Quicksort algorithm Python error

Question

I am trying to implement Quicksort using Python. This is my code:

import random

def quickSort(lst):
    randomIndex = random.randint(0,len(lst)-1)
    pivot = lst[randomIndex]
    greater = []
    less = []
    equal = []
    if len(lst) > 1:
        for num in lst:
            if num > pivot:
                greater.append(num)
            elif num == pivot:
                equal.append(num)
            else:
                less.append(num)
        return quickSort(less)+equal+quickSort(greater)
    else:
        return lst

def main():
    lst = [1000000,100000,1000,10000,100,10]
    sortedLst = quickSort(lst)
    print("Quicksorted List: ", sortedLst)

main()

How come when I run my code, it says that it runs into this error:

ValueError: empty range for randrange() (0,0, 0)

Answer 1

The only problem is that you try to select randomIndex even, when lst is empty, just move your initializations into if condition where you are sure that they are non empty

import random

def quickSort(lst):
    if len(lst) > 1:
        randomIndex = random.randint(0,len(lst)-1)
        pivot = lst[randomIndex]
        greater = []
        less = []
        equal = []
        for num in lst:
            if num > pivot:
                greater.append(num)
            elif num == pivot:
                equal.append(num)
            else:
                less.append(num)
        return quickSort(less)+equal+quickSort(greater)
    else:
        return lst

def main():
    lst = [1000000,100000,1000,10000,100,10]
    sortedLst = quickSort(lst)
    print("Quicksorted List: ", sortedLst)

main()