Open In App

Python Program to multiply two matrices

Improve
Improve
Like Article
Like
Save
Share
Report

Given two matrices, the task to multiply them. Matrices can either be square or rectangular.

Examples: 

Input : mat1[][] = {{1, 2}, 
                   {3, 4}}
        mat2[][] = {{1, 1}, 
                    {1, 1}}
Output : {{3, 3}, 
          {7, 7}}
Input : mat1[][] = {{2, 4}, 
                    {3, 4}}
        mat2[][] = {{1, 2}, 
                    {1, 3}}       
Output : {{6, 16}, 
          {7, 18}}

Multiplication of Square Matrices : 
The below program multiplies two square matrices of size 4*4, we can change N for different dimensions. 

Python3




# 4x4 matrix multiplication using Python3
# Function definition
def matrix_multiplication(M, N):
    # List to store matrix multiplication result
    R = [[0, 0, 0, 0],
        [0, 0, 0, 0],
        [0, 0, 0, 0],
        [0, 0, 0, 0]]
 
    for i in range(0, 4):
        for j in range(0, 4):
            for k in range(0, 4):
                R[i][j] += M[i][k] * N[k][j]
 
    for i in range(0, 4):
        for j in range(0, 4):
            # if we use print(), by default cursor moves to next line each time,
            # Now we can explicitly define ending character or sequence passing
            # second parameter as end ="<character or string>"
            # syntax: print(<variable or value to print>, end ="<ending with>")
            # Here space (" ") is used to print a gap after printing
            # each element of R
            print(R[i][j], end =" ")
        print("
", end ="")
 
# First matrix. M is a list
M = [[1, 1, 1, 1],
    [2, 2, 2, 2],
    [3, 3, 3, 3],
    [4, 4, 4, 4]]
 
# Second matrix. N is a list
N = [[1, 1, 1, 1],
    [2, 2, 2, 2],
    [3, 3, 3, 3],
    [4, 4, 4, 4]]
     
# Call matrix_multiplication function
matrix_multiplication(M, N)
 
# This code is contributed by Santanu


Output

Result matrix is 
10 10 10 10 
20 20 20 20 
30 30 30 30 
40 40 40 40

Time complexity: O(n3). It can be optimized using Strassen’s Matrix Multiplication

Auxiliary Space: O(n2)

Multiplication of Rectangular Matrices : 
We use pointers in C to multiply to matrices. Please refer to the following post as a prerequisite of the code.
How to pass a 2D array as a parameter in C? 

Python3




# Python3 program to multiply two
# rectangular matrices
 
# Multiplies two matrices mat1[][]
# and mat2[][] and prints result.
# (m1) x (m2) and (n1) x (n2) are
# dimensions of given matrices.
def multiply(m1, m2, mat1,
             n1, n2, mat2):
 
    res = [[0 for x in range(n2)]
              for y in range (m1)]
     
    for i in range(m1):
        for j in range(n2):
            res[i][j] = 0
            for x in range(m2):           
                res[i][j] += (mat1[ i][x] *
                              mat2[ x][j])
            
    for i in range(m1):
        for j in range(n2):     
            print (res[i][j],
                   end = " ")       
        print ()
 
# Driver code
if __name__ == "__main__":
   
    mat1 = [[2, 4], [3, 4]]
    mat2 = [[1, 2], [1, 3]]
    m1, m2, n1, n2 = 2, 2, 2, 2
   
    # Function call
    multiply(m1, m2, mat1,
             n1, n2, mat2)
     
# This code is contributed by Chitranayal


 
 

Output

6 16 
7 18

 

Time complexity: O(n3). It can be optimized using Strassen’s Matrix Multiplication

 

Auxiliary Space: O(m1 * n2)

Please refer complete article on Program to multiply two matrices for more details!
 



Last Updated : 24 Feb, 2022
Like Article
Save Article
Previous
Next
Share your thoughts in the comments
Similar Reads