classmethod: 函数对本类进行处理 staticmethod: 函数不对本类里面的参数作处理python
https://www.programiz.com/python-programming/methods/built-in/staticmethod https://www.programiz.com/python-programming/methods/built-in/classmethod
浅复制: 对于不可变对象会开辟新空间,可变对象直接引用函数