Merge sort python 3

Question

I implemented such merge sorting algorithm, hoverer I got some issues

import sys

if __name__ == '__main__':
        input = sys.stdin.read()
        data = list(map(int, input.split()))
        n = data[0]
        a = data[1:]
        print(merge_sort(a))

def merge(left,rigt):
    result = []
    i = j = 0
    while i < len(left) and j < len(rigt):
        if left[i] <= rigt[j]:
            result.append(left[i])
            i += 1

        else:
            result.append(rigt[j])
            j += 1

    result += left[i:]
    result += rigt[j:]

    return result

def merge_sort(a):
    if len(a) <= 2:
        return 1

    middle = len(a)//2

    left = a[:middle]
    right = a[middle:]

    left = merge_sort(left)
    right = merge_sort(right)

    return list(merge(left,right))

I got such error

TypeError: object of type 'int' has no len()

I can't understand, where I went wrong, why program thinks that "left" and "right" are int, however it is array.

Answer 1

You should replace

if len(a) <= 2:
    return 1

with

if len(a) == 1:
    return a

to return a list which is not partitionable.

Answer 2

您忘记了merge_sort函数的终止情况，该情况返回1。因此，当递归到达底部时，left和rigt都为int，因此您需要在代码中加以考虑。