[Python-Dev] PEP 557: Data Classes

[Guido van Rossum]

Oddly I don't like the enum (flag names get too long that way), but I do
agree with everything else Barry said (it should be a trivalue flag and
please don't name it cmp).

On Mon, Sep 11, 2017 at 3:16 PM, Ethan Furman <ethan at stoneleaf.us> wrote:

> On 09/11/2017 03:00 PM, Barry Warsaw wrote:
>
>> On Sep 10, 2017, at 20:08, Nathaniel Smith wrote:
>>
>>>
>>> I've sometimes wished that attrs let me control whether it generated
>>> equality methods (eq/ne/hash) separately from ordering methods (lt/gt/...).
>>> Maybe the cmp= argument should take an enum with options
>>> none/equality-only/full?
>>>
>>
>> I have had use cases where I needed equality comparisons but not ordered
>> comparisons, so I’m in favor of the option to split them.  (atm, I can’t
>> bring up a specific case, but it’s not uncommon.)
>>
>> Given that you only want to support the three states that Nathaniel
>> describes, I think an enum makes the most sense, and it certainly would
>> read well.  I.e. there’s no sense in supporting the ordered comparisons and
>> not equality, so that’s not a state that needs to be represented.
>>
>> I’d make one other suggestion here: please let’s not call the keyword
>> `cmp`.  That’s reminiscent of Python 2’s `cmp` built-in, which of course
>> doesn’t exist in Python 3.  Using `cmp` is just an unnecessarily
>> obfuscating abbreviation.  I’d suggest just `compare` with an enum like so:
>>
>> enum Compare(enum.Enum):
>>      none = 1
>>      unordered = 2
>>      ordered = 3
>>
>
> I like the enum idea (suprise! ;) but I would suggest "equal" or
> "equivalent" instead of "unordered"; better to say what they are rather
> than what they are not.
>
> --
> ~Ethan~
>
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-- 
--Guido van Rossum (python.org/~guido)
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