[Python-Dev] Enum: subclassing? (original) (raw)

Antoine Pitrou solipsis at pitrou.net
Wed May 1 22:33:44 CEST 2013

On Wed, 1 May 2013 13:05:53 -0700 Eli Bendersky <eliben at gmail.com> wrote:

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.

Ok, I've mixed up the example. But, still, since Season(1) should return the Season.spring singleton, I don't see any reasonable thing for MySeason(1) to return. Hence the request to raise an exception.

Regards

Antoine.

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