[Python] Heap Sort in Python

#! /usr/bin/env python
#coding=utf-8

import random,copy

def heap_sort_helper(lst,left,right):
    # max heapify
    current_value = lst[left]
    child = 2 * left + 1
    while (child <= right):
        if (child < right and lst[child] < lst[child+1]):
            child  = child + 1
        if (current_value > lst[child]):
            break
        else:
            lst[(child-1)>>1] = lst[child]
            child = 2 * child + 1
    lst[(child-1)>>1] = current_value
    
def heap_sort(lst):
    # build heap
    for i in range((len(lst)-1)>>1,-1,-1):
        heap_sort_helper(lst,i,len(lst)-1)
    for i in range(len(lst)-1,0,-1):
        lst[i],lst[0] = lst[0],lst[i]
        heap_sort_helper(lst,0,i-1)

if  __name__ == "__main__":
    lst = [random.randint(0,20) for i in range(10)]
    lst2 = copy.deepcopy(lst)
    lst2.sort()
    print(lst)
    print(lst2)
    heap_sort(lst)
    print(lst)