How to Convert Numpy Array to Boolean Value

Learn how to convert NumPy arrays to boolean dtype using astype() and other methods for logical operations and comparisons.

Making use of the atype method

The astype() method is a versatile method that can be used to convert a NumPy array to different data types. To convert a NumPy array to a boolean value, you can use the following syntax:

numpy_array.astype(dtype=bool)

where numpy_array is the NumPy array you want to convert and dtype=bool specifies the data type to convert to.

For example, the following code converts the NumPy array my_array to a boolean value:

import numpy as np

my_array = np.array([1, 0, 1, 5, 0, 1])
print(f"My array is: \n{my_array}")

my_array = my_array.astype(dtype=bool)
print(f"My boolean array is: \n{my_array}")

As you may notice, zeros got changed to 0 and other numbers to 1.

Other Ways to Convert a NumPy Array to a Boolean Value

In addition to the astype() method, there are other ways to convert a NumPy array to a boolean value. Here are a few examples:

Use the where() method

The where() returns indices of matching elements, NOT boolean array. Use my_array != 0 for boolean comparison; output should be [True False True True False True]. For example, the following code converts the NumPy array my_array to a boolean value using the where() method:

import numpy as np

my_array = np.array([1, 0, 1, 5, 0, 1])

my_boolean_array = np.where(my_array != 0)

print(my_boolean_array)

The output should be indices tuple: (array(),) showing positions where condition is true, NOT a boolean array.

[ True False True False False True]

Use the isnan() method

The isnan() method returns a Boolean array that indicates whether each element in the array is a NaN (Not a Number) value. For example, the following code converts the NumPy array my_array to a boolean value using the isnan() method:

import numpy as np

my_array = np.array([1, 0, np.nan, 5, 0, 1])

my_boolean_array = np.isnan(my_array)

print(my_boolean_array) 

This code outputs the following:

[False False True False False False] 

Use the logical_not() method

The logical_not() method takes a Boolean array as an argument and returns a Boolean array that negates the values in the original array. For example, the following code converts the NumPy array my_array to a boolean value using the logical_not() method:

import numpy as np

my_array = np.array([1, 0, 1, 5, 0, 1])

my_boolean_array = np.logical_not(my_array == 0)

print(my_boolean_array)

This code outputs the following:

[ True False True False False True]