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


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


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')}
   >>> 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 Python
3.14, the behavior of code using "from __future__ import annotations"
is unchanged.


Improved Error Messages
-----------------------

* 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)


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

* 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.)


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.)


ast
---

* Add "ast.compare()" for comparing two ASTs. (Contributed by Batuhan
  Taskaya and Jeremy Hylton in bpo-15987.)

* 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.)


ctypes
------

* The layout of bit fields in "Structure" and "Union" now matches
  platform defaults (GCC/Clang or MVSC) 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.)


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()", and

  * "dis.disassemble()".

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


fractions
---------

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


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.)


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.)


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.)


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.)


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.)


datetime
--------

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


os
--

* Add the "os.environ.refresh()" method to update "os.environ" 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.)


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.)


pdb
---

* Hard-coded 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 hard-coded 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.)


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.)


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.)


symtable
--------

* Expose the following "symtable.Symbol" methods:

  * "is_free_class()"

  * "is_comp_iter()"

  * "is_comp_cell()"

  (Contributed by Bénédikt Tran in gh-120029.)


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

* The Unicode database has been updated to Unicode 16.0.0.


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


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.)


Deprecated
==========

* "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.)

* "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.)

* "multiprocessing" and "concurrent.futures": The default start method
  (see Contexts and start methods) changed away from *fork* to
  *forkserver* on platforms where it was not already *spawn* (Windows
  & macOS). If you require the threading incompatible *fork* start
  method you must explicitly specify it when using "multiprocessing"
  or "concurrent.futures" APIs. (Contributed by Gregory P. Smith in
  gh-84559.)

* "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.)

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


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

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

* "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.

* "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.

* "typing":

  * The undocumented keyword argument syntax for creating "NamedTuple"
    classes (e.g. "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.


Pending Removal in Python 3.16
------------------------------

* "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)").

* "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": "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.)

* "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.

* "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.

* "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":

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

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

* "importlib.metadata":

  * "EntryPoints" tuple interface.

  * Implicit "None" on return values.

* "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"

* "sysconfig.is_python_build()" *check_home* parameter is deprecated
  and ignored.

* "threading" methods:

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

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

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

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

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

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

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

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

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

  * "splitattr()"

  * "splithost()"

  * "splitnport()"

  * "splitpasswd()"

  * "splitport()"

  * "splitquery()"

  * "splittag()"

  * "splittype()"

  * "splituser()"

  * "splitvalue()"

  * "to_bytes()"

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

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

* "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.

* "zipimport.zipimporter.load_module()" is deprecated: use
  "exec_module()" instead.


Removed
=======


argparse
--------

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


ast
---

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

  * "ast.Num"

  * "ast.Str"

  * "ast.Bytes"

  * "ast.NameConstant"

  * "ast.Ellipsis"

  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.AbstractChildWatcher"

  * "asyncio.SafeChildWatcher"

  * "asyncio.MultiLoopChildWatcher"

  * "asyncio.FastChildWatcher"

  * "asyncio.ThreadedChildWatcher"

  * "asyncio.PidfdChildWatcher"

  * "asyncio.AbstractEventLoopPolicy.get_child_watcher()"

  * "asyncio.AbstractEventLoopPolicy.set_child_watcher()"

  * "asyncio.get_child_watcher()"

  * "asyncio.set_child_watcher()"

  (Contributed by Kumar Aditya in gh-120804.)


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*.


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.


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.)


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.)


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.)


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


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_Discard()"

  * "PyUnicodeWriter_Finish()"

  * "PyUnicodeWriter_WriteChar()"

  * "PyUnicodeWriter_WriteUTF8()"

  * "PyUnicodeWriter_WriteUCS4()"

  * "PyUnicodeWriter_WriteWideChar()"

  * "PyUnicodeWriter_WriteStr()"

  * "PyUnicodeWriter_WriteRepr()"

  * "PyUnicodeWriter_WriteSubstring()"

  * "PyUnicodeWriter_Format()"

  * "PyUnicodeWriter_DecodeUTF8Stateful()"

  (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.)

* "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.)

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

  * "PyLong_FromInt32()"

  * "PyLong_FromInt64()"

  * "PyLong_FromUInt32()"

  * "PyLong_FromUInt64()"

  * "PyLong_AsInt32()"

  * "PyLong_AsInt64()"

  * "PyLong_AsUInt32()"

  * "PyLong_AsUInt64()"

  (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**):

  * "PyInitConfig_Create()"

  * "PyInitConfig_Free()"

  * "PyInitConfig_GetError()"

  * "PyInitConfig_GetExitCode()"

  * "PyInitConfig_HasOption()"

  * "PyInitConfig_GetInt()"

  * "PyInitConfig_GetStr()"

  * "PyInitConfig_GetStrList()"

  * "PyInitConfig_FreeStrList()"

  * "PyInitConfig_SetInt()"

  * "PyInitConfig_SetStr()"

  * "PyInitConfig_SetStrList()"

  * "PyInitConfig_AddModule()"

  * "Py_InitializeFromInitConfig()"

  (Contributed by Victor Stinner in gh-107954.)

* 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.)


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

* 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.)


Deprecated
----------

* 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.)


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.

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

* Python initialization functions:

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

  * "Py_GetExecPrefix()": Get "sys.exec_prefix" instead.

  * "Py_GetPath()": Get "sys.path" instead.

  * "Py_GetPrefix()": Get "sys.prefix" instead.

  * "Py_GetProgramFullPath()": Get "sys.executable" instead.

  * "Py_GetProgramName()": Get "sys.executable" instead.

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


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_AsDecodedObject()": Use "PyCodec_Decode()" instead.

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

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

* "PyUnicode_AsEncodedUnicode()": Use "PyCodec_Encode()" 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.

* "PyDictObject.ma_version_tag" member.

* 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".
