CODEWITHSUNDEEP
pythonpython-3.x
David542
David542

Reputation: 110482

Type hinting on multi-type

If I have the following function:

def pops(L: list, default=None):
    "Pop from the left of the list, or return the default."
    return L.pop(0) if L else default

What would be the proper way to add type-hints for this? L is a list -- I know that (though of what I have no idea). But default could be anything -- and by extension, the output could be anything as well. What would be the best way to do this?

Examples:

>>> pops([1,2,3,4])
# 1
>>> pops(['1'])
# '1'
>>> pops([], {})
# {}
>>> pops([], None)
# None

Upvotes: 0

Views: 73

Answers (1)

Green Cloak Guy
Green Cloak Guy

Reputation: 24711

Use a TypeVar.

from typing import List, Union, TypeVar

T = TypeVar('T')
K = TypeVar('K')
def pops(L: List[T], default: K = None) -> Union[T, K, None]:
    "Pop from the left of the list, or return the default."
    return L.pop(0) if L else default

Upvotes: 2

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