Should not throw "Value of type "Optional[Match[str]]" is not indexable" error when using Assignment expressions

[dongweiming]

I ’m not sure if it ’s mypy or typeshed issue.

I found an issue about this, here is a short example using Assignment expressions, it will throw an error:

❯ cat a.py 
import re

if (m := re.search(".", "foo")):
    print(m[0])

❯ mypy a.py 
a.py:4: error: Value of type "Optional[Match[str]]" is not indexable
        print(m[0])
              ^
Found 1 error in 1 file (checked 1 source file)

[TH3CHARLie]

It is a mypy issue, related #7316

As a workaround, use:

import re
m = re.search(".", "foo)
if m:
    print(m[0])

[JelleZijlstra]

Yes, this is a duplicate of #7316.