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Re: Enum questions.

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  Re: Enum questions. Michael Selik <michael.selik@gmail.com> - 2016-04-13 12:08 +0000
    Re: Enum questions. Rustom Mody <rustompmody@gmail.com> - 2016-04-13 05:33 -0700

#106937 — Re: Enum questions.

On Wed, Apr 13, 2016, 12:14 PM Antoon Pardon <antoon.pardon@rece.vub.ac.be>
wrote:

> I have been looking at the enum documentation and it
> seems enums are missing two features I rather find
> important.
>
> 1) Given an Enum value, someway to get the next/previous
>    one
>
> 2) Given two Enum values, iterate over the values between
>    them.
>
> Did I miss those in the documentation or are they really
> missing?
>

An Enum corresponds to "nominal" data that is coded as a number simply for
storage rather than meaning. If you want next/previous you are thinking of
"ordinal" data which is coded as numbers for the purpose of comparison (but
not arithmetic). Placing nominal data in order would be comparing apples
and oranges, so to speak.

However, IntEnum should give you the features you want.

https://docs.python.org/3/library/enum.html#intenum

>

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#106938

On Wednesday, April 13, 2016 at 5:39:13 PM UTC+5:30, Michael Selik wrote:
> On Wed, Apr 13, 2016, 12:14 PM Antoon Pardon
> wrote:
> 
> > I have been looking at the enum documentation and it
> > seems enums are missing two features I rather find
> > important.
> >
> > 1) Given an Enum value, someway to get the next/previous
> >    one
> >
> > 2) Given two Enum values, iterate over the values between
> >    them.
> >
> > Did I miss those in the documentation or are they really
> > missing?
> >
> 
> An Enum corresponds to "nominal" data that is coded as a number simply for
> storage rather than meaning. If you want next/previous you are thinking of
> "ordinal" data which is coded as numbers for the purpose of comparison (but
> not arithmetic). Placing nominal data in order would be comparing apples
> and oranges, so to speak.
> 
> However, IntEnum should give you the features you want.
> 
> https://docs.python.org/3/library/enum.html#intenum
> 
> >

from enum import Enum
# General (not contiguous) enum
class Color(Enum):
    red = 10
    blue = 20
    green = 30


>>> Color.__members__
OrderedDict([('red', <Color.red: 1>), ('blue', <Color.blue: 2>), ('green', <Color.green: 3>)])

>>> set(Color.__members__)
set(['blue', 'green', 'red'])

>>> {n:Color[n] for n in set(Color.__members__)}
{'blue': <Color.blue: 20>, 'green': <Color.green: 30>, 'red': <Color.red: 10>}
>>> 

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