[Python-Dev] Handling of sys.args (Re: User's complaints)

[Guido van Rossum]

On 7/13/06, Ka-Ping Yee <python-dev at zesty.ca> wrote:
> On Thu, 13 Jul 2006, Greg Ewing wrote:
> > Would it help if sys were pre-imported into the builtins?
> > Or do you think that args shouldn't live in sys at all?
>
> I feel like the command-line arguments don't really belong in sys,
> and i'd rather not have 'sys' pre-imported into the builtins.
>
> I think of 'sys' as the place for sensitive interpreter internals
> and the builtins as the place for harmless functions.  They're at
> opposite ends of the scale -- 'sys' is the most privileged;
> builtins are the least privileged.  From a security point of view,
> 'import' is the main way to get dangerous new functionality.
> I realize 'open' breaks this concept, but it's nice to be able to
> say, to a rough approximation, that preventing 'import' gives you
> an interpreter that can do computations but isn't a security risk.
>
> These are just my feelings -- i'm not sure how consistent this is
> with the original intent of 'sys'.  I think it would be a quite
> useful distinction to have, though.

sys is a grab-bag. Note that it also has a good deal of harmless
read-only data: maxint, version, platform and many more. But it seems
to specialize in things that you may modify to change global behavior:
path, modules, stdout, ps1, displayhook and others. I'nm afraid if we
were to split it by functionality we'd have to split it 5-way or so...

> > And while we're on the subject, anyone think it would
> > be a good idea to drop the silly feature of having
> > the program name as args[0]? You almost *never* want
> > to treat it the same way as the rest of the args,
> > so the first thing you always do is args[1:].
>
> Starting the args array with the first argument (and putting
> the program name somewhere else) seems Pythonic to me.

As long as it's called args, not argv, I agree.

-- 
--Guido van Rossum (home page: http://www.python.org/~guido/)