Doc: Several fixes and improvements for 3.9 whatsnew (GH-16375)
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@ -75,27 +75,27 @@ New Features
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Other Language Changes
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======================
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* :func:`builtins.__import__` now raises :exc:`ImportError` instead of
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:exc:`ValueError` as used to occur when a relative import went past
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* :func:`__import__` now raises :exc:`ImportError` instead of
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:exc:`ValueError`, which used to occur when a relative import went past
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its top-level package.
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(Contributed by Ngalim Siregar in :issue:`37444`.)
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* Python now gets the absolute path of the script filename specified on
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the command line (ex: ``python3 script.py``): the ``__file__`` attribute of
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the ``__main__`` module, ``sys.argv[0]`` and ``sys.path[0]`` become an
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the :mod:`__main__` module, ``sys.argv[0]`` and ``sys.path[0]`` become an
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absolute path, rather than a relative path. These paths now remain valid
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after the current directory is changed by :func:`os.chdir`. As a side effect,
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a traceback also displays the absolute path for ``__main__`` module frames in
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this case.
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a traceback also displays the absolute path for :mod:`__main__` module frames
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in this case.
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(Contributed by Victor Stinner in :issue:`20443`.)
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* In development mode and in debug build, *encoding* and *errors* arguments are
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now checked on string encoding and decoding operations. Examples:
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:func:`open`, :meth:`str.encode` and :meth:`bytes.decode`.
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By default, for best performances, the *errors* argument is only checked at
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the first encoding/decoding error, and the *encoding* argument is sometimes
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By default, for best performance, the *errors* argument is only checked at
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the first encoding/decoding error and the *encoding* argument is sometimes
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ignored for empty strings.
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(Contributed by Victor Stinner in :issue:`37388`.)
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@ -119,15 +119,16 @@ multiline indented output.
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asyncio
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-------
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Added a new couroutine :meth:`loop.shutdown_default_executor` that schedules
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a shutdown for the default executor that waits on the threadpool to finish
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closing. Also, :func:`asyncio.run` has been updated to use the new coroutine.
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Added a new :term:`coroutine` :meth:`~asyncio.loop.shutdown_default_executor`
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that schedules a shutdown for the default executor that waits on the
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:class:`~concurrent.futures.ThreadPoolExecutor` to finish closing. Also,
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:func:`asyncio.run` has been updated to use the new :term:`coroutine`.
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(Contributed by Kyle Stanley in :issue:`34037`.)
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threading
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---------
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In a subinterpreter, spawning a daemon thread now raises an exception. Daemon
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In a subinterpreter, spawning a daemon thread now raises a :exc:`RuntimeError`. Daemon
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threads were never supported in subinterpreters. Previously, the subinterpreter
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finalization crashed with a Python fatal error if a daemon thread was still
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running.
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@ -164,8 +165,8 @@ Optimizations
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Build and C API Changes
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=======================
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* Add a new public :c:func:`PyObject_CallNoArgs` function to the C API:
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call a callable Python object without any arguments. It is the most efficient
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* Add a new public :c:func:`PyObject_CallNoArgs` function to the C API, which
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calls a callable Python object without any arguments. It is the most efficient
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way to call a callable Python object without any argument.
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(Contributed by Victor Stinner in :issue:`37194`.)
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@ -176,18 +177,18 @@ Deprecated
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* Currently :func:`math.factorial` accepts :class:`float` instances with
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non-negative integer values (like ``5.0``). It raises a :exc:`ValueError`
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for non-integral and negative floats. It is deprecated now. In future
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for non-integral and negative floats. It is now deprecated. In future
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Python versions it will raise a :exc:`TypeError` for all floats.
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(Contributed by Serhiy Storchaka in :issue:`37315`.)
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* The :mod:`parser` module is deprecated and will be removed in future versions
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of Python. For the majority of use cases users can leverage the Abstract Syntax
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of Python. For the majority of use cases, users can leverage the Abstract Syntax
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Tree (AST) generation and compilation stage, using the :mod:`ast` module.
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* The :mod:`random` module currently accepts any hashable type as a
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possible seed value. Unfortunately, some of those types are not
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guaranteed to have a deterministic hash value. After Python 3.9,
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the module will restrict its seeds to *None*, :class:`int`,
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the module will restrict its seeds to :const:`None`, :class:`int`,
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:class:`float`, :class:`str`, :class:`bytes`, and :class:`bytearray`.
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@ -195,7 +196,7 @@ Removed
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=======
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* The undocumented ``sys.callstats()`` function has been removed. Since Python
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3.7, it was deprecated and always returned ``None``. It required a special
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3.7, it was deprecated and always returned :const:`None`. It required a special
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build option ``CALL_PROFILE`` which was already removed in Python 3.7.
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(Contributed by Victor Stinner in :issue:`37414`.)
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@ -213,7 +214,7 @@ Removed
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(Contributed by Victor Stinner in :issue:`37312`.)
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* ``aifc.openfp()`` alias to ``aifc.open()``, ``sunau.openfp()`` alias to
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``sunau.open()``, and ``wave.openfp()`` alias to ``wave.open()`` have been
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``sunau.open()``, and ``wave.openfp()`` alias to :func:`wave.open()` have been
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removed. They were deprecated since Python 3.7.
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(Contributed by Victor Stinner in :issue:`37320`.)
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@ -229,16 +230,16 @@ Removed
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(Contributed by Serhiy Storchaka in :issue:`36543`.)
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* The old :mod:`plistlib` API has been removed, it was deprecated since Python
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3.4. Use the :func:`load`, :func:`loads`, :func:`dump`, and :func:`dumps`
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functions. Additionally, the ``use_builtin_types`` parameter was removed,
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standard :class:`bytes` objects are always used.
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3.4. Use the :func:`~plistlib.load`, :func:`~plistlib.loads`, :func:`~plistlib.dump`, and
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:func:`~plistlib.dumps` functions. Additionally, the *use_builtin_types* parameter was
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removed, standard :class:`bytes` objects are always used instead.
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(Contributed by Jon Janzen in :issue:`36409`.)
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* ``PyThreadState_DeleteCurrent()`` has been removed. It was not documented.
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* The C function ``PyThreadState_DeleteCurrent()`` has been removed. It was not documented.
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(Contributed by Joannah Nanjekye in :issue:`37878`.)
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* The C function ``PyGen_NeedsFinalizing`` has been removed. It was not
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documented, tested or used anywhere within CPython after the implementation
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documented, tested, or used anywhere within CPython after the implementation
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of :pep:`442`. Patch by Joannah Nanjekye.
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(Contributed by Joannah Nanjekye in :issue:`15088`)
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@ -253,11 +254,10 @@ that may require changes to your code.
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Changes in the Python API
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-------------------------
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* :func:`builtins.__import__` and :func:`importlib.util.resolve_name` now raise
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* :func:`__import__` and :func:`importlib.util.resolve_name` now raise
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:exc:`ImportError` where it previously raised :exc:`ValueError`. Callers
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catching the specific exception type and supporting both Python 3.9 and
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earlier versions will need to catch both:
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``except (ImportError, ValueError):``
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earlier versions will need to catch both using ``except (ImportError, ValueError):``.
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* The :mod:`venv` activation scripts no longer special-case when
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``__VENV_PROMPT__`` is set to ``""``.
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