioFlag`: use `PyConfig.legacy_windows_stdio`

  - `Py_FileSystemDefaultEncoding`: use `PyConfig.filesystem_encoding`

  - `Py_HasFileSystemDefaultEncoding`: use `PyConfig.filesystem_encoding`

  - `Py_FileSystemDefaultEncodeErrors`: use `PyConfig.filesystem_errors`

  - `Py_UTF8Mode`: use `PyPreConfig.utf8_mode` (see `Py_PreInitialize()`)

  The `Py_InitializeFromConfig()` API should be used with `PyConfig` instead.

### Pending Removal in Python 3.15

- `PyImport_ImportModuleNoBlock()`: use `PyImport_ImportModule()`.

- `PyWeakref_GET_OBJECT()`: use `PyWeakref_GetRef()` instead.

- `PyWeakref_GetObject()`: use `PyWeakref_GetRef()` instead.

- `Py_UNICODE_WIDE` type: use `wchar_t` instead.

- `Py_UNICODE` type: use `wchar_t` instead.

- Python initialization functions:

  - `PySys_ResetWarnOptions()`: clear `sys.warnoptions` and `warnings.filters` instead.

  - `Py_GetExecPrefix()`: get `sys.exec_prefix` instead.

  - `Py_GetPath()`: get `sys.path` instead.

  - `Py_GetPrefix()`: get `sys.prefix` instead.

  - `Py_GetProgramFullPath()`: get `sys.executable` instead.

  - `Py_GetProgramName()`: get `sys.executable` instead.

  - `Py_GetPythonHome()`: get `PyConfig.home` or `PYTHONHOME` environment variable instead.

### Pending Removal in Future Versions

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

- `Py_TPFLAGS_HAVE_FINALIZE`: no needed since Python 3.8.

- `PyErr_Fetch()`: use `PyErr_GetRaisedException()`.

- `PyErr_NormalizeException()`: use `PyErr_GetRaisedException()`.

- `PyErr_Restore()`: use `PyErr_SetRaisedException()`.

- `PyModule_GetFilename()`: use `PyModule_GetFilenameObject()`.

- `PyOS_AfterFork()`: use `PyOS_AfterFork_Child()`.

- `PySlice_GetIndicesEx()`.

- `PyUnicode_AsDecodedObject()`.

- `PyUnicode_AsDecodedUnicode()`.

- `PyUnicode_AsEncodedObject()`.

- `PyUnicode_AsEncodedUnicode()`.

- `PyUnicode_READY()`: not needed since Python 3.12.

- `_PyErr_ChainExceptions()`.

- `PyBytesObject.ob_shash` member: call `PyObject_Hash()` instead.

- `PyDictObject.ma_version_tag` member.

- TLS API:

  - `PyThread_create_key()`: use `PyThread_tss_alloc()`.

  - `PyThread_delete_key()`: use `PyThread_tss_free()`.

  - `PyThread_set_key_value()`: use `PyThread_tss_set()`.

  - `PyThread_get_key_value()`: use `PyThread_tss_get()`.

  - `PyThread_delete_key_value()`: use `PyThread_tss_delete()`.

  - `PyThread_ReInitTLS()`: no longer needed.

- Remove undocumented `PY_TIMEOUT_MAX` constant from the limited C API. (Contributed by Victor Stinner in gh-110014.)

## Regression Test Changes

- Python built with `configure` `--with-pydebug` now supports a `-X presite=package.module` 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.)