gistfile1.py

>>> class A(object):
...     @classmethod
...     def magic(cls, fn):
...         def _f(*args, **kwargs):    
...             print "Hello from", cls, "_f", args, kwargs
...             return fn(*args, **kwargs) 
...         return _f
... 
>>> class B(object):
...     @A.magic
...     def foo(self, a, b, c):
...         return a + b + c
... 
>>> b = B()
>>> b.foo(1, 3, c=5)
Hello from <class '__main__.A'> _f (<__main__.B object at 0x17872d0>, 1, 3) {'c': 5}
9
>>>