python归并排序如何理解

import random

def ConfiationAlgorithm(str):

    if len(str) <= 1: #子序列

        return str

    mid = (len(str) / 2)

    left = ConfiationAlgorithm(str[:mid])#递归的切片操作

    right = ConfiationAlgorithm(str[mid:len(str)])

    result = []

    #i,j = 0,0

    while len(left) > 0 and len(right) > 0:

        if (left[0] <= right[0]):

            #result.append(left[0])

            result.append(left.pop(0))

            #i+= 1

        else:

            #result.append(right[0])

            result.append(right.pop(0))

            #j+= 1

    if (len(left) > 0):

        result.extend(ConfiationAlgorithm(left))

    else:

        result.extend(ConfiationAlgorithm(right))

    return result  

if __name__ == '__main__':

    a = [20,30,64,16,8,0,99,24,75,100,69]

    print ConfiationAlgorithm(a)

    b = [random.randint(1,1000) for i in range(10)]

    print ConfiationAlgorithm(b)