Booleans

A boolean represents one of two possible states: True or False. Booleans are the backbone of every decision your program makes — every if statement, while loop condition, and comparison ultimately resolves to one of these two values.

True and False Are Keywords

In Python, True and False are reserved keywords, always written with a capital first letter (unlike true/false in JavaScript or Java). They belong to the built-in bool type.

Python

is_active = True
has_permission = False

print(type(is_active))  # <class 'bool'>
print(is_active)         # True

# true = True  -- this would just create a normal variable named "true";
#                 it is NOT the same as the keyword True

bool Is a Subclass of int

Booleans are, under the hood, a specialized form of integer. True behaves like 1 and False behaves like 0 in arithmetic and comparisons.

Python

print(True == 1)     # True
print(False == 0)    # True
print(True + True)   # 2  -- booleans can be added like integers
print(isinstance(True, int))  # True -- bool IS an int subclass

scores = [90, 85, 100]
passing = [s >= 90 for s in scores]
print(sum(passing))   # 2 -- True is counted as 1 when summed

Truthy and Falsy Values

Every object in Python has an inherent truthiness — it can be used anywhere a boolean is expected, such as in an if condition. Most objects are truthy; a specific, well-defined set of values is falsy.

Falsy Value	Type
False	bool
0, 0.0, 0j	int, float, complex
'' (empty string)	str
[] (empty list)	list
() (empty tuple)	tuple
{} (empty dict)	dict
set() (empty set)	set
None	NoneType

Everything else — non-zero numbers, non-empty strings and collections, and virtually every other object — is truthy.

Python

values = [0, 1, "", "hi", [], [1, 2], {}, None, 3.14]

for v in values:
    print(f"{v!r}: {'truthy' if v else 'falsy'}")

# 0: falsy
# 1: truthy
# '': falsy
# 'hi': truthy
# []: falsy
# [1, 2]: truthy
# {}: falsy
# None: falsy
# 3.14: truthy

Using bool() to Check Truthiness

The built-in bool() function converts any value to its explicit True/False equivalent, which is a quick way to verify how Python will treat something in a conditional context.

Python

print(bool(0))        # False
print(bool(42))       # True
print(bool(""))       # False
print(bool("no"))     # True -- even the string "False" would be truthy, since it's non-empty!
print(bool([]))       # False
print(bool([0]))      # True -- a list containing one element (even a falsy one) is truthy

Note

A common trap: `bool("False")` is `True`. Truthiness of a string depends only on whether it is empty, not on what text it contains.

Comparison Operators Return Booleans

Every comparison operator (==, !=, <, >, <=, >=) evaluates to a boolean, which is why they combine naturally with if statements and logical operators.

Python

age = 20
print(age == 20)   # True
print(age != 18)    # True
print(age < 18)     # False
print(age >= 18)    # True

can_vote = age >= 18
print(can_vote)      # True

Combining Booleans

Python provides and, or, and not for combining boolean expressions. These follow their own short-circuiting rules and are covered fully in the dedicated tutorial on logical operators.

Python

age = 20
has_id = True

can_enter = age >= 18 and has_id
print(can_enter)  # True

Tip

See the Logical Operators tutorial for a deep dive into `and`, `or`, `not`, short-circuit evaluation, and how they interact with non-boolean truthy/falsy values.

Key Takeaways

True and False are capitalized keywords belonging to the bool type.
bool is a subclass of int — True behaves as 1, False as 0.
A specific set of values are falsy: 0, 0.0, "", [], (), {}, set(), and None. Everything else is truthy.
bool(value) reveals how Python will treat any object in a boolean context.
All comparison operators produce boolean results.