[Python-Dev] PEP-435 reference implementation (original) (raw)

Ethan Furman ethan at stoneleaf.us
Wed May 1 07:50:31 CEST 2013

On 04/30/2013 09:47 PM, Barry Warsaw wrote:

On Apr 30, 2013, at 07:39 PM, Glenn Linderman wrote:

Because Guido said no subclassing. Indeed, I heard him. But what I heard was that subclasses shouldn't be allowed to define new enumeration values, and that was the point of all his justification and the justifications in the Stack Overflow discussion he linked to. I don't want to disagree, or argue that point, there are reasons for it, although some have raised counter-arguments to it. This is not intended to be a counter-argument to the point that there should be no new enumeration values created in subclasses. That's a shame, because disallowing subclassing to extend an enum will break my existing use cases. Maybe I won't be able to adopt stdlib.enums after all. :(

What is your existing use case?

The way I had subclassing working originally was for the subclass to create it's own versions of the superclass' enum items -- they weren't the same object, but they were equal:

--> class Color(Enum): ... red = 1 ... green = 2 ... blue = 3

--> class MoreColor(Color): ... cyan = 4 ... magenta = 5 ... yellow = 6

--> Color.red is MoreColor.red False

--> Color.red == MoreColor.red True

If you switched from is to == would this work for you?

-- Ethan

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