Custom Exceptions

# The simplest custom exception
class MyCustomError(Exception):
    pass

def check_age(age):
    if age < 0:
        raise ValueError("Age cannot be negative!")

# 1. Define the custom exception by inheriting from Exception
class InsufficientBalanceError(Exception):
    """Exception raised when a withdrawal amount exceeds the account balance."""
    def __init__(self, balance, amount):
        self.balance = balance
        self.amount = amount
        # Pass a descriptive message to the parent Exception class
        super().__init__(f"Attempted to withdraw ${amount} but only have ${balance}")

# 2. Use it in a class or function
class BankAccount:
    def __init__(self, balance):
        self.balance = balance

    def withdraw(self, amount):
        if amount > self.balance:
            # Raise the custom exception
            raise InsufficientBalanceError(self.balance, amount)
        self.balance -= amount
        print(f"Successfully withdrew ${amount}. Remaining balance: ${self.balance}")

# 3. Catch the custom exception
account = BankAccount(100)

try:
    account.withdraw(150)
except InsufficientBalanceError as error:
    print(f"Transaction Failed: {error}")
    # You can access custom attributes defined on the error
    print(f"Current Balance: ${error.balance}")
    print(f"Attempted Withdrawal: ${error.amount}")
    print(f"Shortage Amount: ${error.amount - error.balance}")