None versus MISSING sentinel -- request for design feedback

[bruno.desthuilliers at gmail.com]

On Jul 15, 9:44 am, Cameron Simpson <c... at zip.com.au> wrote:
> On 15Jul2011 15:28, Steven D'Aprano <steve+comp.lang.pyt... at pearwood.info> wrote:
> | Against MISSING: users may expect to be able to choose their own sentinel by
> | assigning to MISSING. I don't want to support that.
>
> Well, we don't have readonly values to play with :-(
> Personally I'd do what I did above: give it a "private" name like
> _MISSING so that people should expect to have inside (and unsupported,
> unguarenteed) knowledge if they fiddle with it.

I think the point is to allow users to explicitely use MISSING in
their data sets, so it does have to be public. But anyway: ALL_UPPER
names are supposed to be treated as constants, so the "warranty void
if messed with" still apply.