bags? 2.5.x?

[Paul Rubin]

Dan Stromberg <dstromberglists at gmail.com> writes:
> > * Is the feature useful for the broad mass?
> 
> Yes, probably, at least if this kind of feature's inclusion in other 
> languages and my two recent needs for it are any indication.  In other 
> languages, they are sometimes called bags or multisets.

I use defaultdict(int) all the time, but it's been fairly rare
to want to do set operations (union, intersection, difference) on 
these.  I'm not even sure what the intersection should mean.