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 stringFalse: 0, empty string
Concepts in Practice
Converting numeric types and strings to Booleans
Concepts in Practice
Converting Booleans to numeric types and strings
Given is_on = True, what is the value of each expression?
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: <=
Concepts in Practice
Comparing values
For each new variable, what is the value of compare_result?
= vs ==
A common mistake is using = for comparison instead of ==. Ex: is_zero = num=0 will always assign is_zero and num with 0, regardless of num's original value. The = operator performs assignment and will modify the variable. The == operator performs comparison, does not modify the variable, and produces True or False.
Exploring further
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.
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".