[Python-Dev] PEP 435 - ref impl disc 2

[Glenn Linderman]

On 5/5/2013 7:14 PM, Nick Coghlan wrote:
> I think there comes a point where "subclass the metaclass" is the
> right answer to "how do I do X with this type?". I believe making two
> different kinds of value labelling mechanisms play nice is such a case
> :)

Could be.

Could be that sufficient operators added to an IntEnum subclass might 
work too. Although it might be unexpected that adding two enumeration 
members would produce a NamedInt :)  But of course, if the enumeration 
were defined by NamedIntEnum, it might be less surprising.

On the other hand, if Enum is in stdlib, and lots of flags parameters 
get defined with Enum, then it would be a pain in the neck to redefine 
them with NamedIntEnum, so that debugging of flag combinations is 
easier. There are enough flag parameters in the stdlib APIs to make me 
think this would be a deficiency.

Sadly, once the Enums are defined, there is to be no way to subclass 
them to add functionality, like producing a NamedInt result from 
operations on them.
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