What’s New In Python 3.11

Release

3.11.0a6

Date

April 05, 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

New syntax features:

  • PEP 654: Exception Groups and except*. (Contributed by Irit Katriel in bpo-45292.)

New typing features:

  • 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 -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

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 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 been added. It behaves similiar to PrependPath but appends the install and scripts directories instead of prepending them. (Contributed by Bastian Neuburger in bpo-44934.)

New Modules

  • A new module, tomllib, was added for parsing TOML. (Contributed by Taneli Hukkinen in bpo-40059.)

Improved Modules

asyncio

  • Add raw datagram socket functions to the event loop: sock_sendto(), sock_recvfrom() and sock_recvfrom_into(). (Contributed by Alex Grönholm in bpo-46805.)

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.)

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.)

IDLE and idlelib

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

inspect

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.)

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

socket

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

sqlite3

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.)

sysconfig

  • Two 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.)

threading

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).

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.)

zipfile

  • Added support for specifying member name encoding for reading metadata in the zipfile’s directory and file headers. (Contributed by Stephen J. Turnbull and Serhiy Storchaka in bpo-28080.)

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.

  • Replaced JUMP_IF_NOT_EXC_MATCH by CHECK_EXC_MATCH which performs the check but does not jump.

  • Replaced JUMP_ABSOLUTE by the relative JUMP_BACKWARD.

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.)

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

  • 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:

    (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.)

  • 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 removed in Python 3.12 (PEP 594). (Contributed by Hugo van Kemenade in bpo-47022.)

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:

    (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 (శ్రీనివాస్ 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.)

  • Global inline flags (e.g. (?i)) can now only be used at the start of the regular expressions. Using them not at the start of expression was deprecated since Python 3.6. (Contributed by Serhiy Storchaka in bpo-47066.)

  • re module: Fix a few long-standing bugs where, in rare cases, capturing group could get wrong result. So the result may be different than before. (Contributed by Ma Lin in bpo-35859.)

  • The population parameter of random.sample() must be a sequence. Automatic conversion of sets to lists is no longer supported. If the sample size is larger than the population size, a ValueError is raised. (Contributed by Raymond Hettinger in bpo-40465.)

Build Changes

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

  • Building Python now requires support of IEEE 754 floating point numbers. (Contributed by Victor Stinner in bpo-46917.)

  • 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, Tcl/Tk libs, and uuid flags are detected by pkg-config (when available). (Contributed by Christian Heimes and Erlend Egeberg Aasland in bpo-45847, bpo-45747, and bpo-45763.)

    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.

  • 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.)

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

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

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:

    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:

    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.

  • Move the private undocumented _PyEval_EvalFrameDefault() function to the internal C API. The function now uses the _PyInterpreterFrame type which is part of the internal C API. (Contributed by Victor Stinner in bpo-46850.)

  • Move the private _PyFrameEvalFunction type, and private _PyInterpreterState_GetEvalFrameFunc() and _PyInterpreterState_SetEvalFrameFunc() functions to the internal C API. The _PyFrameEvalFunction callback function type now uses the _PyInterpreterFrame type which is part of the internal C API. (Contributed by Victor Stinner in bpo-46850.)

Deprecated

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:

    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.)