I often find myself defining function args with list[SomeClass] type and think “do I really care that it’s a list? No, tuple or Generator is fine, too”. I then tend to use Iterable[SomeClass] or Collection[SomeClass]. But when it comes to str, I really don’t like that solution, because if you have this function:

def foo(bar: Collection[str]) -> None:
    pass

Then calling foo("hello") is fine, too, because “hello” is a collection of strings with length 1, which would not be fine if I just used list[str] in the first place. What would you do in a situation like this?

  • 𝕨𝕒𝕤𝕒𝕓𝕚@feddit.deOPEnglish
    3·
    9 months ago

    I know that Iterable and Collection aren’t the same. My point is, that if you use Iterable[str] or Collection[str] as a more flexible alternative to list[str] you no longer have any type-hinting support protecting against passing in a plain string and you could end up with a subtle bug by unexpectedly looping over ['f', 'o', 'o'] instead of ['foo'].