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bpo-10544: Disallow "yield" in comprehensions and generator expressions. (GH-4564)

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Serhiy Storchaka 2018-02-04 10:53:48 +02:00 • committed by GitHub
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Doc/reference/expressions.rst
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@ -196,8 +196,7 @@ they may depend on the values obtained from the leftmost iterable. For example:
To ensure the comprehension always results in a container of the appropriate
type, ``yield`` and ``yield from`` expressions are prohibited in the implicitly
nested scope (in Python 3.7, such expressions emit :exc:`DeprecationWarning`
when compiled, in Python 3.8+ they will emit :exc:`SyntaxError`).
nested scope.
Since Python 3.6, in an :keyword:`async def` function, an :keyword:`async for`
clause may be used to iterate over a :term:`asynchronous iterator`.
@ -214,8 +213,8 @@ See also :pep:`530`.
.. versionadded:: 3.6
Asynchronous comprehensions were introduced.
.. deprecated:: 3.7
``yield`` and ``yield from`` deprecated in the implicitly nested scope.
.. versionchanged:: 3.8
``yield`` and ``yield from`` prohibited in the implicitly nested scope.
.. _lists:
@ -350,9 +349,7 @@ The parentheses can be omitted on calls with only one argument. See section
To avoid interfering with the expected operation of the generator expression
itself, ``yield`` and ``yield from`` expressions are prohibited in the
implicitly defined generator (in Python 3.7, such expressions emit
:exc:`DeprecationWarning` when compiled, in Python 3.8+ they will emit
:exc:`SyntaxError`).
implicitly defined generator.
If a generator expression contains either :keyword:`async for`
clauses or :keyword:`await` expressions it is called an
@ -368,8 +365,8 @@ which is an asynchronous iterator (see :ref:`async-iterators`).
only appear in :keyword:`async def` coroutines. Starting
with 3.7, any function can use asynchronous generator expressions.
.. deprecated:: 3.7
``yield`` and ``yield from`` deprecated in the implicitly nested scope.
.. versionchanged:: 3.8
``yield`` and ``yield from`` prohibited in the implicitly nested scope.
.. _yieldexpr:
@ -401,12 +398,10 @@ coroutine function to be an asynchronous generator. For example::
Due to their side effects on the containing scope, ``yield`` expressions
are not permitted as part of the implicitly defined scopes used to
implement comprehensions and generator expressions (in Python 3.7, such
expressions emit :exc:`DeprecationWarning` when compiled, in Python 3.8+
they will emit :exc:`SyntaxError`)..
implement comprehensions and generator expressions.
.. deprecated:: 3.7
Yield expressions deprecated in the implicitly nested scopes used to
.. versionchanged:: 3.8
Yield expressions prohibited in the implicitly nested scopes used to
implement comprehensions and generator expressions.
Generator functions are described below, while asynchronous generator