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Table of Contents
* What's New In Python 3.12
+ Summary - Release highlights
+ Improved Error Messages
+ New Features
+ Other Language Changes
+ New Modules
+ Improved Modules
o array
o asyncio
o inspect
o pathlib
o dis
o fractions
o math
o os
o os.path
o shutil
o sqlite3
o threading
o unicodedata
o unittest
o uuid
o tempfile
o typing
o sys
+ Optimizations
+ CPython bytecode changes
+ Demos and Tools
+ Deprecated
o Pending Removal in Python 3.13
o Pending Removal in Python 3.14
o Pending Removal in Future Versions
+ Removed
+ Porting to Python 3.12
o Changes in the Python API
+ Build Changes
+ C API Changes
o New Features
o Porting to Python 3.12
o Deprecated
o Removed
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What's New In Python 3.12P
Release
3.12.0a7
Date
April 05, 2023
This article explains the new features in Python 3.12, compared to
3.11.
For full details, see the changelog.
Note
Prerelease users should be aware that this document is currently in
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 highlightsP
Important deprecations, removals or restrictions:
* PEP 623, Remove wstr from Unicode
* PEP 632, Remove the distutils package.
Improved Error MessagesP
* Modules from the standard library are now potentially suggested
as part of the error messages displayed by the interpreter when a
NameError is raised to the top level. Contributed by Pablo
Galindo in gh-98254.
>>> sys.version_info
Traceback (most recent call last):
File "", line 1, in
NameError: name 'sys' is not defined. Did you forget to import 'sys'?
* Improve the error suggestion for NameError exceptions for
instances. Now if a NameError is raised in a method and the
instance has an attribute that's exactly equal to the name in the
exception, the suggestion will include self. instead of the
closest match in the method scope. Contributed by Pablo Galindo
in gh-99139.
>>> class A:
... def __init__(self):
... self.blech = 1
...
... def foo(self):
... somethin = blech
>>> A().foo()
File "", line 1
somethin = blech
^^^^^
NameError: name 'blech' is not defined. Did you mean: 'self.blech'?
* Improve the SyntaxError error message when the user types import
x from y instead of from y import x. Contributed by Pablo Galindo
in gh-98931.
>>> import a.y.z from b.y.z
File "", line 1
import a.y.z from b.y.z
^^^^^^^^^^^^^^^^^^^^^^^
SyntaxError: Did you mean to use 'from ... import ...' instead?
* ImportError exceptions raised from failed from import
statements now include suggestions for the value of
based on the available names in . Contributed by Pablo
Galindo in gh-91058.
>>> from collections import chainmap
Traceback (most recent call last):
File "", line 1, in
ImportError: cannot import name 'chainmap' from 'collections'. Did you mean: 'ChainMap'?
New FeaturesP
* Add Python support for the Linux perf profiler through the new
environment variable PYTHONPERFSUPPORT, the new command-line
option -X perf, as well as the new sys.activate_stack_trampoline
(), sys.deactivate_stack_trampoline(), and
sys.is_stack_trampoline_active() APIs. (Design by Pablo Galindo.
Contributed by Pablo Galindo and Christian Heimes with
contributions from Gregory P. Smith [Google] and Mark Shannon in
gh-96123.)
Other Language ChangesP
* 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 raises SyntaxError instead of ValueError 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 of 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.)
* A backslash-character pair that is not a valid escape sequence
now generates a SyntaxWarning, instead of DeprecationWarning. For
example, re.compile("\d+\.\d+") now emits a SyntaxWarning ("\d"
is an invalid escape sequence), use raw strings for regular
expression: re.compile(r"\d+\.\d+"). In a future Python version,
SyntaxError will eventually be raised, instead of SyntaxWarning.
(Contributed by Victor Stinner in gh-98401.)
* Octal escapes with value larger than 0o377 (ex: "\477"),
deprecated in Python 3.11, now produce a SyntaxWarning, instead
of DeprecationWarning. In a future Python version they will be
eventually a SyntaxError. (Contributed by Victor Stinner in
gh-98401.)
* All builtin and extension callables expecting boolean parameters
now accept arguments of any type instead of just bool and int.
(Contributed by Serhiy Storchaka in gh-60203.)
* Variables used in the target part of comprehensions that are not
stored to can now be used in assignment expressions (:=). For
example, in [(b := 1) for a, b.prop in some_iter], the assignment
to b is now allowed. Note that assigning to variables stored to
in the target part of comprehensions (like a) is still
disallowed, as per PEP 572. (Contributed by Nikita Sobolev in
gh-100581.)
* slice objects are now hashable, allowing them to be used as dict
keys and set items. (Contributed by Will Bradshaw and Furkan
Onder in gh-101264.)
New ModulesP
* None yet.
Improved ModulesP
arrayP
* The array.array class now supports subscripting, making it a
generic type. (Contributed by Jelle Zijlstra in gh-98658.)
asyncioP
* On Linux, asyncio uses PidfdChildWatcher by default if
os.pidfd_open() is available and functional instead of
ThreadedChildWatcher. (Contributed by Kumar Aditya in gh-98024.)
* The child watcher classes MultiLoopChildWatcher, FastChildWatcher
, AbstractChildWatcher and SafeChildWatcher 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 and ThreadedChildWatcher otherwise). (Contributed by
Kumar Aditya in gh-94597.)
* asyncio.set_child_watcher(), asyncio.get_child_watcher(),
asyncio.AbstractEventLoopPolicy.set_child_watcher() and
asyncio.AbstractEventLoopPolicy.get_child_watcher() are
deprecated and will be removed in Python 3.14. (Contributed by
Kumar Aditya in gh-94597.)
* Add loop_factory parameter to asyncio.run() to allow specifying a
custom event loop factory. (Contributed by Kumar Aditya in
gh-99388.)
* Add C implementation of asyncio.current_task() for 4x-6x speedup.
(Contributed by Itamar Ostricher and Pranav Thulasiram Bhat in
gh-100344.)
* asyncio.iscoroutine() now returns False for generators as asyncio
does not support legacy generator-based coroutines. (Contributed
by Kumar Aditya in gh-102748.)
* asyncio.wait() now accepts generators yielding tasks.
(Contributed by Kumar Aditya in gh-78530.)
inspectP
* Add inspect.markcoroutinefunction() to mark sync functions that
return a coroutine for use with inspect.iscoroutinefunction().
(Contributed Carlton Gibson in gh-99247.)
* Add inspect.getasyncgenstate() and inspect.getasyncgenlocals()
for determining the current state of asynchronous generators.
(Contributed by Thomas Krennwallner in bpo-35759.)
pathlibP
* Add walk() for walking the directory trees and generating all
file or directory names within them, similar to os.walk().
(Contributed by Stanislav Zmiev in gh-90385.)
* Add walk_up optional parameter to pathlib.PurePath.relative_to()
to allow the insertion of .. entries in the result; this behavior
is more consistent with os.path.relpath(). (Contributed by
Domenico Ragusa in bpo-40358.)
* Add pathlib.Path.is_junction() as a proxy to os.path.isjunction()
. (Contributed by Charles Machalow in gh-99547.)
disP
* 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 new hasarg
collection instead. (Contributed by Irit Katriel in gh-94216.)
fractionsP
* Objects of type fractions.Fraction now support float-style
formatting. (Contributed by Mark Dickinson in gh-100161.)
mathP
* Added math.sumprod() for computing a sum of products.
(Contributed by Raymond Hettinger in gh-100485.)
osP
* Add os.PIDFD_NONBLOCK to open a file descriptor for a process
with os.pidfd_open() in non-blocking mode. (Contributed by Kumar
Aditya in gh-93312.)
* os.DirEntry now includes an os.DirEntry.is_junction() method to
check if the entry is a junction. (Contributed by Charles
Machalow in gh-99547.)
* Add os.listdrives(), os.listvolumes() and os.listmounts()
functions on Windows for enumerating drives, volumes and mount
points. (Contributed by Steve Dower in gh-102519.)
* os.stat() and os.lstat() are now more accurate on Windows. The
st_birthtime field will now be filled with the creation time of
the file, and st_ctime is deprecated but still contains the
creation time (but in the future will return the last metadata
change, for consistency with other platforms). st_dev may be up
to 64 bits and st_ino up to 128 bits depending on your file
system, and st_rdev is always set to zero rather than incorrect
values. Both functions may be significantly faster on newer
releases of Windows. (Contributed by Steve Dower in gh-99726.)
os.pathP
* Add os.path.isjunction() to check if a given path is a junction.
(Contributed by Charles Machalow in gh-99547.)
* Add os.path.splitroot() to split a path into a triad (drive,
root, tail). (Contributed by Barney Gale in gh-101000.)
shutilP
* 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.)
* shutil.rmtree() now accepts a new argument onexc which is an
error handler like onerror but which expects an exception
instance rather than a (typ, val, tb) triplet. onerror is
deprecated and will be removed in Python 3.14. (Contributed by
Irit Katriel in gh-102828.)
* shutil.which() now consults the PATHEXT environment variable to
find matches within PATH on Windows even when the given cmd
includes a directory component. (Contributed by Charles Machalow
in gh-103179.)
shutil.which() will call NeedCurrentDirectoryForExePathW when
querying for executables on Windows to determine if the current
working directory should be prepended to the search path.
(Contributed by Charles Machalow in gh-103179.)
shutil.which() will return a path matching the cmd with a
component from PATHEXT prior to a direct match elsewhere in the
search path on Windows. (Contributed by Charles Machalow in
gh-103179.)
sqlite3P
* Add a command-line interface. (Contributed by Erlend E. Aasland
in gh-77617.)
* Add the autocommit attribute to Connection and the autocommit
parameter to connect() to control PEP 249-compliant transaction
handling. (Contributed by Erlend E. Aasland in gh-83638.)
threadingP
* Add threading.settrace_all_threads() and
threading.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.)
unicodedataP
* The Unicode database has been updated to version 15.0.0.
(Contributed by Benjamin Peterson in gh-96734).
unittestP
Added --durations command line option, showing the N slowest test
cases:
python3 -m unittest --durations=3 lib.tests.test_threading
.....
Slowest test durations
----------------------------------------------------------------------
1.210s test_timeout (Lib.test.test_threading.BarrierTests)
1.003s test_default_timeout (Lib.test.test_threading.BarrierTests)
0.518s test_timeout (Lib.test.test_threading.EventTests)
(0.000 durations hidden. Use -v to show these durations.)
----------------------------------------------------------------------
Ran 158 tests in 9.869s
OK (skipped=3)
(Contributed by Giampaolo Rodola in bpo-4080)
uuidP
* Add a command-line interface. (Contributed by Adam Chhina in
gh-88597.)
tempfileP
The tempfile.NamedTemporaryFile function has a new optional parameter
delete_on_close (Contributed by Evgeny Zorin in gh-58451.)
typingP
* Add typing.override(), an override decorator telling to static
type checkers to verify that a method overrides some method or
attribute of the same name on a base class, as per PEP 698.
(Contributed by Steven Troxler in gh-101564.)
* isinstance() checks against runtime-checkable protocols now use
inspect.getattr_static() rather than hasattr() to lookup whether
attributes exist. This means that descriptors and __getattr__()
methods are no longer unexpectedly evaluated during isinstance()
checks against runtime-checkable protocols. However, it may also
mean that some objects which used to be considered instances of a
runtime-checkable protocol may no longer be considered instances
of that protocol on Python 3.12+, and vice versa. Most users are
unlikely to be affected by this change. (Contributed by Alex
Waygood in gh-102433.)
sysP
* Add sys.activate_stack_trampoline() and
sys.deactivate_stack_trampoline() for activating and deactivating
stack profiler trampolines, and sys.is_stack_trampoline_active()
for querying if stack profiler trampolines are active.
(Contributed by Pablo Galindo and Christian Heimes with
contributions from Gregory P. Smith [Google] and Mark Shannon in
gh-96123.)
* Add sys.last_exc which holds the last unhandled exception that
was raised (for post-mortem debugging use cases). Deprecate the
three fields that have the same information in its legacy form:
sys.last_type, sys.last_value and sys.last_traceback.
(Contributed by Irit Katriel in gh-102778.)
OptimizationsP
* Removed wstr and wstr_length members from Unicode objects. It
reduces object size by 8 or 16 bytes on 64bit platform. (PEP 623)
(Contributed by Inada Naoki in gh-92536.)
* Added experimental support for using the BOLT binary optimizer in
the build process, which improves performance by 1-5%.
(Contributed by Kevin Modzelewski in gh-90536 and tuned by
Dong-hee Na in gh-101525)
* Speed up the regular expression substitution (functions re.sub()
and re.subn() and corresponding re.Pattern methods) for
replacement strings containing group references by 2-3 times.
(Contributed by Serhiy Storchaka in gh-91524.)
CPython bytecode changesP
* Removed the LOAD_METHOD instruction. It has been merged into
LOAD_ATTR. LOAD_ATTR will now behave like the old LOAD_METHOD
instruction if the low bit of its oparg is set. (Contributed by
Ken Jin in gh-93429.)
* Removed the JUMP_IF_FALSE_OR_POP and JUMP_IF_TRUE_OR_POP
instructions. (Contributed by Irit Katriel in gh-102859.)
Demos and ToolsP
* 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.)
DeprecatedP
* typing.Hashable and typing.Sized aliases for
collections.abc.Hashable and collections.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.)
* In execute(), DeprecationWarning is now emitted when named
placeholders are used together with parameters supplied as a
sequence instead of as a dict. Starting from Python 3.14, using
named placeholders with parameters supplied as a sequence will
raise a ProgrammingError. (Contributed by Erlend E. Aasland in
gh-101698.)
* The 3-arg signatures (type, value, traceback) of throw(), throw()
and athrow() are deprecated 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 was ImportWarning).
(Contributed by Brett Cannon in gh-65961.)
* The get_event_loop() method of the default event loop policy now
emits a DeprecationWarning if there is no current event loop set
and it decides to create one. (Contributed by Serhiy Storchaka
and Guido van Rossum in gh-100160.)
* The xml.etree.ElementTree module now emits DeprecationWarning
when testing the truth value of an xml.etree.ElementTree.Element.
Before, the Python implementation emitted FutureWarning, and the
C implementation emitted nothing.
* In accordance with PEP 699, the ma_version_tag field in
PyDictObject is deprecated for extension modules. Accessing this
field will generate a compiler warning at compile time. This
field will be removed in Python 3.14. (Contributed by Ramvikrams
and Kumar Aditya in gh-101193. PEP by Ken Jin.)
* The st_ctime fields return by os.stat() and os.lstat() on Windows
are deprecated. In a future release, they will contain the last
metadata change time, consistent with other platforms. For now,
they still contain the creation time, which is also available in
the new st_birthtime field. (Contributed by Steve Dower in
gh-99726.)
* The sys.last_type, sys.last_value and sys.last_traceback fields
are deprecated. Use sys.last_exc instead. (Contributed by Irit
Katriel in gh-102778.)
* The onerror argument of shutil.rmtree() is deprecated as will be
removed in Python 3.14. Use onexc instead. (Contributed by Irit
Katriel in gh-102828.)
Pending Removal in Python 3.13P
The following modules and APIs have been deprecated in earlier Python
releases, and will be removed in Python 3.13.
Modules (see PEP 594):
* aifc
* audioop
* cgi
* cgitb
* chunk
* crypt
* imghdr
* mailcap
* msilib
* nis
* nntplib
* ossaudiodev
* pipes
* sndhdr
* spwd
* sunau
* telnetlib
* uu
* xdrlib
APIs:
* configparser.LegacyInterpolation (gh-90765)
* locale.getdefaultlocale() (gh-90817)
* turtle.RawTurtle.settiltangle() (gh-50096)
* unittest.findTestCases() (gh-50096)
* unittest.makeSuite() (gh-50096)
* unittest.getTestCaseNames() (gh-50096)
* webbrowser.MacOSX (gh-86421)
Pending Removal in Python 3.14P
* 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:
+ importlib.resources.abc.Traversable
+ importlib.resources.abc.TraversableResources
(Contributed by Jason R. Coombs and Hugo van Kemenade in gh-93963
.)
* Creating immutable types (Py_TPFLAGS_IMMUTABLETYPE) with mutable
bases using the C API.
* Deprecated the isdst parameter in email.utils.localtime().
(Contributed by Alan Williams in gh-72346.)
* __package__ and __cached__ will cease to be set or taken into
consideration by the import system (gh-97879).
* Testing the truth value of an xml.etree.ElementTree.Element is
deprecated and will raise an exception in Python 3.14.
* The default multiprocessing start method will change to a safer
one on Linux, BSDs, and other non-macOS POSIX platforms where
'fork' is currently the default (gh-84559). Adding a runtime
warning about this was deemed too disruptive as the majority of
code is not expected to care. Use the get_context() or
set_start_method() APIs to explicitly specify when your code
requires 'fork'. See Contexts and start methods.
* pty has two undocumented master_open() and slave_open() functions
that have been deprecated since Python 2 but only gained a proper
DeprecationWarning in 3.12. Remove them in 3.14.
* Accessing co_lnotab was deprecated in PEP 626 since 3.10 and was
planned to be removed in 3.12 but it only got a proper
DeprecationWarning in 3.12. May be removed in 3.14. (Contributed
by Nikita Sobolev in gh-101866.)
* The onerror argument of shutil.rmtree() is deprecated in 3.12,
and will be removed in 3.14.
Pending Removal in Future VersionsP
The following APIs were deprecated in earlier Python versions and
will be removed, although there is currently no date scheduled for
their removal.
* typing.Text (gh-92332)
* Currently Python accepts numeric literals immediately followed by
keywords, for example 0in x, 1or x, 0if 1else 2. It allows
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 keywords and, else, for, if, in, is and or. In
a future release it will be changed to a syntax error. (gh-87999)
RemovedP
* Remove the distutils package. It was deprecated in Python 3.10 by
PEP 632 "Deprecate distutils module". For projects still using
distutils and cannot be updated to something else, the setuptools
project can be installed: it still provides distutils.
(Contributed by Victor Stinner in gh-92584.)
* Removed many old deprecated unittest features:
+ A number of TestCase method aliases:
Deprecated alias Method Name Deprecated in
failUnless assertTrue() 3.1
failIf assertFalse() 3.1
failUnlessEqual assertEqual() 3.1
failIfEqual assertNotEqual() 3.1
failUnlessAlmostEqual assertAlmostEqual() 3.1
failIfAlmostEqual assertNotAlmostEqual() 3.1
failUnlessRaises assertRaises() 3.1
assert_ assertTrue() 3.2
assertEquals assertEqual() 3.2
assertNotEquals assertNotEqual() 3.2
assertAlmostEquals assertAlmostEqual() 3.2
assertNotAlmostEquals assertNotAlmostEqual() 3.2
assertRegexpMatches assertRegex() 3.2
assertRaisesRegexp assertRaisesRegex() 3.2
assertNotRegexpMatches assertNotRegex() 3.5
You can use https://github.com/isidentical/teyit to
automatically modernise your unit tests.
+ Undocumented and broken TestCase method
assertDictContainsSubset (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 a filename attribute
or argument. Use the source attribute and argument instead.
+ configparser no longer has a SafeConfigParser class. Use the
shorter ConfigParser name instead.
+ configparser.ConfigParser no longer has a readfp method. Use
read_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 for
str since Python 3.3. Code that previously set the text factory
to OptimizedUnicode can either use str explicitly, or rely on the
default value which is also str.
(Contributed by Erlend E. Aasland in gh-92548.)
* smtpd has been removed according to the schedule in PEP 594,
having been deprecated in Python 3.4.7 and 3.5.4. Use aiosmtpd
PyPI module or any other asyncio-based server instead.
(Contributed by Oleg Iarygin in gh-93243.)
* asynchat and asyncore have been removed according to the schedule
in PEP 594, having been deprecated in Python 3.6. Use asyncio
instead. (Contributed by Nikita Sobolev in gh-96580.)
* Remove io.OpenWrapper and _pyio.OpenWrapper, deprecated in Python
3.10: just use open() instead. The open() (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: use os.urandom() or ssl.RAND_bytes() instead. (Contributed
by Victor Stinner in gh-94199.)
* gzip: Remove the filename attribute of gzip.GzipFile, deprecated
since Python 2.6, use the name attribute instead. In write mode,
the filename attribute added '.gz' file extension if it was not
present. (Contributed by Victor Stinner in gh-94196.)
* Remove the ssl.match_hostname() function. It was deprecated in
Python 3.7. OpenSSL performs hostname matching since Python 3.7,
Python no longer uses the ssl.match_hostname() function.
(Contributed by Victor Stinner in gh-94199.)
* Remove the locale.format() function, deprecated in Python 3.7:
use locale.format_string() instead. (Contributed by Victor
Stinner in gh-94226.)
* hashlib: Remove the pure Python implementation of
hashlib.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 of pbkdf2_hmac() which is faster.
(Contributed by Victor Stinner in gh-94199.)
* xml.etree.ElementTree: Remove the ElementTree.Element.copy()
method of the pure Python implementation, deprecated in Python
3.10, use the copy.copy() function instead. The C implementation
of xml.etree.ElementTree has no copy() method, only a __copy__()
method. (Contributed by Victor Stinner in gh-94383.)
* zipimport: Remove find_loader() and find_module() methods,
deprecated in Python 3.10: use the find_spec() method instead.
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 a ssl.SSLContext object and call its
ssl.SSLContext.wrap_socket method. Any package that still uses
ssl.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
removed Doc/tools/rstlint.py, both in favor of sphinx-lint.
(Contributed by Julien Palard in gh-98179.)
* Remove the keyfile and certfile parameters from the ftplib,
imaplib, poplib and smtplib modules, and the key_file, cert_file
and check_hostname parameters from the http.client module, all
deprecated since Python 3.6. Use the context parameter (
ssl_context in imaplib) instead. (Contributed by Victor Stinner
in gh-94172.)
* ftplib: Remove the FTP_TLS.ssl_version class attribute: use the
context parameter instead. (Contributed by Victor Stinner in
gh-94172.)
* Remove support for obsolete browsers from webbrowser. Removed
browsers include: Grail, Mosaic, Netscape, Galeon, Skipstone,
Iceape, Firebird, and Firefox versions 35 and below (gh-102871).
Porting to Python 3.12P
This section lists previously described changes and other bugfixes
that may require changes to your code.
Changes in the Python APIP
* 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 than randrange(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-based smtpd module deprecated in Python
3.4.7 and 3.5.4. A recommended replacement is the asyncio-based
aiosmtpd PyPI module.
* shlex.split(): Passing None for s argument now raises an
exception, rather than reading sys.stdin. The feature was
deprecated in Python 3.9. (Contributed by Victor Stinner in
gh-94352.)
* The os module no longer accepts bytes-like paths, like bytearray
and memoryview types: only the exact bytes type is accepted for
bytes strings. (Contributed by Victor Stinner in gh-98393.)
* syslog.openlog() and syslog.closelog() now fail if used in
subinterpreters. syslog.syslog() may still be used in
subinterpreters, but now only if syslog.openlog() has already
been called in the main interpreter. These new restrictions do
not apply to the main interpreter, so only a very small set of
users might be affected. This change helps with interpreter
isolation. Furthermore, syslog is a wrapper around process-global
resources, which are best managed from the main interpreter.
(Contributed by Dong-hee Na in gh-99127.)
* The undocumented locking behavior of cached_property() is
removed, because it locked across all instances of the class,
leading to high lock contention. This means that a cached
property getter function could now run more than once for a
single instance, if two threads race. For most simple cached
properties (e.g. those that are idempotent and simply calculate a
value based on other attributes of the instance) this will be
fine. If synchronization is needed, implement locking within the
cached property getter function or around multi-threaded access
points.
Build ChangesP
* Python no longer uses setup.py to build shared C extension
modules. Build parameters like headers and libraries are detected
in configure script. Extensions are built by Makefile. Most
extensions use pkg-config and fall back to manual detection.
(Contributed by Christian Heimes in gh-93939.)
* va_start() with two parameters, like va_start(args, format), is
now required to build Python. va_start() is no longer called with
a single parameter. (Contributed by Kumar Aditya in gh-93207.)
* CPython now uses the ThinLTO option as the default link time
optimization policy if the Clang compiler accepts the flag.
(Contributed by Dong-hee Na in gh-89536.)
* Add COMPILEALL_OPTS variable in Makefile to override compileall
options (default: -j0) in make install. Also merged the 3
compileall commands into a single command to build .pyc files for
all optimization levels (0, 1, 2) at once. (Contributed by Victor
Stinner in gh-99289.)
C API ChangesP
New FeaturesP
* PEP 697: Introduced the Unstable C API tier, intended for
low-level tools like debuggers and JIT compilers. This API may
change in each minor release of CPython without deprecation
warnings. Its contents are marked by the PyUnstable_ prefix in
names.
Code object constructors:
+ PyUnstable_Code_New() (renamed from PyCode_New)
+ PyUnstable_Code_NewWithPosOnlyArgs() (renamed from
PyCode_NewWithPosOnlyArgs)
Extra storage for code objects (PEP 523):
+ PyUnstable_Eval_RequestCodeExtraIndex() (renamed from
_PyEval_RequestCodeExtraIndex)
+ PyUnstable_Code_GetExtra() (renamed from _PyCode_GetExtra)
+ PyUnstable_Code_SetExtra() (renamed from _PyCode_SetExtra)
The original names will continue to be available until the
respective API changes.
(Contributed by Petr Viktorin in gh-101101.)
* Added the new limited C API function PyType_FromMetaclass(),
which generalizes the existing PyType_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:
+ Py_TPFLAGS_HAVE_VECTORCALL
+ PyVectorcall_NARGS()
+ PyVectorcall_Call()
+ vectorcallfunc
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 the immutable flag, Py_TPFLAGS_IMMUTABLETYPE). Mutable
types that do not override tp_call now inherit the
Py_TPFLAGS_HAVE_VECTORCALL flag. (Contributed by Petr Viktorin in
gh-93274.)
The Py_TPFLAGS_MANAGED_DICT and Py_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.
* API for performing calls using the vectorcall protocol was added
to the Limited API:
+ PyObject_Vectorcall()
+ PyObject_VectorcallMethod()
+ PY_VECTORCALL_ARGUMENTS_OFFSET
This means that both the incoming and outgoing ends of the vector
call protocol are now available in the Limited API. (Contributed
by Wenzel Jakob in gh-98586.)
* Added two new public functions, PyEval_SetProfileAllThreads() and
PyEval_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 given PyFunctionObject.
(Contributed by Andrew Frost in gh-92257.)
* The C API now permits registering callbacks via PyDict_AddWatcher
(), PyDict_Watch() and related APIs to be called whenever a
dictionary is modified. This is intended for use by optimizing
interpreters, JIT compilers, or debuggers. (Contributed by Carl
Meyer in gh-91052.)
* Added PyType_AddWatcher() and PyType_Watch() API to register
callbacks to receive notification on changes to a type.
(Contributed by Carl Meyer in gh-91051.)
* Added PyCode_AddWatcher() and PyCode_ClearWatcher() APIs to
register callbacks to receive notification on creation and
destruction of code objects. (Contributed by Itamar Ostricher in
gh-91054.)
* Add PyFrame_GetVar() and PyFrame_GetVarString() functions to get
a frame variable by its name. (Contributed by Victor Stinner in
gh-91248.)
* Add PyErr_GetRaisedException() and PyErr_SetRaisedException() for
saving and restoring the current exception. These functions
return and accept a single exception object, rather than the
triple arguments of the now-deprecated PyErr_Fetch() and
PyErr_Restore(). This is less error prone and a bit more
efficient. (Contributed by Mark Shannon in gh-101578.)
* Add _PyErr_ChainExceptions1, which takes an exception instance,
to replace the legacy-API _PyErr_ChainExceptions, which is now
deprecated. (Contributed by Mark Shannon in gh-101578.)
* Add PyException_GetArgs() and PyException_SetArgs() as
convenience functions for retrieving and modifying the args
passed to the exception's constructor. (Contributed by Mark
Shannon in gh-101578.)
* Add PyErr_DisplayException(), which takes an exception instance,
to replace the legacy-api PyErr_Display(). (Contributed by Irit
Katriel in gh-102755).
Porting to Python 3.12P
* Legacy Unicode APIs based on Py_UNICODE* representation has been
removed. Please migrate to APIs based on UTF-8 or wchar_t*.
* Argument parsing functions like PyArg_ParseTuple() doesn't
support Py_UNICODE* based format (e.g. u, Z) anymore. Please
migrate to other formats for Unicode like s, z, es, and U.
* tp_weaklist for all static builtin types is always NULL. This is
an internal-only field on PyTypeObject 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__() (using PyObject_CallMethod(), for example).
* An unrecognized format character in PyUnicode_FromFormat() and
PyUnicode_FromFormatV() now sets a SystemError. 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() and
PyUnicode_FromFormatV(). (Contributed by Philip Georgi in
gh-95504.)
* Extension classes wanting to add a __dict__ or weak reference
slot should use Py_TPFLAGS_MANAGED_DICT and
Py_TPFLAGS_MANAGED_WEAKREF instead of tp_dictoffset and
tp_weaklistoffset, respectively. The use of tp_dictoffset and
tp_weaklistoffset is still supported, but does not fully support
multiple inheritance (gh-95589), and performance may be worse.
Classes declaring Py_TPFLAGS_MANAGED_DICT should call
_PyObject_VisitManagedDict() and _PyObject_ClearManagedDict() to
traverse and clear their instance's dictionaries. To clear
weakrefs, call PyObject_ClearWeakRefs(), as before.
* The PyUnicode_FSDecoder() function no longer accepts bytes-like
paths, like bytearray and memoryview types: only the exact bytes
type is accepted for bytes strings. (Contributed by Victor
Stinner in gh-98393.)
* The Py_CLEAR, Py_SETREF and Py_XSETREF macros now only evaluate
their arguments once. If an argument has side effects, these side
effects are no longer duplicated. (Contributed by Victor Stinner
in gh-98724.)
* The interpreter's error indicator is now always normalized. This
means that PyErr_SetObject(), PyErr_SetString() and the other
functions that set the error indicator now normalize the
exception before storing it. (Contributed by Mark Shannon in
gh-101578.)
* _Py_RefTotal is no longer authoritative and only kept around for
ABI compabitility. Note that it is an internal global and only
available on debug builds. If you happen to be using it then
you'll need to start using _Py_GetGlobalRefTotal().
DeprecatedP
* Deprecate global configuration variable:
+ Py_DebugFlag: use PyConfig.parser_debug
+ Py_VerboseFlag: use PyConfig.verbose
+ Py_QuietFlag: use PyConfig.quiet
+ Py_InteractiveFlag: use PyConfig.interactive
+ Py_InspectFlag: use PyConfig.inspect
+ Py_OptimizeFlag: use PyConfig.optimization_level
+ Py_NoSiteFlag: use PyConfig.site_import
+ Py_BytesWarningFlag: use PyConfig.bytes_warning
+ Py_FrozenFlag: use PyConfig.pathconfig_warnings
+ Py_IgnoreEnvironmentFlag: use PyConfig.use_environment
+ Py_DontWriteBytecodeFlag: use PyConfig.write_bytecode
+ Py_NoUserSiteDirectory: use PyConfig.user_site_directory
+ Py_UnbufferedStdioFlag: use PyConfig.buffered_stdio
+ Py_HashRandomizationFlag: use PyConfig.use_hash_seed and
PyConfig.hash_seed
+ Py_IsolatedFlag: use PyConfig.isolated
+ Py_LegacyWindowsFSEncodingFlag: use
PyPreConfig.legacy_windows_fs_encoding
+ Py_LegacyWindowsStdioFlag: use PyConfig.legacy_windows_stdio
+ Py_FileSystemDefaultEncoding: use
PyConfig.filesystem_encoding
+ Py_FileSystemDefaultEncodeErrors: use
PyConfig.filesystem_errors
+ Py_UTF8Mode: use PyPreConfig.utf8_mode (see Py_PreInitialize
())
The Py_InitializeFromConfig() API should be used with PyConfig
instead. (Contributed by Victor Stinner in gh-77782.)
* Creating immutable types (Py_TPFLAGS_IMMUTABLETYPE) with mutable
bases is deprecated and will be disabled in Python 3.14.
* The structmember.h header is deprecated, though it continues to
be available and there are no plans to remove it.
Its contents are now available just by including Python.h, with a
Py prefix added if it was missing:
+ PyMemberDef, PyMember_GetOne() and PyMember_SetOne()
+ Type macros like Py_T_INT, Py_T_DOUBLE, etc. (previously
T_INT, T_DOUBLE, etc.)
+ The flags Py_READONLY (previously READONLY) and Py_AUDIT_READ
(previously all uppercase)
Several items are not exposed from Python.h:
+ T_OBJECT (use Py_T_OBJECT_EX)
+ T_NONE (previously undocumented, and pretty quirky)
+ The macro WRITE_RESTRICTED which does nothing.
+ The macros RESTRICTED and READ_RESTRICTED, equivalents of
Py_AUDIT_READ.
+ In some configurations, is not included from
Python.h. It should be included manually when using offsetof
().
The deprecated header continues to provide its original contents
under the original names. Your old code can stay unchanged,
unless the extra include and non-namespaced macros bother you
greatly.
(Contributed in gh-47146 by Petr Viktorin, based on earlier work
by Alexander Belopolsky and Matthias Braun.)
* PyErr_Fetch() and PyErr_Restore() are deprecated. Use
PyErr_GetRaisedException() and PyErr_SetRaisedException()
instead. (Contributed by Mark Shannon in gh-101578.)
* PyErr_Display() is deprecated. Use PyErr_DisplayException()
instead. (Contributed by Irit Katriel in gh-102755).
* _PyErr_ChainExceptions is deprecated. Use _PyErr_ChainExceptions1
instead. (Contributed by Irit Katriel in gh-102192.)
RemovedP
* Remove the token.h header file. There was never any public
tokenizer C API. The token.h header file was only designed to be
used by Python internals. (Contributed by Victor Stinner in
gh-92651.)
* Legacy Unicode APIs have been removed. See PEP 623 for detail.
o PyUnicode_WCHAR_KIND
o PyUnicode_AS_UNICODE()
o PyUnicode_AsUnicode()
o PyUnicode_AsUnicodeAndSize()
o PyUnicode_AS_DATA()
o PyUnicode_FromUnicode()
o PyUnicode_GET_SIZE()
o PyUnicode_GetSize()
o PyUnicode_GET_DATA_SIZE()
* Remove the PyUnicode_InternImmortal() function and the
SSTATE_INTERNED_IMMORTAL macro. (Contributed by Victor Stinner in
gh-85858.)
* Remove Jython compatibility hacks from several stdlib modules and
tests. (Contributed by Nikita Sobolev in gh-99482.)
* Remove _use_broken_old_ctypes_structure_semantics_ flag from
ctypes module. (Contributed by Nikita Sobolev in gh-99285.)
Table of Contents
* What's New In Python 3.12
+ Summary - Release highlights
+ Improved Error Messages
+ New Features
+ Other Language Changes
+ New Modules
+ Improved Modules
o array
o asyncio
o inspect
o pathlib
o dis
o fractions
o math
o os
o os.path
o shutil
o sqlite3
o threading
o unicodedata
o unittest
o uuid
o tempfile
o typing
o sys
+ Optimizations
+ CPython bytecode changes
+ Demos and Tools
+ Deprecated
o Pending Removal in Python 3.13
o Pending Removal in Python 3.14
o Pending Removal in Future Versions
+ Removed
+ Porting to Python 3.12
o Changes in the Python API
+ Build Changes
+ C API Changes
o New Features
o Porting to Python 3.12
o Deprecated
o Removed
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