[Python-Dev] Deprecated __cmp__ and total ordering

[Michael Foord]

Raymond Hettinger wrote:
>
> [Mart Sõmermaa]
>>>> To provide total ordering without __cmp__ one has to implement all of
>>>>  __lt__, __gt__, __le__, __ge__, __eq__ and __ne__. However, in all
>>>> but a few cases it suffices only to provide a "real" implementation 
>>>> for
>>>> e.g. __lt__ and define all the other methods in terms of it as 
>>>> follows:
>
> [Raymond Hettinger]
>>> FWIW, I'm working on a solution for the problem using class decorators.
>>> The idea is that it would scan a class and fill-in missing methods 
>>> based
>>> on the ones already there.  That way, any one of the four ordering
>>> relations can be provided as a starting point and we won't have to
>>> annoint one like __lt__ as the one true underlying method.
>>>
>>> When it's ready, I'll bring it to python-dev for discussion.
>
> [Michael Foord]
>> Is there something you don't like about this one: 
>> http://code.activestate.com/recipes/576529/
>
> Yes, that recipe has the basic idea!
>

It was originally written after you issued a challenge at PyCon UK last 
year.

> I think the implementation can be cleaned-up quite a bit
> and it can be made as fast as hand-written code (not
> the setup time, but the actual introduced method).

OK

I'll take it back to Christian and Menno and see what we can come up with.

Michael


>
>
> Raymond 


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