"TypeError: 'type' object is not subscriptable" in a function signature

Why am I receiving this error when I run this code?

Traceback (most recent call last):                                                                                                                                                  
  File "", line 13, in <module>                                                                                                                                              
    def twoSum(self, nums: list[int], target: int) -> list[int]:                                                                                                                    
TypeError: 'type' object is not subscriptable
nums = [4,5,6,7,8,9]
target = 13

def twoSum(self, nums: list[int], target: int) -> list[int]:
        dictionary = {}
        answer = []
        for i in range(len(nums)):
            secondNumber = target-nums[i]
            if(secondNumber in dictionary.keys()):
                secondIndex = nums.index(secondNumber)
                if(i != secondIndex):
                    return sorted([i, secondIndex])
            dictionary.update({nums[i]: i})

print(twoSum(nums, target))


  • 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):