Python中变量在内存的存储与地址变化详解
https://blog.csdn.net/as480133937/article/details/87305247
https://blog.csdn.net/Com_ma/article/details/82156912
https://www.cnblogs.com/addswanmei/p/11204257.html
Python 函数及函数作用域
https://blog.csdn.net/ruanxingzi123/article/details/82622592
https://www.cnblogs.com/saintdingspage/p/7788958.html
函数做为返回值