[newbie] Looking for a good introduction to object oriented programming with Python

[Steven D'Aprano]

On Mon, 06 Aug 2012 10:24:10 +0100, lipska the kat wrote:

> er, the point I was trying to make is that when you say 'interface' it
> could mean so many things. If you say 'facade' everyone knows exactly
> what you are talking about. And that is EXACTLY the point.

The whole point of design patterns is to avoid getting stuck in 
incidental implementation details of a particular library or class and 
look for higher-level design patterns.

The same applies to facade -- it's just a special case of the interface 
pattern. Why get stuck in incidental implementation details of the 
particular *kind* of interface layer you need?

Obviously the person writing the interface/facade/adaptor/whatever needs 
to understand the implementation details. But the people using the 
interface don't.

Why waste brain CPUs trying to decide whether a particular interface is a 
facade, an adaptor, a bridge, a proxy, ... ? Especially since in real-
life code, any such interface is going to include elements of all of the 
above. Take this example from Wikipedia's article on Facade pattern:

=========  ========
Pattern    Intent
=========  ========
Adapter    Converts one interface to another so that it matches 
           what the client is expecting
Decorator  Adds responsibility to the interface without altering it
Facade     Provides a simplified interface
=========  ========

It's rare that the intent is as pure as that. Normally it will be:

"Simplify the interface, oh and also change the API of these three 
methods to match this other library, and add a couple of helper methods, 
and while you're at it, this method has a bug that upstream refuses to 
patch, do something about that."

So is that a facade or an adaptor, or something else?




-- 
Steven