While–else behavior in Python - Mini Project: Build & Apply

Understanding While-else Behavior in Python

📖 Scenario: Imagine you are checking a list of numbers to find if any number is divisible by 7. You want to know if you found such a number or if none exists.

🎯 Goal: You will write a Python program that uses a while loop with an else clause to check numbers and print a message depending on whether a divisible number is found.

📋 What You'll Learn

Create a list called numbers with the exact values: [10, 13, 22, 35, 40]

Create a variable called index and set it to 0

Use a while loop with the condition index < len(numbers)

Inside the loop, check if numbers[index] is divisible by 7 using %

If divisible, print Found a number divisible by 7: <number> and break

Use an else clause on the while loop to print No number divisible by 7 found if loop completes without break

Increment index by 1 inside the loop

💡 Why This Matters

🌍 Real World

Checking lists or data for specific conditions and knowing if none matched is common in data processing and validation.

💼 Career

Understanding loop control and the <code>else</code> clause helps in writing clear and efficient code for tasks like searching, filtering, and error checking.

1

Create the list of numbers

Create a list called numbers with these exact values: [10, 13, 22, 35, 40]

Python

# Create the list called numbers with the values [10, 13, 22, 35, 40]
# Your code here

Need a hint?

Use square brackets [] to create a list and separate values with commas.

2

Set up the index variable

Create a variable called index and set it to 0

Python

numbers = [10, 13, 22, 35, 40]
# Create a variable called index and set it to 0
# Your code here

Need a hint?

Use = to assign the value 0 to the variable index.

3

Write the while loop with else

Write a while loop with the condition index < len(numbers). Inside the loop, check if numbers[index] % 7 == 0. If true, print Found a number divisible by 7: {numbers[index]} and use break. Increment index by 1 inside the loop. Add an else clause on the while loop that prints No number divisible by 7 found.

Python

numbers = [10, 13, 22, 35, 40]
index = 0
# Write the while loop with else as described
# Your code here

Need a hint?

Remember the else after a while runs only if the loop did not break.

4

Run the program to see the output

Run the program and print the output. The program should print Found a number divisible by 7: 35.

Python

numbers = [10, 13, 22, 35, 40]
index = 0
while index < len(numbers):
    if numbers[index] % 7 == 0:
        print(f"Found a number divisible by 7: {numbers[index]}")
        break
    index += 1
else:
    print("No number divisible by 7 found")
# Run the program to see the output

Need a hint?

If you see this output, your program works correctly!