What's new in Python 3.14
*************************

Editor:
   TBD

This article explains the new features in Python 3.14, compared to
3.13.

For full details, see the changelog.

Note:

  Prerelease users should be aware that this document is currently in
  draft form. It will be updated substantially as Python 3.14 moves
  towards release, so it's worth checking back even after reading
  earlier versions.


Summary -- release highlights
=============================

* PEP 649: deferred evaluation of annotations

* PEP 741: Python Configuration C API

* PEP 758: Allow except and except* expressions without parentheses

* PEP 761: Discontinuation of PGP signatures

* PEP 765: Disallow return/break/continue that exit a finally block

* PEP 768: Safe external debugger interface for CPython

* A new type of interpreter


Incompatible changes
====================

On platforms other than macOS and Windows, the default start method
for "multiprocessing" and "ProcessPoolExecutor" switches from *fork*
to *forkserver*.

See (1) and (2) for details.

If you encounter "NameError"s or pickling errors coming out of
"multiprocessing" or "concurrent.futures", see the forkserver
restrictions.


New features
============


PEP 768: Safe external debugger interface for CPython
-----------------------------------------------------

**PEP 768** introduces a zero-overhead debugging interface that allows
debuggers and profilers to safely attach to running Python processes.
This is a significant enhancement to Python's debugging capabilities
allowing debuggers to forego unsafe alternatives. See below for how
this feature is leveraged to implement the new "pdb" module's remote
attaching capabilities.

The new interface provides safe execution points for attaching
debugger code without modifying the interpreter's normal execution
path or adding runtime overhead. This enables tools to inspect and
interact with Python applications in real-time without stopping or
restarting them — a crucial capability for high-availability systems
and production environments.

For convenience, CPython implements this interface through the "sys"
module with a "sys.remote_exec()" function:

   sys.remote_exec(pid, script_path)

This function allows sending Python code to be executed in a target
process at the next safe execution point. However, tool authors can
also implement the protocol directly as described in the PEP, which
details the underlying mechanisms used to safely attach to running
processes.

Here's a simple example that inspects object types in a running Python
process:

      import os
      import sys
      import tempfile

      # Create a temporary script
      with tempfile.NamedTemporaryFile(mode='w', suffix='.py', delete=False) as f:
          script_path = f.name
          f.write(f"import my_debugger; my_debugger.connect({os.getpid()})")
      try:
          # Execute in process with PID 1234
          print("Behold! An offering:")
          sys.remote_exec(1234, script_path)
      finally:
          os.unlink(script_path)

The debugging interface has been carefully designed with security in
mind and includes several mechanisms to control access:

* A "PYTHON_DISABLE_REMOTE_DEBUG" environment variable.

* A "-X disable-remote-debug" command-line option.

* A "--without-remote-debug" configure flag to completely disable the
  feature at build time.

A key implementation detail is that the interface piggybacks on the
interpreter's existing evaluation loop and safe points, ensuring zero
overhead during normal execution while providing a reliable way for
external processes to coordinate debugging operations.

See **PEP 768** for more details.

(Contributed by Pablo Galindo Salgado, Matt Wozniski, and Ivona
Stojanovic in gh-131591.)


Remote attaching to a running Python process with PDB
-----------------------------------------------------

The "pdb" module now supports remote attaching to a running Python
process using a new "-p PID" command-line option:

   python -m pdb -p 1234

This will connect to the Python process with the given PID and allow
you to debug it interactively. Notice that due to how the Python
interpreter works attaching to a remote process that is blocked in a
system call or waiting for I/O will only work once the next bytecode
instruction is executed or when the process receives a signal.

This feature leverages **PEP 768** and the "sys.remote_exec()"
function to attach to the remote process and send the PDB commands to
it.

(Contributed by Matt Wozniski and Pablo Galindo in gh-131591.)


PEP 758 – Allow except and except* expressions without parentheses
------------------------------------------------------------------

The "except" and "except*" expressions now allow parentheses to be
omitted when there are multiple exception types and the "as" clause is
not used. For example the following expressions are now valid:

   try:
       release_new_sleep_token_album()
   except AlbumNotFound, SongsTooGoodToBeReleased:
       print("Sorry, no new album this year.")

    # The same applies to except* (for exception groups):
   try:
       release_new_sleep_token_album()
   except* AlbumNotFound, SongsTooGoodToBeReleased:
       print("Sorry, no new album this year.")

Check **PEP 758** for more details.

(Contributed by Pablo Galindo and Brett Cannon in gh-131831.)


PEP 649: deferred evaluation of annotations
-------------------------------------------

The *annotations* on functions, classes, and modules are no longer
evaluated eagerly. Instead, annotations are stored in special-purpose
*annotate functions* and evaluated only when necessary. This is
specified in **PEP 649** and **PEP 749**.

This change is designed to make annotations in Python more performant
and more usable in most circumstances. The runtime cost for defining
annotations is minimized, but it remains possible to introspect
annotations at runtime. It is usually no longer necessary to enclose
annotations in strings if they contain forward references.

The new "annotationlib" module provides tools for inspecting deferred
annotations. Annotations may be evaluated in the "VALUE" format (which
evaluates annotations to runtime values, similar to the behavior in
earlier Python versions), the "FORWARDREF" format (which replaces
undefined names with special markers), and the "STRING" format (which
returns annotations as strings).

This example shows how these formats behave:

   >>> from annotationlib import get_annotations, Format
   >>> def func(arg: Undefined):
   ...     pass
   >>> get_annotations(func, format=Format.VALUE)
   Traceback (most recent call last):
     ...
   NameError: name 'Undefined' is not defined
   >>> get_annotations(func, format=Format.FORWARDREF)
   {'arg': ForwardRef('Undefined', owner=<function func at 0x...>)}
   >>> get_annotations(func, format=Format.STRING)
   {'arg': 'Undefined'}


Implications for annotated code
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

If you define annotations in your code (for example, for use with a
static type checker), then this change probably does not affect you:
you can keep writing annotations the same way you did with previous
versions of Python.

You will likely be able to remove quoted strings in annotations, which
are frequently used for forward references. Similarly, if you use
"from __future__ import annotations" to avoid having to write strings
in annotations, you may well be able to remove that import. However,
if you rely on third-party libraries that read annotations, those
libraries may need changes to support unquoted annotations before they
work as expected.


Implications for readers of "__annotations__"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

If your code reads the "__annotations__" attribute on objects, you may
want to make changes in order to support code that relies on deferred
evaluation of annotations. For example, you may want to use
"annotationlib.get_annotations()" with the "FORWARDREF" format, as the
"dataclasses" module now does.


Related changes
~~~~~~~~~~~~~~~

The changes in Python 3.14 are designed to rework how
"__annotations__" works at runtime while minimizing breakage to code
that contains annotations in source code and to code that reads
"__annotations__". However, if you rely on undocumented details of the
annotation behavior or on private functions in the standard library,
there are many ways in which your code may not work in Python 3.14. To
safeguard your code against future changes, use only the documented
functionality of the "annotationlib" module.


"from __future__ import annotations"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In Python 3.7, **PEP 563** introduced the "from __future__ import
annotations" directive, which turns all annotations into strings. This
directive is now considered deprecated and it is expected to be
removed in a future version of Python. However, this removal will not
happen until after Python 3.13, the last version of Python without
deferred evaluation of annotations, reaches its end of life in 2029.
In Python 3.14, the behavior of code using "from __future__ import
annotations" is unchanged.


Improved error messages
-----------------------

* The interpreter now provides helpful suggestions when it detects
  typos in Python keywords. When a word that closely resembles a
  Python keyword is encountered, the interpreter will suggest the
  correct keyword in the error message. This feature helps programmers
  quickly identify and fix common typing mistakes. For example:

     >>> whille True:
     ...     pass
     Traceback (most recent call last):
       File "<stdin>", line 1
         whille True:
         ^^^^^^
     SyntaxError: invalid syntax. Did you mean 'while'?

     >>> asynch def fetch_data():
     ...     pass
     Traceback (most recent call last):
       File "<stdin>", line 1
         asynch def fetch_data():
         ^^^^^^
     SyntaxError: invalid syntax. Did you mean 'async'?

     >>> async def foo():
     ...     awaid fetch_data()
     Traceback (most recent call last):
       File "<stdin>", line 2
         awaid fetch_data()
         ^^^^^
     SyntaxError: invalid syntax. Did you mean 'await'?

     >>> raisee ValueError("Error")
     Traceback (most recent call last):
       File "<stdin>", line 1
         raisee ValueError("Error")
         ^^^^^^
     SyntaxError: invalid syntax. Did you mean 'raise'?

  While the feature focuses on the most common cases, some variations
  of misspellings may still result in regular syntax errors.
  (Contributed by Pablo Galindo in gh-132449.)

* When unpacking assignment fails due to incorrect number of
  variables, the error message prints the received number of values in
  more cases than before. (Contributed by Tushar Sadhwani in
  gh-122239.)

     >>> x, y, z = 1, 2, 3, 4
     Traceback (most recent call last):
       File "<stdin>", line 1, in <module>
         x, y, z = 1, 2, 3, 4
         ^^^^^^^
     ValueError: too many values to unpack (expected 3, got 4)

* "elif" statements that follow an "else" block now have a specific
  error message. (Contributed by Steele Farnsworth in gh-129902.)

     >>> if who == "me":
     ...     print("It's me!")
     ... else:
     ...     print("It's not me!")
     ... elif who is None:
     ...     print("Who is it?")
     File "<stdin>", line 5
       elif who is None:
       ^^^^
     SyntaxError: 'elif' block follows an 'else' block

* If a statement ("pass", "del", "return", "yield", "raise", "break",
  "continue", "assert", "import", "from") is passed to the Conditional
  expressions after "else", or one of "pass", "break", or "continue"
  is passed before "if", then the error message highlights where the
  "expression" is required. (Contributed by Sergey Miryanov in
  gh-129515.)

     >>> x = 1 if True else pass
     Traceback (most recent call last):
       File "<string>", line 1
         x = 1 if True else pass
                            ^^^^
     SyntaxError: expected expression after 'else', but statement is given

     >>> x = continue if True else break
     Traceback (most recent call last):
       File "<string>", line 1
         x = continue if True else break
             ^^^^^^^^
     SyntaxError: expected expression before 'if', but statement is given

* When incorrectly closed strings are detected, the error message
  suggests that the string may be intended to be part of the string.
  (Contributed by Pablo Galindo in gh-88535.)

     >>> "The interesting object "The important object" is very important"
     Traceback (most recent call last):
     SyntaxError: invalid syntax. Is this intended to be part of the string?


PEP 741: Python Configuration C API
-----------------------------------

Add a PyInitConfig C API to configure the Python initialization
without relying on C structures and the ability to make ABI-compatible
changes in the future.

Complete the **PEP 587** PyConfig C API by adding
"PyInitConfig_AddModule()" which can be used to add a built-in
extension module; feature previously referred to as the “inittab”.

Add "PyConfig_Get()" and "PyConfig_Set()" functions to get and set the
current runtime configuration.

PEP 587 “Python Initialization Configuration” unified all the ways to
configure the Python initialization. This PEP unifies also the
configuration of the Python preinitialization and the Python
initialization in a single API. Moreover, this PEP only provides a
single choice to embed Python, instead of having two “Python” and
“Isolated” choices (PEP 587), to simplify the API further.

The lower level PEP 587 PyConfig API remains available for use cases
with an intentionally higher level of coupling to CPython
implementation details (such as emulating the full functionality of
CPython’s CLI, including its configuration mechanisms).

(Contributed by Victor Stinner in gh-107954.)

See also: **PEP 741**.


A new type of interpreter
-------------------------

A new type of interpreter has been added to CPython. It uses tail
calls between small C functions that implement individual Python
opcodes, rather than one large C case statement. For certain newer
compilers, this interpreter provides significantly better performance.
Preliminary numbers on our machines suggest anywhere up to 30% faster
Python code, and a geometric mean of 3-5% faster on "pyperformance"
depending on platform and architecture. The baseline is Python 3.14
built with Clang 19 without this new interpreter.

This interpreter currently only works with Clang 19 and newer on
x86-64 and AArch64 architectures. However, we expect that a future
release of GCC will support this as well.

This feature is opt-in for now. We highly recommend enabling profile-
guided optimization with the new interpreter as it is the only
configuration we have tested and can validate its improved
performance. For further information on how to build Python, see "--
with-tail-call-interp".

Note:

  This is not to be confused with tail call optimization of Python
  functions, which is currently not implemented in CPython.This new
  interpreter type is an internal implementation detail of the CPython
  interpreter.  It doesn't change the visible behavior of Python
  programs at all.  It can improve their performance, but doesn't
  change anything else.

Attention:

  This section previously reported a 9-15% geometric mean speedup.
  This number has since been cautiously revised down to 3-5%. While we
  expect performance results to be better than what we report, our
  estimates are more conservative due to a compiler bug found in
  Clang/LLVM 19, which causes the normal interpreter to be slower. We
  were unaware of this bug, resulting in inaccurate results. We
  sincerely apologize for communicating results that were only
  accurate for LLVM v19.1.x and v20.1.0. In the meantime, the bug has
  been fixed in LLVM v20.1.1 and for the upcoming v21.1, but it will
  remain unfixed for LLVM v19.1.x and v20.1.0. Thus any benchmarks
  with those versions of LLVM may produce inaccurate numbers. (Thanks
  to Nelson Elhage for bringing this to light.)

(Contributed by Ken Jin in gh-128563, with ideas on how to implement
this in CPython by Mark Shannon, Garrett Gu, Haoran Xu, and Josh
Haberman.)


Other language changes
======================

* The "map()" built-in now has an optional keyword-only *strict* flag
  like "zip()" to check that all the iterables are of equal length.
  (Contributed by Wannes Boeykens in gh-119793.)

* Incorrect usage of "await" and asynchronous comprehensions is now
  detected even if the code is optimized away by the "-O" command-line
  option. For example, "python -O -c 'assert await 1'" now produces a
  "SyntaxError". (Contributed by Jelle Zijlstra in gh-121637.)

* Writes to "__debug__" are now detected even if the code is optimized
  away by the "-O" command-line option. For example, "python -O -c
  'assert (__debug__ := 1)'" now produces a "SyntaxError".
  (Contributed by Irit Katriel in gh-122245.)

* Add class methods "float.from_number()" and "complex.from_number()"
  to convert a number to "float" or "complex" type correspondingly.
  They raise an error if the argument is a string. (Contributed by
  Serhiy Storchaka in gh-84978.)

* Implement mixed-mode arithmetic rules combining real and complex
  numbers as specified by C standards since C99. (Contributed by
  Sergey B Kirpichev in gh-69639.)

* All Windows code pages are now supported as "cpXXX" codecs on
  Windows. (Contributed by Serhiy Storchaka in gh-123803.)

* "super" objects are now "pickleable" and "copyable". (Contributed by
  Serhiy Storchaka in gh-125767.)

* The "memoryview" type now supports subscription, making it a
  *generic type*. (Contributed by Brian Schubert in gh-126012.)

* Support underscore and comma as thousands separators in the
  fractional part for floating-point presentation types of the new-
  style string formatting (with "format()" or f-strings). (Contributed
  by Sergey B Kirpichev in gh-87790.)

* The "bytes.fromhex()" and "bytearray.fromhex()" methods now accept
  ASCII "bytes" and *bytes-like objects*. (Contributed by Daniel Pope
  in gh-129349.)

* "\B" in "regular expression" now matches empty input string. Now it
  is always the opposite of "\b". (Contributed by Serhiy Storchaka in
  gh-124130.)

* iOS and macOS apps can now be configured to redirect "stdout" and
  "stderr" content to the system log. (Contributed by Russell Keith-
  Magee in gh-127592.)

* The iOS testbed is now able to stream test output while the test is
  running. The testbed can also be used to run the test suite of
  projects other than CPython itself. (Contributed by Russell Keith-
  Magee in gh-127592.)

* Three-argument "pow()" now try calling "__rpow__()" if necessary.
  Previously it was only called in two-argument "pow()" and the binary
  power operator. (Contributed by Serhiy Storchaka in gh-130104.)

* Add a built-in implementation for HMAC (**RFC 2104**) using formally
  verified code from the HACL* project. This implementation is used as
  a fallback when the OpenSSL implementation of HMAC is not available.
  (Contributed by Bénédikt Tran in gh-99108.)

* When subclassing from a pure C type, the C slots for the new type
  are no longer replaced with a wrapped version on class creation if
  they are not explicitly overridden in the subclass. (Contributed by
  Tomasz Pytel in gh-132329.)

* The command line option "-c" now automatically dedents its code
  argument before execution. The auto-dedentation behavior mirrors
  "textwrap.dedent()". (Contributed by Jon Crall and Steven Sun in
  gh-103998.)

* Improve error message when an object supporting the synchronous
  (resp. asynchronous) context manager protocol is entered using
  "async with" (resp. "with") instead of "with" (resp. "async with").
  (Contributed by Bénédikt Tran in gh-128398.)


PEP 765: Disallow return/break/continue that exit a finally block
-----------------------------------------------------------------

The compiler emits a "SyntaxWarning" when a "return", "break" or
"continue" statements appears where it exits a "finally" block. This
change is specified in **PEP 765**.


New modules
===========

* "annotationlib": For introspecting *annotations*. See **PEP 749**
  for more details. (Contributed by Jelle Zijlstra in gh-119180.)


Improved modules
================


argparse
--------

* The default value of the program name for "argparse.ArgumentParser"
  now reflects the way the Python interpreter was instructed to find
  the "__main__" module code. (Contributed by Serhiy Storchaka and
  Alyssa Coghlan in gh-66436.)

* Introduced the optional *suggest_on_error* parameter to
  "argparse.ArgumentParser", enabling suggestions for argument choices
  and subparser names if mistyped by the user. (Contributed by
  Savannah Ostrowski in gh-124456.)


ast
---

* Add "ast.compare()" for comparing two ASTs. (Contributed by Batuhan
  Taskaya and Jeremy Hylton in gh-60191.)

* Add support for "copy.replace()" for AST nodes. (Contributed by
  Bénédikt Tran in gh-121141.)

* Docstrings are now removed from an optimized AST in optimization
  level 2. (Contributed by Irit Katriel in gh-123958.)

* The "repr()" output for AST nodes now includes more information.
  (Contributed by Tomas R in gh-116022.)

* "ast.parse()", when called with an AST as input, now always verifies
  that the root node type is appropriate. (Contributed by Irit Katriel
  in gh-130139.)


bdb
---

* The "bdb" module now supports the "sys.monitoring" backend.
  (Contributed by Tian Gao in gh-124533.)


calendar
--------

* By default, today's date is highlighted in color in "calendar"'s
  command-line text output. This can be controlled via the
  "PYTHON_COLORS" environment variable as well as the canonical
  "NO_COLOR" and "FORCE_COLOR" environment variables. See also
  Controlling color. (Contributed by Hugo van Kemenade in gh-128317.)


concurrent.futures
------------------

* Add "InterpreterPoolExecutor", which exposes "subinterpreters
  (multiple Python interpreters in the same process) to Python code.
  This is separate from the proposed API in **PEP 734**. (Contributed
  by Eric Snow in gh-124548.)

* The default "ProcessPoolExecutor" start method changed from fork to
  forkserver on platforms other than macOS and Windows where it was
  already spawn.

  If the threading incompatible *fork* method is required, you must
  explicitly request it by supplying a multiprocessing context
  *mp_context* to "ProcessPoolExecutor".

  See forkserver restrictions for information and differences with the
  *fork* method and how this change may affect existing code with
  mutable global shared variables and/or shared objects that can not
  be automatically "pickled".

  (Contributed by Gregory P. Smith in gh-84559.)

* Add "concurrent.futures.ProcessPoolExecutor.terminate_workers()" and
  "concurrent.futures.ProcessPoolExecutor.kill_workers()" as ways to
  terminate or kill all living worker processes in the given pool.
  (Contributed by Charles Machalow in gh-130849.)

* Add the optional "buffersize" parameter to
  "concurrent.futures.Executor.map()" to limit the number of submitted
  tasks whose results have not yet been yielded. If the buffer is
  full, iteration over the *iterables* pauses until a result is
  yielded from the buffer. (Contributed by Enzo Bonnal and Josh
  Rosenberg in gh-74028.)


contextvars
-----------

* Support context manager protocol by "contextvars.Token".
  (Contributed by Andrew Svetlov in gh-129889.)


ctypes
------

* The layout of bit fields in "Structure" and "Union" now matches
  platform defaults (GCC/Clang or MSVC) more closely. In particular,
  fields no longer overlap. (Contributed by Matthias Görgens in
  gh-97702.)

* The "Structure._layout_" class attribute can now be set to help
  match a non-default ABI. (Contributed by Petr Viktorin in gh-97702.)

* The class of "Structure"/"Union" field descriptors is now available
  as "CField", and has new attributes to aid debugging and
  introspection. (Contributed by Petr Viktorin in gh-128715.)

* On Windows, the "COMError" exception is now public. (Contributed by
  Jun Komoda in gh-126686.)

* On Windows, the "CopyComPointer()" function is now public.
  (Contributed by Jun Komoda in gh-127275.)

* "ctypes.memoryview_at()" now exists to create a "memoryview" object
  that refers to the supplied pointer and length. This works like
  "ctypes.string_at()" except it avoids a buffer copy, and is
  typically useful when implementing pure Python callback functions
  that are passed dynamically-sized buffers. (Contributed by Rian
  Hunter in gh-112018.)

* Complex types, "c_float_complex", "c_double_complex" and
  "c_longdouble_complex", are now available if both the compiler and
  the "libffi" library support complex C types. (Contributed by Sergey
  B Kirpichev in gh-61103).

* Add "ctypes.util.dllist()" for listing the shared libraries loaded
  by the current process. (Contributed by Brian Ward in gh-119349.)

* The "ctypes.py_object" type now supports subscription, making it a
  *generic type*. (Contributed by Brian Schubert in gh-132168.)


datetime
--------

* Add "datetime.time.strptime()" and "datetime.date.strptime()".
  (Contributed by Wannes Boeykens in gh-41431.)


decimal
-------

* Add alternative "Decimal" constructor "Decimal.from_number()".
  (Contributed by Serhiy Storchaka in gh-121798.)


difflib
-------

* Comparison pages with highlighted changes generated by the
  "difflib.HtmlDiff" class now support dark mode. (Contributed by
  Jiahao Li in gh-129939.)


dis
---

* Add support for rendering full source location information of
  "instructions", rather than only the line number. This feature is
  added to the following interfaces via the *show_positions* keyword
  argument:

  * "dis.Bytecode"

  * "dis.dis()"

  * "dis.distb()"

  * "dis.disassemble()"

  This feature is also exposed via "dis --show-positions".
  (Contributed by Bénédikt Tran in gh-123165.)

* Add the "dis --specialized" command-line option to show specialized
  bytecode. (Contributed by Bénédikt Tran in gh-127413.)


errno
-----

* Add "errno.EHWPOISON" error code. (Contributed by James Roy in
  gh-126585.)


faulthandler
------------

* Add support for printing the C stack trace on systems that support
  it via "faulthandler.dump_c_stack()" or via the *c_stack* argument
  in "faulthandler.enable()". (Contributed by Peter Bierma in
  gh-127604.)


fnmatch
-------

* Added "fnmatch.filterfalse()" for excluding names matching a
  pattern. (Contributed by Bénédikt Tran in gh-74598.)


fractions
---------

* Add support for converting any objects that have the
  "as_integer_ratio()" method to a "Fraction". (Contributed by Serhiy
  Storchaka in gh-82017.)

* Add alternative "Fraction" constructor "Fraction.from_number()".
  (Contributed by Serhiy Storchaka in gh-121797.)


functools
---------

* Add support to "functools.partial()" and "functools.partialmethod()"
  for "functools.Placeholder" sentinels to reserve a place for
  positional arguments. (Contributed by Dominykas Grigonis in
  gh-119127.)

* Allow the *initial* parameter of "functools.reduce()" to be passed
  as a keyword argument. (Contributed by Sayandip Dutta in gh-125916.)


getopt
------

* Add support for options with optional arguments. (Contributed by
  Serhiy Storchaka in gh-126374.)

* Add support for returning intermixed options and non-option
  arguments in order. (Contributed by Serhiy Storchaka in gh-126390.)


graphlib
--------

* Allow "graphlib.TopologicalSorter.prepare()" to be called more than
  once as long as sorting has not started. (Contributed by Daniel Pope
  in gh-130914)


hmac
----

* Add a built-in implementation for HMAC (**RFC 2104**) using formally
  verified code from the HACL* project. (Contributed by Bénédikt Tran
  in gh-99108.)


http
----

* Directory lists and error pages generated by the "http.server"
  module allow the browser to apply its default dark mode.
  (Contributed by Yorik Hansen in gh-123430.)

* The "http.server" module now supports serving over HTTPS using the
  "http.server.HTTPSServer" class. This functionality is exposed by
  the command-line interface ("python -m http.server") through the
  following options:

  * "--tls-cert <path>": Path to the TLS certificate file.

  * "--tls-key <path>": Optional path to the private key file.

  * "--tls-password-file <path>": Optional path to the password file
    for the private key.

  (Contributed by Semyon Moroz in gh-85162.)


imaplib
-------

* Add "IMAP4.idle()", implementing the IMAP4 "IDLE" command as defined
  in **RFC 2177**. (Contributed by Forest in gh-55454.)


inspect
-------

* "inspect.signature()" takes a new argument *annotation_format* to
  control the "annotationlib.Format" used for representing
  annotations. (Contributed by Jelle Zijlstra in gh-101552.)

* "inspect.Signature.format()" takes a new argument
  *unquote_annotations*. If true, string *annotations* are displayed
  without surrounding quotes. (Contributed by Jelle Zijlstra in
  gh-101552.)

* Add function "inspect.ispackage()" to determine whether an object is
  a *package* or not. (Contributed by Zhikang Yan in gh-125634.)


io
--

* Reading text from a non-blocking stream with "read" may now raise a
  "BlockingIOError" if the operation cannot immediately return bytes.
  (Contributed by Giovanni Siragusa in gh-109523.)

* Add protocols "io.Reader" and "io.Writer" as a simpler alternatives
  to the pseudo-protocols "typing.IO", "typing.TextIO", and
  "typing.BinaryIO". (Contributed by Sebastian Rittau in gh-127648.)


json
----

* Add notes for JSON serialization errors that allow to identify the
  source of the error. (Contributed by Serhiy Storchaka in gh-122163.)

* Enable the "json" module to work as a script using the "-m" switch:
  **python -m json**. See the JSON command-line interface
  documentation. (Contributed by Trey Hunner in gh-122873.)

* By default, the output of the JSON command-line interface is
  highlighted in color. This can be controlled via the "PYTHON_COLORS"
  environment variable as well as the canonical "NO_COLOR" and
  "FORCE_COLOR" environment variables. See also Controlling color.
  (Contributed by Tomas Roun in gh-131952.)


linecache
---------

* "linecache.getline()" can retrieve source code for frozen modules.
  (Contributed by Tian Gao in gh-131638.)


logging.handlers
----------------

* "logging.handlers.QueueListener" now implements the context manager
  protocol, allowing it to be used in a "with" statement. (Contributed
  by Charles Machalow in gh-132106.)

* "QueueListener.start" now raises a "RuntimeError" if the listener is
  already started. (Contributed by Charles Machalow in gh-132106.)


math
----

* Added more detailed error messages for domain errors in the module.
  (Contributed by by Charlie Zhao and Sergey B Kirpichev in
  gh-101410.)


mimetypes
---------

* Document the command-line for "mimetypes". It now exits with "1" on
  failure instead of "0" and "2" on incorrect command-line parameters
  instead of "1". Also, errors are printed to stderr instead of stdout
  and their text is made tighter. (Contributed by Oleg Iarygin and
  Hugo van Kemenade in gh-93096.)

* Add MS and **RFC 8081** MIME types for fonts:

  * Embedded OpenType: "application/vnd.ms-fontobject"

  * OpenType Layout (OTF) "font/otf"

  * TrueType: "font/ttf"

  * WOFF 1.0 "font/woff"

  * WOFF 2.0 "font/woff2"

  (Contributed by Sahil Prajapati and Hugo van Kemenade in gh-84852.)

* Add **RFC 9559** MIME types for Matroska audiovisual data container
  structures, containing:

  * audio with no video: "audio/matroska" (".mka")

  * video: "video/matroska" (".mkv")

  * stereoscopic video: "video/matroska-3d" (".mk3d")

  (Contributed by Hugo van Kemenade in gh-89416.)

* Add MIME types for images with RFCs:

  * **RFC 1494**: CCITT Group 3 (".g3")

  * **RFC 3362**: Real-time Facsimile, T.38 (".t38")

  * **RFC 3745**: JPEG 2000 (".jp2"), extension (".jpx") and compound
    (".jpm")

  * **RFC 3950**: Tag Image File Format Fax eXtended, TIFF-FX (".tfx")

  * **RFC 4047**: Flexible Image Transport System (".fits")

  * **RFC 7903**: Enhanced Metafile (".emf") and Windows Metafile
    (".wmf")

  (Contributed by Hugo van Kemenade in gh-85957.)

* More MIME type changes:

  * **RFC 2361**: Change type for ".avi" to "video/vnd.avi" and for
    ".wav" to "audio/vnd.wave"

  * **RFC 4337**: Add MPEG-4 "audio/mp4" (".m4a"))

  * **RFC 5334**: Add Ogg media (".oga", ".ogg" and ".ogx")

  * **RFC 9639**: Add FLAC "audio/flac" (".flac")

  * De facto: Add WebM "audio/webm" (".weba")

  * ECMA-376: Add ".docx", ".pptx" and ".xlsx" types

  * OASIS: Add OpenDocument ".odg", ".odp", ".ods" and ".odt" types

  * W3C: Add EPUB "application/epub+zip" (".epub")

  (Contributed by Hugo van Kemenade in gh-129965.)

* Add **RFC 9512** "application/yaml" MIME type for YAML files
  (".yaml" and ".yml"). (Contributed by Sasha "Nelie" Chernykh and
  Hugo van Kemenade in gh-132056.)


multiprocessing
---------------

* The default start method changed from fork to forkserver on
  platforms other than macOS and Windows where it was already spawn.

  If the threading incompatible *fork* method is required, you must
  explicitly request it via a context from
  "multiprocessing.get_context()" (preferred) or change the default
  via "multiprocessing.set_start_method()".

  See forkserver restrictions for information and differences with the
  *fork* method and how this change may affect existing code with
  mutable global shared variables and/or shared objects that can not
  be automatically "pickled".

  (Contributed by Gregory P. Smith in gh-84559.)

* "multiprocessing"'s ""forkserver"" start method now authenticates
  its control socket to avoid solely relying on filesystem permissions
  to restrict what other processes could cause the forkserver to spawn
  workers and run code. (Contributed by Gregory P. Smith for
  gh-97514.)

* The multiprocessing proxy objects for *list* and *dict* types gain
  previously overlooked missing methods:

     * "clear()" and "copy()" for proxies of "list".

     * "fromkeys()", "reversed(d)", "d | {}", "{} | d", "d |= {'b':
       2}" for proxies of "dict".

  (Contributed by Roy Hyunjin Han for gh-103134.)

* Add support for shared "set" objects via "SyncManager.set()". The
  "set()" in "multiprocessing.Manager()" method is now available.
  (Contributed by Mingyu Park in gh-129949.)

* Add "multiprocessing.Process.interrupt()" which terminates the child
  process by sending "SIGINT". This enables "finally" clauses and
  printing stack trace for the terminated process. (Contributed by
  Artem Pulkin in gh-131913.)


operator
--------

* Two new functions "operator.is_none()" and "operator.is_not_none()"
  have been added, such that "operator.is_none(obj)" is equivalent to
  "obj is None" and "operator.is_not_none(obj)" is equivalent to "obj
  is not None". (Contributed by Raymond Hettinger and Nico Mexis in
  gh-115808.)


os
--

* Add the "os.reload_environ()" function to update "os.environ" and
  "os.environb" with changes to the environment made by "os.putenv()",
  by "os.unsetenv()", or made outside Python in the same process.
  (Contributed by Victor Stinner in gh-120057.)

* Add the "SCHED_DEADLINE" and "SCHED_NORMAL" constants to the "os"
  module. (Contributed by James Roy in gh-127688.)

* Add the "os.readinto()" function to read into a buffer object from a
  file descriptor. (Contributed by Cody Maloney in gh-129205.)


pathlib
-------

* Add methods to "pathlib.Path" to recursively copy or move files and
  directories:

  * "copy()" copies a file or directory tree to a destination.

  * "copy_into()" copies *into* a destination directory.

  * "move()" moves a file or directory tree to a destination.

  * "move_into()" moves *into* a destination directory.

  (Contributed by Barney Gale in gh-73991.)

* Add "pathlib.Path.info" attribute, which stores an object
  implementing the "pathlib.types.PathInfo" protocol (also new). The
  object supports querying the file type and internally caching
  "stat()" results. Path objects generated by "iterdir()" are
  initialized with file type information gleaned from scanning the
  parent directory. (Contributed by Barney Gale in gh-125413.)


pdb
---

* Hardcoded breakpoints ("breakpoint()" and "pdb.set_trace()") now
  reuse the most recent "Pdb" instance that calls "set_trace()",
  instead of creating a new one each time. As a result, all the
  instance specific data like "display" and "commands" are preserved
  across hardcoded breakpoints. (Contributed by Tian Gao in
  gh-121450.)

* Add a new argument *mode* to "pdb.Pdb". Disable the "restart"
  command when "pdb" is in "inline" mode. (Contributed by Tian Gao in
  gh-123757.)

* A confirmation prompt will be shown when the user tries to quit
  "pdb" in "inline" mode. "y", "Y", "<Enter>" or "EOF" will confirm
  the quit and call "sys.exit()", instead of raising "bdb.BdbQuit".
  (Contributed by Tian Gao in gh-124704.)

* Inline breakpoints like "breakpoint()" or "pdb.set_trace()" will
  always stop the program at calling frame, ignoring the "skip"
  pattern (if any). (Contributed by Tian Gao in gh-130493.)

* "<tab>" at the beginning of the line in "pdb" multi-line input will
  fill in a 4-space indentation now, instead of inserting a "\t"
  character. (Contributed by Tian Gao in gh-130471.)

* "$_asynctask" is added to access the current asyncio task if
  applicable. (Contributed by Tian Gao in gh-124367.)

* "pdb" now supports two backends: "sys.settrace()" and
  "sys.monitoring". Using "pdb" CLI or "breakpoint()" will always use
  the "sys.monitoring" backend. Explicitly instantiating "pdb.Pdb" and
  its derived classes will use the "sys.settrace()" backend by
  default, which is configurable. (Contributed by Tian Gao in
  gh-124533.)


pickle
------

* Set the default protocol version on the "pickle" module to 5. For
  more details, see pickle protocols.

* Add notes for pickle serialization errors that allow to identify the
  source of the error. (Contributed by Serhiy Storchaka in gh-122213.)


platform
--------

* Add "platform.invalidate_caches()" to invalidate the cached results.
  (Contributed by Bénédikt Tran in gh-122549.)


pydoc
-----

* *Annotations* in help output are now usually displayed in a format
  closer to that in the original source. (Contributed by Jelle
  Zijlstra in gh-101552.)


socket
------

* Improve and fix support for Bluetooth sockets.

  * Fix support of Bluetooth sockets on NetBSD and DragonFly BSD.
    (Contributed by Serhiy Storchaka in gh-132429.)

  * Fix support for "BTPROTO_HCI" on FreeBSD. (Contributed by Victor
    Stinner in gh-111178.)

  * Add support for "BTPROTO_SCO" on FreeBSD. (Contributed by Serhiy
    Storchaka in gh-85302.)

  * Add support for *cid* and *bdaddr_type* in the address for
    "BTPROTO_L2CAP" on FreeBSD. (Contributed by Serhiy Storchaka in
    gh-132429.)

  * Add support for *channel* in the address for "BTPROTO_HCI" on
    Linux. (Contributed by Serhiy Storchaka in gh-70145.)

  * Accept an integer as the address for "BTPROTO_HCI" on Linux
    (Contributed by Serhiy Storchaka in gh-132099.)

  * Return *cid* in "getsockname()" for "BTPROTO_L2CAP". (Contributed
    by Serhiy Storchaka in gh-132429.)

  * Add many new constants. (Contributed by Serhiy Storchaka in
    gh-132734.)


ssl
---

* Indicate through "ssl.HAS_PHA" whether the "ssl" module supports
  TLSv1.3 post-handshake client authentication (PHA). (Contributed by
  Will Childs-Klein in gh-128036.)


struct
------

* Support the float complex and double complex C types in the "struct"
  module (formatting characters "'F'" and "'D'", respectively) if the
  compiler has C11 complex arithmetic. (Contributed by Sergey B
  Kirpichev in gh-121249.)


symtable
--------

* Expose the following "symtable.Symbol" methods:

  * "is_comp_cell()"

  * "is_comp_iter()"

  * "is_free_class()"

  (Contributed by Bénédikt Tran in gh-120029.)


sys
---

* The previously undocumented special function "sys.getobjects()",
  which only exists in specialized builds of Python, may now return
  objects from other interpreters than the one it's called in.

* Add "sys._is_immortal()" for determining if an object is *immortal*.
  (Contributed by Peter Bierma in gh-128509.)

* On FreeBSD, "sys.platform" doesn't contain the major version
  anymore. It is always "'freebsd'", instead of "'freebsd13'" or
  "'freebsd14'".

* Raise "DeprecationWarning" for "sys._clear_type_cache()". This
  function was deprecated in Python 3.13 but it didn't raise a runtime
  warning.


sys.monitoring
--------------

* Two new events are added: "BRANCH_LEFT" and "BRANCH_RIGHT". The
  "BRANCH" event is deprecated.


sysconfig
---------

* Add "ABIFLAGS" key to "sysconfig.get_config_vars()" on Windows.
  (Contributed by Xuehai Pan in gh-131799.)


threading
---------

* "threading.Thread.start()" now sets the operating system thread name
  to "threading.Thread.name". (Contributed by Victor Stinner in
  gh-59705.)


tkinter
-------

* Make tkinter widget methods "after()" and "after_idle()" accept
  arguments passed by keyword. (Contributed by Zhikang Yan in
  gh-126899.)


turtle
------

* Add context managers for "turtle.fill()", "turtle.poly()" and
  "turtle.no_animation()". (Contributed by Marie Roald and Yngve
  Mardal Moe in gh-126350.)


types
-----

* "types.UnionType" is now an alias for "typing.Union". See below for
  more details. (Contributed by Jelle Zijlstra in gh-105499.)


typing
------

* "types.UnionType" and "typing.Union" are now aliases for each other,
  meaning that both old-style unions (created with "Union[int, str]")
  and new-style unions ("int | str") now create instances of the same
  runtime type. This unifies the behavior between the two syntaxes,
  but leads to some differences in behavior that may affect users who
  introspect types at runtime:

  * Both syntaxes for creating a union now produce the same string
    representation in "repr()". For example, "repr(Union[int, str])"
    is now ""int | str"" instead of ""typing.Union[int, str]"".

  * Unions created using the old syntax are no longer cached.
    Previously, running "Union[int, str]" multiple times would return
    the same object ("Union[int, str] is Union[int, str]" would be
    "True"), but now it will return two different objects. Users
    should use "==" to compare unions for equality, not "is". New-
    style unions have never been cached this way. This change could
    increase memory usage for some programs that use a large number of
    unions created by subscripting "typing.Union". However, several
    factors offset this cost: unions used in annotations are no longer
    evaluated by default in Python 3.14 because of **PEP 649**; an
    instance of "types.UnionType" is itself much smaller than the
    object returned by "Union[]" was on prior Python versions; and
    removing the cache also saves some space. It is therefore unlikely
    that this change will cause a significant increase in memory usage
    for most users.

  * Previously, old-style unions were implemented using the private
    class "typing._UnionGenericAlias". This class is no longer needed
    for the implementation, but it has been retained for backward
    compatibility, with removal scheduled for Python 3.17. Users
    should use documented introspection helpers like
    "typing.get_origin()" and "typing.get_args()" instead of relying
    on private implementation details.

  * It is now possible to use "typing.Union" itself in "isinstance()"
    checks. For example, "isinstance(int | str, typing.Union)" will
    return "True"; previously this raised "TypeError".

  * The "__args__" attribute of "typing.Union" objects is no longer
    writable.

  * It is no longer possible to set any attributes on "typing.Union"
    objects. This only ever worked for dunder attributes on previous
    versions, was never documented to work, and was subtly broken in
    many cases.

  (Contributed by Jelle Zijlstra in gh-105499.)


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

* The Unicode database has been updated to Unicode 16.0.0.


unittest
--------

* "unittest" output is now colored by default. This can be controlled
  via the "PYTHON_COLORS" environment variable as well as the
  canonical "NO_COLOR" and "FORCE_COLOR" environment variables. See
  also Controlling color. (Contributed by Hugo van Kemenade in
  gh-127221.)

* unittest discovery supports *namespace package* as start directory
  again. It was removed in Python 3.11. (Contributed by Jacob Walls in
  gh-80958.)

* A number of new methods were added in the "TestCase" class that
  provide more specialized tests.

  * "assertHasAttr()" and "assertNotHasAttr()" check whether the
    object has a particular attribute.

  * "assertIsSubclass()" and "assertNotIsSubclass()" check whether the
    object is a subclass of a particular class, or of one of a tuple
    of classes.

  * "assertStartsWith()", "assertNotStartsWith()", "assertEndsWith()"
    and "assertNotEndsWith()" check whether the Unicode or byte string
    starts or ends with particular string(s).

  (Contributed by Serhiy Storchaka in gh-71339.)


urllib
------

* Upgrade HTTP digest authentication algorithm for "urllib.request" by
  supporting SHA-256 digest authentication as specified in **RFC
  7616**. (Contributed by Calvin Bui in gh-128193.)

* Improve ergonomics and standards compliance when parsing and
  emitting "file:" URLs.

  In "urllib.request.url2pathname()":

  * Accept a complete URL when the new *require_scheme* argument is
    set to true.

  * Discard URL authorities that resolve to a local IP address.

  * Raise "URLError" if a URL authority doesn't resolve to a local IP
    address, except on Windows where we return a UNC path.

  In "urllib.request.pathname2url()":

  * Return a complete URL when the new *add_scheme* argument is set to
    true.

  * Include an empty URL authority when a path begins with a slash.
    For example, the path "/etc/hosts" is converted to the URL
    "///etc/hosts".

  On Windows, drive letters are no longer converted to uppercase, and
  ":" characters not following a drive letter no longer cause an
  "OSError" exception to be raised.

  (Contributed by Barney Gale in gh-125866.)


uuid
----

* Add support for UUID versions 6, 7, and 8 via "uuid.uuid6()",
  "uuid.uuid7()", and "uuid.uuid8()" respectively, as specified in
  **RFC 9562**. (Contributed by Bénédikt Tran in gh-89083.)

* "uuid.NIL" and "uuid.MAX" are now available to represent the Nil and
  Max UUID formats as defined by **RFC 9562**. (Contributed by Nick
  Pope in gh-128427.)

* Allow to generate multiple UUIDs at once via "python -m uuid
  --count". (Contributed by Simon Legner in gh-131236.)


webbrowser
----------

* Names in the "BROWSER" environment variable can now refer to already
  registered browsers for the "webbrowser" module, instead of always
  generating a new browser command.

  This makes it possible to set "BROWSER" to the value of one of the
  supported browsers on macOS.


zipinfo
-------

* Added "ZipInfo._for_archive" to resolve suitable defaults for a
  "ZipInfo" object as used by "ZipFile.writestr". (Contributed by
  Bénédikt Tran in gh-123424.)

* "zipfile.ZipFile.writestr()" now respect "SOURCE_DATE_EPOCH" that
  distributions can set centrally and have build tools consume this in
  order to produce reproducible output. (Contributed by Jiahao Li in
  gh-91279.)


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

* The import time for several standard library modules has been
  improved, including "ast", "asyncio", "base64", "cmd", "csv",
  "gettext", "importlib.util", "locale", "mimetypes", "optparse",
  "pickle", "pprint", "pstats", "socket", "subprocess", "threading",
  "tomllib", and "zipfile".

  (Contributed by Adam Turner, Bénédikt Tran, Chris Markiewicz, Eli
  Schwartz, Hugo van Kemenade, Jelle Zijlstra, and others in
  gh-118761.)


asyncio
-------

* "asyncio" now uses double linked list implementation for native
  tasks which speeds up execution by 10% on standard pyperformance
  benchmarks and reduces memory usage. (Contributed by Kumar Aditya in
  gh-107803.)

* "asyncio" has new utility functions for introspecting and printing
  the program's call graph: "asyncio.capture_call_graph()" and
  "asyncio.print_call_graph()". (Contributed by Yury Selivanov, Pablo
  Galindo Salgado, and Łukasz Langa in gh-91048.)


base64
------

* Improve the performance of "base64.b16decode()" by up to ten times,
  and reduce the import time of "base64" by up to six times.
  (Contributed by Bénédikt Tran, Chris Markiewicz, and Adam Turner in
  gh-118761.)


io
--

* "io" which provides the built-in "open()" makes less system calls
  when opening regular files as well as reading whole files. Reading a
  small operating system cached file in full is up to 15% faster.
  "pathlib.Path.read_bytes()" has the most optimizations for reading a
  file's bytes in full. (Contributed by Cody Maloney and Victor
  Stinner in gh-120754 and gh-90102.)


uuid
----

* Improve generation of "UUID" objects via their dedicated functions:

  * "uuid3()" and "uuid5()" are both roughly 40% faster for 16-byte
    names and 20% faster for 1024-byte names. Performance for longer
    names remains unchanged.

  * "uuid4()" and "uuid8()" are 30% and 40% faster respectively.

  (Contributed by Bénédikt Tran in gh-128150.)


zlib
----

* On Windows, "zlib-ng" is now used as the implementation of the
  "zlib" module. This should produce compatible and comparable results
  with better performance, though it is worth noting that
  "zlib.Z_BEST_SPEED" (1) may result in significantly less compression
  than the previous implementation (while also significantly reducing
  the time taken to compress). (Contributed by Steve Dower in
  gh-91349.)


Deprecated
==========

* "argparse":

  * Passing the undocumented keyword argument *prefix_chars* to
    "add_argument_group()" is now deprecated. (Contributed by Savannah
    Ostrowski in gh-125563.)

  * Deprecated the "argparse.FileType" type converter. Anything with
    resource management should be done downstream after the arguments
    are parsed. (Contributed by Serhiy Storchaka in gh-58032.)

* "asyncio":

  * "asyncio.iscoroutinefunction()" is deprecated and will be removed
    in Python 3.16; use "inspect.iscoroutinefunction()" instead.
    (Contributed by Jiahao Li and Kumar Aditya in gh-122875.)

  * "asyncio" policy system is deprecated and will be removed in
    Python 3.16. In particular, the following classes and functions
    are deprecated:

    * "asyncio.AbstractEventLoopPolicy"

    * "asyncio.DefaultEventLoopPolicy"

    * "asyncio.WindowsSelectorEventLoopPolicy"

    * "asyncio.WindowsProactorEventLoopPolicy"

    * "asyncio.get_event_loop_policy()"

    * "asyncio.set_event_loop_policy()"

    * "asyncio.set_event_loop()"

    Users should use "asyncio.run()" or "asyncio.Runner" with
    *loop_factory* to use the desired event loop implementation.

    For example, to use "asyncio.SelectorEventLoop" on Windows:

       import asyncio

       async def main():
           ...

       asyncio.run(main(), loop_factory=asyncio.SelectorEventLoop)

    (Contributed by Kumar Aditya in gh-127949.)

* "builtins": Passing a complex number as the *real* or *imag*
  argument in the "complex()" constructor is now deprecated; it should
  only be passed as a single positional argument. (Contributed by
  Serhiy Storchaka in gh-109218.)

* "functools": Calling the Python implementation of
  "functools.reduce()" with *function* or *sequence* as keyword
  arguments is now deprecated. (Contributed by Kirill Podoprigora in
  gh-121676.)

* "nturl2path": This module is now deprecated. Call
  "urllib.request.url2pathname()" and "pathname2url()" instead.
  (Contributed by Barney Gale in gh-125866.)

* "os": *Soft deprecate* "os.popen()" and "os.spawn*" functions. They
  should no longer be used to write new code.  The "subprocess" module
  is recommended instead. (Contributed by Victor Stinner in
  gh-120743.)

* "pathlib": "pathlib.PurePath.as_uri()" is deprecated and will be
  removed in Python 3.19. Use "pathlib.Path.as_uri()" instead.
  (Contributed by Barney Gale in gh-123599.)

* "pdb": The undocumented "pdb.Pdb.curframe_locals" attribute is now a
  deprecated read-only property. The low overhead dynamic frame locals
  access added in Python 3.13 by PEP 667 means the frame locals cache
  reference previously stored in this attribute is no longer needed.
  Derived debuggers should access "pdb.Pdb.curframe.f_locals" directly
  in Python 3.13 and later versions. (Contributed by Tian Gao in
  gh-124369 and gh-125951.)

* "symtable": Deprecate "symtable.Class.get_methods()" due to the lack
  of interest. (Contributed by Bénédikt Tran in gh-119698.)

* "urllib.parse": Accepting objects with false values (like "0" and
  "[]") except empty strings, byte-like objects and "None" in
  "urllib.parse" functions "parse_qsl()" and "parse_qs()" is now
  deprecated. (Contributed by Serhiy Storchaka in gh-116897.)


Pending removal in Python 3.15
------------------------------

* The import system:

  * Setting "__cached__" on a module while failing to set
    "__spec__.cached" is deprecated. In Python 3.15, "__cached__" will
    cease to be set or take into consideration by the import system or
    standard library. (gh-97879)

  * Setting "__package__" on a module while failing to set
    "__spec__.parent" is deprecated. In Python 3.15, "__package__"
    will cease to be set or take into consideration by the import
    system or standard library. (gh-97879)

* "ctypes":

  * The undocumented "ctypes.SetPointerType()" function has been
    deprecated since Python 3.13.

* "http.server":

  * The obsolete and rarely used "CGIHTTPRequestHandler" has been
    deprecated since Python 3.13. No direct replacement exists.
    *Anything* is better than CGI to interface a web server with a
    request handler.

  * The "--cgi" flag to the **python -m http.server** command-line
    interface has been deprecated since Python 3.13.

* "importlib":

  * "load_module()" method: use "exec_module()" instead.

* "locale":

  * The "getdefaultlocale()" function has been deprecated since Python
    3.11. Its removal was originally planned for Python 3.13
    (gh-90817), but has been postponed to Python 3.15. Use
    "getlocale()", "setlocale()", and "getencoding()" instead.
    (Contributed by Hugo van Kemenade in gh-111187.)

* "pathlib":

  * "PurePath.is_reserved()" has been deprecated since Python 3.13.
    Use "os.path.isreserved()" to detect reserved paths on Windows.

* "platform":

  * "java_ver()" has been deprecated since Python 3.13. This function
    is only useful for Jython support, has a confusing API, and is
    largely untested.

* "sysconfig":

  * The *check_home* argument of "sysconfig.is_python_build()" has
    been deprecated since Python 3.12.

* "threading":

  * "RLock()" will take no arguments in Python 3.15. Passing any
    arguments has been deprecated since Python 3.14, as the  Python
    version does not permit any arguments, but the C version allows
    any number of positional or keyword arguments, ignoring every
    argument.

* "types":

  * "types.CodeType": Accessing "co_lnotab" was deprecated in **PEP
    626** since 3.10 and was planned to be removed in 3.12, but it
    only got a proper "DeprecationWarning" in 3.12. May be removed in
    3.15. (Contributed by Nikita Sobolev in gh-101866.)

* "typing":

  * The undocumented keyword argument syntax for creating "NamedTuple"
    classes (for example, "Point = NamedTuple("Point", x=int, y=int)")
    has been deprecated since Python 3.13. Use the class-based syntax
    or the functional syntax instead.

  * The "typing.no_type_check_decorator()" decorator function has been
    deprecated since Python 3.13. After eight years in the "typing"
    module, it has yet to be supported by any major type checker.

* "wave":

  * The "getmark()", "setmark()", and "getmarkers()" methods of the
    "Wave_read" and "Wave_write" classes have been deprecated since
    Python 3.13.

* "zipimport":

  * "load_module()" has been deprecated since Python 3.10. Use
    "exec_module()" instead. (Contributed by Jiahao Li in gh-125746.)


Pending removal in Python 3.16
------------------------------

* The import system:

  * Setting "__loader__" on a module while failing to set
    "__spec__.loader" is deprecated. In Python 3.16, "__loader__" will
    cease to be set or taken into consideration by the import system
    or the standard library.

* "array":

  * The "'u'" format code ("wchar_t") has been deprecated in
    documentation since Python 3.3 and at runtime since Python 3.13.
    Use the "'w'" format code ("Py_UCS4") for Unicode characters
    instead.

* "asyncio":

  * "asyncio.iscoroutinefunction()" is deprecated and will be removed
    in Python 3.16; use "inspect.iscoroutinefunction()" instead.
    (Contributed by Jiahao Li and Kumar Aditya in gh-122875.)

  * "asyncio" policy system is deprecated and will be removed in
    Python 3.16. In particular, the following classes and functions
    are deprecated:

    * "asyncio.AbstractEventLoopPolicy"

    * "asyncio.DefaultEventLoopPolicy"

    * "asyncio.WindowsSelectorEventLoopPolicy"

    * "asyncio.WindowsProactorEventLoopPolicy"

    * "asyncio.get_event_loop_policy()"

    * "asyncio.set_event_loop_policy()"

    Users should use "asyncio.run()" or "asyncio.Runner" with
    *loop_factory* to use the desired event loop implementation.

    For example, to use "asyncio.SelectorEventLoop" on Windows:

       import asyncio

       async def main():
           ...

       asyncio.run(main(), loop_factory=asyncio.SelectorEventLoop)

    (Contributed by Kumar Aditya in gh-127949.)

* "builtins":

  * Bitwise inversion on boolean types, "~True" or "~False" has been
    deprecated since Python 3.12, as it produces surprising and
    unintuitive results ("-2" and "-1"). Use "not x" instead for the
    logical negation of a Boolean. In the rare case that you need the
    bitwise inversion of the underlying integer, convert to "int"
    explicitly ("~int(x)").

* "functools":

  * Calling the Python implementation of "functools.reduce()" with
    *function* or *sequence* as keyword arguments has been deprecated
    since Python 3.14.

* "shutil":

  * The "ExecError" exception has been deprecated since Python 3.14.
    It has not been used by any function in "shutil" since Python 3.4,
    and is now an alias of "RuntimeError".

* "symtable":

  * The "Class.get_methods" method has been deprecated since Python
    3.14.

* "sys":

  * The "_enablelegacywindowsfsencoding()" function has been
    deprecated since Python 3.13. Use the
    "PYTHONLEGACYWINDOWSFSENCODING" environment variable instead.

* "sysconfig":

  * The "sysconfig.expand_makefile_vars()" function has been
    deprecated since Python 3.14. Use the "vars" argument of
    "sysconfig.get_paths()" instead.

* "tarfile":

  * The undocumented and unused "TarFile.tarfile" attribute has been
    deprecated since Python 3.13.


Pending removal in future versions
----------------------------------

The following APIs will be removed in the future, although there is
currently no date scheduled for their removal.

* "argparse":

  * Nesting argument groups and nesting mutually exclusive groups are
    deprecated.

  * Passing the undocumented keyword argument *prefix_chars* to
    "add_argument_group()" is now deprecated.

  * The "argparse.FileType" type converter is deprecated.

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

* "builtins":

  * "bool(NotImplemented)".

  * Generators: "throw(type, exc, tb)" and "athrow(type, exc, tb)"
    signature is deprecated: use "throw(exc)" and "athrow(exc)"
    instead, the single argument signature.

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

  * Support for "__index__()" and "__int__()" method returning non-int
    type: these methods will be required to return an instance of a
    strict subclass of "int".

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

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

  * Delegation of "int()" to "__trunc__()" method.

  * Passing a complex number as the *real* or *imag* argument in the
    "complex()" constructor is now deprecated; it should only be
    passed as a single positional argument. (Contributed by Serhiy
    Storchaka in gh-109218.)

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

* "codeobject.co_lnotab": use the "codeobject.co_lines()" method
  instead.

* "datetime":

  * "utcnow()": use "datetime.datetime.now(tz=datetime.UTC)".

  * "utcfromtimestamp()": use
    "datetime.datetime.fromtimestamp(timestamp, tz=datetime.UTC)".

* "gettext": Plural value must be an integer.

* "importlib":

  * "cache_from_source()" *debug_override* parameter is deprecated:
    use the *optimization* parameter instead.

* "importlib.metadata":

  * "EntryPoints" tuple interface.

  * Implicit "None" on return values.

* "logging": the "warn()" method has been deprecated since Python 3.3,
  use "warning()" instead.

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

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

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

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

* "sre_compile", "sre_constants" and "sre_parse" modules.

* "shutil": "rmtree()"'s *onerror* parameter is deprecated in Python
  3.12; use the *onexc* parameter instead.

* "ssl" options and protocols:

  * "ssl.SSLContext" without protocol argument is deprecated.

  * "ssl.SSLContext": "set_npn_protocols()" and
    "selected_npn_protocol()" are deprecated: use ALPN instead.

  * "ssl.OP_NO_SSL*" options

  * "ssl.OP_NO_TLS*" options

  * "ssl.PROTOCOL_SSLv3"

  * "ssl.PROTOCOL_TLS"

  * "ssl.PROTOCOL_TLSv1"

  * "ssl.PROTOCOL_TLSv1_1"

  * "ssl.PROTOCOL_TLSv1_2"

  * "ssl.TLSVersion.SSLv3"

  * "ssl.TLSVersion.TLSv1"

  * "ssl.TLSVersion.TLSv1_1"

* "threading" methods:

  * "threading.Condition.notifyAll()": use "notify_all()".

  * "threading.Event.isSet()": use "is_set()".

  * "threading.Thread.isDaemon()", "threading.Thread.setDaemon()": use
    "threading.Thread.daemon" attribute.

  * "threading.Thread.getName()", "threading.Thread.setName()": use
    "threading.Thread.name" attribute.

  * "threading.currentThread()": use "threading.current_thread()".

  * "threading.activeCount()": use "threading.active_count()".

* "typing.Text" (gh-92332).

* The internal class "typing._UnionGenericAlias" is no longer used to
  implement "typing.Union". To preserve compatibility with users using
  this private class, a compatibility shim will be provided until at
  least Python 3.17. (Contributed by Jelle Zijlstra in gh-105499.)

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

* "urllib.parse" deprecated functions: "urlparse()" instead

  * "splitattr()"

  * "splithost()"

  * "splitnport()"

  * "splitpasswd()"

  * "splitport()"

  * "splitquery()"

  * "splittag()"

  * "splittype()"

  * "splituser()"

  * "splitvalue()"

  * "to_bytes()"

* "wsgiref": "SimpleHandler.stdout.write()" should not do partial
  writes.

* "xml.etree.ElementTree": Testing the truth value of an "Element" is
  deprecated. In a future release it will always return "True". Prefer
  explicit "len(elem)" or "elem is not None" tests instead.

* "sys._clear_type_cache()" is deprecated: use
  "sys._clear_internal_caches()" instead.


Removed
=======


argparse
--------

* Remove the *type*, *choices*, and *metavar* parameters of
  "argparse.BooleanOptionalAction". They were deprecated since 3.12.

* Calling "add_argument_group()" on an argument group, and calling
  "add_argument_group()" or "add_mutually_exclusive_group()" on a
  mutually exclusive group now raise exceptions. This nesting was
  never supported, often failed to work correctly, and was
  unintentionally exposed through inheritance. This functionality has
  been deprecated since Python 3.11. (Contributed by Savannah
  Ostrowski in gh-127186.)


ast
---

* Remove the following classes. They were all deprecated since Python
  3.8, and have emitted deprecation warnings since Python 3.12:

  * "ast.Bytes"

  * "ast.Ellipsis"

  * "ast.NameConstant"

  * "ast.Num"

  * "ast.Str"

  Use "ast.Constant" instead. As a consequence of these removals,
  user-defined "visit_Num", "visit_Str", "visit_Bytes",
  "visit_NameConstant" and "visit_Ellipsis" methods on custom
  "ast.NodeVisitor" subclasses will no longer be called when the
  "NodeVisitor" subclass is visiting an AST. Define a "visit_Constant"
  method instead.

  Also, remove the following deprecated properties on "ast.Constant",
  which were present for compatibility with the now-removed AST
  classes:

  * "ast.Constant.n"

  * "ast.Constant.s"

  Use "ast.Constant.value" instead. (Contributed by Alex Waygood in
  gh-119562.)


asyncio
-------

* Remove the following classes and functions. They were all deprecated
  and emitted deprecation warnings since Python 3.12:

  * "asyncio.get_child_watcher()"

  * "asyncio.set_child_watcher()"

  * "asyncio.AbstractEventLoopPolicy.get_child_watcher()"

  * "asyncio.AbstractEventLoopPolicy.set_child_watcher()"

  * "asyncio.AbstractChildWatcher"

  * "asyncio.FastChildWatcher"

  * "asyncio.MultiLoopChildWatcher"

  * "asyncio.PidfdChildWatcher"

  * "asyncio.SafeChildWatcher"

  * "asyncio.ThreadedChildWatcher"

  (Contributed by Kumar Aditya in gh-120804.)

* Removed implicit creation of event loop by
  "asyncio.get_event_loop()". It now raises a "RuntimeError" if there
  is no current event loop. (Contributed by Kumar Aditya in
  gh-126353.)

  There's a few patterns that use "asyncio.get_event_loop()", most of
  them can be replaced with "asyncio.run()".

  If you're running an async function, simply use "asyncio.run()".

  Before:

     async def main():
         ...


     loop = asyncio.get_event_loop()
     try:
         loop.run_until_complete(main())
     finally:
         loop.close()

  After:

     async def main():
         ...

     asyncio.run(main())

  If you need to start something, e.g. a server listening on a socket
  and then run forever, use "asyncio.run()" and an "asyncio.Event".

  Before:

     def start_server(loop):
         ...

     loop = asyncio.get_event_loop()
     try:
         start_server(loop)
         loop.run_forever()
     finally:
         loop.close()

  After:

     def start_server(loop):
         ...

     async def main():
         start_server(asyncio.get_running_loop())
         await asyncio.Event().wait()

     asyncio.run(main())

  If you need to run something in an event loop, then run some
  blocking code around it, use "asyncio.Runner".

  Before:

     async def operation_one():
         ...

     def blocking_code():
         ...

     async def operation_two():
         ...

     loop = asyncio.get_event_loop()
     try:
         loop.run_until_complete(operation_one())
         blocking_code()
         loop.run_until_complete(operation_two())
     finally:
         loop.close()

  After:

     async def operation_one():
         ...

     def blocking_code():
         ...

     async def operation_two():
         ...

     with asyncio.Runner() as runner:
         runner.run(operation_one())
         blocking_code()
         runner.run(operation_two())


collections.abc
---------------

* Remove "collections.abc.ByteString". It had previously raised a
  "DeprecationWarning" since Python 3.12.


email
-----

* Remove the *isdst* parameter from "email.utils.localtime()".
  (Contributed by Hugo van Kemenade in gh-118798.)


importlib
---------

* Remove deprecated "importlib.abc" classes:

  * "importlib.abc.ResourceReader"

  * "importlib.abc.Traversable"

  * "importlib.abc.TraversableResources"

  Use "importlib.resources.abc" classes instead:

  * "importlib.resources.abc.Traversable"

  * "importlib.resources.abc.TraversableResources"

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


itertools
---------

* Remove "itertools" support for copy, deepcopy, and pickle
  operations. These had previously raised a "DeprecationWarning" since
  Python 3.12. (Contributed by Raymond Hettinger in gh-101588.)


pathlib
-------

* Remove support for passing additional keyword arguments to
  "pathlib.Path". In previous versions, any such arguments are
  ignored.

* Remove support for passing additional positional arguments to
  "pathlib.PurePath.relative_to()" and "is_relative_to()". In previous
  versions, any such arguments are joined onto *other*.


pkgutil
-------

* Remove deprecated "pkgutil.get_loader()" and
  "pkgutil.find_loader()". These had previously raised a
  "DeprecationWarning" since Python 3.12. (Contributed by Bénédikt
  Tran in gh-97850.)


pty
---

* Remove deprecated "pty.master_open()" and "pty.slave_open()". They
  had previously raised a "DeprecationWarning" since Python 3.12. Use
  "pty.openpty()" instead. (Contributed by Nikita Sobolev in
  gh-118824.)


sqlite3
-------

* Remove "version" and "version_info" from "sqlite3". (Contributed by
  Hugo van Kemenade in gh-118924.)

* Disallow using a sequence of parameters with named placeholders.
  This had previously raised a "DeprecationWarning" since Python 3.12;
  it will now raise a "sqlite3.ProgrammingError". (Contributed by
  Erlend E. Aasland in gh-118928 and gh-101693.)


typing
------

* Remove "typing.ByteString". It had previously raised a
  "DeprecationWarning" since Python 3.12.

* "typing.TypeAliasType" now supports star unpacking.


urllib
------

* Remove deprecated "Quoter" class from "urllib.parse". It had
  previously raised a "DeprecationWarning" since Python 3.11.
  (Contributed by Nikita Sobolev in gh-118827.)

* Remove deprecated "URLopener" and "FancyURLopener" classes from
  "urllib.request". They had previously raised a "DeprecationWarning"
  since Python 3.3.

  "myopener.open()" can be replaced with "urlopen()", and
  "myopener.retrieve()" can be replaced with "urlretrieve()".
  Customizations to the opener classes can be replaced by passing
  customized handlers to "build_opener()". (Contributed by Barney Gale
  in gh-84850.)


Others
------

* Using "NotImplemented" in a boolean context will now raise a
  "TypeError". It had previously raised a "DeprecationWarning" since
  Python 3.9. (Contributed by Jelle Zijlstra in gh-118767.)

* The "int()" built-in no longer delegates to "__trunc__()". Classes
  that want to support conversion to integer must implement either
  "__int__()" or "__index__()". (Contributed by Mark Dickinson in
  gh-119743.)


CPython Bytecode Changes
========================

* Replaced the opcode "BINARY_SUBSCR" by "BINARY_OP" with oparg
  "NB_SUBSCR". (Contributed by Irit Katriel in gh-100239.)


Porting to Python 3.14
======================

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


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

* "functools.partial" is now a method descriptor. Wrap it in
  "staticmethod()" if you want to preserve the old behavior.
  (Contributed by Serhiy Storchaka and Dominykas Grigonis in
  gh-121027.)

* The "locale.nl_langinfo()" function now sets temporarily the
  "LC_CTYPE" locale in some cases. This temporary change affects other
  threads. (Contributed by Serhiy Storchaka in gh-69998.)

* "types.UnionType" is now an alias for "typing.Union", causing
  changes in some behaviors. See above for more details. (Contributed
  by Jelle Zijlstra in gh-105499.)


Build changes
=============

* GNU Autoconf 2.72 is now required to generate "configure".
  (Contributed by Erlend Aasland in gh-115765.)

* "#pragma"-based linking with "python3*.lib" can now be switched off
  with Py_NO_LINK_LIB. (Contributed by Jean-Christophe Fillion-Robin
  in gh-82909.)


PEP 761: Discontinuation of PGP signatures
------------------------------------------

PGP signatures will not be available for CPython 3.14 and onwards.
Users verifying artifacts must use Sigstore verification materials for
verifying CPython artifacts. This change in release process is
specified in **PEP 761**.


C API changes
=============


New features
------------

* Add "PyLong_GetSign()" function to get the sign of "int" objects.
  (Contributed by Sergey B Kirpichev in gh-116560.)

* Add a new "PyUnicodeWriter" API to create a Python "str" object:

  * "PyUnicodeWriter_Create()"

  * "PyUnicodeWriter_DecodeUTF8Stateful()"

  * "PyUnicodeWriter_Discard()"

  * "PyUnicodeWriter_Finish()"

  * "PyUnicodeWriter_Format()"

  * "PyUnicodeWriter_WriteChar()"

  * "PyUnicodeWriter_WriteRepr()"

  * "PyUnicodeWriter_WriteStr()"

  * "PyUnicodeWriter_WriteSubstring()"

  * "PyUnicodeWriter_WriteUCS4()"

  * "PyUnicodeWriter_WriteUTF8()"

  * "PyUnicodeWriter_WriteWideChar()"

  (Contributed by Victor Stinner in gh-119182.)

* Add "PyIter_NextItem()" to replace "PyIter_Next()", which has an
  ambiguous return value. (Contributed by Irit Katriel and Erlend
  Aasland in gh-105201.)

* Add "PyLong_IsPositive()", "PyLong_IsNegative()" and
  "PyLong_IsZero()" for checking if "PyLongObject" is positive,
  negative, or zero, respectively. (Contributed by James Roy and
  Sergey B Kirpichev in gh-126061.)

* Add new functions to convert C "<stdint.h>" numbers from/to Python
  "int":

  * "PyLong_AsInt32()"

  * "PyLong_AsInt64()"

  * "PyLong_AsUInt32()"

  * "PyLong_AsUInt64()"

  * "PyLong_FromInt32()"

  * "PyLong_FromInt64()"

  * "PyLong_FromUInt32()"

  * "PyLong_FromUInt64()"

  (Contributed by Victor Stinner in gh-120389.)

* Add "PyBytes_Join(sep, iterable)" function, similar to
  "sep.join(iterable)" in Python. (Contributed by Victor Stinner in
  gh-121645.)

* Add "Py_HashBuffer()" to compute and return the hash value of a
  buffer. (Contributed by Antoine Pitrou and Victor Stinner in
  gh-122854.)

* Add functions to get and set the current runtime Python
  configuration (**PEP 741**):

  * "PyConfig_Get()"

  * "PyConfig_GetInt()"

  * "PyConfig_Set()"

  * "PyConfig_Names()"

  (Contributed by Victor Stinner in gh-107954.)

* Add functions to configure the Python initialization (**PEP 741**):

  * "Py_InitializeFromInitConfig()"

  * "PyInitConfig_AddModule()"

  * "PyInitConfig_Create()"

  * "PyInitConfig_Free()"

  * "PyInitConfig_FreeStrList()"

  * "PyInitConfig_GetError()"

  * "PyInitConfig_GetExitCode()"

  * "PyInitConfig_GetInt()"

  * "PyInitConfig_GetStr()"

  * "PyInitConfig_GetStrList()"

  * "PyInitConfig_HasOption()"

  * "PyInitConfig_SetInt()"

  * "PyInitConfig_SetStr()"

  * "PyInitConfig_SetStrList()"

  (Contributed by Victor Stinner in gh-107954.)

* Add a new import and export API for Python "int" objects (**PEP
  757**):

  * "PyLong_GetNativeLayout()";

  * "PyLong_Export()";

  * "PyLong_FreeExport()";

  * "PyLongWriter_Create()";

  * "PyLongWriter_Finish()";

  * "PyLongWriter_Discard()".

  (Contributed by Sergey B Kirpichev and Victor Stinner in gh-102471.)

* Add "PyType_GetBaseByToken()" and "Py_tp_token" slot for easier
  superclass identification, which attempts to resolve the type
  checking issue mentioned in **PEP 630** (gh-124153).

* Add "PyUnicode_Equal()" function to the limited C API: test if two
  strings are equal. (Contributed by Victor Stinner in gh-124502.)

* Add "PyType_Freeze()" function to make a type immutable.
  (Contributed by Victor Stinner in gh-121654.)

* Add "PyUnstable_Object_EnableDeferredRefcount()" for enabling
  deferred reference counting, as outlined in **PEP 703**.

* Add "PyMonitoring_FireBranchLeftEvent()" and
  "PyMonitoring_FireBranchRightEvent()" for generating "BRANCH_LEFT"
  and "BRANCH_RIGHT" events, respectively.

* Add "Py_fopen()" function to open a file. Similar to the "fopen()"
  function, but the *path* parameter is a Python object and an
  exception is set on error. Add also "Py_fclose()" function to close
  a file. (Contributed by Victor Stinner in gh-127350.)

* Add support of nullable arguments in "PyArg_ParseTuple()" and
  similar functions. Adding "?" after any format unit makes "None" be
  accepted as a value. (Contributed by Serhiy Storchaka in gh-112068.)

* The "k" and "K" formats in "PyArg_ParseTuple()" and similar
  functions now use "__index__()" if available, like all other integer
  formats. (Contributed by Serhiy Storchaka in gh-112068.)

* Add macros "Py_PACK_VERSION()" and "Py_PACK_FULL_VERSION()" for bit-
  packing Python version numbers. (Contributed by Petr Viktorin in
  gh-128629.)

* Add "PyUnstable_IsImmortal()" for determining whether an object is
  *immortal*, for debugging purposes.

* Add "PyImport_ImportModuleAttr()" and
  "PyImport_ImportModuleAttrString()" helper functions to import a
  module and get an attribute of the module. (Contributed by Victor
  Stinner in gh-128911.)

* Add support for a new "p" format unit in "Py_BuildValue()" that
  allows to take a C integer and produce a Python "bool" object.
  (Contributed by Pablo Galindo in bpo-45325.)


Limited C API changes
---------------------

* In the limited C API 3.14 and newer, "Py_TYPE()" and "Py_REFCNT()"
  are now implemented as an opaque function call to hide
  implementation details. (Contributed by Victor Stinner in gh-120600
  and gh-124127.)

* Remove the "PySequence_Fast_GET_SIZE", "PySequence_Fast_GET_ITEM"
  and "PySequence_Fast_ITEMS" macros from the limited C API, since
  these macros never worked in the limited C API. Keep
  "PySequence_Fast()" in the limited C API. (Contributed by Victor
  Stinner in gh-91417.)


Porting to Python 3.14
----------------------

* "Py_Finalize()" now deletes all interned strings. This is backwards
  incompatible to any C-Extension that holds onto an interned string
  after a call to "Py_Finalize()" and is then reused after a call to
  "Py_Initialize()".  Any issues arising from this behavior will
  normally result in crashes during the execution of the subsequent
  call to "Py_Initialize()" from accessing uninitialized memory. To
  fix, use an address sanitizer to identify any use-after-free coming
  from an interned string and deallocate it during module shutdown.
  (Contributed by Eddie Elizondo in gh-113601.)

* The Unicode Exception Objects C API now raises a "TypeError" if its
  exception argument is not a "UnicodeError" object. (Contributed by
  Bénédikt Tran in gh-127691.)

* Private functions promoted to public C APIs:

  * "_PyBytes_Join()": "PyBytes_Join()".

  * "_PyLong_IsNegative()": "PyLong_IsNegative()".

  * "_PyLong_IsPositive()": "PyLong_IsPositive()".

  * "_PyLong_IsZero()": "PyLong_IsZero()".

  * "_PyLong_Sign()": "PyLong_GetSign()".

  * "_PyUnicodeWriter_Dealloc()": "PyUnicodeWriter_Discard()".

  * "_PyUnicodeWriter_Finish()": "PyUnicodeWriter_Finish()".

  * "_PyUnicodeWriter_Init()": use "PyUnicodeWriter_Create()".

  * "_PyUnicodeWriter_Prepare()": (no replacement).

  * "_PyUnicodeWriter_PrepareKind()": (no replacement).

  * "_PyUnicodeWriter_WriteChar()": "PyUnicodeWriter_WriteChar()".

  * "_PyUnicodeWriter_WriteStr()": "PyUnicodeWriter_WriteStr()".

  * "_PyUnicodeWriter_WriteSubstring()":
    "PyUnicodeWriter_WriteSubstring()".

  * "_PyUnicode_EQ()": "PyUnicode_Equal()".

  * "_PyUnicode_Equal()": "PyUnicode_Equal()".

  * "_Py_GetConfig()": "PyConfig_Get()" and "PyConfig_GetInt()".

  * "_Py_HashBytes()": "Py_HashBuffer()".

  * "_Py_fopen_obj()": "Py_fopen()".

  The pythoncapi-compat project can be used to get most of these new
  functions on Python 3.13 and older.


Deprecated
----------

* The "Py_HUGE_VAL" macro is *soft deprecated*, use "Py_INFINITY"
  instead. (Contributed by Sergey B Kirpichev in gh-120026.)

* Macros "Py_IS_NAN", "Py_IS_INFINITY" and "Py_IS_FINITE" are *soft
  deprecated*, use instead "isnan", "isinf" and "isfinite" available
  from "math.h" since C99.  (Contributed by Sergey B Kirpichev in
  gh-119613.)

* Non-tuple sequences are deprecated as argument for the "(items)"
  format unit in "PyArg_ParseTuple()" and other argument parsing
  functions if *items* contains format units which store a borrowed
  buffer or a *borrowed reference*. (Contributed by Serhiy Storchaka
  in gh-50333.)

* The previously undocumented function "PySequence_In()" is *soft
  deprecated*. Use "PySequence_Contains()" instead. (Contributed by
  Yuki Kobayashi in gh-127896.)

* The "PyMonitoring_FireBranchEvent" function is deprecated and should
  be replaced with calls to "PyMonitoring_FireBranchLeftEvent()" and
  "PyMonitoring_FireBranchRightEvent()".

* The following private functions are deprecated and planned for
  removal in Python 3.18:

  * "_PyBytes_Join()": use "PyBytes_Join()".

  * "_PyDict_GetItemStringWithError()": use
    "PyDict_GetItemStringRef()".

  * "_PyDict_Pop()": use "PyDict_Pop()".

  * "_PyLong_Sign()": use "PyLong_GetSign()".

  * "_PyLong_FromDigits()" and "_PyLong_New()": use
    "PyLongWriter_Create()".

  * "_PyThreadState_UncheckedGet()": use
    "PyThreadState_GetUnchecked()".

  * "_PyUnicode_AsString()": use "PyUnicode_AsUTF8()".

  * "_PyUnicodeWriter_Init()": replace
    "_PyUnicodeWriter_Init(&writer)" with "writer =
    PyUnicodeWriter_Create(0)".

  * "_PyUnicodeWriter_Finish()": replace
    "_PyUnicodeWriter_Finish(&writer)" with
    "PyUnicodeWriter_Finish(writer)".

  * "_PyUnicodeWriter_Dealloc()": replace
    "_PyUnicodeWriter_Dealloc(&writer)" with
    "PyUnicodeWriter_Discard(writer)".

  * "_PyUnicodeWriter_WriteChar()": replace
    "_PyUnicodeWriter_WriteChar(&writer, ch)" with
    "PyUnicodeWriter_WriteChar(writer, ch)".

  * "_PyUnicodeWriter_WriteStr()": replace
    "_PyUnicodeWriter_WriteStr(&writer, str)" with
    "PyUnicodeWriter_WriteStr(writer, str)".

  * "_PyUnicodeWriter_WriteSubstring()": replace
    "_PyUnicodeWriter_WriteSubstring(&writer, str, start, end)" with
    "PyUnicodeWriter_WriteSubstring(writer, str, start, end)".

  * "_PyUnicodeWriter_WriteASCIIString()": replace
    "_PyUnicodeWriter_WriteASCIIString(&writer, str)" with
    "PyUnicodeWriter_WriteUTF8(writer, str)".

  * "_PyUnicodeWriter_WriteLatin1String()": replace
    "_PyUnicodeWriter_WriteLatin1String(&writer, str)" with
    "PyUnicodeWriter_WriteUTF8(writer, str)".

  * "_Py_HashPointer()": use "Py_HashPointer()".

  * "_Py_fopen_obj()": use "Py_fopen()".

  The pythoncapi-compat project can be used to get these new public
  functions on Python 3.13 and older. (Contributed by Victor Stinner
  in gh-128863.)


Pending removal in Python 3.15
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* The bundled copy of "libmpdecimal".

* The "PyImport_ImportModuleNoBlock()": Use "PyImport_ImportModule()"
  instead.

* "PyWeakref_GetObject()" and "PyWeakref_GET_OBJECT()": Use
  "PyWeakref_GetRef()" instead. The pythoncapi-compat project can be
  used to get "PyWeakref_GetRef()" on Python 3.12 and older.

* "Py_UNICODE" type and the "Py_UNICODE_WIDE" macro: Use "wchar_t"
  instead.

* "PyUnicode_AsDecodedObject()": Use "PyCodec_Decode()" instead.

* "PyUnicode_AsDecodedUnicode()": Use "PyCodec_Decode()" instead; Note
  that some codecs (for example, "base64") may return a type other
  than "str", such as "bytes".

* "PyUnicode_AsEncodedObject()": Use "PyCodec_Encode()" instead.

* "PyUnicode_AsEncodedUnicode()": Use "PyCodec_Encode()" instead; Note
  that some codecs (for example, "base64") may return a type other
  than "bytes", such as "str".

* Python initialization functions, deprecated in Python 3.13:

  * "Py_GetPath()": Use "PyConfig_Get("module_search_paths")"
    ("sys.path") instead.

  * "Py_GetPrefix()": Use "PyConfig_Get("base_prefix")"
    ("sys.base_prefix") instead. Use "PyConfig_Get("prefix")"
    ("sys.prefix") if virtual environments need to be handled.

  * "Py_GetExecPrefix()": Use "PyConfig_Get("base_exec_prefix")"
    ("sys.base_exec_prefix") instead. Use
    "PyConfig_Get("exec_prefix")" ("sys.exec_prefix") if virtual
    environments need to be handled.

  * "Py_GetProgramFullPath()": Use "PyConfig_Get("executable")"
    ("sys.executable") instead.

  * "Py_GetProgramName()": Use "PyConfig_Get("executable")"
    ("sys.executable") instead.

  * "Py_GetPythonHome()": Use "PyConfig_Get("home")" or the
    "PYTHONHOME" environment variable instead.

  The pythoncapi-compat project can be used to get "PyConfig_Get()" on
  Python 3.13 and older.

* Functions to configure Python's initialization, deprecated in Python
  3.11:

  * "PySys_SetArgvEx()": Set "PyConfig.argv" instead.

  * "PySys_SetArgv()": Set "PyConfig.argv" instead.

  * "Py_SetProgramName()": Set "PyConfig.program_name" instead.

  * "Py_SetPythonHome()": Set "PyConfig.home" instead.

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

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

* Global configuration variables:

  * "Py_DebugFlag": Use "PyConfig.parser_debug" or
    "PyConfig_Get("parser_debug")" instead.

  * "Py_VerboseFlag": Use "PyConfig.verbose" or
    "PyConfig_Get("verbose")" instead.

  * "Py_QuietFlag": Use "PyConfig.quiet" or "PyConfig_Get("quiet")"
    instead.

  * "Py_InteractiveFlag": Use "PyConfig.interactive" or
    "PyConfig_Get("interactive")" instead.

  * "Py_InspectFlag": Use "PyConfig.inspect" or
    "PyConfig_Get("inspect")" instead.

  * "Py_OptimizeFlag": Use "PyConfig.optimization_level" or
    "PyConfig_Get("optimization_level")" instead.

  * "Py_NoSiteFlag": Use "PyConfig.site_import" or
    "PyConfig_Get("site_import")" instead.

  * "Py_BytesWarningFlag": Use "PyConfig.bytes_warning" or
    "PyConfig_Get("bytes_warning")" instead.

  * "Py_FrozenFlag": Use "PyConfig.pathconfig_warnings" or
    "PyConfig_Get("pathconfig_warnings")" instead.

  * "Py_IgnoreEnvironmentFlag": Use "PyConfig.use_environment" or
    "PyConfig_Get("use_environment")" instead.

  * "Py_DontWriteBytecodeFlag": Use "PyConfig.write_bytecode" or
    "PyConfig_Get("write_bytecode")" instead.

  * "Py_NoUserSiteDirectory": Use "PyConfig.user_site_directory" or
    "PyConfig_Get("user_site_directory")" instead.

  * "Py_UnbufferedStdioFlag": Use "PyConfig.buffered_stdio" or
    "PyConfig_Get("buffered_stdio")" instead.

  * "Py_HashRandomizationFlag": Use "PyConfig.use_hash_seed" and
    "PyConfig.hash_seed" or "PyConfig_Get("hash_seed")" instead.

  * "Py_IsolatedFlag": Use "PyConfig.isolated" or
    "PyConfig_Get("isolated")" instead.

  * "Py_LegacyWindowsFSEncodingFlag": Use
    "PyPreConfig.legacy_windows_fs_encoding" or
    "PyConfig_Get("legacy_windows_fs_encoding")" instead.

  * "Py_LegacyWindowsStdioFlag": Use "PyConfig.legacy_windows_stdio"
    or "PyConfig_Get("legacy_windows_stdio")" instead.

  * "Py_FileSystemDefaultEncoding", "Py_HasFileSystemDefaultEncoding":
    Use "PyConfig.filesystem_encoding" or
    "PyConfig_Get("filesystem_encoding")" instead.

  * "Py_FileSystemDefaultEncodeErrors": Use
    "PyConfig.filesystem_errors" or
    "PyConfig_Get("filesystem_errors")" instead.

  * "Py_UTF8Mode": Use "PyPreConfig.utf8_mode" or
    "PyConfig_Get("utf8_mode")" instead. (see "Py_PreInitialize()")

  The "Py_InitializeFromConfig()" API should be used with "PyConfig"
  to set these options. Or "PyConfig_Get()" can be used to get these
  options at runtime.


Pending removal in Python 3.18
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* Deprecated private functions (gh-128863):

  * "_PyBytes_Join()": use "PyBytes_Join()".

  * "_PyDict_GetItemStringWithError()": use
    "PyDict_GetItemStringRef()".

  * "_PyDict_Pop()": "PyDict_Pop()".

  * "_PyLong_Sign()": use "PyLong_GetSign()".

  * "_PyLong_FromDigits()" and "_PyLong_New()": use
    "PyLongWriter_Create()".

  * "_PyThreadState_UncheckedGet()": use
    "PyThreadState_GetUnchecked()".

  * "_PyUnicode_AsString()": use "PyUnicode_AsUTF8()".

  * "_PyUnicodeWriter_Init()": replace
    "_PyUnicodeWriter_Init(&writer)" with "writer =
    PyUnicodeWriter_Create(0)".

  * "_PyUnicodeWriter_Finish()": replace
    "_PyUnicodeWriter_Finish(&writer)" with
    "PyUnicodeWriter_Finish(writer)".

  * "_PyUnicodeWriter_Dealloc()": replace
    "_PyUnicodeWriter_Dealloc(&writer)" with
    "PyUnicodeWriter_Discard(writer)".

  * "_PyUnicodeWriter_WriteChar()": replace
    "_PyUnicodeWriter_WriteChar(&writer, ch)" with
    "PyUnicodeWriter_WriteChar(writer, ch)".

  * "_PyUnicodeWriter_WriteStr()": replace
    "_PyUnicodeWriter_WriteStr(&writer, str)" with
    "PyUnicodeWriter_WriteStr(writer, str)".

  * "_PyUnicodeWriter_WriteSubstring()": replace
    "_PyUnicodeWriter_WriteSubstring(&writer, str, start, end)" with
    "PyUnicodeWriter_WriteSubstring(writer, str, start, end)".

  * "_PyUnicodeWriter_WriteASCIIString()": replace
    "_PyUnicodeWriter_WriteASCIIString(&writer, str)" with
    "PyUnicodeWriter_WriteUTF8(writer, str)".

  * "_PyUnicodeWriter_WriteLatin1String()": replace
    "_PyUnicodeWriter_WriteLatin1String(&writer, str)" with
    "PyUnicodeWriter_WriteUTF8(writer, str)".

  * "_PyUnicodeWriter_Prepare()": (no replacement).

  * "_PyUnicodeWriter_PrepareKind()": (no replacement).

  * "_Py_HashPointer()": use "Py_HashPointer()".

  * "_Py_fopen_obj()": use "Py_fopen()".

  The pythoncapi-compat project can be used to get these new public
  functions on Python 3.13 and older.


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()" instead.

* "PyErr_NormalizeException()": Use "PyErr_GetRaisedException()"
  instead.

* "PyErr_Restore()": Use "PyErr_SetRaisedException()" instead.

* "PyModule_GetFilename()": Use "PyModule_GetFilenameObject()"
  instead.

* "PyOS_AfterFork()": Use "PyOS_AfterFork_Child()" instead.

* "PySlice_GetIndicesEx()": Use "PySlice_Unpack()" and
  "PySlice_AdjustIndices()" instead.

* "PyUnicode_READY()": Unneeded since Python 3.12

* "PyErr_Display()": Use "PyErr_DisplayException()" instead.

* "_PyErr_ChainExceptions()": Use "_PyErr_ChainExceptions1()" instead.

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

* Thread Local Storage (TLS) API:

  * "PyThread_create_key()": Use "PyThread_tss_alloc()" instead.

  * "PyThread_delete_key()": Use "PyThread_tss_free()" instead.

  * "PyThread_set_key_value()": Use "PyThread_tss_set()" instead.

  * "PyThread_get_key_value()": Use "PyThread_tss_get()" instead.

  * "PyThread_delete_key_value()": Use "PyThread_tss_delete()"
    instead.

  * "PyThread_ReInitTLS()": Unneeded since Python 3.7.


Removed
-------

* Creating "immutable types" with mutable bases was deprecated since
  3.12 and now raises a "TypeError".

* Remove "PyDictObject.ma_version_tag" member which was deprecated
  since Python 3.12. Use the "PyDict_AddWatcher()" API instead.
  (Contributed by Sam Gross in gh-124296.)

* Remove the private "_Py_InitializeMain()" function. It was a
  *provisional API* added to Python 3.8 by **PEP 587**. (Contributed
  by Victor Stinner in gh-129033.)
