[Python-Dev] Enum: subclassing?

[Eli Bendersky]

On Wed, May 1, 2013 at 11:59 AM, Georg Brandl <g.brandl at gmx.net> wrote:

> Am 01.05.2013 20:44, schrieb Antoine Pitrou:
> > On Wed, 01 May 2013 10:21:30 -0700
> > Ethan Furman <ethan at stoneleaf.us> wrote:
> >> We may not want to /completely/ disallow subclassing.  Consider:
> >>
> >> --> class StrEnum(str, Enum):
> >> ...    '''string enums for Business Basic variable names'''
> >> ...
> >> --> class Vendors(StrEnum):
> >> EnumError: subclassing not allowed
> >
> > I don't see the point of disallowing subclassing. It sounds like
> > a pointless restriction.
> >
> > However, perhaps the constructor should forbid the returning of a base
> > type, e.g.:
> >
> > class Season(Enum):
> >     spring = 1
> >
> > class MySeason(Season):
> >     """I look nicer than Season"""
> >
> > MySeason('spring')
> > ...
> > ValueError: Season.spring is not a MySeason instance
> >
> > (what this means is perhaps the subclassing of non-empty enum classes
> > should be forbidden)
>
> That's exactly what's implemented in the ref435 code at the moment.
>
>
It can't be because __call__ is by-value lookup, not by-name lookup.
By-name lookup is Season.spring or getattr(Season, 'spring')

Eli
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