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


On Apr 22, 2013, at 09:31 AM, Tim Delaney wrote:

>I'm fine with iteration order being by sorted name by default, so long as
>it's easily overrideable by enum subclasses or metaclasses e.g. an IntEnum
>should probably iterate in value order.

It does</timemachine>. :)

>For definition order, a 3.x-only metaclass could be provided:
>
>class Days(enum.Enum, metaclass=enum.DefinitionOrder):
>    Monday = 1
>    Tuesday = 2
>    Wednesday = 3
>    Thursday = 4
>    Friday = 5
>    Saturday = 6
>    Sunday = 7

Yep, that's how it works.  From flufl.enum:

class IntEnumMetaclass(EnumMetaclass):
    # Define an iteration over the integer values instead of the attribute
    # names.
    def __iter__(cls):
        for key in sorted(cls._enums):
            yield getattr(cls, cls._enums[key])


IntEnum = IntEnumMetaclass(str('IntEnum'), (Enum,), {
    '__doc__': 'A specialized enumeration with values that are also integers.',
    '__value_factory__': IntEnumValue,
    })

-Barry
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