Merge Sort on Python

mergeSort.py

import random


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

    l = merge_sort(a[:n//2])
    r = merge_sort(a[n//2:n])

    i = j = 0
    res = []
    while i < len(l) or j < len(r):
        if not i < len(l):
            res.append(r[j])
            j += 1
        elif not j < len(r):
            res.append(l[i])
            i += 1
        elif l[i] < r[j]:
            res.append(l[i])
            i += 1
        else:
            res.append(r[j])
            j += 1

    return res


if __name__ == '__main__':
    A = [random.randint(0, 10) for i in range(10)]

    print(A)
    A = merge_sort(A)
    print(A)