[Python-ideas] A key parameter for heapq.merge

[Simon Sapin]

Hi,

According to its own documentation, the merge() function in the heapq 
module is similar to sorted(). However, it has none of the key and 
reverse parameters that sorted() has. I think they could be just as 
useful as in sorted().

http://docs.python.org/dev/library/heapq.html#heapq.merge
http://docs.python.org/dev/library/functions.html#sorted


First of all what do you think of the idea?

I’m working on a patch for a key parameter. I think it can be pretty 
straightforward, but I’ll measure if the "no key" case becomes slower 
(calls to lambda x: x) At worst we can always duplicate the loop.

However, I am not sure how to implement reverse. Not all values have an 
"opposite value" that reverses order, _nsmallest and _nlargest are quite 
different, and merge uses neither.


Anyway, if I get this to work, it will be my first contribution to 
CPython. I’m trying to follow the Developer’s guide, but is there 
something else I should be aware of?

http://docs.python.org/devguide/

Regards,
-- 
Simon Sapin