#In python, matrices are represented as follows:
 identity = [[1, 0],
             [0, 1]]

 #To add matrices:
 matrix_one = [[2, 3, 4], 
       [10,11,12], 
       [6,7,8]]

 matrix_two = [[3, 9, 12],
       [9,11,14], 
       [1,7,16]]

 matrix_three= [[0,0,0],
        [0,0,0],
        [0,0,0]]

 matrix_length = len(matrix_one)

 for i in range(len(matrix_one)):
 for k in range(len(matrix_two)):
         matrix_three[i][k] = matrix_one[i][k] + matrix_two[i][k]

 print(matrix_three)


 #To multiply matrices:
 matrix_one = [[2, 3, 4], 
       [10,11,12], 
       [6,7,8]]

 matrix_two = [[3, 9, 12],
       [9,11,14], 
       [1,7,16]]

 matrix_three= [[0,0,0],
        [0,0,0],
        [0,0,0]]

 matrix_length = len(matrix_one)

 for i in range(len(matrix_one)):
     for k in range(len(matrix_two)):
         matrix_three[i][k] = matrix_one[i][k] * matrix_two[i][k]

 print(matrix_three)

 #Using a NumPy array
 import numpy as np

 matrix_one = np.array([[2, 3, 4], [10,11,12], [6,7,8]])
 matrix_two = np.array([[3, 9, 12], [9,11,14], [1,7,16]])

 matrix_three = matrix_one + matrix_two
 matrix_four = matrix_one*matrix_two