list slicing from: https://stackoverflow.com/questions/9027862/what-does-listxy-do
#It slices
x[startAt:endBefore:skip]
#if you use skip = 2, every other element the list beginning at startAt and ending at #endBefore will be selected. [Remember: indices live BETWEEN list elements]
T#o see this, enter
x = range(100)
#at the Python prompt. Then try these things
x[::2]
x[::3]
x[10:40:6]