> In this case, you don't have to use an Event. A boolean attribute on one
> of your objects is enough.
> (similarly, you would use a "volatile" variable in C)

This is already the case with Event. Look at threading.py @line ~355 Event class has a kinda private attribute _flags which is set/unset right before notifying. Using a boolean would look almostly the same so why to reinvent the wheel ? :)

If you look also at is_set(), it has the same meanings than __bool__() (ie returning True or False according to object's status). My suggest is only to had the following two lines:

def __bool__(self):
  return self.is_set()