If Statements

Introduction

If statements allow your program to make decisions. Code inside an if block only runs when the condition is True.

Basic If Statement

if condition:
    # code to run when condition is True

Example

salary = 75000

if salary > 50000:
    print("Senior role")

If / Else

salary = 30000

if salary > 50000:
    print("Senior role")
else:
    print("Junior role")

If / Elif / Else

Use elif (short for "else if") to check multiple conditions in sequence. Python stops at the first match.

salary = 55000

if salary < 30000:
    print("Junior")
elif salary < 60000:
    print("Mid-level")
elif salary < 100000:
    print("Senior")
else:
    print("Principal or above")

Output

Mid-level

Indentation Matters

Python uses indentation (4 spaces) to define blocks. Incorrect indentation will cause an IndentationError.

# Correct
if salary > 50000:
    print("High earner")

# Wrong — will raise IndentationError
if salary > 50000:
print("High earner")

Nested If Statements

You can place if statements inside other if statements.

department = "Engineering"
salary = 80000

if department == "Engineering":
    if salary > 75000:
        print("Senior Engineer")
    else:
        print("Engineer")

Tip: Deeply nested code is hard to read. If you find yourself going more than two levels deep, consider restructuring using and / or.

Truthy and Falsy Values

In Python, values other than True and False can be treated as booleans in an if condition.

Falsy	Truthy
0	Any non-zero number
"" (empty string)	Any non-empty string
[] (empty list)	Any non-empty list
None	Any object

name = ""

if name:
    print(f"Hello, {name}")
else:
    print("No name provided")

Practice Exercises

• Write an if/elif/else statement that categorises a product price: under 10 is "Cheap", between 10 and 50 is "Moderate", above 50 is "Expensive".
• Ask the user for a number. Print whether it is positive, negative, or zero.
• Check if a username variable is an empty string and print an appropriate message.
• Write an if statement using and to check if a salary is between 40000 and 90000.