function for counting items in a sequence

[Steven Bethard]

Alex Martelli wrote:
 > If we had a "turn sequence into bag" function somewhere
 > (and it might be worth having it for other reasons):
 >
 > def bagit(seq):
 >   import collections
 >   d = collections.defaultdict(int)
 >   for x in seq: d[x] += 1
 >   return d

I use this function all the time -- I call it dicttools.count().  I'd 
love to see this appear in the collections module or somewhere else in 
the stdlib.

STeVe