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

Important deprecations, removals or restrictions:

  • PEP 594: The remaining 19 “dead batteries” have been removed from the standard library: aifc, audioop, cgi, cgitb, chunk, crypt, imghdr, mailcap, msilib, nis, nntplib, ossaudiodev, pipes, sndhdr, spwd, sunau, telnetlib, uu and xdrlib.

  • PEP 602 (“Annual Release Cycle for Python”) has been updated:

    • Python 3.9 - 3.12 have one and a half years of full support, followed by three and a half years of security fixes.

    • Python 3.13 and later have two years of full support, followed by three years of security fixes.

Interpreter improvements:

  • A basic JIT compiler was added. It is currently disabled by default (though we may turn it on later). Performance improvements are modest – we expect to be improving this over the next few releases.

New Features

Improved Error Messages

  • The interpreter now colorizes error messages when displaying tracebacks by default. This feature can be controlled via the new PYTHON_COLORS environment variable as well as the canonical NO_COLOR and FORCE_COLOR environment variables. See also Controlling color. (Contributed by Pablo Galindo Salgado in gh-112730.)

  • When an incorrect keyword argument is passed to a function, the error message now potentially suggests the correct keyword argument. (Contributed by Pablo Galindo Salgado and Shantanu Jain in gh-107944.)

    >>> "better error messages!".split(max_split=1)
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
        "better error messages!".split(max_split=1)
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
    TypeError: split() got an unexpected keyword argument 'max_split'. Did you mean 'maxsplit'?
    

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).

  • multiprocessing, concurrent.futures, compileall: Replace os.cpu_count() with os.process_cpu_count() to select the default number of worker threads and processes. Get the CPU affinity if supported. (Contributed by Victor Stinner in gh-109649.)

  • os.path.realpath() now resolves MS-DOS style file names even if the file is not accessible. (Contributed by Moonsik Park in gh-82367.)

  • Fixed a bug where a global declaration in an except block is rejected when the global is used in the else block. (Contributed by Irit Katriel in gh-111123.)

  • Many functions now emit a warning if a boolean value is passed as a file descriptor argument. This can help catch some errors earlier. (Contributed by Serhiy Storchaka in gh-82626.)

  • Added a new environment variable PYTHON_FROZEN_MODULES. It determines whether or not frozen modules are ignored by the import machinery, equivalent of the -X frozen_modules command-line option. (Contributed by Yilei Yang in gh-111374.)

  • The new PYTHON_HISTORY environment variable can be used to change the location of a .python_history file. (Contributed by Levi Sabah, Zackery Spytz and Hugo van Kemenade in gh-73965.)

  • Add PythonFinalizationError exception. This exception derived from RuntimeError is raised when an operation is blocked during the Python finalization.

    The following functions now raise PythonFinalizationError, instead of RuntimeError:

    (Contributed by Victor Stinner in gh-114570.)

New Modules

  • None yet.

Improved Modules

argparse

  • Add parameter deprecated in methods add_argument() and add_parser() which allows to deprecate command-line options, positional arguments and subcommands. (Contributed by Serhiy Storchaka in gh-83648).

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.)

  • Add clear() method in order to implement MutableSequence. (Contributed by Mike Zimin in gh-114894.)

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.)

asyncio

copy

dbm

dis

  • Change the output of dis module functions to show logical labels for jump targets and exception handlers, rather than offsets. The offsets can be added with the new -O command line option or the show_offsets parameter. (Contributed by Irit Katriel in gh-112137.)

dbm

doctest

email

  • email.utils.getaddresses() and email.utils.parseaddr() now return ('', '') 2-tuples in more situations where invalid email addresses are encountered instead of potentially inaccurate values. Add optional strict parameter to these two functions: use strict=False to get the old behavior, accept malformed inputs. getattr(email.utils, 'supports_strict_parsing', False) can be use to check if the strict parameter is available. (Contributed by Thomas Dwyer and Victor Stinner for gh-102988 to improve the CVE-2023-27043 fix.)

fractions

  • Formatting for objects of type fractions.Fraction now supports the standard format specification mini-language rules for fill, alignment, sign handling, minimum width and grouping. (Contributed by Mark Dickinson in gh-111320.)

glob

  • Add glob.translate() function that converts a path specification with shell-style wildcards to a regular expression. (Contributed by Barney Gale in gh-72904.)

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.)

ipaddress

marshal

  • Add the allow_code parameter in module functions. Passing allow_code=False prevents serialization and de-serialization of code objects which are incompatible between Python versions. (Contributed by Serhiy Storchaka in gh-113626.)

mmap

  • The mmap.mmap class now has an seekable() method that can be used when a seekable file-like object is required. The seek() method now returns the new absolute position. (Contributed by Donghee Na and Sylvie Liberman in gh-111835.)

  • mmap.mmap now has a trackfd parameter on Unix; if it is False, the file descriptor specified by fileno will not be duplicated. (Contributed by Zackery Spytz and Petr Viktorin in gh-78502.)

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.

os

os.path

  • Add os.path.isreserved() to check if a path is reserved on the current system. This function is only available on Windows. (Contributed by Barney Gale in gh-88569.)

  • On Windows, os.path.isabs() no longer considers paths starting with exactly one (back)slash to be absolute. (Contributed by Barney Gale and Jon Foster in gh-44626.)

pathlib

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.)

  • sys.path[0] will no longer be replaced by the directory of the script being debugged when sys.flags.safe_path is set (via the -P command line option or PYTHONSAFEPATH environment variable). (Contributed by Tian Gao and Christian Walther in gh-111762.)

queue

re

  • Rename re.error to re.PatternError for improved clarity. re.error is kept for backward compatibility.

sqlite3

subprocess

  • The subprocess module now uses the os.posix_spawn() function in more situations. Notably in the default case of close_fds=True on more recent versions of platforms including Linux, FreeBSD, and Solaris where the C library provides posix_spawn_file_actions_addclosefrom_np(). On Linux this should perform similar to our existing Linux vfork() based code. A private control knob subprocess._USE_POSIX_SPAWN can be set to False if you need to force subprocess not to ever use os.posix_spawn(). Please report your reason and platform details in the CPython issue tracker if you set this so that we can improve our API selection logic for everyone. (Contributed by Jakub Kulik in gh-113117.)

sys

  • Add the sys._is_interned() function to test if the string was interned. This function is not guaranteed to exist in all implementations of Python. (Contributed by Serhiy Storchaka in gh-78573.)

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.)

  • The tkinter widget method wm_attributes() now accepts the attribute name without the minus prefix to get window attributes, e.g. w.wm_attributes('alpha') and allows to specify attributes and values to set as keyword arguments, e.g. w.wm_attributes(alpha=0.5). Add new optional keyword-only parameter return_python_dict: calling w.wm_attributes(return_python_dict=True) returns the attributes as a dict instead of a tuple. (Contributed by Serhiy Storchaka in gh-43457.)

  • Add new optional keyword-only parameter return_ints in the Text.count() method. Passing return_ints=True makes it always returning the single count as an integer instead of a 1-tuple or None. (Contributed by Serhiy Storchaka in gh-97928.)

  • Add support of the “vsapi” element type in the element_create() method of tkinter.ttk.Style. (Contributed by Serhiy Storchaka in gh-68166.)

traceback

typing

unicodedata

  • The Unicode database has been updated to version 15.1.0. (Contributed by James Gerity in gh-109559.)

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.)

warnings

  • The new warnings.deprecated() decorator provides a way to communicate deprecations to static type checkers and to warn on usage of deprecated classes and functions. A runtime deprecation warning may also be emitted when a decorated function or class is used at runtime. See PEP 702. (Contributed by Jelle Zijlstra in gh-104003.)

xml.etree.ElementTree

  • Add the close() method for the iterator returned by iterparse() for explicit cleaning up. (Contributed by Serhiy Storchaka in gh-69893.)

Optimizations

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

  • The subprocess module uses os.posix_spawn() in more situations including the default where close_fds=True on many modern platforms. This should provide a noteworthy performance increase launching processes on FreeBSD and Solaris. See the subprocess section above for details. (Contributed by Jakub Kulik in gh-113117.)

Experimental JIT Compiler

When CPython is configured using the --enable-experimental-jit option, a just-in-time compiler is added which can speed up some Python programs.

The internal architecture is roughly as follows.

  • We start with specialized Tier 1 bytecode. See What’s new in 3.11 for details.

  • When the Tier 1 bytecode gets hot enough, it gets translated to a new, purely internal Tier 2 IR, a.k.a. micro-ops (“uops”).

  • The Tier 2 IR uses the same stack-based VM as Tier 1, but the instruction format is better suited to translation to machine code.

  • We have several optimization passes for Tier 2 IR, which are applied before it is interpreted or translated to machine code.

  • There is a Tier 2 interpreter, but it is mostly intended for debugging the earlier stages of the optimization pipeline. If the JIT is not enabled, the Tier 2 interpreter can be invoked by passing Python the -X uops option or by setting the PYTHON_UOPS environment variable to 1.

  • When the --enable-experimental-jit option is used, the optimized Tier 2 IR is translated to machine code, which is then executed. This does not require additional runtime options.

  • The machine code translation process uses an architecture called copy-and-patch. It has no runtime dependencies, but there is a new build-time dependency on LLVM.

(JIT by Brandt Bucher, inspired by a paper by Haoran Xu and Fredrik Kjolstad. Tier 2 IR by Mark Shannon and Guido van Rossum. Tier 2 optimizer by Ken Jin.)

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.)

  • decimal: Deprecate non-standard format specifier “N” for decimal.Decimal. It was not documented and only supported in the C implementation. (Contributed by Serhiy Storchaka in gh-89902.)

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

  • getopt and optparse modules: They are now soft deprecated: the argparse module 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.)

  • gettext: Emit deprecation warning for non-integer numbers in gettext functions and methods that consider plural forms even if the translation was not found. (Contributed by Serhiy Storchaka in gh-88434.)

  • 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.

  • pathlib: pathlib.PurePath.is_reserved() is deprecated and scheduled for removal in Python 3.15. Use os.path.isreserved() to detect reserved paths on Windows.

  • pydoc: Deprecate undocumented pydoc.ispackage() function. (Contributed by Zackery Spytz in gh-64020.)

  • sqlite3: 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:

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

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

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

  • sys: sys._enablelegacywindowsfsencoding() function. Replace it with the PYTHONLEGACYWINDOWSFSENCODING environment variable. (Contributed by Inada Naoki in gh-73427.)

  • traceback: The field exc_type of traceback.TracebackException is deprecated. Use exc_type_str instead.

  • 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.)

  • Calling frame.clear() on a suspended frame raises RuntimeError (as has always been the case for an executing frame). (Contributed by Irit Katriel in gh-79932.)

  • Assignment to a function’s __code__ attribute where the new code object’s type does not match the function’s type, is deprecated. The different types are: plain function, generator, async generator and coroutine. (Contributed by Irit Katriel in gh-81137.)

Pending Removal 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.

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

  • pathlib: pathlib.PurePath.is_reserved() is deprecated and scheduled for removal in Python 3.15. Use os.path.isreserved() to detect reserved paths on Windows.

  • threading: 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.)

  • 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.)

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.)

  • 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.

  • 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.

  • 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:

  • 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.

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

Removed

PEP 594: dead batteries

  • PEP 594 removed 19 modules from the standard library, deprecated in Python 3.11:

    • aifc. (Contributed by Victor Stinner in gh-104773.)

    • audioop. (Contributed by Victor Stinner in gh-104773.)

    • chunk. (Contributed by Victor Stinner in gh-104773.)

    • cgi and cgitb.

      • 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_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
        
      • 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.

      (Contributed by Victor Stinner in gh-104773.)

    • crypt module and its private _crypt extension. 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.)

    • imghdr: use the projects filetype, puremagic, or python-magic instead. (Contributed by Victor Stinner in gh-104773.)

    • mailcap. The mimetypes module provides an alternative. (Contributed by Victor Stinner in gh-104773.)

    • msilib. (Contributed by Zachary Ware in gh-104773.)

    • nis. (Contributed by Victor Stinner in gh-104773.)

    • nntplib: the PyPI nntplib project can be used instead. (Contributed by Victor Stinner in gh-104773.)

    • ossaudiodev: use the pygame project for audio playback. (Contributed by Victor Stinner in gh-104780.)

    • pipes: use the subprocess module instead. (Contributed by Victor Stinner in gh-104773.)

    • sndhdr: use the projects filetype, puremagic, or python-magic instead. (Contributed by Victor Stinner in gh-104773.)

    • spwd: the python-pam project can be used instead. (Contributed by Victor Stinner in gh-104773.)

    • sunau. (Contributed by Victor Stinner in gh-104773.)

    • telnetlib, use the projects telnetlib3 or Exscript instead. (Contributed by Victor Stinner in gh-104773.)

    • uu: the base64 module is a modern alternative. (Contributed by Victor Stinner in gh-104773.)

    • xdrlib. (Contributed by Victor Stinner in gh-104773.)

2to3

  • Remove the 2to3 program and the lib2to3 module, deprecated in Python 3.11. (Contributed by Victor Stinner in gh-104780.)

configparser

  • 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.)

importlib

locale

  • Remove locale.resetlocale() function deprecated in Python 3.11: use locale.setlocale(locale.LC_ALL, "") instead. (Contributed by Victor Stinner in gh-104783.)

logging

  • 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.)

pathlib

  • Remove support for using pathlib.Path objects as context managers. This functionality was deprecated and made a no-op in Python 3.9.

re

  • 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.)

tkinter

  • 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.)

turtle

  • 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.)

typing

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

unittest

urllib

webbrowser

  • 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 deprecated webbrowser.MacOSXOSAScript._name attribute. Use webbrowser.MacOSXOSAScript.name attribute instead. (Contributed by Nikita Sobolev in gh-105546.)

Others

  • None yet

CPython bytecode changes

  • The oparg of YIELD_VALUE is now 1 if the yield is part of a yield-from or await, and 0 otherwise. The oparg of RESUME was changed to add a bit indicating whether the except-depth is 1, which is needed to optimize closing of generators. (Contributed by Irit Katriel in gh-111354.)

Porting to Python 3.13

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

Changes in the Python API

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 the 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.

  • The errno, md5, resource, winsound, _ctypes_test, _multiprocessing.posixshmem, _scproxy, _stat, _testimportmultiple and _uuid C extensions are now built with the limited C API. (Contributed by Victor Stinner in gh-85283.)

  • wasm32-wasi is now a tier 2 platform. (Contributed by Brett Cannon in gh-115192.)

  • wasm32-emscripten is no longer a supported platform. (Contributed by Brett Cannon in gh-115192.)

C API Changes

New Features

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 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.)

  • If the Py_LIMITED_API macro is defined, Py_BUILD_CORE, Py_BUILD_CORE_BUILTIN and Py_BUILD_CORE_MODULE macros are now undefined by <Python.h>. (Contributed by Victor Stinner in gh-85283.)

  • 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.

  • On Windows, Python.h no longer includes the <stddef.h> standard header file. If needed, it should now be included explicitly. For example, it provides offsetof() function, and size_t and ptrdiff_t types. Including <stddef.h> explicitly was already needed by all other platforms, the HAVE_STDDEF_H macro is only defined on Windows. (Contributed by Victor Stinner in gh-108765.)

Deprecated

Removed

Pending Removal in Python 3.14

Pending Removal in Python 3.15

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.

Regression Test Changes

  • Python built with configure --with-pydebug now supports a -X presite=package.module command-line option. If used, it specifies a module that should be imported early in the lifecycle of the interpreter, before site.py is executed. (Contributed by Łukasz Langa in gh-110769.)