Custom Exceptions (Enhanced)

# ===== 1. Basic Custom Exception =====
class MyError(Exception):
    """Custom exception class"""
    pass

try:
    raise MyError("Something went wrong")
except MyError as e:
    print(f"Caught custom error: {e}")

# ===== 2. Adding Attributes =====
print(f"\n===== Exception with Attributes =====")

class ValidationError(Exception):
    def __init__(self, field, message):
        self.field = field
        self.message = message
        super().__init__(f"{field}: {message}")

try:
    raise ValidationError("username", "must not be empty")
except ValidationError as e:
    print(f"Error in {e.field} - {e.message}")

# ===== 3. Hierarchy of Custom Exceptions =====
print(f"\n===== Exception Hierarchy =====")

class AppError(Exception):
    """Base class for app errors"""
    pass

class DatabaseError(AppError):
    pass

class AuthenticationError(AppError):
    pass

try:
    raise AuthenticationError("Invalid password")
except AppError as e:
    print(f"App error: {e}")

# ===== 4. Real-World Example: Bank Account =====
print(f"\n===== Bank Account Example =====")

class InsufficientFundsError(Exception):
    pass

class BankAccount:
    def __init__(self, balance):
        self.balance = balance

    def withdraw(self, amount):
        if amount > self.balance:
            raise InsufficientFundsError("Not enough balance")
        self.balance -= amount
        return self.balance

try:
    account = BankAccount(100)
    account.withdraw(200)
except InsufficientFundsError as e:
    print(f"Withdrawal failed: {e}")