atm.py

class ATM:
  def __init__(self):
    self.balance = 0

  def check_balance(self):
    return self.balance

  def deposit(self, amount):
    if amount <= 0:
      raise ValueError('Deposit amount must be positive.')
    
    self.balance += amount
    
  def withdraw(self, amount):
    if amount <= 0:
      raise ValueError('Withdrawal amount must be positive.')
    if amount > self.balance:
      raise ValueError('Insufficient funds.')

    self.balance -= amount

class ATMController:
  def __init__(self):
    self.atm = ATM()

  def get_number(self, prompt):
    while True:
      try:
        number = float(input(prompt))
        return number
      except ValueError:
        print('Please enter a valid number.')

  
  def display_menu(self):
    print('\nWelcome to the ATM!')
    print('1. Check Balance')
    print('2. Deposit')
    print('3. Withdraw')
    print('4. Exit')    

  def check_balance(self):
    balance = self.atm.check_balance()
    print(f'Your current balance is: ${balance}')    

  def deposit(self):
    while True:
      try:
        amount = self.get_number('Enter the amount to deposit: ')
        self.atm.deposit(amount)
        print(f'Successfully deposited ${amount}.')
        break
      except ValueError as error:
        print(error)    

  def withdraw(self):
    while True:
      try:
        amount = self.get_number('Enter the amount to withdraw: ')
        self.atm.withdraw(amount)
        print(f'Successfully withdrew ${amount}.')
        break
      except ValueError as error:
        print(error)    

  def run(self):
    while True: 
      self.display_menu()

      choice = input('Please choose an option: ')
      if choice == '1':
        self.check_balance()
      elif choice == '2':
        self.deposit()
      elif choice == '3':
        self.withdraw()
      elif choice == '4':
        print('Thank you for using the ATM.')
        break
      else:
        print('Invalid choice. Please try again.')


def main():
  atm = ATMController()
  atm.run()


if __name__ == '__main__':
  main()