L7 Loops

What is a Loop?

A loop lets your program repeat actions without writing the same code over and over.

Example in real life: You check your messages every 5 minutes. That’s like a loop — repeat until there are no new messages.

🎯 Learning Objectives

By the end of this lesson, you will:

Understand when and how to use for and while loops.
Use break to exit a loop early.
Use continue to skip part of a loop.
Write and test your own loops.

PART 1: for Loops

What is a for loop?

Use a for loop when you know how many times you want something to repeat.
Example use: Print numbers 1 to 5.

🔍 Example 1: Print 0 to 4

# Repeats 5 times, starting at 0

for i in range(5):

print(i)

What it does:

range(5) gives numbers: 0, 1, 2, 3, 4
It runs 5 times
It starts at zero

✏️ Guided Practice

Try copying this and changing the number in range().
What happens if you change it to range(10)?

PART 2: while Loops

What is a while loop?

Use a while loop when you want to repeat something until a condition changes.
Example use: Ask for a password until it’s correct.

🔍 Example 4: Count up to 4

# Keep repeating until count is 5

count = 0

while count < 5:

print(count)

count += 1

Output: 0, 1, 2, 3, 4

🔍 Example 5: Ask for password

# Ask until the correct password is typed

password = ""

while password != "admin123":

password = input("Enter password: ")

It stops only when the user types "admin123".

✏️ Guided Practice

Try changing the password to something else.
What happens if you don’t change count in a while loop?

PART 3: break – Stop the Loop Early

What is break?
It ends the loop immediately — even if the condition or range isn’t finished.

🔍 Example 6: Break inside a for loop

# Stop the loop when i reaches 4

for i in range(10):

if i == 4:

break

print(i)

Output: 0, 1, 2, 3

🔍 Example 7: Break inside a while loop

x = 0

while True:

print(x)

x += 1

if x == 5:

break

Output: 0, 1, 2, 3, 4

PART 4: continue – Skip One Step

What is continue?
It skips the rest of that loop step and jumps to the next one.

🔍 Example 8: Skip 3 in a for loop

for i in range(6):

if i == 3:

continue

print(i)

Output: 0, 1, 2, 4, 5

🔍 Example 9: Skip 4 in a while loop

x = 0

while x < 6:

x += 1

if x == 4:

continue

print(x)

Output: 1, 2, 3, 5, 6

⚠️ Common Mistakes

Mistake

Why it’s wrong

How to fix it

for i in 5:

You must use range()

for i in range(5):

Infinite loop

Forgot to change the loop variable

Use x += 1 inside the loop

🧪 COPY + TEST SECTION

Try running each example above on your computer or online Python tool.
✅ Change the numbers
✅ Change the condition
✅ Add print statements to explain what’s happening

L7 🔴 Independent Practice

🔗 Practice on W3Schools: Loops Tutorials (While loops and For loops) – Learn how to use loops in Python.

🔗 Try It Online: Run Your Code Here – Test your Python code instantly.

🎯 Four Fun Challenges

Print numbers from 1 to 20 using a for loop.
Ask the user to type "go". Use a while loop to keep asking until they write it.
Use a for loop to print numbers from 1 to 10. Stop early if the number is 7.
Use a while loop to count from 1 to 6, but skip the number 4 using continue.

📜 Write by Hand!

Without looking at the lesson or your own code, write the Four Fun Challenges code on paper.

When you have done it, compare your code to the correct code. Did you make any errors?
Correct your code and try to remember what your mistake were so you dont make them again.

Page updated

Google Sites

Report abuse