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Python Boolean

Summary: in this tutorial, you’ll learn about the Python boolean data type, falsy and truthy values.

Introduction to Python Boolean data type

In programming, you often want to check if a condition is true or not and perform some actions based on the result.

To represent true and false, Python provides you with the boolean data type. The boolean value has a technical name as bool .

The boolean data type has two values: True and False .

Note that the boolean values True and False start with the capital letters ( T ) and ( F ).

The following example defines two boolean variables:

is_active = True is_admin = FalseCode language: Python (python)

When you compare two numbers, Python returns the result as a boolean value. For example:

>>> 20 > 10 True >>> 20 < 10 FalseCode language: Python (python)

Also, comparing two strings results in a boolean value:

>>> 'a' < 'b' True >>> 'a' > 'b' FalseCode language: Python (python)

The bool() function

To find out if a value is True or False , you use the bool() function. For example:

>>> bool('Hi') True >>> bool('') False >>> bool(100) True >>> bool(0) FalseCode language: Python (python)

As you can see clearly from the output, some values evaluate to True and the others evaluate to False .

Falsy and Truthy values

When a value evaluates to True , it’s truthy. And if a value evaluates to False , it’s falsy.

The following are falsy values in Python:

• The number zero ( 0 )
• An empty string »
• False
• None
• An empty list []
• An empty tuple ()
• An empty dictionary <>

The truthy values are the other values that aren’t falsy.

Note that you’ll learn more about the None , list , tuple , and dictionary in the upcoming tutorials.

Summary

• Python boolean data type has two values: True and False .
• Use the bool() function to test if a value is True or False .
• The falsy values evaluate to False while the truthy values evaluate to True .
• Falsy values are the number zero, an empty string, False, None, an empty list, an empty tuple, and an empty dictionary. Truthy values are the values that are not falsy.

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Python Booleans

Booleans represent one of two values: True or False .

Boolean Values

In programming you often need to know if an expression is True or False .

You can evaluate any expression in Python, and get one of two answers, True or False .

When you compare two values, the expression is evaluated and Python returns the Boolean answer:

Example

When you run a condition in an if statement, Python returns True or False :

Example

Print a message based on whether the condition is True or False :

if b > a:
print(«b is greater than a»)
else:
print(«b is not greater than a»)

Evaluate Values and Variables

The bool() function allows you to evaluate any value, and give you True or False in return,

Example

Evaluate a string and a number:

Example

Most Values are True

Almost any value is evaluated to True if it has some sort of content.

Any string is True , except empty strings.

Any number is True , except 0 .

Any list, tuple, set, and dictionary are True , except empty ones.

Example

The following will return True:

Some Values are False

In fact, there are not many values that evaluate to False , except empty values, such as () , [] , <> , «» , the number 0 , and the value None . And of course the value False evaluates to False .

Example

The following will return False:

One more value, or object in this case, evaluates to False , and that is if you have an object that is made from a class with a __len__ function that returns 0 or False :

Example

class myclass():
def __len__(self):
return 0

Functions can Return a Boolean

You can create functions that returns a Boolean Value:

Example

Print the answer of a function:

def myFunction() :
return True

You can execute code based on the Boolean answer of a function:

Example

Print «YES!» if the function returns True, otherwise print «NO!»:

def myFunction() :
return True

if myFunction():
print(«YES!»)
else:
print(«NO!»)

Python also has many built-in functions that return a boolean value, like the isinstance() function, which can be used to determine if an object is of a certain data type:

Example

Check if an object is an integer or not:

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