OO conventions

[Daniel Nogradi]

> > > In this case, Image seems to be a python module, with the open function
> > > defined, PIL's Image is not a class.
> > >
> >
> > Thanks for the enlightening remarks, especially this last one, indeed,
> > it's not a class.
>
> Actually, this way of creating a class instance is good OO practice in
> many places: The Image.open() method acts as a factory-function for
> creating Image objects.
> You don't know, until you inspect the return value, if the created
> object is actually an instance of class Image or something which just
> happens to behave like one...
> It could for instance be a sub-class of Image, JpegImage, if that
> better suits the class library designers.
> In general, factory-functions allow greater uncoupling between
> interface and implementation.
>

>From all the enlightening replies it seems to me that my next task
should be to look into what 'factory functions' are. Whenever I've
seen the word 'factory' I just skipped it, knowing that if I really
need to know what it is, I'll come back to it later. Apparently it's
just about time, thanks all for the comments.