How to invert the elements of a numpy boolean array in python ?

In this article, we will discuss how to invert a numpy boolean array in Python. We will go over the basics of a numpy boolean array and how to use the bitwise operator to invert it.

Create a numpy boolean array

Let's create a boolean matrix using numpy

import numpy as np

data = np.array([True,True,False], dtype=bool)

Note that

print( type(data) )
print( data.dtype )

returns

<class 'numpy.ndarray'>

and

bool

respectively.

Using numpy invert()

To invert a numpy boolean array, you can use the numpy invert() function to flip each element in the array. This function performs a bitwise NOT operation, which will result in each element of the numpy boolean array being flipped. For example, if an element is True, it will become False, and if an element is False it will become True.

np.invert(data)

gives

array([False, False,  True])

Using the ~ operator

To invert a numpy boolean array, you can also use the bitwise operator (~) to flip each element in the array.

data_inv = ~data

print(data_inv)

gives

array([False, False,  True])

The ~ operator serves as a convenient shorthand for np.invert when operating on ndarrays

Inverting an array of 1 and 0

For certain practical scenarios, we often utilize the values of 0 and 1 to denote boolean information. In such cases, to invert the array using the aforementioned methods, it becomes imperative to initially convert it into a boolean array.

data = np.array([1,1,0])

Note that

~data

then gives

array([-2, -2, -1])

Convert array to a boolean array

data_new = np.array(data, dtype=bool)

gives

array([ True,  True, False])

then

data_inv = ~data_new

gives

array([False, False,  True])

Converting the array to int

data_inv = np.array(data_inv, dtype=int)

gives

array([0, 0, 1])

References