Passing array to an array in numpy

Question

import numpy as np

arr1= np.array([10,20,30,40,50])
arr2= np.array([False, False,  True,  True,  True])

result=arr1[arr2] #[30 40 50]

Having hard time to grasp this. When another numpy array is passed to an existing numpy array, all elements multiplied?

No, it's called boolean or masked indexing. numpy.org/devdocs/user/… — Valentino
– Valentino, Commented May 29, 2021 at 12:07

sacuL · Accepted Answer · 2021-05-29 12:07:08Z

3

You're indexing a numpy array by another array, rather than passing an array to another array. In your case, since you're using a boolean index, it's creating a mask, and only returning the values of arr1 where arr2 is True.

answered May 29, 2021 at 12:07

sacuL

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