What’s New In Python 3.12
*************************

Editor:
   Adam Turner

This article explains the new features in Python 3.12, compared to
3.11. Python 3.12 was released on October 2, 2023. For full details,
see the changelog.

See also: **PEP 693** – Python 3.12 Release Schedule


Summary – Release highlights
============================

Python 3.12 is the latest stable release of the Python programming
language, with a mix of changes to the language and the standard
library. The library changes focus on cleaning up deprecated APIs,
usability, and correctness. Of note, the "distutils" package has been
removed from the standard library. Filesystem support in "os" and
"pathlib" has seen a number of improvements, and several modules have
better performance.

The language changes focus on usability, as *f-strings* have had many
limitations removed and ‘Did you mean …’ suggestions continue to
improve. The new type parameter syntax and "type" statement improve
ergonomics for using *generic types* and *type aliases* with static
type checkers.

This article doesn’t attempt to provide a complete specification of
all new features, but instead gives a convenient overview. For full
details, you should refer to the documentation, such as the  Library
Reference and Language Reference. If you want to understand the
complete implementation and design rationale for a change, refer to
the PEP for a particular new feature; but note that PEPs usually are
not kept up-to-date once a feature has been fully implemented.

======================================================================

New syntax features:

* PEP 695, type parameter syntax and the "type" statement

New grammar features:

* PEP 701, *f-strings* in the grammar

Interpreter improvements:

* PEP 684, a unique per-interpreter *GIL*

* PEP 669, low impact monitoring

* Improved ‘Did you mean …’ suggestions for "NameError",
  "ImportError", and "SyntaxError" exceptions

Python data model improvements:

* PEP 688, using the buffer protocol from Python

Significant improvements in the standard library:

* The "pathlib.Path" class now supports subclassing

* The "os" module received several improvements for Windows support

* A command-line interface has been added to the "sqlite3" module

* "isinstance()" checks against "runtime-checkable protocols" enjoy a
  speed up of between two and 20 times

* The "asyncio" package has had a number of performance improvements,
  with some benchmarks showing a 75% speed up.

* A command-line interface has been added to the "uuid" module

* Due to the changes in PEP 701, producing tokens via the "tokenize"
  module is up to 64% faster.

Security improvements:

* Replace the builtin "hashlib" implementations of SHA1, SHA3,
  SHA2-384, SHA2-512, and MD5 with formally verified code from the
  HACL* project. These builtin implementations remain as fallbacks
  that are only used when OpenSSL does not provide them.

C API improvements:

* PEP 697, unstable C API tier

* PEP 683, immortal objects

CPython implementation improvements:

* PEP 709, comprehension inlining

* CPython support for the Linux "perf" profiler

* Implement stack overflow protection on supported platforms

New typing features:

* PEP 692, using "TypedDict" to annotate ***kwargs*

* PEP 698, "typing.override()" decorator

Important deprecations, removals or restrictions:

* **PEP 623**: Remove "wstr" from Unicode objects in Python’s C API,
  reducing the size of every "str" object by at least 8 bytes.

* **PEP 632**: Remove the "distutils" package. See the migration guide
  for advice replacing the APIs it provided. The third-party
  Setuptools package continues to provide "distutils", if you still
  require it in Python 3.12 and beyond.

* gh-95299: Do not pre-install "setuptools" in virtual environments
  created with "venv". This means that "distutils", "setuptools",
  "pkg_resources", and "easy_install" will no longer available by
  default; to access these run "pip install setuptools" in the
  activated virtual environment.

* The "asynchat", "asyncore", and "imp" modules have been removed,
  along with several "unittest.TestCase" method aliases.


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


PEP 695: Type Parameter Syntax
------------------------------

Generic classes and functions under **PEP 484** were declared using a
verbose syntax that left the scope of type parameters unclear and
required explicit declarations of variance.

**PEP 695** introduces a new, more compact and explicit way to create
generic classes and functions:

   def max[T](args: Iterable[T]) -> T:
       ...

   class list[T]:
       def __getitem__(self, index: int, /) -> T:
           ...

       def append(self, element: T) -> None:
           ...

In addition, the PEP introduces a new way to declare type aliases
using the "type" statement, which creates an instance of
"TypeAliasType":

   type Point = tuple[float, float]

Type aliases can also be generic:

   type Point[T] = tuple[T, T]

The new syntax allows declaring "TypeVarTuple" and "ParamSpec"
parameters, as well as "TypeVar" parameters with bounds or
constraints:

   type IntFunc[**P] = Callable[P, int]  # ParamSpec
   type LabeledTuple[*Ts] = tuple[str, *Ts]  # TypeVarTuple
   type HashableSequence[T: Hashable] = Sequence[T]  # TypeVar with bound
   type IntOrStrSequence[T: (int, str)] = Sequence[T]  # TypeVar with constraints

The value of type aliases and the bound and constraints of type
variables created through this syntax are evaluated only on demand
(see lazy evaluation). This means type aliases are able to refer to
other types defined later in the file.

Type parameters declared through a type parameter list are visible
within the scope of the declaration and any nested scopes, but not in
the outer scope. For example, they can be used in the type annotations
for the methods of a generic class or in the class body. However, they
cannot be used in the module scope after the class is defined. See
Type parameter lists for a detailed description of the runtime
semantics of type parameters.

In order to support these scoping semantics, a new kind of scope is
introduced, the annotation scope. Annotation scopes behave for the
most part like function scopes, but interact differently with
enclosing class scopes. In Python 3.13, *annotations* will also be
evaluated in annotation scopes.

See **PEP 695** for more details.

(PEP written by Eric Traut. Implementation by Jelle Zijlstra, Eric
Traut, and others in gh-103764.)


PEP 701: Syntactic formalization of f-strings
---------------------------------------------

**PEP 701** lifts some restrictions on the usage of *f-strings*.
Expression components inside f-strings can now be any valid Python
expression, including strings reusing the same quote as the containing
f-string, multi-line expressions, comments, backslashes, and unicode
escape sequences. Let’s cover these in detail:

* Quote reuse: in Python 3.11, reusing the same quotes as the
  enclosing f-string raises a "SyntaxError", forcing the user to
  either use other available quotes (like using double quotes or
  triple quotes if the f-string uses single quotes). In Python 3.12,
  you can now do things like this:

  >>> songs = ['Take me back to Eden', 'Alkaline', 'Ascensionism']
  >>> f"This is the playlist: {", ".join(songs)}"
  'This is the playlist: Take me back to Eden, Alkaline, Ascensionism'

  Note that before this change there was no explicit limit in how
  f-strings can be nested, but the fact that string quotes cannot be
  reused inside the expression component of f-strings made it
  impossible to nest f-strings arbitrarily. In fact, this is the most
  nested f-string that could be written:

  >>> f"""{f'''{f'{f"{1+1}"}'}'''}"""
  '2'

  As now f-strings can contain any valid Python expression inside
  expression components, it is now possible to nest f-strings
  arbitrarily:

  >>> f"{f"{f"{f"{f"{f"{1+1}"}"}"}"}"}"
  '2'

* Multi-line expressions and comments: In Python 3.11, f-string
  expressions must be defined in a single line, even if the expression
  within the f-string could normally span multiple lines (like literal
  lists being defined over multiple lines), making them harder to
  read. In Python 3.12 you can now define f-strings spanning multiple
  lines, and add inline comments:

  >>> f"This is the playlist: {", ".join([
  ...     'Take me back to Eden',  # My, my, those eyes like fire
  ...     'Alkaline',              # Not acid nor alkaline
  ...     'Ascensionism'           # Take to the broken skies at last
  ... ])}"
  'This is the playlist: Take me back to Eden, Alkaline, Ascensionism'

* Backslashes and unicode characters: before Python 3.12 f-string
  expressions couldn’t contain any "\" character. This also affected
  unicode escape sequences (such as "\N{snowman}") as these contain
  the "\N" part that previously could not be part of expression
  components of f-strings. Now, you can define expressions like this:

  >>> print(f"This is the playlist: {"\n".join(songs)}")
  This is the playlist: Take me back to Eden
  Alkaline
  Ascensionism
  >>> print(f"This is the playlist: {"\N{BLACK HEART SUIT}".join(songs)}")
  This is the playlist: Take me back to Eden♥Alkaline♥Ascensionism

See **PEP 701** for more details.

As a positive side-effect of how this feature has been implemented (by
parsing f-strings with **the PEG parser**), now error messages for
f-strings are more precise and include the exact location of the
error. For example, in Python 3.11, the following f-string raises a
"SyntaxError":

   >>> my_string = f"{x z y}" + f"{1 + 1}"
     File "<stdin>", line 1
       (x z y)
        ^^^
   SyntaxError: f-string: invalid syntax. Perhaps you forgot a comma?

but the error message doesn’t include the exact location of the error
within the line and also has the expression artificially surrounded by
parentheses. In Python 3.12, as f-strings are parsed with the PEG
parser, error messages can be more precise and show the entire line:

   >>> my_string = f"{x z y}" + f"{1 + 1}"
     File "<stdin>", line 1
       my_string = f"{x z y}" + f"{1 + 1}"
                      ^^^
   SyntaxError: invalid syntax. Perhaps you forgot a comma?

(Contributed by Pablo Galindo, Batuhan Taskaya, Lysandros Nikolaou,
Cristián Maureira-Fredes and Marta Gómez in gh-102856. PEP written by
Pablo Galindo, Batuhan Taskaya, Lysandros Nikolaou and Marta Gómez).


PEP 684: A Per-Interpreter GIL
------------------------------

**PEP 684** introduces a per-interpreter *GIL*, so that sub-
interpreters may now be created with a unique GIL per interpreter.
This allows Python programs to take full advantage of multiple CPU
cores. This is currently only available through the C-API, though a
Python API is **anticipated for 3.13**.

Use the new "Py_NewInterpreterFromConfig()" function to create an
interpreter with its own GIL:

   PyInterpreterConfig config = {
       .check_multi_interp_extensions = 1,
       .gil = PyInterpreterConfig_OWN_GIL,
   };
   PyThreadState *tstate = NULL;
   PyStatus status = Py_NewInterpreterFromConfig(&tstate, &config);
   if (PyStatus_Exception(status)) {
       return -1;
   }
   /* The new interpreter is now active in the current thread. */

For further examples how to use the C-API for sub-interpreters with a
per-interpreter GIL, see Modules/_xxsubinterpretersmodule.c.

(Contributed by Eric Snow in gh-104210, etc.)


PEP 669: Low impact monitoring for CPython
------------------------------------------

**PEP 669** defines a new "API" for profilers, debuggers, and other
tools to monitor events in CPython. It covers a wide range of events,
including calls, returns, lines, exceptions, jumps, and more. This
means that you only pay for what you use, providing support for near-
zero overhead debuggers and coverage tools. See  "sys.monitoring" for
details.

(Contributed by Mark Shannon in gh-103082.)


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.)


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
two times. See **PEP 709** for further details.

Comprehension iteration variables remain isolated and don’t overwrite
a variable of the same name in the outer scope, nor are they visible
after the comprehension. 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.

* The "symtable" module will no longer produce child symbol tables for
  each comprehension; instead, the comprehension’s locals will be
  included in the parent function’s symbol table.

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

* A comprehension iterating directly over "locals()" (e.g. "[k for k
  in locals()]") may see “RuntimeError: dictionary changed size during
  iteration” when run under tracing (e.g. code coverage measurement).
  This is the same behavior already seen in e.g. "for k in locals():".
  To avoid the error, first create a list of keys to iterate over:
  "keys = list(locals()); [k for k in keys]".

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


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 Related to Type Hints
==================================

This section covers major changes affecting **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.

**PEP 692** 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.

(Contributed by Franek Magiera in gh-103629.)


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

A new decorator "typing.override()" has been added to the "typing"
module. It indicates to type checkers that the method is intended to
override a method in a superclass. This allows type checkers to catch
mistakes where a method that is intended to override something in a
base class does not in fact do so.

Example:

   from typing import override

   class Base:
     def get_color(self) -> str:
       return "blue"

   class GoodChild(Base):
     @override  # ok: overrides Base.get_color
     def get_color(self) -> str:
       return "yellow"

   class BadChild(Base):
     @override  # type checker error: does not override Base.get_color
     def get_colour(self) -> str:
       return "red"

See **PEP 698** for more details.

(Contributed by Steven Troxler in gh-101561.)


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

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

* 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.)

* 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.)

* Exceptions raised in a class or type’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.)

* 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.)

* 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.)

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

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

* "sum()" now uses Neumaier summation to improve accuracy and
  commutativity when summing floats or mixed ints and floats.
  (Contributed by Raymond Hettinger in gh-100425.)

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

* 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 tarfile extraction filters for
  details. In Python 3.14, the default will switch to "'data'".
  (Contributed by Petr Viktorin in **PEP 706**.)

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

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


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

* None.


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.)

* Add "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 Oren in gh-102853,
  gh-104140, and gh-104138)

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

* The event loop now uses the best available child watcher for each
  platform ("asyncio.PidfdChildWatcher" if supported and
  "asyncio.ThreadedChildWatcher" otherwise), so manually configuring a
  child watcher is not recommended. (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 Oren 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 "calendar.Month" and "calendar.Day" defining months of the
  year and days of the week. (Contributed by Prince Roshan in
  gh-103636.)


csv
---

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


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 "dis.hasarg"
  collection instead. (Contributed by Irit Katriel in gh-94216.)

* Add the "dis.hasexc" collection to signify instructions that set an
  exception handler. (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.)


importlib.resources
-------------------

* "importlib.resources.as_file()" now supports resource directories.
  (Contributed by Jason R. Coombs in gh-97930.)

* Rename first parameter of "importlib.resources.files()" to *anchor*.
  (Contributed by Jason R. Coombs in gh-100598.)


inspect
-------

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

* Add "inspect.getasyncgenstate()" and "inspect.getasyncgenlocals()"
  for determining the current state of asynchronous generators.
  (Contributed by Thomas Krennwallner in gh-79940.)

* 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. (Contributed by Alex Waygood in
  gh-103193.)


itertools
---------

* Add "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
----

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

* Extend "math.nextafter()" to include a *steps* argument for moving
  up or down multiple steps at a time. (Contributed by Matthias
  Goergens, Mark Dickinson, and Raymond Hettinger in gh-94906.)


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.)

* As of 3.12.4, "os.mkdir()" and "os.makedirs()" on Windows now
  support passing a *mode* value of "0o700" to apply access control to
  the new directory. This implicitly affects "tempfile.mkdtemp()" and
  is a mitigation for CVE-2024-4030. Other values for *mode* continue
  to be ignored. (Contributed by Steve Dower in gh-118486.)


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.)


pathlib
-------

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

* Add "pathlib.Path.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 gh-84538.)

* 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.


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.)


random
------

* Add "random.binomialvariate()". (Contributed by Raymond Hettinger in
  gh-81620.)

* Add a default of "lambd=1.0" to "random.expovariate()". (Contributed
  by Raymond Hettinger in gh-100234.)


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.
  (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 "sqlite3.Connection.autocommit" attribute to
  "sqlite3.Connection" and the *autocommit* parameter to
  "sqlite3.connect()" to control **PEP 249**-compliant transaction
  handling. (Contributed by Erlend E. Aasland in gh-83638.)

* Add *entrypoint* keyword-only parameter to
  "sqlite3.Connection.load_extension()", for overriding the SQLite
  extension entry point. (Contributed by Erlend E. Aasland in
  gh-103015.)

* Add "sqlite3.Connection.getconfig()" and
  "sqlite3.Connection.setconfig()" to "sqlite3.Connection" to make
  configuration changes to a database connection. (Contributed by
  Erlend E. Aasland in gh-103489.)


statistics
----------

* Extend "statistics.correlation()" to include as a "ranked" method
  for computing the Spearman correlation of ranked data. (Contributed
  by Raymond Hettinger in gh-95861.)


sys
---

* Add the "sys.monitoring" namespace to expose the new PEP 669
  monitoring API. (Contributed by Mark Shannon in gh-103082.)

* 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.)

* "sys.setrecursionlimit()" and "sys.getrecursionlimit()". The
  recursion limit now applies only to Python code. Builtin functions
  do not use the recursion limit, but are protected by a different
  mechanism that prevents recursion from causing a virtual machine
  crash.


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.

* As of 3.12.4 on Windows, the default mode "0o700" used by
  "tempfile.mkdtemp()" now limits access to the new directory due to
  changes to "os.mkdir()". This is a mitigation for CVE-2024-4030.
  (Contributed by Steve Dower in gh-118486.)


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.)


tokenize
--------

* The "tokenize" module includes the changes introduced in **PEP
  701**. (Contributed by Marta Gómez Macías and Pablo Galindo in
  gh-102856.) See Porting to Python 3.12 for more information on the
  changes to the "tokenize" module.


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.)


typing
------

* "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 many members may be
  slower than in Python 3.11. (Contributed by Alex Waygood in gh-74690
  and gh-103193.)

* All "typing.TypedDict" and "typing.NamedTuple" classes now have the
  "__orig_bases__" attribute. (Contributed by Adrian Garcia Badaracco
  in gh-103699.)

* Add "frozen_default" parameter to "typing.dataclass_transform()".
  (Contributed by Erik De Bonte in gh-99957.)


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

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


unittest
--------

Add a "--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 gh-48330)


uuid
----

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


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

* Remove "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.)

* Add 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 Donghee 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 Oren in gh-103793.)

* The "tokenize.tokenize()" and "tokenize.generate_tokens()" functions
  are up to 64% faster as a side effect of the changes required to
  cover **PEP 701** in the "tokenize" module. (Contributed by Marta
  Gómez Macías and Pablo Galindo in gh-102856.)

* Speed up "super()" method calls and attribute loads via the new
  "LOAD_SUPER_ATTR" instruction. (Contributed by Carl Meyer and
  Vladimir Matveev in gh-103497.)


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

* Remove 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.)

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

* Remove the "PRECALL" instruction. (Contributed by Mark Shannon in
  gh-92925.)

* Add the "BINARY_SLICE" and "STORE_SLICE" instructions. (Contributed
  by Mark Shannon in gh-94163.)

* Add the "CALL_INTRINSIC_1" instructions. (Contributed by Mark
  Shannon in gh-99005.)

* Add the "CALL_INTRINSIC_2" instruction. (Contributed by Irit Katriel
  in gh-101799.)

* Add the "CLEANUP_THROW" instruction. (Contributed by Brandt Bucher
  in gh-90997.)

* Add the "END_SEND" instruction. (Contributed by Mark Shannon in
  gh-103082.)

* Add the "LOAD_FAST_AND_CLEAR" instruction as part of the
  implementation of **PEP 709**. (Contributed by Carl Meyer in
  gh-101441.)

* Add the "LOAD_FAST_CHECK" instruction. (Contributed by Dennis
  Sweeney in gh-93143.)

* Add the "LOAD_FROM_DICT_OR_DEREF", "LOAD_FROM_DICT_OR_GLOBALS", and
  "LOAD_LOCALS" opcodes as part of the implementation of **PEP 695**.
  Remove the "LOAD_CLASSDEREF" opcode, which can be replaced with
  "LOAD_LOCALS" plus "LOAD_FROM_DICT_OR_DEREF". (Contributed by Jelle
  Zijlstra in gh-103764.)

* Add the "LOAD_SUPER_ATTR" instruction. (Contributed by Carl Meyer
  and Vladimir Matveev in gh-103497.)

* Add the "RETURN_CONST" instruction. (Contributed by Wenyang Wang in
  gh-101632.)


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
==========

* "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 "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.)

* "asyncio":

  * The child watcher classes "asyncio.MultiLoopChildWatcher",
    "asyncio.FastChildWatcher", "asyncio.AbstractChildWatcher" and
    "asyncio.SafeChildWatcher" are deprecated and will be removed in
    Python 3.14. (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.)

  * 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.)

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

* "collections.abc": 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.)

* "datetime": "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.)

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

* "importlib.abc": Deprecated the following 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.)

* "itertools": Deprecate the support for copy, deepcopy, and pickle
  operations, which is undocumented, inefficient, historically buggy,
  and inconsistent. 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": 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.

* "pkgutil": "pkgutil.find_loader()" and "pkgutil.get_loader()" are
  deprecated and will be removed in Python 3.14; use
  "importlib.util.find_spec()" instead. (Contributed by Nikita Sobolev
  in gh-97850.)

* "pty": The module 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. (Contributed by Soumendra Ganguly and Gregory P. Smith in
  gh-85984.)

* "os":

  * 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.)

  * On POSIX platforms, "os.fork()" can now raise a
    "DeprecationWarning" when it can detect being called from a
    multithreaded process. There has always been a fundamental
    incompatibility with the POSIX platform when doing so. Even if
    such code *appeared* to work. We added the warning to raise
    awareness as issues encountered by code doing this are becoming
    more frequent. See the "os.fork()" documentation for more details
    along with this discussion on fork being incompatible with threads
    for *why* we’re now surfacing this longstanding platform
    compatibility problem to developers.

  When this warning appears due to usage of "multiprocessing" or
  "concurrent.futures" the fix is to use a different "multiprocessing"
  start method such as ""spawn"" or ""forkserver"".

* "shutil": The *onerror* argument of "shutil.rmtree()" is deprecated;
  use *onexc* instead. (Contributed by Irit Katriel in gh-102828.)

* "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.)

* "sys": 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.)

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

* "typing":

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

  * "typing.ByteString", deprecated since Python 3.9, now causes a
    "DeprecationWarning" to be emitted when it is used. (Contributed
    by Alex Waygood in gh-91896.)

* "xml.etree.ElementTree": The 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. (Contributed by Jacob Walls in
  gh-83122.)

* The 3-arg signatures (type, value, traceback) of "coroutine
  throw()", "generator throw()" and "async generator throw()" 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.)

* Setting "__package__" or "__cached__" on a module is deprecated, and
  will cease to be set or taken into consideration by the import
  system in Python 3.14. (Contributed by Brett Cannon in gh-65961.)

* 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:
  "~int(x)". (Contributed by Tim Hoffmann in gh-103487.)

* Accessing "co_lnotab" on code objects was deprecated in Python 3.10
  via **PEP 626**, but it only got a proper "DeprecationWarning" in
  3.12, therefore it will be removed in 3.14. (Contributed by Nikita
  Sobolev in gh-101866.)


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"

Other modules:

* "lib2to3", and the **2to3** program (gh-84540)

APIs:

* "configparser.LegacyInterpolation" (gh-90765)

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

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

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

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

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

* "unittest.TestProgram.usageExit()" (gh-67048)

* "webbrowser.MacOSX" (gh-86421)

* "classmethod" descriptor chaining (gh-89519)

* "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 (gh-106531)


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

The following APIs have been deprecated and will be removed in Python
3.14.

* "argparse": The *type*, *choices*, and *metavar* parameters of
  "argparse.BooleanOptionalAction"

* "ast":

  * "ast.Num"

  * "ast.Str"

  * "ast.Bytes"

  * "ast.NameConstant"

  * "ast.Ellipsis"

* "asyncio":

  * "asyncio.MultiLoopChildWatcher"

  * "asyncio.FastChildWatcher"

  * "asyncio.AbstractChildWatcher"

  * "asyncio.SafeChildWatcher"

  * "asyncio.set_child_watcher()"

  * "asyncio.get_child_watcher()",

  * "asyncio.AbstractEventLoopPolicy.set_child_watcher()"

  * "asyncio.AbstractEventLoopPolicy.get_child_watcher()"

* "collections.abc": "collections.abc.ByteString".

* "email": the *isdst* parameter in "email.utils.localtime()".

* "importlib.abc":

  * "importlib.abc.ResourceReader"

  * "importlib.abc.Traversable"

  * "importlib.abc.TraversableResources"

* "itertools": Support for copy, deepcopy, and pickle operations.

* "pkgutil":

  * "pkgutil.find_loader()"

  * "pkgutil.get_loader()".

* "pty":

  * "pty.master_open()"

  * "pty.slave_open()"

* "shutil": The *onerror* argument of "shutil.rmtree()"

* "typing": "typing.ByteString"

* "xml.etree.ElementTree": Testing the truth value of an
  "xml.etree.ElementTree.Element".

* The "__package__" and "__cached__" attributes on module objects.

* The "co_lnotab" attribute of code objects.


Pending Removal in Python 3.15
------------------------------

The following APIs have been deprecated and will be removed in Python
3.15.

APIs:

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


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.

* "array"’s "'u'" format code (gh-57281)

* "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
=======


asynchat and asyncore
---------------------

* These two modules 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.)


configparser
------------

* 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.


distutils
---------

* 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.)


ensurepip
---------

* 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.)


enum
----

* Remove "enum"’s "EnumMeta.__getattr__", which is no longer needed
  for enum attribute access. (Contributed by Ethan Furman in
  gh-95083.)


ftplib
------

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


gzip
----

* Remove the "filename" attribute of "gzip"’s "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.)


hashlib
-------

* Remove the pure Python implementation of "hashlib"’s
  "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.)


importlib
---------

* 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", "importlib.util.set_loader" and
    "importlib.util.module_for_loader" have all been removed.
    (Contributed by Brett Cannon and Nikita Sobolev in gh-65961 and
    gh-97850.)

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

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


imp
---

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

  To migrate, consult the following correspondence table:

     +-----------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------+
     | imp                               | importlib                                                                                                                                      |
     |===================================|================================================================================================================================================|
     | "imp.NullImporter"                | Insert "None" into "sys.path_importer_cache"                                                                                                   |
     +-----------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------+
     | "imp.cache_from_source()"         | "importlib.util.cache_from_source()"                                                                                                           |
     +-----------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------+
     | "imp.find_module()"               | "importlib.util.find_spec()"                                                                                                                   |
     +-----------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------+
     | "imp.get_magic()"                 | "importlib.util.MAGIC_NUMBER"                                                                                                                  |
     +-----------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------+
     | "imp.get_suffixes()"              | "importlib.machinery.SOURCE_SUFFIXES", "importlib.machinery.EXTENSION_SUFFIXES", and "importlib.machinery.BYTECODE_SUFFIXES"                   |
     +-----------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------+
     | "imp.get_tag()"                   | "sys.implementation.cache_tag"                                                                                                                 |
     +-----------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------+
     | "imp.load_module()"               | "importlib.import_module()"                                                                                                                    |
     +-----------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------+
     | "imp.new_module(name)"            | "types.ModuleType(name)"                                                                                                                       |
     +-----------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------+
     | "imp.reload()"                    | "importlib.reload()"                                                                                                                           |
     +-----------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------+
     | "imp.source_from_cache()"         | "importlib.util.source_from_cache()"                                                                                                           |
     +-----------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------+
     | "imp.load_source()"               | *See below*                                                                                                                                    |
     +-----------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------+

  Replace "imp.load_source()" with:

     import importlib.util
     import importlib.machinery

     def load_source(modname, filename):
         loader = importlib.machinery.SourceFileLoader(modname, filename)
         spec = importlib.util.spec_from_file_location(modname, filename, loader=loader)
         module = importlib.util.module_from_spec(spec)
         # The module is always executed and not cached in sys.modules.
         # Uncomment the following line to cache the module.
         # sys.modules[module.__name__] = module
         loader.exec_module(module)
         return module

* Remove "imp" functions and attributes with no replacements:

  * Undocumented functions:

    * "imp.init_builtin()"

    * "imp.load_compiled()"

    * "imp.load_dynamic()"

    * "imp.load_package()"

  * "imp.lock_held()", "imp.acquire_lock()", "imp.release_lock()": the
    locking scheme has changed in Python 3.3 to per-module locks.

  * "imp.find_module()" constants: "SEARCH_ERROR", "PY_SOURCE",
    "PY_COMPILED", "C_EXTENSION", "PY_RESOURCE", "PKG_DIRECTORY",
    "C_BUILTIN", "PY_FROZEN", "PY_CODERESOURCE", "IMP_HOOK".


io
--

* Remove "io"’s "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.)


locale
------

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


smtpd
-----

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


sqlite3
-------

* 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.)


ssl
---

* Remove "ssl"’s "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.)

* 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 "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 the server hostname. Code is
  subject to CWE-295 (Improper Certificate Validation). (Contributed
  by Victor Stinner in gh-94199.)


unittest
--------

* Remove many long-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 3.5).

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

  (Contributed by Serhiy Storchaka in gh-89325.)


webbrowser
----------

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


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 "zipimport"’s "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.)


Others
------

* Remove the "suspicious" rule from the documentation "Makefile" and
  "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.)

* 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.)


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.)

* Remove "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-
  integer 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.

* Remove 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
  Donghee 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.

* The output of the "tokenize.tokenize()" and
  "tokenize.generate_tokens()" functions is now changed due to the
  changes introduced in **PEP 701**. This means that "STRING" tokens
  are not emitted any more for f-strings and the tokens described in
  **PEP 701** are now produced instead: "FSTRING_START",
  "FSTRING_MIDDLE" and "FSTRING_END" are now emitted for f-string
  “string” parts in addition to the appropriate tokens for the
  tokenization in the expression components. For example for the
  f-string "f"start {1+1} end"" the old version of the tokenizer
  emitted:

     1,0-1,18:           STRING         'f"start {1+1} end"'

  while the new version emits:

     1,0-1,2:            FSTRING_START  'f"'
     1,2-1,8:            FSTRING_MIDDLE 'start '
     1,8-1,9:            OP             '{'
     1,9-1,10:           NUMBER         '1'
     1,10-1,11:          OP             '+'
     1,11-1,12:          NUMBER         '1'
     1,12-1,13:          OP             '}'
     1,13-1,17:          FSTRING_MIDDLE ' end'
     1,17-1,18:          FSTRING_END    '"'

  Additionally, there may be some minor behavioral changes as a
  consequence of the changes required to support **PEP 701**. Some of
  these changes include:

  * The "type" attribute of the tokens emitted when tokenizing some
    invalid Python characters such as "!" has changed from
    "ERRORTOKEN" to "OP".

  * Incomplete single-line strings now also raise
    "tokenize.TokenError" as incomplete multiline strings do.

  * Some incomplete or invalid Python code now raises
    "tokenize.TokenError" instead of returning arbitrary "ERRORTOKEN"
    tokens when tokenizing it.

  * Mixing tabs and spaces as indentation in the same file is not
    supported anymore and will raise a "TabError".

* The "threading" module now expects the "_thread" module to have an
  "_is_main_interpreter" attribute.  It is a function with no
  arguments that returns "True" if the current interpreter is the main
  interpreter.

  Any library or application that provides a custom "_thread" module
  should provide "_is_main_interpreter()". (See gh-112826.)


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 Donghee 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.

* Autoconf 2.71 and aclocal 1.16.4 is now required to regenerate
  "!configure". (Contributed by Christian Heimes in gh-89886.)

* Windows builds and macOS installers from python.org now use OpenSSL
  3.0.


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


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

* **PEP 697**: Introduce 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**: Add an 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.)

* Add 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.)

* Add 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.)

* Add 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.)

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

* Add "PyCode_AddWatcher()" and "PyCode_ClearWatcher()" APIs to
  register callbacks to receive notification on creation and
  destruction of code objects. (Contributed by Itamar Oren 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**: Introduce *Immortal Objects*, which allows objects to
  bypass reference counts, and related 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.)

* **PEP 684**: Add the new "Py_NewInterpreterFromConfig()" function
  and "PyInterpreterConfig", which may be used to create sub-
  interpreters with their own GILs. (See PEP 684: A Per-Interpreter
  GIL for more info.) (Contributed by Eric Snow in gh-104110.)

* In the limited C API version 3.12, "Py_INCREF()" and "Py_DECREF()"
  functions are now implemented as opaque function calls to hide
  implementation details. (Contributed by Victor Stinner in
  gh-105387.)


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.)

* Fix 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 compatibility.  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"
  ("__new__()" in Python).

  Since "tp_new" overrides almost everything "PyType_From*" functions
  do, the two are incompatible with each other. The existing behavior
  – ignoring the metaclass for several steps of type creation – is
  unsafe in general, since (meta)classes assume that "tp_new" was
  called. There is no simple general workaround. One of the following
  may work for you:

  * If you control the metaclass, avoid using "tp_new" in it:

    * If initialization can be skipped, it can be done in "tp_init"
      instead.

    * If the metaclass doesn’t need to be instantiated from Python,
      set its "tp_new" to "NULL" using the
      "Py_TPFLAGS_DISALLOW_INSTANTIATION" flag. This makes it
      acceptable for "PyType_From*" functions.

  * Avoid "PyType_From*" functions: if you don’t need C-specific
    features (slots or setting the instance size), create types by
    calling the metaclass.

  * If you *know* the "tp_new" can be skipped safely, filter the
    deprecation warning out using "warnings.catch_warnings()" from
    Python.

* "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.

* "PyLongObject" has had its internals changed for better performance.
  Although the internals of "PyLongObject" are private, they are used
  by some extension modules. The internal fields should no longer be
  accessed directly, instead the API functions beginning "PyLong_..."
  should be used instead. Two new *unstable* API functions are
  provided for efficient access to the value of "PyLongObject"s which
  fit into a single machine word:

  * "PyUnstable_Long_IsCompact()"

  * "PyUnstable_Long_CompactValue()"

* Custom allocators, set via "PyMem_SetAllocator()", are now required
  to be thread-safe, regardless of memory domain.  Allocators that
  don’t have their own state, including “hooks”, are not affected. If
  your custom allocator is not already thread-safe and you need
  guidance then please create a new GitHub issue and CC
  "@ericsnowcurrently".


Deprecated
----------

* 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.)

* 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_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. (Contributed by Victor Stinner in gh-77782.)

* Creating "immutable types" with mutable bases is deprecated and will
  be disabled in Python 3.14. (gh-95388)

* 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.


Pending Removal in Python 3.14
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* The "ma_version_tag" field in "PyDictObject" for extension modules
  (**PEP 699**; gh-101193).

* 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.

* Creating "immutable types" with mutable bases (gh-95388).


Pending Removal in Python 3.15
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* "PyImport_ImportModuleNoBlock()": use "PyImport_ImportModule()"

* "Py_UNICODE_WIDE" type: use "wchar_t"

* "Py_UNICODE" type: use "wchar_t"

* Python initialization functions:

  * "PySys_ResetWarnOptions()": clear "sys.warnoptions" and
    "warnings.filters"

  * "Py_GetExecPrefix()": get "sys.exec_prefix"

  * "Py_GetPath()": get "sys.path"

  * "Py_GetPrefix()": get "sys.prefix"

  * "Py_GetProgramFullPath()": get "sys.executable"

  * "Py_GetProgramName()": get "sys.executable"

  * "Py_GetPythonHome()": get "PyConfig.home" or the "PYTHONHOME"
    environment variable


Pending Removal in Future Versions
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The following APIs are deprecated and will be removed, although there
is currently no date scheduled for their removal.

* "Py_TPFLAGS_HAVE_FINALIZE": unneeded 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()": use "PySlice_Unpack()" and
  "PySlice_AdjustIndices()"

* "PyUnicode_AsDecodedObject()": use "PyCodec_Decode()"

* "PyUnicode_AsDecodedUnicode()": use "PyCodec_Decode()"

* "PyUnicode_AsEncodedObject()": use "PyCodec_Encode()"

* "PyUnicode_AsEncodedUnicode()": use "PyCodec_Encode()"

* "PyUnicode_READY()": unneeded since Python 3.12

* "PyErr_Display()": use "PyErr_DisplayException()"

* "_PyErr_ChainExceptions()": use "_PyErr_ChainExceptions1"

* "PyBytesObject.ob_shash" member: call "PyObject_Hash()" instead

* "PyDictObject.ma_version_tag" member

* Thread Local Storage (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()": unneeded since Python 3.7


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.)


Notable changes in 3.12.4
=========================


ipaddress
---------

* Fixed "is_global" and "is_private" behavior in "IPv4Address",
  "IPv6Address", "IPv4Network" and "IPv6Network".
