[Python-Dev] PEP 435: initial values must be specified? Yes (original) (raw)

Ethan Furman ethan at stoneleaf.us
Sun May 5 22:09:50 CEST 2013

On 05/05/2013 10:07 AM, � wrote:> I'm chiming in late, but am I the only one who's really bothered by the syntax?

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

No, you are not only one that's bothered by it. I tried it without assignments until I discovered that bugs are way too easy to introduce. The problem is a successful name lookup looks just like a name failure, but of course no error is raised and no new enum item is created:

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

--> class MoreColor(Color): ... red, orange, yellow ...

--> type(MoreColor.red) is MoreColor False

--> MoreColor.orange <MoreColor.orange: 4> # value should be 5

About the closest you going to be able to get is something like:

def e(_next=[1]): e, _next[0] = _next[0], _next[0] + 1 return e

class Color(Enum): red = e() green = e() blue = e()

and you can keep using e() for all your enumerations, since you don't care what actual value each enumeration member happens to get.

-- Ethan

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