I use a wrapper functions as follows to specify the callback argument of addCallback() and addErrback(). def reqConnLostCallbk(result, arg_self):     arg_self.lost_conn() def reqConnLostErrbk(failure, arg_self):     arg_self.lost_conn() ... inside a class method     d.addCallback(reqConnLostCallbk, self)     d.addErrback(reqConnLostErrbk, self)     def lost_conn(self):         // cleanup         pass Is there an alternative and/or cleaner solution to specify a class method as a callback or errback? -Arun