product of two matrices in python code example

Example 1: matrix multiplication in python

# Program to multiply two matrices using nested loops

# 3x3 matrix
X = [[12,7,3],
    [4 ,5,6],
    [7 ,8,9]]
# 3x4 matrix
Y = [[5,8,1,2],
    [6,7,3,0],
    [4,5,9,1]]
# result is 3x4
result = [[0,0,0,0],
         [0,0,0,0],
         [0,0,0,0]]

# iterate through rows of X
for i in range(len(X)):
   # iterate through columns of Y
   for j in range(len(Y[0])):
       # iterate through rows of Y
       for k in range(len(Y)):
           result[i][j] += X[i][k] * Y[k][j]

for r in result:
   print(r)

Example 2: addition of two matrices in python

num = [2, 3, 4], [5, 6, 7]
num2 = [8, 9, 10], [11, 12, 13]
num3 = [0, 0, 0], [0, 0, 0]
for i in range(len(num)):
    print(num[i])
for i in range(len(num)):
    print(num2[i])
print()
for i in range (len(num)):
    for j in range(len(num)+1):
        num3[i][j] = num[i][j] + num2[i][j]

for i in range(len(num3)):
    print(num3[i])

Example 3: how to add two matrices in python

matrix1 = [[0, 1, 2], [3, 4, 5], [6, 7, 8]]
matrix2 = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]


def addTheMatrix(matrix1, matrix2):
    matrix1Rows = len(matrix1)
    matrix2Rows = len(matrix2)
    matrix1Col = len(matrix1[0])
    matrix2Col = len(matrix2[0])

    #base case
    if(matrix1Rows != matrix2Rows or matrix1Col != matrix2Col):
        return "ERROR: dimensions of the two arrays must be the same"

    #make a matrix of the same size as matrix 1 and matrix 2
    matrix = []
    rows = []

    for i in range(0, matrix1Rows):
        for j in range(0, matrix2Col):
            rows.append(0)
        matrix.append(rows.copy())
        rows = []

    #loop through the two matricies and the summation should be placed in the
    #matrix
    for i in range(0, matrix1Rows):
        for j in range(0, matrix2Col):
            matrix[i][j] = matrix1[i][j] + matrix2[i][j]
            
    return matrix



print(addTheMatrix(matrix1, matrix2)) 
#output = [[1, 3, 5], [7, 9, 11], [13, 15, 17]]