MRAB wrote:
Kottiyath wrote:Hi, I have 2 lists a = [(4, 1), (7, 3), (3, 2), (2, 4)] b = [2, 4, 1, 3]Now, I want to order _a_ (a[1]) based on _b_. i.e. the second element in tuple should be the same as b. i.e. Output would be [(3, 2), (2, 4), (4, 1), (7, 3)] I did the same as follows:l = len(a) * [None] for (k, v) in a:... for i, e in enumerate(b): ... if e == v: ... l[i] = (k, v) This works, but the code -for python- looks very kludgy. I thought for ~2 hours to see whether I can do it in a line or 2, but I cannot seem to find a mechanism. Can someone help me out?How about: >>> 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)] Understanding how it works is left as an exercise for the reader. :-)
Actually, a more general solution is: >>> a = [(4, 1), (7, 3), (3, 2), (2, 4)] >>> b = [2, 4, 1, 3] >>> d = dict((t[1], t) for t in a) >>> c = [d[s] for s in b] >>> c [(3, 2), (2, 4), (4, 1), (7, 3)] -- http://mail.python.org/mailman/listinfo/python-list
