[Visualpython-users] Toy program for variable size checkers grid

Hi,

I 'm a new vpython user, trying to get familiar with working with 3D 
objects. In particular, I'm trying to understand how I can make an 
arbitrary checkers board with N rows and M columns. Unfortunately, 
taking the following sample code from 
http://www.vpython.org/contents/docs/visual/materials.html

/from visual import *
checkerboard = ( (0,1,0,1),
                  (1,0,1,0),
                  (0,1,0,1),
                  (1,0,1,0) )
tex = materials.texture(data=checkerboard,
                      mapping="rectangular",
                      interpolate=False)
box(axis=(0,0,1), color=color.cyan, material=tex)/

and just adding some extra rows, columns, or both to the checkerboard 
variable does not work.
Could you please give me some pointers on this?

Thanks,
Andreas