Quicksort with Python

quicksort.py

def quicksort(a, p, r):
    if p < r:
        q = partition(a, p, r)
        quicksort(a, p, q - 1)
        quicksort(a, q + 1, r)


def partition(a, p, r):
    x = a[r]
    i = p - 1
    for j in range(p, r):
        if a[j] <= x:
            i += 1
            a[i], a[j] = a[j], a[i]
    a[i + 1], a[r] = a[r], a[i + 1]
    return i + 1

if __name__ == '__main__':
    a = [11, 67, 23, 5, 101, 19, 41, 90, 2, 44, 1]
    quicksort(a, 0, len(a) - 1)
    print(a)