Raymond Hettinger <pyt...@rcn.com> writes: > If you're assuming a consistent sort-order (transitivity, not > evolving over time, etc), then the cmp method and key method > are mathematically equivalent (you could always do a compare > sort first, record the order produced, and assign the position > number as a key function)
But that is an efficiency hit. > If you're starting point is a cmp function (for instance, > asking a dating service member whether they prefer > mate x to mate y), then having to convert to a key function > can be inconvenient. Well, the issue there is that the comparison function may not be transitive. Maybe you really want a topological sort for that. > All that being said, for many everyday uses, a key function is > simpler to write and faster to run than a cmp function approach. I still have never understood why cmp was removed. Sure, key is more convenient a lot (or maybe most) of the time, but it's not always. -- http://mail.python.org/mailman/listinfo/python-list
