[Tutor] design questions: pythonic approach to ostriches

[Alan Gauld]

> I do remain a bit surprised that there seems to be no way to
implement
> what I naively thought would be the obvious solution -- to remove an
> inherited method from the instance's dictionary.

You can, as Kent said, override the method to do nothing. Some
languages,
like Eifell offer better support for that than others.

But there is a danger in removing methods too. By doing so you break
one of the fundamental principles of inheritence:
that everywhere that you use the superclass you can use the sub class.

If you remove the fly() method from your subclass of birds code like
this will break:

birds = [ aSwallow, anOstrich, anEmu, anEagle]

for bird in birds:
   bird.fly()

Whereas if you simply make fly a null method you can still call it
but nothing happens - a lot safer...

But conceptually the problem (and it is common) is that bird has a
fly() method when not all birds can fly - the object model is broken
at a high level of abstraction.

HTH,

Alan G.