[Python-Dev] enum instances (original) (raw)

Ethan Furman ethan at stoneleaf.us
Tue Apr 30 04:17:08 CEST 2013

On 04/29/2013 06:23 PM, Marco Hemmelrath wrote:

First of all, hi, I'm new to this list.

Following the enum discussions on this list I am kind of confused about how enums and their respective instances, i.e. the values, should behave in "normal" context. I apologize beforehand for the mass of "questions" because the following contains really many discussed things but they all kinda depend on one another, and for terminology which I might've missed. Considering we have[1]: class Color(enum): red = 1 white = 2 other = "undefined" class State(enum): idle = 0 busy = 1 idling = idle ideling = 0 together with the premises: 1. type(State.busy) == State 2. type(State) == enum 3. isinstance(State.idle, State) 4. State.idle is State.idle which should mostly be agreed on (if I didn't misinterpret).

How would an enum instance (e.g. State.busy) behave in normal Python expressions? Should these instances just wrap their values and provide some simple overhead useful for enums? I'll just note down a few examples of how I think it could work and express a few thoughts on them: 1. State.busy == 1 2. State.busy == Color.red 3. int(State.Busy) is 1 4. isinstance(State.busy, int) 5. Color.other.startswith("und") 6. State.busy is not 1 7. State.busy is not Color.red 8. State.idle in State 9. 0 in State # True, False or raise? 10. State.idling is State.idle 11. State.idle == State.idling 12. State.idle is not State.idling

1 & 2 are False (would be true if using .value)

3 is True

4 & 5 are False (again, need .value)

6 is not the correct way to use is (should be ==)

7, 8, 9, 10, 11 are True

12 is False

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