matrix multiplication in python

1# input two matrices of size n x m 
2matrix1 = [[12,7,3], 
3        [4 ,5,6], 
4        [7 ,8,9]] 
5matrix2 = [[5,8,1], 
6        [6,7,3], 
7        [4,5,9]] 
8  
9res = [[0 for x in range(3)] for y in range(3)]  
10  
11# explicit for loops 
12for i in range(len(matrix1)): 
13    for j in range(len(matrix2[0])): 
14        for k in range(len(matrix2)): 
15  
16            # resulted matrix 
17            res[i][j] += matrix1[i][k] * matrix2[k][j] 
18  
19print (res) 
20

1# Program to multiply two matrices using nested loops
2
3# 3x3 matrix
4X = [[12,7,3],
5    [4 ,5,6],
6    [7 ,8,9]]
7# 3x4 matrix
8Y = [[5,8,1,2],
9    [6,7,3,0],
10    [4,5,9,1]]
11# result is 3x4
12result = [[0,0,0,0],
13         [0,0,0,0],
14         [0,0,0,0]]
15
16# iterate through rows of X
17for i in range(len(X)):
18   # iterate through columns of Y
19   for j in range(len(Y[0])):
20       # iterate through rows of Y
21       for k in range(len(Y)):
22           result[i][j] += X[i][k] * Y[k][j]
23
24for r in result:
25   print(r)
26

1>>> a = np.array([[ 5, 1 ,3], 
2                  [ 1, 1 ,1], 
3                  [ 1, 2 ,1]])
4>>> b = np.array([1, 2, 3])
5>>> print a.dot(b)
6array([16, 6, 8])