What’s New In Python 3.12¶
- Release
3.12.0a0
- Date
十月 12, 2022
This article explains the new features in Python 3.12, compared to 3.11.
For full details, see the changelog.
备注
Prerelease users should be aware that this document is currently in draft form. It will be updated substantially as Python 3.12 moves towards release, so it’s worth checking back even after reading earlier versions.
Summary – Release highlights¶
Important deprecations, removals or restrictions:
PEP 623, Remove wstr from Unicode
New Features¶
Other Language Changes¶
types.MappingProxyType
instances are now hashable if the underlying mapping is hashable. (Contributed by Serhiy Storchaka in gh-87995.)memoryview
now supports the half-float type (the “e” format code). (Contributed by Dong-hee Na and Antoine Pitrou in gh-90751.)The parser now raises
SyntaxError
when parsing source code containing null bytes. (Contributed by Pablo Galindo in gh-96670.)ast.parse()
now raisesSyntaxError
instead ofValueError
when parsing source code containing null bytes. (Contributed by Pablo Galindo in gh-96670.)The Garbage Collector now runs only on the eval breaker mechanism of the Python bytecode evaluation loop instead on object allocations. The GC can also run when
PyErr_CheckSignals()
is called so C extensions that need to run for a long time without executing any Python code also have a chance to execute the GC periodically. (Contributed by Pablo Galindo in gh-97922.)
New Modules¶
None yet.
Improved Modules¶
asyncio¶
On Linux,
asyncio
usesPidfdChildWatcher
by default ifos.pidfd_open()
is available and functional instead ofThreadedChildWatcher
. (Contributed by Kumar Aditya in gh-98024.)The child watcher classes
MultiLoopChildWatcher
,FastChildWatcher
andSafeChildWatcher
are deprecated and will be removed in Python 3.14. It is recommended to not manually configure a child watcher as the event loop now uses the best available child watcher for each platform (PidfdChildWatcher
if supported andThreadedChildWatcher
otherwise). (Contributed by Kumar Aditya in gh-94597.)
pathlib¶
dis¶
Pseudo instruction opcodes (which are used by the compiler but do not appear in executable bytecode) are now exposed in the
dis
module.HAVE_ARGUMENT
is still relevant to real opcodes, but it is not useful for pseudo instructions. Use the newhasarg
collection instead. (Contributed by Irit Katriel in gh-94216.)
os¶
Add
os.PIDFD_NONBLOCK
to open a file descriptor for a process withos.pidfd_open()
in non-blocking mode. (Contributed by Kumar Aditya in gh-93312.)
shutil¶
shutil.make_archive()
now passes the root_dir argument to custom archivers which support it. In this case it no longer temporarily changes the current working directory of the process to root_dir to perform archiving. (Contributed by Serhiy Storchaka in gh-74696.)
sqlite3¶
Add a command-line interface. (Contributed by Erlend E. Aasland in gh-77617.)
threading¶
Add
threading.settrace_all_threads()
andthreading.setprofile_all_threads()
that allow to set tracing and profiling functions in all running threads in addition to the calling one. (Contributed by Pablo Galindo in gh-93503.)
unicodedata¶
The Unicode database has been updated to version 15.0.0. (Contributed by Benjamin Peterson in gh-96734).
tempfile¶
The tempfile.NamedTemporaryFile
function has a new optional parameter
delete_on_close (Contributed by Evgeny Zorin in gh-58451.)
Optimizations¶
Removed
wstr
andwstr_length
members from Unicode objects. It reduces object size by 8 or 16 bytes on 64bit platform. (PEP 623) (Contributed by Inada Naoki in gh-92536.)Added experimental support for using the BOLT binary optimizer in the build process, which improves performance by 1-5%. (Contributed by Kevin Modzelewski in gh-90536.)
CPython bytecode changes¶
Removed the
LOAD_METHOD
instruction. It has been merged intoLOAD_ATTR
.LOAD_ATTR
will now behave like the oldLOAD_METHOD
instruction if the low bit of its oparg is set. (Contributed by Ken Jin in gh-93429.)
Demos and Tools¶
Remove the
Tools/demo/
directory which contained old demo scripts. A copy can be found in the old-demos project. (Contributed by Victor Stinner in gh-97681.)Remove outdated example scripts of the
Tools/scripts/
directory. A copy can be found in the old-demos project. (Contributed by Victor Stinner in gh-97669.)
Deprecated¶
typing.Hashable
andtyping.Sized
aliases forcollections.abc.Hashable
andcollections.abc.Sized
. (gh-94309.)The
sqlite3
default adapters and converters are now deprecated. Instead, use the Adapter and converter recipes and tailor them to your needs. (Contributed by Erlend E. Aasland in gh-90016.)The 3-arg signatures (type, value, traceback) of
throw()
,throw()
andathrow()
are deprecated and may be removed in a future version of Python. Use the single-arg versions of these functions instead. (Contributed by Ofey Chan in gh-89874.)DeprecationWarning
is now raised when__package__
on a module differs from__spec__.parent
(previously it wasImportWarning
). (Contributed by Brett Cannon in gh-65961.)
Pending Removal in Python 3.13¶
The following modules and APIs have been deprecated in earlier Python releases, and will be removed in Python 3.13.
Modules (see PEP 594):
APIs:
Pending Removal in Python 3.14¶
Deprecated the following
importlib.abc
classes, scheduled for removal in Python 3.14:importlib.abc.ResourceReader
importlib.abc.Traversable
importlib.abc.TraversableResources
Use
importlib.resources.abc
classes instead:(Contributed by Jason R. Coombs and Hugo van Kemenade in gh-93963.)
Creating
immutable types
with mutable bases using the C API.__package__
and__cached__
will cease to be set or taken into consideration by the import system (gh-97879).
Pending Removal in Future Versions¶
The following APIs were deprecated in earlier Python versions and will be removed, although there is currently no date scheduled for their removal.
Currently Python accepts numeric literals immediately followed by keywords, for example
0in x
,1or x
,0if 1else 2
. It allows confusing and ambiguous expressions like[0x1for x in y]
(which can be interpreted as[0x1 for x in y]
or[0x1f or x in y]
). A syntax warning is raised if the numeric literal is immediately followed by one of keywordsand
,else
,for
,if
,in
,is
andor
. In a future release it will be changed to a syntax error. (gh-87999)
Removed¶
Removed many old deprecated
unittest
features:A number of
TestCase
method aliases:Deprecated alias
Method Name
Deprecated in
failUnless
3.1
failIf
3.1
failUnlessEqual
3.1
failIfEqual
3.1
failUnlessAlmostEqual
3.1
failIfAlmostEqual
3.1
failUnlessRaises
3.1
assert_
3.2
assertEquals
3.2
assertNotEquals
3.2
assertAlmostEquals
3.2
assertNotAlmostEquals
3.2
assertRegexpMatches
3.2
assertRaisesRegexp
3.2
assertNotRegexpMatches
3.5
You can use https://github.com/isidentical/teyit to automatically modernise your unit tests.
Undocumented and broken
TestCase
methodassertDictContainsSubset
(deprecated in Python 3.2).Undocumented
TestLoader.loadTestsFromModule
parameter use_load_tests (deprecated and ignored since Python 3.2).An alias of the
TextTestResult
class:_TextTestResult
(deprecated in Python 3.2).
(Contributed by Serhiy Storchaka in bpo-45162.)
Several names deprecated in the
configparser
way back in 3.2 have been removed per gh-89336:configparser.ParsingError
no longer has afilename
attribute or argument. Use thesource
attribute and argument instead.configparser
no longer has aSafeConfigParser
class. Use the shorterConfigParser
name instead.configparser.ConfigParser
no longer has areadfp
method. Useread_file()
instead.
The following undocumented
sqlite3
features, deprecated in Python 3.10, are now removed:sqlite3.enable_shared_cache()
sqlite3.OptimizedUnicode
If a shared cache must be used, open the database in URI mode using the
cache=shared
query parameter.The
sqlite3.OptimizedUnicode
text factory has been an alias forstr
since Python 3.3. Code that previously set the text factory toOptimizedUnicode
can either usestr
explicitly, or rely on the default value which is alsostr
.(Contributed by Erlend E. Aasland in gh-92548.)
The
--experimental-isolated-subinterpreters
configure flag (and correspondingEXPERIMENTAL_ISOLATED_SUBINTERPRETERS
) have been removed.smtpd
has been removed according to the schedule in PEP 594, having been deprecated in Python 3.4.7 and 3.5.4. Use aiosmtpd PyPI module or any otherasyncio
-based server instead. (Contributed by Oleg Iarygin in gh-93243.)
Remove
io.OpenWrapper
and_pyio.OpenWrapper
, deprecated in Python 3.10: just useopen()
instead. Theopen()
(io.open()
) function is a built-in function. Since Python 3.10,_pyio.open()
is also a static method. (Contributed by Victor Stinner in gh-94169.)Remove the
ssl.RAND_pseudo_bytes()
function, deprecated in Python 3.6: useos.urandom()
orssl.RAND_bytes()
instead. (Contributed by Victor Stinner in gh-94199.)gzip
: Remove thefilename
attribute ofgzip.GzipFile
, deprecated since Python 2.6, use thename
attribute instead. In write mode, thefilename
attribute added'.gz'
file extension if it was not present. (Contributed by Victor Stinner in gh-94196.)Remove the
ssl.match_hostname()
function. Thessl.match_hostname()
was deprecated in Python 3.7. OpenSSL performs hostname matching since Python 3.7, Python no longer uses thessl.match_hostname()
function. (Contributed by Victor Stinner in gh-94199.)Remove the
locale.format()
function, deprecated in Python 3.7: uselocale.format_string()
instead. (Contributed by Victor Stinner in gh-94226.)hashlib
: Remove the pure Python implementation ofhashlib.pbkdf2_hmac()
, deprecated in Python 3.10. Python 3.10 and newer requires OpenSSL 1.1.1 (PEP 644): this OpenSSL version provides a C implementation ofpbkdf2_hmac()
which is faster. (Contributed by Victor Stinner in gh-94199.)xml.etree
: Remove theElementTree.Element.copy()
method of the pure Python implementation, deprecated in Python 3.10, use thecopy.copy()
function instead. The C implementation ofxml.etree
has nocopy()
method, only a__copy__()
method. (Contributed by Victor Stinner in gh-94383.)zipimport
: Removefind_loader()
andfind_module()
methods, deprecated in Python 3.10: use thefind_spec()
method instead. See PEP 451 for the rationale. (Contributed by Victor Stinner in gh-94379.)Remove the
ssl.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 a SNI TLS extension nor validates server hostname. Code is subject to CWE-295: Improper Certificate Validation. (Contributed by Victor Stinner in gh-94199.)Many previously deprecated cleanups in
importlib
have now been completed:References to, and support for
module_repr()
has been eradicated.
importlib.util.set_package
has been removed. (Contributed by Brett Cannon in gh-65961.)Removed the
suspicious
rule from the documentation Makefile, and removedDoc/tools/rstlint.py
, both in favor of sphinx-lint. (Contributed by Julien Palard in gh-98179.)
Porting to Python 3.12¶
This section lists previously described changes and other bugfixes that may require changes to your code.
Changes in the Python API¶
More strict rules are now applied for numerical group references and group 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 only contain ASCII letters and digits and underscore. (Contributed by Serhiy Storchaka in gh-91760.)
Removed randrange() functionality deprecated since Python 3.10. Formerly, randrange(10.0) losslessly converted to randrange(10). Now, it raises a TypeError. Also, the exception raised for non-integral values such as randrange(10.5) or randrange(‘10’) has been changed from ValueError to TypeError. This also prevents bugs where
randrange(1e25)
would silently select from a larger range thanrandrange(10**25)
. (Originally suggested by Serhiy Storchaka gh-86388.)argparse.ArgumentParser
changed encoding and error handler for reading arguments from file (e.g.fromfile_prefix_chars
option) from default text encoding (e.g.locale.getpreferredencoding(False)
) to filesystem encoding and error handler. Argument files should be encoded in UTF-8 instead of ANSI Codepage on Windows.Removed the
asyncore
-basedsmtpd
module deprecated in Python 3.4.7 and 3.5.4. A recommended replacement is theasyncio
-based aiosmtpd PyPI module.shlex.split()
: PassingNone
for s argument now raises an exception, rather than readingsys.stdin
. The feature was deprecated in Python 3.9. (Contributed by Victor Stinner in gh-94352.)
Build Changes¶
Python no longer uses
setup.py
to build shared C extension modules. Build parameters like headers and libraries are detected inconfigure
script. Extensions are built byMakefile
. Most extensions usepkg-config
and fall back to manual detection. (Contributed by Christian Heimes in gh-93939.)va_start()
with two parameters, likeva_start(args, format),
is now required to build Python.va_start()
is no longer called with a single parameter. (Contributed by Kumar Aditya in gh-93207.)CPython now uses the ThinLTO option as the default link time optimization policy if the Clang compiler accepts the flag. (Contributed by Dong-hee Na in gh-89536.)
C API Changes¶
New Features¶
Added the new limited C API function
PyType_FromMetaclass()
, which generalizes the existingPyType_FromModuleAndSpec()
using an additional metaclass argument. (Contributed by Wenzel Jakob in gh-93012.)API for creating objects that can be called using the vectorcall protocol was added to the Limited API:
The
Py_TPFLAGS_HAVE_VECTORCALL
flag is now removed from a class when the class’s__call__()
method is reassigned. This makes vectorcall safe to use with mutable types (i.e. heap types without theimmutable
flag). Mutable types that do not overridetp_call
now inherit thePy_TPFLAGS_HAVE_VECTORCALL
flag. (Contributed by Petr Viktorin in gh-93274.)The
Py_TPFLAGS_MANAGED_DICT
andPy_TPFLAGS_MANAGED_WEAKREF
flags have been added. This allows extensions classes to support object__dict__
and weakrefs with less bookkeeping, using less memory and with faster access.Added two new public functions,
PyEval_SetProfileAllThreads()
andPyEval_SetTraceAllThreads()
, that allow to set tracing and profiling functions in all running threads in addition to the calling one. (Contributed by Pablo Galindo in gh-93503.)Added new function
PyFunction_SetVectorcall()
to the C API which sets the vectorcall field of a givenPyFunctionObject
. (Contributed by Andrew Frost in gh-92257.)The C API now permits registering callbacks via
PyDict_AddWatcher()
,PyDict_AddWatch()
and related APIs to be called whenever a dictionary is modified. This is intended for use by optimizing interpreters, JIT compilers, or debuggers.
Porting to Python 3.12¶
Legacy Unicode APIs based on
Py_UNICODE*
representation has been removed. Please migrate to APIs based on UTF-8 orwchar_t*
.Argument parsing functions like
PyArg_ParseTuple()
doesn’t supportPy_UNICODE*
based format (e.g.u
,Z
) anymore. Please migrate to other formats for Unicode likes
,z
,es
, andU
.tp_weaklist
for all static builtin types is alwaysNULL
. This is an internal-only field onPyTypeObject
but we’re pointing out the change in case someone happens to be accessing the field directly anyway. To avoid breakage, consider using the existing public C-API instead, or, if necessary, the (internal-only)_PyObject_GET_WEAKREFS_LISTPTR()
macro.This internal-only
PyTypeObject.tp_subclasses
may now not be a valid object pointer. Its type was changed to void* to reflect this. We mention this in case someone happens to be accessing the internal-only field directly.To get a list of subclasses, call the Python method
__subclasses__()
(usingPyObject_CallMethod()
, for example).An unrecognized format character in
PyUnicode_FromFormat()
andPyUnicode_FromFormatV()
now sets aSystemError
. In previous versions it caused all the rest of the format string to be copied as-is to the result string, and any extra arguments discarded. (Contributed by Serhiy Storchaka in gh-95781.)Fixed wrong sign placement in
PyUnicode_FromFormat()
andPyUnicode_FromFormatV()
. (Contributed by Philip Georgi in gh-95504.)Extension classes wanting to add a
__dict__
or weak reference slot should usePy_TPFLAGS_MANAGED_DICT
andPy_TPFLAGS_MANAGED_WEAKREF
instead oftp_dictoffset
andtp_weaklistoffset
, respectively. The use oftp_dictoffset
andtp_weaklistoffset
is still supported, but does not fully support multiple inheritance (gh-95589), and performance may be worse. Classes declaringPy_TPFLAGS_MANAGED_DICT
should call_PyObject_VisitManagedDict()
and_PyObject_ClearManagedDict()
to traverse and clear their instance’s dictionaries. To clear weakrefs, callPyObject_ClearWeakRefs()
, as before.
Deprecated¶
Deprecate global configuration variable:
Py_HashRandomizationFlag
: usePyConfig.use_hash_seed
andPyConfig.hash_seed
Py_LegacyWindowsFSEncodingFlag
: usePyConfig.legacy_windows_fs_encoding
Py_LegacyWindowsStdioFlag
: usePyConfig.legacy_windows_stdio
Py_FileSystemDefaultEncoding
: usePyConfig.filesystem_encoding
Py_FileSystemDefaultEncodeErrors
: usePyConfig.filesystem_errors
Py_UTF8Mode
: usePyPreConfig.utf8_mode
(seePy_PreInitialize()
)
The
Py_InitializeFromConfig()
API should be used withPyConfig
instead. (Contributed by Victor Stinner in gh-77782.)Creating
immutable types
with mutable bases is deprecated and will be disabled in Python 3.14.
Removed¶
Remove the
token.h
header file. There was never any public tokenizer C API. Thetoken.h
header file was only designed to be used by Python internals. (Contributed by Victor Stinner in gh-92651.)Leagcy Unicode APIs has been removed. See PEP 623 for detail.
PyUnicode_WCHAR_KIND
PyUnicode_AS_UNICODE()
PyUnicode_AsUnicode()
PyUnicode_AsUnicodeAndSize()
PyUnicode_AS_DATA()
PyUnicode_FromUnicode()
PyUnicode_GET_SIZE()
PyUnicode_GetSize()
PyUnicode_GET_DATA_SIZE()
Remove the
PyUnicode_InternImmortal()
function and theSSTATE_INTERNED_IMMORTAL
macro. (Contributed by Victor Stinner in gh-85858.)