pure virtual functions in python

[Erik Max Francis]

"Delaney, Timothy" wrote:

> Most responses have used `NotImplementedError`. This is fine, and
> useful if
> you want the abstract class to document what methods it defines.
> 
> The other approach is to document what attributes/methods other
> functions
> require their parameters to have. This achieves the same effect (but
> throws
> an `AttributeError` rather than a `NotImplementedError`), but is in
> many
> ways more versatile.
> 
> I have never used `NotImplementedError` in my python code. Why bother?

I prefer explicit is better than implicit.  Simply using documentation
certainly gets the same effect, I agree, but there's something more
prominently indicating "Hey, you forgot to override something" when you
get a NotImplementedError rather than an AttributeError.  An
AttributeError might just indicate, for instance, that you spelled the
method name wrong.  A NotImplementedError means that I spelled it right,
but someone, somewhere along the line forgot to override a method which
required overriding.

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