Custom Exceptions

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

class InsufficientFundsError(Exception):
    def __init__(self, balance, amount):
        self.balance = balance
        self.amount = amount
        super().__init__(f"Need ${amount}, have ${balance}")

# Using custom exceptions
def validate_age(age):
    if not isinstance(age, int):
        raise ValidationError("age", "Must be an integer")
    if age < 0 or age > 150:
        raise ValidationError("age", "Must be 0-150")
    return age

def withdraw(balance, amount):
    if amount > balance:
        raise InsufficientFundsError(balance, amount)
    return balance - amount

# Handling custom exceptions
try:
    validate_age(-5)
except ValidationError as e:
    print(f"Validation failed: {e}")

try:
    new_balance = withdraw(100, 500)
except InsufficientFundsError as e:
    print(f"Transaction failed: {e}")
    print(f"  Deficit: ${e.amount - e.balance}")