How to pass arguments to win32com event handler

The code below works fine. I can't find a way to pass some arguments to EventHandler or to call methods of MainClass from EventHandler. For example instead of using constant param, I'd like to pass it through constructor or setter method. I've tried recommendations from here. But in this case EventHandler instance does not catch any events (or at least nothing appears in stdout).

class EventHandler:
    param = "value"    
    def OnConnected(self):
        print 'connected'
        return True

class MainClass:
    def run(self):
        pythoncom.CoInitialize()
        session = win32com.client.Dispatch("Lib.Obj")
        session_id = pythoncom.CoMarshalInterThreadInterfaceInStream(pythoncom.IID_IDispatch, session)
        args = { 's_id': session_id, }
        thread = threading.Thread(target=self.run_in_thread, kwargs=args)
        thread.start()

    def run_in_thread(self, s_id):
        pythoncom.CoInitialize()
        session = win32com.client.DispatchWithEvent(
            pythoncom.CoGetInterfaceAndReleaseStream(s_id, pythoncom.IID_IDispatch),
            EventHandler
        )
        session.connect()
        while True:
            pythoncom.PumpWaitingMessages()
            time.sleep(1)

if __name__ == '__main__':
    obj = MainClass()
    obj.run()

One possibility is to use WithEvents function. But this may not be the best way. Also now handler and client objects are different entities, so this leads to additional mechanisms of interaction between them.

class EventHandler:

    def set_params(self, client):
        self.client = client

    def OnConnected(self):
        print  "connected!"
        self.client.do_something()
        return True

client = win32com.client.Dispatch("Lib.Obj")
handler = win32com.client.WithEvents(client, EventHandler)
handler.set_client(client)

client.connect()

while True:
    PumpWaitingMessages()
    time.sleep(1)

Here is a complete example.