Python Merge Sort

gistfile1.py

import random


def merge(left_arr, right_arr):
    """
    Receives two ordered lists and returns a ordered
    list created from the merge of the other two.
    :param left_arr: ordered list
    :param right_arr: ordered list
    :return: ordered list created from the merge of left_arr and right_arr
    """
    result = []
    lc, rc = 0, 0
    while lc < len(left_arr) and rc < len(right_arr):
        if left_arr[lc] <= right_arr[rc]:
            result.append(left_arr[lc])
            lc += 1
        else:
            result.append(right_arr[rc])
            rc += 1
    while lc < len(left_arr):
        result.append(left_arr[lc])
        lc += 1
    while rc < len(right_arr):
        result.append(right_arr[rc])
        rc += 1
    return result


def merge_sort(unordered_list):
    if len(unordered_list) <= 1:
        return unordered_list
    else:
        left_array = unordered_list[:len(unordered_list)/2]
        right_array = unordered_list[len(unordered_list)/2:]
        left_array = merge_sort(left_array)
        right_array = merge_sort(right_array)
        unordered_list = merge(left_array, right_array)
    return unordered_list


arr = random.sample(range(1000), 10)
print arr

print merge_sort(arr)