If statements

What are if statements?

If statements let your program make decisions. They check if something is true or false, then act accordingly. Real-life logic:

IF it’s raining THEN take umbrella
IF battery < 20% THEN charge phone
IF password correct THEN allow access

Basic if statement

age = 18

if age >= 18:
    print("You can vote!")
    print("You're an adult")

How it works:

Check the condition (age >= 18)
If True, run the indented code
If False, skip it

The colon : and indentation are required! This is how Python knows what code belongs to the if statement.

If-else statements

Handle both True and False cases:

temperature = 25

if temperature > 30:
    print("It's hot!")
else:
    print("Nice weather!")

If-elif-else chains

For multiple conditions:

score = 85

if score >= 90:
    print("A - Excellent!")
elif score >= 80:
    print("B - Good job!")
elif score >= 70:
    print("C - Keep it up!")
else:
    print("F - Need improvement")

Python checks each condition in order and runs the first True one.

Why elif instead of multiple if statements? With elif, Python stops checking once it finds a true condition. This is more efficient and prevents multiple blocks from running. The order matters - always put more specific conditions first!

Multiple conditions

Combine conditions with and, or, not:

age = 25
has_license = True

# Both must be True
if age >= 18 and has_license:
    print("You can drive!")

# At least one must be True
if weekend or holiday:
    print("No work today!")

# Reverse the condition
if not raining:
    print("Let's go outside!")

Nested if statements

Put if statements inside other if statements:

has_ticket = True
age = 15

if has_ticket:
    if age >= 18:
        print("Enjoy the movie!")
    else:
        print("Need adult supervision")
else:
    print("Buy a ticket first")

Common mistakes

Forgetting the colon

# Wrong
if x > 5
    print("Big")

# Right
if x > 5:
    print("Big")

Using = instead of ==

# Wrong (assignment)
if x = 5:
    print("Five")

# Right (comparison)
if x == 5:
    print("Five")

Wrong indentation

# Wrong
if True:
print("Hello")  # IndentationError

# Right
if True:
    print("Hello")

Practice & Exercises

To reinforce what you’ve learned in this section (If, If-Else, and Elif Statements), practice with these interactive notebooks:

Follow-Along Practice

Practice basic conditions, if-else branches, and nested logical expressions.💻 VS Code | 🚀 Colab | 📥 Download

Practice Exercises

Test your conditional logic skills with exercises on even/odd checkers and custom ticketing pricing rules.💻 VS Code | 🚀 Colab | 📥 Download

What’s next?

Now let’s learn about the clean pattern matching tool: Match Case!

Match Case

Structural pattern matching for value checking

Getting started

Data types

Working with data

Control flow

Data structures

Packing & Unpacking

What are if statements?

Basic if statement

If-else statements

If-elif-else chains

Multiple conditions

Nested if statements

Common mistakes

Practice & Exercises

Follow-Along Practice

Practice Exercises

What’s next?

Match Case

​What are if statements?

​Basic if statement

​If-else statements

​If-elif-else chains

​Multiple conditions

​Nested if statements

​Common mistakes

​Practice & Exercises

Follow-Along Practice

Practice Exercises

​What’s next?

Match Case

What are if statements?

Basic if statement

If-else statements

If-elif-else chains

Multiple conditions

Nested if statements

Common mistakes

Practice & Exercises

What’s next?