Insertion Sort implementation in Python

insertion_sort.py

def insertion_sort(array, decrescent=False):
    if len(array) <= 1:
        return array
    for x in range(1, len(array)):
        y = x
        while y > 0 and ((decrescent and array[y] > array[y - 1]) or
                         (not decrescent and array[y] < array[y - 1])):
            array[y], array[y - 1] = array[y - 1], array[y]
            y = y - 1
    return array