On Wed, 8 Sep 2010 13:55:50 -0500 Jonno <jonnojohn...@gmail.com> wrote:
> I know that I can index into a list of lists like this: > a=[[1,2,3],[4,5,6],[7,8,9]] > a[0][2]=3 > a[2][0]=7 > > but when I try to use fancy indexing to select the first item in each > list I get: Let me write out in words what you're doing, and it should become clear: > a[0][:]=[1,2,3] Here you're making a list of all elements of the first element of a. > a[:][0]=[1,2,3] > And here you're selecting the first element of all elements of a. Huh. Not quite as clear as I hoped. But ponder on this for a few moments. It'll dawn on you eventually. > Why is this and is there a way to select [1,4,7]? zip(*a)[0] (or rather list(zip(*a)[0]), if you definitely need a list and not a tuple) /W -- INVALID? DE! -- http://mail.python.org/mailman/listinfo/python-list
