JES while循环是或否

Question

我试图获得一个循环，允许用户选择“是”或“否”，如果不是，程序说无效输入和重复。我每次都得到无效的输入，它不会给我一个“是”或“没有”

def main():
  choice = raw_input("Would you like to open a file? (yes or no) ")
  while true:
    if choice is 'no':
      print("Goodbye")
      break
    elif choice != "yes" or choice != "no":
      print("invalid input")
      break   
    elif choice is 'yes':
      file = get_file()
      image = make_image(file)
      show_image(image)   

def get_file():
  file = pickAFile()
  return file

def make_image(file):
  image = makePicture(file)
  return image

def show_image(image):
  show(image)

main()