What's New In Python 3.12
*************************

Release:
   3.13.0a0

Date:
   May 23, 2023

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

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 3.12 moves
  towards release, so it's worth checking back even after reading
  earlier versions.


Summary -- Release highlights
=============================

New typing features:

* **PEP 688**: Making the buffer protocol accessible in Python

* PEP 692: Using TypedDict for more precise **kwargs typing

* **PEP 698**: Override Decorator for Static Typing

Important deprecations, removals or restrictions:

* **PEP 623**: Remove wstr from Unicode

* **PEP 632**: Remove the "distutils" package


Improved Error Messages
=======================

* Modules from the standard library are now potentially suggested as
  part of the error messages displayed by the interpreter when a
  "NameError" is raised to the top level. Contributed by Pablo Galindo
  in gh-98254.

  >>> sys.version_info
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  NameError: name 'sys' is not defined. Did you forget to import 'sys'?

* Improve the error suggestion for "NameError" exceptions for
  instances. Now if a "NameError" is raised in a method and the
  instance has an attribute that's exactly equal to the name in the
  exception, the suggestion will include "self.<NAME>" instead of the
  closest match in the method scope. Contributed by Pablo Galindo in
  gh-99139.

  >>> class A:
  ...    def __init__(self):
  ...        self.blech = 1
  ...
  ...    def foo(self):
  ...        somethin = blech

  >>> A().foo()
  Traceback (most recent call last):
    File "<stdin>", line 1
      somethin = blech
                 ^^^^^
  NameError: name 'blech' is not defined. Did you mean: 'self.blech'?

* Improve the "SyntaxError" error message when the user types "import
  x from y" instead of "from y import x". Contributed by Pablo Galindo
  in gh-98931.

  >>> import a.y.z from b.y.z
  Traceback (most recent call last):
    File "<stdin>", line 1
      import a.y.z from b.y.z
      ^^^^^^^^^^^^^^^^^^^^^^^
  SyntaxError: Did you mean to use 'from ... import ...' instead?

* "ImportError" exceptions raised from failed "from <module> import
  <name>" statements now include suggestions for the value of "<name>"
  based on the available names in "<module>". Contributed by Pablo
  Galindo in gh-91058.

  >>> from collections import chainmap
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  ImportError: cannot import name 'chainmap' from 'collections'. Did you mean: 'ChainMap'?


New Features
============

* Add Python support for the Linux perf profiler through the new
  environment variable "PYTHONPERFSUPPORT", the new command-line
  option "-X perf", as well as the new
  "sys.activate_stack_trampoline()",
  "sys.deactivate_stack_trampoline()", and
  "sys.is_stack_trampoline_active()" APIs. (Design by Pablo Galindo.
  Contributed by Pablo Galindo and Christian Heimes with contributions
  from Gregory P. Smith [Google] and Mark Shannon in gh-96123.)

* The extraction methods in "tarfile", and "shutil.unpack_archive()",
  have a new a *filter* argument that allows limiting tar features
  than may be surprising or dangerous, such as creating files outside
  the destination directory. See Extraction filters for details. In
  Python 3.14, the default will switch to "'data'". (Contributed by
  Petr Viktorin in **PEP 706**.)


PEP 709: Comprehension inlining
-------------------------------

Dictionary, list, and set comprehensions are now inlined, rather than
creating a new single-use function object for each execution of the
comprehension. This speeds up execution of a comprehension by up to
2x.

Comprehension iteration variables remain isolated; they don't
overwrite a variable of the same name in the outer scope, nor are they
visible after the comprehension. This isolation is now maintained via
stack/locals manipulation, not via separate function scope.

Inlining does result in a few visible behavior changes:

* There is no longer a separate frame for the comprehension in
  tracebacks, and tracing/profiling no longer shows the comprehension
  as a function call.

* Calling "locals()" inside a comprehension now includes variables
  from outside the comprehension, and no longer includes the synthetic
  ".0" variable for the comprehension "argument".

Contributed by Carl Meyer and Vladimir Matveev in **PEP 709**.


PEP 688: Making the buffer protocol accessible in Python
--------------------------------------------------------

**PEP 688** introduces a way to use the buffer protocol from Python
code. Classes that implement the "__buffer__()" method are now usable
as buffer types.

The new "collections.abc.Buffer" ABC provides a standard way to
represent buffer objects, for example in type annotations. The new
"inspect.BufferFlags" enum represents the flags that can be used to
customize buffer creation. (Contributed by Jelle Zijlstra in
gh-102500.)


New Features Related to Type Hints
==================================

This section covers major changes affecting **PEP 484** type hints and
the "typing" module.


PEP 692: Using "TypedDict" for more precise "**kwargs" typing
-------------------------------------------------------------

Typing "**kwargs" in a function signature as introduced by **PEP 484**
allowed for valid annotations only in cases where all of the
"**kwargs" were of the same type.

This PEP specifies a more precise way of typing "**kwargs" by relying
on typed dictionaries:

   from typing import TypedDict, Unpack

   class Movie(TypedDict):
     name: str
     year: int

   def foo(**kwargs: Unpack[Movie]): ...

See **PEP 692** for more details.

(PEP written by Franek Magiera)


Other Language Changes
======================

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

* "memoryview" now supports the half-float type (the "e" format code).
  (Contributed by Dong-hee Na and Antoine Pitrou in gh-90751.)

* The parser now raises "SyntaxError" when parsing source code
  containing null bytes. (Contributed by Pablo Galindo in gh-96670.)

* "ast.parse()" now raises "SyntaxError" instead of "ValueError" when
  parsing source code containing null bytes. (Contributed by Pablo
  Galindo in gh-96670.)

* The Garbage Collector now runs only on the eval breaker mechanism of
  the Python bytecode evaluation loop instead of object allocations.
  The GC can also run when "PyErr_CheckSignals()" is called so C
  extensions that need to run for a long time without executing any
  Python code also have a chance to execute the GC periodically.
  (Contributed by Pablo Galindo in gh-97922.)

* A backslash-character pair that is not a valid escape sequence now
  generates a "SyntaxWarning", instead of "DeprecationWarning". For
  example, "re.compile("\d+\.\d+")" now emits a "SyntaxWarning"
  (""\d"" is an invalid escape sequence), use raw strings for regular
  expression: "re.compile(r"\d+\.\d+")". In a future Python version,
  "SyntaxError" will eventually be raised, instead of "SyntaxWarning".
  (Contributed by Victor Stinner in gh-98401.)

* Octal escapes with value larger than "0o377" (ex: ""\477""),
  deprecated in Python 3.11, now produce a "SyntaxWarning", instead of
  "DeprecationWarning". In a future Python version they will be
  eventually a "SyntaxError". (Contributed by Victor Stinner in
  gh-98401.)

* All builtin and extension callables expecting boolean parameters now
  accept arguments of any type instead of just "bool" and "int".
  (Contributed by Serhiy Storchaka in gh-60203.)

* Variables used in the target part of comprehensions that are not
  stored to can now be used in assignment expressions (":="). For
  example, in "[(b := 1) for a, b.prop in some_iter]", the assignment
  to "b" is now allowed. Note that assigning to variables stored to in
  the target part of comprehensions (like "a") is still disallowed, as
  per **PEP 572**. (Contributed by Nikita Sobolev in gh-100581.)

* "slice" objects are now hashable, allowing them to be used as dict
  keys and set items. (Contributed by Will Bradshaw and Furkan Onder
  in gh-101264.)

* Exceptions raised in a typeobject's "__set_name__" method are no
  longer wrapped by a "RuntimeError". Context information is added to
  the exception as a **PEP 678** note. (Contributed by Irit Katriel in
  gh-77757.)

* When a "try-except*" construct handles the entire "ExceptionGroup"
  and raises one other exception, that exception is no longer wrapped
  in an "ExceptionGroup". Also changed in version 3.11.4. (Contributed
  by Irit Katriel in gh-103590.)


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

* None yet.


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


array
-----

* The "array.array" class now supports subscripting, making it a
  *generic type*. (Contributed by Jelle Zijlstra in gh-98658.)


asyncio
-------

* The performance of writing to sockets in "asyncio" has been
  significantly improved. "asyncio" now avoids unnecessary copying
  when writing to sockets and uses "sendmsg()" if the platform
  supports it. (Contributed by Kumar Aditya in gh-91166.)

* Added "asyncio.eager_task_factory()" and
  "asyncio.create_eager_task_factory()" functions to allow opting an
  event loop in to eager task execution, making some use-cases 2x to
  5x faster. (Contributed by Jacob Bower & Itamar O in gh-102853,
  gh-104140, and gh-104138)

* On Linux, "asyncio" uses "PidfdChildWatcher" by default if
  "os.pidfd_open()" is available and functional instead of
  "ThreadedChildWatcher". (Contributed by Kumar Aditya in gh-98024.)

* The child watcher classes "MultiLoopChildWatcher",
  "FastChildWatcher", "AbstractChildWatcher" and "SafeChildWatcher"
  are deprecated and will be removed in Python 3.14. It is recommended
  to not manually configure a child watcher as the event loop now uses
  the best available child watcher for each platform
  ("PidfdChildWatcher" if supported and "ThreadedChildWatcher"
  otherwise). (Contributed by Kumar Aditya in gh-94597.)

* "asyncio.set_child_watcher()", "asyncio.get_child_watcher()",
  "asyncio.AbstractEventLoopPolicy.set_child_watcher()" and
  "asyncio.AbstractEventLoopPolicy.get_child_watcher()" are deprecated
  and will be removed in Python 3.14. (Contributed by Kumar Aditya in
  gh-94597.)

* Add *loop_factory* parameter to "asyncio.run()" to allow specifying
  a custom event loop factory. (Contributed by Kumar Aditya in
  gh-99388.)

* Add C implementation of "asyncio.current_task()" for 4x-6x speedup.
  (Contributed by Itamar Ostricher and Pranav Thulasiram Bhat in
  gh-100344.)

* "asyncio.iscoroutine()" now returns "False" for generators as
  "asyncio" does not support legacy generator-based coroutines.
  (Contributed by Kumar Aditya in gh-102748.)

* "asyncio.wait()" and "asyncio.as_completed()" now accepts generators
  yielding tasks. (Contributed by Kumar Aditya in gh-78530.)


calendar
--------

* Add enums "Month" and "Day". (Contributed by Prince Roshan in
  gh-103636.)


csv
---

* Add "QUOTE_NOTNULL" and "QUOTE_STRINGS" flags to provide finer
  grained control of "None" and empty strings by "writer" objects.


inspect
-------

* Add "inspect.markcoroutinefunction()" to mark sync functions that
  return a *coroutine* for use with "inspect.iscoroutinefunction()".
  (Contributed Carlton Gibson in gh-99247.)

* Add "inspect.getasyncgenstate()" and "inspect.getasyncgenlocals()"
  for determining the current state of asynchronous generators.
  (Contributed by Thomas Krennwallner in bpo-35759.)

* The performance of "inspect.getattr_static()" has been considerably
  improved. Most calls to the function should be at least 2x faster
  than they were in Python 3.11, and some may be 6x faster or more.
  (Contributed by Alex Waygood in gh-103193.)


pathlib
-------

* Add support for subclassing "pathlib.PurePath" and "Path", plus
  their Posix- and Windows-specific variants. Subclasses may override
  the "with_segments()" method to pass information between path
  instances.

* Add "walk()" for walking the directory trees and generating all file
  or directory names within them, similar to "os.walk()". (Contributed
  by Stanislav Zmiev in gh-90385.)

* Add *walk_up* optional parameter to "pathlib.PurePath.relative_to()"
  to allow the insertion of ".." entries in the result; this behavior
  is more consistent with "os.path.relpath()". (Contributed by
  Domenico Ragusa in bpo-40358.)

* Add "pathlib.Path.is_junction()" as a proxy to
  "os.path.isjunction()". (Contributed by Charles Machalow in
  gh-99547.)

* Add *case_sensitive* optional parameter to "pathlib.Path.glob()",
  "pathlib.Path.rglob()" and "pathlib.PurePath.match()" for matching
  the path's case sensitivity, allowing for more precise control over
  the matching process.


dis
---

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


fractions
---------

* Objects of type "fractions.Fraction" now support float-style
  formatting. (Contributed by Mark Dickinson in gh-100161.)


itertools
---------

* Added "itertools.batched()" for collecting into even-sized tuples
  where the last batch may be shorter than the rest. (Contributed by
  Raymond Hettinger in gh-98363.)


math
----

* Added "math.sumprod()" for computing a sum of products. (Contributed
  by Raymond Hettinger in gh-100485.)


os
--

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

* "os.DirEntry" now includes an "os.DirEntry.is_junction()" method to
  check if the entry is a junction. (Contributed by Charles Machalow
  in gh-99547.)

* Add "os.listdrives()", "os.listvolumes()" and "os.listmounts()"
  functions on Windows for enumerating drives, volumes and mount
  points. (Contributed by Steve Dower in gh-102519.)

* "os.stat()" and "os.lstat()" are now more accurate on Windows. The
  "st_birthtime" field will now be filled with the creation time of
  the file, and "st_ctime" is deprecated but still contains the
  creation time (but in the future will return the last metadata
  change, for consistency with other platforms). "st_dev" may be up to
  64 bits and "st_ino" up to 128 bits depending on your file system,
  and "st_rdev" is always set to zero rather than incorrect values.
  Both functions may be significantly faster on newer releases of
  Windows. (Contributed by Steve Dower in gh-99726.)


os.path
-------

* Add "os.path.isjunction()" to check if a given path is a junction.
  (Contributed by Charles Machalow in gh-99547.)

* Add "os.path.splitroot()" to split a path into a triad "(drive,
  root, tail)". (Contributed by Barney Gale in gh-101000.)


pdb
---

* Add convenience variables to hold values temporarily for debug
  session and provide quick access to values like the current frame or
  the return value. (Contributed by Tian Gao in gh-103693.)


shutil
------

* "shutil.make_archive()" now passes the *root_dir* argument to custom
  archivers which support it. In this case it no longer temporarily
  changes the current working directory of the process to *root_dir*
  to perform archiving. (Contributed by Serhiy Storchaka in gh-74696.)

* "shutil.rmtree()" now accepts a new argument *onexc* which is an
  error handler like *onerror* but which expects an exception instance
  rather than a *(typ, val, tb)* triplet. *onerror* is deprecated and
  will be removed in Python 3.14. (Contributed by Irit Katriel in
  gh-102828.)

* "shutil.which()" now consults the *PATHEXT* environment variable to
  find matches within *PATH* on Windows even when the given *cmd*
  includes a directory component. (Contributed by Charles Machalow in
  gh-103179.)

  "shutil.which()" will call "NeedCurrentDirectoryForExePathW" when
  querying for executables on Windows to determine if the current
  working directory should be prepended to the search path.
  (Contributed by Charles Machalow in gh-103179.)

  "shutil.which()" will return a path matching the *cmd* with a
  component from "PATHEXT" prior to a direct match elsewhere in the
  search path on Windows. (Contributed by Charles Machalow in
  gh-103179.)


sqlite3
-------

* Add a command-line interface. (Contributed by Erlend E. Aasland in
  gh-77617.)

* Add the "autocommit" attribute to "Connection" and the *autocommit*
  parameter to "connect()" to control **PEP 249**-compliant
  transaction handling. (Contributed by Erlend E. Aasland in
  gh-83638.)

* Add *entrypoint* keyword-only parameter to "load_extension()", for
  overriding the SQLite extension entry point. (Contributed by Erlend
  E. Aasland in gh-103015.)

* Add "getconfig()" and "setconfig()" to "Connection" to make
  configuration changes to a database connection. (Contributed by
  Erlend E. Aasland in gh-103489.)


threading
---------

* Add "threading.settrace_all_threads()" and
  "threading.setprofile_all_threads()" that allow to set tracing and
  profiling functions in all running threads in addition to the
  calling one. (Contributed by Pablo Galindo in gh-93503.)


tkinter
-------

* "tkinter.Canvas.coords()" now flattens its arguments. It now accepts
  not only coordinates as separate arguments ("x1, y1, x2, y2, ...")
  and a sequence of coordinates ("[x1, y1, x2, y2, ...]"), but also
  coordinates grouped in pairs ("(x1, y1), (x2, y2), ..." and "[(x1,
  y1), (x2, y2), ...]"), like "create_*()" methods. (Contributed by
  Serhiy Storchaka in gh-94473.)


types
-----

* Add "types.get_original_bases()" to allow for further introspection
  of User-defined generic types when subclassed. (Contributed by James
  Hilton-Balfe and Alex Waygood in gh-101827.)


unicodedata
-----------

* The Unicode database has been updated to version 15.0.0.
  (Contributed by Benjamin Peterson in gh-96734).


unittest
--------

Added "--durations" command line option, showing the N slowest test
cases:

   python3 -m unittest --durations=3 lib.tests.test_threading
   .....
   Slowest test durations
   ----------------------------------------------------------------------
   1.210s     test_timeout (Lib.test.test_threading.BarrierTests)
   1.003s     test_default_timeout (Lib.test.test_threading.BarrierTests)
   0.518s     test_timeout (Lib.test.test_threading.EventTests)

   (0.000 durations hidden.  Use -v to show these durations.)
   ----------------------------------------------------------------------
   Ran 158 tests in 9.869s

   OK (skipped=3)

(Contributed by Giampaolo Rodola in bpo-4080)


uuid
----

* Add a command-line interface. (Contributed by Adam Chhina in
  gh-88597.)


tempfile
--------

* The "tempfile.NamedTemporaryFile" function has a new optional
  parameter *delete_on_close* (Contributed by Evgeny Zorin in
  gh-58451.)

* "tempfile.mkdtemp()" now always returns an absolute path, even if
  the argument provided to the *dir* parameter is a relative path.


typing
------

* Add "typing.override()", an override decorator telling to static
  type checkers to verify that a method overrides some method or
  attribute of the same name on a base class, as per **PEP 698**.
  (Contributed by Steven Troxler in gh-101564.)

* "isinstance()" checks against "runtime-checkable protocols" now use
  "inspect.getattr_static()" rather than "hasattr()" to lookup whether
  attributes exist. This means that descriptors and "__getattr__()"
  methods are no longer unexpectedly evaluated during "isinstance()"
  checks against runtime-checkable protocols. However, it may also
  mean that some objects which used to be considered instances of a
  runtime-checkable protocol may no longer be considered instances of
  that protocol on Python 3.12+, and vice versa. Most users are
  unlikely to be affected by this change. (Contributed by Alex Waygood
  in gh-102433.)

* The members of a runtime-checkable protocol are now considered
  "frozen" at runtime as soon as the class has been created. Monkey-
  patching attributes onto a runtime-checkable protocol will still
  work, but will have no impact on "isinstance()" checks comparing
  objects to the protocol. For example:

     >>> from typing import Protocol, runtime_checkable
     >>> @runtime_checkable
     ... class HasX(Protocol):
     ...     x = 1
     ...
     >>> class Foo: ...
     ...
     >>> f = Foo()
     >>> isinstance(f, HasX)
     False
     >>> f.x = 1
     >>> isinstance(f, HasX)
     True
     >>> HasX.y = 2
     >>> isinstance(f, HasX)  # unchanged, even though HasX now also has a "y" attribute
     True

  This change was made in order to speed up "isinstance()" checks
  against runtime-checkable protocols.

* The performance profile of "isinstance()" checks against "runtime-
  checkable protocols" has changed significantly. Most "isinstance()"
  checks against protocols with only a few members should be at least
  2x faster than in 3.11, and some may be 20x faster or more. However,
  "isinstance()" checks against protocols with fourteen or more
  members may be slower than in Python 3.11. (Contributed by Alex
  Waygood in gh-74690 and gh-103193.)


sys
---

* Add "sys.activate_stack_trampoline()" and
  "sys.deactivate_stack_trampoline()" for activating and deactivating
  stack profiler trampolines, and "sys.is_stack_trampoline_active()"
  for querying if stack profiler trampolines are active. (Contributed
  by Pablo Galindo and Christian Heimes with contributions from
  Gregory P. Smith [Google] and Mark Shannon in gh-96123.)

* Add "sys.last_exc" which holds the last unhandled exception that was
  raised (for post-mortem debugging use cases). Deprecate the three
  fields that have the same information in its legacy form:
  "sys.last_type", "sys.last_value" and "sys.last_traceback".
  (Contributed by Irit Katriel in gh-102778.)

* "sys._current_exceptions()" now returns a mapping from thread-id to
  an exception instance, rather than to a "(typ, exc, tb)" tuple.
  (Contributed by Irit Katriel in gh-103176.)


Optimizations
=============

* Removed "wstr" and "wstr_length" members from Unicode objects. It
  reduces object size by 8 or 16 bytes on 64bit platform. (**PEP
  623**) (Contributed by Inada Naoki in gh-92536.)

* Added experimental support for using the BOLT binary optimizer in
  the build process, which improves performance by 1-5%. (Contributed
  by Kevin Modzelewski in gh-90536 and tuned by Dong-hee Na in
  gh-101525)

* Speed up the regular expression substitution (functions "re.sub()"
  and "re.subn()" and corresponding "re.Pattern" methods) for
  replacement strings containing group references by 2--3 times.
  (Contributed by Serhiy Storchaka in gh-91524.)

* Speed up "asyncio.Task" creation by deferring expensive string
  formatting. (Contributed by Itamar O in gh-103793.)


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

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

* Removed the "JUMP_IF_FALSE_OR_POP" and "JUMP_IF_TRUE_OR_POP"
  instructions. (Contributed by Irit Katriel in gh-102859.)


Demos and Tools
===============

* Remove the "Tools/demo/" directory which contained old demo scripts.
  A copy can be found in the old-demos project. (Contributed by Victor
  Stinner in gh-97681.)

* Remove outdated example scripts of the "Tools/scripts/" directory. A
  copy can be found in the old-demos project. (Contributed by Victor
  Stinner in gh-97669.)


Deprecated
==========

* "typing.Hashable" and "typing.Sized" aliases for
  "collections.abc.Hashable" and "collections.abc.Sized". (gh-94309.)

* The "sqlite3" default adapters and converters are now deprecated.
  Instead, use the Adapter and converter recipes and tailor them to
  your needs. (Contributed by Erlend E. Aasland in gh-90016.)

* In "execute()", "DeprecationWarning" is now emitted when named
  placeholders are used together with parameters supplied as a
  *sequence* instead of as a "dict". Starting from Python 3.14, using
  named placeholders with parameters supplied as a sequence will raise
  a "ProgrammingError". (Contributed by Erlend E. Aasland in
  gh-101698.)

* The 3-arg signatures (type, value, traceback) of "throw()",
  "throw()" and "athrow()" are deprecated and may be removed in a
  future version of Python. Use the single-arg versions of these
  functions instead. (Contributed by Ofey Chan in gh-89874.)

* "DeprecationWarning" is now raised when "__package__" on a module
  differs from "__spec__.parent" (previously it was "ImportWarning").
  (Contributed by Brett Cannon in gh-65961.)

* The "get_event_loop()" method of the default event loop policy now
  emits a "DeprecationWarning" if there is no current event loop set
  and it decides to create one. (Contributed by Serhiy Storchaka and
  Guido van Rossum in gh-100160.)

* The "xml.etree.ElementTree" module now emits "DeprecationWarning"
  when testing the truth value of an "xml.etree.ElementTree.Element".
  Before, the Python implementation emitted "FutureWarning", and the C
  implementation emitted nothing.

* In accordance with **PEP 699**, the "ma_version_tag" field in
  "PyDictObject" is deprecated for extension modules. Accessing this
  field will generate a compiler warning at compile time. This field
  will be removed in Python 3.14. (Contributed by Ramvikrams and Kumar
  Aditya in gh-101193. PEP by Ken Jin.)

* The "st_ctime" fields return by "os.stat()" and "os.lstat()" on
  Windows are deprecated. In a future release, they will contain the
  last metadata change time, consistent with other platforms. For now,
  they still contain the creation time, which is also available in the
  new "st_birthtime" field. (Contributed by Steve Dower in gh-99726.)

* The "sys.last_type", "sys.last_value" and "sys.last_traceback"
  fields are deprecated. Use "sys.last_exc" instead. (Contributed by
  Irit Katriel in gh-102778.)

* The *onerror* argument of "shutil.rmtree()" is deprecated as will be
  removed in Python 3.14. Use *onexc* instead. (Contributed by Irit
  Katriel in gh-102828.)

* Extracting tar archives without specifying *filter* is deprecated
  until Python 3.14, when "'data'" filter will become the default. See
  Extraction filters for details.

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

* The bitwise inversion operator ("~") on bool is deprecated. It will
  throw an error in Python 3.14. Use "not" for logical negation of
  bools instead. In the rare case that you really need the bitwise
  inversion of the underlying "int", convert to int explicitly with
  "~int(x)". (Contributed by Tim Hoffmann in gh-103487.)

* "datetime.datetime"'s "utcnow()" and "utcfromtimestamp()" are
  deprecated and will be removed in a future version. Instead, use
  timezone-aware objects to represent datetimes in UTC: respectively,
  call "now()" and "fromtimestamp()"  with the *tz* parameter set to
  "datetime.UTC". (Contributed by Paul Ganssle in gh-103857.)


Pending Removal in Python 3.13
------------------------------

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

Modules (see **PEP 594**):

* "aifc"

* "audioop"

* "cgi"

* "cgitb"

* "chunk"

* "crypt"

* "imghdr"

* "mailcap"

* "msilib"

* "nis"

* "nntplib"

* "ossaudiodev"

* "pipes"

* "sndhdr"

* "spwd"

* "sunau"

* "telnetlib"

* "uu"

* "xdrlib"

APIs:

* "configparser.LegacyInterpolation" (gh-90765)

* "locale.getdefaultlocale()" (gh-90817)

* "turtle.RawTurtle.settiltangle()" (gh-50096)

* "unittest.findTestCases()" (gh-50096)

* "unittest.makeSuite()" (gh-50096)

* "unittest.getTestCaseNames()" (gh-50096)

* "webbrowser.MacOSX" (gh-86421)


Pending Removal in Python 3.14
------------------------------

* Deprecated the following "importlib.abc" classes, scheduled for
  removal in Python 3.14:

  * "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.)

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

* "typing.ByteString", deprecated since Python 3.9, now causes a
  "DeprecationWarning" to be emitted when it is used.

* Creating immutable types ("Py_TPFLAGS_IMMUTABLETYPE") with mutable
  bases using the C API.

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

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

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

* The default "multiprocessing" 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.

* "pty" has two undocumented "master_open()" and "slave_open()"
  functions that have been deprecated since Python 2 but only gained a
  proper "DeprecationWarning" in 3.12. Remove them in 3.14.

* 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.)

* The *onerror* argument of "shutil.rmtree()" is deprecated in 3.12,
  and will be removed in 3.14.

* 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.)

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

* The following "ast" 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.)


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.

* "typing.Text" (gh-92332)

* Currently Python accepts numeric literals immediately followed by
  keywords, for example "0in x", "1or x", "0if 1else 2".  It allows
  confusing and ambiguous expressions like "[0x1for x in y]" (which
  can be interpreted as "[0x1 for x in y]" or "[0x1f or x in y]"). A
  syntax warning is raised if the numeric literal is immediately
  followed by one of keywords "and", "else", "for", "if", "in", "is"
  and "or". In a future release it will be changed to a syntax error.
  (gh-87999)


Removed
=======

* Remove the "distutils" package. It was deprecated in Python 3.10 by
  **PEP 632** "Deprecate distutils module". For projects still using
  "distutils" and cannot be updated to something else, the
  "setuptools" project can be installed: it still provides
  "distutils". (Contributed by Victor Stinner in gh-92584.)

* Remove the bundled setuptools wheel from "ensurepip", and stop
  installing setuptools in environments created by "venv".

  "pip (>= 22.1)" does not require setuptools to be installed in the
  environment. "setuptools"-based (and "distutils"-based) packages can
  still be used with "pip install", since pip will provide
  "setuptools" in the build environment it uses for building a
  package.

  "easy_install", "pkg_resources", "setuptools" and "distutils" are no
  longer provided by default in environments created with "venv" or
  bootstrapped with "ensurepip", since they are part of the
  "setuptools" package. For projects relying on these at runtime, the
  "setuptools" project should be declared as a dependency and
  installed separately (typically, using pip).

  (Contributed by Pradyun Gedam in gh-95299.)

* Removed many old deprecated "unittest" features:

  * A number of "TestCase" method aliases:

    +------------------------------+---------------------------------+-----------------+
    | Deprecated alias             | Method Name                     | Deprecated in   |
    |==============================|=================================|=================|
    | "failUnless"                 | "assertTrue()"                  | 3.1             |
    +------------------------------+---------------------------------+-----------------+
    | "failIf"                     | "assertFalse()"                 | 3.1             |
    +------------------------------+---------------------------------+-----------------+
    | "failUnlessEqual"            | "assertEqual()"                 | 3.1             |
    +------------------------------+---------------------------------+-----------------+
    | "failIfEqual"                | "assertNotEqual()"              | 3.1             |
    +------------------------------+---------------------------------+-----------------+
    | "failUnlessAlmostEqual"      | "assertAlmostEqual()"           | 3.1             |
    +------------------------------+---------------------------------+-----------------+
    | "failIfAlmostEqual"          | "assertNotAlmostEqual()"        | 3.1             |
    +------------------------------+---------------------------------+-----------------+
    | "failUnlessRaises"           | "assertRaises()"                | 3.1             |
    +------------------------------+---------------------------------+-----------------+
    | "assert_"                    | "assertTrue()"                  | 3.2             |
    +------------------------------+---------------------------------+-----------------+
    | "assertEquals"               | "assertEqual()"                 | 3.2             |
    +------------------------------+---------------------------------+-----------------+
    | "assertNotEquals"            | "assertNotEqual()"              | 3.2             |
    +------------------------------+---------------------------------+-----------------+
    | "assertAlmostEquals"         | "assertAlmostEqual()"           | 3.2             |
    +------------------------------+---------------------------------+-----------------+
    | "assertNotAlmostEquals"      | "assertNotAlmostEqual()"        | 3.2             |
    +------------------------------+---------------------------------+-----------------+
    | "assertRegexpMatches"        | "assertRegex()"                 | 3.2             |
    +------------------------------+---------------------------------+-----------------+
    | "assertRaisesRegexp"         | "assertRaisesRegex()"           | 3.2             |
    +------------------------------+---------------------------------+-----------------+
    | "assertNotRegexpMatches"     | "assertNotRegex()"              | 3.5             |
    +------------------------------+---------------------------------+-----------------+

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

  * Undocumented and broken "TestCase" method
    "assertDictContainsSubset" (deprecated in Python 3.2).

  * Undocumented "TestLoader.loadTestsFromModule" parameter
    *use_load_tests* (deprecated and ignored since Python 3.2).

  * An alias of the "TextTestResult" class: "_TextTestResult"
    (deprecated in Python 3.2).

  (Contributed by Serhiy Storchaka in bpo-45162.)

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

  * "configparser.ParsingError" no longer has a "filename" attribute
    or argument. Use the "source" attribute and argument instead.

  * "configparser" no longer has a "SafeConfigParser" class. Use the
    shorter "ConfigParser" name instead.

  * "configparser.ConfigParser" no longer has a "readfp" method. Use
    "read_file()" instead.

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

  * "sqlite3.enable_shared_cache()"

  * "sqlite3.OptimizedUnicode"

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

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

  (Contributed by Erlend E. Aasland in gh-92548.)

* "smtpd" has been removed according to the schedule in **PEP 594**,
  having been deprecated in Python 3.4.7 and 3.5.4. Use aiosmtpd PyPI
  module or any other "asyncio"-based server instead. (Contributed by
  Oleg Iarygin in gh-93243.)

* "asynchat" and "asyncore" have been removed according to the
  schedule in **PEP 594**, having been deprecated in Python 3.6. Use
  "asyncio" instead. (Contributed by Nikita Sobolev in gh-96580.)

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

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

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

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

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

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

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

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

* Remove the "ssl.wrap_socket()" function, deprecated in Python 3.7:
  instead, create a "ssl.SSLContext" object and call its
  "ssl.SSLContext.wrap_socket" method. Any package that still uses
  "ssl.wrap_socket()" is broken and insecure. The function neither
  sends a SNI TLS extension nor validates server hostname. Code is
  subject to CWE-295: Improper Certificate Validation. (Contributed by
  Victor Stinner in gh-94199.)

* Many previously deprecated cleanups in "importlib" have now been
  completed:

  * References to, and support for "module_repr()" has been removed.
    (Contributed by Barry Warsaw in gh-97850.)

  * "importlib.util.set_package" has been removed. (Contributed by
    Brett Cannon in gh-65961.)

  * Support for "find_loader()" and "find_module()" APIs have been
    removed.  (Contributed by Barry Warsaw in gh-98040.)

  * "importlib.abc.Finder", "pkg.ImpImporter", and "pkg.ImpLoader"
    have been removed.  (Contributed by Barry Warsaw in gh-98040.)

  * The "imp" module has been removed.  (Contributed by Barry Warsaw
    in gh-98040.)

* Removed the "suspicious" rule from the documentation Makefile, and
  removed "Doc/tools/rstlint.py", both in favor of sphinx-lint.
  (Contributed by Julien Palard in gh-98179.)

* Remove the *keyfile* and *certfile* parameters from the "ftplib",
  "imaplib", "poplib" and "smtplib" modules, and the *key_file*,
  *cert_file* and *check_hostname* parameters from the "http.client"
  module, all deprecated since Python 3.6. Use the *context* parameter
  (*ssl_context* in "imaplib") instead. (Contributed by Victor Stinner
  in gh-94172.)

* "ftplib": Remove the "FTP_TLS.ssl_version" class attribute: use the
  *context* parameter instead. (Contributed by Victor Stinner in
  gh-94172.)

* Remove support for obsolete browsers from "webbrowser". Removed
  browsers include: Grail, Mosaic, Netscape, Galeon, Skipstone,
  Iceape, Firebird, and Firefox versions 35 and below (gh-102871).


Porting to Python 3.12
======================

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


Changes in the Python API
-------------------------

* More strict rules are now applied for numerical group references and
  group names in regular expressions. Only sequence of ASCII digits is
  now accepted as a numerical reference. The group name in bytes
  patterns and replacement strings can now only contain ASCII letters
  and digits and underscore. (Contributed by Serhiy Storchaka in
  gh-91760.)

* Removed "randrange()" functionality deprecated since Python 3.10.
  Formerly, "randrange(10.0)" losslessly converted to "randrange(10)".
  Now, it raises a "TypeError". Also, the exception raised for non-
  integral values such as "randrange(10.5)" or "randrange('10')" has
  been changed from "ValueError" to "TypeError".  This also prevents
  bugs where "randrange(1e25)" would silently select from a larger
  range than "randrange(10**25)". (Originally suggested by Serhiy
  Storchaka gh-86388.)

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

* Removed the "asyncore"-based "smtpd" module deprecated in Python
  3.4.7 and 3.5.4.  A recommended replacement is the "asyncio"-based
  aiosmtpd PyPI module.

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

* The "os" module no longer accepts bytes-like paths, like "bytearray"
  and "memoryview" types: only the exact "bytes" type is accepted for
  bytes strings. (Contributed by Victor Stinner in gh-98393.)

* "syslog.openlog()" and "syslog.closelog()" now fail if used in
  subinterpreters. "syslog.syslog()" may still be used in
  subinterpreters, but now only if "syslog.openlog()" has already been
  called in the main interpreter. These new restrictions do not apply
  to the main interpreter, so only a very small set of users might be
  affected. This change helps with interpreter isolation.
  Furthermore, "syslog" is a wrapper around process-global resources,
  which are best managed from the main interpreter. (Contributed by
  Dong-hee Na in gh-99127.)

* The undocumented locking behavior of "cached_property()" is removed,
  because it locked across all instances of the class, leading to high
  lock contention. This means that a cached property getter function
  could now run more than once for a single instance, if two threads
  race. For most simple cached properties (e.g. those that are
  idempotent and simply calculate a value based on other attributes of
  the instance) this will be fine.  If synchronization is needed,
  implement locking within the cached property getter function or
  around multi-threaded access points.

* "sys._current_exceptions()" now returns a mapping from thread-id to
  an exception instance, rather than to a "(typ, exc, tb)" tuple.
  (Contributed by Irit Katriel in gh-103176.)

* When extracting tar files using "tarfile" or
  "shutil.unpack_archive()", pass the *filter* argument to limit
  features that may be surprising or dangerous. See Extraction filters
  for details.


Build Changes
=============

* Python no longer uses "setup.py" to build shared C extension
  modules. Build parameters like headers and libraries are detected in
  "configure" script. Extensions are built by "Makefile". Most
  extensions use "pkg-config" and fall back to manual detection.
  (Contributed by Christian Heimes in gh-93939.)

* "va_start()" with two parameters, like "va_start(args, format)," is
  now required to build Python. "va_start()" is no longer called with
  a single parameter. (Contributed by Kumar Aditya in gh-93207.)

* CPython now uses the ThinLTO option as the default link time
  optimization policy if the Clang compiler accepts the flag.
  (Contributed by Dong-hee Na in gh-89536.)

* Add "COMPILEALL_OPTS" variable in Makefile to override "compileall"
  options (default: "-j0") in "make install". Also merged the 3
  "compileall" commands into a single command to build .pyc files for
  all optimization levels (0, 1, 2) at once. (Contributed by Victor
  Stinner in gh-99289.)

* Add platform triplets for 64-bit LoongArch:

  * loongarch64-linux-gnusf

  * loongarch64-linux-gnuf32

  * loongarch64-linux-gnu

  (Contributed by Zhang Na in gh-90656.)

* "PYTHON_FOR_REGEN" now require Python 3.10 or newer.


C API Changes
=============


New Features
------------

* **PEP 697**: Introduced the Unstable C API tier, intended for low-
  level tools like debuggers and JIT compilers. This API may change in
  each minor release of CPython without deprecation warnings. Its
  contents are marked by the "PyUnstable_" prefix in names.

  Code object constructors:

  * "PyUnstable_Code_New()" (renamed from "PyCode_New")

  * "PyUnstable_Code_NewWithPosOnlyArgs()" (renamed from
    "PyCode_NewWithPosOnlyArgs")

  Extra storage for code objects (**PEP 523**):

  * "PyUnstable_Eval_RequestCodeExtraIndex()" (renamed from
    "_PyEval_RequestCodeExtraIndex")

  * "PyUnstable_Code_GetExtra()" (renamed from "_PyCode_GetExtra")

  * "PyUnstable_Code_SetExtra()" (renamed from "_PyCode_SetExtra")

  The original names will continue to be available until the
  respective API changes.

  (Contributed by Petr Viktorin in gh-101101.)

* **PEP 697**: Added API for extending types whose instance memory
  layout is opaque:

  * "PyType_Spec.basicsize" can be zero or negative to specify
    inheriting or extending the base class size.

  * "PyObject_GetTypeData()" and "PyType_GetTypeDataSize()" added to
    allow access to subclass-specific instance data.

  * "Py_TPFLAGS_ITEMS_AT_END" and "PyObject_GetItemData()" added to
    allow safely extending certain variable-sized types, including
    "PyType_Type".

  * "Py_RELATIVE_OFFSET" added to allow defining "members" in terms of
    a subclass-specific struct.

  (Contributed by Petr Viktorin in gh-103509.)

* Added the new limited C API function "PyType_FromMetaclass()", which
  generalizes the existing "PyType_FromModuleAndSpec()" using an
  additional metaclass argument. (Contributed by Wenzel Jakob in
  gh-93012.)

* API for creating objects that can be called using the vectorcall
  protocol was added to the Limited API:

  * "Py_TPFLAGS_HAVE_VECTORCALL"

  * "PyVectorcall_NARGS()"

  * "PyVectorcall_Call()"

  * "vectorcallfunc"

  The "Py_TPFLAGS_HAVE_VECTORCALL" flag is now removed from a class
  when the class's "__call__()" method is reassigned. This makes
  vectorcall safe to use with mutable types (i.e. heap types without
  the immutable flag, "Py_TPFLAGS_IMMUTABLETYPE"). Mutable types that
  do not override "tp_call" now inherit the
  "Py_TPFLAGS_HAVE_VECTORCALL" flag. (Contributed by Petr Viktorin in
  gh-93274.)

  The "Py_TPFLAGS_MANAGED_DICT" and "Py_TPFLAGS_MANAGED_WEAKREF" flags
  have been added. This allows extensions classes to support object
  "__dict__" and weakrefs with less bookkeeping, using less memory and
  with faster access.

* API for performing calls using the vectorcall protocol was added to
  the Limited API:

  * "PyObject_Vectorcall()"

  * "PyObject_VectorcallMethod()"

  * "PY_VECTORCALL_ARGUMENTS_OFFSET"

  This means that both the incoming and outgoing ends of the vector
  call protocol are now available in the Limited API. (Contributed by
  Wenzel Jakob in gh-98586.)

* Added two new public functions, "PyEval_SetProfileAllThreads()" and
  "PyEval_SetTraceAllThreads()", that allow to set tracing and
  profiling functions in all running threads in addition to the
  calling one. (Contributed by Pablo Galindo in gh-93503.)

* Added new function "PyFunction_SetVectorcall()" to the C API which
  sets the vectorcall field of a given "PyFunctionObject".
  (Contributed by Andrew Frost in gh-92257.)

* The C API now permits registering callbacks via
  "PyDict_AddWatcher()", "PyDict_Watch()" and related APIs to be
  called whenever a dictionary is modified. This is intended for use
  by optimizing interpreters, JIT compilers, or debuggers.
  (Contributed by Carl Meyer in gh-91052.)

* Added "PyType_AddWatcher()" and "PyType_Watch()" API to register
  callbacks to receive notification on changes to a type. (Contributed
  by Carl Meyer in gh-91051.)

* Added "PyCode_AddWatcher()" and "PyCode_ClearWatcher()" APIs to
  register callbacks to receive notification on creation and
  destruction of code objects. (Contributed by Itamar Ostricher in
  gh-91054.)

* Add "PyFrame_GetVar()" and "PyFrame_GetVarString()" functions to get
  a frame variable by its name. (Contributed by Victor Stinner in
  gh-91248.)

* Add "PyErr_GetRaisedException()" and "PyErr_SetRaisedException()"
  for saving and restoring the current exception. These functions
  return and accept a single exception object, rather than the triple
  arguments of the now-deprecated "PyErr_Fetch()" and
  "PyErr_Restore()". This is less error prone and a bit more
  efficient. (Contributed by Mark Shannon in gh-101578.)

* Add "_PyErr_ChainExceptions1", which takes an exception instance, to
  replace the legacy-API "_PyErr_ChainExceptions", which is now
  deprecated. (Contributed by Mark Shannon in gh-101578.)

* Add "PyException_GetArgs()" and "PyException_SetArgs()" as
  convenience functions for retrieving and modifying the "args" passed
  to the exception's constructor. (Contributed by Mark Shannon in
  gh-101578.)

* Add "PyErr_DisplayException()", which takes an exception instance,
  to replace the legacy-api "PyErr_Display()". (Contributed by Irit
  Katriel in gh-102755).

* **PEP 683**: Introduced Immortal Objects to Python which allows
  objects to bypass reference counts and introduced changes to the
  C-API:

  * "_Py_IMMORTAL_REFCNT": The reference count that defines an object
       as immortal.

  * "_Py_IsImmortal" Checks if an object has the immortal reference
    count.

  * "PyObject_HEAD_INIT" This will now initialize reference count to
       "_Py_IMMORTAL_REFCNT" when used with "Py_BUILD_CORE".

  * "SSTATE_INTERNED_IMMORTAL" An identifier for interned unicode
    objects
       that are immortal.

  * "SSTATE_INTERNED_IMMORTAL_STATIC" An identifier for interned
    unicode
       objects that are immortal and static

  * "sys.getunicodeinternedsize" This returns the total number of
    unicode
       objects that have been interned. This is now needed for
       refleak.py to correctly track reference counts and allocated
       blocks

  (Contributed by Eddie Elizondo in gh-84436.)


Porting to Python 3.12
----------------------

* Legacy Unicode APIs based on "Py_UNICODE*" representation has been
  removed. Please migrate to APIs based on UTF-8 or "wchar_t*".

* Argument parsing functions like "PyArg_ParseTuple()" doesn't support
  "Py_UNICODE*" based format (e.g. "u", "Z") anymore. Please migrate
  to other formats for Unicode like "s", "z", "es", and "U".

* "tp_weaklist" for all static builtin types is always "NULL". This is
  an internal-only field on "PyTypeObject" but we're pointing out the
  change in case someone happens to be accessing the field directly
  anyway.  To avoid breakage, consider using the existing public C-API
  instead, or, if necessary, the (internal-only)
  "_PyObject_GET_WEAKREFS_LISTPTR()" macro.

* This internal-only "PyTypeObject.tp_subclasses" may now not be a
  valid object pointer.  Its type was changed to void* to reflect
  this.  We mention this in case someone happens to be accessing the
  internal-only field directly.

  To get a list of subclasses, call the Python method
  "__subclasses__()" (using "PyObject_CallMethod()", for example).

* Add support of more formatting options (left aligning, octals,
  uppercase hexadecimals, "intmax_t", "ptrdiff_t", "wchar_t" C
  strings, variable width and precision) in "PyUnicode_FromFormat()"
  and "PyUnicode_FromFormatV()". (Contributed by Serhiy Storchaka in
  gh-98836.)

* An unrecognized format character in "PyUnicode_FromFormat()" and
  "PyUnicode_FromFormatV()" now sets a "SystemError". In previous
  versions it caused all the rest of the format string to be copied
  as-is to the result string, and any extra arguments discarded.
  (Contributed by Serhiy Storchaka in gh-95781.)

* Fixed wrong sign placement in "PyUnicode_FromFormat()" and
  "PyUnicode_FromFormatV()". (Contributed by Philip Georgi in
  gh-95504.)

* Extension classes wanting to add a "__dict__" or weak reference slot
  should use "Py_TPFLAGS_MANAGED_DICT" and
  "Py_TPFLAGS_MANAGED_WEAKREF" instead of "tp_dictoffset" and
  "tp_weaklistoffset", respectively. The use of "tp_dictoffset" and
  "tp_weaklistoffset" is still supported, but does not fully support
  multiple inheritance (gh-95589), and performance may be worse.
  Classes declaring "Py_TPFLAGS_MANAGED_DICT" should call
  "_PyObject_VisitManagedDict()" and "_PyObject_ClearManagedDict()" to
  traverse and clear their instance's dictionaries. To clear weakrefs,
  call "PyObject_ClearWeakRefs()", as before.

* The "PyUnicode_FSDecoder()" function no longer accepts bytes-like
  paths, like "bytearray" and "memoryview" types: only the exact
  "bytes" type is accepted for bytes strings. (Contributed by Victor
  Stinner in gh-98393.)

* The "Py_CLEAR", "Py_SETREF" and "Py_XSETREF" macros now only
  evaluate their arguments once. If an argument has side effects,
  these side effects are no longer duplicated. (Contributed by Victor
  Stinner in gh-98724.)

* The interpreter's error indicator is now always normalized. This
  means that "PyErr_SetObject()", "PyErr_SetString()" and the other
  functions that set the error indicator now normalize the exception
  before storing it. (Contributed by Mark Shannon in gh-101578.)

* "_Py_RefTotal" is no longer authoritative and only kept around for
  ABI compabitility.  Note that it is an internal global and only
  available on debug builds.  If you happen to be using it then you'll
  need to start using "_Py_GetGlobalRefTotal()".

* The following functions now select an appropriate metaclass for the
  newly created type:

  * "PyType_FromSpec()"

  * "PyType_FromSpecWithBases()"

  * "PyType_FromModuleAndSpec()"

  Creating classes whose metaclass overrides "tp_new" is deprecated,
  and in Python 3.14+ it will be disallowed. Note that these functions
  ignore "tp_new" of the metaclass, possibly allowing incomplete
  initialization.

  Note that "PyType_FromMetaclass()" (added in Python 3.12) already
  disallows creating classes whose metaclass overrides "tp_new".

* "PyOS_InputHook" and "PyOS_ReadlineFunctionPointer" are no longer
  called in subinterpreters. This is because clients generally rely on
  process-wide global state (since these callbacks have no way of
  recovering extension module state).

  This also avoids situations where extensions may find themselves
  running in a subinterpreter that they don't support (or haven't yet
  been loaded in). See gh-104668 for more info.


Deprecated
----------

* Deprecate global configuration variable:

  * "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_FileSystemDefaultEncodeErrors": use
    "PyConfig.filesystem_errors"

  * "Py_UTF8Mode": use "PyPreConfig.utf8_mode" (see
    "Py_PreInitialize()")

  The "Py_InitializeFromConfig()" API should be used with "PyConfig"
  instead. (Contributed by Victor Stinner in gh-77782.)

* Creating immutable types ("Py_TPFLAGS_IMMUTABLETYPE") with mutable
  bases is deprecated and will be disabled in Python 3.14.

* The "structmember.h" header is deprecated, though it continues to be
  available and there are no plans to remove it.

  Its contents are now available just by including "Python.h", with a
  "Py" prefix added if it was missing:

  * "PyMemberDef", "PyMember_GetOne()" and "PyMember_SetOne()"

  * Type macros like "Py_T_INT", "Py_T_DOUBLE", etc. (previously
    "T_INT", "T_DOUBLE", etc.)

  * The flags "Py_READONLY" (previously "READONLY") and
    "Py_AUDIT_READ" (previously all uppercase)

  Several items are not exposed from "Python.h":

  * "T_OBJECT" (use "Py_T_OBJECT_EX")

  * "T_NONE" (previously undocumented, and pretty quirky)

  * The macro "WRITE_RESTRICTED" which does nothing.

  * The macros "RESTRICTED" and "READ_RESTRICTED", equivalents of
    "Py_AUDIT_READ".

  * In some configurations, "<stddef.h>" is not included from
    "Python.h". It should be included manually when using
    "offsetof()".

  The deprecated header continues to provide its original contents
  under the original names. Your old code can stay unchanged, unless
  the extra include and non-namespaced macros bother you greatly.

  (Contributed in gh-47146 by Petr Viktorin, based on earlier work by
  Alexander Belopolsky and Matthias Braun.)

* "PyErr_Fetch()" and "PyErr_Restore()" are deprecated. Use
  "PyErr_GetRaisedException()" and "PyErr_SetRaisedException()"
  instead. (Contributed by Mark Shannon in gh-101578.)

* "PyErr_Display()" is deprecated. Use "PyErr_DisplayException()"
  instead. (Contributed by Irit Katriel in gh-102755).

* "_PyErr_ChainExceptions" is deprecated. Use
  "_PyErr_ChainExceptions1" instead. (Contributed by Irit Katriel in
  gh-102192.)

* Using "PyType_FromSpec()", "PyType_FromSpecWithBases()" or
  "PyType_FromModuleAndSpec()" to create a class whose metaclass
  overrides "tp_new" is deprecated. Call the metaclass instead.


Removed
-------

* Remove the "token.h" header file. There was never any public
  tokenizer C API. The "token.h" header file was only designed to be
  used by Python internals. (Contributed by Victor Stinner in
  gh-92651.)

* Legacy Unicode APIs have been removed. See **PEP 623** for detail.

     * "PyUnicode_WCHAR_KIND"

     * "PyUnicode_AS_UNICODE()"

     * "PyUnicode_AsUnicode()"

     * "PyUnicode_AsUnicodeAndSize()"

     * "PyUnicode_AS_DATA()"

     * "PyUnicode_FromUnicode()"

     * "PyUnicode_GET_SIZE()"

     * "PyUnicode_GetSize()"

     * "PyUnicode_GET_DATA_SIZE()"

* Remove the "PyUnicode_InternImmortal()" function macro. (Contributed
  by Victor Stinner in gh-85858.)

* Remove "Jython" compatibility hacks from several stdlib modules and
  tests. (Contributed by Nikita Sobolev in gh-99482.)

* Remove "_use_broken_old_ctypes_structure_semantics_" flag from
  "ctypes" module. (Contributed by Nikita Sobolev in gh-99285.)
