[Python-Dev] AutoNumber Enum

Brett Cannon brett at python.org
Wed Jun 29 14:15:11 EDT 2016

On Wed, 29 Jun 2016 at 10:41 Ethan Furman <ethan at stoneleaf.us> wrote:

> There is a several-month-old request to add aenum's [1] AutoNumberEnum
> to the stdlib [2].
> The requester and two of the three developers of Enum are in favor (the
> third hasn't chimed in yet).
> This new addition would enable the following:
>    from Enum import AutoNumberEnum
>    class Color(AutoNumberEnum):
>        # auto-number magic is on
>        Red
>        Green
>        Blue
>        Cyan
>        # magic turns off when non-enum is defined
>        def is_primary(self):
>            # typos in methods, etc, will raise
>            return self in (self.Red, self.Grene, self.Blue)
>        # typos after the initial definition stanza will raise
>        BlueGreen = Blue + Grene
> There is, of course, the risk of typos during the initial member
> definition stanza, but since this magic only happens when the user
> explicitly asks for it (AutoNumberEnum), I think it is acceptable.
> The `start` parameter is still available, and assigning a number is
> supported (subsequent numbers will (re)start from the assigned number).
> Thoughts?  Opinions?  Flames?

Is it going to subclass Enum or IntEnum? Personally I would be quite happy
to never have to specify a value for enums ever again, but only if they
subclass Enum (since IntEnum is for compatibility with C stuff where a
specific value is needed I don't think users need to mess that up by having
the automatic numbering not work how they would expect).
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