Python Nested if Statements

Some decisions only make sense after another decision has been made. You only ask for the 2FA code after the password is correct. A Python nested if statement handles exactly this: an if inside another if. In this lesson, you'll learn how nested if statements work, when you really need them, and how to keep them from turning into hard-to-read code.

What is a nested if statement in Python?

A nested if is an if statement written inside the block of another if, elif or else. The inner statement is indented one more level, and Python only reaches it when the outer condition is true.

height_cm = 135
age = 10
with_adult = True

if height_cm >= 120:
    print("Height check passed.")
    if age >= 12 or with_adult:
        print("Enjoy the ride!")
    else:
        print("Sorry, riders under 12 need an adult.")
else:
    print("Sorry, you must be at least 120 cm tall.")

Height check passed.
Enjoy the ride!

Read it from the outside in. The outer if checks the height. The inner if (indented 8 spaces in total) checks the age rule, but only for people who passed the height check.

How does Python run a nested if?

Python follows the same top-to-bottom rule you learned in if, elif and else, one level at a time:

1. Check the outer condition.
2. If it's False, jump to the outer else (if there is one). The inner if is never looked at.
3. If it's True, run the outer block line by line. When Python reaches the inner if, it checks that condition the same way.

Try changing height_cm to 110 in the example above. The output becomes just Sorry, you must be at least 120 cm tall. The age rule is skipped completely.

When do you need a nested if?

Nesting is the right tool when the inner check only makes sense after the outer one passes, or when each level needs its own else message. A login system is a classic case:

username = "maya"
password = "sunflower42"
has_2fa = True
code_entered = "381904"
code_sent = "381904"

if username == "maya" and password == "sunflower42":
    if has_2fa:
        if code_entered == code_sent:
            print("Logged in with 2FA.")
        else:
            print("Wrong verification code.")
    else:
        print("Logged in. Tip: turn on 2FA for extra safety.")
else:
    print("Wrong username or password.")

Logged in with 2FA.

Each level has a different message for failure, so nesting makes the logic clear. Asking for a code before the password is right would make no sense, which is exactly what the structure prevents.

How do you avoid deeply nested if statements?

Each extra level pushes the code further right and makes it harder to follow. Programmers call deeply nested code the "arrow" shape. Here are three ways to flatten it.

1. Combine conditions with and

If the outer if has no else and contains nothing but the inner if, merge them with and:

temperature = 24
is_weekend = True

# Nested version
if is_weekend:
    if temperature > 20:
        print("Beach day!")

# Flat version: same result, one level
if is_weekend and temperature > 20:
    print("Beach day!")

Beach day!
Beach day!

2. Use elif instead of else + if

An if sitting alone inside an else is usually an elif in disguise:

battery = 35

# Nested version
if battery > 80:
    print("Fully charged")
else:
    if battery > 20:
        print("Okay for now")
    else:
        print("Charge soon")

# Flat version with elif
if battery > 80:
    print("Fully charged")
elif battery > 20:
    print("Okay for now")
else:
    print("Charge soon")

Okay for now
Okay for now

3. Handle the "no" cases first (guard clauses)

A guard clause checks for a problem first and deals with it right away, so the main path doesn't have to be nested inside a success check. Instead of "if everything is fine, then... then... then...", you write "if this is wrong, stop here". Here's an order checkout written that way with an elif chain:

cart_items = 3
in_stock = True
card_valid = False

if cart_items == 0:
    print("Your cart is empty.")
elif not in_stock:
    print("Sorry, an item is out of stock.")
elif not card_valid:
    print("Your card was declined.")
else:
    print("Order placed. Thank you!")

Your card was declined.

Every problem is handled on its own line at the same level, and the happy path sits at the end. The nested version of this would need three levels of indentation. Guard clauses become even more useful inside functions, where you can return early; you'll see that in the Functions chapter.

Real-world example: a flight check-in

This program nests where the logic needs it and stays flat everywhere else:

has_ticket = True
passport_valid = True
bags = 2
ticket_class = "economy"

if has_ticket and passport_valid:
    print("Check-in complete.")
    if bags > 1:
        if ticket_class == "business":
            print("Extra bag included in your ticket.")
        else:
            fee = (bags - 1) * 35
            print(f"Extra bag fee: ${fee}")
    print("Please go to gate B12.")
else:
    print("Please visit the help desk.")

Check-in complete.
Extra bag fee: $35
Please go to gate B12.

Notice the last print("Please go to gate B12."). It's indented at the outer level, so it runs for every passenger who checked in, no matter how many bags they have.

Common mistakes with nested if

1. Indenting the inner block wrongly

age = 20
has_id = True
if age >= 18:
    if has_id:
    print("Welcome in")

IndentationError: expected an indented block after 'if' statement on line 4

The inner block needs one more level: 8 spaces in total.

2. An else attached to the wrong if

is_member = False
points = 500

if is_member:
    if points >= 100:
        print("You earned a reward!")
    else:
        print("Join our club to earn rewards.")

This prints nothing. The else is indented under the inner if, so it belongs to points >= 100, and non-members never get there. To answer non-members, move else: back to line up with if is_member:. In Python, the indent decides which if an else belongs to.

3. Nesting when and would do

Three levels of nested ifs with no else blocks can almost always be written as one if with and. Flatten it.

Practice exercise

is_weekend = True
is_sunny = False

if is_weekend:
    if is_sunny:
        print("Go for a hike")
    else:
        print("Movie marathon")
else:
    print("Work day")

Movie marathon

What's next?

When you need to compare one value against many possible options, a long elif chain can get repetitive. Next, learn a neat alternative: the Python match-case statement.