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

Release:
   3.11.0a5

Date:
   March 07, 2022

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

For full details, see the changelog.

Note:

  Prerelease users should be aware that this document is currently in
  draft form. It will be updated substantially as Python 3.11 moves
  towards release, so it's worth checking back even after reading
  earlier versions.


Summary -- Release highlights
=============================

PEP-654: Exception Groups and "except*". (Contributed by Irit Katriel
in bpo-45292.) PEP-673: "Self" Type. (Contributed by James Hilton-
Balfe and Pradeep Kumar in bpo-30924.)


New Features
============


Enhanced 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 dictionary 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

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 of disk usage of compiled Python
  files or interpreter memory usage. To avoid storing the extra
  information and/or deactivate printing the extra traceback
  information, the "-X" "no_debug_ranges" command line flag or the
  "PYTHONNODEBUGRANGES" environment variable can be used.


Column information for code objects
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The information used by the enhanced traceback feature is made
available as a general API that can be used to correlate bytecode
instructions with source code. This information can be retrieved
using:

* The "codeobject.co_positions()" method in Python.

* The "PyCode_Addr2Location()" function in the C-API.

The "-X" "no_debug_ranges" option and the environment variable
"PYTHONNODEBUGRANGES" can be used to disable this feature.

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


Exceptions can be enriched with a string "__note__"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The "__note__" field was added to "BaseException". It is "None" by
default but can be set to a string which is added to the exception's
traceback. (Contributed by Irit Katriel in bpo-45607.)


Other Language Changes
======================

* Starred expressions can 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. (Contributed by Serhiy Storchaka in bpo-33346.)

* A "TypeError" is now raised instead of an "AttributeError" in
  "contextlib.ExitStack.enter_context()" and
  "contextlib.AsyncExitStack.enter_async_context()" for objects which
  do not support the *context manager* or *asynchronous context
  manager* protocols correspondingly. (Contributed by Serhiy Storchaka
  in bpo-44471.)

* A "TypeError" is now raised instead of an "AttributeError" in "with"
  and "async with" statements for objects which do not support the
  *context manager* or *asynchronous context manager* protocols
  correspondingly. (Contributed by Serhiy Storchaka in bpo-12022.)


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

* Special methods "complex.__complex__()" and "bytes.__bytes__()" are
  implemented to support "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 algorithms. It's has
  similar security properties as "siphash24" but it is slightly faster
  for long inputs. "str", "bytes", and some other types now use it as
  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 (a.k.a
  exc_info, or _PyErr_StackItem) now has only the "exc_value" field,
  "exc_type" and "exc_traceback" have been removed as their values can
  be derived from "exc_value". (Contributed by Irit Katriel in
  bpo-45711.)

* A new command line option for the Windows installer "AppendPath" has
  beend added. It behaves similiar to "PrependPath" but appends the
  install and scripts directories instead of prepending it.
  (Contributed by Bastian Neuburger in bpo-44934.)


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

* None yet.


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


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.)


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

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


inspect
-------

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

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


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.)


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.)


socket
------

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


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.)


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.)


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.)


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

* The Unicode database has been updated to version 14.0.0.
  (bpo-45190).


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.


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

* Compiler now optimizes simple C-style formatting with literal format
  containing only format codes "%s", "%r" and "%a" and makes it as
  fast as corresponding f-string expression. (Contributed by Serhiy
  Storchaka in bpo-28307.)

* "Zero-cost" exceptions are implemented. The cost of "try" statements
  is almost eliminated when no exception is raised. (Contributed by
  Mark Shannon in bpo-40222.)

* Method calls with keywords are now faster due to bytecode changes
  which avoid creating bound method instances. Previously, this
  optimization was applied only to method calls with purely positional
  arguments. (Contributed by Ken Jin and Mark Shannon in bpo-26110,
  based on ideas implemented in PyPy.)

* Pure ASCII strings are now normalized in constant time by
  "unicodedata.normalize()". (Contributed by Dong-hee Na in
  bpo-44987.)

* "math" functions "comb()" and "perm()" are now up to 10 times or
  more faster for large arguments (the speed up is larger for larger
  *k*). (Contributed by Serhiy Storchaka in bpo-37295.)

* Dict don't store hash value when all inserted keys are Unicode
  objects. This reduces dict size. For example,
  "sys.getsizeof(dict.fromkeys("abcdefg"))" becomes 272 bytes from 352
  bytes on 64bit platform. (Contributed by Inada Naoki in bpo-46845.)


CPython bytecode changes
========================

* Replaced all numeric "BINARY_*" and "INPLACE_*" instructions with a
  single "BINARY_OP" implementation.

* Replaced the three call instructions: "CALL_FUNCTION",
  "CALL_FUNCTION_KW" and "CALL_METHOD" with "PUSH_NULL", "PRECALL",
  "CALL", and "KW_NAMES". This decouples the argument shifting for
  methods from the handling of keyword arguments and allows better
  specialization of calls.

* Removed "COPY_DICT_WITHOUT_KEYS" and "GEN_START".

* "MATCH_CLASS" and "MATCH_KEYS" no longer push an additional boolean
  value indicating whether the match succeeded or failed. Instead,
  they indicate failure with "None" (where a tuple of extracted values
  would otherwise be).

* Replace several stack manipulation instructions ("DUP_TOP",
  "DUP_TOP_TWO", "ROT_TWO", "ROT_THREE", "ROT_FOUR", and "ROT_N") with
  new "COPY" and "SWAP" instructions.

* Add "POP_JUMP_IF_NOT_NONE" and "POP_JUMP_IF_NONE" opcodes to speed
  up conditional jumps.

* "JUMP_IF_NOT_EXC_MATCH" no longer pops the active exception.


Deprecated
==========

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

* "webbrowser.MacOSX" is deprecated and will be removed in Python
  3.13. It is untested and undocumented and also 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 "unittest" functions, scheduled for removal
  in Python 3.13:

  * "unittest.findTestCases()"

  * "unittest.makeSuite()"

  * "unittest.getTestCaseNames()"

  Use "TestLoader" method instead:

  * "unittest.TestLoader.loadTestsFromModule()"

  * "unittest.TestLoader.loadTestsFromTestCase()"

  * "unittest.TestLoader.getTestCaseNames()"

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

* The "turtle.RawTurtle.settiltangle()" is deprecated since Python
  3.1, it now emits a deprecation warning and will be removed in
  Python 3.13. Use "turtle.RawTurtle.tiltangle()" instead (it was
  earlier incorrectly marked as deprecated, its docstring is now
  corrected). (Contributed by Hugo van Kemenade in bpo-45837.)

* 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.)

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

  * the "configparser.SafeConfigParser" class

  * the "configparser.ParsingError.filename" property

  * the "configparser.ParsingError.readfp()" method

  (Contributed by Hugo van Kemenade in bpo-45173.)

* 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 bpo-46659.)


Removed
=======

* "smtpd.MailmanProxy" is now removed as it is unusable without an
  external module, "mailman". (Contributed by Dong-hee Na in
  bpo-35800.)

* The "binhex" module, deprecated in Python 3.9, is now removed. The
  following "binascii" functions, deprecated in Python 3.9, are now
  also removed:

  * "a2b_hqx()", "b2a_hqx()";

  * "rlecode_hqx()", "rledecode_hqx()".

  The "binascii.crc_hqx()" function remains available.

  (Contributed by Victor Stinner in bpo-45085.)

* The distutils "bdist_msi" command, deprecated in Python 3.9, is now
  removed. Use "bdist_wheel" (wheel packages) instead. (Contributed by
  Hugo van Kemenade in bpo-45124.)

* 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 "__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.)

* The following deprecated functions and methods are removed in the
  "gettext" module: "lgettext()", "ldgettext()", "lngettext()" and
  "ldngettext()".

  Function "bind_textdomain_codeset()", methods "output_charset()" and
  "set_output_charset()", and the *codeset* parameter of functions
  "translation()" and "install()" are also removed, since they are
  only used for the "l*gettext()" functions. (Contributed by Dong-hee
  Na and Serhiy Storchaka in bpo-44235.)

* 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.)

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

* Removed the deprecated "split()" method of "_tkinter.TkappType".
  (Contributed by Erlend E. Aasland in bpo-38371.)

* 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 and "Signature" object directly.

  * the undocumented "Signature.from_builtin" and
    "Signature.from_function" functions, deprecated since Python 3.5;
    use the "Signature.from_callable()" method instead.

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

* Remove 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.)

* Remove "__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.)

* Remove 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.)


Porting to Python 3.11
======================

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


Changes in the Python API
-------------------------

* Prohibited passing non-"concurrent.futures.ThreadPoolExecutor"
  executors to "loop.set_default_executor()" following a deprecation
  in Python 3.8. (Contributed by Illia Volochii in bpo-43234.)

* "open()", "io.open()", "codecs.open()" and "fileinput.FileInput" no
  longer accept "'U'" ("universal newline") in the file mode. This
  flag was deprecated since Python 3.3. In Python 3, the "universal
  newline" is used by default when a file is open in text mode.  The
  newline parameter of "open()" controls how universal newlines works.
  (Contributed by Victor Stinner in bpo-37330.)

* 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.)

* When sorting using tuples as keys, the order of the result may
  differ from earlier releases if the tuple elements don't define a
  total ordering (see Value comparisons for information on total
  ordering).  It's generally true that the result of sorting simply
  isn't well-defined in the absence of a total ordering on list
  elements.

* "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.)


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

* Building Python now requires a C11 compiler without optional C11
  features. (Contributed by Victor Stinner in bpo-46656.)

* CPython can now be built with the ThinLTO option via "--with-
  lto=thin". (Contributed by Dong-hee Na and Brett Holman in
  bpo-44340.)

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

* Building Python now requires a C99 "<math.h>" header file providing
  the following functions: "copysign()", "hypot()", "isfinite()",
  "isinf()", "isnan()", "round()". (Contributed by Victor Stinner in
  bpo-45440.)

* Building Python now requires a C99 "<math.h>" header file providing
  a "NAN" constant, or the "__builtin_nan()" built-in function.
  (Contributed by Victor Stinner in bpo-46640.)

* Building Python now requires support for floating point Not-a-Number
  (NaN): remove the "Py_NO_NAN" macro. (Contributed by Victor Stinner
  in bpo-46656.)

* 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 main binary
  or library. (Contributed by Brett Cannon and Christian Heimes in
  bpo-45548, bpo-45570, bpo-45571, and bpo-43974.)

* Build dependencies, compiler flags, and linker flags for most stdlib
  extension modules are now detected by **configure**. libffi, libnsl,
  libsqlite3, zlib, bzip2, liblzma, libcrypt, and uuid flags are
  detected by "pkg-config" (when available). (Contributed by Christian
  Heimes and Erlend Egeberg Aasland in bpo-bpo-45847, bpo-45747, and
  bpo-45763.)

* CPython now has experimental support for cross compiling to
  WebAssembly platform "wasm32-emscripten". The effort is inspired by
  previous work like Pyodide. (Contributed by Christian Heimes and
  Ethan Smith in bpo-40280.)

* 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
=============

* "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.)


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()"

  * "PyBuffer_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.)


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

* 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_MAJOR_VERSION >= 3 && PY_MINOR_VERSION >= 8
     #  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",
  "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 "PyFrameObject" structure member has been moved to the internal
  C API headers.

  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 "PyObject_GetAttrString((PyObject*)frame,
    "f_builtins")".

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

  * "f_gen": removed.

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

  * "f_iblock": removed.

  * "f_lasti": use "PyObject_GetAttrString((PyObject*)frame,
    "f_lasti")". Code using "f_lasti" with "PyCode_Addr2Line()" must
    use "PyFrame_GetLineNumber()" instead.

  * "f_lineno": use "PyFrame_GetLineNumber()"

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

  * "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")" (it also be modified).

  * "f_trace_opcodes": use "PyObject_GetAttrString((PyObject*)frame,
    "f_trace_opcodes")" (it also be modified).

  * "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.

  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.


Deprecated
----------

* Deprecate the following functions to configure the Python
  initialization:

  * "PySys_AddWarnOptionUnicode()"

  * "PySys_AddWarnOption()"

  * "PySys_AddXOption()"

  * "PySys_HasWarnOptions()"

  * "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 bpo-44113.)

* Deprecate the "ob_shash" member of the "PyBytesObject". Use
  "PyObject_Hash()" instead. (Contributed by Inada Naoki in
  bpo-46864.)


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.)
