On 29 sep, 14:17, Steven D'Aprano <st...@remove-this- cybersource.com.au> wrote: > On Tue, 28 Sep 2010 20:11:51 +0100, Rog wrote: > > On Tue, 28 Sep 2010 11:59:08 -0700, geremy condra wrote: > > >> On Tue, Sep 28, 2010 at 11:44 AM, Rog <r...@pynguins.com> wrote: > >>> Hi all, > >>> Have been grappling with a list problem for hours... a = [2, 3, 4, > >>> 5,.....] > >>> b = [4, 8, 2, 6,.....] > >>> Basicly I am trying to place a[0], b[0] in a seperate list IF a[2] and > >>> b[2] is present. > >>> I have tried sets, zip etc with no success. I am tackling Euler > >>> projects with Python 3.1, with minimal knowledge, and having to tackle > >>> the language as I progress. Enjoyable frustration :) > > >> I'm not clear on what your actual problem is, could you restate it? > > >> It sounds like you want to copy the ith element out of a and b into > >> some other list- call it c- when the (i+2)th element meets some > >> condition. What's the condition? > > >> Geremy Condra > > > The condition is that the i-th element is inverted, but not equal. eg > > 4,2 - 2,4 , 34,5 - 5,34 etc. > > Hope that is clearer. > > Clear as mud. > > Perhaps you should given an example. Given input > > a = [2, 3, 4, 5, 6, 7] > b = [4, 8, 2, 6, 10, 42] > > what output are you expecting,
AFAICT, the OP expects [2, 4] in this case, but it's not clear what he'd expect for let's say: a = [2, 3, 21, 4, 5, 6, 7] b = [4, 8, 22, 2, 6, 10, 42] (the 'reversed' pair is at i+3, not i+2) or a = [0, 2, 3, 4, 5, 6, 7] b = [3, 4, 8, 2, 6, 10, 42] (the first pair is at pos 1, not 0) or a = [2, 3, 4, 8, 6, 7] b = [4, 8, 2, 3, 10, 42] (there's a second 'non-reversed/reversed' match at positions resp. 1 & 3) -- http://mail.python.org/mailman/listinfo/python-list