Yielding from sorted iterators in sorted order in Python?

Question

Is there a better way to merge/collate a bunch of sorted iterators into one so that it yields the items in sorted order? I think the code below works but I feel like there i

Answer 1

yes, you want heapq.merge() which does exactly one thing; iterate over sorted iterators in order

def sortkey(row):
    return (row[5], row)

def unwrap(key):
    sortkey, row = key
    return row

from itertools import imap
FILE_LIST = map(file, ['foo.csv', 'bar.csv'])
input_iters = imap(sortkey, map(csv.csvreader, FILE_LIST))
output_iter = imap(unwrap, heapq.merge(*input_iters))