utils.py

def print_message():
  print('I\'m sorry, I did not understand your selection. Please enter the corresponding letter for your response.')
  
def get_size():
  res = input('What size drink can I get for you? \n[a] Small \n[b] Medium \n[c] Large \n> ')
  
  if res == 'a':
    return 'small'
  elif res == 'b':
    return 'medium'
  elif res == 'c':
    return 'large'
  else:
    print_message()
    return get_size()

def order_latte():
  res = input('And what kind of milk for your latte? \n[a] 2% milk \n[b] Non-fat milk \n[c] Soy milk \n> ')

  if res == 'a':
    return 'latte'
  elif res == 'b':
    return 'non-fat latte'
  elif res == 'c':
    return 'soy latte'
  else:
    print_message()
    return order_latte()

def order_mocha():

  while True:
    res = input('Would you like to try our limited-edition peppermint mocha? \n[a]Sure! \n[b]Maybe next time! \n> ')
    if res == 'a':
      return 'peppermint mocha'
    elif res == 'b':
      return 'mocha'
    else:
      print_message()