3.12.0b2
DateJune 09, 2023
This article explains the new features in Python 3.12, compared to 3.11.
For full details, see the changelog.
Note
Prerelease users should be aware that this document is currently in draftform. It will be updated substantially as Python 3.12 moves towards release,so it’s worth checking back even after reading earlier versions.
Summary – Release highlights¶New grammar features:
PEP 701: Syntactic formalization of f-strings
New typing features:
PEP 688: Making the buffer protocol accessible in Python
PEP 692: Using TypedDict for more precise **kwargs typing
PEP 695: Type Parameter Syntax
PEP 698: Override Decorator for Static Typing
Important deprecations, removals or restrictions:
PEP 623: Remove wstr from Unicode
PEP 632: Remove the distutils package
Improved Error Messages¶Modules from the standard library are now potentially suggested as part ofthe error messages displayed by the interpreter when a NameError israised to the top level. Contributed by Pablo Galindo in gh-98254.
>>> sys.version_infoTraceback (most recent call last): File "", line 1, in NameError: name 'sys' is not defined. Did you forget to import 'sys'?Improve the error suggestion for NameError exceptions for instances.Now if a NameError is raised in a method and the instance has anattribute that’s exactly equal to the name in the exception, the suggestionwill include self. instead of the closest match in the methodscope. Contributed by Pablo Galindo in gh-99139.
>>> class A:...def __init__(self):...self.blech = 1......def foo(self):...somethin = blech>>> A().foo() File "", line 1somethin = blech^^^^^NameError: name 'blech' is not defined. Did you mean: 'self.blech'?Improve the SyntaxError error message when the user types import xfrom y instead of from y import x. Contributed by Pablo Galindo in gh-98931.
>>> import a.y.z from b.y.z File "", line 1import a.y.z from b.y.z^^^^^^^^^^^^^^^^^^^^^^^SyntaxError: Did you mean to use 'from ... import ...' instead?ImportError exceptions raised from failed from import statements now include suggestions for the value of based on theavailable names in . Contributed by Pablo Galindo in gh-91058.
>>> from collections import chainmapTraceback (most recent call last): File "", line 1, in ImportError: cannot import name 'chainmap' from 'collections'. Did you mean: 'ChainMap'?New Features¶PEP 701: Syntactic formalization of f-strings¶PEP 701 lifts some restrictions on the usage of f-strings. Expression componentsinside f-strings can now be any valid Python expression including backslashes,unicode escaped sequences, multi-line expressions, comments and strings reusing thesame quote as the containing f-string. Let’s cover these in detail:
Quote reuse: in Python 3.11, reusing the same quotes as the containing f-stringraises a SyntaxError, forcing the user to either use other availablequotes (like using double quotes or triple quotes if the f-string uses singlequotes). In Python 3.12, you can now do things like this:
>>> songs = ['Take me back to Eden', 'Alkaline', 'Ascensionism']>>> f"This is the playlist: {", ".join(songs)}"'This is the playlist: Take me back to Eden, Alkaline, Ascensionism'Note that before this change there was no explicit limit in how f-strings canbe nested, but the fact that string quotes cannot be reused inside theexpression component of f-strings made it impossible to nest f-stringsarbitrarily. In fact, this is the most nested f-string that could be written:
>>> f"""{f'''{f'{f"{1+1}"}'}'''}"""'2'As now f-strings can contain any valid Python expression inside expressioncomponents, it is now possible to nest f-strings arbitrarily:
>>> f"{f"{f"{f"{f"{f"{1+1}"}"}"}"}"}"'2'Multi-line expressions and comments: In Python 3.11, f-strings expressionsmust be defined in a single line even if outside f-strings expressions couldspan multiple lines (like literal lists being defined over multiple lines),making them harder to read. In Python 3.12 you can now define expressionsspanning multiple lines and include comments on them:
>>> f"This is the playlist: {", ".join([... 'Take me back to Eden', # My, my, those eyes like fire... 'Alkaline', # Not acid nor alkaline... 'Ascensionism'# Take to the broken skies at last... ])}"'This is the playlist: Take me back to Eden, Alkaline, Ascensionism'Backslashes and unicode characters: before Python 3.12 f-string expressionscouldn’t contain any \ character. This also affected unicode escapedsequences (such as \N{snowman}) as these contain the \N part thatpreviously could not be part of expression components of f-strings. Now, youcan define expressions like this:
>>> print(f"This is the playlist: {"\n".join(songs)}")This is the playlist: Take me back to EdenAlkalineAscensionism>>> print(f"This is the playlist: {"\N{BLACK HEART SUIT}".join(songs)}")This is the playlist: Take me back to Eden♥Alkaline♥AscensionismSee PEP 701 for more details.
As a positive side-effect of how this feature has been implemented (by parsing f-stringswith the PEG parser (see PEP 617), now error messages for f-strings are more preciseand include the exact location of the error. For example, in Python 3.11, the followingf-string raises a SyntaxError:
>>> my_string = f"{x z y}" + f"{1 + 1}" File "", line 1(x z y) ^^^SyntaxError: f-string: invalid syntax. Perhaps you forgot a comma?but the error message doesn’t include the exact location of the error within the line andalso has the expression artificially surrounded by parentheses. In Python 3.12, as f-stringsare parsed with the PEG parser, error messages can be more precise and show the entire line:
>>> my_string = f"{x z y}" + f"{1 + 1}" File "", line 1my_string = f"{x z y}" + f"{1 + 1}"^^^SyntaxError: invalid syntax. Perhaps you forgot a comma?(Contributed by Pablo Galindo, Batuhan Taskaya, Lysandros Nikolaou, CristiánMaureira-Fredes and Marta Gómez in gh-102856. PEP written by Pablo Galindo,Batuhan Taskaya, Lysandros Nikolaou and Marta Gómez).
PEP 709: Comprehension inlining¶Dictionary, list, and set comprehensions are now inlined, rather than creating anew single-use function object for each execution of the comprehension. Thisspeeds up execution of a comprehension by up to 2x.
Comprehension iteration variables remain isolated; they don’t overwrite avariable of the same name in the outer scope, nor are they visible after thecomprehension. This isolation is now maintained via stack/locals manipulation,not via separate function scope.
Inlining does result in a few visible behavior changes:
There is no longer a separate frame for the comprehension in tracebacks,and tracing/profiling no longer shows the comprehension as a function call.
Calling locals() inside a comprehension now includes variablesfrom outside the comprehension, and no longer includes the synthetic .0variable for the comprehension “argument”.
Contributed by Carl Meyer and Vladimir Matveev in PEP 709.
PEP 688: Making the buffer protocol accessible in Python¶PEP 688 introduces a way to use the buffer protocolfrom Python code. Classes that implement the __buffer__() methodare now usable as buffer types.
The new collections.abc.Buffer ABC provides a standardway to represent buffer objects, for example in type annotations.The new inspect.BufferFlags enum represents the flags thatcan be used to customize buffer creation.(Contributed by Jelle Zijlstra in gh-102500.)
New Features Related to Type Hints¶This section covers major changes affecting PEP 484 type hints andthe typing module.
PEP 692: Using TypedDict for more precise **kwargs typing¶Typing **kwargs in a function signature as introduced by PEP 484 allowedfor valid annotations only in cases where all of the **kwargs were of thesame type.
This PEP specifies a more precise way of typing **kwargs by relying ontyped dictionaries:
from typing import TypedDict, Unpackclass Movie(TypedDict): name: str year: intdef foo(**kwargs: Unpack[Movie]): ...See PEP 692 for more details.
(Contributed by Franek Magiera in gh-103629.)
PEP 698: Override Decorator for Static Typing¶A new decorator typing.override() has been added to the typingmodule. It indicates to type checkers that the method is intended to overridea method in a superclass. This allows type checkers to catch mistakes wherea method that is intended to override something in a base classdoes not in fact do so.
Example:
from typing import overrideclass Base: def get_color(self) -> str:return "blue"class GoodChild(Base): @override # ok: overrides Base.get_color def get_color(self) -> str:return "yellow"class BadChild(Base): @override # type checker error: does not override Base.get_color def get_colour(self) -> str:return "red"(Contributed by Steven Troxler in gh-101561.)
PEP 695: Type Parameter Syntax¶Generic classes and functions under PEP 484 were declared using a verbose syntaxthat left the scope of type parameters unclear and required explicit declarations ofvariance.
PEP 695 introduces a new, more compact and explicit way to creategeneric classes and functions:
def max[T](args: Iterable[T]) -> T:...class list[T]:def __getitem__(self, index: int, /) -> T:...def append(self, element: T) -> None:...In addition, the PEP introduces a new way to declare type aliasesusing the type statement, which creates an instance ofTypeAliasType:
type Point = tuple[float, float]Type aliases can also be generic:
type Point[T] = tuple[T, T]The new syntax allows declaring TypeVarTupleand ParamSpec parameters, as well as TypeVarparameters with bounds or constraints:
type IntFunc[**P] = Callable[P, int] # ParamSpectype LabeledTuple[*Ts] = tuple[str, *Ts] # TypeVarTupletype HashableSequence[T: Hashable] = Sequence[T] # TypeVar with boundtype IntOrStrSequence[T: (int, str)] = Sequence[T] # TypeVar with constraintsThe value of type aliases and the bound and constraints of type variablescreated through this syntax are evaluated only on demand (seeLazy evaluation). This means type aliases are able to refer to othertypes defined later in the file.
Type parameters declared through a type parameter list are visible within thescope of the declaration and any nested scopes, but not in the outer scope. Forexample, they can be used in the type annotations for the methods of a genericclass or in the class body. However, they cannot be used in the module scope afterthe class is defined. See Type parameter lists for a detailed description of theruntime semantics of type parameters.
In order to support these scoping semantics, a new kind of scope is introduced,the annotation scope. Annotation scopes behave for themost part like function scopes, but interact differently with enclosing class scopes.In Python 3.13, annotations will also be evaluated inannotation scopes.
See PEP 695 for more details.
(PEP written by Eric Traut. Implementation by Jelle Zijlstra, Eric Traut,and others in gh-103764.)
Other Language Changes¶Add Python support for the Linux perf profiler through the newenvironment variable PYTHONPERFSUPPORT,the new command-line option -X perf,as well as the new sys.activate_stack_trampoline(),sys.deactivate_stack_trampoline(),and sys.is_stack_trampoline_active() APIs.(Design by Pablo Galindo. Contributed by Pablo Galindo and Christian Heimeswith contributions from Gregory P. Smith [Google] and Mark Shannonin gh-96123.)
The extraction methods in tarfile, and shutil.unpack_archive(),have a new a filter argument that allows limiting tar features than may besurprising or dangerous, such as creating files outside the destinationdirectory.See Extraction filters for details.In Python 3.14, the default will switch to 'data'.(Contributed by Petr Viktorin in PEP 706.)
types.MappingProxyType instances are now hashable if the underlyingmapping is hashable.(Contributed by Serhiy Storchaka in gh-87995.)
memoryview now supports the half-float type (the “e” format code).(Contributed by Dong-hee Na and Antoine Pitrou in gh-90751.)
The parser now raises SyntaxError when parsing source code containingnull bytes. (Contributed by Pablo Galindo in gh-96670.)
ast.parse() now raises SyntaxError instead of ValueErrorwhen parsing source code containing null bytes. (Contributed by Pablo Galindoin gh-96670.)
The Garbage Collector now runs only on the eval breaker mechanism of thePython bytecode evaluation loop instead of object allocations. The GC canalso run when PyErr_CheckSignals() is called so C extensions thatneed to run for a long time without executing any Python code also have achance to execute the GC periodically. (Contributed by Pablo Galindo ingh-97922.)
A backslash-character pair that is not a valid escape sequence now generatesa SyntaxWarning, instead of DeprecationWarning.For example, re.compile("\d+\.\d+") now emits a SyntaxWarning("\d" is an invalid escape sequence), use raw strings for regularexpression: re.compile(r"\d+\.\d+").In a future Python version, SyntaxError will eventually be raised,instead of SyntaxWarning.(Contributed by Victor Stinner in gh-98401.)
Octal escapes with value larger than 0o377 (ex: "\477"), deprecatedin Python 3.11, now produce a SyntaxWarning, instead ofDeprecationWarning.In a future Python version they will be eventually a SyntaxError.(Contributed by Victor Stinner in gh-98401.)
All builtin and extension callables expecting boolean parameters now acceptarguments of any type instead of just bool and int.(Contributed by Serhiy Storchaka in gh-60203.)
Variables used in the target part of comprehensions that are not stored tocan now be used in assignment expressions (:=).For example, in [(b := 1) for a, b.prop in some_iter], the assignment tob is now allowed. Note that assigning to variables stored to in the targetpart of comprehensions (like a) is still disallowed, as per PEP 572.(Contributed by Nikita Sobolev in gh-100581.)
slice objects are now hashable, allowing them to be used as dict keys andset items. (Contributed by Will Bradshaw, Furkan Onder, and Raymond Hettinger in gh-101264.)
sum() now uses Neumaier summation to improve accuracy when summingfloats or mixed ints and floats.(Contributed by Raymond Hettinger in gh-100425.)
Exceptions raised in a typeobject’s __set_name__ method are no longerwrapped by a RuntimeError. Context information is added to theexception as a PEP 678 note. (Contributed by Irit Katriel in gh-77757.)
When a try-except* construct handles the entire ExceptionGroupand raises one other exception, that exception is no longer wrapped in anExceptionGroup. Also changed in version 3.11.4. (Contributed by IritKatriel in gh-103590.)
New Modules¶None yet.
Improved Modules¶array¶The array.array class now supports subscripting, making it ageneric type. (Contributed by Jelle Zijlstra in gh-98658.)
asyncio¶The performance of writing to sockets in asyncio has beensignificantly improved. asyncio now avoids unnecessary copying whenwriting to sockets and uses sendmsg() if the platformsupports it. (Contributed by Kumar Aditya in gh-91166.)
Added asyncio.eager_task_factory() and asyncio.create_eager_task_factory()functions to allow opting an event loop in to eager task execution,making some use-cases 2x to 5x faster.(Contributed by Jacob Bower & Itamar O in gh-102853, gh-104140, and gh-104138)
On Linux, asyncio uses PidfdChildWatcher by defaultif os.pidfd_open() is available and functional instead ofThreadedChildWatcher.(Contributed by Kumar Aditya in gh-98024.)
The child watcher classes MultiLoopChildWatcher,FastChildWatcher, AbstractChildWatcherand SafeChildWatcher are deprecated andwill be removed in Python 3.14. It is recommended to not manuallyconfigure a child watcher as the event loop now uses the best availablechild watcher for each platform (PidfdChildWatcherif supported and ThreadedChildWatcher otherwise).(Contributed by Kumar Aditya in gh-94597.)
asyncio.set_child_watcher(), asyncio.get_child_watcher(),asyncio.AbstractEventLoopPolicy.set_child_watcher() andasyncio.AbstractEventLoopPolicy.get_child_watcher() are deprecatedand will be removed in Python 3.14.(Contributed by Kumar Aditya in gh-94597.)
Add loop_factory parameter to asyncio.run() to allow specifyinga custom event loop factory.(Contributed by Kumar Aditya in gh-99388.)
Add C implementation of asyncio.current_task() for 4x-6x speedup.(Contributed by Itamar Ostricher and Pranav Thulasiram Bhat in gh-100344.)
asyncio.iscoroutine() now returns False for generators asasyncio does not support legacy generator-based coroutines.(Contributed by Kumar Aditya in gh-102748.)
asyncio.wait() and asyncio.as_completed() now accepts generatorsyielding tasks.(Contributed by Kumar Aditya in gh-78530.)
calendar¶Add enums Month and Day.(Contributed by Prince Roshan in gh-103636.)
csv¶Add QUOTE_NOTNULL and QUOTE_STRINGS flags toprovide finer grained control of None and empty strings bywriter objects.
dis¶Pseudo instruction opcodes (which are used by the compiler butdo not appear in executable bytecode) are now exposed in thedis module.HAVE_ARGUMENT is still relevant to real opcodes,but it is not useful for pseudo instructions. Use the newhasarg collection instead.(Contributed by Irit Katriel in gh-94216.)
fractions¶Objects of type fractions.Fraction now support float-styleformatting. (Contributed by Mark Dickinson in gh-100161.)
inspect¶Add inspect.markcoroutinefunction() to mark sync functions that returna coroutine for use with inspect.iscoroutinefunction().(Contributed Carlton Gibson in gh-99247.)
Add inspect.getasyncgenstate() and inspect.getasyncgenlocals()for determining the current state of asynchronous generators.(Contributed by Thomas Krennwallner in bpo-35759.)
The performance of inspect.getattr_static() has been considerablyimproved. Most calls to the function should be at least 2x faster than theywere in Python 3.11, and some may be 6x faster or more. (Contributed by AlexWaygood in gh-103193.)
itertools¶Added itertools.batched() for collecting into even-sizedtuples where the last batch may be shorter than the rest.(Contributed by Raymond Hettinger in gh-98363.)
json¶Added json.AttrDict for use with object_hook in json.load()or json.loads(). This is a subclass of dict that also supportsattribute style dotted access.(Contributed by Raymond Hettinger in gh-96145.)
math¶Added math.sumprod() for computing a sum of products.(Contributed by Raymond Hettinger in gh-100485.)
Extended math.nextafter() to include a steps argumentfor moving up or down multiple steps at a time.(By Matthias Goergens, Mark Dickinson, and Raymond Hettinger in gh-94906.)
os¶Add os.PIDFD_NONBLOCK to open a file descriptorfor a process with os.pidfd_open() in non-blocking mode.(Contributed by Kumar Aditya in gh-93312.)
os.DirEntry now includes an os.DirEntry.is_junction()method to check if the entry is a junction.(Contributed by Charles Machalow in gh-99547.)
Add os.listdrives(), os.listvolumes() and os.listmounts()functions on Windows for enumerating drives, volumes and mount points.(Contributed by Steve Dower in gh-102519.)
os.stat() and os.lstat() are now more accurate on Windows.The st_birthtime field will now be filled with the creation timeof the file, and st_ctime is deprecated but still contains thecreation time (but in the future will return the last metadata change,for consistency with other platforms). st_dev may be up to 64 bitsand st_ino up to 128 bits depending on your file system, andst_rdev is always set to zero rather than incorrect values.Both functions may be significantly faster on newer releases ofWindows. (Contributed by Steve Dower in gh-99726.)
os.path¶Add os.path.isjunction() to check if a given path is a junction.(Contributed by Charles Machalow in gh-99547.)
Add os.path.splitroot() to split a path into a triad(drive, root, tail). (Contributed by Barney Gale in gh-101000.)
pathlib¶Add support for subclassing pathlib.PurePath andPath, plus their Posix- and Windows-specific variants.Subclasses may override the with_segments() methodto pass information between path instances.
Add walk() for walking the directory trees and generatingall file or directory names within them, similar to os.walk().(Contributed by Stanislav Zmiev in gh-90385.)
Add walk_up optional parameter to pathlib.PurePath.relative_to()to allow the insertion of .. entries in the result; this behavior ismore consistent with os.path.relpath().(Contributed by Domenico Ragusa in bpo-40358.)
Add pathlib.Path.is_junction() as a proxy to os.path.isjunction().(Contributed by Charles Machalow in gh-99547.)
Add case_sensitive optional parameter to pathlib.Path.glob(),pathlib.Path.rglob() and pathlib.PurePath.match() for matchingthe path’s case sensitivity, allowing for more precise control over the matching process.
pdb¶Add convenience variables to hold values temporarily for debug sessionand provide quick access to values like the current frame or the returnvalue.(Contributed by Tian Gao in gh-103693.)
random¶Added random.binomialvariate().(Contributed by Raymond Hettinger in gh-81620.)
Added a default of lamb=1.0 to random.expovariate().(Contributed by Raymond Hettinger in gh-100234.)
shutil¶shutil.make_archive() now passes the root_dir argument to customarchivers which support it.In this case it no longer temporarily changes the current working directoryof the process to root_dir to perform archiving.(Contributed by Serhiy Storchaka in gh-74696.)
shutil.rmtree() now accepts a new argument onexc which is anerror handler like onerror but which expects an exception instancerather than a (typ, val, tb) triplet. onerror is deprecated andwill be removed in Python 3.14.(Contributed by Irit Katriel in gh-102828.)
shutil.which() now consults the PATHEXT environment variable tofind matches within PATH on Windows even when the given cmd includesa directory component.(Contributed by Charles Machalow in gh-103179.)
shutil.which() will call NeedCurrentDirectoryForExePathW whenquerying for executables on Windows to determine if the current workingdirectory should be prepended to the search path.(Contributed by Charles Machalow in gh-103179.)
shutil.which() will return a path matching the cmd with a componentfrom PATHEXT prior to a direct match elsewhere in the search path onWindows.(Contributed by Charles Machalow in gh-103179.)
sqlite3¶Add a command-line interface.(Contributed by Erlend E. Aasland in gh-77617.)
Add the autocommit attributeto Connectionand the autocommit parameter to connect()to control PEP 249-complianttransaction handling.(Contributed by Erlend E. Aasland in gh-83638.)
Add entrypoint keyword-only parameter toload_extension(),for overriding the SQLite extension entry point.(Contributed by Erlend E. Aasland in gh-103015.)
Add getconfig() andsetconfig() to Connectionto make configuration changes to a database connection.(Contributed by Erlend E. Aasland in gh-103489.)
statistics¶Extended statistics.correlation() to include as a ranked methodfor computing the Spearman correlation of ranked data.(Contributed by Raymond Hettinger in gh-95861.)
sys¶Add sys.activate_stack_trampoline() andsys.deactivate_stack_trampoline() for activating and deactivatingstack profiler trampolines,and sys.is_stack_trampoline_active() for querying if stack profilertrampolines are active.(Contributed by Pablo Galindo and Christian Heimeswith contributions from Gregory P. Smith [Google] and Mark Shannonin gh-96123.)
Add sys.last_exc which holds the last unhandled exception thatwas raised (for post-mortem debugging use cases). Deprecate thethree fields that have the same information in its legacy form:sys.last_type, sys.last_value and sys.last_traceback.(Contributed by Irit Katriel in gh-102778.)
sys._current_exceptions() now returns a mapping from thread-id to anexception instance, rather than to a (typ, exc, tb) tuple.(Contributed by Irit Katriel in gh-103176.)
tempfile¶The tempfile.NamedTemporaryFile function has a new optional parameterdelete_on_close (Contributed by Evgeny Zorin in gh-58451.)
tempfile.mkdtemp() now always returns an absolute path, even if theargument provided to the dir parameter is a relative path.
threading¶Add threading.settrace_all_threads() andthreading.setprofile_all_threads() that allow to set tracing andprofiling functions in all running threads in addition to the calling one.(Contributed by Pablo Galindo in gh-93503.)
tkinter¶tkinter.Canvas.coords() now flattens its arguments.It now accepts not only coordinates as separate arguments(x1, y1, x2, y2, ...) and a sequence of coordinates([x1, y1, x2, y2, ...]), but also coordinates grouped in pairs((x1, y1), (x2, y2), ... and [(x1, y1), (x2, y2), ...]),like create_*() methods.(Contributed by Serhiy Storchaka in gh-94473.)
tokenize¶The tokenize module includes the changes introduced in PEP 701. (Contributed by Marta Gómez Macías and Pablo Galindo in gh-102856.)See Porting to Python 3.12 for more information on thechanges to the tokenize module.
types¶Add types.get_original_bases() to allow for further introspection ofUser-defined generic types when subclassed. (Contributed byJames Hilton-Balfe and Alex Waygood in gh-101827.)
typing¶isinstance() checks againstruntime-checkable protocols now useinspect.getattr_static() rather than hasattr() to lookup whetherattributes exist. This means that descriptors and __getattr__()methods are no longer unexpectedly evaluated during isinstance() checksagainst runtime-checkable protocols. However, it may also mean that someobjects which used to be considered instances of a runtime-checkable protocolmay no longer be considered instances of that protocol on Python 3.12+, andvice versa. Most users are unlikely to be affected by this change.(Contributed by Alex Waygood in gh-102433.)
The members of a runtime-checkable protocol are now considered “frozen” atruntime as soon as the class has been created. Monkey-patching attributesonto a runtime-checkable protocol will still work, but will have no impact onisinstance() checks comparing objects to the protocol. For example:
>>> from typing import Protocol, runtime_checkable>>> @runtime_checkable... class HasX(Protocol):... x = 1...>>> class Foo: ......>>> f = Foo()>>> isinstance(f, HasX)False>>> f.x = 1>>> isinstance(f, HasX)True>>> HasX.y = 2>>> isinstance(f, HasX) # unchanged, even though HasX now also has a "y" attributeTrueThis change was made in order to speed up isinstance() checks againstruntime-checkable protocols.
The performance profile of isinstance() checks againstruntime-checkable protocols has changedsignificantly. Most isinstance() checks against protocols with only a fewmembers should be at least 2x faster than in 3.11, and some may be 20xfaster or more. However, isinstance() checks against protocols with fourteenor more members may be slower than in Python 3.11. (Contributed by AlexWaygood in gh-74690 and gh-103193.)
All typing.TypedDict and typing.NamedTuple classes now have the__orig_bases__ attribute. (Contributed by Adrian Garcia Badaracco ingh-103699.)
Add frozen_default parameter to typing.dataclass_transform().(Contributed by Erik De Bonte in gh-99957.)
unicodedata¶The Unicode database has been updated to version 15.0.0. (Contributed byBenjamin Peterson in gh-96734).
unittest¶Added --durations command line option, showing the N slowest test cases:
python3 -m unittest --durations=3 lib.tests.test_threading.....Slowest test durations----------------------------------------------------------------------1.210s test_timeout (Lib.test.test_threading.BarrierTests)1.003s test_default_timeout (Lib.test.test_threading.BarrierTests)0.518s test_timeout (Lib.test.test_threading.EventTests)(0.000 durations hidden. Use -v to show these durations.)----------------------------------------------------------------------Ran 158 tests in 9.869sOK (skipped=3)(Contributed by Giampaolo Rodola in bpo-4080)
uuid¶Add a command-line interface.(Contributed by Adam Chhina in gh-88597.)
Optimizations¶Removed wstr and wstr_length members from Unicode objects.It reduces object size by 8 or 16 bytes on 64bit platform. (PEP 623)(Contributed by Inada Naoki in gh-92536.)
Added experimental support for using the BOLT binary optimizer in the buildprocess, which improves performance by 1-5%.(Contributed by Kevin Modzelewski in gh-90536 and tuned by Dong-hee Na in gh-101525)
Speed up the regular expression substitution (functions re.sub() andre.subn() and corresponding re.Pattern methods) forreplacement strings containing group references by 2–3 times.(Contributed by Serhiy Storchaka in gh-91524.)
Speed up asyncio.Task creation by deferring expensive string formatting.(Contributed by Itamar O in gh-103793.)
The tokenize.tokenize() and tokenize.generate_tokens() functions areup to 64% faster as a side effect of the changes required to cover PEP 701 inthe tokenize module. (Contributed by Marta Gómez Macías and Pablo Galindoin gh-102856.)
Speed up super() method calls and attribute loads via thenew LOAD_SUPER_ATTR instruction. (Contributed by Carl Meyer andVladimir Matveev in gh-103497.)
CPython bytecode changes¶Remove the LOAD_METHOD instruction. It has been merged intoLOAD_ATTR. LOAD_ATTR will now behave like the oldLOAD_METHOD instruction if the low bit of its oparg is set.(Contributed by Ken Jin in gh-93429.)
Remove the JUMP_IF_FALSE_OR_POP and JUMP_IF_TRUE_OR_POPinstructions. (Contributed by Irit Katriel in gh-102859.)
Add the LOAD_FAST_AND_CLEAR instruction as part of theimplementation of PEP 709. (Contributed by Carl Meyer in gh-101441.)
Add the LOAD_FROM_DICT_OR_DEREF, LOAD_FROM_DICT_OR_GLOBALS,and LOAD_LOCALS opcodes as part of the implementation of PEP 695.Remove the LOAD_CLASSDEREF opcode, which can be replaced withLOAD_LOCALS plus LOAD_FROM_DICT_OR_DEREF. (Contributedby Jelle Zijlstra in gh-103764.)
Add the LOAD_SUPER_ATTR instruction. (Contributed by Carl Meyer andVladimir Matveev in gh-103497.)
Demos and Tools¶Remove the Tools/demo/ directory which contained old demo scripts. A copycan be found in the old-demos project.(Contributed by Victor Stinner in gh-97681.)
Remove outdated example scripts of the Tools/scripts/ directory.A copy can be found in the old-demos project.(Contributed by Victor Stinner in gh-97669.)
Deprecated¶typing.Hashable and typing.Sized aliases for collections.abc.Hashableand collections.abc.Sized. (gh-94309.)
The sqlite3 default adapters and converters are now deprecated.Instead, use the Adapter and converter recipesand tailor them to your needs.(Contributed by Erlend E. Aasland in gh-90016.)
In execute(), DeprecationWarning is now emittedwhen named placeholders are used together withparameters supplied as a sequence instead of as a dict.Starting from Python 3.14, using named placeholders with parameters suppliedas a sequence will raise a ProgrammingError.(Contributed by Erlend E. Aasland in gh-101698.)
The 3-arg signatures (type, value, traceback) of throw(),throw() and athrow() are deprecated andmay be removed in a future version of Python. Use the single-arg versionsof these functions instead. (Contributed by Ofey Chan in gh-89874.)
DeprecationWarning is now raised when __package__ on amodule differs from __spec__.parent (previously it wasImportWarning).(Contributed by Brett Cannon in gh-65961.)
The get_event_loop() method of thedefault event loop policy now emits a DeprecationWarning if thereis no current event loop set and it decides to create one.(Contributed by Serhiy Storchaka and Guido van Rossum in gh-100160.)
The xml.etree.ElementTree module now emits DeprecationWarningwhen testing the truth value of an xml.etree.ElementTree.Element.Before, the Python implementation emitted FutureWarning, and the Cimplementation emitted nothing.
In accordance with PEP 699, the ma_version_tag field in PyDictObjectis deprecated for extension modules. Accessing this field will generate a compilerwarning at compile time. This field will be removed in Python 3.14.(Contributed by Ramvikrams and Kumar Aditya in gh-101193. PEP by Ken Jin.)
The st_ctime fields return by os.stat() and os.lstat() onWindows are deprecated. In a future release, they will contain the lastmetadata change time, consistent with other platforms. For now, they stillcontain the creation time, which is also available in the new st_birthtimefield. (Contributed by Steve Dower in gh-99726.)
The sys.last_type, sys.last_value and sys.last_tracebackfields are deprecated. Use sys.last_exc instead.(Contributed by Irit Katriel in gh-102778.)
The onerror argument of shutil.rmtree() is deprecated as will be removedin Python 3.14. Use onexc instead. (Contributed by Irit Katriel in gh-102828.)
Extracting tar archives without specifying filter is deprecated untilPython 3.14, when 'data' filter will become the default.See Extraction filters for details.
calendar.January and calendar.February constants are deprecated andreplaced by calendar.Month.JANUARY and calendar.Month.FEBRUARY.(Contributed by Prince Roshan in gh-103636.)
The bitwise inversion operator (~) on bool is deprecated. It will throw anerror in Python 3.14. Use not for logical negation of bools instead.In the rare case that you really need the bitwise inversion of the underlyingint, convert to int explicitly with ~int(x). (Contributed by Tim Hoffmannin gh-103487.)
datetime.datetime’sutcnow() andutcfromtimestamp() are deprecated and will beremoved in a future version. Instead, use timezone-aware objects to representdatetimes in UTC: respectively, callnow() andfromtimestamp() with the tz parameter set todatetime.UTC.(Contributed by Paul Ganssle in gh-103857.)
Pending Removal in Python 3.13¶The following modules and APIs have been deprecated in earlier Python releases,and will be removed in Python 3.13.
Modules (see PEP 594):
aifc
audioop
cgi
cgitb
chunk
crypt
imghdr
mailcap
msilib
nis
nntplib
ossaudiodev
pipes
sndhdr
spwd
sunau
telnetlib
uu
xdrlib
APIs:
configparser.LegacyInterpolation (gh-90765)
locale.getdefaultlocale() (gh-90817)
turtle.RawTurtle.settiltangle() (gh-50096)
unittest.findTestCases() (gh-50096)
unittest.getTestCaseNames() (gh-50096)
unittest.makeSuite() (gh-50096)
unittest.TestProgram.usageExit() (gh-67048)
webbrowser.MacOSX (gh-86421)
classmethod descriptor chaining (gh-89519)
Pending Removal in Python 3.14¶Deprecated the following importlib.abc classes, scheduled for removal inPython 3.14:
importlib.abc.ResourceReader
importlib.abc.Traversable
importlib.abc.TraversableResources
Use importlib.resources.abc classes instead:
importlib.resources.abc.Traversable
importlib.resources.abc.TraversableResources
(Contributed by Jason R. Coombs and Hugo van Kemenade in gh-93963.)
Deprecated collections.abc.ByteString.Prefer Sequence or collections.abc.Buffer.For use in typing, prefer a union, like bytes | bytearray, or collections.abc.Buffer.(Contributed by Shantanu Jain in gh-91896.)
typing.ByteString, deprecated since Python 3.9, now causes aDeprecationWarning to be emitted when it is used.
Creating immutable types (Py_TPFLAGS_IMMUTABLETYPE) with mutablebases using the C API.
Deprecated the isdst parameter in email.utils.localtime().(Contributed by Alan Williams in gh-72346.)
__package__ and __cached__ will cease to be set or takeninto consideration by the import system (gh-97879).
Testing the truth value of an xml.etree.ElementTree.Elementis deprecated and will raise an exception in Python 3.14.
The default multiprocessing start method will change to a safer one onLinux, BSDs, and other non-macOS POSIX platforms where 'fork' is currentlythe default (gh-84559). Adding a runtime warning about this was deemed toodisruptive as the majority of code is not expected to care. Use theget_context() orset_start_method() APIs to explicitly specify whenyour code requires 'fork'. See Contexts and start methods.
pty has two undocumented master_open() and slave_open()functions that have been deprecated since Python 2 but only gained aproper DeprecationWarning in 3.12. Remove them in 3.14.
itertools had undocumented, inefficient, historically buggy,and inconsistent support for copy, deepcopy, and pickle operations.This will be removed in 3.14 for a significant reduction in codevolume and maintenance burden.(Contributed by Raymond Hettinger in gh-101588.)
Accessing co_lnotab was deprecated in PEP 626 since 3.10and was planned to be removed in 3.12but it only got a proper DeprecationWarning in 3.12.May be removed in 3.14.(Contributed by Nikita Sobolev in gh-101866.)
The onerror argument of shutil.rmtree() is deprecated in 3.12,and will be removed in 3.14.
The type, choices, and metavar parametersof argparse.BooleanOptionalAction are deprecatedand will be removed in 3.14.(Contributed by Nikita Sobolev in gh-92248.)
pkgutil.find_loader() and pkgutil.get_loader()now raise DeprecationWarning;use importlib.util.find_spec() instead.(Contributed by Nikita Sobolev in gh-97850.)
The following ast features have been deprecated in documentation sincePython 3.8, now cause a DeprecationWarning to be emitted at runtimewhen they are accessed or used, and will be removed in Python 3.14:
ast.Num
ast.Str
ast.Bytes
ast.NameConstant
ast.Ellipsis
Use ast.Constant instead.(Contributed by Serhiy Storchaka in gh-90953.)
Pending Removal in Future Versions¶The following APIs were deprecated in earlier Python versions and will be removed,although there is currently no date scheduled for their removal.
typing.Text (gh-92332)
Currently Python accepts numeric literals immediately followed by keywords,for example 0in x, 1or x, 0if 1else 2. It allows confusingand ambiguous expressions like [0x1for x in y] (which can beinterpreted as [0x1 for x in y] or [0x1f or x in y]).A syntax warning is raised if the numeric literal isimmediately followed by one of keywords and, else,for, if, in, is and or.In a future release it will be changed to a syntax error. (gh-87999)
Removed¶Remove the distutils package. It was deprecated in Python 3.10 byPEP 632 “Deprecate distutils module”. For projects still usingdistutils and cannot be updated to something else, the setuptoolsproject can be installed: it still provides distutils.(Contributed by Victor Stinner in gh-92584.)
Remove the bundled setuptools wheel from ensurepip,and stop installing setuptools in environments created by venv.
pip (>= 22.1) does not require setuptools to be installed in theenvironment. setuptools-based (and distutils-based) packagescan still be used with pip install, since pip will providesetuptools in the build environment it uses for building apackage.
easy_install, pkg_resources, setuptools and distutilsare no longer provided by default in environments created withvenv or bootstrapped with ensurepip, since they are part ofthe setuptools package. For projects relying on these at runtime,the setuptools project should be declared as a dependency andinstalled separately (typically, using pip).
(Contributed by Pradyun Gedam in gh-95299.)
Removed many old deprecated unittest features:
A number of TestCase method aliases:
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
You can use https://github.com/isidentical/teyit to automatically moderniseyour unit tests.
Undocumented and broken TestCase methodassertDictContainsSubset (deprecated in Python 3.2).
Undocumented TestLoader.loadTestsFromModule parameter use_load_tests(deprecated and ignored since Python 3.2).
An alias of the TextTestResult class:_TextTestResult (deprecated in Python 3.2).
(Contributed by Serhiy Storchaka in bpo-45162.)
Several names deprecated in the configparser way back in 3.2 havebeen removed per gh-89336:
configparser.ParsingError no longer has a filename attributeor argument. Use the source attribute and argument instead.
configparser no longer has a SafeConfigParser class. Use theshorter ConfigParser name instead.
configparser.ConfigParser no longer has a readfp method.Use read_file() instead.
The following undocumented sqlite3 features, deprecated in Python3.10, are now removed:
sqlite3.enable_shared_cache()
sqlite3.OptimizedUnicode
If a shared cache must be used, open the database in URI mode using thecache=shared query parameter.
The sqlite3.OptimizedUnicode text factory has been an alias forstr since Python 3.3. Code that previously set the text factory toOptimizedUnicode can either use str explicitly, or rely on thedefault value which is also str.
(Contributed by Erlend E. Aasland in gh-92548.)
smtpd has been removed according to the schedule in PEP 594,having been deprecated in Python 3.4.7 and 3.5.4.Use aiosmtpd PyPI module or any otherasyncio-based server instead.(Contributed by Oleg Iarygin in gh-93243.)
asynchat and asyncore have been removedaccording to the schedule in PEP 594,having been deprecated in Python 3.6.Use asyncio instead.(Contributed by Nikita Sobolev in gh-96580.)
Remove io.OpenWrapper and _pyio.OpenWrapper, deprecated in Python3.10: just use open() instead. The open() (io.open())function is a built-in function. Since Python 3.10, _pyio.open() isalso a static method.(Contributed by Victor Stinner in gh-94169.)
Remove the ssl.RAND_pseudo_bytes() function, deprecated in Python 3.6:use os.urandom() or ssl.RAND_bytes() instead.(Contributed by Victor Stinner in gh-94199.)
gzip: Remove the filename attribute of gzip.GzipFile,deprecated since Python 2.6, use the name attributeinstead. In write mode, the filename attribute added '.gz' fileextension if it was not present.(Contributed by Victor Stinner in gh-94196.)
Remove the ssl.match_hostname() function.It was deprecated in Python 3.7. OpenSSL performshostname matching since Python 3.7, Python no longer uses thessl.match_hostname() function.(Contributed by Victor Stinner in gh-94199.)
Remove the locale.format() function, deprecated in Python 3.7:use locale.format_string() instead.(Contributed by Victor Stinner in gh-94226.)
hashlib: Remove the pure Python implementation ofhashlib.pbkdf2_hmac(), deprecated in Python 3.10. Python 3.10 andnewer requires OpenSSL 1.1.1 (PEP 644): this OpenSSL version providesa C implementation of pbkdf2_hmac() which is faster.(Contributed by Victor Stinner in gh-94199.)
xml.etree.ElementTree: Remove the ElementTree.Element.copy() method of thepure Python implementation, deprecated in Python 3.10, use thecopy.copy() function instead. The C implementation of xml.etree.ElementTreehas no copy() method, only a __copy__() method.(Contributed by Victor Stinner in gh-94383.)
zipimport: Remove find_loader() and find_module() methods,deprecated in Python 3.10: use the find_spec() method instead. SeePEP 451 for the rationale.(Contributed by Victor Stinner in gh-94379.)
Remove the ssl.wrap_socket() function, deprecated in Python 3.7:instead, create a ssl.SSLContext object and call itsssl.SSLContext.wrap_socket method. Any package that still usesssl.wrap_socket() is broken and insecure. The function neither sends aSNI TLS extension nor validates server hostname. Code is subject to CWE-295: Improper CertificateValidation.(Contributed by Victor Stinner in gh-94199.)
Many previously deprecated cleanups in importlib have now beencompleted:
References to, and support for module_repr() has been removed.(Contributed by Barry Warsaw in gh-97850.)
importlib.util.set_package has been removed. (Contributed by BrettCannon in gh-65961.)
Support for find_loader() and find_module() APIs have beenremoved. (Contributed by Barry Warsaw in gh-98040.)
importlib.abc.Finder, pkgutil.ImpImporter, and pkgutil.ImpLoaderhave been removed. (Contributed by Barry Warsaw in gh-98040.)
The imp module has been removed. (Contributed by Barry Warsaw ingh-98040.)
Removed the suspicious rule from the documentation Makefile, andremoved Doc/tools/rstlint.py, both in favor of sphinx-lint.(Contributed by Julien Palard in gh-98179.)
Remove the keyfile and certfile parameters from theftplib, imaplib, poplib and smtplib modules,and the key_file, cert_file and check_hostname parameters from thehttp.client module,all deprecated since Python 3.6. Use the context parameter(ssl_context in imaplib) instead.(Contributed by Victor Stinner in gh-94172.)
ftplib: Remove the FTP_TLS.ssl_version class attribute: use thecontext parameter instead.(Contributed by Victor Stinner in gh-94172.)
Remove support for obsolete browsers from webbrowser.Removed browsers include: Grail, Mosaic, Netscape, Galeon, Skipstone,Iceape, Firebird, and Firefox versions 35 and below (gh-102871).
Porting to Python 3.12¶This section lists previously described changes and other bugfixesthat may require changes to your code.
Changes in the Python API¶More strict rules are now applied for numerical group references andgroup names in regular expressions.Only sequence of ASCII digits is now accepted as a numerical reference.The group name in bytes patterns and replacement strings can now onlycontain ASCII letters and digits and underscore.(Contributed by Serhiy Storchaka in gh-91760.)
Removed randrange() functionality deprecated since Python 3.10. Formerly,randrange(10.0) losslessly converted to randrange(10). Now, it raises aTypeError. Also, the exception raised for non-integral values such asrandrange(10.5) or randrange('10') has been changed from ValueError toTypeError. This also prevents bugs where randrange(1e25) would silentlyselect from a larger range than randrange(10**25).(Originally suggested by Serhiy Storchaka gh-86388.)
argparse.ArgumentParser changed encoding and error handlerfor reading arguments from file (e.g. fromfile_prefix_chars option)from default text encoding (e.g. locale.getpreferredencoding(False))to filesystem encoding and error handler.Argument files should be encoded in UTF-8 instead of ANSI Codepage on Windows.
Removed the asyncore-based smtpd module deprecated in Python 3.4.7and 3.5.4. A recommended replacement is theasyncio-based aiosmtpd PyPI module.
shlex.split(): Passing None for s argument now raises anexception, rather than reading sys.stdin. The feature was deprecatedin Python 3.9.(Contributed by Victor Stinner in gh-94352.)
The os module no longer accepts bytes-like paths, likebytearray and memoryview types: only the exactbytes type is accepted for bytes strings.(Contributed by Victor Stinner in gh-98393.)
syslog.openlog() and syslog.closelog() now fail if used in subinterpreters.syslog.syslog() may still be used in subinterpreters,but now only if syslog.openlog() has already been called in the main interpreter.These new restrictions do not apply to the main interpreter,so only a very small set of users might be affected.This change helps with interpreter isolation. Furthermore, syslog is a wrapperaround process-global resources, which are best managed from the main interpreter.(Contributed by Dong-hee Na in gh-99127.)
The undocumented locking behavior of cached_property()is removed, because it locked across all instances of the class, leading to highlock contention. This means that a cached property getter function could now runmore than once for a single instance, if two threads race. For most simplecached properties (e.g. those that are idempotent and simply calculate a valuebased on other attributes of the instance) this will be fine. Ifsynchronization is needed, implement locking within the cached property getterfunction or around multi-threaded access points.
sys._current_exceptions() now returns a mapping from thread-id to anexception instance, rather than to a (typ, exc, tb) tuple.(Contributed by Irit Katriel in gh-103176.)
When extracting tar files using tarfile orshutil.unpack_archive(), pass the filter argument to limit featuresthat may be surprising or dangerous.See Extraction filters for details.
The output of the tokenize.tokenize() and tokenize.generate_tokens()functions is now changed due to the changes introduced in PEP 701. Thismeans that STRING tokens are not emitted any more for f-strings and thetokens described in PEP 701 are now produced instead: FSTRING_START,FSRING_MIDDLE and FSTRING_END are now emitted for f-string “string”parts in addition to the appropriate tokens for the tokenization in theexpression components. For example for the f-string f"start {1+1} end"the old version of the tokenizer emitted:
1,0-1,18:STRING 'f"start {1+1} end"'while the new version emits:
1,0-1,2:FSTRING_START 'f"'1,2-1,8:FSTRING_MIDDLE 'start '1,8-1,9:OP '{'1,9-1,10:NUMBER '1'1,10-1,11: OP '+'1,11-1,12: NUMBER '1'1,12-1,13: OP '}'1,13-1,17: FSTRING_MIDDLE ' end'1,17-1,18: FSTRING_END'"'Additionally, there may be some minor behavioral changes as a consecuence of thechanges required to support PEP 701. Some of these changes include:
The type attribute of the tokens emitted when tokenizing some invalid Pythoncharacters such as ! has changed from ERRORTOKEN to OP.
Incomplete single-line strings now also raise tokenize.TokenError as incompletemultiline strings do.
Some incomplete or invalid Python code now raises tokenize.TokenError instead ofreturning arbitrary ERRORTOKEN tokens when tokenizing it.
Build Changes¶Python no longer uses setup.py to build shared C extension modules.Build parameters like headers and libraries are detected in configurescript. Extensions are built by Makefile. Most extensions usepkg-config and fall back to manual detection.(Contributed by Christian Heimes in gh-93939.)
va_start() with two parameters, like va_start(args, format),is now required to build Python.va_start() is no longer called with a single parameter.(Contributed by Kumar Aditya in gh-93207.)
CPython now uses the ThinLTO option as the default link time optimization policyif the Clang compiler accepts the flag.(Contributed by Dong-hee Na in gh-89536.)
Add COMPILEALL_OPTS variable in Makefile to override compilealloptions (default: -j0) in make install. Also merged the 3compileall commands into a single command to build .pyc files for alloptimization levels (0, 1, 2) at once.(Contributed by Victor Stinner in gh-99289.)
Add platform triplets for 64-bit LoongArch:
loongarch64-linux-gnusf
loongarch64-linux-gnuf32
loongarch64-linux-gnu
(Contributed by Zhang Na in gh-90656.)
PYTHON_FOR_REGEN now require Python 3.10 or newer.
Autoconf 2.71 and aclocal 1.16.4 is now required to regenerate!configure.(Contributed by Christian Heimes in gh-89886.)
C extensions built with the limited C APIon Python build in debug mode no longer support Python3.9 and older. In this configuration, Py_INCREF() andPy_DECREF() are now always implemented as opaque function calls,but the called functions were added to Python 3.10. Build C extensionswith a release build of Python or with Python 3.12 and older, to keep supportfor Python 3.9 and older.(Contributed by Victor Stinner in gh-102304.)
C API Changes¶New Features¶PEP 697: Introduced the Unstable C API tier,intended for low-level tools like debuggers and JIT compilers.This API may change in each minor release of CPython without deprecationwarnings.Its contents are marked by the PyUnstable_ prefix in names.
Code object constructors:
PyUnstable_Code_New() (renamed from PyCode_New)
PyUnstable_Code_NewWithPosOnlyArgs() (renamed from PyCode_NewWithPosOnlyArgs)
Extra storage for code objects (PEP 523):
PyUnstable_Eval_RequestCodeExtraIndex() (renamed from _PyEval_RequestCodeExtraIndex)
PyUnstable_Code_GetExtra() (renamed from _PyCode_GetExtra)
PyUnstable_Code_SetExtra() (renamed from _PyCode_SetExtra)
The original names will continue to be available until the respectiveAPI changes.
(Contributed by Petr Viktorin in gh-101101.)
PEP 697: Added API for extending types whose instance memory layout isopaque:
PyType_Spec.basicsize can be zero or negative to specifyinheriting or extending the base class size.
PyObject_GetTypeData() and PyType_GetTypeDataSize()added to allow access to subclass-specific instance data.
Py_TPFLAGS_ITEMS_AT_END and PyObject_GetItemData()added to allow safely extending certain variable-sized types, includingPyType_Type.
Py_RELATIVE_OFFSET added to allow definingmembers in terms of a subclass-specific struct.
(Contributed by Petr Viktorin in gh-103509.)
Added the new limited C API function PyType_FromMetaclass(),which generalizes the existing PyType_FromModuleAndSpec() usingan additional metaclass argument.(Contributed by Wenzel Jakob in gh-93012.)
API for creating objects that can be called usingthe vectorcall protocol was added to theLimited API:
Py_TPFLAGS_HAVE_VECTORCALL
PyVectorcall_NARGS()
PyVectorcall_Call()
vectorcallfunc
The Py_TPFLAGS_HAVE_VECTORCALL flag is now removed from a classwhen the class’s __call__() method is reassigned.This makes vectorcall safe to use with mutable types (i.e. heap typeswithout the immutable flag, Py_TPFLAGS_IMMUTABLETYPE).Mutable types that do not override tp_call nowinherit the Py_TPFLAGS_HAVE_VECTORCALL flag.(Contributed by Petr Viktorin in gh-93274.)
The Py_TPFLAGS_MANAGED_DICT and Py_TPFLAGS_MANAGED_WEAKREFflags have been added. This allows extensions classes to support object__dict__ and weakrefs with less bookkeeping,using less memory and with faster access.
API for performing calls usingthe vectorcall protocol was added to theLimited API:
PyObject_Vectorcall()
PyObject_VectorcallMethod()
PY_VECTORCALL_ARGUMENTS_OFFSET
This means that both the incoming and outgoing ends of the vector callprotocol are now available in the Limited API. (Contributedby Wenzel Jakob in gh-98586.)
Added two new public functions,PyEval_SetProfileAllThreads() andPyEval_SetTraceAllThreads(), that allow to set tracing and profilingfunctions in all running threads in addition to the calling one. (Contributedby Pablo Galindo in gh-93503.)
Added new function PyFunction_SetVectorcall() to the C APIwhich sets the vectorcall field of a given PyFunctionObject.(Contributed by Andrew Frost in gh-92257.)
The C API now permits registering callbacks via PyDict_AddWatcher(),PyDict_Watch() and related APIs to be called whenever a dictionaryis modified. This is intended for use by optimizing interpreters, JITcompilers, or debuggers.(Contributed by Carl Meyer in gh-91052.)
Added PyType_AddWatcher() and PyType_Watch() API to registercallbacks to receive notification on changes to a type.(Contributed by Carl Meyer in gh-91051.)
Added PyCode_AddWatcher() and PyCode_ClearWatcher()APIs to register callbacks to receive notification on creation anddestruction of code objects.(Contributed by Itamar Ostricher in gh-91054.)
Add PyFrame_GetVar() and PyFrame_GetVarString() functions toget a frame variable by its name.(Contributed by Victor Stinner in gh-91248.)
Add PyErr_GetRaisedException() and PyErr_SetRaisedException()for saving and restoring the current exception.These functions return and accept a single exception object,rather than the triple arguments of the now-deprecatedPyErr_Fetch() and PyErr_Restore().This is less error prone and a bit more efficient.(Contributed by Mark Shannon in gh-101578.)
Add _PyErr_ChainExceptions1, which takes an exception instance,to replace the legacy-API _PyErr_ChainExceptions, which is nowdeprecated. (Contributed by Mark Shannon in gh-101578.)
Add PyException_GetArgs() and PyException_SetArgs()as convenience functions for retrieving and modifyingthe args passed to the exception’s constructor.(Contributed by Mark Shannon in gh-101578.)
Add PyErr_DisplayException(), which takes an exception instance,to replace the legacy-api PyErr_Display(). (Contributed byIrit Katriel in gh-102755).
PEP 683: Introduced Immortal Objects to Python which allows objectsto bypass reference counts and introduced changes to the C-API:
_Py_IMMORTAL_REFCNT: The reference count that defines an objectas immortal.
_Py_IsImmortal Checks if an object has the immortal reference count.
PyObject_HEAD_INIT This will now initialize reference count to_Py_IMMORTAL_REFCNT when used with Py_BUILD_CORE.
SSTATE_INTERNED_IMMORTAL An identifier for interned unicode objectsthat are immortal.
SSTATE_INTERNED_IMMORTAL_STATIC An identifier for interned unicodeobjects that are immortal and static
sys.getunicodeinternedsize This returns the total number of unicodeobjects that have been interned. This is now needed for refleak.py tocorrectly track reference counts and allocated blocks
(Contributed by Eddie Elizondo in gh-84436.)
Porting to Python 3.12¶Legacy Unicode APIs based on Py_UNICODE* representation has been removed.Please migrate to APIs based on UTF-8 or wchar_t*.
Argument parsing functions like PyArg_ParseTuple() doesn’t supportPy_UNICODE* based format (e.g. u, Z) anymore. Please migrateto other formats for Unicode like s, z, es, and U.
tp_weaklist for all static builtin types is always NULL.This is an internal-only field on PyTypeObjectbut we’re pointing out the change in case someone happens to beaccessing the field directly anyway. To avoid breakage, considerusing the existing public C-API instead, or, if necessary, the(internal-only) _PyObject_GET_WEAKREFS_LISTPTR() macro.
This internal-only PyTypeObject.tp_subclasses may now not bea valid object pointer. Its type was changed to void* toreflect this. We mention this in case someone happens to be accessing theinternal-only field directly.
To get a list of subclasses, call the Python method__subclasses__() (using PyObject_CallMethod(),for example).
Add support of more formatting options (left aligning, octals, uppercasehexadecimals, intmax_t, ptrdiff_t, wchar_t Cstrings, variable width and precision) in PyUnicode_FromFormat() andPyUnicode_FromFormatV().(Contributed by Serhiy Storchaka in gh-98836.)
An unrecognized format character in PyUnicode_FromFormat() andPyUnicode_FromFormatV() now sets a SystemError.In previous versions it caused all the rest of the format string to becopied as-is to the result string, and any extra arguments discarded.(Contributed by Serhiy Storchaka in gh-95781.)
Fixed wrong sign placement in PyUnicode_FromFormat() andPyUnicode_FromFormatV().(Contributed by Philip Georgi in gh-95504.)
Extension classes wanting to add a __dict__ or weak reference slotshould use Py_TPFLAGS_MANAGED_DICT andPy_TPFLAGS_MANAGED_WEAKREF instead of tp_dictoffset andtp_weaklistoffset, respectively.The use of tp_dictoffset and tp_weaklistoffset is stillsupported, but does not fully support multiple inheritance(gh-95589), and performance may be worse.Classes declaring Py_TPFLAGS_MANAGED_DICT should call_PyObject_VisitManagedDict() and _PyObject_ClearManagedDict()to traverse and clear their instance’s dictionaries.To clear weakrefs, call PyObject_ClearWeakRefs(), as before.
The PyUnicode_FSDecoder() function no longer accepts bytes-likepaths, like bytearray and memoryview types: only the exactbytes type is accepted for bytes strings.(Contributed by Victor Stinner in gh-98393.)
The Py_CLEAR, Py_SETREF and Py_XSETREFmacros now only evaluate their arguments once. If an argument has sideeffects, these side effects are no longer duplicated.(Contributed by Victor Stinner in gh-98724.)
The interpreter’s error indicator is now always normalized. This meansthat PyErr_SetObject(), PyErr_SetString() and the otherfunctions that set the error indicator now normalize the exceptionbefore storing it. (Contributed by Mark Shannon in gh-101578.)
_Py_RefTotal is no longer authoritative and only kept aroundfor ABI compatibility. Note that it is an internal global and onlyavailable on debug builds. If you happen to be using it then you’llneed to start using _Py_GetGlobalRefTotal().
The following functions now select an appropriate metaclass for the newlycreated type:
PyType_FromSpec()
PyType_FromSpecWithBases()
PyType_FromModuleAndSpec()
Creating classes whose metaclass overrides tp_newis deprecated, and in Python 3.14+ it will be disallowed.Note that these functions ignore tp_new of the metaclass, possiblyallowing incomplete initialization.
Note that PyType_FromMetaclass() (added in Python 3.12)already disallows creating classes whose metaclass overrides tp_new.
PyOS_InputHook and PyOS_ReadlineFunctionPointer are nolonger called in subinterpreters. This isbecause clients generally rely on process-wide global state (since thesecallbacks have no way of recovering extension module state).
This also avoids situations where extensions may find themselves running in asubinterpreter that they don’t support (or haven’t yet been loaded in). Seegh-104668 for more info.
Deprecated¶Deprecate global configuration variable:
Py_DebugFlag: use PyConfig.parser_debug
Py_VerboseFlag: use PyConfig.verbose
Py_QuietFlag: use PyConfig.quiet
Py_InteractiveFlag: use PyConfig.interactive
Py_InspectFlag: use PyConfig.inspect
Py_OptimizeFlag: use PyConfig.optimization_level
Py_NoSiteFlag: use PyConfig.site_import
Py_BytesWarningFlag: use PyConfig.bytes_warning
Py_FrozenFlag: use PyConfig.pathconfig_warnings
Py_IgnoreEnvironmentFlag: use PyConfig.use_environment
Py_DontWriteBytecodeFlag: use PyConfig.write_bytecode
Py_NoUserSiteDirectory: use PyConfig.user_site_directory
Py_UnbufferedStdioFlag: use PyConfig.buffered_stdio
Py_HashRandomizationFlag: use PyConfig.use_hash_seedand PyConfig.hash_seed
Py_IsolatedFlag: use PyConfig.isolated
Py_LegacyWindowsFSEncodingFlag: use PyPreConfig.legacy_windows_fs_encoding
Py_LegacyWindowsStdioFlag: use PyConfig.legacy_windows_stdio
Py_FileSystemDefaultEncoding: use PyConfig.filesystem_encoding
Py_FileSystemDefaultEncodeErrors: use PyConfig.filesystem_errors
Py_UTF8Mode: use PyPreConfig.utf8_mode (see Py_PreInitialize())
The Py_InitializeFromConfig() API should be used withPyConfig instead.(Contributed by Victor Stinner in gh-77782.)
Creating immutable types (Py_TPFLAGS_IMMUTABLETYPE) with mutablebases is deprecated and will be disabled in Python 3.14.
The structmember.h header is deprecated, though it continues to beavailable and there are no plans to remove it.
Its contents are now available just by including Python.h,with a Py prefix added if it was missing:
PyMemberDef, PyMember_GetOne() andPyMember_SetOne()
Type macros like Py_T_INT, Py_T_DOUBLE, etc.(previously T_INT, T_DOUBLE, etc.)
The flags Py_READONLY (previously READONLY) andPy_AUDIT_READ (previously all uppercase)
Several items are not exposed from Python.h:
T_OBJECT (use Py_T_OBJECT_EX)
T_NONE (previously undocumented, and pretty quirky)
The macro WRITE_RESTRICTED which does nothing.
The macros RESTRICTED and READ_RESTRICTED, equivalents ofPy_AUDIT_READ.
In some configurations, is not included from Python.h.It should be included manually when using offsetof().
The deprecated header continues to provide its originalcontents under the original names.Your old code can stay unchanged, unless the extra include and non-namespacedmacros bother you greatly.
(Contributed in gh-47146 by Petr Viktorin, based onearlier work by Alexander Belopolsky and Matthias Braun.)
PyErr_Fetch() and PyErr_Restore() are deprecated.Use PyErr_GetRaisedException() andPyErr_SetRaisedException() instead.(Contributed by Mark Shannon in gh-101578.)
PyErr_Display() is deprecated. Use PyErr_DisplayException()instead. (Contributed by Irit Katriel in gh-102755).
_PyErr_ChainExceptions is deprecated. Use _PyErr_ChainExceptions1instead. (Contributed by Irit Katriel in gh-102192.)
Using PyType_FromSpec(), PyType_FromSpecWithBases()or PyType_FromModuleAndSpec() to create a class whose metaclassoverrides tp_new is deprecated.Call the metaclass instead.
Removed¶Remove the token.h header file. There was never any public tokenizer CAPI. The token.h header file was only designed to be used by Pythoninternals.(Contributed by Victor Stinner in gh-92651.)
Legacy Unicode APIs have been removed. See PEP 623 for detail.
PyUnicode_WCHAR_KIND
PyUnicode_AS_UNICODE()
PyUnicode_AsUnicode()
PyUnicode_AsUnicodeAndSize()
PyUnicode_AS_DATA()
PyUnicode_FromUnicode()
PyUnicode_GET_SIZE()
PyUnicode_GetSize()
PyUnicode_GET_DATA_SIZE()
Remove the PyUnicode_InternImmortal() function macro.(Contributed by Victor Stinner in gh-85858.)
Remove Jython compatibility hacks from several stdlib modules and tests.(Contributed by Nikita Sobolev in gh-99482.)
Remove _use_broken_old_ctypes_structure_semantics_ flagfrom ctypes module.(Contributed by Nikita Sobolev in gh-99285.)