In Python, how do I iterate over a dictionary in sorted key order?

Question

There\'s an existing function that ends in the following, where d is a dictionary:

return d.iteritems()

that returns an unsort

Answer 1

>>> import heapq
>>> d = {"c": 2, "b": 9, "a": 4, "d": 8}
>>> def iter_sorted(d):
        keys = list(d)
        heapq.heapify(keys) # Transforms to heap in O(N) time
        while keys:
            k = heapq.heappop(keys) # takes O(log n) time
            yield (k, d[k])


>>> i = iter_sorted(d)
>>> for x in i:
        print x


('a', 4)
('b', 9)
('c', 2)
('d', 8)

This method still has an O(N log N) sort, however, after a short linear heapify, it yields the items in sorted order as it goes, making it theoretically more efficient when you do not always need the whole list.