Question

I’m finding difficulting what exactly the doctest in the following code is looking for in the function.

Can someone make it more clear for me, please?

Question 14:

1. Write functions row_times_column and matrix_mult:

def row_times_column(m1, row, m2, column):
    """
      >>> row_times_column([[1, 2], [3, 4]], 0, [[5, 6], [7, 8]], 0)
      19
      >>> row_times_column([[1, 2], [3, 4]], 0, [[5, 6], [7, 8]], 1)
      22
      >>> row_times_column([[1, 2], [3, 4]], 1, [[5, 6], [7, 8]], 0)
      43
      >>> row_times_column([[1, 2], [3, 4]], 1, [[5, 6], [7, 8]], 1)
      50
    """
def matrix_mult(m1, m2):
   """
      >>> matrix_mult([[1, 2], [3,  4]], [[5, 6], [7, 8]])
      [[19, 22], [43, 50]]
      >>> matrix_mult([[1, 2, 3], [4,  5, 6]], [[7, 8], [9, 1], [2, 3]])
      [[31, 19], [85, 55]]
      >>> matrix_mult([[7, 8], [9, 1], [2, 3]], [[1, 2, 3], [4, 5, 6]])
      [[39, 54, 69], [13, 23, 33], [14, 19, 24]]
    """

Add your new functions to matrices.py and be sure it passes the
doctests above.

Answer 1

Its asking you to implement some matrix multiplication methods.

In the first one, given a matrix, multiply the row of m1 x the column of m2. The first one given is:

1 2   times   5 6
3 4           7 8

but we only want row 0 times col 0, so it would be

[1 2] x 5 
        7

= 5+14 = 19. And so on for the others…

The second function wants a full matrix multiplication. See http://en.wikipedia.org/wiki/Matrix_multiplication