class method ,static method ,bounded method

Occasionally when writing a class you want to include a function that is called from the class, not the instance. Perhaps this method creates new instances, or perhaps it is independent of any properties of any individual instance. Python actually gives you two ways to do this, depending if your method needs to (or should) know about which class called it. Both involve applying decorators to your methods.

A 'class method' receives the class as the first argument, just as a regular instance method receives the instance as the first argument. So, the method is aware if it is being called from its own class or from a subclass.

A 'static method' receives no information about where it is called; it is essentially a regular function, just in a different scope.

Class and static methods can be called straight from the class, as Class.method(), or from an instance as Class().method(). The instance is ignored except for its class. Here's an example of each, along with a regular instance method:

# 's

 1class Class:
 2    @classmethod
 3    def a_class_method(cls):
 4        print 'I was called from class %s' % cls
 5    #
 6    @staticmethod
 7    def a_static_method():
 8        print 'I have no idea where I was called from'
 9    #
10    def an_instance_method(self):
11        print 'I was called from the instance %s' % self
12
13instance = Class()
14
15Class.a_class_method()
16instance.a_class_method()
17# both print 'I was called from class __main__.Class'
18
19Class.a_static_method()
20instance.a_static_method()
21# both print 'I have no idea where I was called from'
22
23Class.an_instance_method()
24
25# raises TypeError
26instance.an_instance_method()
27# prints something like 'I was called from the instance <__main__.Class instance at 0x2e80d0>'