Quick sort algorithm

quicksort.py

def quicksort(arr):
    if len(arr) == 1:
        return arr
    if len(arr) == 0:
        return []

    pivot = arr[-1]
    left = []
    right = []

    for a in arr[:-1]:
        if a > pivot:
            right.append(a)
        else:
            left.append(a)

    left = quicksort(left)
    right = quicksort(right)

    return left+[pivot]+right


arr = [5, 2, 4, 3, 1, 8, 7, 9]