3.13.rst

What's New In Python 3.13

Editor

TBD

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

For full details, see the changelog <changelog>.

Note

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

Summary -- Release highlights

New Features

Other Language Changes

• Allow the count argument of str.replace to be a keyword. (Contributed by Hugo van Kemenade in 106487.)
• Compiler now strip indents from docstrings. This will reduce the size of bytecode cache <bytecode> (e.g. .pyc file). For example, cache file size for sqlalchemy.orm.session in SQLAlchemy 2.0 is reduced by about 5%. This change will affect tools using docstrings, like doctest. (Contributed by Inada Naoki in 81283.)
• The compile built-in can now accept a new flag, ast.PyCF_OPTIMIZED_AST, which is similar to ast.PyCF_ONLY_AST except that the returned AST is optimized according to the value of the optimize argument. (Contributed by Irit Katriel in 108113).

New Modules

• None yet.

Improved Modules

ast

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

array

• Add 'w' type code (Py_UCS4) that can be used for Unicode strings. It can be used instead of 'u' type code, which is deprecated. (Contributed by Inada Naoki in 80480.)

dbm

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

doctest

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

io

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

opcode

• Move opcode.ENABLE_SPECIALIZATION to _opcode.ENABLE_SPECIALIZATION. This field was added in 3.12, it was never documented and is not intended for external usage. (Contributed by Irit Katriel in 105481.)
• Removed opcode.is_pseudo, opcode.MIN_PSEUDO_OPCODE and opcode.MAX_PSEUDO_OPCODE, which were added in 3.12, were never documented or exposed through dis, and were not intended to be used externally.

pathlib

• Add pathlib.UnsupportedOperation, which is raised instead of NotImplementedError when a path operation isn't supported. (Contributed by Barney Gale in 89812.)
• Add support for recursive wildcards in pathlib.PurePath.match. (Contributed by Barney Gale in 73435.)
• Add follow_symlinks keyword-only argument to pathlib.Path.glob, ~pathlib.Path.rglob, ~pathlib.Path.is_file, and ~pathlib.Path.is_dir. (Contributed by Barney Gale in 77609 and 105793.)

pdb

• Add ability to move between chained exceptions during post mortem debugging in ~pdb.pm using the new exceptions [exc_number] command for Pdb. (Contributed by Matthias Bussonnier in 106676.)
• Expressions/Statements whose prefix is a pdb command are now correctly identified and executed. (Contributed by Tian Gao in 108464.)

sqlite3

• A ResourceWarning is now emitted if a sqlite3.Connection object is not closed <sqlite3.Connection.close> explicitly. (Contributed by Erlend E. Aasland in 105539.)

tkinter

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

traceback

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

typing

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

Optimizations

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

Deprecated

• array: array's 'u' format code, deprecated in docs since Python 3.3, emits DeprecationWarning since 3.13 and will be removed in Python 3.16. Use the 'w' format code instead. (contributed by Hugo van Kemenade in 80480)
• ctypes: Deprecate undocumented !ctypes.SetPointerType and !ctypes.ARRAY functions. Replace ctypes.ARRAY(item_type, size) with item_type * size. (Contributed by Victor Stinner in 105733.)
• getopt and optparse modules: They are now soft deprecated: the argparse should be used for new projects. Previously, the optparse module was already deprecated, its removal was not scheduled, and no warnings was emitted: so there is no change in practice. (Contributed by Victor Stinner in 106535.)
• typing: Creating a typing.NamedTuple class using keyword arguments to denote the fields (NT = NamedTuple("NT", x=int, y=int)) is deprecated, and will be disallowed in Python 3.15. Use the class-based syntax or the functional syntax instead. (Contributed by Alex Waygood in 105566.)
  • When using the functional syntax to create a typing.NamedTuple class or a typing.TypedDict class, failing to pass a value to the 'fields' parameter (NT = NamedTuple("NT") or TD = TypedDict("TD")) is deprecated. Passing None to the 'fields' parameter (NT = NamedTuple("NT", None) or TD = TypedDict("TD", None)) is also deprecated. Both will be disallowed in Python 3.15. To create a NamedTuple class with 0 fields, use class NT(NamedTuple): pass or NT = NamedTuple("NT", []). To create a TypedDict class with 0 fields, use class TD(TypedDict): pass or TD = TypedDict("TD", {}). (Contributed by Alex Waygood in 105566 and 105570.)
  • typing.no_type_check_decorator is deprecated, and scheduled for removal in Python 3.15. After eight years in the typing module, it has yet to be supported by any major type checkers. (Contributed by Alex Waygood in 106309.)
  • typing.AnyStr is deprecated. In Python 3.16, it will be removed from typing.__all__, and a DeprecationWarning will be emitted when it is imported or accessed. It will be removed entirely in Python 3.18. Use the new type parameter syntax <type-params> instead. (Contributed by Michael The in 107116.)
• wave: Deprecate the getmark(), setmark() and getmarkers() methods of the wave.Wave_read and wave.Wave_write classes. They will be removed in Python 3.15. (Contributed by Victor Stinner in 105096.)

• Passing more than one positional argument to sqlite3.connect and the sqlite3.Connection constructor is deprecated. The remaining parameters will become keyword-only in Python 3.15.

  Deprecate passing name, number of arguments, and the callable as keyword arguments, for the following sqlite3.Connection APIs:

  • ~sqlite3.Connection.create_function
  • ~sqlite3.Connection.create_aggregate

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

  • ~sqlite3.Connection.set_authorizer
  • ~sqlite3.Connection.set_progress_handler
  • ~sqlite3.Connection.set_trace_callback

  The affected parameters will become positional-only in Python 3.15.

  (Contributed by Erlend E. Aasland in 107948 and 108278.)

Pending Removal in Python 3.14

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

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

  • !ast.Num
  • !ast.Str
  • !ast.Bytes
  • !ast.NameConstant
  • !ast.Ellipsis

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

• collections.abc: Deprecated ~collections.abc.ByteString. Prefer !Sequence or ~collections.abc.Buffer. For use in typing, prefer a union, like bytes | bytearray, or collections.abc.Buffer. (Contributed by Shantanu Jain in 91896.)
• email: Deprecated the isdst parameter in email.utils.localtime. (Contributed by Alan Williams in 72346.)
• importlib: __package__ and __cached__ will cease to be set or taken into consideration by the import system (97879).

• importlib.abc deprecated classes:

  • !importlib.abc.ResourceReader
  • !importlib.abc.Traversable
  • !importlib.abc.TraversableResources

  Use importlib.resources.abc classes instead:

  • importlib.resources.abc.Traversable
  • importlib.resources.abc.TraversableResources

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

• itertools had undocumented, inefficient, historically buggy, and inconsistent support for copy, deepcopy, and pickle operations. This will be removed in 3.14 for a significant reduction in code volume and maintenance burden. (Contributed by Raymond Hettinger in 101588.)
• multiprocessing: The default start method will change to a safer one on Linux, BSDs, and other non-macOS POSIX platforms where 'fork' is currently the default (84559). Adding a runtime warning about this was deemed too disruptive as the majority of code is not expected to care. Use the ~multiprocessing.get_context or ~multiprocessing.set_start_method APIs to explicitly specify when your code requires 'fork'. See multiprocessing-start-methods.
• pathlib: ~pathlib.PurePath.is_relative_to, ~pathlib.PurePath.relative_to: passing additional arguments is deprecated.
• pkgutil.find_loader and pkgutil.get_loader now raise DeprecationWarning; use importlib.util.find_spec instead. (Contributed by Nikita Sobolev in 97850.)
• pty:
  • master_open(): use pty.openpty.
  • slave_open(): use pty.openpty.
• shutil.rmtree onerror parameter is deprecated in 3.12, and will be removed in 3.14: use the onexc parameter instead.
• sqlite3:
  • ~sqlite3.version and ~sqlite3.version_info.
  • ~sqlite3.Cursor.execute and ~sqlite3.Cursor.executemany if named placeholders <sqlite3-placeholders> are used and parameters is a sequence instead of a dict.
  • date and datetime adapter, date and timestamp converter: see the sqlite3 documentation for suggested replacement recipes.
• types.CodeType: Accessing co_lnotab was deprecated in 626 since 3.10 and was planned to be removed in 3.12, but it only got a proper DeprecationWarning in 3.12. May be removed in 3.14. (Contributed by Nikita Sobolev in 101866.)
• typing: ~typing.ByteString, deprecated since Python 3.9, now causes a DeprecationWarning to be emitted when it is used.
• !urllib.parse.Quoter is deprecated: it was not intended to be a public API. (Contributed by Gregory P. Smith in 88168.)
• xml.etree.ElementTree: Testing the truth value of an ~xml.etree.ElementTree.Element is deprecated and will raise an exception in Python 3.14.

Pending Removal in Python 3.15

• typing.NamedTuple:
  • The undocumented keyword argument syntax for creating NamedTuple classes (NT = NamedTuple("NT", x=int)) is deprecated, and will be disallowed in 3.15. Use the class-based syntax or the functional syntax instead.
  • When using the functional syntax to create a NamedTuple class, failing to pass a value to the 'fields' parameter (NT = NamedTuple("NT")) is deprecated. Passing None to the 'fields' parameter (NT = NamedTuple("NT", None)) is also deprecated. Both will be disallowed in Python 3.15. To create a NamedTuple class with 0 fields, use class NT(NamedTuple): pass or NT = NamedTuple("NT", []).
• typing.TypedDict: When using the functional syntax to create a TypedDict class, failing to pass a value to the 'fields' parameter (TD = TypedDict("TD")) is deprecated. Passing None to the 'fields' parameter (TD = TypedDict("TD", None)) is also deprecated. Both will be disallowed in Python 3.15. To create a TypedDict class with 0 fields, use class TD(TypedDict): pass or TD = TypedDict("TD", {}).
• wave: Deprecate the getmark(), setmark() and getmarkers() methods of the wave.Wave_read and wave.Wave_write classes. They will be removed in Python 3.15. (Contributed by Victor Stinner in 105096.)
• Passing any arguments to threading.RLock is now deprecated. C version allows any numbers of args and kwargs, but they are just ignored. Python version does not allow any arguments. All arguments will be removed from threading.RLock in Python 3.15. (Contributed by Nikita Sobolev in 102029.)

Pending Removal in Python 3.16

• array.array 'u' type (:cwchar_t): use the 'w' type instead (Py_UCS4).

Pending Removal in Future Versions

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

• argparse: Nesting argument groups and nesting mutually exclusive groups are deprecated.
• builtins:
  • ~bool, bitwise inversion on bool.
  • bool(NotImplemented).
  • Generators: throw(type, exc, tb) and athrow(type, exc, tb) signature is deprecated: use throw(exc) and athrow(exc) instead, the single argument signature.
  • Currently Python accepts numeric literals immediately followed by keywords, for example 0in x, 1or x, 0if 1else 2. It allows confusing and ambiguous expressions like [0x1for x in y] (which can be interpreted as [0x1 for x in y] or [0x1f or x in y]). A syntax warning is raised if the numeric literal is immediately followed by one of keywords and, else, for, if, in, is and or. In a future release it will be changed to a syntax error. (87999)
  • Support for __index__() and __int__() method returning non-int type: these methods will be required to return an instance of a strict subclass of int.
  • Support for __float__() method returning a strict subclass of float: these methods will be required to return an instance of float.
  • Support for __complex__() method returning a strict subclass of complex: these methods will be required to return an instance of complex.
  • Delegation of int() to __trunc__() method.
• calendar: calendar.January and calendar.February constants are deprecated and replaced by calendar.JANUARY and calendar.FEBRUARY. (Contributed by Prince Roshan in 103636.)
• datetime:
  • ~datetime.datetime.utcnow: use datetime.datetime.now(tz=datetime.UTC).
  • ~datetime.datetime.utcfromtimestamp: use datetime.datetime.fromtimestamp(timestamp, tz=datetime.UTC).
• gettext: Plural value must be an integer.
• importlib:
  • load_module() method: use exec_module() instead.
  • ~importlib.util.cache_from_source debug_override parameter is deprecated: use the optimization parameter instead.
• importlib.metadata:
  • EntryPoints tuple interface.
  • Implicit None on return values.
• importlib.resources: First parameter to files is renamed to 'anchor'.

• importlib.resources deprecated methods:

  • contents()
  • is_resource()
  • open_binary()
  • open_text()
  • path()
  • read_binary()
  • read_text()

  Use files() instead. Refer to importlib-resources: Migrating from Legacy for migration advice.

• locale.getdefaultlocale: use locale.setlocale(), locale.getencoding() and locale.getlocale() instead (90817)
• 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 91760.)
• ssl options and protocols:
  • ssl.SSLContext without protocol argument is deprecated.
  • ssl.SSLContext: ~ssl.SSLContext.set_npn_protocols and !~ssl.SSLContext.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
• !sre_compile, !sre_constants and !sre_parse modules.
• types.CodeType.co_lnotab: use the co_lines attribute instead.
• typing.Text (92332).
• sysconfig.is_python_build check_home parameter is deprecated and ignored.
• threading methods:
  • !threading.Condition.notifyAll: use ~threading.Condition.notify_all.
  • !threading.Event.isSet: use ~threading.Event.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.
• unittest.IsolatedAsyncioTestCase: it is deprecated to return a value that is not None from a test case.
• urllib.request: ~urllib.request.URLopener and ~urllib.request.FancyURLopener style of invoking requests is deprecated. Use newer ~urllib.request.urlopen functions and methods.
• !urllib.parse.to_bytes.
• urllib.parse deprecated functions: ~urllib.parse.urlparse instead
  • splitattr()
  • splithost()
  • splitnport()
  • splitpasswd()
  • splitport()
  • splitquery()
  • splittag()
  • splittype()
  • splituser()
  • splitvalue()
• wsgiref: SimpleHandler.stdout.write() should not do partial writes.
• zipimport.zipimporter.load_module is deprecated: use ~zipimport.zipimporter.exec_module instead.

Removed

• 594: Remove the !telnetlib module, deprecated in Python 3.11: use the projects telnetlib3 or Exscript instead. (Contributed by Victor Stinner in 104773.)
• Remove the 2to3 program and the !lib2to3 module, deprecated in Python 3.11. (Contributed by Victor Stinner in 104780.)
• Namespaces typing.io and typing.re, deprecated in Python 3.8, are now removed. The items in those namespaces can be imported directly from typing. (Contributed by Sebastian Rittau in 92871.)
• Remove the untested and undocumented webbrowser !MacOSX class, deprecated in Python 3.11. Use the !MacOSXOSAScript class (introduced in Python 3.2) instead. (Contributed by Hugo van Kemenade in 104804.)
• Remove support for using pathlib.Path objects as context managers. This functionality was deprecated and made a no-op in Python 3.9.
• Remove the undocumented !configparser.LegacyInterpolation class, deprecated in the docstring since Python 3.2, and with a deprecation warning since Python 3.11. (Contributed by Hugo van Kemenade in 104886.)
• Remove the !turtle.RawTurtle.settiltangle method, deprecated in docs since Python 3.1 and with a deprecation warning since Python 3.11. (Contributed by Hugo van Kemenade in 104876.)

• Removed the following unittest functions, deprecated in Python 3.11:

  • !unittest.findTestCases
  • !unittest.makeSuite
  • !unittest.getTestCaseNames

  Use ~unittest.TestLoader methods instead:

  • unittest.TestLoader.loadTestsFromModule
  • unittest.TestLoader.loadTestsFromTestCase
  • unittest.TestLoader.getTestCaseNames

  (Contributed by Hugo van Kemenade in 104835.)

• 594: Remove the !cgi and !cgitb modules, deprecated in Python 3.11.

  • cgi.FieldStorage can typically be replaced with urllib.parse.parse_qsl for GET and HEAD requests, and the email.message module or multipart PyPI project for POST and PUT.
  • cgi.parse() can be replaced by calling urllib.parse.parse_qs directly on the desired query string, except for multipart/form-data input, which can be handled as described for cgi.parse_multipart().
  • cgi.parse_multipart() can be replaced with the functionality in the email package (e.g. email.message.EmailMessage and email.message.Message) which implements the same MIME RFCs, or with the multipart PyPI project.

  • cgi.parse_header() can be replaced with the functionality in the email package, which implements the same MIME RFCs. For example, with email.message.EmailMessage:

    from email.message import EmailMessage
    msg = EmailMessage()
    msg['content-type'] = 'application/json; charset="utf8"'
    main, params = msg.get_content_type(), msg['content-type'].params

  (Contributed by Victor Stinner in 104773.)

• 594: Remove the !sndhdr module, deprecated in Python 3.11: use the projects filetype, puremagic, or python-magic instead. (Contributed by Victor Stinner in 104773.)
• 594: Remove the !pipes module, deprecated in Python 3.11: use the subprocess module instead. (Contributed by Victor Stinner in 104773.)
• 594: Remove the !ossaudiodev module, deprecated in Python 3.11: use the pygame project for audio playback. (Contributed by Victor Stinner in 104780.)
• 594: Remove the !sunau module, deprecated in Python 3.11. (Contributed by Victor Stinner in 104773.)
• 594: Remove the !mailcap module, deprecated in Python 3.11. The mimetypes module provides an alternative. (Contributed by Victor Stinner in 104773.)
• 594: Remove the !spwd module, deprecated in Python 3.11: the python-pam project can be used instead. (Contributed by Victor Stinner in 104773.)
• 594: Remove the !nntplib module, deprecated in Python 3.11: the PyPI nntplib project can be used instead. (Contributed by Victor Stinner in 104773.)
• 594: Remove the !nis module, deprecated in Python 3.11. (Contributed by Victor Stinner in 104773.)
• 594: Remove the !xdrlib module, deprecated in Python 3.11. (Contributed by Victor Stinner in 104773.)
• 594: Remove the !msilib module, deprecated in Python 3.11. (Contributed by Zachary Ware in 104773.)

• 594: Remove the !crypt module and its private !_crypt extension, deprecated in Python 3.11. The hashlib module is a potential replacement for certain use cases. Otherwise, the following PyPI projects can be used:

  • bcrypt: Modern password hashing for your software and your servers.
  • passlib: Comprehensive password hashing framework supporting over 30 schemes.
  • argon2-cffi: The secure Argon2 password hashing algorithm.
  • legacycrypt: Wrapper to the POSIX crypt library call and associated functionality.

  (Contributed by Victor Stinner in 104773.)

• 594: Remove the !uu module, deprecated in Python 3.11: the base64 module is a modern alternative. (Contributed by Victor Stinner in 104773.)
• 594: Remove the !aifc module, deprecated in Python 3.11. (Contributed by Victor Stinner in 104773.)
• 594: Remove the !audioop module, deprecated in Python 3.11. (Contributed by Victor Stinner in 104773.)
• 594: Remove the !chunk module, deprecated in Python 3.11. (Contributed by Victor Stinner in 104773.)
• Remove support for the keyword-argument method of creating typing.TypedDict types, deprecated in Python 3.11. (Contributed by Tomas Roun in 104786.)
• 594: Remove the !imghdr module, deprecated in Python 3.11: use the projects filetype, puremagic, or python-magic instead. (Contributed by Victor Stinner in 104773.)
• Remove the untested and undocumented !unittest.TestProgram.usageExit method, deprecated in Python 3.11. (Contributed by Hugo van Kemenade in 104992.)
• Remove the !tkinter.tix module, deprecated in Python 3.6. The third-party Tix library which the module wrapped is unmaintained. (Contributed by Zachary Ware in 75552.)
• Remove the old trashcan macros Py_TRASHCAN_SAFE_BEGIN and Py_TRASHCAN_SAFE_END. They should be replaced by the new macros Py_TRASHCAN_BEGIN and Py_TRASHCAN_END. The new macros were added in Python 3.8 and the old macros were deprecated in Python 3.11. (Contributed by Irit Katriel in 105111.)
• Remove locale.resetlocale() function deprecated in Python 3.11: use locale.setlocale(locale.LC_ALL, "") instead. (Contributed by Victor Stinner in 104783.)
• logging: Remove undocumented and untested Logger.warn() and LoggerAdapter.warn() methods and logging.warn() function. Deprecated since Python 3.3, they were aliases to the logging.Logger.warning method, !logging.LoggerAdapter.warning method and logging.warning function. (Contributed by Victor Stinner in 105376.)
• Remove cafile, capath and cadefault parameters of the urllib.request.urlopen function, deprecated in Python 3.6: use the context parameter instead. Please use ssl.SSLContext.load_cert_chain instead, or let ssl.create_default_context select the system's trusted CA certificates for you. (Contributed by Victor Stinner in 105382.)
• Remove deprecated webbrowser.MacOSXOSAScript._name attribute. Use webbrowser.MacOSXOSAScript.name <webbrowser.controller.name> attribute instead. (Contributed by Nikita Sobolev in 105546.)
• Remove undocumented, never working, and deprecated re.template function and re.TEMPLATE flag (and re.T alias). (Contributed by Serhiy Storchaka and Nikita Sobolev in 105687.)

Porting to Python 3.13

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

• The old trashcan macros Py_TRASHCAN_SAFE_BEGIN and Py_TRASHCAN_SAFE_END were removed. They should be replaced by the new macros Py_TRASHCAN_BEGIN and Py_TRASHCAN_END.

  A tp_dealloc function that has the old macros, such as:

  static void
  mytype_dealloc(mytype *p)
  {
      PyObject_GC_UnTrack(p);
      Py_TRASHCAN_SAFE_BEGIN(p);
      ...
      Py_TRASHCAN_SAFE_END
  }

  should migrate to the new macros as follows:

  static void
  mytype_dealloc(mytype *p)
  {
      PyObject_GC_UnTrack(p);
      Py_TRASHCAN_BEGIN(p, mytype_dealloc)
      ...
      Py_TRASHCAN_END
  }

  Note that Py_TRASHCAN_BEGIN has a second argument which should be the deallocation function it is in.

Build Changes

• Autoconf 2.71 and aclocal 1.16.4 is now required to regenerate the configure script. (Contributed by Christian Heimes in 89886.)
• SQLite 3.15.2 or newer is required to build the sqlite3 extension module. (Contributed by Erlend Aasland in 105875.)
• Python built with configure --with-trace-refs (tracing references) is now ABI compatible with Python release build and debug build <debug-build>. (Contributed by Victor Stinner in 108634.)
• Building CPython now requires a compiler with support for the C11 atomic library, GCC built-in atomic functions, or MSVC interlocked intrinsics.

C API Changes

New Features

• You no longer have to define the PY_SSIZE_T_CLEAN macro before including Python.h when using # formats in format codes <arg-parsing-string-and-buffers>. APIs accepting the format codes always use Py_ssize_t for # formats. (Contributed by Inada Naoki in 104922.)
• Add :cPyImport_AddModuleRef: similar to :cPyImport_AddModule, but return a strong reference instead of a borrowed reference. (Contributed by Victor Stinner in 105922.)
• Add :cPyWeakref_GetRef function: similar to :cPyWeakref_GetObject but returns a strong reference, or NULL if the referent is no longer live. (Contributed by Victor Stinner in 105927.)
• Add :cPyObject_GetOptionalAttr and :cPyObject_GetOptionalAttrString, variants of :cPyObject_GetAttr and :cPyObject_GetAttrString which don't raise AttributeError if the attribute is not found. These variants are more convenient and faster if the missing attribute should not be treated as a failure. (Contributed by Serhiy Storchaka in 106521.)
• Add :cPyMapping_GetOptionalItem and :cPyMapping_GetOptionalItemString: variants of :cPyObject_GetItem and :cPyMapping_GetItemString which don't raise KeyError if the key is not found. These variants are more convenient and faster if the missing key should not be treated as a failure. (Contributed by Serhiy Storchaka in 106307.)

• Add fixed variants of functions which silently ignore errors:

  • :cPyObject_HasAttrWithError replaces :cPyObject_HasAttr.
  • :cPyObject_HasAttrStringWithError replaces :cPyObject_HasAttrString.
  • :cPyMapping_HasKeyWithError replaces :cPyMapping_HasKey.
  • :cPyMapping_HasKeyStringWithError replaces :cPyMapping_HasKeyString.

  New functions return not only 1 for true and 0 for false, but also -1 for error.

  (Contributed by Serhiy Storchaka in 108511.)

• If Python is built in debug mode <debug-build> or with assertions <--with-assertions>, :cPyTuple_SET_ITEM and :cPyList_SET_ITEM now check the index argument with an assertion. If the assertion fails, make sure that the size is set before. (Contributed by Victor Stinner in 106168.)
• Add :cPyModule_Add function: similar to :cPyModule_AddObjectRef and :cPyModule_AddObject but always steals a reference to the value. (Contributed by Serhiy Storchaka in 86493.)
• Added :cPyDict_GetItemRef and :cPyDict_GetItemStringRef functions: similar to :cPyDict_GetItemWithError but returning a strong reference instead of a borrowed reference. Moreover, these functions return -1 on error and so checking PyErr_Occurred() is not needed. (Contributed by Victor Stinner in 106004.)
• Added :cPyDict_ContainsString function: same as :cPyDict_Contains, but key is specified as a :cconst char* UTF-8 encoded bytes string, rather than a :cPyObject*. (Contributed by Victor Stinner in 108314.)
• Add :cPy_IsFinalizing function: check if the main Python interpreter is shutting down <interpreter shutdown>. (Contributed by Victor Stinner in 108014.)
• Add :cPyLong_AsInt function: similar to :cPyLong_AsLong, but store the result in a C :cint instead of a C :clong. Previously, it was known as the private function :c!_PyLong_AsInt (with an underscore prefix). (Contributed by Victor Stinner in 108014.)
• Python built with configure --with-trace-refs (tracing references) now supports the Limited API <limited-c-api>. (Contributed by Victor Stinner in 108634.)

Porting to Python 3.13

• Python.h no longer includes the <ieeefp.h> standard header. It was included for the finite() function which is now provided by the <math.h> header. It should now be included explicitly if needed. Remove also the HAVE_IEEEFP_H macro. (Contributed by Victor Stinner in 108765.)
• Python.h no longer includes the <unistd.h> standard header file. If needed, it should now be included explicitly. For example, it provides the functions: close(), getpagesize(), getpid() and sysconf(). (Contributed by Victor Stinner in 108765.)
• Python.h no longer includes these standard header files: <time.h>, <sys/select.h> and <sys/time.h>. If needed, they should now be included explicitly. For example, <time.h> provides the clock() and gmtime() functions, <sys/select.h> provides the select() function, and <sys/time.h> provides the futimes(), gettimeofday() and setitimer() functions. (Contributed by Victor Stinner in 108765.)
• Python.h no longer includes the <ctype.h> standard header file. If needed, it should now be included explicitly. For example, it provides isalpha() and tolower() functions which are locale dependent. Python provides locale independent functions, like :c!Py_ISALPHA and :c!Py_TOLOWER. (Contributed by Victor Stinner in 108765.)

Deprecated

• Passing optional arguments maxsplit, count and flags in module-level functions re.split, re.sub and re.subn as positional arguments is now deprecated. In future Python versions these parameters will be keyword-only <keyword-only_parameter>. (Contributed by Serhiy Storchaka in 56166.)
• Deprecate the old Py_UNICODE and PY_UNICODE_TYPE types: use directly the :cwchar_t type instead. Since Python 3.3, Py_UNICODE and PY_UNICODE_TYPE are just aliases to :cwchar_t. (Contributed by Victor Stinner in 105156.)

• Deprecate old Python initialization functions:

  • :cPySys_ResetWarnOptions: clear sys.warnoptions and !warnings.filters instead.
  • :cPy_GetExecPrefix: get sys.exec_prefix instead.
  • :cPy_GetPath: get sys.path instead.
  • :cPy_GetPrefix: get sys.prefix instead.
  • :cPy_GetProgramFullPath: get sys.executable instead.
  • :cPy_GetProgramName: get sys.executable instead.
  • :cPy_GetPythonHome: get :cPyConfig.home or PYTHONHOME environment variable instead.

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

• Deprecate the :cPyImport_ImportModuleNoBlock function which is just an alias to :cPyImport_ImportModule since Python 3.3. Scheduled for removal in Python 3.15. (Contributed by Victor Stinner in 105396.)
• Deprecate the :cPyWeakref_GetObject and :cPyWeakref_GET_OBJECT functions, which return a borrowed reference: use the new :cPyWeakref_GetRef function instead, it returns a strong reference. The pythoncapi-compat project can be used to get :cPyWeakref_GetRef on Python 3.12 and older. (Contributed by Victor Stinner in 105927.)

Removed

• Remove many APIs (functions, macros, variables) with names prefixed by _Py or _PY (considered as private API). If your project is affected by one of these removals and you consider that the removed API should remain available, please open a new issue to request a public C API and add cc @vstinner to the issue to notify Victor Stinner. (Contributed by Victor Stinner in 106320.)

• Remove functions deprecated in Python 3.9.

  • PyEval_CallObject(), PyEval_CallObjectWithKeywords(): use :cPyObject_CallNoArgs or :cPyObject_Call instead. Warning: :cPyObject_Call positional arguments must be a tuple and must not be NULL, keyword arguments must be a dict or NULL, whereas removed functions checked arguments type and accepted NULL positional and keyword arguments. To replace PyEval_CallObjectWithKeywords(func, NULL, kwargs) with :cPyObject_Call, pass an empty tuple as positional arguments using :cPyTuple_New(0) <PyTuple_New>.
  • PyEval_CallFunction(): use :cPyObject_CallFunction instead.
  • PyEval_CallMethod(): use :cPyObject_CallMethod instead.
  • PyCFunction_Call(): use :cPyObject_Call instead.

  (Contributed by Victor Stinner in 105107.)

• Remove old buffer protocols deprecated in Python 3.0. Use bufferobjects instead.

  • :c!PyObject_CheckReadBuffer: Use :cPyObject_CheckBuffer to test if the object supports the buffer protocol. Note that :cPyObject_CheckBuffer doesn't guarantee that :cPyObject_GetBuffer will succeed. To test if the object is actually readable, see the next example of :cPyObject_GetBuffer.

  • :c!PyObject_AsCharBuffer, :c!PyObject_AsReadBuffer: :cPyObject_GetBuffer and :cPyBuffer_Release instead:

    Py_buffer view;
    if (PyObject_GetBuffer(obj, &view, PyBUF_SIMPLE) < 0) {
        return NULL;
    }
    // Use `view.buf` and `view.len` to read from the buffer.
    // You may need to cast buf as `(const char*)view.buf`.
    PyBuffer_Release(&view);

  • :c!PyObject_AsWriteBuffer: Use :cPyObject_GetBuffer and :cPyBuffer_Release instead:

    Py_buffer view;
    if (PyObject_GetBuffer(obj, &view, PyBUF_WRITABLE) < 0) {
        return NULL;
    }
    // Use `view.buf` and `view.len` to write to the buffer.
    PyBuffer_Release(&view);

  (Contributed by Inada Naoki in 85275.)

• Remove the following old functions to configure the Python initialization, deprecated in Python 3.11:

  • PySys_AddWarnOptionUnicode(): use :cPyConfig.warnoptions instead.
  • PySys_AddWarnOption(): use :cPyConfig.warnoptions instead.
  • PySys_AddXOption(): use :cPyConfig.xoptions instead.
  • PySys_HasWarnOptions(): use :cPyConfig.xoptions instead.
  • PySys_SetArgvEx(): set :cPyConfig.argv instead.
  • PySys_SetArgv(): set :cPyConfig.argv instead.
  • PySys_SetPath(): set :cPyConfig.module_search_paths instead.
  • Py_SetPath(): set :cPyConfig.module_search_paths instead.
  • Py_SetProgramName(): set :cPyConfig.program_name instead.
  • Py_SetPythonHome(): set :cPyConfig.home instead.
  • Py_SetStandardStreamEncoding(): set :cPyConfig.stdio_encoding instead, and set also maybe :cPyConfig.legacy_windows_stdio (on Windows).
  • _Py_SetProgramFullPath(): set :cPyConfig.executable instead.

  Use the new :cPyConfig API of the Python Initialization Configuration <init-config> instead (587), added to Python 3.8. (Contributed by Victor Stinner in 105145.)

• Remove PyEval_InitThreads() and PyEval_ThreadsInitialized() functions, deprecated in Python 3.9. Since Python 3.7, Py_Initialize() always creates the GIL: calling PyEval_InitThreads() did nothing and PyEval_ThreadsInitialized() always returned non-zero. (Contributed by Victor Stinner in 105182.)

• Remove PyEval_AcquireLock() and PyEval_ReleaseLock() functions, deprecated in Python 3.2. They didn't update the current thread state. They can be replaced with:

  • :cPyEval_SaveThread and :cPyEval_RestoreThread;
  • low-level :cPyEval_AcquireThread and :cPyEval_RestoreThread;
  • or :cPyGILState_Ensure and :cPyGILState_Release.

  (Contributed by Victor Stinner in 105182.)

• Remove the old aliases to functions calling functions which were kept for backward compatibility with Python 3.8 provisional API:

  • _PyObject_CallMethodNoArgs(): use PyObject_CallMethodNoArgs()
  • _PyObject_CallMethodOneArg(): use PyObject_CallMethodOneArg()
  • _PyObject_CallOneArg(): use PyObject_CallOneArg()
  • _PyObject_FastCallDict(): use PyObject_VectorcallDict()
  • _PyObject_Vectorcall(): use PyObject_Vectorcall()
  • _PyObject_VectorcallMethod(): use PyObject_VectorcallMethod()
  • _PyVectorcall_Function(): use PyVectorcall_Function()

  Just remove the underscore prefix to update your code. (Contributed by Victor Stinner in 106084.)

• Remove private _PyObject_FastCall() function: use PyObject_Vectorcall() which is available since Python 3.8 (590). (Contributed by Victor Stinner in 106023.)
• Remove cpython/pytime.h header file: it only contained private functions. (Contributed by Victor Stinner in 106316.)
• Remove _PyInterpreterState_Get() alias to :cPyInterpreterState_Get() which was kept for backward compatibility with Python 3.8. The pythoncapi-compat project can be used to get :cPyInterpreterState_Get() on Python 3.8 and older. (Contributed by Victor Stinner in 106320.)
• The :cPyModule_AddObject function is now soft deprecated: :cPyModule_Add or :cPyModule_AddObjectRef functions should be used instead. (Contributed by Serhiy Storchaka in 86493.)

Pending Removal in Python 3.14

• Creating immutable types (:cPy_TPFLAGS_IMMUTABLETYPE) with mutable bases using the C API.

• Global configuration variables:

  • :cPy_DebugFlag: use :cPyConfig.parser_debug
  • :cPy_VerboseFlag: use :cPyConfig.verbose
  • :cPy_QuietFlag: use :cPyConfig.quiet
  • :cPy_InteractiveFlag: use :cPyConfig.interactive
  • :cPy_InspectFlag: use :cPyConfig.inspect
  • :cPy_OptimizeFlag: use :cPyConfig.optimization_level
  • :cPy_NoSiteFlag: use :cPyConfig.site_import
  • :cPy_BytesWarningFlag: use :cPyConfig.bytes_warning
  • :cPy_FrozenFlag: use :cPyConfig.pathconfig_warnings
  • :cPy_IgnoreEnvironmentFlag: use :cPyConfig.use_environment
  • :cPy_DontWriteBytecodeFlag: use :cPyConfig.write_bytecode
  • :cPy_NoUserSiteDirectory: use :cPyConfig.user_site_directory
  • :cPy_UnbufferedStdioFlag: use :cPyConfig.buffered_stdio
  • :cPy_HashRandomizationFlag: use :cPyConfig.use_hash_seed and :cPyConfig.hash_seed
  • :cPy_IsolatedFlag: use :cPyConfig.isolated
  • :cPy_LegacyWindowsFSEncodingFlag: use :cPyPreConfig.legacy_windows_fs_encoding
  • :cPy_LegacyWindowsStdioFlag: use :cPyConfig.legacy_windows_stdio
  • :c!Py_FileSystemDefaultEncoding: use :cPyConfig.filesystem_encoding
  • :c!Py_HasFileSystemDefaultEncoding: use :cPyConfig.filesystem_encoding
  • :c!Py_FileSystemDefaultEncodeErrors: use :cPyConfig.filesystem_errors
  • :c!Py_UTF8Mode: use :cPyPreConfig.utf8_mode (see :cPy_PreInitialize)

  The :cPy_InitializeFromConfig API should be used with :cPyConfig instead.

Pending Removal in Python 3.15

• :cPyImport_ImportModuleNoBlock: use :cPyImport_ImportModule.
• :cPyWeakref_GET_OBJECT: use :cPyWeakref_GetRef instead.
• :cPyWeakref_GetObject: use :cPyWeakref_GetRef instead.
• :c!Py_UNICODE_WIDE type: use :cwchar_t instead.
• :cPy_UNICODE type: use :cwchar_t instead.
• Python initialization functions:
  • :cPySys_ResetWarnOptions: clear sys.warnoptions and !warnings.filters instead.
  • :cPy_GetExecPrefix: get sys.exec_prefix instead.
  • :cPy_GetPath: get sys.path instead.
  • :cPy_GetPrefix: get sys.prefix instead.
  • :cPy_GetProgramFullPath: get sys.executable instead.
  • :cPy_GetProgramName: get sys.executable instead.
  • :cPy_GetPythonHome: get :cPyConfig.home or PYTHONHOME environment variable instead.

Pending Removal in Future Versions

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

• :cPy_TPFLAGS_HAVE_FINALIZE: no needed since Python 3.8.
• :cPyErr_Fetch: use :cPyErr_GetRaisedException.
• :cPyErr_NormalizeException: use :cPyErr_GetRaisedException.
• :cPyErr_Restore: use :cPyErr_SetRaisedException.
• :cPyModule_GetFilename: use :cPyModule_GetFilenameObject.
• :cPyOS_AfterFork: use :cPyOS_AfterFork_Child().
• :cPySlice_GetIndicesEx.
• :c!PyUnicode_AsDecodedObject.
• :c!PyUnicode_AsDecodedUnicode.
• :c!PyUnicode_AsEncodedObject.
• :c!PyUnicode_AsEncodedUnicode.
• :cPyUnicode_READY: not needed since Python 3.12.
• :c!_PyErr_ChainExceptions.
• :c!PyBytesObject.ob_shash member: call :cPyObject_Hash instead.
• :c!PyDictObject.ma_version_tag member.
• TLS API:
  • :cPyThread_create_key: use :cPyThread_tss_alloc.
  • :cPyThread_delete_key: use :cPyThread_tss_free.
  • :cPyThread_set_key_value: use :cPyThread_tss_set.
  • :cPyThread_get_key_value: use :cPyThread_tss_get.
  • :cPyThread_delete_key_value: use :cPyThread_tss_delete.
  • :cPyThread_ReInitTLS: no longer needed.