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Date: Thu, 9 Aug 2012 11:32:00 +1000
Subject: Re: Looking for a good introduction to object oriented programming with Python
From: Chris Angelico <rosuav@gmail.com>
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On Thu, Aug 9, 2012 at 3:28 AM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> (As they say: I'll believe that corporations are people when Texas
> executes one.)

If proper excuse you can trump any,
You may wind up a Limited Company
You cannot conveniently blow it up!

-- WS Gilbert, "Utopia, Ltd"

But not every "is-a" relationship needs to be represented as class
inheritance. So what if all your Customers are Persons? Do you
_really_ need a Person base class? In a lot of systems, you don't. If
anything, you might have a generic base class for every entity that
has an Address (which would include corporations), but that's more
likely to want to be composition than inheritance (the customer Has-An
Address rather than the customer Is-An AddressibleEntity). Flat is
better than nested.

Of course, if you don't need an actual use-case, I could invent
several ridiculous base classes. Why not have one for Body, which
would be subclassed by Person and Corporation (after all, a
corporation is a body, that's where the name comes from), but not
Ghost. And then you could have a mixin called Intelligence which is
used by Corporation and Army (everyone knows what Business
Intelligence and Military Intelligence are), sometimes used by Person,
but never used by ClassDesign.

ChrisA