Why doesn't mypy pass when TypedDict calls update method

Question

Example:

from typing import TypedDict

class MyType(TypedDict):
    a: int
    b: int

t = MyType(a=1, b=2)

t.update(b=3)

mypy toy.py complains

toy.py:9:1: error: Unexpected keyword argument "b" for "update" of "TypedDict"
Found 1 error in 1 file (checked 1 source file)

hmm... I haven't touched mypy before, but how does `t |= dict(b=3)` work? — rv.kvetch, Oct 21 '21 at 21:54

score 6 · Accepted Answer · answered Oct 21 '21 at 23:12

6

It appears this is a known open issue for mypy: https://github.com/python/mypy/issues/6019

For now if you want mypy to not bother you with this error, you'll need to tell it to ignore it:

t.update(b=3)  # type: ignore[call-arg]

answered Oct 21 '21 at 23:12

Da Chucky

4

Or (similarly in the meantime) supply a dict or tuple instead of a keyword, I suppose. – CrazyChucky Oct 21 '21 at 23:17
3

Indeed, `mypy` does not complain about `t.update({"b": 3})` – Da Chucky Oct 21 '21 at 23:23

1 Answers1