PEP 695: Type Parameter Syntax¶

Generic classes and functions underPEP 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 andfunctions:

defmax[T](args:Iterable[T])->T:...classlist[T]:def__getitem__(self,index:int,/)->T:...defappend(self,element:T)->None:...

In addition, the PEP introduces a new way to declaretype aliasesusing thetype statement, which creates an instance ofTypeAliasType:

typePoint=tuple[float,float]

Type aliases can also begeneric:

typePoint[T]=tuple[T,T]

The new syntax allows declaringTypeVarTupleandParamSpec parameters, as well asTypeVarparameters with bounds or constraints:

typeIntFunc[**P]=Callable[P,int]# ParamSpectypeLabeledTuple[*Ts]=tuple[str,*Ts]# TypeVarTupletypeHashableSequence[T:Hashable]=Sequence[T]# TypeVar with boundtypeIntOrStrSequence[T:(int,str)]=Sequence[T]# TypeVar with constraints

The 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 torefer to other types 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. SeeType 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,theannotation 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.

SeePEP 695 for more details.

(PEP written by Eric Traut. Implementation by Jelle Zijlstra, Eric Traut,and others ingh-103764.)

PEP 701: Syntactic formalization of f-strings¶

PEP 701 lifts some restrictions on the usage off-strings.Expression components inside f-strings can now be any valid Python expression,including strings reusing the same quote as the containing f-string,multi-line expressions, comments, backslashes, and unicode escape sequences.Let’s cover these in detail:

• Quote reuse: in Python 3.11, reusing the same quotes as the enclosing f-stringraises aSyntaxError, 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-string expressionsmust be defined in a single line, even if the expression within the f-stringcould normally span multiple lines(like literal lists being defined over multiple lines),making them harder to read. In Python 3.12 you can now define f-stringsspanning multiple lines, and add inline comments:

  >>> 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 unicodeescapesequences (such as\N{snowman}) as these containthe\N part that previously could not be part of expression components off-strings. Now, you can 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♥Ascensionism

SeePEP 701 for more details.

As a positive side-effect of how this feature has been implemented (by parsing f-stringswiththe PEG parser), 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 aSyntaxError:

>>>my_string=f"{xzy}"+f"{1+1}"  File"<stdin>", line1(xzy)^^^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"{xzy}"+f"{1+1}"  File"<stdin>", line1my_string=f"{xzy}"+f"{1+1}"^^^SyntaxError:invalid syntax. Perhaps you forgot a comma?

(Contributed by Pablo Galindo, Batuhan Taskaya, Lysandros Nikolaou, CristiánMaureira-Fredes and Marta Gómez ingh-102856. PEP written by Pablo Galindo,Batuhan Taskaya, Lysandros Nikolaou and Marta Gómez).

PEP 684: A Per-Interpreter GIL¶

PEP 684 introduces a per-interpreterGIL,so that sub-interpreters may now be created with a unique GIL per interpreter.This allows Python programs to take full advantage of multiple CPUcores. This is currently only available through the C-API,though a Python API isanticipated for 3.13.

Use the newPy_NewInterpreterFromConfig() function tocreate an interpreter with its own GIL:

PyInterpreterConfigconfig={.check_multi_interp_extensions=1,.gil=PyInterpreterConfig_OWN_GIL,};PyThreadState*tstate=NULL;PyStatusstatus=Py_NewInterpreterFromConfig(&tstate,&config);if(PyStatus_Exception(status)){return-1;}/* The new interpreter is now active in the current thread. */

For further examples how to use the C-API for sub-interpreters with aper-interpreter GIL, seeModules/_xxsubinterpretersmodule.c.

(Contributed by Eric Snow ingh-104210, etc.)

PEP 669: Low impact monitoring for CPython¶

PEP 669 defines a newAPI for profilers,debuggers, and other tools to monitor events in CPython.It covers a wide range of events, including calls,returns, lines, exceptions, jumps, and more.This means that you only pay for what you use, providing supportfor near-zero overhead debuggers and coverage tools.Seesys.monitoring for details.

(Contributed by Mark Shannon ingh-103082.)

PEP 688: Making the buffer protocol accessible in Python¶

PEP 688 introduces a way to use thebuffer protocolfrom Python code. Classes that implement the__buffer__() methodare now usable as buffer types.

The newcollections.abc.Buffer ABC provides a standardway to represent buffer objects, for example in type annotations.The newinspect.BufferFlags enum represents the flags thatcan be used to customize buffer creation.(Contributed by Jelle Zijlstra ingh-102500.)

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 two times.SeePEP 709 for further details.

Comprehension iteration variables remain isolated and don’t overwrite avariable of the same name in the outer scope, nor are they visible after thecomprehension. 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.

• Thesymtable module will no longer produce child symbol tables for eachcomprehension; instead, the comprehension’s locals will be included in theparent function’s symbol table.

• Callinglocals() inside a comprehension now includes variablesfrom outside the comprehension, and no longer includes the synthetic.0variable for the comprehension “argument”.

• A comprehension iterating directly overlocals() (e.g.[kforkinlocals()]) may see “RuntimeError: dictionary changed size during iteration”when run under tracing (e.g. code coverage measurement). This is the samebehavior already seen in e.g.forkinlocals():. To avoid the error, firstcreate a list of keys to iterate over:keys=list(locals());[kforkinkeys].

(Contributed by Carl Meyer and Vladimir Matveev inPEP 709.)

Improved Error Messages¶

• Modules from the standard library are now potentially suggested as part ofthe error messages displayed by the interpreter when aNameError israised to the top level. (Contributed by Pablo Galindo ingh-98254.)

  >>>sys.version_infoTraceback (most recent call last):  File"<stdin>", line1, in<module>NameError:name 'sys' is not defined. Did you forget to import 'sys'?

• Improve the error suggestion forNameError exceptions for instances.Now if aNameError is raised in a method and the instance has anattribute that’s exactly equal to the name in the exception, the suggestionwill includeself.<NAME> instead of the closest match in the methodscope. (Contributed by Pablo Galindo ingh-99139.)

  >>>classA:...def__init__(self):...self.blech=1......deffoo(self):...somethin=blech...>>>A().foo()Traceback (most recent call last):  File"<stdin>", line1somethin=blech^^^^^NameError:name 'blech' is not defined. Did you mean: 'self.blech'?

• Improve theSyntaxError error message when the user typesimportxfromy instead offromyimportx. (Contributed by Pablo Galindo ingh-98931.)

  >>>importa.y.zfromb.y.zTraceback (most recent call last):  File"<stdin>", line1importa.y.zfromb.y.z^^^^^^^^^^^^^^^^^^^^^^^SyntaxError:Did you mean to use 'from ... import ...' instead?

• ImportError exceptions raised from failedfrom<module>import<name> statements now include suggestions for the value of<name> based on theavailable names in<module>. (Contributed by Pablo Galindo ingh-91058.)

  >>>fromcollectionsimportchainmapTraceback (most recent call last):  File"<stdin>", line1, in<module>ImportError:cannot import name 'chainmap' from 'collections'. Did you mean: 'ChainMap'?

PEP 692: UsingTypedDict for more precise**kwargs typing¶

Typing**kwargs in a function signature as introduced byPEP 484 allowedfor valid annotations only in cases where all of the**kwargs were of thesame type.

PEP 692 specifies a more precise way of typing**kwargs by relying ontyped dictionaries:

fromtypingimportTypedDict,UnpackclassMovie(TypedDict):name:stryear:intdeffoo(**kwargs:Unpack[Movie]):...

SeePEP 692 for more details.

(Contributed by Franek Magiera ingh-103629.)

PEP 698: Override Decorator for Static Typing¶

A new decoratortyping.override() has been added to thetypingmodule. 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:

fromtypingimportoverrideclassBase:defget_color(self)->str:return"blue"classGoodChild(Base):@override# ok: overrides Base.get_colordefget_color(self)->str:return"yellow"classBadChild(Base):@override# type checker error: does not override Base.get_colordefget_colour(self)->str:return"red"

SeePEP 698 for more details.

(Contributed by Steven Troxler ingh-101561.)

array¶

• Thearray.array class now supports subscripting, making it ageneric type. (Contributed by Jelle Zijlstra ingh-98658.)

asyncio¶

• The performance of writing to sockets inasyncio has beensignificantly improved.asyncio now avoids unnecessary copying whenwriting to sockets and usessendmsg() if the platformsupports it. (Contributed by Kumar Aditya ingh-91166.)

• Addasyncio.eager_task_factory() andasyncio.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 Oren ingh-102853,gh-104140, andgh-104138)

• On Linux,asyncio usesasyncio.PidfdChildWatcher by defaultifos.pidfd_open() is available and functional instead ofasyncio.ThreadedChildWatcher.(Contributed by Kumar Aditya ingh-98024.)

• The event loop now uses the best available child watcher for each platform(asyncio.PidfdChildWatcher if supported andasyncio.ThreadedChildWatcher otherwise), so manuallyconfiguring a child watcher is not recommended.(Contributed by Kumar Aditya ingh-94597.)

• Addloop_factory parameter toasyncio.run() to allow specifyinga custom event loop factory.(Contributed by Kumar Aditya ingh-99388.)

• Add C implementation ofasyncio.current_task() for 4x-6x speedup.(Contributed by Itamar Oren and Pranav Thulasiram Bhat ingh-100344.)

• asyncio.iscoroutine() now returnsFalse for generators asasyncio does not support legacy generator-based coroutines.(Contributed by Kumar Aditya ingh-102748.)

• asyncio.wait() andasyncio.as_completed() now accepts generatorsyielding tasks.(Contributed by Kumar Aditya ingh-78530.)

calendar¶

• Add enumscalendar.Month andcalendar.Daydefining months of the year and days of the week.(Contributed by Prince Roshan ingh-103636.)

csv¶

• Addcsv.QUOTE_NOTNULL andcsv.QUOTE_STRINGS flags toprovide finer grained control ofNone and empty strings byreader andwriter 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 newdis.hasarg collection instead.(Contributed by Irit Katriel ingh-94216.)

• Add thedis.hasexc collection to signify instructions that setan exception handler. (Contributed by Irit Katriel ingh-94216.)

fractions¶

• Objects of typefractions.Fraction now support float-styleformatting. (Contributed by Mark Dickinson ingh-100161.)

importlib.resources¶

• importlib.resources.as_file() now supports resource directories.(Contributed by Jason R. Coombs ingh-97930.)

• Rename first parameter ofimportlib.resources.files() toanchor.(Contributed by Jason R. Coombs ingh-100598.)

inspect¶

• Addinspect.markcoroutinefunction() to mark sync functions that returnacoroutine for use withinspect.iscoroutinefunction().(Contributed by Carlton Gibson ingh-99247.)

• Addinspect.getasyncgenstate() andinspect.getasyncgenlocals()for determining the current state of asynchronous generators.(Contributed by Thomas Krennwallner ingh-79940.)

• The performance ofinspect.getattr_static() has been considerablyimproved. Most calls to the function should be at least 2x faster than theywere in Python 3.11. (Contributed by Alex Waygood ingh-103193.)

itertools¶

• Additertools.batched() for collecting into even-sizedtuples where the last batch may be shorter than the rest.(Contributed by Raymond Hettinger ingh-98363.)

math¶

• Addmath.sumprod() for computing a sum of products.(Contributed by Raymond Hettinger ingh-100485.)

• Extendmath.nextafter() to include asteps argumentfor moving up or down multiple steps at a time. (Contributed byMatthias Goergens, Mark Dickinson, and Raymond Hettinger ingh-94906.)

os¶

• Addos.PIDFD_NONBLOCK to open a file descriptorfor a process withos.pidfd_open() in non-blocking mode.(Contributed by Kumar Aditya ingh-93312.)

• os.DirEntry now includes anos.DirEntry.is_junction()method to check if the entry is a junction.(Contributed by Charles Machalow ingh-99547.)

• Addos.listdrives(),os.listvolumes() andos.listmounts()functions on Windows for enumerating drives, volumes and mount points.(Contributed by Steve Dower ingh-102519.)

• os.stat() andos.lstat() are now more accurate on Windows.Thest_birthtime field will now be filled with the creation timeof the file, andst_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 bitsandst_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 ingh-99726.)

os.path¶

• Addos.path.isjunction() to check if a given path is a junction.(Contributed by Charles Machalow ingh-99547.)

• Addos.path.splitroot() to split a path into a triad(drive,root,tail). (Contributed by Barney Gale ingh-101000.)

pathlib¶

• Add support for subclassingpathlib.PurePath andpathlib.Path, plus their Posix- and Windows-specific variants.Subclasses may override thepathlib.PurePath.with_segments() methodto pass information between path instances.

• Addpathlib.Path.walk() for walking the directory trees and generatingall file or directory names within them, similar toos.walk().(Contributed by Stanislav Zmiev ingh-90385.)

• Addwalk_up optional parameter topathlib.PurePath.relative_to()to allow the insertion of.. entries in the result; this behavior ismore consistent withos.path.relpath().(Contributed by Domenico Ragusa ingh-84538.)

• Addpathlib.Path.is_junction() as a proxy toos.path.isjunction().(Contributed by Charles Machalow ingh-99547.)

• Addcase_sensitive optional parameter topathlib.Path.glob(),pathlib.Path.rglob() andpathlib.PurePath.match() for matchingthe path’s case sensitivity, allowing for more precise control over the matching process.

platform¶

• Add support for detecting Windows 11 and Windows Server releases past 2012.Previously, lookups on Windows Server platforms newer than Windows Server 2012and on Windows 11 would returnWindows-10.(Contributed by Steve Dower ingh-89545.)

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 ingh-103693.)

random¶

• Addrandom.binomialvariate().(Contributed by Raymond Hettinger ingh-81620.)

• Add a default oflambd=1.0 torandom.expovariate().(Contributed by Raymond Hettinger ingh-100234.)

shutil¶

• shutil.make_archive() now passes theroot_dir argument to customarchivers which support it.In this case it no longer temporarily changes the current working directoryof the process toroot_dir to perform archiving.(Contributed by Serhiy Storchaka ingh-74696.)

• shutil.rmtree() now accepts a new argumentonexc which is anerror handler likeonerror but which expects an exception instancerather than a(typ, val, tb) triplet.onerror is deprecated.(Contributed by Irit Katriel ingh-102828.)

• shutil.which() now consults thePATHEXT environment variable tofind matches withinPATH on Windows even when the givencmd includesa directory component.(Contributed by Charles Machalow ingh-103179.)

  shutil.which() will callNeedCurrentDirectoryForExePathW whenquerying for executables on Windows to determine if the current workingdirectory should be prepended to the search path.(Contributed by Charles Machalow ingh-103179.)

  shutil.which() will return a path matching thecmd with a componentfromPATHEXT prior to a direct match elsewhere in the search path onWindows.(Contributed by Charles Machalow ingh-103179.)

sqlite3¶

• Add acommand-line interface.(Contributed by Erlend E. Aasland ingh-77617.)

• Add thesqlite3.Connection.autocommit attributetosqlite3.Connectionand theautocommit parameter tosqlite3.connect()to controlPEP 249-complianttransaction handling.(Contributed by Erlend E. Aasland ingh-83638.)

• Addentrypoint keyword-only parameter tosqlite3.Connection.load_extension(),for overriding the SQLite extension entry point.(Contributed by Erlend E. Aasland ingh-103015.)

• Addsqlite3.Connection.getconfig() andsqlite3.Connection.setconfig() tosqlite3.Connectionto make configuration changes to a database connection.(Contributed by Erlend E. Aasland ingh-103489.)

statistics¶

• Extendstatistics.correlation() to include as aranked methodfor computing the Spearman correlation of ranked data.(Contributed by Raymond Hettinger ingh-95861.)

sys¶

• Add thesys.monitoring namespace to expose the newPEP 669 monitoring API.(Contributed by Mark Shannon ingh-103082.)

• Addsys.activate_stack_trampoline() andsys.deactivate_stack_trampoline() for activating and deactivatingstack profiler trampolines,andsys.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 Shannoningh-96123.)

• Addsys.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 andsys.last_traceback.(Contributed by Irit Katriel ingh-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 ingh-103176.)

• sys.setrecursionlimit() andsys.getrecursionlimit().The recursion limit now applies only to Python code. Builtin functions donot use the recursion limit, but are protected by a different mechanismthat prevents recursion from causing a virtual machine crash.

tempfile¶

• Thetempfile.NamedTemporaryFile function has a new optional parameterdelete_on_close (Contributed by Evgeny Zorin ingh-58451.)

• tempfile.mkdtemp() now always returns an absolute path, even if theargument provided to thedir parameter is a relative path.

threading¶

• Addthreading.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 ingh-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),...]),likecreate_*() methods.(Contributed by Serhiy Storchaka ingh-94473.)

tokenize¶

• Thetokenize module includes the changes introduced inPEP 701.(Contributed by Marta Gómez Macías and Pablo Galindo ingh-102856.)SeePorting to Python 3.12 for more information on thechanges to thetokenize module.

types¶

• Addtypes.get_original_bases() to allow for further introspection ofUser-defined generic types when subclassed. (Contributed byJames Hilton-Balfe and Alex Waygood ingh-101827.)

typing¶

• isinstance() checks againstruntime-checkableprotocols now useinspect.getattr_static() rather thanhasattr() to lookup whetherattributes exist. This means that descriptors and__getattr__()methods are no longer unexpectedly evaluated duringisinstance() 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 ingh-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:

  >>>fromtypingimportProtocol,runtime_checkable>>>@runtime_checkable...classHasX(Protocol):...x=1...>>>classFoo:......>>>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" attributeTrue

  This change was made in order to speed upisinstance() checks againstruntime-checkable protocols.

• The performance profile ofisinstance() checks againstruntime-checkableprotocols has changedsignificantly. Mostisinstance() 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 manymembers may be slower than in Python 3.11. (Contributed by AlexWaygood ingh-74690 andgh-103193.)

• Alltyping.TypedDict andtyping.NamedTuple classes now have the__orig_bases__ attribute. (Contributed by Adrian Garcia Badaracco ingh-103699.)

• Addfrozen_default parameter totyping.dataclass_transform().(Contributed by Erik De Bonte ingh-99957.)

unicodedata¶

• The Unicode database has been updated to version 15.0.0. (Contributed byBenjamin Peterson ingh-96734).

unittest¶

Add a--durations command line option, showing the N slowest test cases:

python3-munittest--durations=3lib.tests.test_threading.....Slowesttestdurations----------------------------------------------------------------------1.210stest_timeout(Lib.test.test_threading.BarrierTests)1.003stest_default_timeout(Lib.test.test_threading.BarrierTests)0.518stest_timeout(Lib.test.test_threading.EventTests)(0.000durationshidden.Use-vtoshowthesedurations.)----------------------------------------------------------------------Ran158testsin9.869sOK(skipped=3)

(Contributed by Giampaolo Rodola ingh-48330)

uuid¶

• Add acommand-line interface.(Contributed by Adam Chhina ingh-88597.)

Pending removal in Python 3.13¶

Modules (seePEP 594):

• aifc

• audioop

• cgi

• cgitb

• chunk

• crypt

• imghdr

• mailcap

• msilib

• nis

• nntplib

• ossaudiodev

• pipes

• sndhdr

• spwd

• sunau

• telnetlib

• uu

• xdrlib

Other modules:

• lib2to3, and the2to3 program (gh-84540)

APIs:

• configparser.LegacyInterpolation (gh-90765)

• locale.resetlocale() (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¶

• argparse: Thetype,choices, andmetavar parametersofargparse.BooleanOptionalAction are deprecatedand will be removed in 3.14.(Contributed by Nikita Sobolev ingh-92248.)

• ast: The following features have been deprecated in documentationsince Python 3.8, now cause aDeprecationWarning to be emitted atruntime when they are accessed or used, and will be removed in Python 3.14:

  • ast.Num

  • ast.Str

  • ast.Bytes

  • ast.NameConstant

  • ast.Ellipsis

  Useast.Constant instead.(Contributed by Serhiy Storchaka ingh-90953.)

• asyncio:

  • The child watcher classesasyncio.MultiLoopChildWatcher,asyncio.FastChildWatcher,asyncio.AbstractChildWatcherandasyncio.SafeChildWatcher are deprecated andwill be removed in Python 3.14.(Contributed by Kumar Aditya ingh-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 ingh-94597.)

  • Theget_event_loop() method of thedefault event loop policy now emits aDeprecationWarning if thereis no current event loop set and it decides to create one.(Contributed by Serhiy Storchaka and Guido van Rossum ingh-100160.)

• email: Deprecated theisdst parameter inemail.utils.localtime().(Contributed by Alan Williams ingh-72346.)

• importlib.abc deprecated classes:

  • importlib.abc.ResourceReader

  • importlib.abc.Traversable

  • importlib.abc.TraversableResources

  Useimportlib.resources.abc classes instead:

  • importlib.resources.abc.Traversable

  • importlib.resources.abc.TraversableResources

  (Contributed by Jason R. Coombs and Hugo van Kemenade ingh-93963.)

• 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 ingh-101588.)

• multiprocessing: The default 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 coderequires'fork'. SeeContexts and start methods.

• pathlib:is_relative_to() andrelative_to(): passing additional arguments isdeprecated.

• pkgutil:pkgutil.find_loader() andpkgutil.get_loader()now raiseDeprecationWarning;useimportlib.util.find_spec() instead.(Contributed by Nikita Sobolev ingh-97850.)

• pty:

  • master_open(): usepty.openpty().

  • slave_open(): usepty.openpty().

• sqlite3:

  • version andversion_info.

  • execute() andexecutemany()ifnamed placeholders are used andparameters is a sequence instead of adict.

• urllib:urllib.parse.Quoter is deprecated: it was not intended to be apublic API.(Contributed by Gregory P. Smith ingh-88168.)

Pending removal in Python 3.15¶

• The import system:

  • Setting__cached__ on a module whilefailing to set__spec__.cachedis deprecated. In Python 3.15,__cached__ will cease to be set ortake into consideration by the import system or standard library. (gh-97879)

  • Setting__package__ on a module whilefailing to set__spec__.parentis deprecated. In Python 3.15,__package__ will cease to be set ortake into consideration by the import system or standard library. (gh-97879)

• ctypes:

  • The undocumentedctypes.SetPointerType() functionhas been deprecated since Python 3.13.

• http.server:

  • The obsolete and rarely usedCGIHTTPRequestHandlerhas been deprecated since Python 3.13.No direct replacement exists.Anything is better than CGI to interfacea web server with a request handler.

  • The--cgi flag to thepython -m http.servercommand-line interface has been deprecated since Python 3.13.

• importlib:

  • load_module() method: useexec_module() instead.

• locale:

  • Thegetdefaultlocale() functionhas been deprecated since Python 3.11.Its removal was originally planned for Python 3.13 (gh-90817),but has been postponed to Python 3.15.Usegetlocale(),setlocale(),andgetencoding() instead.(Contributed by Hugo van Kemenade ingh-111187.)

• pathlib:

  • .PurePath.is_reserved()has been deprecated since Python 3.13.Useos.path.isreserved() to detect reserved paths on Windows.

• platform:

  • platform.java_ver() has been deprecated since Python 3.13.This function is only useful for Jython support, has a confusing API,and is largely untested.

• sysconfig:

  • Thecheck_home argument ofsysconfig.is_python_build() has beendeprecated since Python 3.12.

• threading:

  • RLock() will take no arguments in Python 3.15.Passing any arguments has been deprecated since Python 3.14,as the Python version does not permit any arguments,but the C version allows any number of positional or keyword arguments,ignoring every argument.

• types:

  • types.CodeType: Accessingco_lnotab wasdeprecated inPEP 626since 3.10 and was planned to be removed in 3.12,but it only got a properDeprecationWarning in 3.12.May be removed in 3.15.(Contributed by Nikita Sobolev ingh-101866.)

• typing:

  • The undocumented keyword argument syntax for creatingNamedTuple classes(for example,Point=NamedTuple("Point",x=int,y=int))has been deprecated since Python 3.13.Use the class-based syntax or the functional syntax instead.

  • When using the functional syntax ofTypedDicts, failingto pass a value to thefields parameter (TD=TypedDict("TD")) orpassingNone (TD=TypedDict("TD",None)) has been deprecatedsince Python 3.13.UseclassTD(TypedDict):pass orTD=TypedDict("TD",{})to create a TypedDict with zero field.

  • Thetyping.no_type_check_decorator() decorator functionhas been deprecated since Python 3.13.After eight years in thetyping module,it has yet to be supported by any major type checker.

• sre_compile,sre_constants andsre_parse modules.

• wave:

  • Thegetmark(),setmark() andgetmarkers() methods oftheWave_read andWave_write classeshave been deprecated since Python 3.13.

• zipimport:

  • zipimport.zipimporter.load_module() has been deprecated sincePython 3.10. Useexec_module() instead.(gh-125746.)

Pending removal in Python 3.16¶

• The import system:

  • Setting__loader__ on a module whilefailing to set__spec__.loaderis deprecated. In Python 3.16,__loader__ will cease to be set ortaken into consideration by the import system or the standard library.

• array:

  • The'u' format code (wchar_t)has been deprecated in documentation since Python 3.3and at runtime since Python 3.13.Use the'w' format code (Py_UCS4)for Unicode characters instead.

• asyncio:

  • asyncio.iscoroutinefunction() is deprecatedand will be removed in Python 3.16;useinspect.iscoroutinefunction() instead.(Contributed by Jiahao Li and Kumar Aditya ingh-122875.)

  • asyncio policy system is deprecated and will be removed in Python 3.16.In particular, the following classes and functions are deprecated:

    • asyncio.AbstractEventLoopPolicy

    • asyncio.DefaultEventLoopPolicy

    • asyncio.WindowsSelectorEventLoopPolicy

    • asyncio.WindowsProactorEventLoopPolicy

    • asyncio.get_event_loop_policy()

    • asyncio.set_event_loop_policy()

    Users should useasyncio.run() orasyncio.Runner withloop_factory to use the desired event loop implementation.

    For example, to useasyncio.SelectorEventLoop on Windows:

    importasyncioasyncdefmain():...asyncio.run(main(),loop_factory=asyncio.SelectorEventLoop)

    (Contributed by Kumar Aditya ingh-127949.)

• builtins:

  • Bitwise inversion on boolean types,~True or~Falsehas been deprecated since Python 3.12,as it produces surprising and unintuitive results (-2 and-1).Usenotx instead for the logical negation of a Boolean.In the rare case that you need the bitwise inversion ofthe underlying integer, convert toint explicitly (~int(x)).

• functools:

  • Calling the Python implementation offunctools.reduce() withfunctionorsequence as keyword arguments has been deprecated since Python 3.14.

• logging:

  • Support for custom logging handlers with thestrm argument is deprecatedand scheduled for removal in Python 3.16. Define handlers with thestreamargument instead. (Contributed by Mariusz Felisiak ingh-115032.)

• mimetypes:

  • Valid extensions start with a ‘.’ or are empty formimetypes.MimeTypes.add_type().Undotted extensions are deprecated and willraise aValueError in Python 3.16.(Contributed by Hugo van Kemenade ingh-75223.)

• shutil:

  • TheExecError exceptionhas been deprecated since Python 3.14.It has not been used by any function inshutil since Python 3.4,and is now an alias ofRuntimeError.

• symtable:

  • TheClass.get_methods methodhas been deprecated since Python 3.14.

• sys:

  • The_enablelegacywindowsfsencoding() functionhas been deprecated since Python 3.13.Use thePYTHONLEGACYWINDOWSFSENCODING environment variable instead.

• sysconfig:

  • Thesysconfig.expand_makefile_vars() functionhas been deprecated since Python 3.14.Use thevars argument ofsysconfig.get_paths() instead.

• tarfile:

  • The undocumented and unusedTarFile.tarfile attributehas been deprecated since Python 3.13.

Pending removal in Python 3.17¶

• collections.abc:

  • collections.abc.ByteString is scheduled for removal in Python 3.17.

    Useisinstance(obj,collections.abc.Buffer) to test ifobjimplements thebuffer protocol at runtime. For usein type annotations, either useBuffer or a unionthat explicitly specifies the types your code supports (e.g.,bytes|bytearray|memoryview).

    ByteString was originally intended to be an abstract class thatwould serve as a supertype of bothbytes andbytearray.However, since the ABC never had any methods, knowing that an object was aninstance ofByteString never actually told you anything usefulabout the object. Other common buffer types such asmemoryviewwere also never understood as subtypes ofByteString (either atruntime or by static type checkers).

    SeePEP 688 for more details.(Contributed by Shantanu Jain ingh-91896.)

• encodings:

  • Passing non-asciiencoding names toencodings.normalize_encoding()is deprecated and scheduled for removal in Python 3.17.(Contributed by Stan Ulbrych ingh-136702)

• typing:

  • Before Python 3.14, old-style unions were implemented using the private classtyping._UnionGenericAlias. This class is no longer needed for the implementation,but it has been retained for backward compatibility, with removal scheduled for Python3.17. Users should use documented introspection helpers liketyping.get_origin()andtyping.get_args() instead of relying on private implementation details.

  • typing.ByteString, deprecated since Python 3.9, is scheduled for removal inPython 3.17.

    Useisinstance(obj,collections.abc.Buffer) to test ifobjimplements thebuffer protocol at runtime. For usein type annotations, either useBuffer or a unionthat explicitly specifies the types your code supports (e.g.,bytes|bytearray|memoryview).

    ByteString was originally intended to be an abstract class thatwould serve as a supertype of bothbytes andbytearray.However, since the ABC never had any methods, knowing that an object was aninstance ofByteString never actually told you anything usefulabout the object. Other common buffer types such asmemoryviewwere also never understood as subtypes ofByteString (either atruntime or by static type checkers).

    SeePEP 688 for more details.(Contributed by Shantanu Jain ingh-91896.)

Pending removal in Python 3.19¶

• ctypes:

  • Implicitly switching to the MSVC-compatible struct layout by setting_pack_ but not_layout_on non-Windows platforms.

• hashlib:

  • In hash function constructors such asnew() or thedirect hash-named constructors such asmd5() andsha256(), their optional initial data parameter couldalso be passed a keyword argument nameddata= orstring= invarioushashlib implementations.

    Support for thestring keyword argument name is now deprecatedand slated for removal in Python 3.19.

    Before Python 3.13, thestring keyword parameter was not correctlysupported depending on the backend implementation of hash functions.Prefer passing the initial data as a positional argument for maximumbackwards compatibility.

Pending removal in Python 3.20¶

• The__version__ attribute has been deprecated in these standard librarymodules and will be removed in Python 3.20.Usesys.version_info instead.

  • argparse

  • csv

  • ctypes

  • ctypes.macholib

  • decimal (usedecimal.SPEC_VERSION instead)

  • http.server

  • imaplib

  • ipaddress

  • json

  • logging (__date__ also deprecated)

  • optparse

  • pickle

  • platform

  • re

  • socketserver

  • tabnanny

  • tkinter.font

  • tkinter.ttk

  • wsgiref.simple_server

  • zlib

  (Contributed by Hugo van Kemenade and Stan Ulbrych ingh-76007.)

Pending removal in future versions¶

The following APIs will be removed in the future,although there is currently no date scheduled for their removal.

• argparse:

  • Nesting argument groups and nesting mutually exclusivegroups are deprecated.

  • Passing the undocumented keyword argumentprefix_chars toadd_argument_group() is nowdeprecated.

  • Theargparse.FileType type converter is deprecated.

• builtins:

  • Generators:throw(type,exc,tb) andathrow(type,exc,tb)signature is deprecated: usethrow(exc) andathrow(exc) instead,the single argument signature.

  • Currently Python accepts numeric literals immediately followed by keywords,for example0inx,1orx,0if1else2. It allows confusing andambiguous expressions like[0x1forxiny] (which can be interpreted as[0x1forxiny] or[0x1forxiny]). A syntax warning is raisedif the numeric literal is immediately followed by one of keywordsand,else,for,if,in,is andor. In a future release itwill be changed to a syntax error. (gh-87999)

  • Support for__index__() and__int__() method returning non-int type:these methods will be required to return an instance of a strict subclass ofint.

  • Support for__float__() method returning a strict subclass offloat: these methods will be required to return an instance offloat.

  • Support for__complex__() method returning a strict subclass ofcomplex: these methods will be required to return an instance ofcomplex.

  • Delegation ofint() to__trunc__() method.

  • Passing a complex number as thereal orimag argument in thecomplex() constructor is now deprecated; it should only be passedas a single positional argument.(Contributed by Serhiy Storchaka ingh-109218.)

• calendar:calendar.January andcalendar.February constants aredeprecated and replaced bycalendar.JANUARY andcalendar.FEBRUARY.(Contributed by Prince Roshan ingh-103636.)

• codecs: useopen() instead ofcodecs.open(). (gh-133038)

• codeobject.co_lnotab: use thecodeobject.co_lines() methodinstead.

• datetime:

  • utcnow():usedatetime.datetime.now(tz=datetime.UTC).

  • utcfromtimestamp():usedatetime.datetime.fromtimestamp(timestamp,tz=datetime.UTC).

• gettext: Plural value must be an integer.

• importlib:

  • cache_from_source()debug_override parameter isdeprecated: use theoptimization parameter instead.

• importlib.metadata:

  • EntryPoints tuple interface.

  • ImplicitNone on return values.

• logging: thewarn() method has been deprecatedsince Python 3.3, usewarning() instead.

• mailbox: Use of StringIO input and text mode is deprecated, useBytesIO and binary mode instead.

• os: Callingos.register_at_fork() in a multi-threaded process.

• pydoc.ErrorDuringImport: A tuple value forexc_info parameter isdeprecated, use an exception instance.

• re: More strict rules are now applied for numerical group referencesand group names in regular expressions. Only sequence of ASCII digits is nowaccepted as a numerical reference. The group name in bytes patterns andreplacement strings can now only contain ASCII letters and digits andunderscore.(Contributed by Serhiy Storchaka ingh-91760.)

• shutil:rmtree()’sonerror parameter is deprecated inPython 3.12; use theonexc parameter instead.

• ssl options and protocols:

  • ssl.SSLContext without protocol argument is deprecated.

  • ssl.SSLContext:set_npn_protocols() andselected_npn_protocol() are deprecated: use ALPNinstead.

  • ssl.OP_NO_SSL* options

  • ssl.OP_NO_TLS* options

  • ssl.PROTOCOL_SSLv3

  • ssl.PROTOCOL_TLS

  • ssl.PROTOCOL_TLSv1

  • ssl.PROTOCOL_TLSv1_1

  • ssl.PROTOCOL_TLSv1_2

  • ssl.TLSVersion.SSLv3

  • ssl.TLSVersion.TLSv1

  • ssl.TLSVersion.TLSv1_1

• threading methods:

  • threading.Condition.notifyAll(): usenotify_all().

  • threading.Event.isSet(): useis_set().

  • threading.Thread.isDaemon(),threading.Thread.setDaemon():usethreading.Thread.daemon attribute.

  • threading.Thread.getName(),threading.Thread.setName():usethreading.Thread.name attribute.

  • threading.currentThread(): usethreading.current_thread().

  • threading.activeCount(): usethreading.active_count().

• typing.Text (gh-92332).

• The internal classtyping._UnionGenericAlias is no longer used to implementtyping.Union. To preserve compatibility with users using this privateclass, a compatibility shim will be provided until at least Python 3.17. (Contributed byJelle Zijlstra ingh-105499.)

• unittest.IsolatedAsyncioTestCase: it is deprecated to return a valuethat is notNone from a test case.

• urllib.parse deprecated functions:urlparse() instead

  • splitattr()

  • splithost()

  • splitnport()

  • splitpasswd()

  • splitport()

  • splitquery()

  • splittag()

  • splittype()

  • splituser()

  • splitvalue()

  • to_bytes()

• wsgiref:SimpleHandler.stdout.write() should not do partialwrites.

• xml.etree.ElementTree: Testing the truth value of anElement is deprecated. In a future release itwill always returnTrue. Prefer explicitlen(elem) orelemisnotNone tests instead.

• sys._clear_type_cache() is deprecated:usesys._clear_internal_caches() instead.

asynchat and asyncore¶

• These two modules have been removedaccording to the schedule inPEP 594,having been deprecated in Python 3.6.Useasyncio instead.(Contributed by Nikita Sobolev ingh-96580.)

configparser¶

• Several names deprecated in theconfigparser way back in 3.2 havebeen removed pergh-89336:

  • configparser.ParsingError no longer has afilename attributeor argument. Use thesource attribute and argument instead.

  • configparser no longer has aSafeConfigParser class. Use theshorterConfigParser name instead.

  • configparser.ConfigParser no longer has areadfp method.Useread_file() instead.

distutils¶

• Remove thedistutils package. It was deprecated in Python 3.10 byPEP 632 “Deprecate distutils module”. For projects still usingdistutils and cannot be updated to something else, thesetuptoolsproject can be installed: it still providesdistutils.(Contributed by Victor Stinner ingh-92584.)

ensurepip¶

• Remove the bundled setuptools wheel fromensurepip,and stop installing setuptools in environments created byvenv.

  pip(>=22.1) does not require setuptools to be installed in theenvironment.setuptools-based (anddistutils-based) packagescan still be used withpipinstall, since pip will providesetuptools in the build environment it uses for building apackage.

  easy_install,pkg_resources,setuptools anddistutilsare no longer provided by default in environments created withvenv or bootstrapped withensurepip, since they are part ofthesetuptools package. For projects relying on these at runtime,thesetuptools project should be declared as a dependency andinstalled separately (typically, using pip).

  (Contributed by Pradyun Gedam ingh-95299.)

enum¶

• Removeenum’sEnumMeta.__getattr__, which is no longer needed forenum attribute access.(Contributed by Ethan Furman ingh-95083.)

ftplib¶

• Removeftplib’sFTP_TLS.ssl_version class attribute: use thecontext parameter instead.(Contributed by Victor Stinner ingh-94172.)

gzip¶

• Remove thefilename attribute ofgzip’sgzip.GzipFile,deprecated since Python 2.6, use thename attributeinstead. In write mode, thefilename attribute added'.gz' fileextension if it was not present.(Contributed by Victor Stinner ingh-94196.)

hashlib¶

• Remove the pure Python implementation ofhashlib’shashlib.pbkdf2_hmac(), deprecated in Python 3.10. Python 3.10 andnewer requires OpenSSL 1.1.1 (PEP 644): this OpenSSL version providesa C implementation ofpbkdf2_hmac() which is faster.(Contributed by Victor Stinner ingh-94199.)

importlib¶

• Many previously deprecated cleanups inimportlib have now beencompleted:

  • References to, and support formodule_repr() has been removed.(Contributed by Barry Warsaw ingh-97850.)

  • importlib.util.set_package,importlib.util.set_loader andimportlib.util.module_for_loader have all been removed. (Contributed byBrett Cannon and Nikita Sobolev ingh-65961 andgh-97850.)

  • Support forfind_loader() andfind_module() APIs have beenremoved. (Contributed by Barry Warsaw ingh-98040.)

  • importlib.abc.Finder,pkgutil.ImpImporter, andpkgutil.ImpLoaderhave been removed. (Contributed by Barry Warsaw ingh-98040.)

imp¶

• Theimp module has been removed. (Contributed by Barry Warsaw ingh-98040.)

  To migrate, consult the following correspondence table:

  imp	importlib
  imp.NullImporter	InsertNone intosys.path_importer_cache
  imp.cache_from_source()	importlib.util.cache_from_source()
  imp.find_module()	importlib.util.find_spec()
  imp.get_magic()	importlib.util.MAGIC_NUMBER
  imp.get_suffixes()	importlib.machinery.SOURCE_SUFFIXES,importlib.machinery.EXTENSION_SUFFIXES, andimportlib.machinery.BYTECODE_SUFFIXES
  imp.get_tag()	sys.implementation.cache_tag
  imp.load_module()	importlib.import_module()
  imp.new_module(name)	types.ModuleType(name)
  imp.reload()	importlib.reload()
  imp.source_from_cache()	importlib.util.source_from_cache()
  imp.load_source()	See below

  Replaceimp.load_source() with:

  importimportlib.utilimportimportlib.machinerydefload_source(modname,filename):loader=importlib.machinery.SourceFileLoader(modname,filename)spec=importlib.util.spec_from_file_location(modname,filename,loader=loader)module=importlib.util.module_from_spec(spec)# The module is always executed and not cached in sys.modules.# Uncomment the following line to cache the module.# sys.modules[module.__name__] = moduleloader.exec_module(module)returnmodule

• Removeimp functions and attributes with no replacements:

  • Undocumented functions:

    • imp.init_builtin()

    • imp.load_compiled()

    • imp.load_dynamic()

    • imp.load_package()

  • imp.lock_held(),imp.acquire_lock(),imp.release_lock():the locking scheme has changed in Python 3.3 to per-module locks.

  • imp.find_module() constants:SEARCH_ERROR,PY_SOURCE,PY_COMPILED,C_EXTENSION,PY_RESOURCE,PKG_DIRECTORY,C_BUILTIN,PY_FROZEN,PY_CODERESOURCE,IMP_HOOK.

io¶

• Removeio’sio.OpenWrapper and_pyio.OpenWrapper, deprecated in Python3.10: just useopen() instead. Theopen() (io.open())function is a built-in function. Since Python 3.10,_pyio.open() isalso a static method.(Contributed by Victor Stinner ingh-94169.)

locale¶

• Removelocale’slocale.format() function, deprecated in Python 3.7:uselocale.format_string() instead.(Contributed by Victor Stinner ingh-94226.)

smtpd¶

• Thesmtpd module has been removed according to the schedule inPEP 594,having been deprecated in Python 3.4.7 and 3.5.4.Use theaiosmtpd PyPI module or any otherasyncio-based server instead.(Contributed by Oleg Iarygin ingh-93243.)

sqlite3¶

• The following undocumentedsqlite3 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.

  Thesqlite3.OptimizedUnicode text factory has been an alias forstr since Python 3.3. Code that previously set the text factory toOptimizedUnicode can either usestr explicitly, or rely on thedefault value which is alsostr.

  (Contributed by Erlend E. Aasland ingh-92548.)

ssl¶

• Removessl’sssl.RAND_pseudo_bytes() function, deprecated in Python 3.6:useos.urandom() orssl.RAND_bytes() instead.(Contributed by Victor Stinner ingh-94199.)

• Remove thessl.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 ingh-94199.)

• Remove thessl.wrap_socket() function, deprecated in Python 3.7:instead, create assl.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 the server hostname. Code is subject toCWE 295(Improper Certificate Validation).(Contributed by Victor Stinner ingh-94199.)

unittest¶

• Remove many long-deprecatedunittest features:

  • A number ofTestCase 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 usehttps://github.com/isidentical/teyit to automatically moderniseyour unit tests.

  • Undocumented and brokenTestCase methodassertDictContainsSubset (deprecated in Python 3.2).

  • UndocumentedTestLoader.loadTestsFromModule parameteruse_load_tests(deprecated and ignored since Python 3.5).

  • An alias of theTextTestResult class:_TextTestResult (deprecated in Python 3.2).

  (Contributed by Serhiy Storchaka ingh-89325.)

webbrowser¶

• Remove support for obsolete browsers fromwebbrowser.The removed browsers include: Grail, Mosaic, Netscape, Galeon, Skipstone,Iceape, Firebird, and Firefox versions 35 and below (gh-102871).

xml.etree.ElementTree¶

• Remove theElementTree.Element.copy() method of thepure Python implementation, deprecated in Python 3.10, use thecopy.copy() function instead. The C implementation ofxml.etree.ElementTreehas nocopy() method, only a__copy__() method.(Contributed by Victor Stinner ingh-94383.)

zipimport¶

• Removezipimport’sfind_loader() andfind_module() methods,deprecated in Python 3.10: use thefind_spec() method instead. SeePEP 451 for the rationale.(Contributed by Victor Stinner ingh-94379.)

Others¶

• Remove thesuspicious rule from the documentationMakefile andDoc/tools/rstlint.py, both in favor ofsphinx-lint.(Contributed by Julien Palard ingh-98179.)

• Remove thekeyfile andcertfile parameters from theftplib,imaplib,poplib andsmtplib modules,and thekey_file,cert_file andcheck_hostname parameters from thehttp.client module,all deprecated since Python 3.6. Use thecontext parameter(ssl_context inimaplib) instead.(Contributed by Victor Stinner ingh-94172.)

• RemoveJython compatibility hacks from several stdlib modules and tests.(Contributed by Nikita Sobolev ingh-99482.)

• Remove_use_broken_old_ctypes_structure_semantics_ flagfromctypes module.(Contributed by Nikita Sobolev ingh-99285.)

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 ingh-91760.)

• Removerandrange() functionality deprecated since Python 3.10. Formerly,randrange(10.0) losslessly converted torandrange(10). Now, it raises aTypeError. Also, the exception raised for non-integer values such asrandrange(10.5) orrandrange('10') has been changed fromValueError toTypeError. This also prevents bugs whererandrange(1e25) would silentlyselect from a larger range thanrandrange(10**25).(Originally suggested by Serhiy Storchakagh-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))tofilesystem encoding and error handler.Argument files should be encoded in UTF-8 instead of ANSI Codepage on Windows.

• Remove theasyncore-basedsmtpd module deprecated in Python 3.4.7and 3.5.4. A recommended replacement is theasyncio-basedaiosmtpd PyPI module.

• shlex.split(): PassingNone fors argument now raises anexception, rather than readingsys.stdin. The feature was deprecatedin Python 3.9.(Contributed by Victor Stinner ingh-94352.)

• Theos module no longer accepts bytes-like paths, likebytearray andmemoryview types: only the exactbytes type is accepted for bytes strings.(Contributed by Victor Stinner ingh-98393.)

• syslog.openlog() andsyslog.closelog() now fail if used in subinterpreters.syslog.syslog() may still be used in subinterpreters,but now only ifsyslog.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 Donghee Na ingh-99127.)

• The undocumented locking behavior ofcached_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 ingh-103176.)

• When extracting tar files usingtarfile orshutil.unpack_archive(), pass thefilter argument to limit featuresthat may be surprising or dangerous.SeeExtraction filters for details.

• The output of thetokenize.tokenize() andtokenize.generate_tokens()functions is now changed due to the changes introduced inPEP 701. Thismeans thatSTRING tokens are not emitted any more for f-strings and thetokens described inPEP 701 are now produced instead:FSTRING_START,FSTRING_MIDDLE andFSTRING_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-stringf"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 consequence of thechanges required to supportPEP 701. Some of these changes include:

  • Thetype attribute of the tokens emitted when tokenizing some invalid Pythoncharacters such as! has changed fromERRORTOKEN toOP.

  • Incomplete single-line strings now also raisetokenize.TokenError as incompletemultiline strings do.

  • Some incomplete or invalid Python code now raisestokenize.TokenError instead ofreturning arbitraryERRORTOKEN tokens when tokenizing it.

  • Mixing tabs and spaces as indentation in the same file is not supported anymore and willraise aTabError.

• Thethreading module now expects the_thread module to havean_is_main_interpreter attribute. It is a function with noarguments that returnsTrue if the current interpreter is themain interpreter.

  Any library or application that provides a custom_thread moduleshould provide_is_main_interpreter().(Seegh-112826.)

New Features¶

• PEP 697: Introduce theUnstable 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 thePyUnstable_ prefix in names.

  Code object constructors:

  • PyUnstable_Code_New() (renamed fromPyCode_New)

  • PyUnstable_Code_NewWithPosOnlyArgs() (renamed fromPyCode_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 ingh-101101.)

• PEP 697: Add an 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() andPyType_GetTypeDataSize()added to allow access to subclass-specific instance data.

  • Py_TPFLAGS_ITEMS_AT_END andPyObject_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 ingh-103509.)

• Add the newlimited C API functionPyType_FromMetaclass(),which generalizes the existingPyType_FromModuleAndSpec() usingan additional metaclass argument.(Contributed by Wenzel Jakob ingh-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

  ThePy_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 overridetp_call nowinherit thePy_TPFLAGS_HAVE_VECTORCALL flag.(Contributed by Petr Viktorin ingh-93274.)

  ThePy_TPFLAGS_MANAGED_DICT andPy_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 theLimited API. (Contributedby Wenzel Jakob ingh-98586.)

• Add 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 ingh-93503.)

• Add new functionPyFunction_SetVectorcall() to the C APIwhich sets the vectorcall field of a givenPyFunctionObject.(Contributed by Andrew Frost ingh-92257.)

• The C API now permits registering callbacks viaPyDict_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 ingh-91052.)

• AddPyType_AddWatcher() andPyType_Watch() API to registercallbacks to receive notification on changes to a type.(Contributed by Carl Meyer ingh-91051.)

• AddPyCode_AddWatcher() andPyCode_ClearWatcher()APIs to register callbacks to receive notification on creation anddestruction of code objects.(Contributed by Itamar Oren ingh-91054.)

• AddPyFrame_GetVar() andPyFrame_GetVarString() functions toget a frame variable by its name.(Contributed by Victor Stinner ingh-91248.)

• AddPyErr_GetRaisedException() andPyErr_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() andPyErr_Restore().This is less error prone and a bit more efficient.(Contributed by Mark Shannon ingh-101578.)

• Add_PyErr_ChainExceptions1, which takes an exception instance,to replace the legacy-API_PyErr_ChainExceptions, which is nowdeprecated. (Contributed by Mark Shannon ingh-101578.)

• AddPyException_GetArgs() andPyException_SetArgs()as convenience functions for retrieving and modifyingtheargs passed to the exception’s constructor.(Contributed by Mark Shannon ingh-101578.)

• AddPyErr_DisplayException(), which takes an exception instance,to replace the legacy-apiPyErr_Display(). (Contributed byIrit Katriel ingh-102755).

• PEP 683: IntroduceImmortal Objects, which allows objectsto bypass reference counts, and related changes to the C-API:

  • _Py_IMMORTAL_REFCNT: The reference count that defines an object

    as 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 withPy_BUILD_CORE.

  • SSTATE_INTERNED_IMMORTAL An identifier for interned unicode objects

    that are immortal.

  • SSTATE_INTERNED_IMMORTAL_STATIC An identifier for interned unicode

    objects that are immortal and static

  • sys.getunicodeinternedsize This returns the total number of unicode

    objects that have been interned. This is now needed forrefleak.py tocorrectly track reference counts and allocated blocks

  (Contributed by Eddie Elizondo ingh-84436.)

• PEP 684: Add the newPy_NewInterpreterFromConfig()function andPyInterpreterConfig, which may be usedto create sub-interpreters with their own GILs.(SeePEP 684: A Per-Interpreter GIL for more info.)(Contributed by Eric Snow ingh-104110.)

• In the limited C API version 3.12,Py_INCREF() andPy_DECREF() functions are now implemented as opaque function calls tohide implementation details.(Contributed by Victor Stinner ingh-105387.)

Porting to Python 3.12¶

• Legacy Unicode APIs based onPy_UNICODE* representation has been removed.Please migrate to APIs based on UTF-8 orwchar_t*.

• Argument parsing functions likePyArg_ParseTuple() doesn’t supportPy_UNICODE* based format (e.g.u,Z) anymore. Please migrateto other formats for Unicode likes,z,es, andU.

• tp_weaklist for all static builtin types is alwaysNULL.This is an internal-only field onPyTypeObjectbut 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-onlyPyTypeObject.tp_subclasses may now not bea valid object pointer. Its type was changed tovoid* 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__() (usingPyObject_CallMethod(),for example).

• Add support of more formatting options (left aligning, octals, uppercasehexadecimals,intmax_t,ptrdiff_t,wchar_t Cstrings, variable width and precision) inPyUnicode_FromFormat() andPyUnicode_FromFormatV().(Contributed by Serhiy Storchaka ingh-98836.)

• An unrecognized format character inPyUnicode_FromFormat() andPyUnicode_FromFormatV() now sets aSystemError.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 ingh-95781.)

• Fix wrong sign placement inPyUnicode_FromFormat() andPyUnicode_FromFormatV().(Contributed by Philip Georgi ingh-95504.)

• Extension classes wanting to add a__dict__ or weak reference slotshould usePy_TPFLAGS_MANAGED_DICT andPy_TPFLAGS_MANAGED_WEAKREF instead oftp_dictoffset andtp_weaklistoffset, respectively.The use oftp_dictoffset andtp_weaklistoffset is stillsupported, but does not fully support multiple inheritance(gh-95589), and performance may be worse.Classes declaringPy_TPFLAGS_MANAGED_DICT must call_PyObject_VisitManagedDict() and_PyObject_ClearManagedDict()to traverse and clear their instance’s dictionaries.To clear weakrefs, callPyObject_ClearWeakRefs(), as before.

• ThePyUnicode_FSDecoder() function no longer accepts bytes-likepaths, likebytearray andmemoryview types: only the exactbytes type is accepted for bytes strings.(Contributed by Victor Stinner ingh-98393.)

• ThePy_CLEAR,Py_SETREF andPy_XSETREFmacros now only evaluate their arguments once. If an argument has sideeffects, these side effects are no longer duplicated.(Contributed by Victor Stinner ingh-98724.)

• The interpreter’s error indicator is now always normalized. This meansthatPyErr_SetObject(),PyErr_SetString() and the otherfunctions that set the error indicator now normalize the exceptionbefore storing it. (Contributed by Mark Shannon ingh-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 overridestp_newis deprecated, and in Python 3.14+ it will be disallowed.Note that these functions ignoretp_new of the metaclass, possiblyallowing incomplete initialization.

  Note thatPyType_FromMetaclass() (added in Python 3.12)already disallows creating classes whose metaclass overridestp_new(__new__() in Python).

  Sincetp_new overrides almost everythingPyType_From* functions do,the two are incompatible with each other.The existing behavior – ignoring the metaclass for several stepsof type creation – is unsafe in general, since (meta)classes assume thattp_new was called.There is no simple general workaround. One of the following may work for you:

  • If you control the metaclass, avoid usingtp_new in it:

    • If initialization can be skipped, it can be done intp_init instead.

    • If the metaclass doesn’t need to be instantiated from Python,set itstp_new toNULL usingthePy_TPFLAGS_DISALLOW_INSTANTIATION flag.This makes it acceptable forPyType_From* functions.

  • AvoidPyType_From* functions: if you don’t need C-specific features(slots or setting the instance size), create types bycallingthe metaclass.

  • If youknow thetp_new can be skipped safely, filter the deprecationwarning out usingwarnings.catch_warnings() from Python.

• PyOS_InputHook andPyOS_ReadlineFunctionPointer are nolonger called insubinterpreters. 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.

• PyLongObject has had its internals changed for better performance.Although the internals ofPyLongObject are private, they are usedby some extension modules.The internal fields should no longer be accessed directly, instead the APIfunctions beginningPyLong_... should be used instead.Two newunstable API functions are provided for efficient access to thevalue ofPyLongObjects which fit into a single machine word:

  • PyUnstable_Long_IsCompact()

  • PyUnstable_Long_CompactValue()

• Custom allocators, set viaPyMem_SetAllocator(), are nowrequired to be thread-safe, regardless of memory domain. Allocatorsthat don’t have their own state, including “hooks”, are not affected.If your custom allocator is not already thread-safe and you needguidance then please create a new GitHub issueand CC@ericsnowcurrently.

Deprecated¶

• In accordance withPEP 699, thema_version_tag field inPyDictObjectis 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 ingh-101193. PEP by Ken Jin.)

• Deprecate global configuration variable:

  • Py_DebugFlag: usePyConfig.parser_debug

  • Py_VerboseFlag: usePyConfig.verbose

  • Py_QuietFlag: usePyConfig.quiet

  • Py_InteractiveFlag: usePyConfig.interactive

  • Py_InspectFlag: usePyConfig.inspect

  • Py_OptimizeFlag: usePyConfig.optimization_level

  • Py_NoSiteFlag: usePyConfig.site_import

  • Py_BytesWarningFlag: usePyConfig.bytes_warning

  • Py_FrozenFlag: usePyConfig.pathconfig_warnings

  • Py_IgnoreEnvironmentFlag: usePyConfig.use_environment

  • Py_DontWriteBytecodeFlag: usePyConfig.write_bytecode

  • Py_NoUserSiteDirectory: usePyConfig.user_site_directory

  • Py_UnbufferedStdioFlag: usePyConfig.buffered_stdio

  • Py_HashRandomizationFlag: usePyConfig.use_hash_seedandPyConfig.hash_seed

  • Py_IsolatedFlag: usePyConfig.isolated

  • Py_LegacyWindowsFSEncodingFlag: usePyPreConfig.legacy_windows_fs_encoding

  • Py_LegacyWindowsStdioFlag: usePyConfig.legacy_windows_stdio

  • Py_FileSystemDefaultEncoding: usePyConfig.filesystem_encoding

  • Py_HasFileSystemDefaultEncoding: usePyConfig.filesystem_encoding

  • Py_FileSystemDefaultEncodeErrors: usePyConfig.filesystem_errors

  • Py_UTF8Mode: usePyPreConfig.utf8_mode (seePy_PreInitialize())

  ThePy_InitializeFromConfig() API should be used withPyConfig instead.(Contributed by Victor Stinner ingh-77782.)

• Creatingimmutabletypes with mutablebases is deprecated and will be disabled in Python 3.14. (gh-95388)

• Thestructmember.h header is deprecated, though it continues to beavailable and there are no plans to remove it.

  Its contents are now available just by includingPython.h,with aPy prefix added if it was missing:

  • PyMemberDef,PyMember_GetOne() andPyMember_SetOne()

  • Type macros likePy_T_INT,Py_T_DOUBLE, etc.(previouslyT_INT,T_DOUBLE, etc.)

  • The flagsPy_READONLY (previouslyREADONLY) andPy_AUDIT_READ (previously all uppercase)

  Several items are not exposed fromPython.h:

  • T_OBJECT (usePy_T_OBJECT_EX)

  • T_NONE (previously undocumented, and pretty quirky)

  • The macroWRITE_RESTRICTED which does nothing.

  • The macrosRESTRICTED andREAD_RESTRICTED, equivalents ofPy_AUDIT_READ.

  • In some configurations,<stddef.h> is not included fromPython.h.It should be included manually when usingoffsetof().

  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 ingh-47146 by Petr Viktorin, based onearlier work by Alexander Belopolsky and Matthias Braun.)

• PyErr_Fetch() andPyErr_Restore() are deprecated.UsePyErr_GetRaisedException() andPyErr_SetRaisedException() instead.(Contributed by Mark Shannon ingh-101578.)

• PyErr_Display() is deprecated. UsePyErr_DisplayException()instead. (Contributed by Irit Katriel ingh-102755).

• _PyErr_ChainExceptions is deprecated. Use_PyErr_ChainExceptions1instead. (Contributed by Irit Katriel ingh-102192.)

• UsingPyType_FromSpec(),PyType_FromSpecWithBases()orPyType_FromModuleAndSpec() to create a class whose metaclassoverridestp_new is deprecated.Call the metaclass instead.

Removed¶

• Remove thetoken.h header file. There was never any public tokenizer CAPI. Thetoken.h header file was only designed to be used by Pythoninternals.(Contributed by Victor Stinner ingh-92651.)

• Legacy Unicode APIs have been removed. SeePEP 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 thePyUnicode_InternImmortal() function macro.(Contributed by Victor Stinner ingh-85858.)