from functools import wraps
def by_about(f):
    @wraps(f)
    def wrapper(self, about, *args, **kwargs):
        o = self.create_object(about=about)
        if type(o) == types.IntType:   # error code
            return o
        return f(self, o.id, *args, **kwargs)
    return wrapper

.....
    tag_object_by_about = by_about(tag_object_by_id)
    untag_object_by_about = by_about(untag_object_by_id)
....