Python快速排序。超出调用堆栈

Question

这是我在python中尝试实现的快速排序

但是，我注意到有一个max call stack exceeded错误，可能是因为我的集合的长度永远不会下降。你知道吗

打印时，我注意到递归调用不会更新“end”变量

def swap(collection, index1, index2):
    temp = collection[index1]
    collection[index1] = collection[index2]
    collection[index2] = temp

def partition(collection, idx1, idx2):
    left = idx1
    right = idx2
    pivot = len(collection)//2

    while(left < right):

        while(collection[left] < collection[pivot]):
            left += 1

        while(collection[right] > collection[pivot]):
            right -= 1       

        if left < right:
            swap(collection, left, right)
            left +=1
            right -=1

    return left


def quickSort(collection, start, end):    
    #Check for base case        
    if len(collection) > 1:        
        index = partition(collection, start, end)        
        newIdx = index - 1        
        if start < newIdx:                        
            quickSort(collection, start, newIdx)

        if index < right: 
            quickSort(collection, index, end)


    return collection


array = [7,5, 10, 12, 3,2,9]

quickSort(array, 0, len(array) - 1)
print(array)