[Python-ideas] Automatic comparisons by default

[Raymond Hettinger]

On Mar 15, 2011, at 11:03 AM, Facundo Batista wrote:

> Two very related proposals:
> 
> 1. On "!=", if Python doesn't find __ne__, use "not __eq__()".
> 
> 2. On "<=", if Python doesn't find __le__, use "__eq__() or __lt__()".
> The same for ">=", of course.


It's a little more complicated than "if Python doesn't find ...".
In Python 3, object() already has __le,__, __gt__, __ge__, and __gt__,
so those methods always get found.   

You can use an identity check to see if those methods have been
overridden, but I think the only truly correct way to tell if one of the
rich comparison methods is defined is to call it and see whether
it returns NotImplemented.


Raymond