---

def on_press(k):
    try:
        held.add(k.char)
    except AttributeError:
        held.add(k)

def on_release(k):
    try:
        held.discard(k.char)
    except AttributeError:
        held.discard(k)

listener = keyboard.Listener(on_press=on_press, on_release=on_release)
listener.start()