bool() in Python

Last Updated : 21 Feb, 2025

In Python, bool() is a built-in function that is used to convert a value to a Boolean (i.e., True or False). The Boolean data type represents truth values and is a fundamental concept in programming, often used in conditional statements, loops and logical operations.

bool() function evaluates the truthness or falseness of a given value and returns either True or False. Understanding how bool() works is crucial for writing effective and efficient Python code.

Example:

Python

x = bool(1) print(x) y = bool() print(y)

Output

True False

Syntax of bool() function

bool([x])

Parameters

x: represents the value that we want to convert to a Boolean. If no argument is provided, bool() returns False by default.

Return Value of bool()

The bool() function returns:

True if the value x is considered “truth”
False if the value x is considered “false.”

Truth and False Values in Python

In Python, certain values are considered “truth” or “false” based on their inherent properties. Here’s a breakdown:

False Values:

False: The Boolean value False.
None: The None keyword, which represents the absence of a value.
0: The integer zero.
0.0: The floating-point zero.
“”: An empty string.
[]: An empty list.
(): An empty tuple.
{}: An empty dictionary.
set(): An empty set.
range(0): An empty range.

Truth Values:

Non-zero numbers (e.g., 1, -1, 3.14).
Non-empty strings (e.g., "hello").
Non-empty collections (e.g., [1, 2, 3], {"key": "value"}).
Objects (e.g., instances of classes).

Examples of bool()

Example 1: Basic usage

Python

print(bool(True))     print(bool(False))    print(bool(0))        print(bool(1))        print(bool(-1))       print(bool(0.0))      print(bool(3.14))     print(bool(""))       print(bool("Hello"))  print(bool([]))       print(bool([1, 2]))   print(bool({}))       print(bool({"a": 1})) print(bool(None))

Output

True False False True True False True False True False True False True False

Explanation:

bool(True) returns True because True is already a Boolean value.
bool(False) returns False because False is already a Boolean value.
bool(0) returns False because 0 is a false value.
bool(1) returns True because 1 is a truth value.
bool(-1) returns True because any non-zero number is truth.
bool(0.0) returns False because 0.0 is a false value.
bool(3.14) returns True because 3.14 is a non-zero number.
bool(“”) returns False because an empty string is false.
bool(“Hello”) returns True because a non-empty string is truth.
bool([]) returns False because an empty list is false.
bool([1, 2]) returns True because a non-empty list is truth.
bool({}) returns False because an empty dictionary is false.
bool({“a”: 1}) returns True because a non-empty dictionary is truth.
bool(None) returns False because None is a false value.

Example 2: Using bool() in conditional statement

Python

value = 10 if bool(value): print("The value is truth.") else: print("The value is false.")

Output

The value is truth.

Explanation:

The bool(value) function is used to check if value is truth or false.
Since value is 10, which is a non-zero number, bool(value) returns True.
Therefore, the if block is executed, and the message “The value is truth.” is printed.

Example 3: Using bool() with custom objects

Python

class gfg:     def __init__(self, value):         self.value = value      def __bool__(self):         return bool(self.value)  obj1 = gfg(0) obj2 = gfg(42)  print(bool(obj1))   print(bool(obj2))

Output

False True

Explanation:

In this example, we define a custom class gfg with an __init__ method and a __bool__ method.
The __bool__ method is a special method in Python that defines the truthiness of an object when bool() is called on it.
When bool(obj1) is called, the __bool__ method of obj1 is invoked, which returns bool(self.value). Since self.value is 0, bool(obj1) returns False.
Similarly, bool(obj2) returns True because self.value is 42, which is a non-zero number.

Python bool() function to check odd and even number

Here is a program to find out even and odd by the use of the bool() method. You may use other inputs and check out the results.

Python

def check_even(num):     return bool(num % 2 == 0)  num = 8  if check_even(num):     print("Even") else:     print("Odd")

Output

Even

Explanation:

num % 2 == 0 this checks if the number is divisible by 2.
bool(num % 2 == 0) converts the result into True (even) or False (odd).
conditional check if True, prints “Even” otherwise “Odd”.

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bool() in Python

Syntax of bool() function

Parameters

Return Value of bool()

Truth and False Values in Python

Examples of bool()

Example 1: Basic usage

Example 2: Using bool() in conditional statement

Example 3: Using bool() with custom objects

Python bool() function to check odd and even number

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