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Walrus operators unrecognised in dictionary initialisation of a class attribute #8379
Description
It seems Walrus operators (in Python 3.8+) are not recognised by mypy when used in initialising a dictionary of a class attribute. Here is a test code.
class TryWalrus:
CKEY = {
'KY': (p:='a_'),
'ANOTHER': p+'content',
}
print(TryWalrus.CKEY['ANOTHER']) # => a_contentThis outputs the following:
$ mypy try_walrus.py
try_walrus.py:4: error: Name 'p' is not defined
Found 1 error in 1 file (checked 1 source file)
If the variable CKEY is out of the class definition, i.e. if directly in Main, it does not raise an error.
I tested it with Python 3.8.1 and mypy version 0.770+dev.8888b1aedf6d4ba543ae12f538f190ce5e65c20d (yesterday's head).
Activity
dhood commentedon Jul 5, 2020
This will also happen with a list e.g.
l = [x2 := 1, x2 + 2, x2 + 3](for this case also it will only happen if it is in the class scope).I have noticed, however, that it only happens on RE-USE of the variable from the assignment expression within the initialisation. Otherwise the walrus operator is ok.
bunny-therapist commentedon Aug 19, 2023
I just (2023) ran into this exact problem with
it176131 commentedon May 28, 2024
Any proposed fix—besides
# type: ignore[name-defined]—for this? I ran into it with the following versions:JelleZijlstra commentedon May 28, 2024
Anyone impacted should feel free to work on a PR to fix this. I haven't looked at the code but I imagine it's a relatively easy fix.