[Python-Dev] PEP 435 - requesting pronouncement

[Eli Bendersky]

On Sat, May 4, 2013 at 4:27 PM, Tim Delaney <timothy.c.delaney at gmail.com>wrote:

> Typo line 171: <Colro.blue: 3>
>
>
Fixed, thanks.



> One thing I'd like to be clear in the PEP about is whether enum_type and
> _EnumDict._enum_names should be documented, or whether they're considered
> implementation details.
>
>
No, they should not. Not only are they implementation details, they are
details of the *reference implementation*, not the actual stdlib module.
The reference implementation will naturally serve as a basis for the stdlib
module, but it still has to undergo a review in which implementation
details can change. Note that usually we do not document implementation
details of stdlib modules, but this doesn't prevent some people from using
them if they really want to.


> I'd like to make a subclass of Enum that accepts ... for auto-valued enums
> but that requires subclassing the metaclass and access to
> classdict._enum_names. I can get to enum_type via type(Enum), but
> _EnumDict._enum_names requires knowing the attribute. It would sufficient
> for my purposes if it was just documented that the passed classdict had a
> _enum_names attribute.
>
> In testing the below, I've also discovered a bug in the reference
> implementation - currently it will not handle an __mro__ like:
>
>
Thanks! Tim - did you sign the contributor CLA for Python? Since the
reference implementation is aimed for becoming the stdlib enum eventually,
we'd probably need you to sign that before we can accept patches from you.

Eli





> (<Enum 'AutoIntEnum'>, <Enum 'IntEnum'>, <class 'int'>, <Enum 'Enum'>,
> <class 'object'>)
>
> Apply the following patch to make that work:
>
> diff -r 758d43b9f732 ref435.py
> --- a/ref435.py Fri May 03 18:59:32 2013 -0700
> +++ b/ref435.py Sun May 05 09:23:25 2013 +1000
> @@ -116,7 +116,11 @@
>              if bases[-1] is Enum:
>                  obj_type = bases[0]
>              else:
> -                obj_type = bases[-1].__mro__[1] # e.g. (IntEnum, int,
> Enum, object)
> +                for base in bases[-1].__mro__:
> +                    if not issubclass(base, Enum):
> +                        obj_type = base
> +                        break
> +
>          else:
>              obj_type = object
>          # save enum items into separate mapping so they don't get baked
> into
>
> My auto-enum implementation (using the above patch - without it you can
> get the essentially the same results with class AutoIntEnum(int, Enum,
> metaclass=auto_enum).
>
> class auto_enum(type(Enum)):
>     def __new__(metacls, cls, bases, classdict):
>         temp = type(classdict)()
>         names = set(classdict._enum_names)
>         i = 0
>
>         for k in classdict._enum_names:
>             v = classdict[k]
>
>             if v is Ellipsis:
>                 v = i
>             else:
>                 i = v
>
>             i += 1
>             temp[k] = v
>
>         for k, v in classdict.items():
>             if k not in names:
>                 temp[k] = v
>
>         return super(auto_enum, metacls).__new__(metacls, cls, bases, temp)
>
> class AutoNumberedEnum(Enum, metaclass=auto_enum):
>     pass
>
> class AutoIntEnum(IntEnum, metaclass=auto_enum):
>     pass
>
> class TestAutoNumber(AutoNumberedEnum):
>     a = ...
>     b = 3
>     c = ...
>
> class TestAutoInt(AutoIntEnum):
>     a = ...
>     b = 3
>     c = ...
>
> print(TestAutoNumber, list(TestAutoNumber))
> print(TestAutoInt, list(TestAutoInt))
>
> ---------- Run ----------
> <Enum 'TestAutoNumber'> [<TestAutoNumber.a: 0>, <TestAutoNumber.b: 3>,
> <TestAutoNumber.c: 4>]
> <Enum 'TestAutoInt'> [<TestAutoInt.a: 0>, <TestAutoInt.b: 3>,
> <TestAutoInt.c: 4>]
>
> Tim Delaney
>
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