[Python-ideas] constant/enum type in stdlib

[Michael Foord]

On 30 January 2013 16:26, Antoine Pitrou <solipsis at pitrou.net> wrote:

> Le Wed, 30 Jan 2013 15:22:06 +0000,
> Michael Foord <fuzzyman at gmail.com> a
> écrit :
> > On 30 January 2013 07:26, Antoine Pitrou
> > <solipsis at pitrou.net> wrote:
> >
> > > On Wed, 30 Jan 2013 17:58:37 +1300
> > > Greg Ewing <greg.ewing at canterbury.ac.nz>
> > > wrote:
> > > > Guido van Rossum wrote:
> > > >
> > > > > class color(enum):
> > > > >   RED = value()
> > > > >   WHITE = value()
> > > > >   BLUE = value()
> > > >
> > > > We could do somewhat better than that:
> > > >
> > > >     class Color(Enum):
> > > >        RED, WHITE, BLUE = range(3)
> > >
> >
> >
> >
> > With a Python 3 metaclass that provides default values for *looked up*
> > entries you could have this:
> >
> > class Color(Enum):
> >     RED, WHITE, BLUE
>
> This relies on tuple evaluation order,



It does if you do them as a tuple.


> and would also evaluate any
> other symbol looked up from inside the class body


Only if they aren't actually defined.


> (which means I
> cannot add anything else than enum symbols to the class).
>
>
So not true - it is only *undefined* symbols that are added as enum values.


> In other words, I'm afraid it would be somewhat fragile ;)
>

Well, within specific parameters...

Michael


>
> Regards
>
> Antoine.
>
>
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