[Python-Dev] PEP 435 -- Adding an Enum type to the Python standard library

[R. David Murray]

On Sat, 20 Apr 2013 14:10:32 -0400, Barry Warsaw <barry at python.org> wrote:
> On Apr 13, 2013, at 08:37 AM, Tim Delaney wrote:
> 
> >Just using definition order as the stable iteration order would do the
> >trick - no need for any comparisons at all. Subclasses (e.g. IntEnum) can
> >then override it.
> 
> I think this isn't possible if we want to keep backward compatibility with
> earlier Pythons, which I want to do.  OTOH, we have another natural sorting
> order for base Enums sitting right in front of us: the attribute name.  These
> have to be unique and ordered, so why not use this for both the __repr__() and
> the base Enum __iter__()?  IntEnum can override __iter__() to iterate over
> item values, which also must be ordered.
> 
> I just made this change to flufl.enum and it seems to work well.
> 
> >>> from flufl.enum import Enum
> >>> A = Enum('A', 'a b c')
> >>> A
> <A {a: 1, b: 2, c: 3}>
> >>> for item in A: print(item)
> ... 
> A.a
> A.b
> A.c
> >>> B = Enum('B', 'c b a')
> >>> B
> <B {a: 3, b: 2, c: 1}>
> >>> for item in B: print(item)
> ... 
> B.a
> B.b
> B.c
> >>> from flufl.enum import IntEnum
> >>> C = IntEnum('C', 'c b a')
> >>> C
> <C {a: 3, b: 2, c: 1}>
> >>> for item in C: print(item)
> ... 
> C.c
> C.b
> C.a

I think definition order would be much better, but if we can't have that,
this is probably better than value order for non-int.

--David