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gh-86482: Document assignment expression need for ()s #23291

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Merged
merged 8 commits into from
Oct 6, 2022
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gh-86482: Document assignment expression need for ()s #23291

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bpo-42316: Document assignment expression need for ()s
terryjreedy Nov 15, 2020
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terryjreedy Nov 15, 2020
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Merge branch 'main' into walrus
JelleZijlstra Apr 5, 2022
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Merge branch 'main' into walrus
JelleZijlstra Oct 3, 2022
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JelleZijlstra Oct 3, 2022
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Update Doc/reference/expressions.rst
JelleZijlstra Oct 3, 2022
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Update Doc/reference/expressions.rst
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@JelleZijlstra
JelleZijlstra authored Oct 3, 2022
commit a9d94bff2202e97c8f3b1b4bd3ac4c7d7e45e1ee
3 changes: 2 additions & 1 deletion 3 Doc/reference/expressions.rst
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Expand Up @@ -1768,7 +1768,8 @@ Or, when processing a file stream in chunks:

Assignment expressions must be surrounded by parentheses when used
as sub-expressions in slicing, conditional, lambda,
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Unparenthesized assignment expressions in slices were implemented in #23317, so they are allowed since 3.10. Also, assignment expression need to parenthesized in assert and with statements.

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Unparenthesized walruses are allowed in index expressions but not slices. This is current 3.12:

>>> x[y:=3]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'x' is not defined
>>> x[y:=3:z:=4]
  File "<stdin>", line 1
    x[y:=3:z:=4]
          ^
SyntaxError: invalid syntax

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Correct! I mixed up indexes/slices. Sorry!

keyword-argument, and comprehension-if expressions.
keyword-argument, and comprehension-if expressions
and in ``assert`` and ``with`` statements.
In all other places where they can be used, parentheses are not required,
including in ``if`` and ``while`` statements.

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