How can I typehint that something should have the same type as earlier?
def mymap(xs: [T], func: T -> V): -> [V]:
return [func(x) for x in xs]
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theonlygusti
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1`def mymap(xs: Iterable[T], func: Callable[[T], V]) -> list[V]: ...` should work? what have you tried? – anthony sottile Jan 16 '22 at 23:46
1 Answers
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You can do this with TypeVar
from typing import Callable, List, TypeVar
T = TypeVar('T')
V = TypeVar('V')
def mymap(items: List[T], fn: Callable[[T], V]) -> List[V]:
return [fn(e) for e in items]
kingkupps
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It depends on what `items` really is and which version of Python you're using. You should definitely use `Callable` but `List` could be replaced by `Set` or `Dict` for example. If you're using (I think) Python 3.9+ you can use `list` directly instead of `typing.List`. – kingkupps Jan 17 '22 at 16:33