“TypeError: ‘type’ object is not subscriptable” in a function signature

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The following answer only applies to Python < 3.9

The expression list[int] is attempting to subscript the object list, which is a class. Class objects are of the type of their metaclass, which is type in this case. Since type does not define a __getitem__ method, you can’t do list[...].

To do this correctly, you need to import typing.List and use that instead of the built-in list in your type hints:

from typing import List

...


def twoSum(self, nums: List[int], target: int) -> List[int]:

If you want to avoid the extra import, you can simplify the type hints to exclude generics:

def twoSum(self, nums: list, target: int) -> list:

Alternatively, you can get rid of type hinting completely:

def twoSum(self, nums, target):

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