How to multiply matrices in python

user51043

Code: Python

2021-02-26 00:38:55

# 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)

1

Really Urgent

Code: Python

2021-07-08 23:55:42

# 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]

0

ismailcem

Code: Python

2021-07-09 09:25:02

# Program to multiply two matrices (vectorized implementation) 
  
# Program to multiply two matrices (vectorized implementation) 
import numpy as np 
# take a 3x3 matrix 
A = [[12, 7, 3], 
    [4, 5, 6], 
    [7, 8, 9]] 
  
# take a 3x4 matrix 
B = [[5, 8, 1, 2], 
    [6, 7, 3, 0], 
    [4, 5, 9, 1]] 
  
# result will be 3x4 
  
result= [[0,0,0,0], 
        [0,0,0,0], 
        [0,0,0,0]] 
  
result = np.dot(A,B) 
  
for r in result: 
    print(r)

0

Ayush

Code: Python

2021-03-01 16:46:27

>>> 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

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