Python bool() Function

Python’s built-in bool(x) function converts value x to a Boolean value True or False. It uses implicit Boolean conversion on the input argument x. Any Python object has an associated truth value. The bool(x) function takes only one argument, the object for which a Boolean value is desired.

Input : bool(1)
Output : True

Input : bool(0)
Output : False

Input : bool(True)
Output : True

Input : bool([1, 2, 3])
Output : True

Input : bool([])
Output : False

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Examples bool() Functions

The following code shows you how to use the bool(x) function on different input arguments that all lead to True results.

#####################
# True Boolean Values
#####################

# All integers except 0
print(bool(1))
print(bool(2))
print(bool(42))
print(bool(-1))

# All collections except empty ones
# (lists, tuples, sets)
print(bool([1, 2]))
print(bool([-1]))
print(bool((-1, -2)))
print(bool({1, 2, 3}))

# All floats except 0.0
print(bool(0.1))
print(bool(0.0000001))
print(bool(3.4))


# Output is True for all previous examples

The following list of executions of the function bool(x) all result in Boolean values of False.

#####################
# False Boolean Values
#####################

# Integer 0
print(bool(0))

# Empty collections
# (lists, tuples, sets)
print(bool([]))
print(bool({}))
print(bool(()))

# Float 0.0
print(bool(0.0))

# Output is False for all previous examples

You can observe multiple properties of the bool() function:

• You can pass any object into it and it will always return a Boolean value because all Python objects implement the __bool__() method and have an associated implicit Boolean value. You can use them to test a condition: 0 if x else 1 (example ternary operator).
• The vast majority of objects are converted to True. Semantically, this means that they’re non-empty or whole.
• A minority of objects convert to False. These are the “empty” values—for example, empty lists, empty sets, empty tuples, or an empty number 0.

Summary

Python’s built-in bool(x) function converts value x to a Boolean value True or False.

It uses implicit Boolean conversion on the input argument x.

Any Python object has an associated truth value.

The bool(x) function takes only one argument, the object for which a Boolean value is desired.

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Chris

While working as a researcher in distributed systems, Dr. Christian Mayer found his love for teaching computer science students.

To help students reach higher levels of Python success, he founded the programming education website Finxter.com. He’s author of the popular programming book Python One-Liners (NoStarch 2020), coauthor of the Coffee Break Python series of self-published books, computer science enthusiast, freelancer, and owner of one of the top 10 largest Python blogs worldwide.

His passions are writing, reading, and coding. But his greatest passion is to serve aspiring coders through Finxter and help them to boost their skills. You can join his free email academy here.