Python program to multiply two matrices

Given two matrix the task is that we will have to create a program to multiply two matrices in python.

Examples:

Input : X = [[1, 7, 3], [3, 5, 6], [6, 8, 9]] Y = [[1, 1, 1, 2], [6, 7, 3, 0], [4, 5, 9, 1]] Output : [55, 65, 49, 5] [57, 68, 72, 12] [90, 107, 111, 21]

**Using Simple Nested Loops**

In this program we have to use nested for loops to iterate through each row and each column.

`# Program to multiply two matrices using nested loops` ` ` `# 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 ` `=` `[[` `0` `, ` `0` `, ` `0` `, ` `0` `],` ` ` `[` `0` `, ` `0` `, ` `0` `, ` `0` `],` ` ` `[` `0` `, ` `0` `, ` `0` `, ` `0` `]]` ` ` `# iterating by row of A` `for` `i ` `in` `range` `(` `len` `(A)):` ` ` ` ` `# iterating by coloum by B ` ` ` `for` `j ` `in` `range` `(` `len` `(B[` `0` `])):` ` ` ` ` `# iterating by rows of B` ` ` `for` `k ` `in` `range` `(` `len` `(B)):` ` ` `result[i][j] ` `+` `=` `A[i][k] ` `*` `B[k][j]` ` ` `for` `r ` `in` `result:` ` ` `print` `(r)` |

Output:

[114, 160, 60, 27] [74, 97, 73, 14] [119, 157, 112, 23]

**Method 2:** Matrix Multiplication Using Nested List. We use zip in Python.

`# Program to multiply two matrices using list comprehension` ` ` `# 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 ` `=` `[[` `sum` `(a ` `*` `b ` `for` `a, b ` `in` `zip` `(A_row, B_col)) ` ` ` `for` `B_col ` `in` `zip` `(` `*` `B)]` ` ` `for` `A_row ` `in` `A]` ` ` `for` `r ` `in` `result:` ` ` `print` `(r)` |

Output:

[114, 160, 60, 27] [74, 97, 73, 14] [119, 157, 112, 23]

**Method 3:** Matrix Multiplication (Vectorized implementation).

`# 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)` |

Output:

[114, 160, 60, 27] [74, 97, 73, 14] [119, 157, 112, 23]

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