Merge sort in Python

merge_sort.py

import random

my_randoms = random.sample(xrange(100), 13)


def merge(first_half, second_half):
    if len(first_half) == 0:
        return second_half
    elif len(second_half) == 0:
        return first_half
    elif first_half[0] < second_half[0]:
        return [first_half[0]] + merge(first_half[1:], second_half)
    else:
        return [second_half[0]] + merge(first_half, second_half[1:])


# Average: O(n log(n))
def merge_sort(items):
    if len(items) < 2:
        return items
    else:
        pivot_point = len(items) / 2
        return merge(
            merge_sort(items[:pivot_point]),
            merge_sort(items[pivot_point:]))


print merge_sort(my_randoms)