Does Python really follow its philosophy of "Readability counts"?

bieffe62 at gmail.com bieffe62 at gmail.com
Mon Jan 12 14:14:35 CET 2009


On 12 Gen, 00:02, Paul Rubin <http://phr...@NOSPAM.invalid> wrote:
> Carl Banks <pavlovevide... at gmail.com> writes:
> > and where it was manipulated for that matter.
>
> > This criticism is completely unfair.  Instance variables have to be
> > manipulated somewhere, and unless your object is immutable, that is
> > going to happen outside of __init__.  That's true in Java, C++, and
> > pretty much any other language.
>
> The criticism is very valid.  Some languages do support immutable
> variables (e.g. "final" declarations in Java, "const" in C++, or
> universal immutability in pure functional languages) and they do so
> precisely for the purpose of taming the chaos of uncontrolled
> mutation.  It would be great if Python also supported immutability.
>
> > I'm not going to argue that this doesn't hurt readability, because it
> > does (though not nearly as much as you claim).  But there are other
> > considerations, and in this case the flexibility of defining
> > attributes outside __init__ is worth the potential decrease in
> > readability.
>
> There are cases where this is useful but they're not terribly common.
> I think it would be an improvement if creating new object attributes
> was by default not allowed outside the __init__ method.  In the cases
> where you really do want to create new attributes elsewhere, you'd
> have to explicitly enable this at instance creation time, for example
> by inheriting from a special superclass:
>
>    class Foo (DynamicAttributes, object): pass
>

You cannot do that, but you can establish a fixed set of attributes by
defining
the __slot__ class variable.


Ciao
-----
FB



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