Exception chaining in Python - Mini Project: Build & Apply

Exception chaining

📖 Scenario: Imagine you are writing a program that reads numbers from a list and divides 100 by each number. Sometimes, the numbers might cause errors like division by zero or invalid data types.

🎯 Goal: You will create a program that uses try and except blocks to catch errors and use exception chaining to show the original error when a new error is raised.

📋 What You'll Learn

Create a list called numbers with the values 10, 0, 'a', and 5

Create a variable called results and set it to an empty list

Use a for loop with variable num to iterate over numbers

Inside the loop, use a try block to divide 100 by num

If an exception occurs, catch it as e and raise a new ValueError with the message 'Invalid number: {num}' using exception chaining

Append the division result to results if no exception occurs

Print the results list at the end

💡 Why This Matters

🌍 Real World

Exception chaining helps programmers understand the root cause of errors while providing clearer messages. This is useful in debugging real applications where multiple errors can happen.

💼 Career

Knowing how to use exception chaining is important for writing robust Python code that is easier to maintain and debug in professional software development.

1

Create the list of numbers

Create a list called numbers with these exact values: 10, 0, 'a', and 5

Python

# Create the list called numbers with 10, 0, 'a', and 5
# Your code here

Need a hint?

Use square brackets to create a list with the exact values in order.

2

Create an empty list to store results

Create a variable called results and set it to an empty list []

Python

numbers = [10, 0, 'a', 5]
# Create an empty list called results
# Your code here

Need a hint?

Use empty square brackets to create an empty list.

3

Use a for loop with try-except and exception chaining

Use a for loop with variable num to iterate over numbers. Inside the loop, use a try block to divide 100 by num and append the result to results. If an exception occurs, catch it as e and raise a new ValueError with the message f'Invalid number: {num}' using exception chaining with from e.

Python

numbers = [10, 0, 'a', 5]
results = []
# Use a for loop with num to iterate over numbers
# Inside the loop, use try-except to divide 100 by num
# Append the result to results
# If exception occurs, raise ValueError with chaining
# Your code here

Need a hint?

Remember to use 'from e' after raising the new ValueError to chain exceptions.

4

Print the results list

Write print(results) to display the list of successful division results after the loop.

Python

numbers = [10, 0, 'a', 5]
results = []
for num in numbers:
    try:
        result = 100 / num
    except Exception as e:
        raise ValueError(f'Invalid number: {num}') from e
    else:
        results.append(result)
# Print the results list
# Your code here

Need a hint?

The print should show the list with the results of dividing 100 by 10 and 5 only.