Joining a set of ordered-integer yielding Python iterators

Question

Here is a seemingly simple problem: given a list of iterators that yield sequences of integers in ascending order, write a concise generator that yields only the integers th

Answer 1

import heapq, itertools
def intersect(*its):
    for key, values in itertools.groupby(heapq.merge(*its)):
        if len(list(values)) == len(its):
            yield key

>>> list(intersect(*postings))
[100, 322]