python 快速排序算法

def sort(start, end, li):
    if start < end:
        i = start
        j = end
        base = li[i]
        while i < j:
            while i < j and li[j] >= base:
                j -= 1
            li[i], li[j] = li[j], li[i]
            while i<j and li[i] < base:
                i += 1
            li[i], li[j] = li[j], li[i]
        sort(start, i-1, li)
        sort(i+1, end, li)
    return

def quicksort(li):
    start = 0
    end = len(li) - 1
    sort(start, end, li)
    return