Aw: Re: mypy question

[Karsten Hilbert]

Hi Greg,

> dict[str, str] is not a subtype of dict[str, str | something_else]
> because you can assign a value of type something_else to the latter
> but not the former.

I understand what you are saying but I do not yet understand why this
applies to my situation.

I don't have Python at hand currently, so I'll write untested pseudocode:

def print_greeting(greeting:int|str):
   print(greeting)

print_greeting('hello')

The above snippet should be equivalent to my more complicated code over
which mypy complains to the equivalent of

   "input" is of type "str"
   but expected type "Union[str,int]

I do understand that "str" is formally more narrow than "Union [str,int]" and
the type system has every right to not consider them equivalent.

However, this seems like a very common use case: "allow passing in either str or int
and have type checking pass either input as valid" -- yet mypy doesn't seem
to share that idea.

Or else there's something I haven't wrapped my head around yet. But what ?

Karsten