Bruno Desthuilliers wrote: > You've already got the technical answer. About a possible design flaw, > it would seem to me that restricting the join() operation on specific
> subclasses breaks the LSP. OTOH, Python being dynamically typed, > inheritence is merely an implementation detail, so that may not be such > a big deal after all... Anyway, you may want to document this point to > make it clear for the next person that'll have to work this code. > > My 2 cents OK, thanks - I see your point. I was in effect implementing mutable objects, similar in some sense to lists, by extending an immutable class similar to Python's tuples. I think instead I should copy the Python type hierarchy, with the list-like and tuple-like classes each defined as sub-classes of a 'sequence' class. In this case the type checking could go away. I'm learning object-orientated programming and dynamic typed languages the hard way at the moment, by trial and error. Can you, or anyone suggest a good book which will guide me? Is there a classic text on this? The coverage of OOP in 'Learning Python' is useful, but I could do with something more in-depth. Thanks again, Andy. -- http://mail.python.org/mailman/listinfo/python-list
