What does 'self' refer to in a @classmethod?

Question

I thought I was starting to get a grip on "the Python way" of programming. Methods of a class accept self as the first parameter to refer to the instance of the class whose context the method is being called in. The @classmethod decorator refers to a method whose functionality is associated with the class, but which doesn't reference a specific instance.

So, what does the first parameter of a @classmethod (canonically 'self') refer to if the method is meant to be called without an instance reference?

Answer 1

class itself:

A class method receives the class as implicit first argument, just like an instance method receives the instance.

class C:
    @classmethod
    def f(cls):
        print(cls.__name__, type(cls))

>>> C.f()
C <class 'type'>

and it's cls canonically, btw

Answer 2

The class object gets passed as the first parameter. For example:

class Foo(object):
    @classmethod
    def bar(self):
        return self()

Would return an instance of the Foo class.

EDIT:

Note that the last line would be self() not self. self would return the class itself, while self() returns an instance.

Answer 3

The first parameter of a classmethod is named cls by convention and refers to the the class object on which the method it was invoked.

>>> class A(object):
...     @classmethod
...     def m(cls):
...         print cls is A
...         print issubclass(cls, A)

>>> class B(A): pass
>>> a = A()
>>> a.m()
True
True
>>> b = B()
>>> b.m()
False 
True