On Mar 16, 2010, at 9:41 AM, Guido van Rossum wrote:
I'd say if you're not going to forward-port this to Python 3, it shouldn't go into Python 2 -- in that case it would make more sense to me to back-port the exception-raising behavior.
Python 3 doesn't need it because it is possible to not give a result at all. Python 2 does need it because we have to give *some* result.
Also supporting comparisons but not other mixed operations is going to be confusing. If you are sticking to that behavior I think mixed comparisons should also be ruled out.
The difference is that mixed comparisons currently do give a result, but one that is non-sensical. The proposal is a make in give a meaningful result, not as an extra feature, but in an effort to not be wrong. Since 2.x has to give a result, we should make it useful. Since 3.x does not make the comparison, it is okay to punt. Raymond