PEP 657: Fine-grained error locations in tracebacks¶

When printing tracebacks, the interpreter will now point to the exact expressionthat caused the error, instead of just the line. For example:

Traceback(mostrecentcalllast):File"distance.py",line11,in<module>print(manhattan_distance(p1,p2))^^^^^^^^^^^^^^^^^^^^^^^^^^File"distance.py",line6,inmanhattan_distancereturnabs(point_1.x-point_2.x)+abs(point_1.y-point_2.y)^^^^^^^^^AttributeError:'NoneType'objecthasnoattribute'x'

Previous versions of the interpreter would point to just the line, making itambiguous which object wasNone. These enhanced errors can also be helpfulwhen dealing with deeply nesteddict objects and multiple function calls:

Traceback(mostrecentcalllast):File"query.py",line37,in<module>magic_arithmetic('foo')File"query.py",line18,inmagic_arithmeticreturnadd_counts(x)/25^^^^^^^^^^^^^File"query.py",line24,inadd_countsreturn25+query_user(user1)+query_user(user2)^^^^^^^^^^^^^^^^^File"query.py",line32,inquery_userreturn1+query_count(db,response['a']['b']['c']['user'],retry=True)~~~~~~~~~~~~~~~~~~^^^^^TypeError:'NoneType'objectisnotsubscriptable

As well as complex arithmetic expressions:

Traceback(mostrecentcalllast):File"calculation.py",line54,in<module>result=(x/y/z)*(a/b/c)~~~~~~^~~ZeroDivisionError:divisionbyzero

Additionally, the information used by the enhanced traceback featureis made available via a general API, that can be used to correlatebytecodeinstructions with source code location.This information can be retrieved using:

• Thecodeobject.co_positions() method in Python.

• ThePyCode_Addr2Location() function in the C API.

SeePEP 657 for more details. (Contributed by Pablo Galindo, Batuhan Taskayaand Ammar Askar inbpo-43950.)

PEP 654: Exception Groups andexcept*¶

PEP 654 introduces language features that enable a programto raise and handle multiple unrelated exceptions simultaneously.The builtin typesExceptionGroup andBaseExceptionGroupmake it possible to group exceptions and raise them together,and the newexcept* syntax generalizesexcept to match subgroups of exception groups.

SeePEP 654 for more details.

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

PEP 678: Exceptions can be enriched with notes¶

Theadd_note() method is added toBaseException.It can be used to enrich exceptions with context informationthat is not available at the time when the exception is raised.The added notes appear in the default traceback.

SeePEP 678 for more details.

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

Windowspy.exe launcher improvements¶

The copy of thePython Launcher for Windows included with Python 3.11 has been significantlyupdated. It now supports company/tag syntax as defined inPEP 514 using the-V:<company>/<tag> argument instead of the limited-<major>.<minor>.This allows launching distributions other thanPythonCore,the one hosted onpython.org.

When using-V: selectors, either company or tag can be omitted, but allinstalls will be searched. For example,-V:OtherPython/ will select the“best” tag registered forOtherPython, while-V:3.11 or-V:/3.11will select the “best” distribution with tag3.11.

When using the legacy-<major>,-<major>.<minor>,-<major>-<bitness> or-<major>.<minor>-<bitness> arguments,all existing behaviour should be preserved from past versions,and only releases fromPythonCore will be selected.However, the-64 suffix now implies “not 32-bit” (not necessarily x86-64),as there are multiple supported 64-bit platforms.32-bit runtimes are detected by checking the runtime’s tag for a-32 suffix.All releases of Python since 3.5 have included this in their 32-bit builds.

PEP 646: Variadic generics¶

PEP 484 previously introducedTypeVar, enabling creationof generics parameterised with a single type.PEP 646 addsTypeVarTuple, enabling parameterisationwith anarbitrary number of types. In other words,aTypeVarTuple is avariadic type variable,enablingvariadic generics.

This enables a wide variety of use cases.In particular, it allows the type of array-like structuresin numerical computing libraries such as NumPy and TensorFlow to beparameterised with the arrayshape. Static type checkers will nowbe able to catch shape-related bugs in code that uses these libraries.

SeePEP 646 for more details.

(Contributed by Matthew Rahtz inbpo-43224, with contributions bySerhiy Storchaka and Jelle Zijlstra. PEP written by Mark Mendoza, MatthewRahtz, Pradeep Kumar Srinivasan, and Vincent Siles.)

PEP 655: Marking individualTypedDict items as required or not-required¶

Required andNotRequired provide astraightforward way to mark whether individual items in aTypedDict must be present. Previously, this was only possibleusing inheritance.

All fields are still required by default,unless thetotal parameter is set toFalse,in which case all fields are still not-required by default.For example, the following specifies aTypedDictwith one required and one not-required key:

classMovie(TypedDict):title:stryear:NotRequired[int]m1:Movie={"title":"Black Panther","year":2018}# OKm2:Movie={"title":"Star Wars"}# OK (year is not required)m3:Movie={"year":2022}# ERROR (missing required field title)

The following definition is equivalent:

classMovie(TypedDict,total=False):title:Required[str]year:int

SeePEP 655 for more details.

(Contributed by David Foster and Jelle Zijlstra inbpo-47087. PEPwritten by David Foster.)

PEP 673:Self type¶

The newSelf annotation provides a simple and intuitiveway to annotate methods that return an instance of their class. Thisbehaves the same as theTypeVar-based approachspecified in PEP 484,but is more concise and easier to follow.

Common use cases include alternative constructors provided asclassmethods,and__enter__() methods that returnself:

classMyLock:def__enter__(self)->Self:self.lock()returnself...classMyInt:@classmethoddeffromhex(cls,s:str)->Self:returncls(int(s,16))...

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

SeePEP 673 for more details.

(Contributed by James Hilton-Balfe inbpo-46534. PEP written byPradeep Kumar Srinivasan and James Hilton-Balfe.)

PEP 675: Arbitrary literal string type¶

The newLiteralString annotation may be used to indicatethat a function parameter can be of any literal string type. This allowsa function to accept arbitrary literal string types, as well as stringscreated from other literal strings. Type checkers can thenenforce that sensitive functions, such as those that execute SQLstatements or shell commands, are called only with static arguments,providing protection against injection attacks.

For example, a SQL query function could be annotated as follows:

defrun_query(sql:LiteralString)->......defcaller(arbitrary_string:str,query_string:LiteralString,table_name:LiteralString,)->None:run_query("SELECT * FROM students")# okrun_query(query_string)# okrun_query("SELECT * FROM "+table_name)# okrun_query(arbitrary_string)# type checker errorrun_query(# type checker errorf"SELECT * FROM students WHERE name ={arbitrary_string}")

SeePEP 675 for more details.

(Contributed by Jelle Zijlstra inbpo-47088. PEP written by PradeepKumar Srinivasan and Graham Bleaney.)

PEP 681: Data class transforms¶

dataclass_transform may be used todecorate a class, metaclass, or a function that is itself a decorator.The presence of@dataclass_transform() tells a static type checker that thedecorated object performs runtime “magic” that transforms a class,giving itdataclass-like behaviors.

For example:

# The create_model decorator is defined by a library.@typing.dataclass_transform()defcreate_model(cls:Type[T])->Type[T]:cls.__init__=...cls.__eq__=...cls.__ne__=...returncls# The create_model decorator can now be used to create new model classes:@create_modelclassCustomerModel:id:intname:strc=CustomerModel(id=327,name="Eric Idle")

SeePEP 681 for more details.

(Contributed by Jelle Zijlstra ingh-91860. PEP written byErik De Bonte and Eric Traut.)

PEP 563 may not be the future¶

PEP 563 Postponed Evaluation of Annotations(thefrom__future__importannotationsfuture statement)that was originally planned for release in Python 3.10has been put on hold indefinitely.Seethis message from the Steering Councilfor more information.

asyncio¶

• Added theTaskGroup class,anasynchronous context managerholding a group of tasks that will wait for all of them upon exit.For new code this is recommended over usingcreate_task() andgather() directly.(Contributed by Yury Selivanov and others ingh-90908.)

• Addedtimeout(), an asynchronous context manager forsetting a timeout on asynchronous operations. For new code this isrecommended over usingwait_for() directly.(Contributed by Andrew Svetlov ingh-90927.)

• Added theRunner class, which exposes the machineryused byrun().(Contributed by Andrew Svetlov ingh-91218.)

• Added theBarrier class to the synchronizationprimitives in the asyncio library, and the relatedBrokenBarrierError exception.(Contributed by Yves Duprat and Andrew Svetlov ingh-87518.)

• Added keyword argumentall_errors toasyncio.loop.create_connection()so that multiple connection errors can be raised as anExceptionGroup.

• Added theasyncio.StreamWriter.start_tls() method forupgrading existing stream-based connections to TLS.(Contributed by Ian Good inbpo-34975.)

• Added raw datagram socket functions to the event loop:sock_sendto(),sock_recvfrom() andsock_recvfrom_into().These have implementations inSelectorEventLoop andProactorEventLoop.(Contributed by Alex Grönholm inbpo-46805.)

• Addedcancelling() anduncancel() methods toTask.These are primarily intended for internal use,notably byTaskGroup.

contextlib¶

• Added non parallel-safechdir() context manager to changethe current working directory and then restore it on exit. Simple wrapperaroundchdir(). (Contributed by Filipe Laíns inbpo-25625)

dataclasses¶

• Change field default mutability check, allowing only defaults which arehashable instead of any object which is not an instance ofdict,list orset. (Contributed by Eric V. Smith inbpo-44674.)

datetime¶

• Adddatetime.UTC, a convenience alias fordatetime.timezone.utc. (Contributed by Kabir Kwatra ingh-91973.)

• datetime.date.fromisoformat(),datetime.time.fromisoformat() anddatetime.datetime.fromisoformat() can now be used to parse most ISO 8601formats (barring only those that support fractional hours and minutes).(Contributed by Paul Ganssle ingh-80010.)

enum¶

• RenamedEnumMeta toEnumType(EnumMeta kept as an alias).

• AddedStrEnum,with members that can be used as (and must be) strings.

• AddedReprEnum,which only modifies the__repr__() of memberswhile returning their literal values (rather than names)for__str__() and__format__()(used bystr(),format() andf-strings).

• ChangedEnum.__format__() (the default forformat(),str.format() andf-strings) to always producethe same result asEnum.__str__(): for enums inheriting fromReprEnum it will be the member’s value; for all other enumsit will be the enum and member name (e.g.Color.RED).

• Added a newboundary class parameter toFlag enumsand theFlagBoundary enum with its options,to control how to handle out-of-range flag values.

• Added theverify() enum decoratorand theEnumCheck enum with its options,to check enum classes against several specific constraints.

• Added themember() andnonmember() decorators,to ensure the decorated object is/is not converted to an enum member.

• Added theproperty() decorator,which works likeproperty() except for enums.Use this instead oftypes.DynamicClassAttribute().

• Added theglobal_enum() enum decorator,which adjusts__repr__() and__str__()to show values as members of their module rather than the enum class.For example,'re.ASCII' for theASCII memberofre.RegexFlag rather than'RegexFlag.ASCII'.

• EnhancedFlag to supportlen(), iteration andin/notin on its members.For example, the following now works:len(AFlag(3))==2andlist(AFlag(3))==(AFlag.ONE,AFlag.TWO)

• ChangedEnum andFlagso that members are now definedbefore__init_subclass__() is called;dir() now includes methods, etc., from mixed-in data types.

• ChangedFlagto only consider primary values (power of two) canonicalwhile composite values (3,6,10, etc.) are considered aliases;inverted flags are coerced to their positive equivalent.

fcntl¶

• On FreeBSD, theF_DUP2FD andF_DUP2FD_CLOEXEC flags respectivelyare supported, the former equals todup2 usage while the latter settheFD_CLOEXEC flag in addition.

fractions¶

• SupportPEP 515-style initialization ofFraction fromstring. (Contributed by Sergey B Kirpichev inbpo-44258.)

• Fraction now implements an__int__ method, sothat anisinstance(some_fraction,typing.SupportsInt) check passes.(Contributed by Mark Dickinson inbpo-44547.)

functools¶

• functools.singledispatch() now supportstypes.UnionTypeandtyping.Union as annotations to the dispatch argument.:

  >>>fromfunctoolsimportsingledispatch>>>@singledispatch...deffun(arg,verbose=False):...ifverbose:...print("Let me just say,",end=" ")...print(arg)...>>>@fun.register...def_(arg:int|float,verbose=False):...ifverbose:...print("Strength in numbers, eh?",end=" ")...print(arg)...>>>fromtypingimportUnion>>>@fun.register...def_(arg:Union[list,set],verbose=False):...ifverbose:...print("Enumerate this:")...fori,eleminenumerate(arg):...print(i,elem)...

  (Contributed by Yurii Karabas inbpo-46014.)

gzip¶

• Thegzip.compress() function is now faster when used with themtime=0 argument as it delegates the compression entirely to a singlezlib.compress() operation. There is one side effect of this change: Thegzip file header contains an “OS” byte in its header. That was traditionallyalways set to a value of 255 representing “unknown” by thegzipmodule. Now, when usingcompress() withmtime=0, it may beset to a different value by the underlying zlib C library Python was linkedagainst.(Seegh-112346 for details on the side effect.)

hashlib¶

• hashlib.blake2b() andhashlib.blake2s() now preferlibb2over Python’s vendored copy.(Contributed by Christian Heimes inbpo-47095.)

• The internal_sha3 module with SHA3 and SHAKE algorithms now usestiny_sha3 instead of theKeccak Code Package to reduce code and binarysize. Thehashlib module prefers optimized SHA3 and SHAKEimplementations from OpenSSL. The change affects only installations withoutOpenSSL support.(Contributed by Christian Heimes inbpo-47098.)

• Addhashlib.file_digest(), a helper function for efficient hashingof files or file-like objects.(Contributed by Christian Heimes ingh-89313.)

IDLE and idlelib¶

• Apply syntax highlighting to.pyi files. (Contributed by AlexWaygood and Terry Jan Reedy inbpo-45447.)

• Include prompts when saving Shell with inputs and outputs.(Contributed by Terry Jan Reedy ingh-95191.)

inspect¶

• Addgetmembers_static() to return all members withouttriggering dynamic lookup via the descriptor protocol. (Contributed byWeipeng Hong inbpo-30533.)

• Addismethodwrapper()for checking if the type of an object is aMethodWrapperType.(Contributed by Hakan Çelik inbpo-29418.)

• Change the frame-related functions in theinspect module to return newFrameInfo andTraceback class instances(backwards compatible with the previousnamed tuple-like interfaces)that includes the extendedPEP 657 position information (endline number, column and end column). The affected functions are:

  • inspect.getframeinfo()

  • inspect.getouterframes()

  • inspect.getinnerframes(),

  • inspect.stack()

  • inspect.trace()

  (Contributed by Pablo Galindo ingh-88116.)

locale¶

• Addlocale.getencoding() to get the current locale encoding. It is similar tolocale.getpreferredencoding(False) but ignores thePython UTF-8 Mode.

logging¶

• AddedgetLevelNamesMapping()to return a mapping from logging level names (e.g.'CRITICAL')to the values of their correspondingLogging Levels (e.g.50, by default).(Contributed by Andrei Kulakovin ingh-88024.)

• Added acreateSocket() methodtoSysLogHandler, to matchSocketHandler.createSocket().It is called automatically during handler initializationand when emitting an event, if there is no active socket.(Contributed by Kirill Pinchuk ingh-88457.)

math¶

• Addmath.exp2(): return 2 raised to the power of x.(Contributed by Gideon Mitchell inbpo-45917.)

• Addmath.cbrt(): return the cube root of x.(Contributed by Ajith Ramachandran inbpo-44357.)

• The behaviour of twomath.pow() corner cases was changed, forconsistency with the IEEE 754 specification. The operationsmath.pow(0.0,-math.inf) andmath.pow(-0.0,-math.inf) now returninf. Previously they raisedValueError. (Contributed by MarkDickinson inbpo-44339.)

• Themath.nan value is now always available.(Contributed by Victor Stinner inbpo-46917.)

operator¶

• A new functionoperator.call has been added, such thatoperator.call(obj,*args,**kwargs)==obj(*args,**kwargs).(Contributed by Antony Lee inbpo-44019.)

os¶

• On Windows,os.urandom() now usesBCryptGenRandom(),instead ofCryptGenRandom() which is deprecated.(Contributed by Donghee Na inbpo-44611.)

• As of 3.11.10,os.mkdir() andos.makedirs() on Windowsnow support passing amode value of0o700 to apply accesscontrol to the new directory. This implicitly affectstempfile.mkdtemp() and is a mitigation for CVE-2024-4030.Other values formode continue to be ignored.(Contributed by Steve Dower ingh-118486.)

pathlib¶

• glob() andrglob() return onlydirectories ifpattern ends with a pathname components separator:sep oraltsep.(Contributed by Eisuke Kawasima inbpo-22276 andbpo-33392.)

re¶

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

shutil¶

• Add optional parameterdir_fd inshutil.rmtree().(Contributed by Serhiy Storchaka inbpo-46245.)

socket¶

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

• create_connection() has an option to raise, in case offailure to connect, anExceptionGroup containing all errorsinstead of only raising the last error.(Contributed by Irit Katriel inbpo-29980.)

sqlite3¶

• You can now disable the authorizer by passingNone toset_authorizer().(Contributed by Erlend E. Aasland inbpo-44491.)

• Collation namecreate_collation() can nowcontain any Unicode character. Collation names with invalid charactersnow raiseUnicodeEncodeError instead ofsqlite3.ProgrammingError.(Contributed by Erlend E. Aasland inbpo-44688.)

• sqlite3 exceptions now include the SQLite extended error code assqlite_errorcode and the SQLite error name assqlite_errorname.(Contributed by Aviv Palivoda, Daniel Shahaf, and Erlend E. Aasland inbpo-16379 andbpo-24139.)

• Addsetlimit() andgetlimit() tosqlite3.Connection forsetting and getting SQLite limits by connection basis.(Contributed by Erlend E. Aasland inbpo-45243.)

• sqlite3 now setssqlite3.threadsafety based on the defaultthreading mode the underlying SQLite library has been compiled with.(Contributed by Erlend E. Aasland inbpo-45613.)

• sqlite3 C callbacks now use unraisable exceptions if callbacktracebacks are enabled. Users can now register anunraisablehookhandler to improve their debugexperience.(Contributed by Erlend E. Aasland inbpo-45828.)

• Fetch across rollback no longer raisesInterfaceError.Instead we leave it to the SQLite library to handle these cases.(Contributed by Erlend E. Aasland inbpo-44092.)

• Addserialize() anddeserialize() tosqlite3.Connection forserializing and deserializing databases.(Contributed by Erlend E. Aasland inbpo-41930.)

• Addcreate_window_function() tosqlite3.Connection for creating aggregate window functions.(Contributed by Erlend E. Aasland inbpo-34916.)

• Addblobopen() tosqlite3.Connection.sqlite3.Blob allows incremental I/O operations on blobs.(Contributed by Aviv Palivoda and Erlend E. Aasland inbpo-24905.)

string¶

• Addget_identifiers()andis_valid() tostring.Template,which respectively return all valid placeholders,and whether any invalid placeholders are present.(Contributed by Ben Kehoe ingh-90465.)

sys¶

• sys.exc_info() now derives thetype andtraceback fieldsfrom thevalue (the exception instance), so when an exception ismodified while it is being handled, the changes are reflected inthe results of subsequent calls toexc_info().(Contributed by Irit Katriel inbpo-45711.)

• Addsys.exception() which returns the active exception instance(equivalent tosys.exc_info()[1]).(Contributed by Irit Katriel inbpo-46328.)

• Add thesys.flags.safe_path flag.(Contributed by Victor Stinner ingh-57684.)

sysconfig¶

• Three newinstallation schemes(posix_venv,nt_venv andvenv) were added and are used when Pythoncreates new virtual environments or when it is running from a virtualenvironment.The first two schemes (posix_venv andnt_venv) are OS-specificfor non-Windows and Windows, thevenv is essentially an alias to one ofthem according to the OS Python runs on.This is useful for downstream distributors who modifysysconfig.get_preferred_scheme().Third party code that creates new virtual environments should use the newvenv installation scheme to determine the paths, as doesvenv.(Contributed by Miro Hrončok inbpo-45413.)

tempfile¶

• SpooledTemporaryFile objects now fully implement the methodsofio.BufferedIOBase orio.TextIOBase(depending on file mode).This lets them work correctly with APIs that expect file-like objects,such as compression modules.(Contributed by Carey Metcalfe ingh-70363.)

• As of 3.11.10 on Windows, the default mode0o700 used bytempfile.mkdtemp() now limits access to the new directory due tochanges toos.mkdir(). This is a mitigation for CVE-2024-4030.(Contributed by Steve Dower ingh-118486.)

threading¶

• On Unix, if thesem_clockwait() function is available in the C library(glibc 2.30 and newer), thethreading.Lock.acquire() method now usesthe monotonic clock (time.CLOCK_MONOTONIC) for the timeout, ratherthan using the system clock (time.CLOCK_REALTIME), to not be affectedby system clock changes.(Contributed by Victor Stinner inbpo-41710.)

time¶

• On Unix,time.sleep() now uses theclock_nanosleep() ornanosleep() function, if available, which has a resolution of 1 nanosecond(10^-9 seconds), rather than usingselect() which has a resolutionof 1 microsecond (10^-6 seconds).(Contributed by Benjamin Szőke and Victor Stinner inbpo-21302.)

• On Windows 8.1 and newer,time.sleep() now uses a waitable timer basedonhigh-resolution timerswhich has a resolution of 100 nanoseconds (10^-7 seconds). Previously,it had a resolution of 1 millisecond (10^-3 seconds).(Contributed by Benjamin Szőke, Donghee Na, Eryk Sun and Victor Stinner inbpo-21302 andbpo-45429.)

tkinter¶

• Added methodinfo_patchlevel() which returns the exact version ofthe Tcl library as a named tuple similar tosys.version_info.(Contributed by Serhiy Storchaka ingh-91827.)

traceback¶

• Addtraceback.StackSummary.format_frame_summary() to allow usersto override which frames appear in the traceback, and how they areformatted.(Contributed by Ammar Askar inbpo-44569.)

• Addtraceback.TracebackException.print(), which prints theformattedTracebackException instance to a file.(Contributed by Irit Katriel inbpo-33809.)

typing¶

For major changes, seeNew Features Related to Type Hints.

• Addtyping.assert_never() andtyping.Never.typing.assert_never() is useful for asking a type checker to confirmthat a line of code is not reachable. At runtime, it raises anAssertionError.(Contributed by Jelle Zijlstra ingh-90633.)

• Addtyping.reveal_type(). This is useful for asking a type checkerwhat type it has inferred for a given expression. At runtime it printsthe type of the received value.(Contributed by Jelle Zijlstra ingh-90572.)

• Addtyping.assert_type(). This is useful for asking a type checkerto confirm that the type it has inferred for a given expression matchesthe given type. At runtime it simply returns the received value.(Contributed by Jelle Zijlstra ingh-90638.)

• typing.TypedDict types can now be generic. (Contributed bySamodya Abeysiriwardane ingh-89026.)

• NamedTuple types can now be generic.(Contributed by Serhiy Storchaka inbpo-43923.)

• Allow subclassing oftyping.Any. This is useful for avoidingtype checker errors related to highly dynamic class, such as mocks.(Contributed by Shantanu Jain ingh-91154.)

• Thetyping.final() decorator now sets the__final__ attributed onthe decorated object.(Contributed by Jelle Zijlstra ingh-90500.)

• Thetyping.get_overloads() function can be used for introspectingthe overloads of a function.typing.clear_overloads() can be usedto clear all registered overloads of a function.(Contributed by Jelle Zijlstra ingh-89263.)

• The__init__() method ofProtocol subclassesis now preserved. (Contributed by Adrian Garcia Badarasco ingh-88970.)

• The representation of empty tuple types (Tuple[()]) is simplified.This affects introspection, e.g.get_args(Tuple[()]) now evaluatesto() instead of((),).(Contributed by Serhiy Storchaka ingh-91137.)

• Loosen runtime requirements for type annotations by removing the callablecheck in the privatetyping._type_check function. (Contributed byGregory Beauregard ingh-90802.)

• typing.get_type_hints() now supports evaluating strings as forwardreferences inPEP 585 generic aliases.(Contributed by Niklas Rosenstein ingh-85542.)

• typing.get_type_hints() no longer addsOptionalto parameters withNone as a default. (Contributed by Nikita Sobolevingh-90353.)

• typing.get_type_hints() now supports evaluating bare stringifiedClassVar annotations. (Contributed by Gregory Beauregardingh-90711.)

• typing.no_type_check() no longer modifies external classes and functions.It also now correctly marks classmethods as not to be type checked. (Contributedby Nikita Sobolev ingh-90729.)

unicodedata¶

• The Unicode database has been updated to version 14.0.0.(Contributed by Benjamin Peterson inbpo-45190).

unittest¶

• Added methodsenterContext() andenterClassContext() of classTestCase, methodenterAsyncContext() ofclassIsolatedAsyncioTestCase and functionunittest.enterModuleContext().(Contributed by Serhiy Storchaka inbpo-45046.)

venv¶

• When new Python virtual environments are created, thevenvsysconfig installation scheme is usedto determine the paths inside the environment.When Python runs in a virtual environment, the same installation schemeis the default.That means that downstream distributors can change the default sysconfig installscheme without changing behavior of virtual environments.Third party code that also creates new virtual environments should do the same.(Contributed by Miro Hrončok inbpo-45413.)

warnings¶

• warnings.catch_warnings() now accepts arguments forwarnings.simplefilter(),providing a more concise way to locally ignore warnings or convert them to errors.(Contributed by Zac Hatfield-Dodds inbpo-47074.)

zipfile¶

• Added support for specifying member name encoding for reading metadatain aZipFile’s directory and file headers.(Contributed by Stephen J. Turnbull and Serhiy Storchaka inbpo-28080.)

• AddedZipFile.mkdir()for creating new directories inside ZIP archives.(Contributed by Sam Ezeh ingh-49083.)

• Addedstem,suffixandsuffixes tozipfile.Path.(Contributed by Miguel Brito ingh-88261.)

Faster Startup¶

Read __pycache__ -> Unmarshal -> Heap allocated code object -> Evaluate

Statically allocated code object -> Evaluate

Faster Runtime¶

Misc¶

• Objects now require less memory due to lazily created object namespaces.Their namespace dictionaries now also share keys more freely.(Contributed Mark Shannon inbpo-45340 andbpo-40116.)

• “Zero-cost” exceptions are implemented, eliminating the costoftry statements when no exception is raised.(Contributed by Mark Shannon inbpo-40222.)

• A more concise representation of exceptions in the interpreter reduced thetime required for catching an exception by about 10%.(Contributed by Irit Katriel inbpo-45711.)

• re’s regular expression matching engine has been partially refactored,and now uses computed gotos (or “threaded code”) on supported platforms. As aresult, Python 3.11 executes thepyperformance regular expression benchmarks up to 10%faster than Python 3.10.(Contributed by Brandt Bucher ingh-91404.)

FAQ¶

About¶

Faster CPython explores optimizations forCPython. The main team isfunded by Microsoft to work on this full-time. Pablo Galindo Salgado is alsofunded by Bloomberg LP to work on the project part-time. Finally, manycontributors are volunteers from the community.

New opcodes¶

• ASYNC_GEN_WRAP,RETURN_GENERATOR andSEND,used in generators and co-routines.

• COPY_FREE_VARS,which avoids needing special caller-side code for closures.

• JUMP_BACKWARD_NO_INTERRUPT,for use in certain loops where handling interrupts is undesirable.

• MAKE_CELL, to createCell Objects.

• CHECK_EG_MATCH andPREP_RERAISE_STAR,to handle thenew exception groups and except*added inPEP 654.

• PUSH_EXC_INFO, for use in exception handlers.

• RESUME, a no-op,for internal tracing, debugging and optimization checks.

Replaced opcodes¶

All jump opcodes are now relative, including theexistingJUMP_IF_TRUE_OR_POP andJUMP_IF_FALSE_OR_POP.The argument is now an offset from the current instructionrather than an absolute location.

Changed/removed opcodes¶

• ChangedMATCH_CLASS andMATCH_KEYSto no longer push an additional boolean value to indicate success/failure.Instead,None is pushed on failurein place of the tuple of extracted values.

• Changed opcodes that work with exceptions to reflect themnow being represented as one item on the stack instead of three(seegh-89874).

• RemovedCOPY_DICT_WITHOUT_KEYS,GEN_START,POP_BLOCK,SETUP_FINALLY andYIELD_FROM.

Language/Builtins¶

• Chainingclassmethod descriptors (introduced inbpo-19072)is now deprecated. It can no longer be used to wrap other descriptorssuch asproperty. The core design of this feature was flawedand caused a number of downstream problems. To “pass-through” aclassmethod, consider using the__wrapped__ attributethat was added in Python 3.10.(Contributed by Raymond Hettinger ingh-89519.)

• Octal escapes in string and bytes literals with values larger than0o377(255 in decimal) now produce aDeprecationWarning.In a future Python version, they will raise aSyntaxWarning andeventually aSyntaxError.(Contributed by Serhiy Storchaka ingh-81548.)

• The delegation ofint() to__trunc__() is now deprecated.Callingint(a) whentype(a) implements__trunc__() but not__int__() or__index__() now raisesaDeprecationWarning.(Contributed by Zackery Spytz inbpo-44977.)

Modules¶

• PEP 594 led to the deprecations of the following modulesslated for removal in Python 3.13:

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

  (Contributed by Brett Cannon inbpo-47061 and Victor Stinner ingh-68966.)

• Theasynchat,asyncore andsmtpd modules have beendeprecated since at least Python 3.6. Their documentation and deprecationwarnings have now been updated to note they will be removed in Python 3.12.(Contributed by Hugo van Kemenade inbpo-47022.)

• Thelib2to3 package and2to3 toolare now deprecated and may not be able to parse Python 3.10 or newer.SeePEP 617, introducing the new PEG parser, for details.(Contributed by Victor Stinner inbpo-40360.)

• Undocumented modulessre_compile,sre_constantsandsre_parse are now deprecated.(Contributed by Serhiy Storchaka inbpo-47152.)

Standard Library¶

• The following have been deprecated inconfigparser since Python 3.2.Their deprecation warnings have now been updated to note they will be removedin Python 3.12:

  • theconfigparser.SafeConfigParser class

  • theconfigparser.ParsingError.filename property

  • theconfigparser.RawConfigParser.readfp() method

  (Contributed by Hugo van Kemenade inbpo-45173.)

• configparser.LegacyInterpolation has been deprecated in the docstringsince Python 3.2, and is not listed in theconfigparser documentation.It now emits aDeprecationWarning and will be removedin Python 3.13. Useconfigparser.BasicInterpolation orconfigparser.ExtendedInterpolation instead.(Contributed by Hugo van Kemenade inbpo-46607.)

• The older set ofimportlib.resources functions were deprecatedin favor of the replacements added in Python 3.9and will be removed in a future Python version,due to not supporting resources located within package subdirectories:

  • importlib.resources.contents()

  • importlib.resources.is_resource()

  • importlib.resources.open_binary()

  • importlib.resources.open_text()

  • importlib.resources.read_binary()

  • importlib.resources.read_text()

  • importlib.resources.path()

• Thelocale.getdefaultlocale() function is deprecated and will beremoved in Python 3.15. Uselocale.setlocale(),locale.getpreferredencoding(False) andlocale.getlocale() functions instead.(Contributed by Victor Stinner ingh-90817.)

• Thelocale.resetlocale() function is deprecated and will beremoved in Python 3.13. Uselocale.setlocale(locale.LC_ALL,"") instead.(Contributed by Victor Stinner ingh-90817.)

• Stricter rules will now be applied for numerical group referencesand group names inregular expressions.Only sequences of ASCII digits will now be accepted as a numerical reference,and the group name inbytes patterns and replacement stringscan only contain ASCII letters, digits and underscores.For now, a deprecation warning is raised for syntax violating these rules.(Contributed by Serhiy Storchaka ingh-91760.)

• In there module, there.template() functionand the correspondingre.TEMPLATE andre.T flagsare deprecated, as they were undocumented and lacked an obvious purpose.They will be removed in Python 3.13.(Contributed by Serhiy Storchaka and Miro Hrončok ingh-92728.)

• turtle.settiltangle() has been deprecated since Python 3.1;it now emits a deprecation warning and will be removed in Python 3.13. Useturtle.tiltangle() instead (it was earlier incorrectly markedas deprecated, and its docstring is now corrected).(Contributed by Hugo van Kemenade inbpo-45837.)

• typing.Text, which exists solely to provide compatibility supportbetween Python 2 and Python 3 code, is now deprecated. Its removal iscurrently unplanned, but users are encouraged to usestr insteadwherever possible.(Contributed by Alex Waygood ingh-92332.)

• The keyword argument syntax for constructingtyping.TypedDict typesis now deprecated. Support will be removed in Python 3.13. (Contributed byJingchen Ye ingh-90224.)

• webbrowser.MacOSX is deprecated and will be removed in Python 3.13.It is untested, undocumented, and not used bywebbrowser itself.(Contributed by Donghee Na inbpo-42255.)

• The behavior of returning a value from aTestCase andIsolatedAsyncioTestCase test methods (other than thedefaultNone value) is now deprecated.

• Deprecated the following not-formally-documentedunittest functions,scheduled for removal in Python 3.13:

  • unittest.findTestCases()

  • unittest.makeSuite()

  • unittest.getTestCaseNames()

  UseTestLoader methods instead:

  • unittest.TestLoader.loadTestsFromModule()

  • unittest.TestLoader.loadTestsFromTestCase()

  • unittest.TestLoader.getTestCaseNames()

  (Contributed by Erlend E. Aasland inbpo-5846.)

• unittest.TestProgram.usageExit() is marked deprecated, to be removedin 3.13.(Contributed by Carlos Damázio ingh-67048.)

New Features¶

• Add a newPyType_GetName() function to get type’s short name.(Contributed by Hai Shi inbpo-42035.)

• Add a newPyType_GetQualName() function to get type’s qualified name.(Contributed by Hai Shi inbpo-42035.)

• Add newPyThreadState_EnterTracing() andPyThreadState_LeaveTracing() functions to the limited C API tosuspend and resume tracing and profiling.(Contributed by Victor Stinner inbpo-43760.)

• Added thePy_Version constant which bears the same value asPY_VERSION_HEX.(Contributed by Gabriele N. Tornetta inbpo-43931.)

• Py_buffer and APIs are now part of the limited API and the stableABI:

  • PyObject_CheckBuffer()

  • PyObject_GetBuffer()

  • PyBuffer_GetPointer()

  • PyBuffer_SizeFromFormat()

  • PyBuffer_ToContiguous()

  • PyBuffer_FromContiguous()

  • PyObject_CopyData()

  • PyBuffer_IsContiguous()

  • PyBuffer_FillContiguousStrides()

  • PyBuffer_FillInfo()

  • PyBuffer_Release()

  • PyMemoryView_FromBuffer()

  • bf_getbuffer andbf_releasebuffer type slots

  (Contributed by Christian Heimes inbpo-45459.)

• Added thePyType_GetModuleByDef() function, used to get the modulein which a method was defined, in cases where this information is notavailable directly (viaPyCMethod).(Contributed by Petr Viktorin inbpo-46613.)

• Add new functions to pack and unpack C double (serialize and deserialize):PyFloat_Pack2(),PyFloat_Pack4(),PyFloat_Pack8(),PyFloat_Unpack2(),PyFloat_Unpack4() andPyFloat_Unpack8().(Contributed by Victor Stinner inbpo-46906.)

• Add new functions to get frame object attributes:PyFrame_GetBuiltins(),PyFrame_GetGenerator(),PyFrame_GetGlobals(),PyFrame_GetLasti().

• Added two new functions to get and set the active exception instance:PyErr_GetHandledException() andPyErr_SetHandledException().These are alternatives toPyErr_SetExcInfo() andPyErr_GetExcInfo() which work with the legacy 3-tuplerepresentation of exceptions.(Contributed by Irit Katriel inbpo-46343.)

• Added thePyConfig.safe_path member.(Contributed by Victor Stinner ingh-57684.)

Porting to Python 3.11¶

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

• PyErr_SetExcInfo() no longer uses thetype andtracebackarguments, the interpreter now derives those values from the exceptioninstance (thevalue argument). The function still steals referencesof all three arguments.(Contributed by Irit Katriel inbpo-45711.)

• PyErr_GetExcInfo() now derives thetype andtracebackfields of the result from the exception instance (thevalue field).(Contributed by Irit Katriel inbpo-45711.)

• _frozen has a newis_package field to indicate whetheror not the frozen module is a package. Previously, a negative valuein thesize field was the indicator. Now only non-negative valuesbe used forsize.(Contributed by Kumar Aditya inbpo-46608.)

• _PyFrameEvalFunction() now takes_PyInterpreterFrame*as its second parameter, instead ofPyFrameObject*.SeePEP 523 for more details of how to use this function pointer type.

• PyCode_New() andPyCode_NewWithPosOnlyArgs() now takean additionalexception_table argument.Using these functions should be avoided, if at all possible.To get a custom code object: create a code object using the compiler,then get a modified version with thereplace method.

• PyCodeObject no longer has theco_code,co_varnames,co_cellvars andco_freevars fields. Instead, usePyCode_GetCode(),PyCode_GetVarnames(),PyCode_GetCellvars() andPyCode_GetFreevars() respectivelyto access them via the C API.(Contributed by Brandt Bucher inbpo-46841 and Ken Jin ingh-92154andgh-94936.)

• The old trashcan macros (Py_TRASHCAN_SAFE_BEGIN/Py_TRASHCAN_SAFE_END)are now deprecated. They should be replaced by the new macrosPy_TRASHCAN_BEGIN andPy_TRASHCAN_END.

  A tp_dealloc function that has the old macros, such as:

  staticvoidmytype_dealloc(mytype*p){PyObject_GC_UnTrack(p);Py_TRASHCAN_SAFE_BEGIN(p);...Py_TRASHCAN_SAFE_END}

  should migrate to the new macros as follows:

  staticvoidmytype_dealloc(mytype*p){PyObject_GC_UnTrack(p);Py_TRASHCAN_BEGIN(p,mytype_dealloc)...Py_TRASHCAN_END}

  Note thatPy_TRASHCAN_BEGIN has a second argument whichshould be the deallocation function it is in.

  To support older Python versions in the same codebase, youcan define the following macros and use them throughoutthe code (credit: these were copied from themypy codebase):

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

• ThePyType_Ready() function now raises an error if a type is definedwith thePy_TPFLAGS_HAVE_GC flag set but has no traverse function(PyTypeObject.tp_traverse).(Contributed by Victor Stinner inbpo-44263.)

• Heap types with thePy_TPFLAGS_IMMUTABLETYPE flag can now inheritthePEP 590 vectorcall protocol. Previously, this was only possible forstatic types.(Contributed by Erlend E. Aasland inbpo-43908)

• SincePy_TYPE() is changed to a inline static function,Py_TYPE(obj)=new_type must be replaced withPy_SET_TYPE(obj,new_type): see thePy_SET_TYPE() function(available since Python 3.9). For backward compatibility, this macro can beused:

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

  (Contributed by Victor Stinner inbpo-39573.)

• SincePy_SIZE() is changed to a inline static function,Py_SIZE(obj)=new_size must be replaced withPy_SET_SIZE(obj,new_size): see thePy_SET_SIZE() function(available since Python 3.9). For backward compatibility, this macro can beused:

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

  (Contributed by Victor Stinner inbpo-39573.)

• <Python.h> no longer includes the header files<stdlib.h>,<stdio.h>,<errno.h> and<string.h> when thePy_LIMITED_APImacro is set to0x030b0000 (Python 3.11) or higher. C extensions shouldexplicitly include the header files after#include<Python.h>.(Contributed by Victor Stinner inbpo-45434.)

• The non-limited API filescellobject.h,classobject.h,code.h,context.h,funcobject.h,genobject.h andlongintrepr.h have been moved totheInclude/cpython directory. Moreover, theeval.h header file wasremoved. These files must not be included directly, as they are alreadyincluded inPython.h:Include Files. If they havebeen included directly, consider includingPython.h instead.(Contributed by Victor Stinner inbpo-35134.)

• ThePyUnicode_CHECK_INTERNED() macro has been excluded from thelimited C API. It was never usable there, because it used internal structureswhich are not available in the limited C API.(Contributed by Victor Stinner inbpo-46007.)

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

  • PyFrame_Check()

  • PyFrame_GetBack()

  • PyFrame_GetBuiltins()

  • PyFrame_GetGenerator()

  • PyFrame_GetGlobals()

  • PyFrame_GetLasti()

  • PyFrame_GetLocals()

  • PyFrame_Type

  (Contributed by Victor Stinner ingh-93937.)

• ThePyFrameObject structure members have been removed from thepublic C API.

  While the documentation notes that thePyFrameObject fields aresubject to change at any time, they have been stable for a long time and wereused in several popular extensions.

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

  PyFrameObject fields:

  • f_back: usePyFrame_GetBack().

  • f_blockstack: removed.

  • f_builtins: usePyFrame_GetBuiltins().

  • f_code: usePyFrame_GetCode().

  • f_gen: usePyFrame_GetGenerator().

  • f_globals: usePyFrame_GetGlobals().

  • f_iblock: removed.

  • f_lasti: usePyFrame_GetLasti().Code usingf_lasti withPyCode_Addr2Line() should usePyFrame_GetLineNumber() instead; it may be faster.

  • f_lineno: usePyFrame_GetLineNumber()

  • f_locals: usePyFrame_GetLocals().

  • f_stackdepth: removed.

  • f_state: no public API (renamed tof_frame.f_state).

  • f_trace: no public API.

  • f_trace_lines: usePyObject_GetAttrString((PyObject*)frame,"f_trace_lines").

  • f_trace_opcodes: usePyObject_GetAttrString((PyObject*)frame,"f_trace_opcodes").

  • f_localsplus: no public API (renamed tof_frame.localsplus).

  • f_valuestack: removed.

  The Python frame object is now created lazily. A side effect is that thef_back member must not be accessed directly,since its value is now alsocomputed lazily. ThePyFrame_GetBack() function must be calledinstead.

  Debuggers that accessed thef_locals directlymust callPyFrame_GetLocals() instead. They no longer need to callPyFrame_FastToLocalsWithError() orPyFrame_LocalsToFast(),in fact they should not call those functions. The necessary updating of theframe is now managed by the virtual machine.

  Code definingPyFrame_GetCode() on Python 3.8 and older:

  #if PY_VERSION_HEX < 0x030900B1staticinlinePyCodeObject*PyFrame_GetCode(PyFrameObject*frame){Py_INCREF(frame->f_code);returnframe->f_code;}#endif

  Code definingPyFrame_GetBack() on Python 3.8 and older:

  #if PY_VERSION_HEX < 0x030900B1staticinlinePyFrameObject*PyFrame_GetBack(PyFrameObject*frame){Py_XINCREF(frame->f_back);returnframe->f_back;}#endif

  Or use thepythoncapi_compat project to get these twofunctions on older Python versions.

• Changes of thePyThreadState structure members:

  • frame: removed, usePyThreadState_GetFrame() (function addedto Python 3.9 bybpo-40429).Warning: the function returns astrong reference, need to callPy_XDECREF().

  • tracing: changed, usePyThreadState_EnterTracing()andPyThreadState_LeaveTracing()(functions added to Python 3.11 bybpo-43760).

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

  • stackcheck_counter: removed.

  Code definingPyThreadState_GetFrame() on Python 3.8 and older:

  #if PY_VERSION_HEX < 0x030900B1staticinlinePyFrameObject*PyThreadState_GetFrame(PyThreadState*tstate){Py_XINCREF(tstate->frame);returntstate->frame;}#endif

  Code definingPyThreadState_EnterTracing() andPyThreadState_LeaveTracing() on Python 3.10 and older:

  #if PY_VERSION_HEX < 0x030B00A2staticinlinevoidPyThreadState_EnterTracing(PyThreadState*tstate){tstate->tracing++;#if PY_VERSION_HEX >= 0x030A00A1tstate->cframe->use_tracing=0;#elsetstate->use_tracing=0;#endif}staticinlinevoidPyThreadState_LeaveTracing(PyThreadState*tstate){intuse_tracing=(tstate->c_tracefunc!=NULL||tstate->c_profilefunc!=NULL);tstate->tracing--;#if PY_VERSION_HEX >= 0x030A00A1tstate->cframe->use_tracing=use_tracing;#elsetstate->use_tracing=use_tracing;#endif}#endif

  Or usethe pythoncapi-compat project to get these functionson old Python functions.

• Distributors are encouraged to build Python with the optimized Blake2librarylibb2.

• ThePyConfig.module_search_paths_set field must now be set to 1 forinitialization to usePyConfig.module_search_paths to initializesys.path. Otherwise, initialization will recalculate the path and replaceany values added tomodule_search_paths.

• PyConfig_Read() no longer calculates the initial search path, and will notfill any values intoPyConfig.module_search_paths. To calculate defaultpaths and then modify them, finish initialization and usePySys_GetObject()to retrievesys.path as a Python list object and modify it directly.

Deprecated¶

• Deprecate the following functions to configure the Python initialization:

  • PySys_AddWarnOptionUnicode()

  • PySys_AddWarnOption()

  • PySys_AddXOption()

  • PySys_HasWarnOptions()

  • PySys_SetArgvEx()

  • PySys_SetArgv()

  • PySys_SetPath()

  • Py_SetPath()

  • Py_SetProgramName()

  • Py_SetPythonHome()

  • Py_SetStandardStreamEncoding()

  • _Py_SetProgramFullPath()

  Use the newPyConfig API of thePython Initialization Configuration instead (PEP 587).(Contributed by Victor Stinner ingh-88279.)

• Deprecate theob_shash member of thePyBytesObject. UsePyObject_Hash() instead.(Contributed by Inada Naoki inbpo-46864.)

Pending Removal in Python 3.12¶

The following C APIs have been deprecated in earlier Python releases,and will be removed in Python 3.12.

• PyUnicode_AS_DATA()

• PyUnicode_AS_UNICODE()

• PyUnicode_AsUnicodeAndSize()

• PyUnicode_AsUnicode()

• PyUnicode_FromUnicode()

• PyUnicode_GET_DATA_SIZE()

• PyUnicode_GET_SIZE()

• PyUnicode_GetSize()

• PyUnicode_IS_COMPACT()

• PyUnicode_IS_READY()

• PyUnicode_READY()

• PyUnicode_WSTR_LENGTH()

• _PyUnicode_AsUnicode()

• PyUnicode_WCHAR_KIND

• PyUnicodeObject

• PyUnicode_InternImmortal()

Removed¶

• PyFrame_BlockSetup() andPyFrame_BlockPop() have beenremoved.(Contributed by Mark Shannon inbpo-40222.)

• Remove the following math macros using theerrno variable:

  • Py_ADJUST_ERANGE1()

  • Py_ADJUST_ERANGE2()

  • Py_OVERFLOWED()

  • Py_SET_ERANGE_IF_OVERFLOW()

  • Py_SET_ERRNO_ON_MATH_ERROR()

  (Contributed by Victor Stinner inbpo-45412.)

• RemovePy_UNICODE_COPY() andPy_UNICODE_FILL() macros, deprecatedsince Python 3.3. UsePyUnicode_CopyCharacters() ormemcpy()(wchar_t* string), andPyUnicode_Fill() functions instead.(Contributed by Victor Stinner inbpo-41123.)

• Remove thepystrhex.h header file. It only contains private functions.C extensions should only include the main<Python.h> header file.(Contributed by Victor Stinner inbpo-45434.)

• Remove thePy_FORCE_DOUBLE() macro. It was used by thePy_IS_INFINITY() macro.(Contributed by Victor Stinner inbpo-45440.)

• The following items are no longer available whenPy_LIMITED_APIis defined:

  • PyMarshal_WriteLongToFile()

  • PyMarshal_WriteObjectToFile()

  • PyMarshal_ReadObjectFromString()

  • PyMarshal_WriteObjectToString()

  • thePy_MARSHAL_VERSION macro

  These are not part of thelimited API.

  (Contributed by Victor Stinner inbpo-45474.)

• ExcludePyWeakref_GET_OBJECT() from the limited C API. It neverworked since thePyWeakReference structure is opaque in thelimited C API.(Contributed by Victor Stinner inbpo-35134.)

• Remove thePyHeapType_GET_MEMBERS() macro. It was exposed in thepublic C API by mistake, it must only be used by Python internally.Use thePyTypeObject.tp_members member instead.(Contributed by Victor Stinner inbpo-40170.)

• Remove theHAVE_PY_SET_53BIT_PRECISION macro (moved to the internal CAPI).(Contributed by Victor Stinner inbpo-45412.)

• Remove thePy_UNICODE encoder APIs,as they have been deprecated since Python 3.3,are little usedand are inefficient relative to the recommended alternatives.

  The removed functions are:

  • PyUnicode_Encode()

  • PyUnicode_EncodeASCII()

  • PyUnicode_EncodeLatin1()

  • PyUnicode_EncodeUTF7()

  • PyUnicode_EncodeUTF8()

  • PyUnicode_EncodeUTF16()

  • PyUnicode_EncodeUTF32()

  • PyUnicode_EncodeUnicodeEscape()

  • PyUnicode_EncodeRawUnicodeEscape()

  • PyUnicode_EncodeCharmap()

  • PyUnicode_TranslateCharmap()

  • PyUnicode_EncodeDecimal()

  • PyUnicode_TransformDecimalToASCII()

  SeePEP 624 for details andmigration guidance.(Contributed by Inada Naoki inbpo-44029.)

tarfile¶

• The extraction methods intarfile, andshutil.unpack_archive(),have a new afilter argument that allows limiting tar features than may besurprising or dangerous, such as creating files outside the destinationdirectory.SeeExtraction filters for details.In Python 3.12, use without thefilter argument will show aDeprecationWarning.In Python 3.14, the default will switch to'data'.(Contributed by Petr Viktorin inPEP 706.)

OpenSSL¶

• Windows builds and macOS installers from python.org now use OpenSSL 3.0.

ipaddress¶

• Fixedis_global andis_private behavior inIPv4Address,IPv6Address,IPv4Network andIPv6Network.

email¶

• Headers with embedded newlines are now quoted on output.

  Thegenerator will now refuse to serialize (write) headersthat are improperly folded or delimited, such that they would be parsed asmultiple headers or joined with adjacent data.If you need to turn this safety feature off,setverify_generated_headers.(Contributed by Bas Bloemsaat and Petr Viktorin ingh-121650.)

• email.utils.getaddresses() andemail.utils.parseaddr() now return('','') 2-tuples in more situations where invalid email addresses areencountered, instead of potentially inaccurate values.An optionalstrict parameter was added to these two functions:usestrict=False to get the old behavior, accepting malformed inputs.getattr(email.utils,'supports_strict_parsing',False) can be used tocheck if thestrict paramater is available.(Contributed by Thomas Dwyer and Victor Stinner forgh-102988 to improvethe CVE-2023-27043 fix.)

os.path¶

• Thestrict parameter toos.path.realpath() accepts a new value,os.path.ALLOW_MISSING.If used, errors other thanFileNotFoundError will be re-raised;the resulting path can be missing but it will be free of symlinks.(Contributed by Petr Viktorin for CVE 2025-4517.)

tarfile¶

• data_filter() now normalizes symbolic link targets in order toavoid path traversal attacks.(Contributed by Petr Viktorin ingh-127987 and CVE 2025-4138.)

• extractall() now skips fixing up directory attributeswhen a directory was removed or replaced by another kind of file.(Contributed by Petr Viktorin ingh-127987 and CVE 2024-12718.)

• extract() andextractall()now (re-)apply the extraction filter when substituting a link (hard orsymbolic) with a copy of another archive member, and when fixing updirectory attributes.The former raises a new exception,LinkFallbackError.(Contributed by Petr Viktorin for CVE 2025-4330 and CVE 2024-12718.)

• extract() andextractall()no longer extract rejected members whenerrorlevel() is zero.(Contributed by Matt Prodani and Petr Viktorin ingh-112887and CVE 2025-4435.)