What's New In Python 3.11

Editor
Pablo Galindo Salgado

* Anyone can add text to this document. Do not spend very much time on the wording of your changes, because your text will probably get rewritten to some degree.

* The maintainer will go through Misc/NEWS periodically and add changes; it's therefore more important to add your changes to Misc/NEWS than to this file.

* This is not a complete list of every single change; completeness is the purpose of Misc/NEWS. Some changes I consider too small or esoteric to include. If such a change is added to the text, I'll just remove it. (This is another reason you shouldn't spend too much time on writing your addition.)

* If you want to draw your new text to the attention of the maintainer, add 'XXX' to the beginning of the paragraph or section.

* It's OK to just add a fragmentary note about a change. For example: "XXX Describe the transmogrify() function added to the socket module." The maintainer will research the change and write the necessary text.

* You can comment out your additions if you like, but it's not necessary (especially when a final release is some months away).

* Credit the author of a patch or bugfix. Just the name is sufficient; the e-mail address isn't necessary.

• It's helpful to add the bug/patch number as a comment:

XXX Describe the transmogrify() function added to the socket module. (Contributed by P.Y. Developer in 12345.)

This saves the maintainer the effort of going through the Mercurial log when researching a change.

This article explains the new features in Python 3.11, compared to 3.10. Python 3.11 was released on October 24, 2022. For full details, see the changelog <changelog>.

Summary -- Release highlights

• Python 3.11 is between 10-60% faster than Python 3.10. On average, we measured a 1.25x speedup on the standard benchmark suite. See whatsnew311-faster-cpython for details.

New syntax features:

• whatsnew311-pep654

New built-in features:

• whatsnew311-pep678

New standard library modules:

• 680: tomllib — Support for parsing TOML in the Standard Library

Interpreter improvements:

• whatsnew311-pep657
• New -P command line option and PYTHONSAFEPATH environment variable to disable automatically prepending potentially unsafe paths <whatsnew311-pythonsafepath> to sys.path

New typing features:

• whatsnew311-pep646
• whatsnew311-pep655
• whatsnew311-pep673
• whatsnew311-pep675
• whatsnew311-pep681

Important deprecations, removals and restrictions:

• 594: Many legacy standard library modules have been deprecated <whatsnew311-pep594> and will be removed in Python 3.13
• 624: Py_UNICODE encoder APIs have been removed <whatsnew311-pep624>
• 670: Macros converted to static inline functions <whatsnew311-pep670>

New Features

PEP 657: Fine-grained error locations in tracebacks

When printing tracebacks, the interpreter will now point to the exact expression that caused the error, instead of just the line. For example:

Traceback (most recent call last):
  File "distance.py", line 11, in <module>
    print(manhattan_distance(p1, p2))
          ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "distance.py", line 6, in manhattan_distance
    return abs(point_1.x - point_2.x) + abs(point_1.y - point_2.y)
                           ^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'x'

Previous versions of the interpreter would point to just the line, making it ambiguous which object was None. These enhanced errors can also be helpful when dealing with deeply nested dict objects and multiple function calls:

Traceback (most recent call last):
  File "query.py", line 37, in <module>
    magic_arithmetic('foo')
  File "query.py", line 18, in magic_arithmetic
    return add_counts(x) / 25
           ^^^^^^^^^^^^^
  File "query.py", line 24, in add_counts
    return 25 + query_user(user1) + query_user(user2)
                ^^^^^^^^^^^^^^^^^
  File "query.py", line 32, in query_user
    return 1 + query_count(db, response['a']['b']['c']['user'], retry=True)
                               ~~~~~~~~~~~~~~~~~~^^^^^
TypeError: 'NoneType' object is not subscriptable

As well as complex arithmetic expressions:

Traceback (most recent call last):
  File "calculation.py", line 54, in <module>
    result = (x / y / z) * (a / b / c)
              ~~~~~~^~~
ZeroDivisionError: division by zero

Additionally, the information used by the enhanced traceback feature is made available via a general API, that can be used to correlate bytecode instructions <bytecodes> with source code location. This information can be retrieved using:

• The codeobject.co_positions method in Python.
• The PyCode_Addr2Location function in the C API.

See 657 for more details. (Contributed by Pablo Galindo, Batuhan Taskaya and Ammar Askar in 43950.)

[!NOTE] This feature requires storing column positions in codeobjects, which may result in a small increase in interpreter memory usage and disk usage for compiled Python files. To avoid storing the extra information and deactivate printing the extra traceback information, use the -X no_debug_ranges <-X> command line option or the PYTHONNODEBUGRANGES environment variable.

PEP 654: Exception Groups and except*

654 introduces language features that enable a program to raise and handle multiple unrelated exceptions simultaneously. The builtin types ExceptionGroup and BaseExceptionGroup make it possible to group exceptions and raise them together, and the new except* <except_star> syntax generalizes except to match subgroups of exception groups.

See 654 for more details.

(Contributed by Irit Katriel in 45292. PEP written by Irit Katriel, Yury Selivanov and Guido van Rossum.)

PEP 678: Exceptions can be enriched with notes

The ~BaseException.add_note method is added to BaseException. It can be used to enrich exceptions with context information that is not available at the time when the exception is raised. The added notes appear in the default traceback.

See 678 for more details.

(Contributed by Irit Katriel in 45607. PEP written by Zac Hatfield-Dodds.)

Windows py.exe launcher improvements

The copy of the launcher included with Python 3.11 has been significantly updated. It now supports company/tag syntax as defined in 514 using the -V:{<company>}/{<tag>} argument instead of the limited -{<major>}.{<minor>}. This allows launching distributions other than PythonCore, the one hosted on python.org.

When using -V: selectors, either company or tag can be omitted, but all installs will be searched. For example, -V:OtherPython/ will select the "best" tag registered for OtherPython, while -V:3.11 or -V:/3.11 will select the "best" distribution with tag 3.11.

When using the legacy -{<major>}, -{<major>}.{<minor>}, -{<major>}-{<bitness>} or -{<major>}.{<minor>}-{<bitness>} arguments, all existing behaviour should be preserved from past versions, and only releases from PythonCore will be selected. However, the -64 suffix now implies "not 32-bit" (not necessarily x86-64), as there are multiple supported 64-bit platforms. 32-bit runtimes are detected by checking the runtime's tag for a -32 suffix. All releases of Python since 3.5 have included this in their 32-bit builds.

New Features Related to Type Hints

This section covers major changes affecting 484 type hints and the typing module.

PEP 646: Variadic generics

484 previously introduced ~typing.TypeVar, enabling creation of generics parameterised with a single type. 646 adds ~typing.TypeVarTuple, enabling parameterisation with an arbitrary number of types. In other words, a ~typing.TypeVarTuple is a variadic type variable, enabling variadic generics.

This enables a wide variety of use cases. In particular, it allows the type of array-like structures in numerical computing libraries such as NumPy and TensorFlow to be parameterised with the array shape. Static type checkers will now be able to catch shape-related bugs in code that uses these libraries.

See 646 for more details.

(Contributed by Matthew Rahtz in 43224, with contributions by Serhiy Storchaka and Jelle Zijlstra. PEP written by Mark Mendoza, Matthew Rahtz, Pradeep Kumar Srinivasan, and Vincent Siles.)

PEP 655: Marking individual TypedDict items as required or not-required

~typing.Required and ~typing.NotRequired provide a straightforward way to mark whether individual items in a ~typing.TypedDict must be present. Previously, this was only possible using inheritance.

All fields are still required by default, unless the total parameter is set to False, in which case all fields are still not-required by default. For example, the following specifies a !TypedDict with one required and one not-required key:

class Movie(TypedDict):
   title: str
   year: NotRequired[int]

m1: Movie = {"title": "Black Panther", "year": 2018}  # OK
m2: Movie = {"title": "Star Wars"}  # OK (year is not required)
m3: Movie = {"year": 2022}  # ERROR (missing required field title)

The following definition is equivalent:

class Movie(TypedDict, total=False):
   title: Required[str]
   year: int

See 655 for more details.

(Contributed by David Foster and Jelle Zijlstra in 47087. PEP written by David Foster.)

PEP 673: Self type

The new ~typing.Self annotation provides a simple and intuitive way to annotate methods that return an instance of their class. This behaves the same as the ~typing.TypeVar-based approach specified in PEP 484 <484#annotating-instance-and-class-methods>, but is more concise and easier to follow.

Common use cases include alternative constructors provided as classmethod <classmethod>s, and ~object.__enter__ methods that return self:

class MyLock:
    def __enter__(self) -> Self:
        self.lock()
        return self

    ...

class MyInt:
    @classmethod
    def fromhex(cls, s: str) -> Self:
        return cls(int(s, 16))

    ...

~typing.Self can also be used to annotate method parameters or attributes of the same type as their enclosing class.

See 673 for more details.

(Contributed by James Hilton-Balfe in 46534. PEP written by Pradeep Kumar Srinivasan and James Hilton-Balfe.)

PEP 675: Arbitrary literal string type

The new ~typing.LiteralString annotation may be used to indicate that a function parameter can be of any literal string type. This allows a function to accept arbitrary literal string types, as well as strings created from other literal strings. Type checkers can then enforce that sensitive functions, such as those that execute SQL statements or shell commands, are called only with static arguments, providing protection against injection attacks.

For example, a SQL query function could be annotated as follows:

def run_query(sql: LiteralString) -> ...:
    ...

def caller(
    arbitrary_string: str,
    query_string: LiteralString,
    table_name: LiteralString,
) -> None:
    run_query("SELECT * FROM students")       # ok
    run_query(query_string)                   # ok
    run_query("SELECT * FROM " + table_name)  # ok
    run_query(arbitrary_string)               # type checker error
    run_query(                                # type checker error
        f"SELECT * FROM students WHERE name = {arbitrary_string}"
    )

See 675 for more details.

(Contributed by Jelle Zijlstra in 47088. PEP written by Pradeep Kumar Srinivasan and Graham Bleaney.)

PEP 681: Data class transforms

~typing.dataclass_transform may be used to decorate a class, metaclass, or a function that is itself a decorator. The presence of @dataclass_transform() tells a static type checker that the decorated object performs runtime "magic" that transforms a class, giving it dataclass <dataclasses.dataclass>-like behaviors.

For example:

# The create_model decorator is defined by a library.
@typing.dataclass_transform()
def create_model(cls: Type[T]) -> Type[T]:
    cls.__init__ = ...
    cls.__eq__ = ...
    cls.__ne__ = ...
    return cls

# The create_model decorator can now be used to create new model classes:
@create_model
class CustomerModel:
    id: int
    name: str

c = CustomerModel(id=327, name="Eric Idle")

See 681 for more details.

(Contributed by Jelle Zijlstra in 91860. PEP written by Erik De Bonte and Eric Traut.)

PEP 563 may not be the future

563 Postponed Evaluation of Annotations (the from __future__ import annotations future statement <future>) that was originally planned for release in Python 3.10 has been put on hold indefinitely. See this message from the Steering Council for more information.

Other Language Changes

• Starred unpacking expressions can now be used in for statements. (See 46725 for more details.)
• Asynchronous comprehensions <comprehensions> are now allowed inside comprehensions in asynchronous functions <async def>. Outer comprehensions implicitly become asynchronous in this case. (Contributed by Serhiy Storchaka in 33346.)
• A TypeError is now raised instead of an AttributeError in with statements and contextlib.ExitStack.enter_context for objects that do not support the context manager protocol, and in async with statements and contextlib.AsyncExitStack.enter_async_context for objects not supporting the asynchronous context manager protocol. (Contributed by Serhiy Storchaka in 12022 and 44471.)
• Added object.__getstate__, which provides the default implementation of the !__getstate__ method. copying and pickleing instances of subclasses of builtin types bytearray, set, frozenset, collections.OrderedDict, collections.deque, weakref.WeakSet, and datetime.tzinfo now copies and pickles instance attributes implemented as slots <__slots__>. This change has an unintended side effect: It trips up a small minority of existing Python projects not expecting object.__getstate__ to exist. See the later comments on 70766 for discussions of what workarounds such code may need. (Contributed by Serhiy Storchaka in 26579.)

Other CPython Implementation Changes

• The special methods ~object.__complex__ for complex and ~object.__bytes__ for bytes are implemented to support the typing.SupportsComplex and typing.SupportsBytes protocols. (Contributed by Mark Dickinson and Donghee Na in 24234.)
• siphash13 is added as a new internal hashing algorithm. It has similar security properties as siphash24, but it is slightly faster for long inputs. str, bytes, and some other types now use it as the default algorithm for hash. 552 hash-based .pyc files <pyc-invalidation> now use siphash13 too. (Contributed by Inada Naoki in 29410.)
• When an active exception is re-raised by a raise statement with no parameters, the traceback attached to this exception is now always sys.exc_info()[1].__traceback__. This means that changes made to the traceback in the current except clause are reflected in the re-raised exception. (Contributed by Irit Katriel in 45711.)
• The interpreter state's representation of handled exceptions (aka exc_info or _PyErr_StackItem) now only has the exc_value field; exc_type and exc_traceback have been removed, as they can be derived from exc_value. (Contributed by Irit Katriel in 45711.)
• A new command line option, AppendPath, has been added for the Windows installer. It behaves similarly to PrependPath, but appends the install and scripts directories instead of prepending them. (Contributed by Bastian Neuburger in 44934.)
• The PyConfig.module_search_paths_set field must now be set to 1 for initialization to use PyConfig.module_search_paths to initialize sys.path. Otherwise, initialization will recalculate the path and replace any values added to module_search_paths.
• The output of the --help option now fits in 50 lines/80 columns. Information about Python environment variables <using-on-envvars> and -X options is now available using the respective --help-env and --help-xoptions flags, and with the new --help-all. (Contributed by Éric Araujo in 46142.)
• Converting between int and str in bases other than 2 (binary), 4, 8 (octal), 16 (hexadecimal), or 32 such as base 10 (decimal) now raises a ValueError if the number of digits in string form is above a limit to avoid potential denial of service attacks due to the algorithmic complexity. This is a mitigation for 2020-10735. This limit can be configured or disabled by environment variable, command line flag, or sys APIs. See the integer string conversion length limitation <int_max_str_digits> documentation. The default limit is 4300 digits in string form.

New Modules

• tomllib: For parsing TOML. See 680 for more details. (Contributed by Taneli Hukkinen in 40059.)
• wsgiref.types: WSGI <3333>-specific types for static type checking. (Contributed by Sebastian Rittau in 42012.)

Improved Modules

asyncio

• Added the ~asyncio.TaskGroup class, an asynchronous context manager <async-context-managers> holding a group of tasks that will wait for all of them upon exit. For new code this is recommended over using ~asyncio.create_task and ~asyncio.gather directly. (Contributed by Yury Selivanov and others in 90908.)
• Added ~asyncio.timeout, an asynchronous context manager for setting a timeout on asynchronous operations. For new code this is recommended over using ~asyncio.wait_for directly. (Contributed by Andrew Svetlov in 90927.)
• Added the ~asyncio.Runner class, which exposes the machinery used by ~asyncio.run. (Contributed by Andrew Svetlov in 91218.)
• Added the ~asyncio.Barrier class to the synchronization primitives in the asyncio library, and the related ~asyncio.BrokenBarrierError exception. (Contributed by Yves Duprat and Andrew Svetlov in 87518.)
• Added keyword argument all_errors to asyncio.loop.create_connection so that multiple connection errors can be raised as an ExceptionGroup.
• Added the asyncio.StreamWriter.start_tls method for upgrading existing stream-based connections to TLS. (Contributed by Ian Good in 34975.)
• Added raw datagram socket functions to the event loop: ~asyncio.loop.sock_sendto, ~asyncio.loop.sock_recvfrom and ~asyncio.loop.sock_recvfrom_into. These have implementations in ~asyncio.SelectorEventLoop and ~asyncio.ProactorEventLoop. (Contributed by Alex Grönholm in 46805.)
• Added ~asyncio.Task.cancelling and ~asyncio.Task.uncancel methods to ~asyncio.Task. These are primarily intended for internal use, notably by ~asyncio.TaskGroup.

contextlib

• Added non parallel-safe ~contextlib.chdir context manager to change the current working directory and then restore it on exit. Simple wrapper around ~os.chdir. (Contributed by Filipe Laíns in 25625)

dataclasses

• Change field default mutability check, allowing only defaults which are hashable instead of any object which is not an instance of dict, list or set. (Contributed by Eric V. Smith in 44674.)

datetime

• Add datetime.UTC, a convenience alias for datetime.timezone.utc. (Contributed by Kabir Kwatra in 91973.)
• datetime.date.fromisoformat, datetime.time.fromisoformat and datetime.datetime.fromisoformat can now be used to parse most ISO 8601 formats (barring only those that support fractional hours and minutes). (Contributed by Paul Ganssle in 80010.)

enum

• Renamed !EnumMeta to ~enum.EnumType (!EnumMeta kept as an alias).
• Added ~enum.StrEnum, with members that can be used as (and must be) strings.
• Added ~enum.ReprEnum, which only modifies the ~object.__repr__ of members while returning their literal values (rather than names) for ~object.__str__ and ~object.__format__ (used by str, format and f-strings).
• Changed Enum.__format__() <enum.Enum.__format__> (the default for format, str.format and f-strings) to always produce the same result as Enum.__str__() <enum.Enum.__str__>: for enums inheriting from ~enum.ReprEnum it will be the member's value; for all other enums it will be the enum and member name (e.g. Color.RED).
• Added a new boundary class parameter to ~enum.Flag enums and the ~enum.FlagBoundary enum with its options, to control how to handle out-of-range flag values.
• Added the ~enum.verify enum decorator and the ~enum.EnumCheck enum with its options, to check enum classes against several specific constraints.
• Added the ~enum.member and ~enum.nonmember decorators, to ensure the decorated object is/is not converted to an enum member.
• Added the ~enum.property decorator, which works like property except for enums. Use this instead of types.DynamicClassAttribute.
• Added the ~enum.global_enum enum decorator, which adjusts ~object.__repr__ and ~object.__str__ to show values as members of their module rather than the enum class. For example, 're.ASCII' for the ~re.ASCII member of re.RegexFlag rather than 'RegexFlag.ASCII'.
• Enhanced ~enum.Flag to support len, iteration and in/not in on its members. For example, the following now works: len(AFlag(3)) == 2 and list(AFlag(3)) == (AFlag.ONE, AFlag.TWO)
• Changed ~enum.Enum and ~enum.Flag so that members are now defined before ~object.__init_subclass__ is called; dir now includes methods, etc., from mixed-in data types.
• Changed ~enum.Flag to only consider primary values (power of two) canonical while composite values (3, 6, 10, etc.) are considered aliases; inverted flags are coerced to their positive equivalent.

fcntl

• On FreeBSD, the !F_DUP2FD and !F_DUP2FD_CLOEXEC flags respectively are supported, the former equals to dup2 usage while the latter set the FD_CLOEXEC flag in addition.

fractions

• Support PEP 515-style initialization of ~fractions.Fraction from string. (Contributed by Sergey B Kirpichev in 44258.)
• ~fractions.Fraction now implements an __int__ method, so that an isinstance(some_fraction, typing.SupportsInt) check passes. (Contributed by Mark Dickinson in 44547.)

functools

• functools.singledispatch now supports types.UnionType and typing.Union as annotations to the dispatch argument.:

  >>> from functools import singledispatch
  >>> @singledispatch
  ... def fun(arg, verbose=False):
  ...     if verbose:
  ...         print("Let me just say,", end=" ")
  ...     print(arg)
  ...
  >>> @fun.register
  ... def _(arg: int | float, verbose=False):
  ...     if verbose:
  ...         print("Strength in numbers, eh?", end=" ")
  ...     print(arg)
  ...
  >>> from typing import Union
  >>> @fun.register
  ... def _(arg: Union[list, set], verbose=False):
  ...     if verbose:
  ...         print("Enumerate this:")
  ...     for i, elem in enumerate(arg):
  ...         print(i, elem)
  ...
  

  (Contributed by Yurii Karabas in 46014.)

gzip

• The gzip.compress function is now faster when used with the mtime=0 argument as it delegates the compression entirely to a single zlib.compress operation. There is one side effect of this change: The gzip file header contains an "OS" byte in its header. That was traditionally always set to a value of 255 representing "unknown" by the gzip module. Now, when using ~gzip.compress with mtime=0, it may be set to a different value by the underlying zlib C library Python was linked against. (See 112346 for details on the side effect.)

hashlib

• hashlib.blake2b and hashlib.blake2s now prefer libb2 over Python's vendored copy. (Contributed by Christian Heimes in 47095.)
• The internal _sha3 module with SHA3 and SHAKE algorithms now uses tiny_sha3 instead of the Keccak Code Package to reduce code and binary size. The hashlib module prefers optimized SHA3 and SHAKE implementations from OpenSSL. The change affects only installations without OpenSSL support. (Contributed by Christian Heimes in 47098.)
• Add hashlib.file_digest, a helper function for efficient hashing of files or file-like objects. (Contributed by Christian Heimes in 89313.)

IDLE and idlelib

• Apply syntax highlighting to .pyi files. (Contributed by Alex Waygood and Terry Jan Reedy in 45447.)
• Include prompts when saving Shell with inputs and outputs. (Contributed by Terry Jan Reedy in 95191.)

inspect

• Add ~inspect.getmembers_static to return all members without triggering dynamic lookup via the descriptor protocol. (Contributed by Weipeng Hong in 30533.)

• Add ~inspect.ismethodwrapper for checking if the type of an object is a ~types.MethodWrapperType. (Contributed by Hakan Çelik in 29418.)

• Change the frame-related functions in the inspect module to return new ~inspect.FrameInfo and ~inspect.Traceback class instances (backwards compatible with the previous named tuple-like interfaces) that includes the extended 657 position information (end line number, column and end column). The affected functions are:

  • inspect.getframeinfo
  • inspect.getouterframes
  • inspect.getinnerframes,
  • inspect.stack
  • inspect.trace

  (Contributed by Pablo Galindo in 88116.)

locale

• Add locale.getencoding to get the current locale encoding. It is similar to locale.getpreferredencoding(False) but ignores the Python UTF-8 Mode <utf8-mode>.

logging

• Added ~logging.getLevelNamesMapping to return a mapping from logging level names (e.g. 'CRITICAL') to the values of their corresponding levels (e.g. 50, by default). (Contributed by Andrei Kulakovin in 88024.)
• Added a ~logging.handlers.SysLogHandler.createSocket method to ~logging.handlers.SysLogHandler, to match SocketHandler.createSocket() <logging.handlers.SocketHandler.createSocket>. It is called automatically during handler initialization and when emitting an event, if there is no active socket. (Contributed by Kirill Pinchuk in 88457.)

math

• Add math.exp2: return 2 raised to the power of x. (Contributed by Gideon Mitchell in 45917.)
• Add math.cbrt: return the cube root of x. (Contributed by Ajith Ramachandran in 44357.)
• The behaviour of two math.pow corner cases was changed, for consistency with the IEEE 754 specification. The operations math.pow(0.0, -math.inf) and math.pow(-0.0, -math.inf) now return inf. Previously they raised ValueError. (Contributed by Mark Dickinson in 44339.)
• The math.nan value is now always available. (Contributed by Victor Stinner in 46917.)

operator

• A new function operator.call has been added, such that operator.call(obj, *args, **kwargs) == obj(*args, **kwargs). (Contributed by Antony Lee in 44019.)

os

• On Windows, os.urandom now uses BCryptGenRandom(), instead of CryptGenRandom() which is deprecated. (Contributed by Donghee Na in 44611.)

pathlib

• ~pathlib.Path.glob and ~pathlib.Path.rglob return only directories if pattern ends with a pathname components separator: ~os.sep or ~os.altsep. (Contributed by Eisuke Kawasima in 22276 and 33392.)

re

• Atomic grouping ((?>...)) and possessive quantifiers (*+, ++, ?+, {m,n}+) are now supported in regular expressions. (Contributed by Jeffrey C. Jacobs and Serhiy Storchaka in 433030.)

shutil

• Add optional parameter dir_fd in shutil.rmtree. (Contributed by Serhiy Storchaka in 46245.)

socket

• Add CAN Socket support for NetBSD. (Contributed by Thomas Klausner in 30512.)
• ~socket.create_connection has an option to raise, in case of failure to connect, an ExceptionGroup containing all errors instead of only raising the last error. (Contributed by Irit Katriel in 29980.)

sqlite3

• You can now disable the authorizer by passing None to ~sqlite3.Connection.set_authorizer. (Contributed by Erlend E. Aasland in 44491.)
• Collation name ~sqlite3.Connection.create_collation can now contain any Unicode character. Collation names with invalid characters now raise UnicodeEncodeError instead of sqlite3.ProgrammingError. (Contributed by Erlend E. Aasland in 44688.)
• sqlite3 exceptions now include the SQLite extended error code as ~sqlite3.Error.sqlite_errorcode and the SQLite error name as ~sqlite3.Error.sqlite_errorname. (Contributed by Aviv Palivoda, Daniel Shahaf, and Erlend E. Aasland in 16379 and 24139.)
• Add ~sqlite3.Connection.setlimit and ~sqlite3.Connection.getlimit to sqlite3.Connection for setting and getting SQLite limits by connection basis. (Contributed by Erlend E. Aasland in 45243.)
• sqlite3 now sets sqlite3.threadsafety based on the default threading mode the underlying SQLite library has been compiled with. (Contributed by Erlend E. Aasland in 45613.)
• sqlite3 C callbacks now use unraisable exceptions if callback tracebacks are enabled. Users can now register an unraisable hook handler <sys.unraisablehook> to improve their debug experience. (Contributed by Erlend E. Aasland in 45828.)
• Fetch across rollback no longer raises ~sqlite3.InterfaceError. Instead we leave it to the SQLite library to handle these cases. (Contributed by Erlend E. Aasland in 44092.)
• Add ~sqlite3.Connection.serialize and ~sqlite3.Connection.deserialize to sqlite3.Connection for serializing and deserializing databases. (Contributed by Erlend E. Aasland in 41930.)
• Add ~sqlite3.Connection.create_window_function to sqlite3.Connection for creating aggregate window functions. (Contributed by Erlend E. Aasland in 34916.)
• Add ~sqlite3.Connection.blobopen to sqlite3.Connection. sqlite3.Blob allows incremental I/O operations on blobs. (Contributed by Aviv Palivoda and Erlend E. Aasland in 24905.)

string

• Add ~string.Template.get_identifiers and ~string.Template.is_valid to string.Template, which respectively return all valid placeholders, and whether any invalid placeholders are present. (Contributed by Ben Kehoe in 90465.)

sys

• sys.exc_info now derives the type and traceback fields from the value (the exception instance), so when an exception is modified while it is being handled, the changes are reflected in the results of subsequent calls to !exc_info. (Contributed by Irit Katriel in 45711.)
• Add sys.exception which returns the active exception instance (equivalent to sys.exc_info()[1]). (Contributed by Irit Katriel in 46328.)
• Add the sys.flags.safe_path <sys.flags> flag. (Contributed by Victor Stinner in 57684.)

sysconfig

• Three new installation schemes <installation_paths> (posix_venv, nt_venv and venv) were added and are used when Python creates new virtual environments or when it is running from a virtual environment. The first two schemes (posix_venv and nt_venv) are OS-specific for non-Windows and Windows, the venv is essentially an alias to one of them according to the OS Python runs on. This is useful for downstream distributors who modify sysconfig.get_preferred_scheme. Third party code that creates new virtual environments should use the new venv installation scheme to determine the paths, as does venv. (Contributed by Miro Hrončok in 45413.)

tempfile

• ~tempfile.SpooledTemporaryFile objects now fully implement the methods of io.BufferedIOBase or io.TextIOBase (depending on file mode). This lets them work correctly with APIs that expect file-like objects, such as compression modules. (Contributed by Carey Metcalfe in 70363.)

threading

• On Unix, if the sem_clockwait() function is available in the C library (glibc 2.30 and newer), the threading.Lock.acquire method now uses the monotonic clock (time.CLOCK_MONOTONIC) for the timeout, rather than using the system clock (time.CLOCK_REALTIME), to not be affected by system clock changes. (Contributed by Victor Stinner in 41710.)

time

• On Unix, time.sleep now uses the clock_nanosleep() or nanosleep() function, if available, which has a resolution of 1 nanosecond (10^-9 seconds), rather than using select() which has a resolution of 1 microsecond (10^-6 seconds). (Contributed by Benjamin Szőke and Victor Stinner in 21302.)
• On Windows 8.1 and newer, time.sleep now uses a waitable timer based on high-resolution timers which has a resolution of 100 nanoseconds (10^-7 seconds). Previously, it had a resolution of 1 millisecond (10^-3 seconds). (Contributed by Benjamin Szőke, Donghee Na, Eryk Sun and Victor Stinner in 21302 and 45429.)

tkinter

• Added method info_patchlevel() which returns the exact version of the Tcl library as a named tuple similar to sys.version_info. (Contributed by Serhiy Storchaka in 91827.)

traceback

• Add traceback.StackSummary.format_frame_summary to allow users to override which frames appear in the traceback, and how they are formatted. (Contributed by Ammar Askar in 44569.)
• Add traceback.TracebackException.print, which prints the formatted ~traceback.TracebackException instance to a file. (Contributed by Irit Katriel in 33809.)

typing

For major changes, see new-feat-related-type-hints-311.

• Add typing.assert_never and typing.Never. typing.assert_never is useful for asking a type checker to confirm that a line of code is not reachable. At runtime, it raises an AssertionError. (Contributed by Jelle Zijlstra in 90633.)
• Add typing.reveal_type. This is useful for asking a type checker what type it has inferred for a given expression. At runtime it prints the type of the received value. (Contributed by Jelle Zijlstra in 90572.)
• Add typing.assert_type. This is useful for asking a type checker to confirm that the type it has inferred for a given expression matches the given type. At runtime it simply returns the received value. (Contributed by Jelle Zijlstra in 90638.)
• typing.TypedDict types can now be generic. (Contributed by Samodya Abeysiriwardane in 89026.)
• ~typing.NamedTuple types can now be generic. (Contributed by Serhiy Storchaka in 43923.)
• Allow subclassing of typing.Any. This is useful for avoiding type checker errors related to highly dynamic class, such as mocks. (Contributed by Shantanu Jain in 91154.)
• The typing.final decorator now sets the __final__ attributed on the decorated object. (Contributed by Jelle Zijlstra in 90500.)
• The typing.get_overloads function can be used for introspecting the overloads of a function. typing.clear_overloads can be used to clear all registered overloads of a function. (Contributed by Jelle Zijlstra in 89263.)
• The ~object.__init__ method of ~typing.Protocol subclasses is now preserved. (Contributed by Adrian Garcia Badarasco in 88970.)
• The representation of empty tuple types (Tuple[()]) is simplified. This affects introspection, e.g. get_args(Tuple[()]) now evaluates to () instead of ((),). (Contributed by Serhiy Storchaka in 91137.)
• Loosen runtime requirements for type annotations by removing the callable check in the private typing._type_check function. (Contributed by Gregory Beauregard in 90802.)
• typing.get_type_hints now supports evaluating strings as forward references in PEP 585 generic aliases <types-genericalias>. (Contributed by Niklas Rosenstein in 85542.)
• typing.get_type_hints no longer adds ~typing.Optional to parameters with None as a default. (Contributed by Nikita Sobolev in 90353.)
• typing.get_type_hints now supports evaluating bare stringified ~typing.ClassVar annotations. (Contributed by Gregory Beauregard in 90711.)
• typing.no_type_check no longer modifies external classes and functions. It also now correctly marks classmethods as not to be type checked. (Contributed by Nikita Sobolev in 90729.)

unicodedata

• The Unicode database has been updated to version 14.0.0. (Contributed by Benjamin Peterson in 45190).

unittest

• Added methods ~unittest.TestCase.enterContext and ~unittest.TestCase.enterClassContext of class ~unittest.TestCase, method ~unittest.IsolatedAsyncioTestCase.enterAsyncContext of class ~unittest.IsolatedAsyncioTestCase and function unittest.enterModuleContext. (Contributed by Serhiy Storchaka in 45046.)

venv

• When new Python virtual environments are created, the venv sysconfig installation scheme <installation_paths> is used to determine the paths inside the environment. When Python runs in a virtual environment, the same installation scheme is the default. That means that downstream distributors can change the default sysconfig install scheme without changing behavior of virtual environments. Third party code that also creates new virtual environments should do the same. (Contributed by Miro Hrončok in 45413.)

warnings

• warnings.catch_warnings now accepts arguments for warnings.simplefilter, providing a more concise way to locally ignore warnings or convert them to errors. (Contributed by Zac Hatfield-Dodds in 47074.)

zipfile

• Added support for specifying member name encoding for reading metadata in a ~zipfile.ZipFile's directory and file headers. (Contributed by Stephen J. Turnbull and Serhiy Storchaka in 28080.)
• Added ZipFile.mkdir() <zipfile.ZipFile.mkdir> for creating new directories inside ZIP archives. (Contributed by Sam Ezeh in 49083.)
• Added ~zipfile.Path.stem, ~zipfile.Path.suffix and ~zipfile.Path.suffixes to zipfile.Path. (Contributed by Miguel Brito in 88261.)

Optimizations

This section covers specific optimizations independent of the whatsnew311-faster-cpython project, which is covered in its own section.

• The compiler now optimizes simple printf-style % formatting <old-string-formatting> on string literals containing only the format codes %s, %r and %a and makes it as fast as a corresponding f-string expression. (Contributed by Serhiy Storchaka in 28307.)
• Integer division (//) is better tuned for optimization by compilers. It is now around 20% faster on x86-64 when dividing an int by a value smaller than 2**30. (Contributed by Gregory P. Smith and Tim Peters in 90564.)
• sum is now nearly 30% faster for integers smaller than 2**30. (Contributed by Stefan Behnel in 68264.)
• Resizing lists is streamlined for the common case, speeding up list.append by ≈15% and simple list comprehensions by up to 20-30% (Contributed by Dennis Sweeney in 91165.)
• Dictionaries don't store hash values when all keys are Unicode objects, decreasing dict size. For example, sys.getsizeof(dict.fromkeys("abcdefg")) is reduced from 352 bytes to 272 bytes (23% smaller) on 64-bit platforms. (Contributed by Inada Naoki in 46845.)
• Using asyncio.DatagramProtocol is now orders of magnitude faster when transferring large files over UDP, with speeds over 100 times higher for a ≈60 MiB file. (Contributed by msoxzw in 91487.)
• math functions ~math.comb and ~math.perm are now ≈10 times faster for large arguments (with a larger speedup for larger k). (Contributed by Serhiy Storchaka in 37295.)
• The statistics functions ~statistics.mean, ~statistics.variance and ~statistics.stdev now consume iterators in one pass rather than converting them to a list first. This is twice as fast and can save substantial memory. (Contributed by Raymond Hettinger in 90415.)
• unicodedata.normalize now normalizes pure-ASCII strings in constant time. (Contributed by Donghee Na in 44987.)

Faster CPython

CPython 3.11 is an average of 25% faster than CPython 3.10 as measured with the pyperformance benchmark suite, when compiled with GCC on Ubuntu Linux. Depending on your workload, the overall speedup could be 10-60%.

This project focuses on two major areas in Python: whatsnew311-faster-startup and whatsnew311-faster-runtime. Optimizations not covered by this project are listed separately under whatsnew311-optimizations.

Faster Startup

Frozen imports / Static code objects

Python caches bytecode in the __pycache__ <tut-pycache> directory to speed up module loading.

Previously in 3.10, Python module execution looked like this:

Read __pycache__ -> Unmarshal -> Heap allocated code object -> Evaluate

In Python 3.11, the core modules essential for Python startup are "frozen". This means that their codeobjects (and bytecode) are statically allocated by the interpreter. This reduces the steps in module execution process to:

Statically allocated code object -> Evaluate

Interpreter startup is now 10-15% faster in Python 3.11. This has a big impact for short-running programs using Python.

(Contributed by Eric Snow, Guido van Rossum and Kumar Aditya in many issues.)

Faster Runtime

Cheaper, lazy Python frames

Python frames, holding execution information, are created whenever Python calls a Python function. The following are new frame optimizations:

• Streamlined the frame creation process.
• Avoided memory allocation by generously re-using frame space on the C stack.
• Streamlined the internal frame struct to contain only essential information. Frames previously held extra debugging and memory management information.

Old-style frame objects <frame-objects> are now created only when requested by debuggers or by Python introspection functions such as sys._getframe and inspect.currentframe. For most user code, no frame objects are created at all. As a result, nearly all Python functions calls have sped up significantly. We measured a 3-7% speedup in pyperformance.

(Contributed by Mark Shannon in 44590.)

Inlined Python function calls

During a Python function call, Python will call an evaluating C function to interpret that function's code. This effectively limits pure Python recursion to what's safe for the C stack.

In 3.11, when CPython detects Python code calling another Python function, it sets up a new frame, and "jumps" to the new code inside the new frame. This avoids calling the C interpreting function altogether.

Most Python function calls now consume no C stack space, speeding them up. In simple recursive functions like fibonacci or factorial, we observed a 1.7x speedup. This also means recursive functions can recurse significantly deeper (if the user increases the recursion limit with sys.setrecursionlimit). We measured a 1-3% improvement in pyperformance.

(Contributed by Pablo Galindo and Mark Shannon in 45256.)

PEP 659: Specializing Adaptive Interpreter

659 is one of the key parts of the Faster CPython project. The general idea is that while Python is a dynamic language, most code has regions where objects and types rarely change. This concept is known as type stability.

At runtime, Python will try to look for common patterns and type stability in the executing code. Python will then replace the current operation with a more specialized one. This specialized operation uses fast paths available only to those use cases/types, which generally outperform their generic counterparts. This also brings in another concept called inline caching, where Python caches the results of expensive operations directly in the bytecode.

The specializer will also combine certain common instruction pairs into one superinstruction, reducing the overhead during execution.

Python will only specialize when it sees code that is "hot" (executed multiple times). This prevents Python from wasting time on run-once code. Python can also de-specialize when code is too dynamic or when the use changes. Specialization is attempted periodically, and specialization attempts are not too expensive, allowing specialization to adapt to new circumstances.

(PEP written by Mark Shannon, with ideas inspired by Stefan Brunthaler. See 659 for more information. Implementation by Mark Shannon and Brandt Bucher, with additional help from Irit Katriel and Dennis Sweeney.)

Operation	Form	Specialization	Operation speedup (up to)	Contributor(s)
Binary operations	x + x x - x x * x	Binary add, multiply and subtract for common types such as int, float and str take custom fast paths for their underlying types.	10%	Mark Shannon, Donghee Na, Brandt Bucher, Dennis Sweeney
Subscript	a[i]	Subscripting container types such as list, tuple and dict directly index the underlying data structures. Subscripting custom ~object.__getitem__ is also inlined similar to inline-calls.	10-25%	Irit Katriel, Mark Shannon
Store subscript	a[i] = z	Similar to subscripting specialization above.	10-25%	Dennis Sweeney
Calls	f(arg) C(arg)	Calls to common builtin (C) functions and types such as len and str directly call their underlying C version. This avoids going through the internal calling convention.	20%	Mark Shannon, Ken Jin
Load global variable	print len	The object's index in the globals/builtins namespace is cached. Loading globals and builtins require zero namespace lookups.	1	Mark Shannon
Load attribute	o.attr	Similar to loading global variables. The attribute's index inside the class/object's namespace is cached. In most cases, attribute loading will require zero namespace lookups.	2	Mark Shannon
Load methods for call	o.meth()	The actual address of the method is cached. Method loading now has no namespace lookups -- even for classes with long inheritance chains.	10-20%	Ken Jin, Mark Shannon
Store attribute	o.attr = z	Similar to load attribute optimization.	2% in pyperformance	Mark Shannon
Unpack Sequence	*seq	Specialized for common containers such as list and tuple. Avoids internal calling convention.	8%	Brandt Bucher

---

1. A similar optimization already existed since Python 3.8. 3.11 specializes for more forms and reduces some overhead.↩︎

2. A similar optimization already existed since Python 3.10. 3.11 specializes for more forms. Furthermore, all attribute loads should be sped up by 45947.↩︎

Misc

• Objects now require less memory due to lazily created object namespaces. Their namespace dictionaries now also share keys more freely. (Contributed Mark Shannon in 45340 and 40116.)
• "Zero-cost" exceptions are implemented, eliminating the cost of try statements when no exception is raised. (Contributed by Mark Shannon in 40222.)
• A more concise representation of exceptions in the interpreter reduced the time required for catching an exception by about 10%. (Contributed by Irit Katriel in 45711.)
• re's regular expression matching engine has been partially refactored, and now uses computed gotos (or "threaded code") on supported platforms. As a result, Python 3.11 executes the pyperformance regular expression benchmarks up to 10% faster than Python 3.10. (Contributed by Brandt Bucher in 91404.)

FAQ

How should I write my code to utilize these speedups?

Write Pythonic code that follows common best practices; you don't have to change your code. The Faster CPython project optimizes for common code patterns we observe.

Will CPython 3.11 use more memory?

Maybe not; we don't expect memory use to exceed 20% higher than 3.10. This is offset by memory optimizations for frame objects and object dictionaries as mentioned above.

I don't see any speedups in my workload. Why?

Certain code won't have noticeable benefits. If your code spends most of its time on I/O operations, or already does most of its computation in a C extension library like NumPy, there won't be significant speedups. This project currently benefits pure-Python workloads the most.

Furthermore, the pyperformance figures are a geometric mean. Even within the pyperformance benchmarks, certain benchmarks have slowed down slightly, while others have sped up by nearly 2x!

Is there a JIT compiler?

No. We're still exploring other optimizations.

About

Faster CPython explores optimizations for CPython. The main team is funded by Microsoft to work on this full-time. Pablo Galindo Salgado is also funded by Bloomberg LP to work on the project part-time. Finally, many contributors are volunteers from the community.

CPython bytecode changes

The bytecode now contains inline cache entries, which take the form of the newly-added CACHE instructions. Many opcodes expect to be followed by an exact number of caches, and instruct the interpreter to skip over them at runtime. Populated caches can look like arbitrary instructions, so great care should be taken when reading or modifying raw, adaptive bytecode containing quickened data.

New opcodes

• !ASYNC_GEN_WRAP, RETURN_GENERATOR and SEND, used in generators and co-routines.
• COPY_FREE_VARS, which avoids needing special caller-side code for closures.
• JUMP_BACKWARD_NO_INTERRUPT, for use in certain loops where handling interrupts is undesirable.
• MAKE_CELL, to create cell-objects.
• CHECK_EG_MATCH and !PREP_RERAISE_STAR, to handle the new exception groups and except* <whatsnew311-pep654> added in 654.
• PUSH_EXC_INFO, for use in exception handlers.
• RESUME, a no-op, for internal tracing, debugging and optimization checks.

Replaced opcodes

Replaced Opcode(s)	New Opcode(s)	Notes
!BINARY_* !INPLACE_*	BINARY_OP	Replaced all numeric binary/in-place opcodes with a single opcode
!CALL_FUNCTION !CALL_FUNCTION_KW !CALL_METHOD	CALL !KW_NAMES !PRECALL PUSH_NULL	Decouples argument shifting for methods from handling of keyword arguments; allows better specialization of calls
!DUP_TOP !DUP_TOP_TWO !ROT_TWO !ROT_THREE !ROT_FOUR !ROT_N	COPY SWAP	Stack manipulation instructions
!JUMP_IF_NOT_EXC_MATCH	CHECK_EXC_MATCH	Now performs check but doesn't jump
!JUMP_ABSOLUTE !POP_JUMP_IF_FALSE !POP_JUMP_IF_TRUE	JUMP_BACKWARD !POP_JUMP_BACKWARD_IF_* !POP_JUMP_FORWARD_IF_*	See1; TRUE, FALSE, NONE and NOT_NONE variants for each direction
!SETUP_WITH !SETUP_ASYNC_WITH	!BEFORE_WITH	with block setup

---

1. All jump opcodes are now relative, including the existing !JUMP_IF_TRUE_OR_POP and !JUMP_IF_FALSE_OR_POP. The argument is now an offset from the current instruction rather than an absolute location.↩︎

Changed/removed opcodes

• Changed MATCH_CLASS and MATCH_KEYS to no longer push an additional boolean value to indicate success/failure. Instead, None is pushed on failure in place of the tuple of extracted values.
• Changed opcodes that work with exceptions to reflect them now being represented as one item on the stack instead of three (see 89874).
• Removed !COPY_DICT_WITHOUT_KEYS, !GEN_START, !POP_BLOCK, !SETUP_FINALLY and !YIELD_FROM.

Deprecated

This section lists Python APIs that have been deprecated in Python 3.11.

Deprecated C APIs are listed separately <whatsnew311-c-api-deprecated>.

Language/Builtins

• Chaining classmethod descriptors (introduced in 19072) is now deprecated. It can no longer be used to wrap other descriptors such as property. The core design of this feature was flawed and caused a number of downstream problems. To "pass-through" a classmethod, consider using the !__wrapped__ attribute that was added in Python 3.10. (Contributed by Raymond Hettinger in 89519.)
• Octal escapes in string and bytes literals with values larger than 0o377 (255 in decimal) now produce a DeprecationWarning. In a future Python version, they will raise a SyntaxWarning and eventually a SyntaxError. (Contributed by Serhiy Storchaka in 81548.)
• The delegation of int to ~object.__trunc__ is now deprecated. Calling int(a) when type(a) implements !__trunc__ but not ~object.__int__ or ~object.__index__ now raises a DeprecationWarning. (Contributed by Zackery Spytz in 44977.)

Modules

Standard Library

• The following have been deprecated in configparser since Python 3.2. Their deprecation warnings have now been updated to note they will be removed in Python 3.12:

  • the !configparser.SafeConfigParser class
  • the !configparser.ParsingError.filename property
  • the !configparser.RawConfigParser.readfp method

  (Contributed by Hugo van Kemenade in 45173.)

• !configparser.LegacyInterpolation has been deprecated in the docstring since Python 3.2, and is not listed in the configparser documentation. It now emits a DeprecationWarning and will be removed in Python 3.13. Use configparser.BasicInterpolation or configparser.ExtendedInterpolation instead. (Contributed by Hugo van Kemenade in 46607.)

• The older set of importlib.resources functions were deprecated in favor of the replacements added in Python 3.9 and will be removed in a future Python version, due to not supporting resources located within package subdirectories:

  • !importlib.resources.contents
  • !importlib.resources.is_resource
  • !importlib.resources.open_binary
  • !importlib.resources.open_text
  • !importlib.resources.read_binary
  • !importlib.resources.read_text
  • !importlib.resources.path

• The locale.getdefaultlocale function is deprecated and will be removed in Python 3.15. Use locale.setlocale, locale.getpreferredencoding(False) <locale.getpreferredencoding> and locale.getlocale functions instead. (Contributed by Victor Stinner in 90817.)

• The !locale.resetlocale function is deprecated and will be removed in Python 3.13. Use locale.setlocale(locale.LC_ALL, "") instead. (Contributed by Victor Stinner in 90817.)

• Stricter rules will now be applied for numerical group references and group names in regular expressions <re-syntax>. Only sequences of ASCII digits will now be accepted as a numerical reference, and the group name in bytes patterns and replacement strings can only contain ASCII letters, digits and underscores. For now, a deprecation warning is raised for syntax violating these rules. (Contributed by Serhiy Storchaka in 91760.)

• In the re module, the !re.template function and the corresponding !re.TEMPLATE and !re.T flags are deprecated, as they were undocumented and lacked an obvious purpose. They will be removed in Python 3.13. (Contributed by Serhiy Storchaka and Miro Hrončok in 92728.)

• !turtle.settiltangle has been deprecated since Python 3.1; it now emits a deprecation warning and will be removed in Python 3.13. Use turtle.tiltangle instead (it was earlier incorrectly marked as deprecated, and its docstring is now corrected). (Contributed by Hugo van Kemenade in 45837.)

• typing.Text, which exists solely to provide compatibility support between Python 2 and Python 3 code, is now deprecated. Its removal is currently unplanned, but users are encouraged to use str instead wherever possible. (Contributed by Alex Waygood in 92332.)

• The keyword argument syntax for constructing typing.TypedDict types is now deprecated. Support will be removed in Python 3.13. (Contributed by Jingchen Ye in 90224.)

• !webbrowser.MacOSX is deprecated and will be removed in Python 3.13. It is untested, undocumented, and not used by webbrowser itself. (Contributed by Donghee Na in 42255.)

• The behavior of returning a value from a ~unittest.TestCase and ~unittest.IsolatedAsyncioTestCase test methods (other than the default None value) is now deprecated.

• Deprecated the following not-formally-documented unittest functions, scheduled for removal in Python 3.13:

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

  Use ~unittest.TestLoader methods instead:

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

  (Contributed by Erlend E. Aasland in 5846.)

• !unittest.TestProgram.usageExit is marked deprecated, to be removed in 3.13. (Contributed by Carlos Damázio in 67048.)

Pending Removal in Python 3.12

The following Python APIs have been deprecated in earlier Python releases, and will be removed in Python 3.12.

C APIs pending removal are listed separately <whatsnew311-c-api-pending-removal>.

• The !asynchat module

• The !asyncore module

• The entire distutils package <distutils-deprecated>

• The !imp module

• The typing.io <typing.IO> namespace

• The typing.re <typing.Pattern> namespace

• !cgi.log

• !importlib.find_loader

• !importlib.abc.Loader.module_repr

• !importlib.abc.MetaPathFinder.find_module

• !importlib.abc.PathEntryFinder.find_loader

• !importlib.abc.PathEntryFinder.find_module

• !importlib.machinery.BuiltinImporter.find_module

• !importlib.machinery.BuiltinImporter.module_repr

• !importlib.machinery.FileFinder.find_loader

• !importlib.machinery.FileFinder.find_module

• !importlib.machinery.FrozenImporter.find_module

• !importlib.machinery.FrozenImporter.module_repr

• !importlib.machinery.PathFinder.find_module

• !importlib.machinery.WindowsRegistryFinder.find_module

• !importlib.util.module_for_loader

• !importlib.util.set_loader_wrapper

• !importlib.util.set_package_wrapper

• !pkgutil.ImpImporter

• !pkgutil.ImpLoader

• !pathlib.Path.link_to

• !sqlite3.enable_shared_cache

• !sqlite3.OptimizedUnicode

• !PYTHONTHREADDEBUG environment variable

• The following deprecated aliases in unittest:

  Deprecated alias	Method Name	Deprecated in
  failUnless	.assertTrue	3.1
  failIf	.assertFalse	3.1
  failUnlessEqual	.assertEqual	3.1
  failIfEqual	.assertNotEqual	3.1
  failUnlessAlmostEqual	.assertAlmostEqual	3.1
  failIfAlmostEqual	.assertNotAlmostEqual	3.1
  failUnlessRaises	.assertRaises	3.1
  assert_	.assertTrue	3.2
  assertEquals	.assertEqual	3.2
  assertNotEquals	.assertNotEqual	3.2
  assertAlmostEquals	.assertAlmostEqual	3.2
  assertNotAlmostEquals	.assertNotAlmostEqual	3.2
  assertRegexpMatches	.assertRegex	3.2
  assertRaisesRegexp	.assertRaisesRegex	3.2
  assertNotRegexpMatches	.assertNotRegex	3.5

Removed

This section lists Python APIs that have been removed in Python 3.11.

Removed C APIs are listed separately <whatsnew311-c-api-removed>.

• Removed the !@asyncio.coroutine decorator enabling legacy generator-based coroutines to be compatible with async / await code. The function has been deprecated since Python 3.8 and the removal was initially scheduled for Python 3.10. Use async def instead. (Contributed by Illia Volochii in 43216.)

• Removed !asyncio.coroutines.CoroWrapper used for wrapping legacy generator-based coroutine objects in the debug mode. (Contributed by Illia Volochii in 43216.)

• Due to significant security concerns, the reuse_address parameter of asyncio.loop.create_datagram_endpoint, disabled in Python 3.9, is now entirely removed. This is because of the behavior of the socket option SO_REUSEADDR in UDP. (Contributed by Hugo van Kemenade in 45129.)

• Removed the !binhex module, deprecated in Python 3.9. Also removed the related, similarly-deprecated binascii functions:

  • !binascii.a2b_hqx
  • !binascii.b2a_hqx
  • !binascii.rlecode_hqx
  • !binascii.rldecode_hqx

  The binascii.crc_hqx function remains available.

  (Contributed by Victor Stinner in 45085.)

• Removed the !distutils bdist_msi command deprecated in Python 3.9. Use bdist_wheel (wheel packages) instead. (Contributed by Hugo van Kemenade in 45124.)

• Removed the ~object.__getitem__ methods of xml.dom.pulldom.DOMEventStream, wsgiref.util.FileWrapper and fileinput.FileInput, deprecated since Python 3.9. (Contributed by Hugo van Kemenade in 45132.)

• Removed the deprecated gettext functions !lgettext, !ldgettext, !lngettext and !ldngettext. Also removed the !bind_textdomain_codeset function, the !NullTranslations.output_charset and !NullTranslations.set_output_charset methods, and the codeset parameter of !translation and !install, since they are only used for the !l*gettext functions. (Contributed by Donghee Na and Serhiy Storchaka in 44235.)

• Removed from the inspect module:

  • The !getargspec function, deprecated since Python 3.0; use inspect.signature or inspect.getfullargspec instead.
  • The !formatargspec function, deprecated since Python 3.5; use the inspect.signature function or the inspect.Signature object directly.
  • The undocumented !Signature.from_builtin and !Signature.from_function methods, deprecated since Python 3.5; use the Signature.from_callable() <inspect.Signature.from_callable> method instead.

  (Contributed by Hugo van Kemenade in 45320.)

• Removed the ~object.__class_getitem__ method from pathlib.PurePath, because it was not used and added by mistake in previous versions. (Contributed by Nikita Sobolev in 46483.)

• Removed the !MailmanProxy class in the !smtpd module, as it is unusable without the external !mailman package. (Contributed by Donghee Na in 35800.)

• Removed the deprecated !split method of !_tkinter.TkappType. (Contributed by Erlend E. Aasland in 38371.)

• Removed namespace package support from unittest discovery. It was introduced in Python 3.4 but has been broken since Python 3.7. (Contributed by Inada Naoki in 23882.)

• Removed the undocumented private !float.__set_format__ method, previously known as !float.__setformat__ in Python 3.7. Its docstring said: "You probably don't want to use this function. It exists mainly to be used in Python's test suite." (Contributed by Victor Stinner in 46852.)

• The !--experimental-isolated-subinterpreters configure flag (and corresponding !EXPERIMENTAL_ISOLATED_SUBINTERPRETERS macro) have been removed.

• Pynche --- The Pythonically Natural Color and Hue Editor --- has been moved out of Tools/scripts and is being developed independently from the Python source tree.

Porting to Python 3.11

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

Porting notes for the C API are listed separately <whatsnew311-c-api-porting>.

• open, io.open, codecs.open and fileinput.FileInput no longer accept 'U' ("universal newline") in the file mode. In Python 3, "universal newline" mode is used by default whenever a file is opened in text mode, and the 'U' flag has been deprecated since Python 3.3. The newline parameter <open-newline-parameter> to these functions controls how universal newlines work. (Contributed by Victor Stinner in 37330.)
• ast.AST node positions are now validated when provided to compile and other related functions. If invalid positions are detected, a ValueError will be raised. (Contributed by Pablo Galindo in 93351)
• Prohibited passing non-concurrent.futures.ThreadPoolExecutor executors to asyncio.loop.set_default_executor following a deprecation in Python 3.8. (Contributed by Illia Volochii in 43234.)
• calendar: The calendar.LocaleTextCalendar and calendar.LocaleHTMLCalendar classes now use locale.getlocale, instead of using locale.getdefaultlocale, if no locale is specified. (Contributed by Victor Stinner in 46659.)
• The pdb module now reads the .pdbrc configuration file with the 'UTF-8' encoding. (Contributed by Srinivas Reddy Thatiparthy (శ్రీనివాస్ రెడ్డి తాటిపర్తి) in 41137.)
• The population parameter of random.sample must be a sequence, and automatic conversion of sets to lists is no longer supported. Also, if the sample size is larger than the population size, a ValueError is raised. (Contributed by Raymond Hettinger in 40465.)
• The random optional parameter of random.shuffle was removed. It was previously an arbitrary random function to use for the shuffle; now, random.random (its previous default) will always be used.
• In re re-syntax, global inline flags (e.g. (?i)) can now only be used at the start of regular expressions. Using them elsewhere has been deprecated since Python 3.6. (Contributed by Serhiy Storchaka in 47066.)
• In the re module, several long-standing bugs where fixed that, in rare cases, could cause capture groups to get the wrong result. Therefore, this could change the captured output in these cases. (Contributed by Ma Lin in 35859.)

Build Changes

• CPython now has 11 Tier 3 support <11#tier-3> for cross compiling to the WebAssembly platforms Emscripten (wasm32-unknown-emscripten, i.e. Python in the browser) and WebAssembly System Interface (WASI) (wasm32-unknown-wasi). The effort is inspired by previous work like Pyodide. These platforms provide a limited subset of POSIX APIs; Python standard libraries features and modules related to networking, processes, threading, signals, mmap, and users/groups are not available or don't work. (Emscripten contributed by Christian Heimes and Ethan Smith in 84461 and WASI contributed by Christian Heimes in 90473; platforms promoted in 95085)

• Building CPython now requires:

  • A C11 compiler and standard library. Optional C11 features are not required. (Contributed by Victor Stinner in 46656, 45440 and 46640.)
  • Support for IEEE 754 floating-point numbers. (Contributed by Victor Stinner in 46917.)

• The !Py_NO_NAN macro has been removed. Since CPython now requires IEEE 754 floats, NaN values are always available. (Contributed by Victor Stinner in 46656.)

• The tkinter package now requires Tcl/Tk version 8.5.12 or newer. (Contributed by Serhiy Storchaka in 46996.)

• Build dependencies, compiler flags, and linker flags for most stdlib extension modules are now detected by configure. libffi, libnsl, libsqlite3, zlib, bzip2, liblzma, libcrypt, Tcl/Tk, and uuid flags are detected by pkg-config (when available). tkinter now requires a pkg-config command to detect development settings for Tcl/Tk headers and libraries. (Contributed by Christian Heimes and Erlend Egeberg Aasland in 45847, 45747, and 45763.)

• libpython is no longer linked against libcrypt. (Contributed by Mike Gilbert in 45433.)

• CPython can now be built with the ThinLTO option via passing thin to --with-lto, i.e. --with-lto=thin. (Contributed by Donghee Na and Brett Holman in 44340.)

• Freelists for object structs can now be disabled. A new configure option --without-freelists can be used to disable all freelists except empty tuple singleton. (Contributed by Christian Heimes in 45522.)

• Modules/Setup and Modules/makesetup have been improved and tied up. Extension modules can now be built through makesetup. All except some test modules can be linked statically into a main binary or library. (Contributed by Brett Cannon and Christian Heimes in 45548, 45570, 45571, and 43974.)

  [!NOTE] Use the environment variables !TCLTK_CFLAGS and !TCLTK_LIBS to manually specify the location of Tcl/Tk headers and libraries. The configure options !--with-tcltk-includes and !--with-tcltk-libs have been removed.

  On RHEL 7 and CentOS 7 the development packages do not provide tcl.pc and tk.pc; use TCLTK_LIBS="-ltk8.5 -ltkstub8.5 -ltcl8.5". The directory Misc/rhel7 contains .pc files and instructions on how to build Python with RHEL 7's and CentOS 7's Tcl/Tk and OpenSSL.

• CPython will now use 30-bit digits by default for the Python int implementation. Previously, the default was to use 30-bit digits on platforms with SIZEOF_VOID_P >= 8, and 15-bit digits otherwise. It's still possible to explicitly request use of 15-bit digits via either the --enable-big-digits option to the configure script or (for Windows) the PYLONG_BITS_IN_DIGIT variable in PC/pyconfig.h, but this option may be removed at some point in the future. (Contributed by Mark Dickinson in 45569.)

C API Changes

New Features

• Add a new PyType_GetName function to get type's short name. (Contributed by Hai Shi in 42035.)

• Add a new PyType_GetQualName function to get type's qualified name. (Contributed by Hai Shi in 42035.)

• Add new PyThreadState_EnterTracing and PyThreadState_LeaveTracing functions to the limited C API to suspend and resume tracing and profiling. (Contributed by Victor Stinner in 43760.)

• Added the Py_Version constant which bears the same value as PY_VERSION_HEX. (Contributed by Gabriele N. Tornetta in 43931.)

• Py_buffer and APIs are now part of the limited API and the stable ABI:

  • PyObject_CheckBuffer
  • PyObject_GetBuffer
  • PyBuffer_GetPointer
  • PyBuffer_SizeFromFormat
  • PyBuffer_ToContiguous
  • PyBuffer_FromContiguous
  • PyObject_CopyData
  • PyBuffer_IsContiguous
  • PyBuffer_FillContiguousStrides
  • PyBuffer_FillInfo
  • PyBuffer_Release
  • PyMemoryView_FromBuffer
  • ~PyBufferProcs.bf_getbuffer and ~PyBufferProcs.bf_releasebuffer type slots

  (Contributed by Christian Heimes in 45459.)

• Added the PyType_GetModuleByDef function, used to get the module in which a method was defined, in cases where this information is not available directly (via PyCMethod). (Contributed by Petr Viktorin in 46613.)

• Add new functions to pack and unpack C double (serialize and deserialize): PyFloat_Pack2, PyFloat_Pack4, PyFloat_Pack8, PyFloat_Unpack2, PyFloat_Unpack4 and PyFloat_Unpack8. (Contributed by Victor Stinner in 46906.)

• Add new functions to get frame object attributes: PyFrame_GetBuiltins, PyFrame_GetGenerator, PyFrame_GetGlobals, PyFrame_GetLasti.

• Added two new functions to get and set the active exception instance: PyErr_GetHandledException and PyErr_SetHandledException. These are alternatives to PyErr_SetExcInfo() and PyErr_GetExcInfo() which work with the legacy 3-tuple representation of exceptions. (Contributed by Irit Katriel in 46343.)

• Added the PyConfig.safe_path member. (Contributed by Victor Stinner in 57684.)

Porting to Python 3.11

Deprecated

• Deprecate the following functions to configure the Python initialization:

  • !PySys_AddWarnOptionUnicode
  • !PySys_AddWarnOption
  • !PySys_AddXOption
  • !PySys_HasWarnOptions
  • !PySys_SetArgvEx
  • !PySys_SetArgv
  • !PySys_SetPath
  • !Py_SetPath
  • !Py_SetProgramName
  • !Py_SetPythonHome
  • !Py_SetStandardStreamEncoding
  • !_Py_SetProgramFullPath

  Use the new PyConfig API of the Python Initialization Configuration <init-config> instead (587). (Contributed by Victor Stinner in 88279.)

• Deprecate the ob_shash member of the PyBytesObject. Use PyObject_Hash instead. (Contributed by Inada Naoki in 46864.)

Pending Removal in Python 3.12

The following C APIs have been deprecated in earlier Python releases, and will be removed in Python 3.12.

• !PyUnicode_AS_DATA
• !PyUnicode_AS_UNICODE
• !PyUnicode_AsUnicodeAndSize
• !PyUnicode_AsUnicode
• !PyUnicode_FromUnicode
• !PyUnicode_GET_DATA_SIZE
• !PyUnicode_GET_SIZE
• !PyUnicode_GetSize
• !PyUnicode_IS_COMPACT
• !PyUnicode_IS_READY
• PyUnicode_READY
• !PyUnicode_WSTR_LENGTH
• !_PyUnicode_AsUnicode
• !PyUnicode_WCHAR_KIND
• PyUnicodeObject
• !PyUnicode_InternImmortal

Removed

• !PyFrame_BlockSetup and !PyFrame_BlockPop have been removed. (Contributed by Mark Shannon in 40222.)

• Remove the following math macros using the errno variable:

  • Py_ADJUST_ERANGE1()
  • Py_ADJUST_ERANGE2()
  • Py_OVERFLOWED()
  • Py_SET_ERANGE_IF_OVERFLOW()
  • Py_SET_ERRNO_ON_MATH_ERROR()

  (Contributed by Victor Stinner in 45412.)

• Remove Py_UNICODE_COPY() and Py_UNICODE_FILL() macros, deprecated since Python 3.3. Use PyUnicode_CopyCharacters() or memcpy() (wchar_t* string), and PyUnicode_Fill() functions instead. (Contributed by Victor Stinner in 41123.)

• Remove the pystrhex.h header file. It only contains private functions. C extensions should only include the main <Python.h> header file. (Contributed by Victor Stinner in 45434.)

• Remove the Py_FORCE_DOUBLE() macro. It was used by the Py_IS_INFINITY() macro. (Contributed by Victor Stinner in 45440.)

• The following items are no longer available when Py_LIMITED_API is defined:

  • PyMarshal_WriteLongToFile
  • PyMarshal_WriteObjectToFile
  • PyMarshal_ReadObjectFromString
  • PyMarshal_WriteObjectToString
  • the Py_MARSHAL_VERSION macro

  These are not part of the limited API <limited-api-list>.

  (Contributed by Victor Stinner in 45474.)

• Exclude !PyWeakref_GET_OBJECT from the limited C API. It never worked since the !PyWeakReference structure is opaque in the limited C API. (Contributed by Victor Stinner in 35134.)

• Remove the PyHeapType_GET_MEMBERS() macro. It was exposed in the public C API by mistake, it must only be used by Python internally. Use the PyTypeObject.tp_members member instead. (Contributed by Victor Stinner in 40170.)

• Remove the HAVE_PY_SET_53BIT_PRECISION macro (moved to the internal C API). (Contributed by Victor Stinner in 45412.)

Notable changes in 3.11.4

tarfile

• The extraction methods in tarfile, and shutil.unpack_archive, have a new a filter argument that allows limiting tar features than may be surprising or dangerous, such as creating files outside the destination directory. See tarfile-extraction-filter for details. In Python 3.12, use without the filter argument will show a DeprecationWarning. In Python 3.14, the default will switch to 'data'. (Contributed by Petr Viktorin in 706.)

Notable changes in 3.11.5

OpenSSL

• Windows builds and macOS installers from python.org now use OpenSSL 3.0.