.. bpo: 45773
.. date: 2022-02-01-14-30-56
.. nonce: Up77LD
.. release date: 2022-02-03
.. section: Core and Builtins
Remove two invalid "peephole" optimizations from the bytecode compiler.
..
.. bpo: 46564
.. date: 2022-02-01-10-23-21
.. nonce: 6Xc2_H
.. section: Core and Builtins
Do not create frame objects when creating :class:`super` object. Patch by
Kumar Aditya.
..
.. bpo: 45885
.. date: 2022-02-01-01-17-28
.. nonce: CjyNf_
.. section: Core and Builtins
Added more fined-grained specialization failure stats regarding the
``COMPARE_OP`` bytecode.
..
.. bpo: 44977
.. date: 2022-01-30-18-23-08
.. nonce: BQV_zS
.. section: Core and Builtins
The delegation of :func:`int` to :meth:`__trunc__` is now deprecated.
Calling ``int(a)`` when ``type(a)`` implements :meth:`__trunc__` but not
:meth:`__int__` or :meth:`__index__` now raises a :exc:`DeprecationWarning`.
..
.. bpo: 46458
.. date: 2022-01-27-10-49-34
.. nonce: 5Gm3Gv
.. section: Core and Builtins
Reorder code emitted by the compiler for a :keyword:`try`-:keyword:`except`
block so that the :keyword:`else` block's code immediately follows the
:keyword:`try` body (without a jump). This is more optimal for the happy
path.
..
.. bpo: 46527
.. date: 2022-01-25-19-34-55
.. nonce: mQLNPk
.. section: Core and Builtins
Allow passing ``iterable`` as a keyword argument to :func:`enumerate` again.
Patch by Jelle Zijlstra.
..
.. bpo: 46528
.. date: 2022-01-25-17-40-07
.. nonce: 2Qmni9
.. section: Core and Builtins
Replace several stack manipulation instructions (``DUP_TOP``,
``DUP_TOP_TWO``, ``ROT_TWO``, ``ROT_THREE``, ``ROT_FOUR``, and ``ROT_N``)
with new :opcode:`COPY` and :opcode:`SWAP` instructions.
..
.. bpo: 46329
.. date: 2022-01-25-11-44-17
.. nonce: SEhynE
.. section: Core and Builtins
Use two or three bytecodes to implement most calls.
Calls without named arguments are implemented as a sequence of two
instructions: ``PRECALL; CALL``. Calls with named arguments are implemented
as a sequence of three instructions: ``PRECALL; KW_NAMES; CALL``. There are
two different ``PRECALL`` instructions: ``PRECALL_FUNTION`` and
``PRECALL_METHOD``. The latter pairs with ``LOAD_METHOD``.
This partition into pre-call and call allows better specialization, and thus
better performance ultimately.
There is no change in semantics.
..
.. bpo: 46503
.. date: 2022-01-24-21-24-41
.. nonce: 4UrPsE
.. section: Core and Builtins
Fix an assert when parsing some invalid \N escape sequences in f-strings.
..
.. bpo: 46431
.. date: 2022-01-24-16-58-01
.. nonce: N6mKAx
.. section: Core and Builtins
Improve error message on invalid calls to
:meth:`BaseExceptionGroup.__new__`.
..
.. bpo: 46476
.. date: 2022-01-24-15-39-34
.. nonce: cvP1Mr
.. section: Core and Builtins
Fix memory leak in code objects generated by deepfreeze. Patch by Kumar
Aditya.
..
.. bpo: 46481
.. date: 2022-01-23-06-56-33
.. nonce: X_FfnB
.. section: Core and Builtins
Speed up calls to :meth:`weakref.ref.__call__` by using the :pep:`590`
``vectorcall`` calling convention. Patch by Donghee Na.
..
.. bpo: 46417
.. date: 2022-01-22-14-39-23
.. nonce: 3U5SfN
.. section: Core and Builtins
Fix a race condition on setting a type ``__bases__`` attribute: the internal
function ``add_subclass()`` now gets the ``PyTypeObject.tp_subclasses``
member after calling :c:func:`PyWeakref_NewRef` which can trigger a garbage
collection which can indirectly modify ``PyTypeObject.tp_subclasses``. Patch
by Victor Stinner.
..
.. bpo: 46417
.. date: 2022-01-21-12-24-14
.. nonce: i3IqMf
.. section: Core and Builtins
``python -X showrefcount`` now shows the total reference count after
clearing and destroyed the main Python interpreter. Previously, it was shown
before. Patch by Victor Stinner.
..
.. bpo: 43683
.. date: 2022-01-20-17-13-49
.. nonce: BqQ26Z
.. section: Core and Builtins
Add ASYNC_GEN_WRAP opcode to wrap the value to be yielded in async
generators. Removes the need to special case async generators in the
``YIELD_VALUE`` instruction.
..
.. bpo: 46407
.. date: 2022-01-17-23-12-01
.. nonce: 2_5a7R
.. section: Core and Builtins
Optimize some modulo operations in ``Objects/longobject.c``. Patch by
Jeremiah Vivian.
..
.. bpo: 46409
.. date: 2022-01-17-12-57-27
.. nonce: HouS6m
.. section: Core and Builtins
Add new ``RETURN_GENERATOR`` bytecode to make generators. Simplifies calling
Python functions in the VM, as they no longer any need to special case
generator functions.
Also add ``JUMP_NO_INTERRUPT`` bytecode that acts like ``JUMP_ABSOLUTE``,
but does not check for interrupts.
..
.. bpo: 46406
.. date: 2022-01-16-15-40-11
.. nonce: g0mke-
.. section: Core and Builtins
The integer division ``//`` implementation has been optimized to better let
the compiler understand its constraints. It can be 20% faster on the amd64
platform when dividing an int by a value smaller than ``2**30``.
..
.. bpo: 46383
.. date: 2022-01-14-20-55-34
.. nonce: v8MTl4
.. section: Core and Builtins
Fix invalid signature of ``_zoneinfo``'s ``module_free`` function to resolve
a crash on wasm32-emscripten platform.
..
.. bpo: 46361
.. date: 2022-01-12-17-15-17
.. nonce: mgI_j_
.. section: Core and Builtins
Ensure that "small" integers created by :meth:`int.from_bytes` and
:class:`decimal.Decimal` are properly cached.
..
.. bpo: 46161
.. date: 2021-12-23-12-32-45
.. nonce: EljBmu
.. section: Core and Builtins
Fix the class building error when the arguments are constants and
CALL_FUNCTION_EX is used.
..
.. bpo: 46028
.. date: 2021-12-16-15-04-58
.. nonce: zfWacB
.. section: Core and Builtins
Fixes calculation of :data:`sys._base_executable` when inside a virtual
environment that uses symlinks with different binary names than the base
environment provides.
..
.. bpo: 46091
.. date: 2021-12-16-00-24-00
.. nonce: rJ_e_e
.. section: Core and Builtins
Correctly calculate indentation levels for lines with whitespace character
that are ended by line continuation characters. Patch by Pablo Galindo
..
.. bpo: 30512
.. date: 2021-12-12-00-49-19
.. nonce: nU9E9V
.. section: Core and Builtins
Add CAN Socket support for NetBSD.
..
.. bpo: 46045
.. date: 2021-12-11-11-36-48
.. nonce: sfThay
.. section: Core and Builtins
Do not use POSIX semaphores on NetBSD
..
.. bpo: 44024
.. date: 2021-05-04-21-55-49
.. nonce: M9m8Qd
.. section: Core and Builtins
Improve the :exc:`TypeError` message for non-string second arguments passed
to the built-in functions :func:`getattr` and :func:`hasattr`. Patch by Géry
Ogam.
..
.. bpo: 46624
.. date: 2022-02-03-12-07-41
.. nonce: f_Qqh0
.. section: Library
Restore support for non-integer arguments of :func:`random.randrange` and
:func:`random.randint`.
..
.. bpo: 46591
.. date: 2022-01-31-15-40-38
.. nonce: prBD1M
.. section: Library
Make the IDLE doc URL on the About IDLE dialog clickable.
..
.. bpo: 46565
.. date: 2022-01-28-19-48-31
.. nonce: bpZXO4
.. section: Library
Remove loop variables that are leaking into modules' namespaces.
..
.. bpo: 46553
.. date: 2022-01-28-08-47-53
.. nonce: f7Uc96
.. section: Library
In :func:`typing.get_type_hints`, support evaluating bare stringified
``ClassVar`` annotations. Patch by Gregory Beauregard.
..
.. bpo: 46544
.. date: 2022-01-27-13-30-02
.. nonce: oFDVWj
.. section: Library
Don't leak ``x`` & ``uspace`` intermediate vars in
:class:`textwrap.TextWrapper`.
..
.. bpo: 46487
.. date: 2022-01-27-12-24-38
.. nonce: UDkN2z
.. section: Library
Add the ``get_write_buffer_limits`` method to
:class:`asyncio.transports.WriteTransport` and to the SSL transport.
..
.. bpo: 45173
.. date: 2022-01-27-11-16-59
.. nonce: wreRF2
.. section: Library
Note the configparser deprecations will be removed in Python 3.12.
..
.. bpo: 45162
.. date: 2022-01-26-23-58-48
.. nonce: 4Jmg_j
.. section: Library
The deprecated :mod:`unittest` APIs removed in 3.11a1 have been temporarily
restored to be removed in 3.12 while cleanups in external projects go in.
..
.. bpo: 46539
.. date: 2022-01-26-20-36-30
.. nonce: 23iW1d
.. section: Library
In :func:`typing.get_type_hints`, support evaluating stringified
``ClassVar`` and ``Final`` annotations inside ``Annotated``. Patch by
Gregory Beauregard.
..
.. bpo: 46510
.. date: 2022-01-25-10-59-41
.. nonce: PM5svI
.. section: Library
Add missing test for :class:`types.TracebackType` and
:class:`types.FrameType`. Calculate them directly from the caught exception
without calling :func:`sys.exc_info`.
..
.. bpo: 46491
.. date: 2022-01-24-23-55-30
.. nonce: jmIKHo
.. section: Library
Allow :data:`typing.Annotated` to wrap :data:`typing.Final` and
:data:`typing.ClassVar`. Patch by Gregory Beauregard.
..
.. bpo: 46483
.. date: 2022-01-24-13-00-09
.. nonce: 9XnmKp
.. section: Library
Remove :meth:`~object.__class_getitem__` from :class:`pathlib.PurePath` as
this class was not supposed to be generic.
..
.. bpo: 46436
.. date: 2022-01-23-19-37-00
.. nonce: Biz1p9
.. section: Library
Fix command-line option ``-d``/``--directory`` in module :mod:`http.server`
which is ignored when combined with command-line option ``--cgi``. Patch by
Géry Ogam.
..
.. bpo: 41403
.. date: 2022-01-23-18-04-45
.. nonce: SgoHqV
.. section: Library
Make :meth:`mock.patch` raise a :exc:`TypeError` with a relevant error
message on invalid arg. Previously it allowed a cryptic
:exc:`AttributeError` to escape.
..
.. bpo: 46474
.. date: 2022-01-22-14-49-10
.. nonce: eKQhvx
.. section: Library
In ``importlib.metadata.EntryPoint.pattern``, avoid potential REDoS by
limiting ambiguity in consecutive whitespace.
..
.. bpo: 46474
.. date: 2022-01-22-14-45-46
.. nonce: 2DUC62
.. section: Library
Removed private method from ``importlib.metadata.Path``. Sync with
importlib_metadata 4.10.0.
..
.. bpo: 46470
.. date: 2022-01-22-13-17-35
.. nonce: MnNhgU
.. section: Library
Remove unused branch from ``typing._remove_dups_flatten``
..
.. bpo: 46469
.. date: 2022-01-22-05-05-08
.. nonce: plUab5
.. section: Library
:mod:`asyncio` generic classes now return :class:`types.GenericAlias` in
``__class_getitem__`` instead of the same class.
..
.. bpo: 41906
.. date: 2022-01-21-18-19-45
.. nonce: YBaquj
.. section: Library
Support passing filter instances in the ``filters`` values of ``handlers``
and ``loggers`` in the dictionary passed to
:func:`logging.config.dictConfig`.
..
.. bpo: 46422
.. date: 2022-01-20-10-35-50
.. nonce: 1UAEHL
.. section: Library
Use ``dis.Positions`` in ``dis.Instruction`` instead of a regular ``tuple``.
..
.. bpo: 46434
.. date: 2022-01-20-10-35-10
.. nonce: geS-aP
.. section: Library
:mod:`pdb` now gracefully handles ``help`` when :attr:`~module.__doc__` is
missing, for example when run with pregenerated optimized ``.pyc`` files.
..
.. bpo: 43869
.. date: 2022-01-18-17-24-21
.. nonce: NayN12
.. section: Library
Python uses the same time Epoch on all platforms. Add an explicit unit test
to ensure that it's the case. Patch by Victor Stinner.
..
.. bpo: 46414
.. date: 2022-01-17-10-00-02
.. nonce: Ld0b_y
.. section: Library
Add :func:`typing.reveal_type`. Patch by Jelle Zijlstra.
..
.. bpo: 40280
.. date: 2022-01-16-14-07-14
.. nonce: LtFHfF
.. section: Library
:mod:`subprocess` now imports Windows-specific imports when ``msvcrt``
module is available, and POSIX-specific imports on all other platforms. This
gives a clean exception when ``_posixsubprocess`` is not available (e.g.
Emscripten browser target).
..
.. bpo: 40066
.. date: 2022-01-13-11-41-24
.. nonce: 1QuVli
.. section: Library
``IntEnum``, ``IntFlag``, and ``StrEnum`` use the mixed-in type for their
``str()`` and ``format()`` output.
..
.. bpo: 46316
.. date: 2022-01-09-15-04-56
.. nonce: AMTyd0
.. section: Library
Optimize :meth:`pathlib.Path.iterdir` by removing an unnecessary check for
special entries.
..
.. bpo: 29688
.. date: 2022-01-05-03-21-21
.. nonce: W06bSH
.. section: Library
Document :meth:`pathlib.Path.absolute` (which has always existed).
..
.. bpo: 43012
.. date: 2022-01-05-03-09-29
.. nonce: RVhLIL
.. section: Library
The pathlib module's obsolete and internal ``_Accessor`` class has been
removed to prepare the terrain for upcoming enhancements to the module.
..
.. bpo: 46258
.. date: 2022-01-04-18-05-25
.. nonce: DYgwRo
.. section: Library
Speed up :func:`math.isqrt` for small positive integers by replacing two
division steps with a lookup table.
..
.. bpo: 46242
.. date: 2022-01-03-16-25-06
.. nonce: f4l_CL
.. section: Library
Improve error message when creating a new :class:`enum.Enum` type
subclassing an existing ``Enum`` with ``_member_names_`` using
:meth:`enum.Enum.__call__`.
..
.. bpo: 43118
.. date: 2021-12-29-14-42-09
.. nonce: BoVi_5
.. section: Library
Fix a bug in :func:`inspect.signature` that was causing it to fail on some
subclasses of classes with a ``__text_signature__`` referencing module
globals. Patch by Weipeng Hong.
..
.. bpo: 26552
.. date: 2021-12-29-13-42-55
.. nonce: 1BqeAn
.. section: Library
Fixed case where failing :func:`asyncio.ensure_future` did not close the
coroutine. Patch by Kumar Aditya.
..
.. bpo: 21987
.. date: 2021-12-28-11-55-10
.. nonce: avBK-p
.. section: Library
Fix an issue with :meth:`tarfile.TarFile.getmember` getting a directory name
with a trailing slash.
..
.. bpo: 46124
.. date: 2021-12-18-18-41-30
.. nonce: ESPrb7
.. section: Library
Update :mod:`zoneinfo` to rely on importlib.resources traversable API.
..
.. bpo: 46103
.. date: 2021-12-16-23-42-54
.. nonce: LMnZAN
.. section: Library
Now :func:`inspect.getmembers` only gets :attr:`__bases__` attribute from
class type. Patch by Weipeng Hong.
..
.. bpo: 46080
.. date: 2021-12-15-06-29-00
.. nonce: AuQpLt
.. section: Library
Fix exception in argparse help text generation if a
:class:`argparse.BooleanOptionalAction` argument's default is
``argparse.SUPPRESS`` and it has ``help`` specified. Patch by Felix
Fontein.
..
.. bpo: 44791
.. date: 2021-07-31-23-18-50
.. nonce: 4jFdpO
.. section: Library
Fix substitution of :class:`~typing.ParamSpec` in
:data:`~typing.Concatenate` with different parameter expressions.
Substitution with a list of types returns now a tuple of types. Substitution
with ``Concatenate`` returns now a ``Concatenate`` with concatenated lists
of arguments.
..
.. bpo: 46463
.. date: 2022-01-21-21-33-48
.. nonce: fBbdTG
.. section: Documentation
Fixes :file:`escape4chm.py` script used when building the CHM documentation
file
..
.. bpo: 43478
.. date: 2022-02-03-00-21-32
.. nonce: 0nfcam
.. section: Tests
Mocks can no longer be provided as the specs for other Mocks. As a result,
an already-mocked object cannot be passed to ``mock.Mock()``. This can uncover
bugs in tests since these Mock-derived Mocks will always pass certain tests
(e.g. isinstance) and builtin assert functions (e.g.
assert_called_once_with) will unconditionally pass.
..
.. bpo: 46616
.. date: 2022-02-02-18-14-38
.. nonce: URvBtE
.. section: Tests
Ensures ``test_importlib.test_windows`` cleans up registry keys after
completion.
..
.. bpo: 44359
.. date: 2022-02-02-02-24-04
.. nonce: kPPSmN
.. section: Tests
test_ftplib now silently ignores socket errors to prevent logging unhandled
threading exceptions. Patch by Victor Stinner.
..
.. bpo: 46600
.. date: 2022-02-01-17-13-53
.. nonce: FMCk8Z
.. section: Tests
Fix test_gdb.test_pycfunction() for Python built with ``clang -Og``.
Tolerate inlined functions in the gdb traceback. Patch by Victor Stinner.
..
.. bpo: 46542
.. date: 2022-01-31-17-34-13
.. nonce: RTMm1T
.. section: Tests
Fix a Python crash in test_lib2to3 when using Python built in debug mode:
limit the recursion limit. Patch by Victor Stinner.
..
.. bpo: 46576
.. date: 2022-01-29-12-37-53
.. nonce: -prRaV
.. section: Tests
test_peg_generator now disables compiler optimization when testing
compilation of its own C extensions to significantly speed up the testing on
non-debug builds of CPython.
..
.. bpo: 46542
.. date: 2022-01-28-01-17-10
.. nonce: xRLTdj
.. section: Tests
Fix ``test_json`` tests checking for :exc:`RecursionError`: modify these
tests to use ``support.infinite_recursion()``. Patch by Victor Stinner.
..
.. bpo: 13886
.. date: 2022-01-17-13-10-04
.. nonce: 5mZH4b
.. section: Tests
Skip test_builtin PTY tests on non-ASCII characters if the readline module
is loaded. The readline module changes input() behavior, but test_builtin is
not intended to test the readline module. Patch by Victor Stinner.
..
.. bpo: 40280
.. date: 2022-01-16-14-11-57
.. nonce: fNnFfx
.. section: Tests
Add :func:`test.support.requires_fork` decorators to mark tests that require
a working :func:`os.fork`.
..
.. bpo: 40280
.. date: 2022-01-14-23-22-41
.. nonce: nHLWoD
.. section: Tests
Add :func:`test.support.requires_subprocess` decorator to mark tests which
require working :mod:`subprocess` module or ``os.spawn*``. The
wasm32-emscripten platform has no support for processes.
..
.. bpo: 46126
.. date: 2021-12-18-22-23-50
.. nonce: 0LH3Yb
.. section: Tests
Disable 'descriptions' when running tests internally.
..
.. bpo: 46602
.. date: 2022-02-02-02-06-07
.. nonce: 8GaOZ2
.. section: Build
Tidied up configure.ac so that conftest.c is truncated rather than appended.
This assists in the case where the 'rm' of conftest.c fails to happen
between tests. Downstream issues such as a clobbered SOABI can result.
..
.. bpo: 46600
.. date: 2022-02-01-14-07-37
.. nonce: NNLnfj
.. section: Build
Fix the test checking if the C compiler supports ``-Og`` option in the
``./configure`` script to also use ``-Og`` on clang which supports it. Patch
by Victor Stinner.
..
.. bpo: 38472
.. date: 2022-01-26-22-59-12
.. nonce: RxfLho
.. section: Build
Fix GCC detection in setup.py when cross-compiling. The C compiler is now
run with LC_ALL=C. Previously, the detection failed with a German locale.
..
.. bpo: 46513
.. date: 2022-01-25-12-32-37
.. nonce: mPm9B4
.. section: Build
:program:`configure` no longer uses ``AC_C_CHAR_UNSIGNED`` macro and
``pyconfig.h`` no longer defines reserved symbol ``__CHAR_UNSIGNED__``.
..
.. bpo: 46471
.. date: 2022-01-22-11-06-23
.. nonce: 03snrE
.. section: Build
Use global singletons for single byte bytes objects in deepfreeze.
..
.. bpo: 46443
.. date: 2022-01-20-05-27-07
.. nonce: udCVII
.. section: Build
Deepfreeze now uses cached small integers as it saves some space for common
small integers.
..
.. bpo: 46429
.. date: 2022-01-19-04-36-15
.. nonce: y0OtVL
.. section: Build
Merge all deep-frozen files into one for space savings. Patch by Kumar
Aditya.
..
.. bpo: 45569
.. date: 2022-01-09-11-24-54
.. nonce: zCIENy
.. section: Build
The build now defaults to using 30-bit digits for Python integers.
Previously either 15-bit or 30-bit digits would be selected, depending on
the platform. 15-bit digits may still be selected using the
``--enable-big-digits=15`` option to the ``configure`` script, or by
defining ``PYLONG_BITS_IN_DIGIT`` in ``pyconfig.h``.
..
.. bpo: 45925
.. date: 2022-01-08-12-43-31
.. nonce: 38F3NO
.. section: Build
Update Windows installer to use SQLite 3.37.2.
..
.. bpo: 43112
.. date: 2021-02-10-17-54-04
.. nonce: H5Lat6
.. section: Build
Detect musl libc as a separate SOABI (tagged as ``linux-musl``).
..
.. bpo: 33125
.. date: 2022-01-25-14-48-39
.. nonce: 5WyY_J
.. section: Windows
The traditional EXE/MSI based installer for Windows is now available for
ARM64
..
.. bpo: 46362
.. date: 2022-01-13-22-31-09
.. nonce: f2cuEb
.. section: Windows
os.path.abspath("C:\CON") is now fixed to return "\\.\CON", not the same
path. The regression was true of all legacy DOS devices such as COM1, LPT1,
or NUL.
..
.. bpo: 44934
.. date: 2021-09-01-10-48-11
.. nonce: W1xPATH
.. section: Windows
The installer now offers a command-line only option to add the installation
directory to the end of :envvar:`PATH` instead of at the start.
..
.. bpo: 45925
.. date: 2022-01-26-12-04-09
.. nonce: yBSiYO
.. section: macOS
Update macOS installer to SQLite 3.37.2.
..
.. bpo: 45296
.. date: 2022-01-26-19-33-55
.. nonce: LzZKdU
.. section: IDLE
Clarify close, quit, and exit in IDLE. In the File menu, 'Close' and 'Exit'
are now 'Close Window' (the current one) and 'Exit' is now 'Exit IDLE' (by
closing all windows). In Shell, 'quit()' and 'exit()' mean 'close Shell'.
If there are no other windows, this also exits IDLE.
..
.. bpo: 40170
.. date: 2022-01-27-02-51-22
.. nonce: uPolek
.. section: C API
Remove the ``PyHeapType_GET_MEMBERS()`` macro. It was exposed in the public
C API by mistake, it must only be used by Python internally. Use the
``PyTypeObject.tp_members`` member instead. Patch by Victor Stinner.
..
.. bpo: 40170
.. date: 2022-01-27-02-37-18
.. nonce: XxQB0i
.. section: C API
Move _Py_GetAllocatedBlocks() and _PyObject_DebugMallocStats() private
functions to the internal C API. Patch by Victor Stinner.
..
.. bpo: 46433
.. date: 2022-01-19-16-51-54
.. nonce: Er9ApS
.. section: C API
The internal function _PyType_GetModuleByDef now correctly handles
inheritance patterns involving static types.
..
.. bpo: 45459
.. date: 2021-10-18-16-54-24
.. nonce: Y1pEZs
.. section: C API
:c:type:`Py_buffer` and various ``Py_buffer`` related functions are now part
of the limited API and stable ABI.
..
.. bpo: 14916
.. date: 2020-09-11-02-50-41
.. nonce: QN1Y03
.. section: C API
Fixed bug in the tokenizer that prevented ``PyRun_InteractiveOne`` from
parsing from the provided FD.
Codebase Browser
cpython