def merge_sort(alist):
    '''归并排序'''
    n = len(alist)
    if n <= 1:
        return alist
    mid = n//2
    left_list = merge_sort(alist[:mid])
    right_list = merge_sort(alist[mid:])
    #2个有序的合并
    left_point = 0
    right_point = 0
    result = []
    while left_point < len(left_list) and right_point < len(right_list):
        if left_list[left_point] < right_list[right_point]:
            result.append(left_list[left_point])
            left_point += 1
        else:
            result.append(right_list[right_point])
            right_point += 1
    result += left_list[left_point:]
    result += right_list[right_point:]
    return result

if __name__ == '__main__':
    li = [1, 3, 9, 0, -30, -54, 86]
    print(li)
    sorted_list = merge_sort(li)
    print('original list:',li)
    print('new list:',sorted_list)

C:\Users\user\AppData\Local\Programs\Python\Python36\python.exe “C:/Users/user/PycharmProjects/hellow python/test.py”
[1, 3, 9, 0, -30, -54, 86]
original list: [1, 3, 9, 0, -30, -54, 86]
new list: [-54, -30, 0, 1, 3, 9, 86]

Process finished with exit code 0