Quicksort in Python

import random

class QuickSort :
    def __init__(self):
        self.r = random.Random()
       
    def sort(self, input):
        if len(input) <= 1 :
            return input

        pivot = self.r.randint(0, len(input)-1)
        pivotValue = input[pivot]

        left = list()
        right = list()

        s = 0
        for elem in input:
            s = s + elem
            if elem < pivotValue :
                left.append(elem)
            else :
                right.append(elem)
       
        if (len(left)==0 or len(right)==0) \
                and s/float(len(input)) == pivotValue:
            return input


        return self.sort(left) + self.sort(right)


if __name__ == "__main__":
    sorter = QuickSort()
    print sorter.sort([1,3,2,4,2,5,3,4,3,3,2,32,235,23,523,5,235,23-253])