python multiply two matrices code example

Example 1: python numpy multiply matrices

a = np.array([[-6, 1], [1, 1]])
b = np.array([[0], [8]])

c = a.dot(b) # multiply matrice a and b

Example 2: how to multiply matrices in python

# Program to multiply two matrices using list comprehension

# 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 = [[sum(a*b for a,b in zip(X_row,Y_col)) for Y_col in zip(*Y)] for X_row in X]

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]]

Example 4: how to multiply matrices in python

>>> a = np.ones([9, 5, 7, 4])
>>> c = np.ones([9, 5, 4, 3])
>>> np.dot(a, c).shape
(9, 5, 7, 9, 5, 3)
>>> np.matmul(a, c).shape
(9, 5, 7, 3)
>>> # n is 7, k is 4, m is 3