Python classmethod staticmethod 进价学习

@classmethod means: when this method is called, we pass the class as the first argument instead of the instance of that class (as we normally do with methods). This means you can use the class and its properties inside that method rather than a particular instance.

@staticmethod means: when this method is called, we don't pass an instance of the class to it (as we normally do with methods). This means you can put a function inside a class but you can't access the instance of that class (this is useful when your method does not use the instance).

When an instance attribute is referenced that isn’t a data attribute, its class is searched. 

If the name denotes a valid class attribute that is a function object, a method object is 
created by packing (pointers to) the instance object and the function object just found together
in an abstract object: this is the method object. When the method object is called with an 
argument list, a new argument list is constructed from the instance object and the argument list, 

and the function object is called with this new argument list.

类方法：
classmethod 是类对象与函数的结合。
可以使用类和类的实例调用，但是都是将类作为隐含参数传递过去。
使用类来调用 classmethod 可以避免将类实例化的开销。

类的静态方法：
当一个函数逻辑上属于一个类又不依赖与类的属性的时候，可以使用staticmethod。
使用 staticmethod 可以避免每次使用的时都会创建一个对象的开销。
staticmethod 可以使用类和类的实例调用。但是不依赖于类和类的实例的状态。

实例方法：
instance method 就是实例对象与函数的结合。
使用类调用，第一个参数明确的传递过去一个实例。
使用实例调用，调用的实例被作为第一个参数被隐含的传递过去。