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.

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 gh-106487.)

• Compiler now strip indents from docstrings. This will reduce the size of bytecode cache (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 gh-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 gh-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 gh-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 gh-80480.)

copy

• Add copy.replace() function which allows to create a modified copy of an object, which is especially useful for immutable objects. It supports named tuples created with the factory function collections.namedtuple(), dataclass instances, various datetime objects, Signature objects, Parameter objects, code object, and any user classes which define the __replace__() method. (Contributed by Serhiy Storchaka in gh-108751.)

dbm

• Add dbm.gnu.gdbm.clear() and dbm.ndbm.ndbm.clear() methods that remove all items from the database. (Contributed by Donghee Na in gh-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 gh-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 or on Python built on debug mode. (Contributed by Victor Stinner in gh-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 gh-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 gh-89812.)

• Add support for recursive wildcards in pathlib.PurePath.match(). (Contributed by Barney Gale in gh-73435.)

• Add follow_symlinks keyword-only argument to pathlib.Path.glob(), rglob(), is_file(), and is_dir(). (Contributed by Barney Gale in gh-77609 and gh-105793.)

pdb

• Add ability to move between chained exceptions during post mortem debugging in pm() using the new exceptions [exc_number] command for Pdb. (Contributed by Matthias Bussonnier in gh-106676.)

• Expressions/Statements whose prefix is a pdb command are now correctly identified and executed. (Contributed by Tian Gao in gh-108464.)

sqlite3

• A ResourceWarning is now emitted if a sqlite3.Connection object is not closed explicitly. (Contributed by Erlend E. Aasland in gh-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 gh-72684.)

traceback

• Add show_group parameter to traceback.TracebackException.format_exception_only() to format the nested exceptions of a BaseExceptionGroup instance, recursively. (Contributed by Irit Katriel in gh-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 gh-104873.)

venv

• Add support for adding source control management (SCM) ignore files to a virtual environment’s directory. By default, Git is supported. This is implemented as opt-in via the API which can be extended to support other SCMs (venv.EnvBuilder and venv.create()), and opt-out via the CLI (using --without-scm-ignore-files). (Contributed by Brett Cannon in gh-108125.)

Optimizations

• textwrap.indent() is now ~30% faster than before for large input. (Contributed by Inada Naoki in gh-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 gh-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 gh-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 gh-106535.)

• http.server: http.server.CGIHTTPRequestHandler now emits a DeprecationWarning as it will be removed in 3.15. Process based CGI http servers have been out of favor for a very long time. This code was outdated, unmaintained, and rarely used. It has a high potential for both security and functionality bugs. This includes removal of the --cgi flag to the python -m http.server command line in 3.15.

• 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 gh-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 gh-105566 and gh-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 gh-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 instead. (Contributed by Michael The in gh-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 gh-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:

  • create_function()

  • create_aggregate()

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

  • set_authorizer()

  • set_progress_handler()

  • set_trace_callback()

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

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

• The dis.HAVE_ARGUMENT separator is deprecated. Check membership in hasarg instead. (Contributed by Irit Katriel in gh-109319.)

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 gh-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 gh-90953.)

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

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

• importlib: __package__ and __cached__ will cease to be set or taken into consideration by the import system (gh-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 gh-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 gh-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 (gh-84559). Adding a runtime warning about this was deemed too disruptive as the majority of code is not expected to care. Use the get_context() or set_start_method() APIs to explicitly specify when your code requires 'fork'. See Contexts and start methods.

• pathlib: is_relative_to(), 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 gh-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:

  • version and version_info.

  • execute() and executemany() if named 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 PEP 626 since 3.10 and was planned to be removed in 3.12, but it only got a proper DeprecationWarning in 3.12. May be removed in 3.14. (Contributed by Nikita Sobolev in gh-101866.)

• 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 gh-88168.)

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

Pending Removal in Python 3.15

• http.server.CGIHTTPRequestHandler will be removed along with its related --cgi flag to python -m http.server. It was obsolete and rarely used. No direct replacement exists. Anything is better than CGI to interface a web server with a request handler.

• 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 gh-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 gh-102029.)

Pending Removal in Python 3.16

• array.array 'u' type (wchar_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. (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.

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

• 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.

• 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 (gh-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 gh-91760.)

• ssl options and protocols:

  • ssl.SSLContext without protocol argument is deprecated.

  • 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 (gh-92332).

• 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().

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

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

• urllib.parse.to_bytes().

• urllib.parse deprecated functions: 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 exec_module() instead.

Removed

• PEP 594: Remove the telnetlib module, deprecated in Python 3.11: use the projects telnetlib3 or Exscript instead. (Contributed by Victor Stinner in gh-104773.)

• Remove the 2to3 program and the lib2to3 module, deprecated in Python 3.11. (Contributed by Victor Stinner in gh-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 gh-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 gh-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 gh-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 gh-104876.)

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

  • unittest.findTestCases()

  • unittest.makeSuite()

  • unittest.getTestCaseNames()

  Use TestLoader methods instead:

  • unittest.TestLoader.loadTestsFromModule()

  • unittest.TestLoader.loadTestsFromTestCase()

  • unittest.TestLoader.getTestCaseNames()

  (Contributed by Hugo van Kemenade in gh-104835.)

• PEP 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 gh-104773.)

• PEP 594: Remove the sndhdr module, deprecated in Python 3.11: use the projects filetype, puremagic, or python-magic instead. (Contributed by Victor Stinner in gh-104773.)

• PEP 594: Remove the pipes module, deprecated in Python 3.11: use the subprocess module instead. (Contributed by Victor Stinner in gh-104773.)

• PEP 594: Remove the ossaudiodev module, deprecated in Python 3.11: use the pygame project for audio playback. (Contributed by Victor Stinner in gh-104780.)

• PEP 594: Remove the sunau module, deprecated in Python 3.11. (Contributed by Victor Stinner in gh-104773.)

• PEP 594: Remove the mailcap module, deprecated in Python 3.11. The mimetypes module provides an alternative. (Contributed by Victor Stinner in gh-104773.)

• PEP 594: Remove the spwd module, deprecated in Python 3.11: the python-pam project can be used instead. (Contributed by Victor Stinner in gh-104773.)

• PEP 594: Remove the nntplib module, deprecated in Python 3.11: the PyPI nntplib project can be used instead. (Contributed by Victor Stinner in gh-104773.)

• PEP 594: Remove the nis module, deprecated in Python 3.11. (Contributed by Victor Stinner in gh-104773.)

• PEP 594: Remove the xdrlib module, deprecated in Python 3.11. (Contributed by Victor Stinner in gh-104773.)

• PEP 594: Remove the msilib module, deprecated in Python 3.11. (Contributed by Zachary Ware in gh-104773.)

• PEP 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 gh-104773.)

• PEP 594: Remove the uu module, deprecated in Python 3.11: the base64 module is a modern alternative. (Contributed by Victor Stinner in gh-104773.)

• PEP 594: Remove the aifc module, deprecated in Python 3.11. (Contributed by Victor Stinner in gh-104773.)

• PEP 594: Remove the audioop module, deprecated in Python 3.11. (Contributed by Victor Stinner in gh-104773.)

• PEP 594: Remove the chunk module, deprecated in Python 3.11. (Contributed by Victor Stinner in gh-104773.)

• Remove support for the keyword-argument method of creating typing.TypedDict types, deprecated in Python 3.11. (Contributed by Tomas Roun in gh-104786.)

• PEP 594: Remove the imghdr module, deprecated in Python 3.11: use the projects filetype, puremagic, or python-magic instead. (Contributed by Victor Stinner in gh-104773.)

• Remove the untested and undocumented unittest.TestProgram.usageExit() method, deprecated in Python 3.11. (Contributed by Hugo van Kemenade in gh-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 gh-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 gh-105111.)

• Remove locale.resetlocale() function deprecated in Python 3.11: use locale.setlocale(locale.LC_ALL, "") instead. (Contributed by Victor Stinner in gh-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 gh-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 gh-105382.)

• Remove deprecated webbrowser.MacOSXOSAScript._name attribute. Use webbrowser.MacOSXOSAScript.name attribute instead. (Contributed by Nikita Sobolev in gh-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 gh-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 gh-89886.)

• SQLite 3.15.2 or newer is required to build the sqlite3 extension module. (Contributed by Erlend Aasland in gh-105875.)

• Python built with configure --with-trace-refs (tracing references) is now ABI compatible with Python release build and debug build. (Contributed by Victor Stinner in gh-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. APIs accepting the format codes always use Py_ssize_t for # formats. (Contributed by Inada Naoki in gh-104922.)

• Add PyImport_AddModuleRef(): similar to PyImport_AddModule(), but return a strong reference instead of a borrowed reference. (Contributed by Victor Stinner in gh-105922.)

• Add PyWeakref_GetRef() function: similar to PyWeakref_GetObject() but returns a strong reference, or NULL if the referent is no longer live. (Contributed by Victor Stinner in gh-105927.)

• Add PyObject_GetOptionalAttr() and PyObject_GetOptionalAttrString(), variants of PyObject_GetAttr() and PyObject_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 gh-106521.)

• Add PyMapping_GetOptionalItem() and PyMapping_GetOptionalItemString(): variants of PyObject_GetItem() and PyMapping_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 gh-106307.)

• Add fixed variants of functions which silently ignore errors:

  • PyObject_HasAttrWithError() replaces PyObject_HasAttr().

  • PyObject_HasAttrStringWithError() replaces PyObject_HasAttrString().

  • PyMapping_HasKeyWithError() replaces PyMapping_HasKey().

  • PyMapping_HasKeyStringWithError() replaces PyMapping_HasKeyString().

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

  (Contributed by Serhiy Storchaka in gh-108511.)

• If Python is built in debug mode or with assertions, PyTuple_SET_ITEM() and PyList_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 gh-106168.)

• Add PyModule_Add() function: similar to PyModule_AddObjectRef() and PyModule_AddObject() but always steals a reference to the value. (Contributed by Serhiy Storchaka in gh-86493.)

• Added PyDict_GetItemRef() and PyDict_GetItemStringRef() functions: similar to PyDict_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 gh-106004.)

• Added PyDict_ContainsString() function: same as PyDict_Contains(), but key is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*. (Contributed by Victor Stinner in gh-108314.)

• Add Py_IsFinalizing() function: check if the main Python interpreter is shutting down. (Contributed by Victor Stinner in gh-108014.)

• Add PyLong_AsInt() function: similar to PyLong_AsLong(), but store the result in a C int instead of a C long. Previously, it was known as the private function _PyLong_AsInt() (with an underscore prefix). (Contributed by Victor Stinner in gh-108014.)

• Python built with configure --with-trace-refs (tracing references) now supports the Limited API. (Contributed by Victor Stinner in gh-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 gh-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 gh-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 gh-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 Py_ISALPHA() and Py_TOLOWER(). (Contributed by Victor Stinner in gh-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. (Contributed by Serhiy Storchaka in gh-56166.)

• Deprecate the old Py_UNICODE and PY_UNICODE_TYPE types: use directly the wchar_t type instead. Since Python 3.3, Py_UNICODE and PY_UNICODE_TYPE are just aliases to wchar_t. (Contributed by Victor Stinner in gh-105156.)

• Deprecate old 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 PYTHONHOME environment variable instead.

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

• Deprecate the PyImport_ImportModuleNoBlock() function which is just an alias to PyImport_ImportModule() since Python 3.3. Scheduled for removal in Python 3.15. (Contributed by Victor Stinner in gh-105396.)

• Deprecate the PyWeakref_GetObject() and PyWeakref_GET_OBJECT() functions, which return a borrowed reference: use the new PyWeakref_GetRef() function instead, it returns a strong reference. The pythoncapi-compat project can be used to get PyWeakref_GetRef() on Python 3.12 and older. (Contributed by Victor Stinner in gh-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 gh-106320.)

• Remove functions deprecated in Python 3.9.

  • PyEval_CallObject(), PyEval_CallObjectWithKeywords(): use PyObject_CallNoArgs() or PyObject_Call() instead. Warning: PyObject_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 PyObject_Call(), pass an empty tuple as positional arguments using PyTuple_New(0).

  • PyEval_CallFunction(): use PyObject_CallFunction() instead.

  • PyEval_CallMethod(): use PyObject_CallMethod() instead.

  • PyCFunction_Call(): use PyObject_Call() instead.

  (Contributed by Victor Stinner in gh-105107.)

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

  • PyObject_CheckReadBuffer(): Use PyObject_CheckBuffer() to test if the object supports the buffer protocol. Note that PyObject_CheckBuffer() doesn’t guarantee that PyObject_GetBuffer() will succeed. To test if the object is actually readable, see the next example of PyObject_GetBuffer().

  • PyObject_AsCharBuffer(), PyObject_AsReadBuffer(): PyObject_GetBuffer() and PyBuffer_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);
    

  • PyObject_AsWriteBuffer(): Use PyObject_GetBuffer() and PyBuffer_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 gh-85275.)

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

  • PySys_AddWarnOptionUnicode(): use PyConfig.warnoptions instead.

  • PySys_AddWarnOption(): use PyConfig.warnoptions instead.

  • PySys_AddXOption(): use PyConfig.xoptions instead.

  • PySys_HasWarnOptions(): use PyConfig.xoptions instead.

  • PySys_SetArgvEx(): set PyConfig.argv instead.

  • PySys_SetArgv(): set PyConfig.argv instead.

  • PySys_SetPath(): set PyConfig.module_search_paths instead.

  • Py_SetPath(): set PyConfig.module_search_paths instead.

  • Py_SetProgramName(): set PyConfig.program_name instead.

  • Py_SetPythonHome(): set PyConfig.home instead.

  • Py_SetStandardStreamEncoding(): set PyConfig.stdio_encoding instead, and set also maybe PyConfig.legacy_windows_stdio (on Windows).

  • _Py_SetProgramFullPath(): set PyConfig.executable instead.

  Use the new PyConfig API of the Python Initialization Configuration instead (PEP 587), added to Python 3.8. (Contributed by Victor Stinner in gh-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 gh-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:

  • PyEval_SaveThread() and PyEval_RestoreThread();

  • low-level PyEval_AcquireThread() and PyEval_RestoreThread();

  • or PyGILState_Ensure() and PyGILState_Release().

  (Contributed by Victor Stinner in gh-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 gh-106084.)

• Remove private _PyObject_FastCall() function: use PyObject_Vectorcall() which is available since Python 3.8 (PEP 590). (Contributed by Victor Stinner in gh-106023.)

• Remove cpython/pytime.h header file: it only contained private functions. (Contributed by Victor Stinner in gh-106316.)

• Remove _PyInterpreterState_Get() alias to PyInterpreterState_Get() which was kept for backward compatibility with Python 3.8. The pythoncapi-compat project can be used to get PyInterpreterState_Get() on Python 3.8 and older. (Contributed by Victor Stinner in gh-106320.)

• The PyModule_AddObject() function is now soft deprecated: PyModule_Add() or PyModule_AddObjectRef() functions should be used instead. (Contributed by Serhiy Storchaka in gh-86493.)

Pending Removal in Python 3.14

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

• Global configuration variables:

  • Py_DebugFlag: use PyConfig.parser_debug

  • Py_VerboseFlag: use PyConfig.verbose

  • Py_QuietFlag: use PyConfig.quiet

  • Py_InteractiveFlag: use PyConfig.interactive

  • Py_InspectFlag: use PyConfig.inspect

  • Py_OptimizeFlag: use PyConfig.optimization_level

  • Py_NoSiteFlag: use PyConfig.site_import

  • Py_BytesWarningFlag: use PyConfig.bytes_warning

  • Py_FrozenFlag: use PyConfig.pathconfig_warnings

  • Py_IgnoreEnvironmentFlag: use PyConfig.use_environment

  • Py_DontWriteBytecodeFlag: use PyConfig.write_bytecode

  • Py_NoUserSiteDirectory: use PyConfig.user_site_directory

  • Py_UnbufferedStdioFlag: use PyConfig.buffered_stdio

  • Py_HashRandomizationFlag: use PyConfig.use_hash_seed and PyConfig.hash_seed

  • Py_IsolatedFlag: use PyConfig.isolated

  • Py_LegacyWindowsFSEncodingFlag: use PyPreConfig.legacy_windows_fs_encoding

  • Py_LegacyWindowsStdioFlag: use PyConfig.legacy_windows_stdio

  • Py_FileSystemDefaultEncoding: use PyConfig.filesystem_encoding

  • Py_HasFileSystemDefaultEncoding: use PyConfig.filesystem_encoding

  • Py_FileSystemDefaultEncodeErrors: use PyConfig.filesystem_errors

  • Py_UTF8Mode: use PyPreConfig.utf8_mode (see Py_PreInitialize())

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

Pending Removal in Python 3.15

• PyImport_ImportModuleNoBlock(): use PyImport_ImportModule().

• PyWeakref_GET_OBJECT(): use PyWeakref_GetRef() instead.

• PyWeakref_GetObject(): use PyWeakref_GetRef() instead.

• Py_UNICODE_WIDE type: use wchar_t instead.

• Py_UNICODE type: 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 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.

• Py_TPFLAGS_HAVE_FINALIZE: no needed since Python 3.8.

• PyErr_Fetch(): use PyErr_GetRaisedException().

• PyErr_NormalizeException(): use PyErr_GetRaisedException().

• PyErr_Restore(): use PyErr_SetRaisedException().

• PyModule_GetFilename(): use PyModule_GetFilenameObject().

• PyOS_AfterFork(): use PyOS_AfterFork_Child().

• PySlice_GetIndicesEx().

• PyUnicode_AsDecodedObject().

• PyUnicode_AsDecodedUnicode().

• PyUnicode_AsEncodedObject().

• PyUnicode_AsEncodedUnicode().

• PyUnicode_READY(): not needed since Python 3.12.

• _PyErr_ChainExceptions().

• PyBytesObject.ob_shash member: call PyObject_Hash() instead.

• PyDictObject.ma_version_tag member.

• TLS API:

  • PyThread_create_key(): use PyThread_tss_alloc().

  • PyThread_delete_key(): use PyThread_tss_free().

  • PyThread_set_key_value(): use PyThread_tss_set().

  • PyThread_get_key_value(): use PyThread_tss_get().

  • PyThread_delete_key_value(): use PyThread_tss_delete().

  • PyThread_ReInitTLS(): no longer needed.