Hi. What is the intendend semantic wrt to __xxxattr__ caching: class X: pass def cga(self,name): print name def iga(name): print name x=X() x.__dict__['__getattr__'] = iga # 1. x.__getattr__ = iga # 2. X.__dict__['__getattr__'] = cga # 3. X.__getattr__ = cga # 4. x.a for the manual http://www.python.org/doc/current/ref/customization.html with all the variants x.a should fail, they should have no effect. In practice 4. work. Is that an implementation manual mismatch, is this indented, is there code around using 4. ? I'm asking this because jython has differences/bugs in this respect? I imagine that 1.-4. should work for all other __magic__ methods (this should be fixed in jython for some methods), OTOH jython has such a restriction on __del__ too, and this one cannot be removed (is not simply a matter of caching/non caching). regards, Samuele Pedroni.