How do you retrieve element indexes in numpy?

You can use the numpy.where() function in numpy to get the index of elements that meet a certain condition. This function will return a tuple containing the indices of the elements that satisfy the condition.

For example, we have a numpy array called arr.

import numpy as np

arr = np.array([1, 2, 3, 4, 5])

We can use the numpy.where() function to obtain the indices of all elements greater than 2.

indexes = np.where(arr > 2)
print(indexes)

Output:

(array([2, 3, 4]),)

This indicates that the indices of the elements that meet the condition are 2, 3, and 4. If we want to directly access the index values instead of a tuple, we can use the first element of numpy.where().

indexes = np.where(arr > 2)[0]
print(indexes)

Output:

[2 3 4]