In [1]: class Foo(object):
   ...:     member = {}
   ...:     @classmethod
   ...:     def register(cls, k, v):
   ...:         cls.member[k] = v
   ...:

In [2]: Foo.member.keys()
Out[2]: []

In [3]: Foo.register('hello', 'world')

In [4]: Foo.member.keys()
Out[4]: ['hello']