[Python-Dev] Arbitrary non-identifier string keys when using **kwargs

[Chris Jerdonek]

On Tue, Oct 9, 2018 at 7:13 PM Benjamin Peterson <benjamin at python.org> wrote:
> On Tue, Oct 9, 2018, at 17:14, Barry Warsaw wrote:
> > On Oct 9, 2018, at 16:21, Steven D'Aprano <steve at pearwood.info> wrote:
> > >
> > > On Tue, Oct 09, 2018 at 10:26:50AM -0700, Guido van Rossum wrote:
> > >> My feeling is that limiting it to strings is fine, but checking those
> > >> strings for resembling identifiers is pointless and wasteful.
> > >
> > > Sure. The question is, do we have to support uses where people
> > > intentionally smuggle non-identifier strings as keys via **kwargs?
> >
> > I would not be in favor of that.  I think it doesn’t make sense to be
> > able to smuggle those in via **kwargs when it’s not supported by
> > Python’s grammar/syntax.
>
> Can anyone think of a situation where it would be advantageous for an implementation to reject non-identifier string kwargs? I can't.

One possibility is that it could foreclose certain security bugs from
happening. For example, if someone has an API that accepts **kwargs,
they might have the mistaken assumption that the keys are identifiers
without special characters like ";" etc, and so they could make the
mistake of thinking they don't need to escape / sanitize them.

--Chris

>
> I agree with Guido—banning it would be too much trouble for no benefit.
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