4.1 Boolean values

Learning objectives

By the end of this section you should be able to

Explain a Boolean value.
Use bool variables to store Boolean values.
Demonstrate converting integers, floats, and strings to Booleans.
Demonstrate converting Booleans to integers, floats, and strings.
Use comparison operators to compare integers, floats, and strings.

bool data type

People often ask binary questions such as yes/no or true/false questions. Ex: Do you like pineapple on pizza? Ex: True or false: I like pineapple on pizza. The response is a Boolean value, meaning the value is either true or false. The bool data type, standing for Boolean, represents a binary value of either true or false. true and false are keywords, and capitalization is required.

Concepts in Practice

Using Boolean variables

Consider the following code:

is_fruit = "True"
is_vegetable = 0
is_dessert = False

Type conversion with bool

Deciding whether a value is true or false is helpful when writing programs/statements based on decisions. Converting data types to Booleans can seem unintuitive at first. Ex: Is "ice cream" True? But the conversion is actually simple.

bool converts a value to a Boolean value, True or False.

True: any non-zero number, any non-empty string
False: 0, empty string

Comparison operators

Programmers often have to answer questions like "Is the current user the admin?" A programmer may want to compare a string variable, user, to the string, "admin". Comparison operators are used to compare values, and the result is either true or false. Ex: is_admin = (user == "admin"). user is compared with "admin" using the == operator, which tests for equality. The Boolean variable, is_admin, is assigned with the Boolean result.

The 6 comparison operators:

equal to: ==
not equal to: !=
greater than: >
less than: <
greater than or equal to: >=
less than or equal to: <=

Try It

Friday Boolean

"It's Friday, I'm in love" —from "Friday I'm in Love," a song released by the Cure in 1992.

Write a program that reads in the day of the week. Assign the Boolean variable, in_love, with the result of whether the day is Friday or not.

# Read in day 

in_love = # Compute boolean
print("It's", day, "I'm in love?", in_love)

Try It

Even numbers

Write a program that reads in an integer and prints whether the integer is even or not. Remember, a number is even if the number is divisible by 2. To test this use number % 2 == 0. Ex: If the input is 6, the output is "6 is even: True".

Adapted from Introduction to Python Programming by OpenStax (openstax.org), licensed under CC BY-NC-SA 4.0. Changes were made. License: CC-BY-NC-SA-4.0.