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

Ethan Furman ethan at stoneleaf.us
Thu Apr 25 22:18:47 CEST 2013

On 04/25/2013 11:44 AM, Barry Warsaw wrote:
> On Apr 23, 2013, at 03:44 PM, Antoine Pitrou wrote:
>> I'm having a problem with the proposed implementation. I haven't found
>> any mention of it, so apologies if this has already been discussed:
>>>>> from flufl.enum import *
>>>>> class C(Enum):
>> ...  a = 1
>> ...  b = 2
>> ...
>>>>> C.a.__class__
>> <class 'flufl.enum._enum.EnumValue'>
>>>>> isinstance(C.a, C)
>> False
>>>>> isinstance(C(1), C)
>> False
>> It would really be better if instances were actual instances of the
>> class, IMO.
> Ignore the single argument call syntax for Enums please.  As Eli pointed out,
> you have getitem syntax for this and the single argument call syntax is
> deprecated.  It will be removed in a future version of flufl.enum and need not
> appear in stdlib enum.  TOOWTDI.

For me, the getitem syntax on a class seems odd and the call syntax is TOOWTDI.

> C.a and C[1] return the same object, and it seems perfectly natural to me that
> this object is *not* an instance of the enum class.  In fact, it seems
> completely weird to me that C.a would be an instance of the enum class.  It
> seems very rare that a class has attributes that are instances of that class.
> It's not even easy to do with traditional syntax.
> class Foo:
>      a = Foo()
>      b = Foo()
>      c = Foo()

Obviously you need a metaclass in there.  ;)


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