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[Python-Dev] [Python-checkins] peps: Pre-alpha draft for PEP 435 (enum). The name is not important at the moment, as

Eli Bendersky eliben at gmail.com
Sat Feb 23 17:27:50 CET 2013 
On Sat, Feb 23, 2013 at 7:57 AM, R. David Murray <rdmurray at bitdance.com>wrote:

> On Sun, 24 Feb 2013 01:31:09 +1000, Nick Coghlan <ncoghlan at gmail.com>
> wrote:
> > On Sun, Feb 24, 2013 at 1:06 AM, Antoine Pitrou <solipsis at pitrou.net>
> wrote:
> > > On Sat, 23 Feb 2013 16:02:31 +0100
> > > Stefan Krah <stefan at bytereef.org> wrote:
> > >> eli.bendersky <python-checkins at python.org> wrote:
> > >> > +Ordered comparisons between enumeration values are *not*
> supported.  Enums are
> > >> > +not integers!
> > >>
> > >> Hmm. I think this limits interoperation with C libraries and
> prototyping
> > >> C code.
> > >
> > > Agreed, this is a deal-breaker IMO. I'd actually argue that enums are
> > > not terribly useful apart from interacting with C constants.
> >
> > I've argued in the past that we should have a "Named Value" mechanism
> > *before* we have a proposal to group named constants in some fashion
> > (such as sequential enums, or binary flag groups). It never gained
> > much traction, even though it could be more useful in many cases
> > (think things like being able to tag a file descriptor with the repr
> > of the object it belongs to)
> >
> > After seeing this checkin, I also suggested to Eli and Barry that any
> > new PEP on this topic should come with a survey of *existing*
> > pseudo-enums in the standard library, and an explanation of how the
> > proposal can be used to make those either easier to debug when they
> > show up in error messages or otherwise make it easier to detect when
> > you've made a mistake while working with them.
>
> See also http://bugs.python.org/issue16801#msg178542 for another use
> case for named values.
>
> I've seen an awful lot of code that uses global variables or class
> attributes primarily to get name validation on constant values, and I
> think all of that code would be a prime candidate for using Named Values.
> Some of them are also enum-like, but many of them are not.  So I'm with
> Nick on this one.
>

Any suggestions for places in the stdlib where enums could come useful will
be most welcome

Eli
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