[Tutor] Changing a class into a subclass

[Alan Gauld]

> > single instance (or indeed no instances because you could
> > use a static method... or get really fancy and create a
> > meta-class!). 
> 
> or make it a static method of Building 

Yes that's actually what I meant, but reading it back it 
sounds like I meant static Factory method.... Ho hum.

> or get really simple and use a module-level function...

Yeah., but I did say if he wanted to be OOPish.

> > class Shack(Building):
> >    def __init__(self,p1,p2...):
> >       Building.__init__(self,...)
> >       Building.register(self,'Shack', Shack)
> >       ...rest of init...
> 
> I think you want to register Shack before you ever create one. 

Yeah, you are right. My way you register it every time you 
create an instance. A single registration call right after 
the class definition is probably better.

> or you could probably get tricky and do it in a metaclass...

I would do in Smalltalk but meta classes in Python are somewhere 
that I haven't visited yet! :-)

Alan G.