subclassing versus object redefinition

[Roald de Vries]

Hi W,

On Aug 3, 2010, at 4:38 PM, wheres pythonmonks wrote:
> I think that the crux of the matter is in points #3,  #4, and #5 that
> you raised:

I think #2 is important too: a program is supposed to do what you  
expect, and I don't expect instantiation of an ABC.

> On #3:  Not clear that all possible specializations warrant
> factorization into a class.  Indeed, this may result in "premature
> abstraction" -- and make the code less clear.  Also, it will freeze in
> the base classes, making future refactoring a headache.

I agree (for small specializations only).

> On #4:  Unless I misunderstood something, there is nothing in python
> that ensures that a class definition is localized.  So, putting
> definitions in classes, does not guarantee that the definition is at a
> single location in the code.

That's right, but with classes it is possible (and encouraged) to keep  
things in a single location. The other option necessarily puts things  
where I don't expect them.

> 5) why would you want a thinner class hierarchy?
>
> The yo-yo anti-patten:
> http://en.wikipedia.org/wiki/Yo-yo_problem
>
> I have a pretty strong preference for using a small number of useful
> objects, instead of having code littered with objects strewn across
> the namespace.

I see the point, but I would like to remark that if a program does  
what you expect, you won't need to understand the whole inheritance  
graph.

> Maybe there is a Python ABC tutorial out there that can enlighten me?

http://docs.python.org/library/abc.html
http://www.doughellmann.com/PyMOTW/abc/

Cheers, Roald

PS: most people in this list prefer not top posting