MRAB wrote: > >>> a = [(4, 1), (7, 3), (3, 2), (2, 4)] > >>> b = [2, 4, 1, 3] > >>> d = dict((v, k) for k, v in a) > >>> c = [(d[s], s) for s in b] > >>> c > [(3, 2), (2, 4), (4, 1), (7, 3)] ah, that is more efficient than the suggestions i posted. andrew