Hi again, Thanks for your comments they are really appreciated.
Alan, yes you are right, there is no need to use S, A_Len works the same way. Beginner mistake The dictionary way seems to be way better than my idea, will give it a try. And Danny, your CA is very nice. Do you know a better way to do this? if i < A_Len-1: a = A_List[i-1] b = A_List[i] c = A_List[i+1] else: a = A_List[i-1] b = A_List[i] c = A_List[0] if I dont do this I get the following error: c = A_List[i+1] IndexError: list index out of range I have the impression that this can be done in a less clunky way. Again thanks for your comments. : ) Best Regards, Carlos. _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor