bpo-37759: More updates to Whatsnew 3.8 (GH-16854)
* math.perm() and math.comb() * math.isqrt() * Add singledispatchmethod() * itertools.accumulate() * Optional headers for xmlrpc.client.ServerProxy * IDLE non-BMP characters * import collections.abc directly * @coroutine is deprecated * pprint.pp() * New options for object.__reduce__() * DictReader no longer returns OrderedDicts * "force" option for logging.basicConfig() * Fix spelling * cProfile context manager * Various markup/grammar fixes from Kyle Stanley. Other minor fixes as well. Also, dedup the __reduce__ entry. * Fix markup * Fix grammar nits found by MS Word
This commit is contained in:
Raymond Hettinger
GitHub
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c93883c6af
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@ -355,8 +355,8 @@ It is meant to formalize existing optimizations which were already done
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for various classes.
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Any extension type implementing a callable can use this protocol.
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This is currently provisional,
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the aim is to make it fully public in Python 3.9.
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This is currently provisional.
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The aim is to make it fully public in Python 3.9.
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See :pep:`590` for a full description.
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@ -445,7 +445,7 @@ Other Language Changes
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an instance of the subclass, rather than the base class. This also affects
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the return type of operations whose implementation (directly or indirectly)
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uses :class:`datetime.timedelta` arithmetic, such as
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:meth:`datetime.datetime.astimezone`.
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:meth:`~datetime.datetime.astimezone`.
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(Contributed by Paul Ganssle in :issue:`32417`.)
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* When the Python interpreter is interrupted by Ctrl-C (SIGINT) and the
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@ -529,6 +529,13 @@ Other Language Changes
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(Contributed by Jörn Heissler in :issue:`35224`.)
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* The :meth:`object.__reduce__` method can now return a tuple from two to
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six elements long. Formerly, five was the limit. The new, optional sixth
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element is a callable with a ``(obj, state)`` signature. This allows the
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direct control over the state-updating behavior of a specific object. If
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not *None*, this callable will have priority over the object's
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:meth:`~__setstate__` method.
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(Contributed by Pierre Glaser and Olivier Grisel in :issue:`35900`.)
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New Modules
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===========
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@ -579,8 +586,8 @@ The :func:`ast.parse` function has some new flags:
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comments" (returned for function definition AST nodes);
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* ``feature_version=(3, N)`` allows specifying an earlier Python 3
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version. (For example, ``feature_version=(3, 4)`` will treat
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``async`` and ``await`` as non-reserved words.)
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version. For example, ``feature_version=(3, 4)`` will treat
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:keyword:`async` and :keyword:`await` as non-reserved words.
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(Contributed by Guido van Rossum in :issue:`35766`.)
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@ -630,14 +637,39 @@ marked with the ``CO_COROUTINE`` flag may then be returned.
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collections
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-----------
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The :meth:`_asdict()` method for :func:`collections.namedtuple` now returns
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a :class:`dict` instead of a :class:`collections.OrderedDict`. This works because
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regular dicts have guaranteed ordering since Python 3.7. If the extra
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features of :class:`OrderedDict` are required, the suggested remediation is
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to cast the result to the desired type: ``OrderedDict(nt._asdict())``.
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The :meth:`~collections.somenamedtuple._asdict` method for
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:func:`collections.namedtuple` now returns a :class:`dict` instead of a
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:class:`collections.OrderedDict`. This works because regular dicts have
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guaranteed ordering since Python 3.7. If the extra features of
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:class:`OrderedDict` are required, the suggested remediation is to cast the
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result to the desired type: ``OrderedDict(nt._asdict())``.
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(Contributed by Raymond Hettinger in :issue:`35864`.)
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cProfile
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--------
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The :class:`cProfile.Profile <profile.Profile>` class can now be used as a context manager.
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Profile a block of code by running::
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import cProfile
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with cProfile.Profile() as profiler:
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# code to be profiled
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...
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(Contributed by Scott Sanderson in :issue:`29235`.)
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csv
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---
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The :class:`csv.DictReader` now returns instances of :class:`dict` instead of
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a :class:`collections.OrderedDict`. The tool is now faster and uses less
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memory while still preserving the field order.
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(Contributed by Michael Seek in :issue:`34003`.)
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curses
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-------
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@ -700,6 +732,30 @@ cached for the life of the instance. ::
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(Contributed by Carl Meyer in :issue:`21145`)
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Added a new :func:`functools.singledispatchmethod` decorator that converts
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methods into :term:`generic functions <generic function>` using
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:term:`single dispatch`::
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from functools import singledispatchmethod
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from contextlib import suppress
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class TaskManager:
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def __init__(self, tasks):
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self.tasks = list(tasks)
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@singledispatchmethod
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def discard(self, value):
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with suppress(ValueError):
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self.tasks.remove(value)
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@discard.register(list)
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def _(self, tasks):
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targets = set(tasks)
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self.tasks = [x for x in self.tasks if x not in targets]
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(Contributed by Ethan Smith in :issue:`32380`)
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gc
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--
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@ -727,7 +783,7 @@ for certain types of invalid or corrupt gzip files.
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:issue:`6584`.)
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idlelib and IDLE
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IDLE and idlelib
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----------------
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Output over N lines (50 by default) is squeezed down to a button.
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@ -743,12 +799,19 @@ They also re-appear in the box for the next customized run. One can also
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suppress the normal Shell main module restart. (Contributed by Cheryl
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Sabella, Terry Jan Reedy, and others in :issue:`5680` and :issue:`37627`.)
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Add optional line numbers for IDLE editor windows. Windows
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Added optional line numbers for IDLE editor windows. Windows
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open without line numbers unless set otherwise in the General
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tab of the configuration dialog. Line numbers for an existing
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window are shown and hidden in the Options menu.
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(Contributed by Tal Einat and Saimadhav Heblikar in :issue:`17535`.)
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OS native encoding is now used for converting between Python strings and Tcl
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objects. This allows IDLE to work with emoji and other non-BMP characters.
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These characters can be displayed or copied and pasted to or from the
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clipboard. Converting strings from Tcl to Python and back now never fails.
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(Many people worked on this for eight years but the problem was finally
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solved by Serhiy Storchaka in :issue:`13153`.)
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The changes above have been backported to 3.7 maintenance releases.
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@ -779,13 +842,44 @@ fails. The exception is ignored silently by default in release build.
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(Contributed by Victor Stinner in :issue:`18748`.)
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itertools
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---------
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The :func:`itertools.accumulate` function added an option *initial* keyword
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argument to specify an initial value::
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>>> from itertools import accumulate
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>>> list(accumulate([10, 5, 30, 15], initial=1000))
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[1000, 1010, 1015, 1045, 1060]
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(Contributed by Lisa Roach in :issue:`34659`.)
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json.tool
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---------
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Add option ``--json-lines`` to parse every input line as separate JSON object.
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Add option ``--json-lines`` to parse every input line as a separate JSON object.
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(Contributed by Weipeng Hong in :issue:`31553`.)
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logging
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-------
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Added a *force* keyword argument to :func:`logging.basicConfig()`
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When set to *True*, any existing handlers attached
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to the root logger are removed and closed before carrying out the
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configuration specified by the other arguments.
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This solves a long-standing problem. Once a logger or *basicConfig()* had
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been called, subsequent calls to *basicConfig()* were silently ignored.
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This made it difficult to update, experiment with, or teach the various
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logging configuration options using the interactive prompt or a Jupyter
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notebook.
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(Suggested by Raymond Hettinger, implemented by Dong-hee Na, and
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reviewed by Vinay Sajip in :issue:`33897`.)
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math
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----
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@ -807,7 +901,28 @@ numbers::
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(Contributed by Pablo Galindo in :issue:`35606`.)
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Added new function :func:`math.isqrt` for computing integer square roots.
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Added two new combinatoric functions :func:`math.perm` and :func:`math.comb`::
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>>> math.perm(10, 3) # Permutations of 10 things taken 3 at a time
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720
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>>> math.comb(10, 3) # Combinations of 10 things taken 3 at a time
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120
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(Contributed by Yash Aggarwal, Keller Fuchs, Serhiy Storchaka, and Raymond
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Hettinger in :issue:`37128`, :issue:`37178`, and :issue:`35431`.)
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Added a new function :func:`math.isqrt` for computing accurate integer square
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roots without conversion to floating point. The new function supports
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arbitrarily large integers. It is faster than ``floor(sqrt(n))`` but slower
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than :func:`math.sqrt`::
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>>> r = 650320427
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>>> s = r ** 2
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>>> isqrt(s - 1) # correct
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650320426
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>>> floor(sqrt(s - 1)) # incorrect
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650320427
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(Contributed by Mark Dickinson in :issue:`36887`.)
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The function :func:`math.factorial` no longer accepts arguments that are not
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@ -908,11 +1023,6 @@ to a path.
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pickle
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------
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Reduction methods can now include a 6th item in the tuple they return. This
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item should specify a custom state-setting method that's called instead of the
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regular ``__setstate__`` method.
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(Contributed by Pierre Glaser and Olivier Grisel in :issue:`35900`.)
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:mod:`pickle` extensions subclassing the C-optimized :class:`~pickle.Pickler`
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can now override the pickling logic of functions and classes by defining the
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special :meth:`~pickle.Pickler.reducer_override` method.
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@ -927,6 +1037,32 @@ NSKeyedArchiver-encoded binary plists.
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(Contributed by Jon Janzen in :issue:`26707`.)
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pprint
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------
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The :mod:`pprint` module added a *sort_dicts* parameter to several functions.
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By default, those functions continue to sort dictionaries before rendering or
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printing. However, if *sort_dicts* is set to *False*, the dictionaries retain
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the order that keys were inserted. This can be useful for comparison to JSON
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inputs during debugging.
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In addition, there is a convenience new function, :func:`pprint.pp` that is
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like :func:`pprint.pprint` but with *sort_dicts* defaulting to *False*::
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>>> from pprint import pprint, pp
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>>> d = dict(source='input.txt', operation='filter', destination='output.txt')
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>>> pp(d, width=40) # Original order
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{'source': 'input.txt',
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'operation': 'filter',
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'destination': 'output.txt'}
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>>> pprint(d, width=40) # Keys sorted alphabetically
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{'destination': 'output.txt',
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'operation': 'filter',
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'source': 'input.txt'}
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(Contributed by Rémi Lapeyre in :issue:`30670`.)
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py_compile
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----------
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@ -973,8 +1109,8 @@ The :func:`socket.if_nameindex()`, :func:`socket.if_nametoindex()`, and
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ssl
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---
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Added :attr:`ssl.SSLContext.post_handshake_auth` to enable and
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:meth:`ssl.SSLSocket.verify_client_post_handshake` to initiate TLS 1.3
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Added :attr:`~ssl.SSLContext.post_handshake_auth` to enable and
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:meth:`~ssl.SSLSocket.verify_client_post_handshake` to initiate TLS 1.3
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post-handshake authentication.
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(Contributed by Christian Heimes in :issue:`34670`.)
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@ -1152,8 +1288,9 @@ the string. (Contributed by Max Belanger, David Euresti, and Greg Price in
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unittest
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--------
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Added :class:`AsyncMock` to support an asynchronous version of :class:`Mock`.
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Appropriate new assert functions for testing have been added as well.
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Added :class:`~unittest.mock.AsyncMock` to support an asynchronous version of
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:class:`~unittest.mock.Mock`. Appropriate new assert functions for testing
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have been added as well.
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(Contributed by Lisa Roach in :issue:`26467`).
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Added :func:`~unittest.addModuleCleanup()` and
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@ -1233,6 +1370,16 @@ them in the generated tree.
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(Contributed by Stefan Behnel in :issue:`36676` and :issue:`36673`.)
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xmlrpc
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------
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:class:`xmlrpc.client.ServerProxy` now supports an optional *headers* keyword
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argument for a sequence of HTTP headers to be sent with each request. Among
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other things, this makes it possible to upgrade from default basic
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authentication to faster session authentication.
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(Contributed by Cédric Krier in :issue:`35153`.)
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Optimizations
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=============
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@ -1456,6 +1603,11 @@ Deprecated
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constant nodes.
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(Contributed by Serhiy Storchaka in :issue:`36917`.)
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* The :func:`asyncio.coroutine` :term:`decorator` is deprecated and will be
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removed in version 3.10. Instead of ``@asyncio.coroutine``, use
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:keyword:`async def` instead.
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(Contributed by Andrew Svetlov in :issue:`36921`.)
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* The following functions and methods are deprecated in the :mod:`gettext`
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module: :func:`~gettext.lgettext`, :func:`~gettext.ldgettext`,
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:func:`~gettext.lngettext` and :func:`~gettext.ldngettext`.
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@ -1502,7 +1654,7 @@ Deprecated
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:class:`multiprocessing.managers.SharedMemoryServer`.
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- *obj* in :func:`weakref.finalize`.
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In future releases of Python they will be :ref:`positional-only
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In future releases of Python, they will be :ref:`positional-only
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<positional-only_parameter>`.
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(Contributed by Serhiy Storchaka in :issue:`36492`.)
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@ -1512,6 +1664,11 @@ API and Feature Removals
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The following features and APIs have been removed from Python 3.8:
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* Starting with Python 3.3, importing ABCs from :mod:`collections` was
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deprecated, and importing should be done from :mod:`collections.abc`. Being
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able to import from collections was marked for removal in 3.8, but has been
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delayed to 3.9. (See :issue:`36952`.)
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* The :mod:`macpath` module, deprecated in Python 3.7, has been removed.
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(Contributed by Victor Stinner in :issue:`35471`.)
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@ -1630,7 +1787,7 @@ Changes in the Python API
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(Contributed by Eric Snow in :issue:`34651`, modified by Christian Heimes
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in :issue:`37951`.)
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* The :meth:`imap.IMAP4.logout` method no longer ignores silently arbitrary
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* The :meth:`imap.IMAP4.logout` method no longer silently ignores arbitrary
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exceptions.
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(Contributed by Victor Stinner in :issue:`36348`.)
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@ -1685,7 +1842,7 @@ Changes in the Python API
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* The ``PyGC_Head`` struct has changed completely. All code that touched the
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struct member should be rewritten. (See :issue:`33597`.)
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* The ``PyInterpreterState`` struct has been moved into the "internal"
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* The :c:type:`PyInterpreterState` struct has been moved into the "internal"
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header files (specifically Include/internal/pycore_pystate.h). An
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opaque ``PyInterpreterState`` is still available as part of the public
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API (and stable ABI). The docs indicate that none of the struct's
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