atm.py

class ATM:
    def __init__(self):
        self._total_twenties = 0
        self._total_fives = 0

    def deposit_twenty(self, amount):
        if amount > 0:
            self._total_twenties += amount
            return f"Deposited {amount * 20} dollars successfully."
        else:
            return "Invalid amount. Please deposit a positive number of twenties."

    def deposit_five(self, amount):
        if amount > 0:
            self._total_fives += amount
            return f"Deposited {amount * 5} dollars successfully."
        else:
            return "Invalid amount. Please deposit a positive number of fives."

    def can_withdraw(self, amount):
        if amount <= 0 or amount % 5 != 0:
            return False, "Invalid amount. Amount must be a positive multiple of 5."

        # Calculate if the withdrawal can be made with available notes
        total_amount = self._total_twenties * 20 + self._total_fives * 5
        if amount > total_amount:
            return False, "Insufficient funds."

        twenties_needed = min(amount // 20, self._total_twenties)
        amount -= twenties_needed * 20
        fives_needed = amount // 5

        if fives_needed > self._total_fives:
            return False, "Cannot dispense the exact amount with available notes."

        return True, "Withdrawal is possible."

    def withdraw(self, amount):
        can_withdraw, message = self.can_withdraw(amount)
        if not can_withdraw:
            return message

        twenties_to_withdraw = min(amount // 20, self._total_twenties)
        self._total_twenties -= twenties_to_withdraw
        amount -= twenties_to_withdraw * 20

        fives_to_withdraw = amount // 5
        self._total_fives -= fives_to_withdraw

        return f"Dispensed {twenties_to_withdraw * 20 + fives_to_withdraw * 5} dollars."

    def __str__(self):
        total_cash = self._total_twenties * 20 + self._total_fives * 5
        return f"ATM has {self._total_twenties} twenty dollar bills and {self._total_fives} five dollar bills: ${total_cash}"

# Example usage:
atm = ATM()
print(atm)  # Initially empty
print(atm.deposit_twenty(10))  # Deposit twenties
print(atm.deposit_five(0))  # Attempt to deposit an invalid amount of fives
print(atm.withdraw(40))  # Withdraw an amount
print(atm.withdraw(15))  # Attempt to withdraw an invalid amount
print(atm)  # Check ATM status after transactions

atm_driver.py

class ATMdriver:
    def __init__(self, atm_machine):
        self.atm_machine = atm_machine

    def display_menu(self):
        print("Please select an option:")
        print("W: withdraw money from the ATM")
        print("T: add twenties to the ATM")
        print("F: add fives to the ATM")
        print("Q: quit")

    def execute_option(self, option):
        option = option.upper()
        if option == 'W':
            self.process_withdrawal()
        elif option == 'T':
            self.process_deposit_twenty()
        elif option == 'F':
            self.process_deposit_five()
        elif option == 'Q':
            self.quit()
        else:
            print("Invalid option selected.")

    def validate_amount(self, amount):
        return amount > 0 and amount % 5 == 0

    def process_withdrawal(self, amount):
        if self.validate_amount(amount):
            print(self.atm_machine.withdraw(amount))
        else:
            print("Invalid amount. Amount must be a positive multiple of 5.")

    def process_deposit_twenty(self, amount):
        if amount > 0:
            print(self.atm_machine.deposit_twenty(amount))
        else:
            print("Invalid amount. Please enter a positive number.")

    def process_deposit_five(self, amount):
        amount = int(input("How many fives do you want to add?\n"))
        if amount > 0:
            print(self.atm_machine.deposit_five(amount))
        else:
            print("Invalid amount. Please enter a positive number.")

    def quit(self):
        print("Quitting program. Final ATM status:")
        print(self.atm_machine)
        exit(0)

# Main interaction loop for the ATMdriver, assuming an ATM instance exists as atm_machine
def main():
    atm_machine = ATM() 
    driver = ATMdriver(atm_machine)

    while True:
        driver.display_menu()
        choice = input("Your choice: ")
        driver.execute_option(choice)
        print("\n")

if __name__ == "__main__":
    main()