Code 4

class PresenceFactory(protocol.ServerFactory):
    # used by default buildProtocol:
    protocol = Presence
    
    def __init__(self):
        self.users = {}

    def addUser(self, user):
        self.users[user] = 1

    def removeUser(self, user):
        del self.users[user]

    def userOnline(self, user):
        return self.users.has_key(user)