# Mask a NumPy array with two or more conditions

### Jesse

—### February 18, 2021

Boolean masking is a technique you can use to access elements of an array that match a certain condition e.g.

import numpy as npa = np.array([1, 2, 3, 4, 5])mask = a > 3# array([False, False, False, True, True])a[mask]# array([4, 5])

You can combine two or multiple conditions like so:

mask = (a > 3) & (a != 5) # Note: Parentheses are requireda[mask]# array([4])mask = (a < 2) | (a > 2)a[mask]# array([1, 3, 4, 5])