How to run an action upon seeing someone who hasn't been trained in?

[Aedanp07]

Hi! I love this amazing face recognizer that you have made, and I play with it so much. There is one thing that I have a question about, though: How do you run an action upon seeing someone who hasn't been trained into the system? Basically, if the AI sees someone, and it isn't ID 1, 2, 3, etc., what ID is it? I know the code for if a certain ID is found, which is:
elif str(id) == "1":
confidence = " {0}%".format(round(100 - confidence))

but no matter how much I have toyed around with the confidence settings, I cant get it to work.
Is there is a fix to this?