What's the idiomatic Python equivalent to Django's 'regroup' template tag?

Question

http://docs.djangoproject.com/en/dev/ref/templates/builtins/#regroup

I can think of a few ways of doing it with loops but I'd particularly like to know if there is a neat one-liner.

Answer 1

Combine itertools.groupby with operator.itemgetter to get a pretty nice solution:

from operator import itemgetter
from itertools import groupby

key = itemgetter('gender')
iter = groupy(sorted(people, key=key), key=key)

for gender, people in iter:
    print '===', gender, '==='
    for person in people:
        print person

Answer 2

itertools.groupby