Creating exception classes in Python - Try It Yourself

Creating exception classes

📖 Scenario: Imagine you are building a simple banking system. You want to handle errors like when someone tries to withdraw more money than they have.

🎯 Goal: You will create a custom exception class called InsufficientFundsError to handle this specific error. Then you will use it in a function that withdraws money from an account.

📋 What You'll Learn

Create a custom exception class named InsufficientFundsError that inherits from Exception.

Create a variable balance with the value 100.

Create a variable withdraw_amount with the value 150.

Write a function withdraw that takes amount as a parameter.

Inside the function, raise InsufficientFundsError with the message 'Not enough money in the account' if amount is greater than balance.

Call the withdraw function with withdraw_amount inside a try block.

Catch the InsufficientFundsError exception and print its message.

💡 Why This Matters

🌍 Real World

Custom exceptions help you handle specific errors in your programs clearly, like when a bank account has insufficient funds.

💼 Career

Knowing how to create and use custom exceptions is important for writing robust software that handles errors gracefully in real-world applications.

1

Create the custom exception class

Create a custom exception class called InsufficientFundsError that inherits from Exception.

Python

# Your code here

Need a hint?

Use class InsufficientFundsError(Exception): and add pass inside.

2

Set up balance and withdraw amount

Create a variable called balance and set it to 100. Then create a variable called withdraw_amount and set it to 150.

Python

class InsufficientFundsError(Exception):
    pass

# Your code here

Need a hint?

Use simple assignment like balance = 100 and withdraw_amount = 150.

3

Write the withdraw function with exception

Write a function called withdraw that takes a parameter amount. Inside the function, if amount is greater than balance, raise InsufficientFundsError with the message 'Not enough money in the account'.

Python

class InsufficientFundsError(Exception):
    pass

balance = 100
withdraw_amount = 150

# Your code here

Need a hint?

Use def withdraw(amount): and inside check if amount > balance: then raise InsufficientFundsError('Not enough money in the account').

4

Call withdraw and handle exception

Call the withdraw function with withdraw_amount inside a try block. Catch the InsufficientFundsError exception and print its message.

Python

class InsufficientFundsError(Exception):
    pass

balance = 100
withdraw_amount = 150

def withdraw(amount):
    if amount > balance:
        raise InsufficientFundsError('Not enough money in the account')

# Your code here

Need a hint?

Use try: to call withdraw(withdraw_amount) and except InsufficientFundsError as e: to print e.