Python Watcher/Observer over opened/closed applications

I am trying to build an observer for the system to watch for applications' close/open/minimized/activated events

I was able to build the below observer. However, I was stuck on how to connect it

class AbstractObserver(ABC):
    """ The Observer interface declares the update method, used by subjects. """

    @abstractmethod
    def update(self, ) -> None:
        """ Receive update from subject. """
        pass


class AbstractObserved(ABC):
    """ The Subject interface declares a set of methods for managing subscribers. """
    _state = None
    _observers = {}

    @abstractmethod
    def attach(self, id) -> None:
        pass

    def detach(self, id) -> None:
        """ Detach an observer from the subject."""
        print(f'Task{id} Detach From Observer.')
        try:
            self._observers.pop(id, None)
        except ValueError:
            print(f'Task{id} Not found in observers.')
        pass

    @abstractmethod
    def notify(self, ids, state='create') -> None:
        """ Notify all observers about an event."""
        pass

class ApplicationObserver(AbstractObserver):
    _tracker = None
    _start = None

    def update(self, ) -> None:
        pass


class ObservedApplication(AbstractObserved):
    """ The Subject interface declares a set of methods for managing subscribers. """
    _state = None
    _observers = {}

    def attach(self, id) -> None:
        """ Attach an observer to the subject. """
        pass

    def notify(self, ids: dict, state='create') -> None:
        """ Notify all observers about an event."""
        pass

I am trying to connect it to the generator results from psutil.process_iter() function But, as a generator, there is always an extra step of converting it to a list causing me troubles in the connection