[issue44223] := in comprehensions does not work

[Dennis Sweeney]

Dennis Sweeney <sweeney.dennis650 at gmail.com> added the comment:

The parser rejects this ambiguity and requires parentheses:
[
    xxx
    for item in collection
    if (xxx := mutator(item)) is not None
]

Example ambiguity:

>>> [x for item in "abcdefabc" if x := item.upper() not in "ABC"]
SyntaxError: invalid syntax
>>> [x for item in "abcdefabc" if (x := item.upper()) not in "ABC"]
['D', 'E', 'F']
>>> [x for item in "abcdefabc" if (x := item.upper() not in "ABC")]
[True, True, True]
>>>

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nosy: +Dennis Sweeney

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue44223>
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