[Python-Dev] PEP 362 Third Revision

[Nick Coghlan]

On Fri, Jun 15, 2012 at 3:23 PM, Larry Hastings <larry at hastings.org> wrote:
> I disagree with the description "ill-defined".  I would be very surprised
> indeed if either you or Benjamin genuinely didn't understand exactly what
> "is_implemented" represents.  If you're suggesting that the documentation is
> inadequate we can certainly address that.
>
> Perhaps you meant "ill-concieved"?

No, I mean ill-defined. The criteria for when a particular platform
should flip that bit for an arbitrary parameter is highly unclear, as
whether or not a particular parameter is "implemented" or not depends
on the operation and the parameter.

Let's take the "buffering" parameter to the open() builtin. It has
three interesting settings:
- unbuffered
- line buffered
- fixed size buffering

What counts as "implemented" in that case? Supporting all 3? At least
2? Any 1 of them? If there's a maximum (or minimum) buffer size, does
that still count as implemented?

To know what "is_implemented" means for any given parameter, it's
going to have to be documented *for that parameter*. In that case,
better to define an interface specific mechanism that lets people ask
the questions they want to ask. It's not appropriate to lump it into a
general purpose introspection facility (certainly not one that hasn't
even been added yet).

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia