A class method is a method bound to a class and not to an instance.
>>> class MyFantasticClass(object):
... def interrupt(self):
... print 'Or a woman !'
>>> m = MyFantasticClass()
>>> m.interrupt()
Or a woman !
The interrupt function is an instance function, it receives self as an argument. This is not adapted here, because for the function to be used, an instance must be created: even though the interrupt method does not make use of the instance, it is passed as an input parameter to the function.
How to define the *interrupt* method so that it is called directly on the class without having to create an instance?
Example :
MyFantasticClass.interrupt()
Answer: use a class method or even better a static method. The class method:
>>> class MyFantasticClass(object):
... @classmethod
... def interrupt( klass):
... print 'Or a woman !'
>>> MyFantasticClass.interrupt()
Or a woman !
For the user of the class, it dos not make much of a difference if the function is bound to the class or just static, but it changes the definition. The class method is passed the class as the first argument (and not self, the instance). In our example, the best choice is a static method since the function uses neither the instance nor the class:
>>> class MyFantasticClass(object):
... @staticmethod
... def interrupt():
... print 'Or a woman !'
>>> MyFantasticClass.interrupt()
Or a woman !