How to use multiple conditions in numpy where() function

Question

How can I specify multiple conditions using and/or in the where() function of Numpy?

E.g.

a=np.array([12,14,16,18,7,8,45,23,34])

I want to find indices of numbers that are less than 20 but greater than 10 using the where() function.

Answer 1

If you want to use multiple conditions in the where() function of Numpy, you need to put those conditions inside the parentheses "()," and instead of using and/or, you need to use &/|.

& is AND

| is OR

Here is an example to show how to use multiple conditions in the Numpy where() function.

>>> import numpy as np
>>> a=np.array([12,14,16,18,7,8,45,23,34])
>>> a
array([12, 14, 16, 18,  7,  8, 45, 23, 34])
>>> np.where((a>10) & (a<20))
(array([0, 1, 2, 3]),)
>>> a[np.where((a>10) & (a<20))[0]]
array([12, 14, 16, 18])