Before learning about the bool() method in Python, let's see what are Python Booleans.
What is Boolean?
TrueFalse
Python Boolean Type
type() of both True and False is bool.>>> type(False)
<class 'bool'>
>>> type(True)
<class 'bool'>
Boolean Operator
print(18 > 9)
print(18 == 9)
print(18 < 9)
True
False
False
if statement, Python returns True or False:a = 120
b = 50
if b > a:
print("b is greater than a")
else:
print("b is not greater than a")
b is not greater than a
Here, the if condition evaluates to False, hence, the else condition's statement is printed.
After learning about Booleans in Python, let us see the bool() method in Python.
What is the bool() method in Python?
bool() method is a built-in method in Python that allows us to evaluate an expression or value and return True or False.bool() method is used to return or convert a value to a Boolean value(True or False).Syntax of bool()
bool(object)
The bool() method takes 0 or 1 argument. In general, it accepts one object as a parameter like List, String, Number, etc.
Note: If no parameter is passed, the bool() method returns False.
How bool() works?
The following are the few cases in which Python’s bool() method returns False:
- If None is passed.
- If
Falsevalue is passed. (FalseandTrueare keywords in Python) - If 0(zero) is passed in any numeric type, such as 0, 0.0, etc.
- If an empty object is passed such as (), [], {}, "", etc.
- If Objects of Classes having __bool__() or __len()__ method, returning 0 or
False.
Other than the above-mentioned cases, the bool() method always returns True.
Let's look at some examples of the bool() method.
Example 1:
# Returns False as x is False
x = False
print(bool(x))
# Returns True as x is True
x = True
print(bool(x))
# Returns False as x is None
x = None
print(bool(x))
False
True
False
Note: False and True are keywords in Python.
Example 2:
bool() method returns True for any number except 0.print(bool(1))
print(bool(0))
print(bool(0.00))
print(bool(18))
print(bool(-101))
True
False
False
True
True
Example 3:
bool() method return True for any string except an empty string.x = 'CosedDope'
print(bool(x))
x = 'Python is Interesting'
print(bool(x))
x = ''
print(bool(x))
x = ' '
print(bool(x))
True
True
False
True
Note: In the above example, the last print statement prints True as the string is not empty. The length of the string is 1 as space is counted while calculating the length of a string.
Example 4:
bool() method returns True for any List except an empty List.x = ["air", "water", "fire"]
print(bool(x))
x = []
print(bool(x))
x = [1, 2]
print(bool(x))
True
False
True
Example 5:
bool() method returns True for any Tuple except an empty Tuple.x = ("cookies", "chocolates", "wafers")
print(bool(x))
x = ()
print(bool(x))
True
False
Example 6:
bool() method returns False if you have an object that is made from a class with a __len__ function that returns 0 or False.class Person:
def __len__(self):
return 0
obj = Person()
print(bool(obj))
bool() method in Python.def check_num(x):
return (bool(x % 2 == 0))
# Driver Code
x = 101
if (check_num(x)):
print("The number is Even")
else:
print("The number is Odd")
The number is Odd
Here, the check_num() function evaluates if the number passed as a parameter is even or odd and returns True or False accordingly with the help of bool() method. If the bool() method returns True, the if condition's statement is printed and if the bool() method returns False, the else statement is printed.
