Why does python not have a mechanism for data hiding?

Russ P. Russ.Paielli at gmail.com
Thu Jun 5 20:36:28 CEST 2008


On Jun 5, 4:53 am, Bruno Desthuilliers <bruno.
42.desthuilli... at websiteburo.invalid> wrote:
> Russ P. a écrit :

> Given your very recent discovery of what 'dynamic' *really* means in
> Python (like, for exemple, dynamically adding / replacing attributes -
> including methods - on a per-class or per-instance basis), possibly, yes.

My "very recent" discovery? Funny, I thought I knew that several years
ago. You must know more about me than I know about myself.

> > I also realize, by the way, that Python allows a client of a class to
> > define a new class member from completely outside the class
> > definition. Obviously, that cannot be declared private.
>
> Why so ?

Why should the client of a class not be able to declare a *private*
member of the class? You're kidding, right? Do you mind if I tell you
how to arrange the furniture in your bedroom?

> > But if the
> > same identifier is already declared private within the class, than the
> > new definition should not be allowed (because it would defeat the
> > whole idea of "private" class members).
>
> Why so ?
>
> Metaprogramming (including monkeypatching) is part of the pythoneer's
> toolbox, and while it's not something to use without pretty good
> reasons, it has many times proven to be a real life saver. In languages
> not allowing it, the solutions to the class of problems easily solved by
> monkeypatching happens to be at best a kludge, at worst plain
> unsolvable, at least without too much effort to be even worth it. Your
> above proposition would arbitrarily make possible and useful things
> either uselessly complicated or near impossible.

For the record, I have made it abundantly clear that I don't think
Python should not have as rigorous an encapsulation regime as C++ or
Java. The worst that could happen with my proposition is that you
would need to use a "mangled" name to access private data or methods.
But you will be using the name many times, you can reassign your own
name, of course, so the mangled name need not appear more than once
where it is needed.



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