问TypeError:当求和矩阵对角线时，“int”对象不可调用

EN

    Traceback (most recent call last):

  File "C:\Users\AppData\Local\Temp/ipykernel_18232/558242258.py", line 1, in <module>
    diagonalDifference(arr)

  File "C:\Users\AppData\Local\Temp/ipykernel_18232/2138727441.py", line 3, in diagonalDifference
    m = sum([arr[i][i] for i in range(n)])

TypeError: 'int' object is not callable


n = int(input().strip()) # n for n*n mat
arr = []
for _ in range(n):
   arr.append(list(map(int, input().rstrip().split())))  #takes n times inputs, each time n space separated integer

def diagonalDifference(arr):
        n = len(arr)
        m = sum([arr[i][i] for i in range(n)])
        o = sum([arr[i][n-i-1] for i in range(n)])
        return abs(m-o)