class Event: 
    def __init__(self, name): 
        self.name = name 

    def __str__(self): 
        return self.name 

class Widget: 
    def __init__(self, parent=None): 
        self.parent = parent 

    def handle(self, event): 
        handler = f'handle_{event}' 
        if hasattr(self, handler): 
            method = getattr(self, handler) 
            method(event) 
        elif self.parent is not None: 
            self.parent.handle(event) 
        elif hasattr(self, 'handle_default'): 
            self.handle_default(event) 

class MainWindow(Widget): 
    def handle_close(self, event): 
        print(f'MainWindow: {event}') 

    def handle_default(self, event): 
        print(f'MainWindow Default: {event}') 

class SendDialog(Widget): 
    def handle_paint(self, event): 
        print(f'SendDialog: {event}') 

class MsgText(Widget): 
    def handle_down(self, event): 
        print(f'MsgText: {event}') 

def main(): 
    mw = MainWindow() 
    sd = SendDialog(mw) 
    msg = MsgText(sd) 

    for e in ('down', 'paint', 'unhandled', 'close'): 
        evt = Event(e) 
        print(f'Sending event -{evt}- to MainWindow') 
        mw.handle(evt) 
        print(f'Sending event -{evt}- to SendDialog') 
        sd.handle(evt) 
        print(f'Sending event -{evt}- to MsgText') 
        msg.handle(evt) 

if __name__ == '__main__': 
    main()