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

2013年4月12日 08:41:20 -0700 

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 <[email protected]> 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~
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