Another newbie question

Xavier Morel xavier.morel at masklinn.net
Sat Dec 10 12:07:13 CET 2005


Mike Meyer wrote:
> And you've once again missed the point. The reason you don't
> manipulate the attributes directly is because it violates
> encapsulation, and tightens the coupling between your class and the
> classes it uses. It means you see the implementation details of the
> classes you are using, meaning that if that changes, your class has to
> be changed to match.
> 
One of Python's greatnesses is that a property is, for all means an 
purposes, a fully virtual instance attribute/member.

If you follow the KISS principle, as long as your (naive? probably) 
implementation of the class has "real" attributes and their manipulation 
is meaningful & makes sense from an external point of view, just leave 
it at that. If you happen to change the implementation for whatever 
reason and happen to remove the real attributes, just create virtual 
attributes with a property and be done with it.

Wrapping everything just because you can and considering that 
encapsulation is only truly done if you never happen to touch what's 
under the hood (even without knowing it) is the Java Way, this is Python.

In Python, the interface of an object instance is always virtualized 
because you can never know if you're manipulating "real" attributes or 
property-spawned virtual attributes. _that_, in my opinion, is not 
knowing about the implementation details.

While a Java object is mineral (set in stone) and trying to abstract 
everything from the start (and generate 50 pages documentation for each 
class to be sure that you didn't miss anything) kind of makes sense, a 
Python object is an organic, morphing, living entity. Don't abstract 
everything and over-engineer from the start just because you can and 
because you'd do it in Java or C#, only abstract (from your point of 
view) when you *have to*. And remember that "Java's Object Oriented 
Programming" is not the only one worth using, even though some people 
would like to make you believe it.



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