What's New In Python 3.11
*************************

Editor:
   Pablo Galindo Salgado

This article explains the new features in Python 3.11, compared to
3.10.

For full details, see the 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
  Faster CPython for details.

New syntax features:

* PEP 654: Exception Groups and except*

New built-in features:

* PEP 678: Exceptions can be enriched with notes

New standard library modules:

* **PEP 680**: "tomllib" — Support for parsing TOML in the Standard
  Library

Interpreter improvements:

* PEP 657: Fine-grained error locations in tracebacks

* New "-P" command line option and "PYTHONSAFEPATH" environment
  variable to disable automatically prepending potentially unsafe
  paths to "sys.path"

New typing features:

* PEP 646: Variadic generics

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

* PEP 673: Self type

* PEP 675: Arbitrary literal string type

* PEP 681: Data class transforms

Important deprecations, removals and restrictions:

* **PEP 594**: Many legacy standard library modules have been
  deprecated and will be removed in Python 3.13

* **PEP 624**: Py_UNICODE encoder APIs have been removed

* **PEP 670**: Macros converted to static inline functions


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 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 **PEP 657** for more details. (Contributed by Pablo Galindo,
Batuhan Taskaya and Ammar Askar in bpo-43950.)

Note:

  This feature requires storing column positions in Code Objects,
  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" command line option or the
  "PYTHONNODEBUGRANGES" environment variable.


PEP 654: Exception Groups and "except*"
---------------------------------------

**PEP 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*" syntax generalizes "except" to match subgroups of exception
groups.

See **PEP 654** for more details.

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


PEP 678: Exceptions can be enriched with notes
----------------------------------------------

The "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 **PEP 678** for more details.

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


Windows "py.exe" launcher improvements
--------------------------------------

The copy of the Python Launcher for Windows included with Python 3.11
has been significantly updated. It now supports company/tag syntax as
defined in **PEP 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 **PEP 484** type hints and
the "typing" module.


PEP 646: Variadic generics
--------------------------

**PEP 484** previously introduced "TypeVar", enabling creation of
generics parameterised with a single type. **PEP 646** adds
"TypeVarTuple", enabling parameterisation with an *arbitrary* number
of types. In other words, a "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 **PEP 646** for more details.

(Contributed by Matthew Rahtz in bpo-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
-------------------------------------------------------------------------

"Required" and "NotRequired" provide a straightforward way to mark
whether individual items in a "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 **PEP 655** for more details.

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


PEP 673: "Self" type
--------------------

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

Common use cases include alternative constructors provided as
"classmethod"s, and "__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))

       ...

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

See **PEP 673** for more details.

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


PEP 675: Arbitrary literal string type
--------------------------------------

The new "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 **PEP 675** for more details.

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


PEP 681: Data class transforms
------------------------------

"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"-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 **PEP 681** for more details.

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


PEP 563 may not be the future
-----------------------------

**PEP 563** Postponed Evaluation of Annotations (the "from __future__
import annotations" future statement) 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 bpo-46725 for more details.)

* Asynchronous comprehensions are now allowed inside comprehensions in
  asynchronous functions. Outer comprehensions implicitly become
  asynchronous in this case. (Contributed by Serhiy Storchaka in
  bpo-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 bpo-12022 and bpo-44471.)

* Added "object.__getstate__()", which provides the default
  implementation of the "__getstate__()" method. "copy"ing and
  "pickle"ing 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*. 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 gh-70766 for discussions of what workarounds
  such code may need. (Contributed by Serhiy Storchaka in bpo-26579.)

* Added a "-P" command line option and a "PYTHONSAFEPATH" environment
  variable, which disable the automatic prepending to "sys.path" of
  the script's directory when running a script, or the current
  directory when using "-c" and "-m". This ensures only stdlib and
  installed modules are picked up by "import", and avoids
  unintentionally or maliciously shadowing modules with those in a
  local (and typically user-writable) directory. (Contributed by
  Victor Stinner in gh-57684.)

* A ""z"" option was added to the Format Specification Mini-Language
  that coerces negative to positive zero after rounding to the format
  precision. See **PEP 682** for more details. (Contributed by John
  Belmonte in gh-90153.)

* Bytes are no longer accepted on "sys.path".  Support broke sometime
  between Python 3.2 and 3.6, with no one noticing until after Python
  3.10.0 was released. In addition, bringing back support would be
  problematic due to interactions between "-b" and
  "sys.path_importer_cache" when there is a mixture of "str" and
  "bytes" keys. (Contributed by Thomas Grainger in gh-91181.)


Other CPython Implementation Changes
====================================

* The special methods "__complex__()" for "complex" and "__bytes__()"
  for "bytes" are implemented to support the "typing.SupportsComplex"
  and "typing.SupportsBytes" protocols. (Contributed by Mark Dickinson
  and Dong-hee Na in bpo-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()". **PEP 552** hash-based
  .pyc files now use "siphash13" too. (Contributed by Inada Naoki in
  bpo-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 bpo-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
  bpo-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 bpo-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 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 bpo-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 CVE-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 documentation.  The default limit is 4300 digits
  in string form.


New Modules
===========

* "tomllib": For parsing TOML. See **PEP 680** for more details.
  (Contributed by Taneli Hukkinen in bpo-40059.)

* "wsgiref.types": **WSGI**-specific types for static type checking.
  (Contributed by Sebastian Rittau in bpo-42012.)


Improved Modules
================


asyncio
-------

* Added the "TaskGroup" class, an asynchronous context manager holding
  a group of tasks that will wait for all of them upon exit. For new
  code this is recommended over using "create_task()" and "gather()"
  directly. (Contributed by Yury Selivanov and others in gh-90908.)

* Added "timeout()", an asynchronous context manager for setting a
  timeout on asynchronous operations. For new code this is recommended
  over using "wait_for()" directly. (Contributed by Andrew Svetlov in
  gh-90927.)

* Added the "Runner" class, which exposes the machinery used by
  "run()". (Contributed by Andrew Svetlov in gh-91218.)

* Added the "Barrier" class to the synchronization primitives in the
  asyncio library, and the related "BrokenBarrierError" exception.
  (Contributed by Yves Duprat and Andrew Svetlov in gh-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 bpo-34975.)

* Added raw datagram socket functions to the event loop:
  "sock_sendto()", "sock_recvfrom()" and "sock_recvfrom_into()". These
  have implementations in "SelectorEventLoop" and "ProactorEventLoop".
  (Contributed by Alex Grönholm in bpo-46805.)

* Added "cancelling()" and "uncancel()" methods to "Task". These are
  primarily intended for internal use, notably by "TaskGroup".


contextlib
----------

* Added non parallel-safe "chdir()" context manager to change the
  current working directory and then restore it on exit. Simple
  wrapper around "chdir()". (Contributed by Filipe Laíns in bpo-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
  bpo-44674.)


datetime
--------

* Add "datetime.UTC", a convenience alias for "datetime.timezone.utc".
  (Contributed by Kabir Kwatra in gh-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 gh-80010.)


enum
----

* Renamed "EnumMeta" to "EnumType" ("EnumMeta" kept as an alias).

* Added "StrEnum", with members that can be used as (and must be)
  strings.

* Added "ReprEnum", which only modifies the "__repr__()" of members
  while returning their literal values (rather than names) for
  "__str__()" and "__format__()" (used by "str()", "format()" and
  *f-string*s).

* Changed "Enum.__format__()" (the default for "format()",
  "str.format()" and *f-string*s) to always produce the same result as
  "Enum.__str__()":  for enums inheriting from "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 "Flag" enums and the
  "FlagBoundary" enum with its options, to control how to handle out-
  of-range flag values.

* Added the "verify()" enum decorator and the "EnumCheck" enum with
  its options, to check enum classes against several specific
  constraints.

* Added the "member()" and "nonmember()" decorators, to ensure the
  decorated object is/is not converted to an enum member.

* Added the "property()" decorator, which works like "property()"
  except for enums. Use this instead of
  "types.DynamicClassAttribute()".

* Added the "global_enum()" enum decorator, which adjusts "__repr__()"
  and "__str__()" to show values as members of their module rather
  than the enum class. For example, "'re.ASCII'" for the "ASCII"
  member of "re.RegexFlag" rather than "'RegexFlag.ASCII'".

* Enhanced "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" and "Flag" so that members are now defined before
  "__init_subclass__()" is called; "dir()" now includes methods, etc.,
  from mixed-in data types.

* Changed "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 "Fraction" from string.
  (Contributed by Sergey B Kirpichev in bpo-44258.)

* "Fraction" now implements an "__int__" method, so that an
  "isinstance(some_fraction, typing.SupportsInt)" check passes.
  (Contributed by Mark Dickinson in bpo-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 bpo-46014.)


hashlib
-------

* "hashlib.blake2b()" and "hashlib.blake2s()" now prefer libb2 over
  Python's vendored copy. (Contributed by Christian Heimes in
  bpo-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
  bpo-47098.)

* Add "hashlib.file_digest()", a helper function for efficient hashing
  of files or file-like objects. (Contributed by Christian Heimes in
  gh-89313.)


IDLE and idlelib
----------------

* Apply syntax highlighting to ".pyi" files. (Contributed by Alex
  Waygood and Terry Jan Reedy in bpo-45447.)

* Include prompts when saving Shell with inputs and outputs.
  (Contributed by Terry Jan Reedy in gh-95191.)


inspect
-------

* Add "getmembers_static()" to return all members without triggering
  dynamic lookup via the descriptor protocol. (Contributed by Weipeng
  Hong in bpo-30533.)

* Add "ismethodwrapper()" for checking if the type of an object is a
  "MethodWrapperType". (Contributed by Hakan Çelik in bpo-29418.)

* Change the frame-related functions in the "inspect" module to return
  new "FrameInfo" and "Traceback" class instances (backwards
  compatible with the previous *named tuple*-like interfaces) that
  includes the extended **PEP 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 gh-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.


logging
-------

* Added "getLevelNamesMapping()" to return a mapping from logging
  level names (e.g. "'CRITICAL'") to the values of their corresponding
  Logging Levels (e.g. "50", by default). (Contributed by Andrei
  Kulakovin in gh-88024.)

* Added a "createSocket()" method to "SysLogHandler", to match
  "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 gh-88457.)


math
----

* Add "math.exp2()": return 2 raised to the power of x. (Contributed
  by Gideon Mitchell in bpo-45917.)

* Add "math.cbrt()": return the cube root of x. (Contributed by Ajith
  Ramachandran in bpo-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 bpo-44339.)

* The "math.nan" value is now always available. (Contributed by Victor
  Stinner in bpo-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 bpo-44019.)


os
--

* On Windows, "os.urandom()" now uses "BCryptGenRandom()", instead of
  "CryptGenRandom()" which is deprecated. (Contributed by Dong-hee Na
  in bpo-44611.)


pathlib
-------

* "glob()" and "rglob()" return only directories if *pattern* ends
  with a pathname components separator: "sep" or "altsep".
  (Contributed by Eisuke Kawasima in bpo-22276 and bpo-33392.)


re
--

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


shutil
------

* Add optional parameter *dir_fd* in "shutil.rmtree()". (Contributed
  by Serhiy Storchaka in bpo-46245.)


socket
------

* Add CAN Socket support for NetBSD. (Contributed by Thomas Klausner
  in bpo-30512.)

* "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 bpo-29980.)


sqlite3
-------

* You can now disable the authorizer by passing "None" to
  "set_authorizer()". (Contributed by Erlend E. Aasland in bpo-44491.)

* Collation name "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 bpo-44688.)

* "sqlite3" exceptions now include the SQLite extended error code as
  "sqlite_errorcode" and the SQLite error name as "sqlite_errorname".
  (Contributed by Aviv Palivoda, Daniel Shahaf, and Erlend E. Aasland
  in bpo-16379 and bpo-24139.)

* Add "setlimit()" and "getlimit()" to "sqlite3.Connection" for
  setting and getting SQLite limits by connection basis. (Contributed
  by Erlend E. Aasland in bpo-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 bpo-45613.)

* "sqlite3" C callbacks now use unraisable exceptions if callback
  tracebacks are enabled. Users can now register an "unraisable hook
  handler" to improve their debug experience. (Contributed by Erlend
  E. Aasland in bpo-45828.)

* Fetch across rollback no longer raises "InterfaceError". Instead we
  leave it to the SQLite library to handle these cases. (Contributed
  by Erlend E. Aasland in bpo-44092.)

* Add "serialize()" and "deserialize()" to "sqlite3.Connection" for
  serializing and deserializing databases. (Contributed by Erlend E.
  Aasland in bpo-41930.)

* Add "create_window_function()" to "sqlite3.Connection" for creating
  aggregate window functions. (Contributed by Erlend E. Aasland in
  bpo-34916.)

* Add "blobopen()" to "sqlite3.Connection". "sqlite3.Blob" allows
  incremental I/O operations on blobs. (Contributed by Aviv Palivoda
  and Erlend E. Aasland in bpo-24905.)


string
------

* Add "get_identifiers()" and "is_valid()" to "string.Template", which
  respectively return all valid placeholders, and whether any invalid
  placeholders are present. (Contributed by Ben Kehoe in gh-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 bpo-45711.)

* Add "sys.exception()" which returns the active exception instance
  (equivalent to "sys.exc_info()[1]"). (Contributed by Irit Katriel in
  bpo-46328.)

* Add the "sys.flags.safe_path" flag. (Contributed by Victor Stinner
  in gh-57684.)


sysconfig
---------

* Three new installation schemes (*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 bpo-45413.)


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 gh-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 bpo-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 bpo-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, Dong-
  hee Na, Eryk Sun and Victor Stinner in bpo-21302 and bpo-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 gh-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 bpo-44569.)

* Add "traceback.TracebackException.print()", which prints the
  formatted "TracebackException" instance to a file. (Contributed by
  Irit Katriel in bpo-33809.)


typing
------

For major changes, see New Features Related to Type Hints.

* 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 gh-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 gh-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 gh-90638.)

* "typing.TypedDict" types can now be generic. (Contributed by Samodya
  Abeysiriwardane in gh-89026.)

* "NamedTuple" types can now be generic. (Contributed by Serhiy
  Storchaka in bpo-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 gh-91154.)

* The "typing.final()" decorator now sets the "__final__" attributed
  on the decorated object. (Contributed by Jelle Zijlstra in
  gh-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 gh-89263.)

* The "__init__()" method of "Protocol" subclasses is now preserved.
  (Contributed by Adrian Garcia Badarasco in gh-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
  gh-91137.)

* Loosen runtime requirements for type annotations by removing the
  callable check in the private "typing._type_check" function.
  (Contributed by Gregory Beauregard in gh-90802.)

* "typing.get_type_hints()" now supports evaluating strings as forward
  references in PEP 585 generic aliases. (Contributed by Niklas
  Rosenstein in gh-85542.)

* "typing.get_type_hints()" no longer adds "Optional" to parameters
  with "None" as a default. (Contributed by Nikita Sobolev in
  gh-90353.)

* "typing.get_type_hints()" now supports evaluating bare stringified
  "ClassVar" annotations. (Contributed by Gregory Beauregard in
  gh-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 gh-90729.)


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

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


unittest
--------

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


venv
----

* When new Python virtual environments are created, the *venv*
  sysconfig installation scheme 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 bpo-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 bpo-47074.)


zipfile
-------

* Added support for specifying member name encoding for reading
  metadata in a "ZipFile"'s directory and file headers. (Contributed
  by Stephen J. Turnbull and Serhiy Storchaka in bpo-28080.)

* Added "ZipFile.mkdir()" for creating new directories inside ZIP
  archives. (Contributed by Sam Ezeh in gh-49083.)

* Added "stem", "suffix" and "suffixes" to "zipfile.Path".
  (Contributed by Miguel Brito in gh-88261.)


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

This section covers specific optimizations independent of the Faster
CPython project, which is covered in its own section.

* The compiler now optimizes simple printf-style % 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 bpo-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 gh-90564.)

* "sum()" is now nearly 30% faster for integers smaller than "2**30".
  (Contributed by Stefan Behnel in gh-68264.)

* Resizing lists is streamlined for the common case, speeding up
  "list.append()" by ≈15% and simple *list comprehension*s by up to
  20-30% (Contributed by Dennis Sweeney in gh-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 bpo-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 gh-91487.)

* "math" functions "comb()" and "perm()" are now ≈10 times faster for
  large arguments (with a larger speedup for larger *k*). (Contributed
  by Serhiy Storchaka in bpo-37295.)

* The "statistics" functions "mean()", "variance()" and "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 gh-90415.)

* "unicodedata.normalize()" now normalizes pure-ASCII strings in
  constant time. (Contributed by Dong-hee Na in bpo-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: Faster Startup and
Faster Runtime. Optimizations not covered by this project are listed
separately under Optimizations.


Faster Startup
--------------


Frozen imports / Static code objects
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Python caches *bytecode* in the __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 Code Objects (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 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 bpo-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 bpo-45256.)


PEP 659: Specializing Adaptive Interpreter
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

**PEP 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 **PEP 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   | Contributor(s)      |
|                 |                      |                                                         | (up to)             |                     |
|=================|======================|=========================================================|=====================|=====================|
| Binary          | "x + x"  "x - x"  "x | Binary add, multiply and subtract for common types such | 10%                 | Mark Shannon, Dong- |
| operations      | * x"                 | as "int", "float" and "str" take custom fast paths for  |                     | hee Na, Brandt      |
|                 |                      | their underlying types.                                 |                     | Bucher, Dennis      |
|                 |                      |                                                         |                     | Sweeney             |
+-----------------+----------------------+---------------------------------------------------------+---------------------+---------------------+
| Subscript       | "a[i]"               | Subscripting container types such as "list", "tuple"    | 10-25%              | Irit Katriel, Mark  |
|                 |                      | and "dict" directly index the underlying data           |                     | Shannon             |
|                 |                      | structures.  Subscripting custom "__getitem__()" is     |                     |                     |
|                 |                      | also inlined similar to Inlined Python function calls.  |                     |                     |
+-----------------+----------------------+---------------------------------------------------------+---------------------+---------------------+
| 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 | 20%                 | Mark Shannon, Ken   |
|                 |                      | "len()" and "str" directly call their underlying C      |                     | Jin                 |
|                 |                      | version. This avoids going through the internal calling |                     |                     |
|                 |                      | convention.                                             |                     |                     |
+-----------------+----------------------+---------------------------------------------------------+---------------------+---------------------+
| Load global     | "print"  "len"       | The object's index in the globals/builtins namespace is | [1]                 | Mark Shannon        |
| variable        |                      | cached. Loading globals and builtins require zero       |                     |                     |
|                 |                      | namespace lookups.                                      |                     |                     |
+-----------------+----------------------+---------------------------------------------------------+---------------------+---------------------+
| Load attribute  | "o.attr"             | Similar to loading global variables. The attribute's    | [2]                 | Mark Shannon        |
|                 |                      | index inside the class/object's namespace is cached. In |                     |                     |
|                 |                      | most cases, attribute loading will require zero         |                     |                     |
|                 |                      | namespace lookups.                                      |                     |                     |
+-----------------+----------------------+---------------------------------------------------------+---------------------+---------------------+
| Load methods    | "o.meth()"           | The actual address of the method is cached. Method      | 10-20%              | Ken Jin, Mark       |
| for call        |                      | loading now has no namespace lookups -- even for        |                     | Shannon             |
|                 |                      | classes with long inheritance chains.                   |                     |                     |
+-----------------+----------------------+---------------------------------------------------------+---------------------+---------------------+
| 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    | 8%                  | Brandt Bucher       |
|                 |                      | "tuple". Avoids internal calling convention.            |                     |                     |
+-----------------+----------------------+---------------------------------------------------------+---------------------+---------------------+

[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 bpo-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 bpo-45340 and bpo-40116.)

* "Zero-cost" exceptions are implemented, eliminating the cost of
  "try" statements when no exception is raised. (Contributed by Mark
  Shannon in bpo-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 bpo-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 gh-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* added in **PEP 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" "KW_NAMES" "PRECALL"         | Decouples argument shifting for methods   |
| "CALL_METHOD"                        | "PUSH_NULL"                         | from handling of keyword arguments;       |
|                                      |                                     | allows better specialization of calls     |
+--------------------------------------+-------------------------------------+-------------------------------------------+
| "DUP_TOP" "DUP_TOP_TWO" "ROT_TWO"    | "COPY" "SWAP"                       | Stack manipulation instructions           |
| "ROT_THREE" "ROT_FOUR" "ROT_N"       |                                     |                                           |
+--------------------------------------+-------------------------------------+-------------------------------------------+
| "JUMP_IF_NOT_EXC_MATCH"              | "CHECK_EXC_MATCH"                   | Now performs check but doesn't jump       |
+--------------------------------------+-------------------------------------+-------------------------------------------+
| "JUMP_ABSOLUTE" "POP_JUMP_IF_FALSE"  | "JUMP_BACKWARD"                     | See [3]; "TRUE", "FALSE", "NONE" and      |
| "POP_JUMP_IF_TRUE"                   | "POP_JUMP_BACKWARD_IF_*"            | "NOT_NONE" variants for each direction    |
|                                      | "POP_JUMP_FORWARD_IF_*"             |                                           |
+--------------------------------------+-------------------------------------+-------------------------------------------+
| "SETUP_WITH" "SETUP_ASYNC_WITH"      | "BEFORE_WITH"                       | "with" block setup                        |
+--------------------------------------+-------------------------------------+-------------------------------------------+

[3] 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
  gh-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.


Language/Builtins
-----------------

* Chaining "classmethod" descriptors (introduced in bpo-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
  gh-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
  gh-81548.)

* The delegation of "int()" to "__trunc__()" is now deprecated.
  Calling "int(a)" when "type(a)" implements "__trunc__()" but not
  "__int__()" or "__index__()" now raises a "DeprecationWarning".
  (Contributed by Zackery Spytz in bpo-44977.)


Modules
-------

* **PEP 594** led to the deprecations of the following modules slated
  for removal in Python 3.13:

  +-----------------------+-----------------------+-----------------------+-----------------------+-----------------------+
  | "aifc"                | "chunk"               | "msilib"              | "pipes"               | "telnetlib"           |
  +-----------------------+-----------------------+-----------------------+-----------------------+-----------------------+
  | "audioop"             | "crypt"               | "nis"                 | "sndhdr"              | "uu"                  |
  +-----------------------+-----------------------+-----------------------+-----------------------+-----------------------+
  | "cgi"                 | "imghdr"              | "nntplib"             | "spwd"                | "xdrlib"              |
  +-----------------------+-----------------------+-----------------------+-----------------------+-----------------------+
  | "cgitb"               | "mailcap"             | "ossaudiodev"         | "sunau"               |                       |
  +-----------------------+-----------------------+-----------------------+-----------------------+-----------------------+

  (Contributed by Brett Cannon in bpo-47061 and Victor Stinner in
  gh-68966.)

* The "asynchat", "asyncore" and  "smtpd" modules have been deprecated
  since at least Python 3.6. Their documentation and deprecation
  warnings have now been updated to note they will be removed in
  Python 3.12. (Contributed by Hugo van Kemenade in bpo-47022.)

* The "lib2to3" package and 2to3 tool are now deprecated and may not
  be able to parse Python 3.10 or newer. See **PEP 617**, introducing
  the new PEG parser, for details. (Contributed by Victor Stinner in
  bpo-40360.)

* Undocumented modules "sre_compile", "sre_constants" and "sre_parse"
  are now deprecated. (Contributed by Serhiy Storchaka in bpo-47152.)


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 bpo-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 bpo-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 3.13. Use "locale.setlocale()",
  "locale.getpreferredencoding(False)" and "locale.getlocale()"
  functions instead. (Contributed by Victor Stinner in gh-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 gh-90817.)

* Stricter rules will now be applied for numerical group references
  and group names in regular expressions. 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 gh-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 gh-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 bpo-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
  gh-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 gh-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 Dong-hee Na in bpo-42255.)

* The behavior of returning a value from a "TestCase" and
  "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 "TestLoader" methods instead:

  * "unittest.TestLoader.loadTestsFromModule()"

  * "unittest.TestLoader.loadTestsFromTestCase()"

  * "unittest.TestLoader.getTestCaseNames()"

  (Contributed by Erlend E. Aasland in bpo-5846.)

* "usageExit()" is marked deprecated, to be removed in 3.13.
  (Contributed by Carlos Damázio in gh-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.

* The "asynchat" module

* The "asyncore" module

* The entire distutils package

* The "imp" module

* The "typing.io" namespace

* The "typing.re" 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.BuiltinLoader.module_repr()"

* "importlib.machinery.FileFinder.find_loader()"

* "importlib.machinery.FileFinder.find_module()"

* "importlib.machinery.FrozenImporter.find_module()"

* "importlib.machinery.FrozenLoader.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.

* 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 bpo-43216.)

* Removed "asyncio.coroutines.CoroWrapper" used for wrapping legacy
  generator-based coroutine objects in the debug mode. (Contributed by
  Illia Volochii in bpo-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 bpo-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 bpo-45085.)

* Removed the "distutils" "bdist_msi" command deprecated in Python
  3.9. Use "bdist_wheel" (wheel packages) instead. (Contributed by
  Hugo van Kemenade in bpo-45124.)

* Removed the "__getitem__()" methods of
  "xml.dom.pulldom.DOMEventStream", "wsgiref.util.FileWrapper" and
  "fileinput.FileInput", deprecated since Python 3.9. (Contributed by
  Hugo van Kemenade in bpo-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 Dong-hee Na
  and Serhiy Storchaka in bpo-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()" method instead.

  (Contributed by Hugo van Kemenade in bpo-45320.)

* Removed the "__class_getitem__()" method from "pathlib.PurePath",
  because it was not used and added by mistake in previous versions.
  (Contributed by Nikita Sobolev in bpo-46483.)

* Removed the "MailmanProxy" class in the "smtpd" module, as it is
  unusable without the external "mailman" package. (Contributed by
  Dong-hee Na in bpo-35800.)

* Removed the deprecated "split()" method of "_tkinter.TkappType".
  (Contributed by Erlend E. Aasland in bpo-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 bpo-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 bpo-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.

* "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 to these functions controls
  how universal newlines work. (Contributed by Victor Stinner in
  bpo-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 gh-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
  bpo-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 bpo-46659.)

* The "pdb" module now reads the ".pdbrc" configuration file with the
  "'UTF-8'" encoding. (Contributed by Srinivas Reddy Thatiparthy (శ్
  రీనివాస్  రెడ్డి తాటిపర్తి) in bpo-41137.)

* The *population* parameter of "random.sample()" must be a sequence,
  and automatic conversion of "set"s to "list"s is no longer
  supported. Also, if the sample size is larger than the population
  size, a "ValueError" is raised. (Contributed by Raymond Hettinger in
  bpo-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" Regular Expression 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 bpo-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 bpo-35859.)


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

* CPython now has **PEP 11** **Tier 3 support** 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 gh-84461 and WASI contributed by
  Christian Heimes in gh-90473; platforms promoted in gh-95085)

* Building CPython now requires:

  * A C11 compiler and standard library. Optional C11 features are not
    required. (Contributed by Victor Stinner in bpo-46656, bpo-45440
    and bpo-46640.)

  * Support for IEEE 754 floating point numbers. (Contributed by
    Victor Stinner in bpo-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 bpo-46656.)

* The "tkinter" package now requires Tcl/Tk version 8.5.12 or newer.
  (Contributed by Serhiy Storchaka in bpo-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 bpo-45847, bpo-45747, and bpo-45763.)

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

* CPython can now be built with the ThinLTO option via passing "thin"
  to "--with-lto", i.e. "--with-lto=thin". (Contributed by Dong-hee Na
  and Brett Holman in bpo-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 bpo-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
  bpo-45548, bpo-45570, bpo-45571, and bpo-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 bpo-45569.)


C API Changes
=============


New Features
------------

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

* Add a new "PyType_GetQualName()" function to get type's qualified
  name. (Contributed by Hai Shi in bpo-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 bpo-43760.)

* Added the "Py_Version" constant which bears the same value as
  "PY_VERSION_HEX". (Contributed by  Gabriele N. Tornetta in
  bpo-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()"

  * "bf_getbuffer" and "bf_releasebuffer" type slots

  (Contributed by Christian Heimes in bpo-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 bpo-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 bpo-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 bpo-46343.)

* Added the "PyConfig.safe_path" member. (Contributed by Victor
  Stinner in gh-57684.)


Porting to Python 3.11
----------------------

* Some macros have been converted to static inline functions to avoid
  macro pitfalls. The change should be mostly transparent to users, as
  the replacement functions will cast their arguments to the expected
  types to avoid compiler warnings due to static type checks. However,
  when the limited C API is set to >=3.11, these casts are not done,
  and callers will need to cast arguments to their expected types. See
  **PEP 670** for more details. (Contributed by Victor Stinner and
  Erlend E. Aasland in gh-89653.)

* "PyErr_SetExcInfo()" no longer uses the "type" and "traceback"
  arguments, the interpreter now derives those values from the
  exception instance (the "value" argument). The function still steals
  references of all three arguments. (Contributed by Irit Katriel in
  bpo-45711.)

* "PyErr_GetExcInfo()" now derives the "type" and "traceback" fields
  of the result from the exception instance (the "value" field).
  (Contributed by Irit Katriel in bpo-45711.)

* "_frozen" has a new "is_package" field to indicate whether or not
  the frozen module is a package.  Previously, a negative value in the
  "size" field was the indicator.  Now only non-negative values be
  used for "size". (Contributed by Kumar Aditya in bpo-46608.)

* "_PyFrameEvalFunction()" now takes "_PyInterpreterFrame*" as its
  second parameter, instead of "PyFrameObject*". See **PEP 523** for
  more details of how to use this function pointer type.

* "PyCode_New()" and "PyCode_NewWithPosOnlyArgs()" now take an
  additional "exception_table" argument. Using these functions should
  be avoided, if at all possible. To get a custom code object: create
  a code object using the compiler, then get a modified version with
  the "replace" method.

* "PyCodeObject" no longer has the "co_code", "co_varnames",
  "co_cellvars" and "co_freevars" fields.  Instead, use
  "PyCode_GetCode()", "PyCode_GetVarnames()", "PyCode_GetCellvars()"
  and "PyCode_GetFreevars()" respectively to access them via the C
  API. (Contributed by Brandt Bucher in bpo-46841 and Ken Jin in
  gh-92154 and gh-94936.)

* The old trashcan macros
  ("Py_TRASHCAN_SAFE_BEGIN"/"Py_TRASHCAN_SAFE_END") are now
  deprecated. 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.

  To support older Python versions in the same codebase, you can
  define the following macros and use them throughout the code
  (credit: these were copied from the "mypy" codebase):

     #if PY_VERSION_HEX >= 0x03080000
     #  define CPy_TRASHCAN_BEGIN(op, dealloc) Py_TRASHCAN_BEGIN(op, dealloc)
     #  define CPy_TRASHCAN_END(op) Py_TRASHCAN_END
     #else
     #  define CPy_TRASHCAN_BEGIN(op, dealloc) Py_TRASHCAN_SAFE_BEGIN(op)
     #  define CPy_TRASHCAN_END(op) Py_TRASHCAN_SAFE_END(op)
     #endif

* The "PyType_Ready()" function now raises an error if a type is
  defined with the "Py_TPFLAGS_HAVE_GC" flag set but has no traverse
  function ("PyTypeObject.tp_traverse"). (Contributed by Victor
  Stinner in bpo-44263.)

* Heap types with the "Py_TPFLAGS_IMMUTABLETYPE" flag can now inherit
  the **PEP 590** vectorcall protocol.  Previously, this was only
  possible for static types. (Contributed by Erlend E. Aasland in
  bpo-43908)

* Since "Py_TYPE()" is changed to a inline static function,
  "Py_TYPE(obj) = new_type" must be replaced with "Py_SET_TYPE(obj,
  new_type)": see the "Py_SET_TYPE()" function (available since Python
  3.9). For backward compatibility, this macro can be used:

     #if PY_VERSION_HEX < 0x030900A4 && !defined(Py_SET_TYPE)
     static inline void _Py_SET_TYPE(PyObject *ob, PyTypeObject *type)
     { ob->ob_type = type; }
     #define Py_SET_TYPE(ob, type) _Py_SET_TYPE((PyObject*)(ob), type)
     #endif

  (Contributed by Victor Stinner in bpo-39573.)

* Since "Py_SIZE()" is changed to a inline static function,
  "Py_SIZE(obj) = new_size" must be replaced with "Py_SET_SIZE(obj,
  new_size)": see the "Py_SET_SIZE()" function (available since Python
  3.9). For backward compatibility, this macro can be used:

     #if PY_VERSION_HEX < 0x030900A4 && !defined(Py_SET_SIZE)
     static inline void _Py_SET_SIZE(PyVarObject *ob, Py_ssize_t size)
     { ob->ob_size = size; }
     #define Py_SET_SIZE(ob, size) _Py_SET_SIZE((PyVarObject*)(ob), size)
     #endif

  (Contributed by Victor Stinner in bpo-39573.)

* "<Python.h>" no longer includes the header files "<stdlib.h>",
  "<stdio.h>", "<errno.h>" and "<string.h>" when the "Py_LIMITED_API"
  macro is set to "0x030b0000" (Python 3.11) or higher. C extensions
  should explicitly include the header files after "#include
  <Python.h>". (Contributed by Victor Stinner in bpo-45434.)

* The non-limited API files "cellobject.h", "classobject.h", "code.h",
  "context.h", "funcobject.h", "genobject.h" and "longintrepr.h" have
  been moved to the "Include/cpython" directory. Moreover, the
  "eval.h" header file was removed. These files must not be included
  directly, as they are already included in "Python.h": Include Files.
  If they have been included directly, consider including "Python.h"
  instead. (Contributed by Victor Stinner in bpo-35134.)

* The "PyUnicode_CHECK_INTERNED()" macro has been excluded from the
  limited C API. It was never usable there, because it used internal
  structures which are not available in the limited C API.
  (Contributed by Victor Stinner in bpo-46007.)

* The following frame functions and type are now directly available
  with "#include <Python.h>", it's no longer needed to add "#include
  <frameobject.h>":

  * "PyFrame_Check()"

  * "PyFrame_GetBack()"

  * "PyFrame_GetBuiltins()"

  * "PyFrame_GetGenerator()"

  * "PyFrame_GetGlobals()"

  * "PyFrame_GetLasti()"

  * "PyFrame_GetLocals()"

  * "PyFrame_Type"

  (Contributed by Victor Stinner in gh-93937.)

* The "PyFrameObject" structure members have been removed from the
  public C API.

  While the documentation notes that the "PyFrameObject" fields are
  subject to change at any time, they have been stable for a long time
  and were used in several popular extensions.

  In Python 3.11, the frame struct was reorganized to allow
  performance optimizations. Some fields were removed entirely, as
  they were details of the old implementation.

  "PyFrameObject" fields:

  * "f_back": use "PyFrame_GetBack()".

  * "f_blockstack": removed.

  * "f_builtins": use "PyFrame_GetBuiltins()".

  * "f_code": use "PyFrame_GetCode()".

  * "f_gen": use "PyFrame_GetGenerator()".

  * "f_globals": use "PyFrame_GetGlobals()".

  * "f_iblock": removed.

  * "f_lasti": use "PyFrame_GetLasti()". Code using "f_lasti" with
    "PyCode_Addr2Line()" should use "PyFrame_GetLineNumber()" instead;
    it may be faster.

  * "f_lineno": use "PyFrame_GetLineNumber()"

  * "f_locals": use "PyFrame_GetLocals()".

  * "f_stackdepth": removed.

  * "f_state": no public API (renamed to "f_frame.f_state").

  * "f_trace": no public API.

  * "f_trace_lines": use "PyObject_GetAttrString((PyObject*)frame,
    "f_trace_lines")".

  * "f_trace_opcodes": use "PyObject_GetAttrString((PyObject*)frame,
    "f_trace_opcodes")".

  * "f_localsplus": no public API (renamed to "f_frame.localsplus").

  * "f_valuestack": removed.

  The Python frame object is now created lazily. A side effect is that
  the "f_back" member must not be accessed directly, since its value
  is now also computed lazily. The "PyFrame_GetBack()" function must
  be called instead.

  Debuggers that accessed the "f_locals" directly *must* call
  "PyFrame_GetLocals()" instead. They no longer need to call
  "PyFrame_FastToLocalsWithError()" or "PyFrame_LocalsToFast()", in
  fact they should not call those functions. The necessary updating of
  the frame is now managed by the virtual machine.

  Code defining "PyFrame_GetCode()" on Python 3.8 and older:

     #if PY_VERSION_HEX < 0x030900B1
     static inline PyCodeObject* PyFrame_GetCode(PyFrameObject *frame)
     {
         Py_INCREF(frame->f_code);
         return frame->f_code;
     }
     #endif

  Code defining "PyFrame_GetBack()" on Python 3.8 and older:

     #if PY_VERSION_HEX < 0x030900B1
     static inline PyFrameObject* PyFrame_GetBack(PyFrameObject *frame)
     {
         Py_XINCREF(frame->f_back);
         return frame->f_back;
     }
     #endif

  Or use the pythoncapi_compat project to get these two functions on
  older Python versions.

* Changes of the "PyThreadState" structure members:

  * "frame": removed, use "PyThreadState_GetFrame()" (function added
    to Python 3.9 by bpo-40429). Warning: the function returns a
    *strong reference*, need to call "Py_XDECREF()".

  * "tracing": changed, use "PyThreadState_EnterTracing()" and
    "PyThreadState_LeaveTracing()" (functions added to Python 3.11 by
    bpo-43760).

  * "recursion_depth": removed, use "(tstate->recursion_limit -
    tstate->recursion_remaining)" instead.

  * "stackcheck_counter": removed.

  Code defining "PyThreadState_GetFrame()" on Python 3.8 and older:

     #if PY_VERSION_HEX < 0x030900B1
     static inline PyFrameObject* PyThreadState_GetFrame(PyThreadState *tstate)
     {
         Py_XINCREF(tstate->frame);
         return tstate->frame;
     }
     #endif

  Code defining "PyThreadState_EnterTracing()" and
  "PyThreadState_LeaveTracing()" on Python 3.10 and older:

     #if PY_VERSION_HEX < 0x030B00A2
     static inline void PyThreadState_EnterTracing(PyThreadState *tstate)
     {
         tstate->tracing++;
     #if PY_VERSION_HEX >= 0x030A00A1
         tstate->cframe->use_tracing = 0;
     #else
         tstate->use_tracing = 0;
     #endif
     }

     static inline void PyThreadState_LeaveTracing(PyThreadState *tstate)
     {
         int use_tracing = (tstate->c_tracefunc != NULL || tstate->c_profilefunc != NULL);
         tstate->tracing--;
     #if PY_VERSION_HEX >= 0x030A00A1
         tstate->cframe->use_tracing = use_tracing;
     #else
         tstate->use_tracing = use_tracing;
     #endif
     }
     #endif

  Or use the pythoncapi-compat project to get these functions on old
  Python functions.

* Distributors are encouraged to build Python with the optimized
  Blake2 library libb2.

* 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".

* "PyConfig_Read()" no longer calculates the initial search path, and
  will not fill any values into "PyConfig.module_search_paths". To
  calculate default paths and then modify them, finish initialization
  and use "PySys_GetObject()" to retrieve "sys.path" as a Python list
  object and modify it directly.


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 instead (**PEP 587**). (Contributed by Victor Stinner
  in gh-88279.)

* Deprecate the "ob_shash" member of the "PyBytesObject". Use
  "PyObject_Hash()" instead. (Contributed by Inada Naoki in
  bpo-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 bpo-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 bpo-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 bpo-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 bpo-45434.)

* Remove the "Py_FORCE_DOUBLE()" macro. It was used by the
  "Py_IS_INFINITY()" macro. (Contributed by Victor Stinner in
  bpo-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.

  (Contributed by Victor Stinner in bpo-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 bpo-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 bpo-40170.)

* Remove the "HAVE_PY_SET_53BIT_PRECISION" macro (moved to the
  internal C API). (Contributed by Victor Stinner in bpo-45412.)

* Remove the "Py_UNICODE" encoder APIs, as they have been deprecated
  since Python 3.3, are little used and are inefficient relative to
  the recommended alternatives.

  The removed functions are:

  * "PyUnicode_Encode()"

  * "PyUnicode_EncodeASCII()"

  * "PyUnicode_EncodeLatin1()"

  * "PyUnicode_EncodeUTF7()"

  * "PyUnicode_EncodeUTF8()"

  * "PyUnicode_EncodeUTF16()"

  * "PyUnicode_EncodeUTF32()"

  * "PyUnicode_EncodeUnicodeEscape()"

  * "PyUnicode_EncodeRawUnicodeEscape()"

  * "PyUnicode_EncodeCharmap()"

  * "PyUnicode_TranslateCharmap()"

  * "PyUnicode_EncodeDecimal()"

  * "PyUnicode_TransformDecimalToASCII()"

  See **PEP 624** for details and **migration guidance**. (Contributed
  by Inada Naoki in bpo-44029.)
