How to replace a value in a matrix by index

Question

Let's say I have a 4X4 matrix containing value from 1 to 20. If I want the element at line 2 column 3 to be equal to 100, how can I do this?

Answer 1

First, import the numpy library:

import numpy as np

Then, create the matrix:

matrix = np.array([[1,2,3], [4,5,6], [7,8,9]])

Finally, use the index to replace the value:

matrix[1,2] = 10

The new matrix will be:

[[ 1  2  3]
 [ 4  5 10]
 [ 7  8  9]]