Boolean Logic

Combine conditions with and, or, not, and master Python truthiness

You've used if with simple conditions like x > 5. But real programs need to check multiple things at once, "is the user logged in AND does she have a premium account?" That's where boolean logic comes in.

and, or, not in actionpython

age = 20
has_ticket = True

# AND: both must be True
if age >= 18 and has_ticket:
    print("You can enter")   # ✓ prints

# OR: at least one must be True
is_member = False
has_guest_pass = True
if is_member or has_guest_pass:
    print("Welcome!")        # ✓ prints

# NOT: flips True → False, False → True
is_closed = False
if not is_closed:
    print("Store is open")   # ✓ prints

Boolean operators:

and → True only when BOTH sides are True

or → True when EITHER side is True

not → reverses True ↔ False

Truthiness, Python treats some values as "false-like" even when they aren't literally False. This lets you write cleaner conditions.

Falsy values: 0, "", [], Nonepython

# All of these behave like False in an if statement:
if 0:       print("won't run")
if "":      print("won't run")
if []:      print("won't run")
if None:    print("won't run")

# All of these behave like True:
if 42:      print("runs!")
if "hello": print("runs!")
if [1, 2]:  print("runs!")

# Practical: check if a string is empty
name = ""
if not name:
    print("Please enter your name")   # prints!

if username: and if username != "": are equivalent in Python. The first is considered more "Pythonic", shorter and just as clear.

Short-circuit evaluation, Python stops evaluating as soon as the result is certain. In A and B, if A is False, Python never checks B. In A or B, if A is True, B is never checked. This matters when B might crash.

Short-circuit safetypython

users = []

# Without short-circuit guard, crashes if list is empty:
# if users[0] == "admin":  ← IndexError!

# Safe version using short-circuit:
if users and users[0] == "admin":
    print("Admin found")
# If users is empty (falsy), Python skips the second check

Practice Exercises

0/3 solved

Exercise 1 of 3easy

⏱ 00:00

Can They Enter?

Write a function can_enter(age, has_ticket) that returns True only if the person is 18 or older AND has a ticket.

solution.py

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Exercise 2 of 3easy

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Strong Password

Write a function is_strong(password) that returns True if the password meets ALL three rules:- At least 8 characters long- Contains at least one digit- Contains at least one uppercase letter
Useful built-ins: any(c.isdigit() for c in s) checks for digits, any(c.isupper() for c in s) checks for uppercase.

solution.py

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Exercise 3 of 3medium

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Access Control

Write a function can_access(role, is_active, resource) that returns True if:- The role is "admin" (admins can access anything), OR- The role is "user" AND is_active is True AND resource is "public"
All other combinations return False.

solution.py

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Solve all 3 exercises to unlock completion

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