Generic Typing with Iterable[str] or Collection[str]: Should you use it? (feddit.de)

submitted 7 months ago* (last edited 7 months ago) by wasabi@feddit.de to c/python@programming.dev

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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?

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[-] sloppy_diffuser@sh.itjust.works 1 points 7 months ago

Look at the official docs. There is a table part way down stating which methods are available for each. I pick the one closest to how I use it. So if I'm not mutating I'll use Sequence over List to inform the caller I'm treating as immutable and to safe guard myself from mutating it in my implementation via static type analysis.

https://docs.python.org/3/library/collections.abc.html