Nested Conditions and Ternary Expressions

15 min · Beginner

When a secondary decision depends on an initial condition succeeding, we can nest conditionals. For simple two-way assignments, Python provides a compact ternary expression.

Nested if statements

Nested if is an if statement placed inside the block of another if. The inner check runs only when the outer condition is True, so the inner block sits one level deeper.

An if statement placed inside another if block executes only when the outer condition is true.

Python

1account_active = True2balance = 2503
4if account_active:5    if balance >= 100:6        print("Transaction approved")7    else:8        print("Low balance")9else:10    print("Account suspended")

Example 1 · Loan pre-check

Python

1age = 252income = 400003
4if age >= 21:5    if income >= 30000:6        print("Application accepted")7    else:8        print("Income too low")9else:10    print("Applicant too young")

Output

Application accepted

What this code does

The income check only runs when the age check passes.
Both are True here, so the innermost print runs. The two else lines belong to their own if.

Example 2 · Same check, one level

Python

1is_logged_in = True2cart_items = 23
4if is_logged_in and cart_items > 0:5    print("Go to payment")6else:7    print("Cannot check out")

Output

Go to payment

What this code does

Two nested ifs with no code between them can become one if joined by and.
The flat version is shorter and has one less level of indentation.

Each nested level adds 4 more spaces of indentation. Keep nesting shallow (at most 2-3 levels) for maintainability.

Python's ternary operator: inline if-else

Ternary expression is a one-line expression of the form a if condition else b. It gives a when the condition is True and b when it is False, so it can be assigned or printed directly.

For concise conditional assignment, Python uses the syntax: value_if_true if condition else value_if_false.

Python

age = 20status = "Adult" if age >= 18 else "Minor"print(status)

Example 3 · Stock label

Python

stock = 0label = "In stock" if stock > 0 else "Sold out"print(label)

Output

Sold out

What this code does

stock > 0 is False, so the ternary gives the text after else.
The result is stored in label like any other value.

This is Python's equivalent of the C/Java condition ? a : b operator. It reads like natural English prose.

Using ternary expressions in prints and calculations

Because a conditional expression evaluates to a value, you can pass it directly into function calls or calculations.

Python

score = 85print(f"Result: {'Pass' if score >= 50 else 'Fail'}")

Example 4 · Member discount

Python

1is_member = True2purchase_amount = 8003
4discount = 0.15 if is_member and purchase_amount >= 500 else 0.055final_price = purchase_amount * (1 - discount)6
7print(f"Discount: {int(discount * 100)}%")8print(f"Final price: {final_price}")

Output

Discount: 15%
Final price: 680.0

What this code does

Uses a ternary expression to select 15% discount for qualifying members.
Calculates final price and prints formatted summary.

The ternary expression evaluates inline inside the f-string curly braces, printing Result: Pass.

Next step

Check your understanding

8 quick questions

1is_member = True2purchase_amount = 8003 4discount = 0.15 if is_member and purchase_amount >= 500 else 0.055final_price = purchase_amount * (1 - discount)6 7print(f"Discount: {int(discount * 100)}%")8print(f"Final price: {final_price}")