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