On 12/01/2012 11:28 AM, Brian van den Broek wrote: > On 1 December 2012 10:40, richard kappler <richkapp...@gmail.com> wrote: >> I'm working through Mark Lutz's "Python," reviewing the section on lists. I >> understand the list comprehension so far, but ran into a snag with the >> matrix. I've created the matrix M as follows: >> >> M = [[1, 2, 3[, [4, 5, 6], [7, 8, 9]] >> >> then ran through the various comprehension examples, including: >> >> diag = [M[i][i] for i in [0, 1, 2]] >> >> which, of course, gave me [1, 5, 9]. >> >> Then I tried creating revdiag, wanting to return [3, 5, 7], tried several >> different ways, never quite got what I was looking for, so I'm looking for >> guidance as I'm stuck on this idea. Here's the various attempts I made and >> the tracebacks: > > Richard, > > It is good you copy and pasted everything I snipped. But, you typed in > the line defining M. Better to also copy paste that, as you typed it > in wrong :-) > > Here's one way that assumes of M only that it is an n-by-n matrix: > >>>> M = [[1, 2, 3], [4, 5, 6], [7, 8, 9]] >>>> for i in reversed(range(len(M))): > M[i][i] > > > 9 > 5 > 1 >
The only catch to that is it's not what he wants. He said he wants 3, 5, 7 -- DaveA _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor