How to Perform Matrix Multiplication of given dimension in Python

In this Python tutorial, we will learn how to perform matrix multiplication in Python of any given dimension.

MATRIX MULTIPLICATION in Python

Matrix multiplication is the multiplication of two matrices.

The necessary condition:

  • R2(Number of Rows of the Second Matrix) = C1(Number of Columns of the First Matrix)
  • Number of Rows of the Product Matrix =R1(Number of Rows of First Matrix)
  • Number of Columns of the Product Matrix = C2(Number of Columns of the Second Matrix)

 

MATRIX MULTIPLICATION in Python

From the above conditions and the image we can understand that:



[A](m,n) X [B](n,s) = [P](m,s)

where

  • m is the number of rows of A
  • n is the number of columns of A = number of rows of B
  • s is the number of columns of B

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Let’s take a look at the code snippet.

Python program for matrix multiplication

r1=int(input("Enter number of Rows of Matrix A: "))
c1=int(input("Enter number of Columns of Matrix A: "))
A=[[0 for i in range(c1)] for j in range(r1)] #initialize matrix A
print("Enter Matrix Elements of A:")
#input matrix A
for i in range(r1):
    for j in range(c1):
        x=int(input())
        A[i][j]=x
r2=int(input("Enter number of Rows of Matrix B: "))
c2=int(input("Enter number of Columns of Matrix B: "))
B=[[0 for i in range(c2)] for j in range(r2)] #initialize matrix B
print("Enter Matrix Elements of B:")
#input matrix B
for i in range(r2):
    for j in range(c2):
        x=int(input())
        B[i][j]=x
if(c1==r2): #if no. of columns of matrix A is equal to no. of rows of matrix B
    P=[[0 for i in range(c2)] for j in range(r1)] #initialize product matrix
    for i in range(len(A)):
        for j in range(c2):
            for k in range(len(B)):
                P[i][j]=P[i][j]+(A[i][k]*B[k][j]) #multiplication
    #print the product matrix
    print("Product of Matrices A and B: ")
    for i in range(r1):
        for j in range(c2):
            print(P[i][j],end=" ")
        print()
else: #if no. of columns of matrix A isn't equal to no. of rows of matrix B
    print("Matrix Multiplication is not possible.")

OUTPUT 1:

Enter number of Rows of Matrix A: 3
Enter number of Columns of Matrix A: 3
Enter Matrix Elements of A:
1
2
3
4
5
6
7
8
9
Enter number of Rows of Matrix B: 3
Enter number of Columns of Matrix B: 2
Enter Matrix Elements of B:
2
4
6
8
1
3
Product of Matrices A and B: 
17 29 
44 74 
71 119

Here, the dimension of matrix A is 3X3. And the matrix B is of 3X2 dimension. Thus product matrix is 3X2.

OUTPUT 2:

Enter number of Rows of Matrix A: 4
Enter number of Columns of Matrix A: 3
Enter Matrix Elements of A:
4
8
6
7
8
2
1
4
5
6
7
3
Enter number of Rows of Matrix B: 3
Enter number of Columns of Matrix B: 2
Enter Matrix Elements of B:
7
5
6
4
3
3
Product of Matrices A and B: 
94 70 
103 73 
46 36 
93 67

The dimension of the Product matrix = (Number of rows of A) X (Number of columns of B)

Output 3:

Enter number of Rows of Matrix A: 3
Enter number of Columns of Matrix A: 3
Enter Matrix Elements of A:
7
8
6
9
4
3
5
1
2
Enter number of Rows of Matrix B: 2
Enter number of Columns of Matrix B: 2
Enter Matrix Elements of B:
4
5
2
6
Matrix Multiplication is not possible.

In this result, the number of rows of matrix B is not equal to the number of columns of matrix A. Thus the message shows that the matrix multiplication is not possible.

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