python quicksort

quicksort.py

def quick_sort(array):
    def partition(array, start, end):
        i = start - 1  # i represent the last index of smaller set
        pivot = end - 1
        # j represent the working pointer
        for j in range(start, end - 1):
            # swap
            if array[j] < array[pivot]:
                i += 1
                tmp = array[j]
                array[j] = array[i]
                array[i] = tmp
        tmp = array[pivot]
        array[pivot] = array[i + 1]
        array[i + 1] = tmp
        return i + 1

    def _quick_sort(array, start, end):
        if end - start <= 1:
            return
        if end - start == 2:
            if array[start] > array[end - 1]:
                tmp = array[start]
                array[start] = array[end - 1]
                array[end - 1] = tmp
            return
        divide = partition(array, start, end)
        if divide == end or divide == start:
            return
        _quick_sort(array, start, divide)
        _quick_sort(array, divide, end)
        return

    _quick_sort(array, 0, len(array))
    return array