On Mon, 11 Jun 2007 05:27:35 -0700, Frank Millman wrote:
> I now have the following - > >>>> class A(object): > ... def __init__(self,x,y): > ... self.x = x > ... self.y = y > ... def __getattr__(self,name): > ... print 'getattr',name > ... self.compute() > ... return self.__dict__[name] > ... def compute(self): # compute all missing attributes > ... self.__dict__['z'] = self.x * self.y > [there could be many of these] > >>>> a = A(3,4) >>>> a.x > 3 >>>> a.y > 4 >>>> a.z > getattr z > 12 >>>> a.z > 12 >>>> a.q > KeyError: 'q' > > The only problem with this is that it raises KeyError instead of the > expected AttributeError. Yes, because you never assign __dict__['q']. >> You haven't told us what the 'compute' method is. >> >> Or if you have, I missed it. >> > > Sorry - I made it more explicit above. It is the method that sets up > all the missing attributes. No matter which attribute is referenced > first, 'compute' sets up all of them, so they are all available for > any future reference. If you're going to do that, why not call compute() from your __init__ code so that initializing an instance sets up all the attributes? That way you can remove all the __getattr__ code. Sometimes avoiding the problem is better than solving the problem. -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
