A boolean value indicating whether this thread is a daemon thread (True) or not (False). This must be set before start() is called, otherwise RuntimeError is raised. Its initial value is inherited from the creating thread; the main thread is not a daemon thread and therefore all threads created in the main thread default to daemon = False.
Yeah, but what the fuck does it do?!?
(The explanation is two pages before the argument; so anyone looking straight for the option will not find out what it does.)
@juliobiason Now I'm curious
@babble_endanger Two pages before that:
A thread can be flagged as a “daemon thread”. The significance of this flag is that the entire Python program exits when only daemon threads are left.
@juliobiason 
All righty then