1.  >>> rows = 4
2.  >>> cols = 2
3.  >>> twoDim = [ ([0] * cols) for row in range(rows) ]
4.  >>> twoDim
5.  [[0, 0], [0, 0], [0, 0], [0, 0]]
6.  >>> twoDim[0][0] = 45
7.  >>> twoDim[0][1] = 50
8.  >>> twoDim
9.  [[45, 50], [0, 0], [0, 0], [0, 0]]
10. >>> twoDim[3][0] = 20
11. >>> twoDim
12. [[45, 50], [0, 0], [0, 0], [20, 0]]
13. >>> print(len(twoDim))
14. 4
15. >>> print(len(twoDim[0]))
16. 2
