bool() in Python

bool() is a built-in function that converts a value to a Boolean (True or False). The Boolean data type is fundamental in programming and is commonly used in conditional statements, loops and logical operations. The bool() function evaluates the truthiness or falseness of a value and returns either True or False. Understanding bool() is essential for writing clean and efficient Python code.

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

True
False

Syntax:

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:

• 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()

1. Basic usage

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))    

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.

2. Using bool() in conditional statement

value = 10

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

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.

3. Using bool() with Custom Objects

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))  

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. 

def check_even(num):
    return bool(num % 2 == 0)

num = 8

if check_even(num):
    print("Even")
else:
    print("Odd")

Even

Explanation:

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

Related Articles:

• Python Boolean
• Check for True or False in Python