Python D&G快速排序

def quicksort(array):
    if len(array)<2:
        return array #基线条件为空或只包含一个元素
    else:
        pivot = array[0]
        less = [i for i in array[1:] if i<=pivot]
        greater = [i for i in array[1:] if i>pivot]

        return quicksort(less)+[pivot]+quicksort(greater)



print (quicksort([30,20,55,31]))