Guido rethinking removal of cmp from sort method

[Antoon Pardon]

On Wed, Mar 23, 2011 at 05:51:07PM +0100, Stefan Behnel wrote:
> >>
> >>You can use a stable sort in two steps for that.
> >
> >Which isn't helpfull if where you decide how they have to be sorted is
> >not the place where they are actually sorted.
> >
> >I have a class that is a priority queue. Elements are added at random but
> >are removed highest priority first. The priority queue can have a key or
> >a cmp function for deciding which item is the highest priority. It
> >can also take a list as an initializor, which will then be sorted.
> >
> >So this list is sorted within the class but how it is sorted is decided
> >outside the class. So I can't do the sort in multiple steps.
> 
> That sounds more like a use case for heap sort than for Python's
> builtin list sort. See the heapq module.

No the heapq module is not usefull. The heapq functions don't have a
cmp, or a key argument. So you can't use it with priorities that differ
from the normal order of the items.

For the rest is solving this particular problem beside the point. It
was just an illustration of how, sorting a list can be done in a place
differently from where one decides the order-relation of the items in
the list. That fact makes it less obvious to use multiple steps in the
place where you actually sort.