[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 18:35:58 CET 2013

On 02/25/2013 08:37 AM, Barry Warsaw wrote:

On Feb 25, 2013, at 07:12 AM, Ethan Furman wrote:

And if, in those places, the enums were based on ints (or strings), would it hurt you? Because in the places where I, as well as many others, use enums we need the int portion; and having to wrap the enum in an int() call is seven extra keystrokes (minor) and a heap of visual clutter (major), destroying any value the enum was supposed to have. Yes, I think enum values inheriting from int (or string) would hurt. First, as your question implies, which is it? int or str? Some people want int some want str. It can't be both, and I don't think we need two enum types.

I can see enums of at least three different types being useful: int, str, and bitmask; a valueless enum would be a fourth.

It's a deeper question though, because if enum values inherited from int, then people would expect things like Colors.red == 1 to work. Maybe you think that doesn't look so bad, but that also implies:

I do expect that to work.

>>> Colors = make('Colors', 'red green blue'.split()) >>> Animals = make('Animals', 'ant bee cat'.split()) >>> Colors.green == Animals.bee

But this I don't, and in both mine, Ted's, and Alex's versions enums from different groups do not compare equal, regardless of the underlying value. Of course, this does have the potential problem of green == 1 == bee but not green == bee which would be a problem with set and dicts -- but I'm the only one who has brought up that issue.

I get that you think wrapping the value in int() is ugly. I have a compromise that you might find acceptable. EnumValues already have .enum and .name attributes, to give you the value's class and string name respectively. It would be trivial to add a .int attribute to return the value.

Thus if you want the int value, it would be easy enough to say Colors.green.int or Animals.bee.int

Well, it certainly isn't as ugly, and isn't as hard on the wrists. If your's is the package that makes it in the stdlib I would certainly appreciate the modification.

However, as I replied to Skip, I think a stdlib solution should meet many needs, and sometimes (often, for some people ;) those needs will be better served by an int-based or str-based enum.

-- Ethan

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