Dictionary Merge & Update Operators¶

Merge (|) and update (|=) operators have been added to the built-indict class. Those complement the existingdict.update and{**d1,**d2} methods of merging dictionaries.

範例：

>>>x={"key1":"value1 from x","key2":"value2 from x"}>>>y={"key2":"value2 from y","key3":"value3 from y"}>>>x|y{'key1': 'value1 from x', 'key2': 'value2 from y', 'key3': 'value3 from y'}>>>y|x{'key2': 'value2 from x', 'key3': 'value3 from y', 'key1': 'value1 from x'}

SeePEP 584 for a full description.(Contributed by Brandt Bucher inbpo-36144.)

New String Methods to Remove Prefixes and Suffixes¶

str.removeprefix(prefix) andstr.removesuffix(suffix) have been addedto easily remove an unneeded prefix or a suffix from a string. Correspondingbytes,bytearray, andcollections.UserString methods have also beenadded. SeePEP 616 for a full description. (Contributed by Dennis Sweeney inbpo-39939.)

Type Hinting Generics in Standard Collections¶

In type annotations you can now use built-in collection types such aslist anddict as generic types instead of importing thecorresponding capitalized types (e.g.List orDict) fromtyping. Some other types in the standard library are also now generic,for examplequeue.Queue.

範例：

defgreet_all(names:list[str])->None:fornameinnames:print("Hello",name)

SeePEP 585 for more details. (Contributed by Guido van Rossum,Ethan Smith, and Batuhan Taşkaya inbpo-39481.)

New Parser¶

Python 3.9 uses a new parser, based onPEG insteadofLL(1). The newparser's performance is roughly comparable to that of the old parser,but the PEG formalism is more flexible than LL(1) when it comes todesigning new language features. We'll start using this flexibilityin Python 3.10 and later.

Theast module uses the new parser and produces the same AST asthe old parser.

In Python 3.10, the old parser will be deleted and so will allfunctionality that depends on it (primarily theparser module,which has long been deprecated). In Python 3.9only, you can switchback to the LL(1) parser using a command line switch (-Xoldparser) or an environment variable (PYTHONOLDPARSER=1).

SeePEP 617 for more details. (Contributed by Guido van Rossum,Pablo Galindo and Lysandros Nikolaou inbpo-40334.)

zoneinfo¶

Thezoneinfo module brings support for the IANA time zone database tothe standard library. It addszoneinfo.ZoneInfo, a concretedatetime.tzinfo implementation backed by the system's time zone data.

範例：

>>>fromzoneinfoimportZoneInfo>>>fromdatetimeimportdatetime,timedelta>>># Daylight saving time>>>dt=datetime(2020,10,31,12,tzinfo=ZoneInfo("America/Los_Angeles"))>>>print(dt)2020-10-31 12:00:00-07:00>>>dt.tzname()'PDT'>>># Standard time>>>dt+=timedelta(days=7)>>>print(dt)2020-11-07 12:00:00-08:00>>>print(dt.tzname())PST

As a fall-back source of data for platforms that don't ship the IANA database,thetzdata module was released as a first-party package -- distributed viaPyPI and maintained by the CPython core team.

graphlib¶

A new module,graphlib, was added that contains thegraphlib.TopologicalSorter class to offer functionality to performtopological sorting of graphs. (Contributed by Pablo Galindo, Tim Peters andLarry Hastings inbpo-17005.)

ast¶

Added theindent option todump() which allows it to produce amultiline indented output.(Contributed by Serhiy Storchaka inbpo-37995.)

Addedast.unparse() as a function in theast module that canbe used to unparse anast.AST object and produce a string with codethat would produce an equivalentast.AST object when parsed.(Contributed by Pablo Galindo and Batuhan Taskaya inbpo-38870.)

Added docstrings to AST nodes that contains the ASDL signature used toconstruct that node. (Contributed by Batuhan Taskaya inbpo-39638.)

asyncio¶

Due to significant security concerns, thereuse_address parameter ofasyncio.loop.create_datagram_endpoint() is no longer supported. This isbecause of the behavior of the socket optionSO_REUSEADDR in UDP. For moredetails, see the documentation forloop.create_datagram_endpoint().(Contributed by Kyle Stanley, Antoine Pitrou, and Yury Selivanov inbpo-37228.)

Added a newcoroutineshutdown_default_executor()that schedules a shutdown for the default executor that waits on theThreadPoolExecutor to finish closing. Also,asyncio.run() has been updated to use the newcoroutine.(Contributed by Kyle Stanley inbpo-34037.)

Addedasyncio.PidfdChildWatcher, a Linux-specific child watcherimplementation that polls process file descriptors. (bpo-38692)

Added a newcoroutineasyncio.to_thread(). It is mainly used forrunning IO-bound functions in a separate thread to avoid blocking the eventloop, and essentially works as a high-level version ofrun_in_executor() that can directly take keyword arguments.(Contributed by Kyle Stanley and Yury Selivanov inbpo-32309.)

When cancelling the task due to a timeout,asyncio.wait_for() will nowwait until the cancellation is complete also in the case whentimeout is<= 0, like it does with positive timeouts.(Contributed by Elvis Pranskevichus inbpo-32751.)

asyncio now raisesTypeError when calling incompatiblemethods with anssl.SSLSocket socket.(Contributed by Ido Michael inbpo-37404.)

compileall¶

Added new possibility to use hardlinks for duplicated.pyc files:hardlink_dupes parameter and --hardlink-dupes command line option.(Contributed by Lumír 'Frenzy' Balhar inbpo-40495.)

Added new options for path manipulation in resulting.pyc files:stripdir,prependdir,limit_sl_dest parameters and -s, -p, -e command line options.Added the possibility to specify the option for an optimization level multiple times.(Contributed by Lumír 'Frenzy' Balhar inbpo-38112.)

concurrent.futures¶

Added a newcancel_futures parameter toconcurrent.futures.Executor.shutdown() that cancels all pending futureswhich have not started running, instead of waiting for them to complete beforeshutting down the executor.(Contributed by Kyle Stanley inbpo-39349.)

Removed daemon threads fromThreadPoolExecutorandProcessPoolExecutor. This improvescompatibility with subinterpreters and predictability in their shutdownprocesses. (Contributed by Kyle Stanley inbpo-39812.)

Workers inProcessPoolExecutor are now spawned ondemand, only when there are no available idle workers to reuse. This optimizesstartup overhead and reduces the amount of lost CPU time to idle workers.(Contributed by Kyle Stanley inbpo-39207.)

curses¶

Addedcurses.get_escdelay(),curses.set_escdelay(),curses.get_tabsize(), andcurses.set_tabsize() functions.(Contributed by Anthony Sottile inbpo-38312.)

datetime¶

Theisocalendar() ofdatetime.dateandisocalendar() ofdatetime.datetimemethods now returns anamedtuple() instead of atuple.(Contributed by Donghee Na inbpo-24416.)

distutils¶

Theupload command now creates SHA2-256 and Blake2b-256 hashdigests. It skips MD5 on platforms that block MD5 digest.(Contributed by Christian Heimes inbpo-40698.)

fcntl¶

Added constantsF_OFD_GETLK,F_OFD_SETLKandF_OFD_SETLKW.(Contributed by Donghee Na inbpo-38602.)

ftplib¶

FTP andFTP_TLS now raise aValueErrorif the given timeout for their constructor is zero to prevent the creation ofa non-blocking socket. (Contributed by Donghee Na inbpo-39259.)

gc¶

When the garbage collector makes a collection in which some objects resurrect(they are reachable from outside the isolated cycles after the finalizers havebeen executed), do not block the collection of all objects that are stillunreachable. (Contributed by Pablo Galindo and Tim Peters inbpo-38379.)

Added a new functiongc.is_finalized() to check if an object has beenfinalized by the garbage collector. (Contributed by Pablo Galindo inbpo-39322.)

hashlib¶

Thehashlib module can now use SHA3 hashes and SHAKE XOF from OpenSSLwhen available.(Contributed by Christian Heimes inbpo-37630.)

Builtin hash modules can now be disabled with./configure--without-builtin-hashlib-hashes or selectively enabled withe.g../configure--with-builtin-hashlib-hashes=sha3,blake2 to force useof OpenSSL based implementation.(Contributed by Christian Heimes inbpo-40479)

http¶

HTTP status codes103EARLY_HINTS,418IM_A_TEAPOT and425TOO_EARLY are added tohttp.HTTPStatus. (Contributed by Donghee Na inbpo-39509 and Ross Rhodes inbpo-39507.)

IDLE and idlelib¶

Added option to toggle cursor blink off. (Contributed by Zackery Spytzinbpo-4603.)

Escape key now closes IDLE completion windows. (Contributed by JohnnyNajera inbpo-38944.)

Added keywords to module name completion list. (Contributed by Terry J.Reedy inbpo-37765.)

New in 3.9 maintenance releases

Make IDLE invokesys.excepthook() (when started without '-n').User hooks were previously ignored. (Contributed by Ken Hilton inbpo-43008.)

The changes above have been backported to 3.8 maintenance releases.

Rearrange the settings dialog. Split the General tab into Windowsand Shell/Ed tabs. Move help sources, which extend the Help menu, to theExtensions tab. Make space for new options and shorten the dialog. Thelatter makes the dialog better fit small screens. (Contributed by Terry JanReedy inbpo-40468.) Move the indent space setting from the Font tab tothe new Windows tab. (Contributed by Mark Roseman and Terry Jan Reedy inbpo-33962.)

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

imaplib¶

IMAP4 andIMAP4_SSL now havean optionaltimeout parameter for their constructors.Also, theopen() method now has an optionaltimeout parameterwith this change. The overridden methods ofIMAP4_SSL andIMAP4_stream were applied to this change.(Contributed by Donghee Na inbpo-38615.)

imaplib.IMAP4.unselect() is added.imaplib.IMAP4.unselect() frees server's resources associated with theselected mailbox and returns the server to the authenticatedstate. This command performs the same actions asimaplib.IMAP4.close(), exceptthat no messages are permanently removed from the currentlyselected mailbox. (Contributed by Donghee Na inbpo-40375.)

importlib¶

To improve consistency with import statements,importlib.util.resolve_name()now raisesImportError instead ofValueError for invalid relativeimport attempts.(Contributed by Ngalim Siregar inbpo-37444.)

Import loaders which publish immutable module objects can now publishimmutable packages in addition to individual modules.(Contributed by Dino Viehland inbpo-39336.)

Addedimportlib.resources.files() function with support forsubdirectories in package data, matching backport inimportlib_resourcesversion 1.5.(Contributed by Jason R. Coombs inbpo-39791.)

Refreshedimportlib.metadata fromimportlib_metadata version 1.6.1.

inspect¶

inspect.BoundArguments.arguments is changed fromOrderedDict to regulardict. (Contributed by Inada Naoki inbpo-36350 andbpo-39775.)

ipaddress¶

ipaddress now supports IPv6 Scoped Addresses (IPv6 address with suffix%<scope_id>).

Scoped IPv6 addresses can be parsed usingipaddress.IPv6Address.If present, scope zone ID is available through thescope_id attribute.(Contributed by Oleksandr Pavliuk inbpo-34788.)

Starting with Python 3.9.5 theipaddress module no longeraccepts any leading zeros in IPv4 address strings.(Contributed by Christian Heimes inbpo-36384).

math¶

Expanded themath.gcd() function to handle multiple arguments.Formerly, it only supported two arguments.(Contributed by Serhiy Storchaka inbpo-39648.)

Addedmath.lcm(): return the least common multiple of specified arguments.(Contributed by Mark Dickinson, Ananthakrishnan and Serhiy Storchaka inbpo-39479 andbpo-39648.)

Addedmath.nextafter(): return the next floating-point value afterxtowardsy.(Contributed by Victor Stinner inbpo-39288.)

Addedmath.ulp(): return the value of the least significant bitof a float.(Contributed by Victor Stinner inbpo-39310.)

multiprocessing¶

Themultiprocessing.SimpleQueue class has a newclose() method to explicitly close thequeue.(Contributed by Victor Stinner inbpo-30966.)

nntplib¶

NNTP andNNTP_SSL now raise aValueErrorif the given timeout for their constructor is zero to prevent the creation ofa non-blocking socket. (Contributed by Donghee Na inbpo-39259.)

os¶

AddedCLD_KILLED andCLD_STOPPED forsi_code.(Contributed by Donghee Na inbpo-38493.)

Exposed the Linux-specificos.pidfd_open() (bpo-38692) andos.P_PIDFD (bpo-38713) for process management with filedescriptors.

Theos.unsetenv() function is now also available on Windows.(Contributed by Victor Stinner inbpo-39413.)

Theos.putenv() andos.unsetenv() functions are now alwaysavailable.(Contributed by Victor Stinner inbpo-39395.)

Addedos.waitstatus_to_exitcode() function:convert a wait status to an exit code.(Contributed by Victor Stinner inbpo-40094.)

pathlib¶

Addedpathlib.Path.readlink() which acts similarly toos.readlink().(Contributed by Girts Folkmanis inbpo-30618)

pdb¶

On Windows nowPdb supports~/.pdbrc.(Contributed by Tim Hopper and Dan Lidral-Porter inbpo-20523.)

poplib¶

POP3 andPOP3_SSL now raise aValueErrorif the given timeout for their constructor is zero to prevent the creation ofa non-blocking socket. (Contributed by Donghee Na inbpo-39259.)

pprint¶

pprint can now pretty-printtypes.SimpleNamespace.(Contributed by Carl Bordum Hansen inbpo-37376.)

pydoc¶

The documentation string is now shown not only for class, function,method etc, but for any object that has its own__doc__attribute.(Contributed by Serhiy Storchaka inbpo-40257.)

random¶

Added a newrandom.Random.randbytes method: generate random bytes.(Contributed by Victor Stinner inbpo-40286.)

signal¶

Exposed the Linux-specificsignal.pidfd_send_signal() for sending tosignals to a process using a file descriptor instead of a pid. (bpo-38712)

smtplib¶

SMTP andSMTP_SSL now raise aValueErrorif the given timeout for their constructor is zero to prevent the creation ofa non-blocking socket. (Contributed by Donghee Na inbpo-39259.)

LMTP constructor now has an optionaltimeout parameter.(Contributed by Donghee Na inbpo-39329.)

socket¶

Thesocket module now exports theCAN_RAW_JOIN_FILTERSconstant on Linux 4.1 and greater.(Contributed by Stefan Tatschner and Zackery Spytz inbpo-25780.)

The socket module now supports theCAN_J1939 protocol onplatforms that support it. (Contributed by Karl Ding inbpo-40291.)

The socket module now has thesocket.send_fds() andsocket.recv_fds() functions. (Contributed by Joannah Nanjekye, ShinyaOkano and Victor Stinner inbpo-28724.)

time¶

On AIX,thread_time() is now implemented withthread_cputime()which has nanosecond resolution, rather thanclock_gettime(CLOCK_THREAD_CPUTIME_ID) which has a resolution of 10 milliseconds.(Contributed by Batuhan Taskaya inbpo-40192)

sys¶

Added a newsys.platlibdir attribute: name of the platform-specificlibrary directory. It is used to build the path of standard library and thepaths of installed extension modules. It is equal to"lib" on mostplatforms. On Fedora and SuSE, it is equal to"lib64" on 64-bit platforms.(Contributed by Jan Matějek, Matěj Cepl, Charalampos Stratakis and Victor Stinner inbpo-1294959.)

Previously,sys.stderr was block-buffered when non-interactive. Nowstderr defaults to always being line-buffered.(Contributed by Jendrik Seipp inbpo-13601.)

tracemalloc¶

Addedtracemalloc.reset_peak() to set the peak size of traced memoryblocks to the current size, to measure the peak of specific pieces of code.(Contributed by Huon Wilson inbpo-40630.)

typing¶

PEP 593 introduced antyping.Annotated type to decorate existingtypes with context-specific metadata and newinclude_extras parameter totyping.get_type_hints() to access the metadata at runtime. (Contributedby Till Varoquaux and Konstantin Kashin.)

unicodedata¶

The Unicode database has been updated to version 13.0.0. (bpo-39926).

venv¶

The activation scripts provided byvenv now all specify their promptcustomization consistently by always using the value specified by__VENV_PROMPT__. Previously some scripts unconditionally used__VENV_PROMPT__, others only if it happened to be set (which was the defaultcase), and one used__VENV_NAME__ instead.(Contributed by Brett Cannon inbpo-37663.)

xml¶

White space characters within attributes are now preserved when serializingxml.etree.ElementTree to XML file. EOLNs are no longer normalizedto "n". This is the result of discussion about how to interpretsection 2.11 of XML spec.(Contributed by Mefistotelis inbpo-39011.)

Python API 的變更¶

• __import__() andimportlib.util.resolve_name() now raiseImportError where it previously raisedValueError. Callerscatching the specific exception type and supporting both Python 3.9 andearlier versions will need to catch both usingexcept(ImportError,ValueError):.

• Thevenv activation scripts no longer special-case when__VENV_PROMPT__ is set to"".

• Theselect.epoll.unregister() method no longer ignores theEBADF error.(Contributed by Victor Stinner inbpo-39239.)

• Thecompresslevel parameter ofbz2.BZ2File became keyword-only,since thebuffering parameter has been removed.(Contributed by Victor Stinner inbpo-39357.)

• Simplified AST for subscription. Simple indices will be represented bytheir value, extended slices will be represented as tuples.Index(value) will return avalue itself,ExtSlice(slices)will returnTuple(slices,Load()).(Contributed by Serhiy Storchaka inbpo-34822.)

• Theimportlib module now ignores thePYTHONCASEOKenvironment variable when the-E or-I command lineoptions are being used.

• Theencoding parameter has been added to the classesftplib.FTP andftplib.FTP_TLS as a keyword-only parameter, and the default encodingis changed from Latin-1 to UTF-8 to followRFC 2640.

• asyncio.loop.shutdown_default_executor() has been added toAbstractEventLoop, meaning alternative event loops thatinherit from it should have this method defined.(Contributed by Kyle Stanley inbpo-34037.)

• The constant values of future flags in the__future__ moduleis updated in order to prevent collision with compiler flags. PreviouslyPyCF_ALLOW_TOP_LEVEL_AWAIT was clashing withCO_FUTURE_DIVISION.(Contributed by Batuhan Taskaya inbpo-39562)

• array('u') now useswchar_t as C type instead ofPy_UNICODE.This change doesn't affect to its behavior becausePy_UNICODE is aliasofwchar_t since Python 3.3.(Contributed by Inada Naoki inbpo-34538.)

• Thelogging.getLogger() API now returns the root logger when passedthe name'root', whereas previously it returned a non-root logger named'root'. This could affect cases where user code explicitly wants anon-root logger named'root', or instantiates a logger usinglogging.getLogger(__name__) in some top-level module called'root.py'.(Contributed by Vinay Sajip inbpo-37742.)

• Division handling ofPurePath now returnsNotImplementedinstead of raising aTypeError when passed something other than aninstance ofstr orPurePath. This allows creatingcompatible classes that don't inherit from those mentioned types.(Contributed by Roger Aiudi inbpo-34775).

• Starting with Python 3.9.5 theipaddress module no longeraccepts any leading zeros in IPv4 address strings. Leading zeros areambiguous and interpreted as octal notation by some libraries. For examplethe legacy functionsocket.inet_aton() treats leading zeros as octalnotatation. glibc implementation of moderninet_pton() doesnot accept any leading zeros.(Contributed by Christian Heimes inbpo-36384).

• codecs.lookup() now normalizes the encoding name the same way asencodings.normalize_encoding(), except thatcodecs.lookup() alsoconverts the name to lower case. For example,"latex+latin1" encodingname is now normalized to"latex_latin1".(Contributed by Jordon Xu inbpo-37751.)

C API 中的改動¶

• Instances ofheap-allocated types (such as those created withPyType_FromSpec() and similar APIs) hold a reference to their typeobject since Python 3.8. As indicated in the "Changes in the C API" of Python3.8, for the vast majority of cases, there should be no side effect but fortypes that have a customtp_traverse function,ensure that all customtp_traverse functions of heap-allocated typesvisit the object's type.

  範例：

  intfoo_traverse(foo_struct*self,visitprocvisit,void*arg){// Rest of the traverse function#if PY_VERSION_HEX >= 0x03090000// This was not needed before Python 3.9 (Python issue 35810 and 40217)Py_VISIT(Py_TYPE(self));#endif}

  If your traverse function delegates totp_traverse of its base class(or another type), ensure thatPy_TYPE(self) is visited only once.Note that onlyheap type are expected to visit the typeintp_traverse.

  For example, if yourtp_traverse function includes:

  base->tp_traverse(self,visit,arg)

  then add:

  #if PY_VERSION_HEX >= 0x03090000// This was not needed before Python 3.9 (bpo-35810 and bpo-40217)if(base->tp_flags&Py_TPFLAGS_HEAPTYPE){// a heap type's tp_traverse already visited Py_TYPE(self)}else{Py_VISIT(Py_TYPE(self));}#else

  （更多資訊請見bpo-35810 與bpo-40217。）

• The functionsPyEval_CallObject,PyEval_CallFunction,PyEval_CallMethod andPyEval_CallObjectWithKeywords are deprecated.UsePyObject_Call() and its variants instead.(See more details inbpo-29548.)

CPython 位元組碼變更¶

• TheLOAD_ASSERTION_ERROR opcode was added for handling theassert statement. Previously, the assert statement would not workcorrectly if theAssertionError exception was being shadowed.(Contributed by Zackery Spytz inbpo-34880.)

• TheCOMPARE_OP opcode was split into four distinct instructions:

  • COMPARE_OP for rich comparisons

  • IS_OP for 'is' and 'is not' tests

  • CONTAINS_OP for 'in' and 'not in' tests

  • JUMP_IF_NOT_EXC_MATCH for checking exceptions in 'try-except'statements.

  （由 Mark Shannon 在bpo-39156 中貢獻。）

新增功能¶

• PEP 573: AddedPyType_FromModuleAndSpec() to associatea module with a class;PyType_GetModule() andPyType_GetModuleState() to retrieve the module and its state; andPyCMethod andMETH_METHOD to allow a method toaccess the class it was defined in.(Contributed by Marcel Plch and Petr Viktorin inbpo-38787.)

• AddedPyFrame_GetCode() function: get a frame code.AddedPyFrame_GetBack() function: get the frame next outer frame.(Contributed by Victor Stinner inbpo-40421.)

• AddedPyFrame_GetLineNumber() to the limited C API.(Contributed by Victor Stinner inbpo-40421.)

• AddedPyThreadState_GetInterpreter() andPyInterpreterState_Get() functions to get the interpreter.AddedPyThreadState_GetFrame() function to get the current frame of aPython thread state.AddedPyThreadState_GetID() function: get the unique identifier of aPython thread state.(Contributed by Victor Stinner inbpo-39947.)

• Added a new publicPyObject_CallNoArgs() function to the C API, whichcalls a callable Python object without any arguments. It is the most efficientway to call a callable Python object without any argument.(Contributed by Victor Stinner inbpo-37194.)

• Changes in the limited C API (ifPy_LIMITED_API macro is defined):

  • ProvidePy_EnterRecursiveCall() andPy_LeaveRecursiveCall()as regular functions for the limited API. Previously, there were defined asmacros, but these macros didn't compile with the limited C API which cannotaccessPyThreadState.recursion_depth field (the structure is opaque inthe limited C API).

  • PyObject_INIT() andPyObject_INIT_VAR() become regular "opaque"function to hide implementation details.

  （由 Victor Stinner 在 38644 和 39542 中貢獻。）

• ThePyModule_AddType() function is added to help adding a typeto a module.(Contributed by Donghee Na inbpo-40024.)

• Added the functionsPyObject_GC_IsTracked() andPyObject_GC_IsFinalized() to the public API to allow to query ifPython objects are being currently tracked or have been already finalized bythe garbage collector respectively.(Contributed by Pablo Galindo Salgado inbpo-40241.)

• Added_PyObject_FunctionStr() to get a user-friendly stringrepresentation of a function-like object.(Patch by Jeroen Demeyer inbpo-37645.)

• AddedPyObject_CallOneArg() for calling an object with onepositional argument(Patch by Jeroen Demeyer inbpo-37483.)

移植至 Python 3.9¶

• PyInterpreterState.eval_frame (PEP 523) now requires a new mandatorytstate parameter (PyThreadState*).(Contributed by Victor Stinner inbpo-38500.)

• Extension modules:m_traverse,m_clear andm_freefunctions ofPyModuleDef are no longer called if the module statewas requested but is not allocated yet. This is the case immediately afterthe module is created and before the module is executed(Py_mod_exec function). More precisely, these functions are not calledifm_size is greater than 0 and the module state (asreturned byPyModule_GetState()) isNULL.

  Extension modules without module state (m_size<=0) are not affected.

• IfPy_AddPendingCall() is called in a subinterpreter, the function isnow scheduled to be called from the subinterpreter, rather than being calledfrom the main interpreter. Each subinterpreter now has its own list ofscheduled calls.(Contributed by Victor Stinner inbpo-39984.)

• The Windows registry is no longer used to initializesys.path whenthe-E option is used (ifPyConfig.use_environment is set to0). This is significant when embedding Python on Windows.(Contributed by Zackery Spytz inbpo-8901.)

• The global variablePyStructSequence_UnnamedField is now a constantand refers to a constant string.(Contributed by Serhiy Storchaka inbpo-38650.)

• ThePyGC_Head structure is now opaque. It is only defined in theinternal C API (pycore_gc.h).(Contributed by Victor Stinner inbpo-40241.)

• ThePy_UNICODE_COPY,Py_UNICODE_FILL,PyUnicode_WSTR_LENGTH,PyUnicode_FromUnicode(),PyUnicode_AsUnicode(),_PyUnicode_AsUnicode, andPyUnicode_AsUnicodeAndSize() aremarked as deprecated in C. They have been deprecated byPEP 393 sincePython 3.3.(Contributed by Inada Naoki inbpo-36346.)

• ThePy_FatalError() function is replaced with a macro which logsautomatically the name of the current function, unless thePy_LIMITED_API macro is defined.(Contributed by Victor Stinner inbpo-39882.)

• The vectorcall protocol now requires that the caller passes only strings askeyword names. (Seebpo-37540 for more information.)

• Implementation details of a number of macros and functions are now hidden:

  • PyObject_IS_GC() macro was converted to a function.

  • ThePyObject_NEW() macro becomes an alias to thePyObject_New macro, and thePyObject_NEW_VAR() macrobecomes an alias to thePyObject_NewVar macro. They no longeraccess directly thePyTypeObject.tp_basicsize member.

  • PyObject_GET_WEAKREFS_LISTPTR() macro was converted to a function:the macro accessed directly thePyTypeObject.tp_weaklistoffsetmember.

  • PyObject_CheckBuffer() macro was converted to a function: the macroaccessed directly thePyTypeObject.tp_as_buffer member.

  • PyIndex_Check() is now always declared as an opaque function to hideimplementation details: removed thePyIndex_Check() macro. The macro accesseddirectly thePyTypeObject.tp_as_number member.

  （更多資訊請見bpo-40170。）

已移除¶

• ExcludedPyFPE_START_PROTECT() andPyFPE_END_PROTECT() macros ofpyfpe.h from the limited C API.(Contributed by Victor Stinner inbpo-38835.)

• Thetp_print slot ofPyTypeObject has been removed.It was used for printing objects to files in Python 2.7 and before. SincePython 3.0, it has been ignored and unused.(Contributed by Jeroen Demeyer inbpo-36974.)

• Changes in the limited C API (ifPy_LIMITED_API macro is defined):

  • Excluded the following functions from the limited C API:

    • PyThreadState_DeleteCurrent()(Contributed by Joannah Nanjekye inbpo-37878.)

    • _Py_CheckRecursionLimit

    • _Py_NewReference()

    • _Py_ForgetReference()

    • _PyTraceMalloc_NewReference()

    • _Py_GetRefTotal()

    • The trashcan mechanism which never worked in the limited C API.

    • PyTrash_UNWIND_LEVEL

    • Py_TRASHCAN_BEGIN_CONDITION

    • Py_TRASHCAN_BEGIN

    • Py_TRASHCAN_END

    • Py_TRASHCAN_SAFE_BEGIN

    • Py_TRASHCAN_SAFE_END

  • Moved following functions and definitions to the internal C API:

    • _PyDebug_PrintTotalRefs()

    • _Py_PrintReferences()

    • _Py_PrintReferenceAddresses()

    • _Py_tracemalloc_config

    • _Py_AddToAllObjects() (specific toPy_TRACE_REFS build)

  （由 Victor Stinner 在 38644 和 39542 中貢獻。）

• Removed_PyRuntime.getframe hook and removed_PyThreadState_GetFramemacro which was an alias to_PyRuntime.getframe. They were only exposedby the internal C API. Removed alsoPyThreadFrameGetter type.(Contributed by Victor Stinner inbpo-39946.)

• Removed the following functions from the C API. CallPyGC_Collect()explicitly to clear all free lists.(Contributed by Inada Naoki and Victor Stinner inbpo-37340,bpo-38896 andbpo-40428.)

  • PyAsyncGen_ClearFreeLists()

  • PyContext_ClearFreeList()

  • PyDict_ClearFreeList()

  • PyFloat_ClearFreeList()

  • PyFrame_ClearFreeList()

  • PyList_ClearFreeList()

  • PyMethod_ClearFreeList() andPyCFunction_ClearFreeList():the free lists of bound method objects have been removed.

  • PySet_ClearFreeList(): the set free list has been removedin Python 3.4.

  • PyTuple_ClearFreeList()

  • PyUnicode_ClearFreeList(): the Unicode free list has been removed inPython 3.3.

• Removed_PyUnicode_ClearStaticStrings() function.(Contributed by Victor Stinner inbpo-39465.)

• RemovedPy_UNICODE_MATCH. It has been deprecated byPEP 393, andbroken since Python 3.3. ThePyUnicode_Tailmatch() function can beused instead.(Contributed by Inada Naoki inbpo-36346.)

• Cleaned header files of interfaces defined but with no implementation.The public API symbols being removed are:_PyBytes_InsertThousandsGroupingLocale,_PyBytes_InsertThousandsGrouping,_Py_InitializeFromArgs,_Py_InitializeFromWideArgs,_PyFloat_Repr,_PyFloat_Digits,_PyFloat_DigitsInit,PyFrame_ExtendStack,_PyAIterWrapper_Type,PyNullImporter_Type,PyCmpWrapper_Type,PySortWrapper_Type,PyNoArgsFunction.(Contributed by Pablo Galindo Salgado inbpo-39372.)

typing¶

The behavior oftyping.Literal was changed to conform withPEP 586and to match the behavior of static type checkers specified in the PEP.

1. Literal now de-duplicates parameters.

2. Equality comparisons betweenLiteral objects are now order independent.

3. Literal comparisons now respect types. For example,Literal[0]==Literal[False] previously evaluated toTrue. It isnowFalse. To support this change, the internally used type cache nowsupports differentiating types.

4. Literal objects will now raise aTypeError exception duringequality comparisons if any of their parameters are nothashable.Note that declaringLiteral with mutable parameters will not throwan error:

   >>>fromtypingimportLiteral>>>Literal[{0}]>>>Literal[{0}]==Literal[{False}]Traceback (most recent call last):  File"<stdin>", line1, in<module>TypeError:unhashable type: 'set'

（由 Yurii Karabas 在bpo-42345 中貢獻。）

macOS 11.0 (Big Sur) and Apple Silicon Mac support¶

As of 3.9.1, Python now fully supports building and running on macOS 11.0(Big Sur) and on Apple Silicon Macs (based on theARM64 architecture).A new universal build variant,universal2, is now available to nativelysupport bothARM64 andIntel64 in one set of executables. Binariescan also now be built on current versions of macOS to be deployed on a rangeof older macOS versions (tested to 10.9) while making some newer OSfunctions and options conditionally available based on the operating systemversion in use at runtime ("weaklinking").

（由 Ronald Oussoren 和 Lawrence D'Anna 在bpo-41100 中貢獻。）

collections.abc¶

collections.abc.Callable generic now flattens type parameters, similarto whattyping.Callable currently does. This means thatcollections.abc.Callable[[int,str],str] will have__args__ of(int,str,str); previously this was([int,str],str). To allow thischange,types.GenericAlias can now be subclassed, and a subclass willbe returned when subscripting thecollections.abc.Callable type.Code which accesses the arguments viatyping.get_args() or__args__need to account for this change. ADeprecationWarning may be emitted forinvalid forms of parameterizingcollections.abc.Callable which may havepassed silently in Python 3.9.1. ThisDeprecationWarning willbecome aTypeError in Python 3.10.(Contributed by Ken Jin inbpo-42195.)

urllib.parse¶

Earlier Python versions allowed using both; and& asquery parameter separators inurllib.parse.parse_qs() andurllib.parse.parse_qsl(). Due to security concerns, and to conform withnewer W3C recommendations, this has been changed to allow only a singleseparator key, with& as the default. This change also affectscgi.parse() andcgi.parse_multipart() as they use the affectedfunctions internally. For more details, please see their respectivedocumentation.(Contributed by Adam Goldschmidt, Senthil Kumaran and Ken Jin inbpo-42967.)

urllib.parse¶

The presence of newline or tab characters in parts of a URL allows for someforms of attacks. Following the WHATWG specification that updatesRFC 3986,ASCII newline\n,\r and tab\t characters are stripped from theURL by the parser inurllib.parse preventing such attacks. The removalcharacters are controlled by a new module level variableurllib.parse._UNSAFE_URL_BYTES_TO_REMOVE. (Seegh-88048)

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.)