TypeError: object of type 'types.GenericAlias' has no len()

Question

I have one question, regarding why object of type "~~~" no len()

class testing:
def findrepeatnum(self, nums: list[int]) -> int:
    i = 0
    while i < len(nums):
        if nums[i] == i:
            i += 1
            continue
        if nums[nums[i]] == nums[i]:
            return nums[i]
        nums[nums[i]], nums[i] = nums[i], nums[nums[i]]
    return -1
if __name__ == '__main__':
    num = list[2, 3, 4, 2, 5, 0, 1]
    res = testing().findrepeatnum(num)
    print(res)

This code gives me TypeError: object of type ‘types.GenericAlias’ has no len(). This confuses me for a long time. If I build the function like this:

def findrepeatnum(self, nums: list[int]) -> int:
i = 0
while i < len(nums):
    if nums[i] == i:
        i += 1
        continue
    if nums[nums[i]] == nums[i]:
        return nums[i]
    nums[nums[i]], nums[i] = nums[i], nums[nums[i]]
return -1


if __name__ == '__main__':
    num = list[2, 3, 4, 2, 5, 0, 1]
    res = findrepeatnum(num)
    print(res)

The code gives me TypeError: findrepeatnum() missing 1 required positional argument: ‘nums’ but the nums is already the parameter. I want to know how I can write this correctly.
Thank you very very much!

Asked By: Leong

||

Source

Answer 1

The value of num should be:

num = [2, 3, 4, 2, 5, 0, 1]
# or
num = list([2, 3, 4, 2, 5, 0, 1])

list[int] is used to specify that the values in the list are integer values.
so we cannot use list[] to define a list.

Answered By: Mathan

TypeError: object of type 'types.GenericAlias' has no len()

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