Python 直接赋值、浅拷贝和深度拷贝解析:
https://www.cnblogs.com/alinh/p/6603976.html
判断字符串是否为空:
https://blog.csdn.net/qiqiaiairen/article/details/52623459
Python的函数返回值返回的是值还是引用?
https://www.jianshu.com/p/fe26afef8c8e
https://www.cnblogs.com/alinh/p/6603976.html
判断字符串是否为空:
https://blog.csdn.net/qiqiaiairen/article/details/52623459
https://www.jianshu.com/p/fe26afef8c8e