Merge sort integer array in python

merge_sort.py

source = [11, 8, 3, 9, 7, 1, 2, 5, 13, 6, 8]


def merge(left, right):
    temp = [0] * (len(left) + len(right))
    idx_l = 0
    idx_r = 0
    for i in range(len(temp)):
        if idx_l >= len(left):
            for k in range(i, i + len(right) - idx_r):
                temp[k] = right[idx_r]
                idx_r += 1
            break

        if idx_r >= len(right):
            for k in range(i, i + len(left) - idx_l):
                temp[k] = left[idx_l]
                idx_l += 1
            break
        if left[idx_l] < right[idx_r]:
            temp[i] = left[idx_l]
            idx_l += 1
        else:
            temp[i] = right[idx_r]
            idx_r += 1
    return temp


def merge_sort(source):
    n = len(source)
    if n == 1:
        return source
    if n == 2:
        if source[0] > source[1]:
            source[0], source[1] = source[1], source[0]
            return source
        else:
            return source
    mid = int(n / 2)
    return merge(merge_sort(source[:mid]), merge_sort(source[mid:]))


result = merge_sort(source)

print('result = ', result)