gistfile1.py

class fakeGlobal(object):
    def __init__(self, f):
        self.f = f
        self.__name__ = f.__name__

    def __call__(self, *args):
        global derpadil
        derpadil = "blarg"
        retval = self.f(*args)
        del derpadil
        return retval

@fakeGlobal
def blurf():
    print derpadil

blurf()