[Python-Dev] PEP 557: Data Classes

[Eric V. Smith]

On 9/11/2017 6:28 PM, Guido van Rossum wrote:
> 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).

So if we don't do enums, I think the choices are ints, strs, or maybe 
True/False/None. Do you have a preference here?

If int or str, I assume we'd want module-level constants.

I like the name compare=, and 3 values makes sense: None, Equality, Ordered.

Eric.

> 
> On Mon, Sep 11, 2017 at 3:16 PM, Ethan Furman <ethan at stoneleaf.us 
> <mailto: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 <http://python.org/%7Eguido>)
> 
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