[Python-Dev] [Python-checkins] peps: Pre-alpha draft for PEP 435 (enum). The name is not important at the moment, as (original) (raw)

Ethan Furman ethan at stoneleaf.us
Mon Feb 25 20:34:35 CET 2013

Antoine, question for you:

Do you think enums from different groupings should compare equal?

If no, how would you propose to handle the following:

8<---------------------------------------------------------------------------- --> import yaenum

--> class Color(yaenum.Enum): ... black ... red ... green ... blue ...

--> class Literature(yaenum.Enum): ... scifi ... fantasy ... mystery ... pop ...

--> Color.black Color('black', value=0)

--> Literature.scifi Literature('scifi', value=0)

--> black = Color.black

--> scifi = Literature.scifi

--> black == 0 True

--> hash(black) 0

--> scifi == 0 True

--> hash(scifi) 0

--> black == scifi False

--> hash(0) 0

--> huh = dict() --> huh[black] = 9 --> huh {Color('black', value=0): 9}

--> huh[0] 9 --> huh[scifi] Traceback (most recent call last): File "", line 1, in KeyError: Literature('scifi', value=0)

--> huh[scifi] = 11 --> huh {Color('black', value=0): 9, Literature('scifi', value=0): 11}

--> huh[0] 9

--> del huh[0] --> huh[0] 11

8<----------------------------------------------------------------------------

I do not think enums from different classes should compare equal.

I see two ways around the above issue:

make enums unhashable, forcing the user to pick a hash method;
make the hash based on something else (like the enum's name) in which case the enum would not be /completely/ interoperable, even though it is a subclass of int