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

[Ethan Furman]

On 04/12/2013 08:02 AM, Barry Warsaw wrote:
> On Apr 12, 2013, at 03:31 PM, Dirkjan Ochtman wrote:
>
>> On Fri, Apr 12, 2013 at 2:55 PM, Eli Bendersky <eliben at gmail.com> wrote:
>>> Ordered comparisons between enumeration values are *not* supported.  Enums
>>> are
>>> not integers (but see `IntEnum`_ below)::
>>>
>>>      >>> Colors.red < Colors.blue
>>>      Traceback (most recent call last):
>>>      ...
>>>      NotImplementedError
>>>      >>> Colors.red <= Colors.blue
>>>      Traceback (most recent call last):
>>>      ...
>>>      NotImplementedError
>>>      >>> Colors.blue > Colors.green
>>>      Traceback (most recent call last):
>>>      ...
>>>      NotImplementedError
>>>      >>> Colors.blue >= Colors.green
>>>      Traceback (most recent call last):
>>>      ...
>>>      NotImplementedError
>>
>> I like much of this PEP, but the exception type for this case seems
>> odd to me. Wouldn't a TypeError be more appropriate here?
>>
>> Somewhat like this:
>>
>>>>> 'a' - 'b'
>> Traceback (most recent call last):
>>   File "<stdin>", line 1, in <module>
>> TypeError: unsupported operand type(s) for -: 'str' and 'str'
>
> Interesting.  I'm having a hard time articulating why, but NotImplementedError
> just feels more right to me in this case.

NotImplemented makes it seem like we could implement it in a subclass -- is this true?

Also, for a more direct comparison:

--> 'a' < 1
Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
TypeError: unorderable types: str() < int()

I would think this is the more appropriate exception and text to use.

--
~Ethan~