[Python-Dev] Python roadmap

[Alex Martelli]

On Saturday 01 February 2003 07:33 pm, Guido van Rossum wrote:
   ...
> It is sort of against the rules of the language -- the whole point of
> scoping is that you should be able to define variables even if they
> block a builtin (that you may never have heard of and don't need) from
> view.

It would be wonderful to be able to OPTIONALLY get a warning
for any "shadowing" of a name in an ``outer'' scope by a name
in an ``inner'' scope, though -- I do (occasionally) miss Java's
prohibition against doing that.

> But it would be a great feature of PyChecker (for all I know, it
> already does this).

At least in 0.8.12, which I think is the current release, PyChecker
doesn't diagnose the binding (in global or local scope) of built-in
names with a warning, no.  But I think you're right that such a
functionality would belong there.

> There's one situation where I actually *do* think this is worth a
> warning, or perhaps even an error.  When you import a module and
> assign to an attribute of it that didn't exist before and has the name
> of a built-in, you may change that module's meaning.  If this wasn't

Very good point.  Such behavior seems unlikely to me to be
accidental (the usage "import X; X.Y=Z" is rare indeed), so I'm
not sure warnings would help all that much -- but, _forbidding_
this when Y names a built-in could indeed open the way to some 
very useful optimizations in the future.  Of course, enabling this 
optimization would also require a prohibition against "overriding" 
of built-ins by one's own versions -- I don't think that would be a 
great loss in terms of practical functionality.


Alex