quick_sort

import random

def quick_sort(myList, start=None, end=None):
    if start is None:
        start = 0
        end = len(myList)
    if start + 1 >= end:
        return

    pivot_ind = random.randint(start, end-1)
    pivot_val = myList[pivot_ind]

    myList[start], myList[pivot_ind] = myList[pivot_ind], myList[start]

    j = start + 1           # put here elements greater than pivot
    k = start + 1           # put here elements equal to pivot
    for i in range(start+1, end):
        if myList[i] < pivot_val :
            myList[i], myList[j] = myList[j], myList[i]
            j += 1
        if myList[i] == pivot_val :
            myList[i], myList[j] = myList[j], myList[i]
            myList[j], myList[k] = myList[k], myList[j]
            k += 1
            j += 1

    for n in range(start, k):
         myList[n], myList[j-1-(n-start)] = myList[j-1-(n-start)], myList[n]

    quick_sort(myList, start, j -(k-start) )
    quick_sort(myList, j, end)