On Sat, Jul 18, 2009 at 8:45 PM, Raymond Hettinger <python@rcn.com> wrote:

On Jul 17, 2009, at 6:54 PM, Michael Lenzen wrote:

In a nutshell, I want to add 2 new classes (and respective frozen varients) to the collections module, namely a bag (multiset) class and a setlist (ordered set/unique list) class. I know this has been floated before, but I think it merits more consideration.

FWIW, my goal for the collections module is to keep it relatively small and not to include every variant someone can think of. We've already rejected red-black trees, pairing heaps, and blist (which is a list variant that allows fast insertions).

Michael Lenzen:

If you're interested in maintaining a more extensive collections module on PyPi, I'd be happy to collaborate with you as the author of 2 of the 3 aforementioned rejected data structures. :-)

In addition to pairing heaps (deprecated) and blist (on PyPi), I've also got a few other data structures that may or may not interest you:
- HeapDict (on PyPi): a dictionary where .popitem() returns the item with the lowest value
- LRU: a dictionary that maintains hard references to the most recently used n items and weak references to the rest
- MultiValueDict: x[5] = 1, x[5] = 2, print x[5] => set([1,2])
- WeakRefSet: the set analog to a WeakRefDict