Boolean data in Python

Whenever a program decides what to do next, whether to print a message, whether to let a user in, whether to retry a request, it works with boolean values. Python's bool type holds exactly two values: True and False, and every condition and check is built from them.

What is boolean data?

In Python, the values "true" and "false" are represented by the bool type, which can hold only two values:

True
False

Python 3.13
12345
# Create boolean variables
is_raining = True
likes_pizza = True

print(type(is_raining))
<class 'bool'>

Important: True and False are always written with a capital first letter. If you write true or false, Python won't understand them and will throw an error.

Boolean operators

We often need to combine several conditions. For example: "I'll go to the beach if it's sunny AND warm" or "I'll buy this phone if it's beautiful OR cheap". Python gives us three operators for this: and, or, not.

The and operator (logical AND)

Returns True only if both values are true:

Python 3.13
123456
sunny = True
warm = True

# Go to the beach if sunny AND warm
going_to_beach = sunny and warm
print(f"Sunny: {sunny}, Warm: {warm}")
Sunny: True, Warm: True
7
print(f"Going to the beach? {going_to_beach}")
Going to the beach? True
891011
# What if the weather changes?
warm = False  # It got cold
going_to_beach = sunny and warm
print(f"Sunny: {sunny}, Warm: {warm}")
Sunny: True, Warm: False
12
print(f"Going to the beach? {going_to_beach}")
Going to the beach? False

The or operator (logical OR)

Returns True if at least one value is true:

Python 3.13
123456
phone_is_beautiful = True
phone_is_cheap = False

# Buy the phone if it's beautiful OR cheap
will_buy_phone = phone_is_beautiful or phone_is_cheap
print(f"Phone is beautiful: {phone_is_beautiful}, Phone is cheap: {phone_is_cheap}")
Phone is beautiful: True, Phone is cheap: False
7
print(f"Will we buy the phone? {will_buy_phone}")
Will we buy the phone? True

The not operator (logical NOT)

Inverts the value: True becomes False, and vice versa:

Python 3.13
12
have_homework = True
print(f"I have homework: {have_homework}")
I have homework: True
3
print(f"I do NOT have homework: {not have_homework}")
I do NOT have homework: False

Comparing values

Boolean values often come up as the result of a comparison:

Python 3.13
12345
# Comparing numbers
my_age = 25
friend_age = 30

print(f"My age: {my_age}, friend's age: {friend_age}")
My age: 25, friend's age: 30
6
print(f"Are we the same age? {my_age == friend_age}")
Are we the same age? False
7
print(f"Are we different ages? {my_age != friend_age}")
Are we different ages? True
8
print(f"Am I younger? {my_age < friend_age}")
Am I younger? True
910
# Comparing strings (alphabetically)
print(f"'apple' < 'banana': {'apple' < 'banana'}")
'apple' < 'banana': True

The is operator: comparing identity

Beyond ==, Python also has the is operator. They look similar but check different things:

== compares values (what's inside)
is compares identity (whether two names point at the same object in memory)

Python 3.13
12345
my_scores = [90, 85, 95]
friend_scores = [90, 85, 95]  # Same list, but a different object
same_list = my_scores         # The same object

print(f"Same content? {my_scores == friend_scores}")
Same content? True
6
print(f"The same object? {my_scores is friend_scores}")
The same object? False
7
print(f"Is same_list the same object as my_scores? {my_scores is same_list}")
Is same_list the same object as my_scores? True

Rule of thumb: in the vast majority of cases you want ==. The is operator is appropriate only for checks against the special singletons: is None, is True, is False. Using is on numbers, strings, or lists is almost always a bug.

Operator precedence: what's evaluated first?

Operators are applied in this order (from highest to lowest precedence):

not (highest precedence)
and
or (lowest precedence)

Python 3.13
12345678910
# Precedence example
has_ticket = True
has_passport = False
has_visa = True

# Can we travel abroad?
# We need a ticket AND (passport OR visa)
can_travel = has_ticket and (has_passport or has_visa)

print(f"has_ticket and (has_passport or has_visa) = {can_travel}")
has_ticket and (has_passport or has_visa) = True
111213
# Step-by-step evaluation:
step1 = has_passport or has_visa  # First, the expression in parentheses is evaluated
print(f"Step 1: has_passport or has_visa = {step1}")
Step 1: has_passport or has_visa = True
1415
step2 = has_ticket and step1  # Then the and operator is applied
print(f"Step 2: has_ticket and (result of step 1) = {step2}")
Step 2: has_ticket and (result of step 1) = True

Tip: if you're unsure about the order of evaluation, use parentheses. They make the code clearer and let you control the order explicitly.

Conversion to boolean: what counts as true?

The bool function

Python can convert any value to a boolean:

Python 3.13
1
print(bool(100))
True
2
print(bool(0))
False
3
print(bool("Hello"))
True
4
print(bool(""))
False

What is considered true and false?

In Python most values are considered true (True).

The values considered false (False) are only:

False (the boolean "no")
None (absence of a value)
Zero: 0, 0.0, 0j
Empty containers: "", (), [], {}

Python 3.13
12345
money = 0
if money:
    print("I have money")
else:
    print("My wallet is empty")
My wallet is empty
678910
name = "Alex"
if name:
    print(f"Hello, {name}")
else:
    print("Hello, stranger")
Hello, Alex

Understanding check

Let's check how well you've absorbed the material:

What will the following expression return?

Python 3.13
1
result = (False or True) and not (False and True or True)