A boolean value is a data type that can only take on one of two values: True or False.
These values are often used in the context of conditional statements and loops to control the flow of a program.
In this guide, we will cover the basics of Python booleans, including how to create boolean variables, the various ways to evaluate expressions as boolean values, and some common use cases for booleans in programming.
Creating Boolean Variables
To create a boolean variable in Python, you simply need to assign the value True or False to a variable.
is_running = True is_sleeping = False
You can also use the bool() function to convert other types of data into boolean values.
For example, the following code will create a boolean variable is_zero that is True if the variable x is equal to 0, and False otherwise:
x = 0 is_zero = bool(x) # is_zero is True
Evaluating Expressions as Booleans
In many cases, you may need to evaluate an expression as a boolean value, rather than assigning a specific value to a variable.
For example, you may need to check whether a certain condition is true or false.
In Python, any non-zero or non-empty value is considered to be True, and zero or empty values are considered to be False.
x = 5 y = 0 print(bool(x)) # True print(bool(y)) # False
You can also use comparison operators to compare two values and evaluate the expression as a boolean value.
x = 5 y = 10 print(x < y) # True print(x > y) # False
Python provides several boolean operators that allow you to combine multiple boolean expressions and evaluate them together.
The most common operators are:
- and: Returns True if both operands are True, and False otherwise.
- or: Returns True if at least one of the operands is True, and False otherwise.
- not: Inverts the value of the operand.
x = 5 y = 10 print((x < y) and (x > 0)) # True print((x < y) or (x > 0)) # True print(not (x < y)) # False
Common Use Cases
Booleans are often used in conjunction with if and else statements to control the flow of a program.
x = 5 if x > 0: print("x is positive") else: print("x is non-positive")
Booleans are also commonly used in loops to control when a loop should terminate.
while x > 0: x -= 1 print(x)
You can use boolean values to filter out certain elements from a list or other data structure.
numbers = [1, 2, 3, 4, 5] positive_numbers = [x for x in numbers if x > 0] print(positive_numbers) # [1, 2, 3, 4, 5]
Booleans can be used to check if an operation was successful or not.
For example, a function that attempts to open a file may return True if the file was successfully opened, and False otherwise.
This can then be used to handle any errors that may have occurred during the operation.
You can use booleans to check if the input received from a user or another source is valid before processing it further.
For example, you can check if a string entered by a user is a valid email address or not.
In conclusion, Python booleans are a simple but powerful data type that are used to control the flow of a program, filter data and for many other functionalities.
Understanding how to create and manipulate boolean variables and expressions is an essential part of becoming proficient in Python programming.