cpython/Misc/NEWS.d/3.10.0a4.rst

.. bpo: 42814
.. date: 2021-01-03-04-41-25
.. nonce: sDvVbb
.. release date: 2021-01-04
.. section: Core and Builtins

Fix undefined behavior in ``Objects/genericaliasobject.c``.

..

.. bpo: 42806
.. date: 2021-01-03-00-20-38
.. nonce: mLAobJ
.. section: Core and Builtins

Fix the column offsets for f-strings :mod:`ast` nodes surrounded by
parentheses and for nodes that spawn multiple lines. Patch by Pablo Galindo.

..

.. bpo: 40631
.. date: 2020-12-31-20-58-22
.. nonce: deRMCx
.. section: Core and Builtins

Fix regression where a single parenthesized starred expression was a valid
assignment target.

..

.. bpo: 27794
.. date: 2020-12-27-18-07-43
.. nonce: sxgfGi
.. section: Core and Builtins

Improve the error message for failed writes/deletes to property objects.
When possible, the attribute name is now shown. Patch provided by Yurii
Karabas.

..

.. bpo: 42745
.. date: 2020-12-25-23-30-58
.. nonce: XsFoHS
.. section: Core and Builtins

Make the type attribute lookup cache per-interpreter. Patch by Victor
Stinner.

..

.. bpo: 42246
.. date: 2020-12-22-20-30-11
.. nonce: 7BrPLg
.. section: Core and Builtins

Jumps to jumps are not eliminated when it would break PEP 626.

..

.. bpo: 42246
.. date: 2020-12-16-14-44-21
.. nonce: RtIEY7
.. section: Core and Builtins

Make sure that the ``f_lasti`` and ``f_lineno`` attributes of a frame are
set correctly when an exception is raised or re-raised. Required for PEP
626.

..

.. bpo: 32381
.. date: 2020-12-15-18-43-43
.. nonce: 3tIofL
.. section: Core and Builtins

The coding cookie (ex: ``# coding: latin1``) is now ignored in the command
passed to the :option:`-c` command line option. Patch by Victor Stinner.

..

.. bpo: 30858
.. date: 2020-12-13-15-23-09
.. nonce: -f9G4z
.. section: Core and Builtins

Improve error location in expressions that contain assignments. Patch by
Pablo Galindo and Lysandros Nikolaou.

..

.. bpo: 42615
.. date: 2020-12-10-17-06-52
.. nonce: Je6Q-r
.. section: Core and Builtins

Remove jump commands made redundant by the deletion of unreachable bytecode
blocks

..

.. bpo: 42639
.. date: 2020-12-09-01-55-10
.. nonce: 5pI5HG
.. section: Core and Builtins

Make the :mod:`atexit` module state per-interpreter. It is now safe have
more than one :mod:`atexit` module instance. Patch by Donghee Na and Victor
Stinner.

..

.. bpo: 32381
.. date: 2020-12-04-17-17-44
.. nonce: NY5t2S
.. section: Core and Builtins

Fix encoding name when running a ``.pyc`` file on Windows:
:c:func:`PyRun_SimpleFileExFlags()` now uses the correct encoding to decode
the filename.

..

.. bpo: 42195
.. date: 2020-11-20-00-57-47
.. nonce: HeqcpS
.. section: Core and Builtins

The ``__args__`` of the parameterized generics for :data:`typing.Callable`
and :class:`collections.abc.Callable` are now consistent.  The ``__args__``
for :class:`collections.abc.Callable` are now flattened while
:data:`typing.Callable`'s have not changed.  To allow this change,
:class:`types.GenericAlias` can now be subclassed and
``collections.abc.Callable``'s ``__class_getitem__`` will now return a
subclass of ``types.GenericAlias``.  Tests for typing were also updated to
not subclass things like ``Callable[..., T]`` as that is not a valid base
class.  Finally, both ``Callable``\ s no longer validate their ``argtypes``,
in ``Callable[[argtypes], resulttype]`` to prepare for :pep:`612`.  Patch by
Ken Jin.

..

.. bpo: 40137
.. date: 2020-11-19-23-12-57
.. nonce: bihl9O
.. section: Core and Builtins

Convert functools module to use :c:func:`PyType_FromModuleAndSpec`.

..

.. bpo: 40077
.. date: 2020-11-03-13-46-10
.. nonce: NfAIdj
.. section: Core and Builtins

Convert :mod:`array` to use heap types, and establish module state for
these.

..

.. bpo: 42008
.. date: 2020-10-12-14-51-59
.. nonce: ijWw2I
.. section: Core and Builtins

Fix _random.Random() seeding.

..

.. bpo: 1635741
.. date: 2020-09-12-19-21-52
.. nonce: F2kDrU
.. section: Core and Builtins

Port the :mod:`pyexpat` extension module to multi-phase initialization
(:pep:`489`).

..

.. bpo: 40521
.. date: 2020-05-14-02-55-39
.. nonce: dIlXsZ
.. section: Core and Builtins

Make the Unicode dictionary of interned strings compatible with
subinterpreters. Patch by Victor Stinner.

..

.. bpo: 39465
.. date: 2020-05-13-18-50-27
.. nonce: j7nl6A
.. section: Core and Builtins

Make :c:func:`!_PyUnicode_FromId` function compatible with subinterpreters.
Each interpreter now has an array of identifier objects (interned strings
decoded from UTF-8). Patch by Victor Stinner.

..

.. bpo: 42257
.. date: 2020-12-31-23-05-53
.. nonce: ALQy7B
.. section: Library

Handle empty string in variable executable in platform.libc_ver()

..

.. bpo: 42772
.. date: 2020-12-30-17-16-43
.. nonce: Xe7WFV
.. section: Library

randrange() now raises a TypeError when step is specified without a stop
argument.  Formerly, it silently ignored the step argument.

..

.. bpo: 42759
.. date: 2020-12-27-22-19-26
.. nonce: lGi_03
.. section: Library

Fixed equality comparison of :class:`tkinter.Variable` and
:class:`tkinter.font.Font`. Objects which belong to different Tcl
interpreters are now always different, even if they have the same name.

..

.. bpo: 42756
.. date: 2020-12-27-21-22-01
.. nonce: dHMPJ9
.. section: Library

Configure LMTP Unix-domain socket to use socket global default timeout when
a timeout is not explicitly provided.

..

.. bpo: 23328
.. date: 2020-12-27-18-47-01
.. nonce: _xqepZ
.. section: Library

Allow / character in username, password fields on _PROXY envars.

..

.. bpo: 42740
.. date: 2020-12-25-23-23-11
.. nonce: F0rQ_E
.. section: Library

:func:`typing.get_args` and :func:`typing.get_origin` now support :pep:`604`
union types and :pep:`612` additions to ``Callable``.

..

.. bpo: 42655
.. date: 2020-12-25-12-32-47
.. nonce: W5ytpV
.. section: Library

:mod:`subprocess` *extra_groups* is now correctly passed into setgroups()
system call.

..

.. bpo: 42727
.. date: 2020-12-23-19-43-06
.. nonce: WH3ODh
.. section: Library

``EnumMeta.__prepare__`` now accepts ``**kwds`` to properly support
``__init_subclass__``

..

.. bpo: 38308
.. date: 2020-12-23-15-16-12
.. nonce: lB4Sv0
.. section: Library

Add optional *weights* to *statistics.harmonic_mean()*.

..

.. bpo: 42721
.. date: 2020-12-22-22-47-22
.. nonce: I5Ai5L
.. section: Library

When simple query dialogs (:mod:`tkinter.simpledialog`), message boxes
(:mod:`tkinter.messagebox`) or color choose dialog
(:mod:`tkinter.colorchooser`) are created without arguments *master* and
*parent*, and the default root window is not yet created, and
:func:`~tkinter.NoDefaultRoot` was not called, a new temporal hidden root
window will be created automatically. It will not be set as the default root
window and will be destroyed right after closing the dialog window. It will
help to use these simple dialog windows in programs which do not need other
GUI.

..

.. bpo: 25246
.. date: 2020-12-22-13-16-43
.. nonce: GhhCTl
.. section: Library

Optimized :meth:`collections.deque.remove`.

..

.. bpo: 35728
.. date: 2020-12-21-23-34-57
.. nonce: 9m-azF
.. section: Library

Added a root parameter to :func:`tkinter.font.nametofont`.

..

.. bpo: 15303
.. date: 2020-12-21-22-59-26
.. nonce: zozVrq
.. section: Library

:mod:`tkinter` supports now widgets with boolean value False.

..

.. bpo: 42681
.. date: 2020-12-20-22-50-15
.. nonce: lDO6jb
.. section: Library

Fixed range checks for color and pair numbers in :mod:`curses`.

..

.. bpo: 42685
.. date: 2020-12-19-17-32-43
.. nonce: kwZlwp
.. section: Library

Improved placing of simple query windows in Tkinter (such as
:func:`tkinter.simpledialog.askinteger`). They are now centered at the
center of the parent window if it is specified and shown, otherwise at the
center of the screen.

..

.. bpo: 9694
.. date: 2020-12-19-12-33-38
.. nonce: CkKK9V
.. section: Library

Argparse help no longer uses the confusing phrase, "optional arguments". It
uses "options" instead.

..

.. bpo: 1635741
.. date: 2020-12-16-23-28-52
.. nonce: Quy3zn
.. section: Library

Port the :mod:`!_thread` extension module to the multiphase initialization
API (:pep:`489`) and convert its static types to heap types.

..

.. bpo: 37961
.. date: 2020-12-16-16-16-33
.. nonce: jrESEq
.. section: Library

Fix crash in :func:`tracemalloc.Traceback.__repr__` (regressed in Python
3.9).

..

.. bpo: 42630
.. date: 2020-12-15-17-51-27
.. nonce: jf4jBl
.. section: Library

:mod:`tkinter` functions and constructors which need a default root window
raise now :exc:`RuntimeError` with descriptive message instead of obscure
:exc:`AttributeError` or :exc:`NameError` if it is not created yet or cannot
be created automatically.

..

.. bpo: 42639
.. date: 2020-12-15-15-14-29
.. nonce: uJ3h8I
.. section: Library

:func:`atexit._run_exitfuncs` now logs callback exceptions using
:data:`sys.unraisablehook`, rather than logging them directly into
:data:`sys.stderr` and raise the last exception.

..

.. bpo: 42644
.. date: 2020-12-15-10-00-04
.. nonce: XgLCNx
.. section: Library

``logging.disable`` will now validate the types and value of its parameter.
It also now accepts strings representing the levels (as does
``logging.setLevel``) instead of only the numerical values.

..

.. bpo: 42639
.. date: 2020-12-14-22-31-22
.. nonce: 5Z3iWX
.. section: Library

At Python exit, if a callback registered with :func:`atexit.register` fails,
its exception is now logged. Previously, only some exceptions were logged,
and the last exception was always silently ignored.

..

.. bpo: 36541
.. date: 2020-12-14-08-23-57
.. nonce: qdEtZv
.. section: Library

Fixed lib2to3.pgen2 to be able to parse PEP-570 positional only argument
syntax.

..

.. bpo: 42382
.. date: 2020-12-13-22-05-35
.. nonce: 2YtKo5
.. section: Library

In ``importlib.metadata``: -  ``EntryPoint`` objects now expose a ``.dist``
object referencing the ``Distribution`` when constructed from a
``Distribution``. - Add support for package discovery under package
normalization rules. - The object returned by ``metadata()`` now has a
formally defined protocol called ``PackageMetadata`` with declared support
for the ``.get_all()`` method. - Synced with importlib_metadata 3.3.

..

.. bpo: 41877
.. date: 2020-12-10-19-49-52
.. nonce: wiVlPc
.. section: Library

A check is added against misspellings of autospect, auto_spec and set_spec
being passed as arguments to patch, patch.object and create_autospec.

..

.. bpo: 39717
.. date: 2020-12-10-18-36-52
.. nonce: sK2u0w
.. section: Library

[tarfile] update nested exception raising to use ``from None`` or ``from e``

..

.. bpo: 41877
.. date: 2020-12-10-09-24-44
.. nonce: iJSCvM
.. section: Library

AttributeError for suspected misspellings of assertions on mocks are now
pointing out that the cause are misspelled assertions and also what to do if
the misspelling is actually an intended attribute name. The unittest.mock
document is also updated to reflect the current set of recognised
misspellings.

..

.. bpo: 41559
.. date: 2020-12-10-00-09-40
.. nonce: 1l4yjP
.. section: Library

Implemented :pep:`612`: added ``ParamSpec`` and ``Concatenate`` to
:mod:`typing`.  Patch by Ken Jin.

..

.. bpo: 42385
.. date: 2020-12-09-19-45-32
.. nonce: boGbjo
.. section: Library

StrEnum: fix _generate_next_value_ to return a str

..

.. bpo: 31904
.. date: 2020-12-09-15-23-28
.. nonce: g3k5k3
.. section: Library

Define THREAD_STACK_SIZE for VxWorks.

..

.. bpo: 34750
.. date: 2020-12-09-14-15-48
.. nonce: x8TASR
.. section: Library

[Enum] ``_EnumDict.update()`` is now supported.

..

.. bpo: 42517
.. date: 2020-12-09-10-59-16
.. nonce: FKEVcZ
.. section: Library

Enum: private names do not become members / do not generate errors -- they
remain normal attributes

..

.. bpo: 42678
.. date: 2020-12-08-22-43-35
.. nonce: ba9ktU
.. section: Library

``Enum``: call ``__init_subclass__`` after members have been added

..

.. bpo: 28964
.. date: 2020-12-07-13-21-00
.. nonce: UTQikc
.. section: Library

:func:`ast.literal_eval` adds line number information (if available) in
error message for malformed nodes.

..

.. bpo: 42470
.. date: 2020-12-06-12-00-00
.. nonce: iqtC4L
.. section: Library

:func:`random.sample` no longer warns on a sequence which is also a set.

..

.. bpo: 31904
.. date: 2020-11-27-18-09-59
.. nonce: g8k43d
.. section: Library

:func:`posixpath.expanduser` returns the input *path* unchanged if user home
directory is None on VxWorks.

..

.. bpo: 42388
.. date: 2020-11-22-11-22-28
.. nonce: LMgM6B
.. section: Library

Fix subprocess.check_output(..., input=None) behavior when text=True to be
consistent with that of the documentation and universal_newlines=True.

..

.. bpo: 34463
.. date: 2020-11-20-19-00-27
.. nonce: aJcm56
.. section: Library

Fixed discrepancy between :mod:`traceback` and the interpreter in formatting
of SyntaxError with lineno not set (:mod:`traceback` was changed to match
interpreter).

..

.. bpo: 42393
.. date: 2020-11-17-22-06-15
.. nonce: BB0oXc
.. section: Library

Raise :exc:`OverflowError` instead of silent truncation in
:meth:`socket.ntohs` and :meth:`socket.htons`.  Silent truncation was
deprecated in Python 3.7. Patch by Erlend E. Aasland

..

.. bpo: 42222
.. date: 2020-10-31-10-28-32
.. nonce: Cfl1eR
.. section: Library

Harmonized :func:`random.randrange` argument handling to match :func:`range`.

* The integer test and conversion in ``randrange()`` now uses
  :func:`operator.index`.
* Non-integer arguments to ``randrange()`` are deprecated.
* The ``ValueError`` is deprecated in favor of a ``TypeError``.
* It now runs a little faster than before.

(Contributed by Raymond Hettinger and Serhiy Storchaka.)

..

.. bpo: 42163
.. date: 2020-10-29-09-22-56
.. nonce: O4VcCY
.. section: Library

Restore compatibility for ``uname_result`` around deepcopy and _replace.

..

.. bpo: 42090
.. date: 2020-10-25-14-48-57
.. nonce: Ubuc0j
.. section: Library

``zipfile.Path.joinpath`` now accepts arbitrary arguments, same as
``pathlib.Path.joinpath``.

..

.. bpo: 1635741
.. date: 2020-10-20-23-28-55
.. nonce: Iyka3r
.. section: Library

Port the _csv module to the multi-phase initialization API (:pep:`489`).

..

.. bpo: 42059
.. date: 2020-10-17-12-42-08
.. nonce: ZGMZ3D
.. section: Library

:class:`typing.TypedDict` types created using the alternative call-style
syntax now correctly respect the ``total`` keyword argument when setting
their ``__required_keys__`` and ``__optional_keys__`` class attributes.

..

.. bpo: 41960
.. date: 2020-10-06-23-59-20
.. nonce: icQ7Xd
.. section: Library

Add ``globalns`` and ``localns`` parameters to the :func:`inspect.signature`
and :meth:`inspect.Signature.from_callable`.

..

.. bpo: 41907
.. date: 2020-10-02-10-19-49
.. nonce: wiIEsz
.. section: Library

fix ``format()`` behavior for ``IntFlag``

..

.. bpo: 41891
.. date: 2020-09-30-13-35-29
.. nonce: pNAeYI
.. section: Library

Ensure asyncio.wait_for waits for task completion

..

.. bpo: 24792
.. date: 2020-09-11-16-07-00
.. nonce: Z-ARra
.. section: Library

Fixed bug where :mod:`zipimporter` sometimes reports an incorrect cause of
import errors.

..

.. bpo: 31904
.. date: 2020-08-11-17-44-07
.. nonce: cb13ea
.. section: Library

Fix site and sysconfig modules for VxWorks RTOS which has no home
directories.

..

.. bpo: 41462
.. date: 2020-08-03-17-54-32
.. nonce: ek38d_
.. section: Library

Add :func:`os.set_blocking` support for VxWorks RTOS.

..

.. bpo: 40219
.. date: 2020-07-13-19-43-11
.. nonce: MUoJEP
.. section: Library

Lowered :class:`tkinter.ttk.LabeledScale` dummy widget to prevent hiding
part of the content label.

..

.. bpo: 37193
.. date: 2020-06-12-21-23-20
.. nonce: wJximU
.. section: Library

Fixed memory leak in ``socketserver.ThreadingMixIn`` introduced in Python
3.7.

..

.. bpo: 39068
.. date: 2019-12-16-17-55-31
.. nonce: Ti3f9P
.. section: Library

Fix initialization race condition in :func:`a85encode` and :func:`b85encode`
in :mod:`base64`. Patch by Brandon Stansbury.

..

.. bpo: 17140
.. date: 2020-12-16-21-06-16
.. nonce: 1leSEg
.. section: Documentation

Add documentation for the :class:`multiprocessing.pool.ThreadPool` class.

..

.. bpo: 34398
.. date: 2019-03-04-18-51-21
.. nonce: YedUqW
.. section: Documentation

Prominently feature listings from the glossary in documentation search
results. Patch by Ammar Askar.

..

.. bpo: 42794
.. date: 2021-01-01-08-52-36
.. nonce: -7-XGz
.. section: Tests

Update test_nntplib to use official group name of news.aioe.org for testing.
Patch by Donghee Na.

..

.. bpo: 31904
.. date: 2020-12-17-15-42-44
.. nonce: d8g3l0d5
.. section: Tests

Skip some asyncio tests on VxWorks.

..

.. bpo: 42641
.. date: 2020-12-15-17-38-04
.. nonce: uzwlF_
.. section: Tests

Enhance ``test_select.test_select()``: it now takes 500 milliseconds rather than 10
seconds. Use Python rather than a shell to make the test more portable.

..

.. bpo: 31904
.. date: 2020-12-09-15-23-28
.. nonce: ghj38d
.. section: Tests

Skip some tests in _test_all_chown_common() on VxWorks.

..

.. bpo: 42199
.. date: 2020-10-29-21-26-46
.. nonce: KksGCV
.. section: Tests

Fix bytecode helper assertNotInBytecode.

..

.. bpo: 41443
.. date: 2020-07-30-18-43-05
.. nonce: 834gyg
.. section: Tests

Add more attribute checking in test_posix.py

..

.. bpo: 31904
.. date: 2020-07-30-18-06-15
.. nonce: y3d8dk
.. section: Tests

Disable os.popen and impacted tests on VxWorks

..

.. bpo: 41439
.. date: 2020-07-30-14-08-58
.. nonce: yhteoi
.. section: Tests

Port test_ssl and test_uuid to VxWorks RTOS.

..

.. bpo: 42692
.. date: 2021-01-04-05-07-30
.. nonce: OO11SN
.. section: Build

Fix __builtin_available check on older compilers. Patch by Joshua Root.

..

.. bpo: 27640
.. date: 2020-12-22-17-57-04
.. nonce: j3a8r0
.. section: Build

Added ``--disable-test-modules`` option to the ``configure`` script: don't
build nor install test modules. Patch by Xavier de Gaye, Thomas Petazzoni
and Peixing Xin.

..

.. bpo: 42604
.. date: 2020-12-20-02-35-28
.. nonce: gRd89w
.. section: Build

Now all platforms use a value for the "EXT_SUFFIX" build variable derived
from SOABI (for instance in freeBSD, "EXT_SUFFIX" is now ".cpython-310d.so"
instead of ".so"). Previously only Linux, Mac and VxWorks were using a value
for "EXT_SUFFIX" that included "SOABI".

..

.. bpo: 42598
.. date: 2020-12-13-14-43-10
.. nonce: 7ipr5H
.. section: Build

Fix implicit function declarations in configure which could have resulted in
incorrect configuration checks.  Patch contributed by Joshua Root.

..

.. bpo: 31904
.. date: 2020-12-11-18-04-38
.. nonce: j3j6d8
.. section: Build

Enable libpython3.so for VxWorks.

..

.. bpo: 29076
.. date: 2020-02-28-14-33-15
.. nonce: Gtixi5
.. section: Build

Add fish shell support to macOS installer.

..

.. bpo: 42361
.. date: 2021-01-04-01-17-17
.. nonce: eolZAi
.. section: macOS

Update macOS installer build to use Tcl/Tk 8.6.11 (rc2, expected to be final
release).

..

.. bpo: 41837
.. date: 2021-01-04-00-48-08
.. nonce: dX-unJ
.. section: macOS

Update macOS installer build to use OpenSSL 1.1.1i.

..

.. bpo: 42584
.. date: 2020-12-07-11-37-35
.. nonce: LygmqQ
.. section: macOS

Update macOS installer to use SQLite 3.34.0.

..

.. bpo: 42726
.. date: 2020-12-23-19-42-11
.. nonce: a5EkTv
.. section: Tools/Demos

Fixed Python 3 compatibility issue with gdb/libpython.py handling of
attribute dictionaries.

..

.. bpo: 42613
.. date: 2020-12-16-09-10-32
.. nonce: J-jnm5
.. section: Tools/Demos

Fix ``freeze.py`` tool to use the prope config and library directories.
Patch by Victor Stinner.

..

.. bpo: 42591
.. date: 2020-12-10-10-43-03
.. nonce: CXNY8G
.. section: C API

Export the :c:func:`Py_FrozenMain` function: fix a Python 3.9.0 regression.
Python 3.9 uses ``-fvisibility=hidden`` and the function was not exported
explicitly and so not exported.

..

.. bpo: 32381
.. date: 2020-12-09-00-35-25
.. nonce: Je08Ny
.. section: C API

Remove the private :c:func:`!_Py_fopen` function which is no longer needed.
Use :c:func:`!_Py_wfopen` or :c:func:`!_Py_fopen_obj` instead. Patch by Victor
Stinner.

..

.. bpo: 1635741
.. date: 2020-11-22-13-46-06
.. nonce: -fJLzA
.. section: C API

Port :mod:`resource` extension module to module state

..

.. bpo: 42111
.. date: 2020-10-21-18-43-06
.. nonce: 9pvtrc
.. section: C API

Update the ``xxlimited`` module to be a better example of how to use the
limited C API.

..

.. bpo: 40052
.. date: 2020-03-24-09-27-10
.. nonce: 27P2KG
.. section: C API

Fix an alignment build warning/error in function
``PyVectorcall_Function()``. Patch by Andreas Schneider, Antoine Pitrou and
Petr Viktorin.