Insertion sort in Python

isort.py

def insertion_sort(keys):
    index = 1
    while index < len(keys):
        key = keys[index]
        comp_index = index - 1
        while comp_index >= 0 and key < keys[comp_index]:
            keys[comp_index], keys[comp_index+1] = keys[comp_index+1], keys[comp_index]
            comp_index -= 1
        index += 1