Code 3

...class Presence:
    def handle_ISONLINE(self, username):
        if self.state != 'loggedin':
            self.sendLine('ERROR')
            return
        if self.factory.userOnline(username):
            self.sendLine('YES')
        else:
            self.sendLine('NO')

    def connectionLost(self, reason):
        if self.state == 'loggedin':
            u = self.username
            self.factory.removeUser(u)