subscriber class not returning value

edit

Here is code

class Robotreacher(object):
    def __init__(self):
        #rospy.init_node('robot_control_node', anonymous=True)
        self._event = threading.Event()
        self.waistp = None
        self.shoulderp = None
        self.elbowp = None
        self.waistv = None
        self.shoulderv = None
        self.elbowv = None

    def joint_callback(self, data):
        self.waistp = math.degrees(data.position[5])+180
        self.shoulderp = abs(math.degrees(data.position[4])-90)
        self.elbowp = abs(math.degrees(data.position[0])-90)
        self.waistv = data.velocity[5]
        self.shoulderv = data.velocity[4]
        self.elbowv = data.velocity[0]
        self._event.set()
        q = [self.waistp, self.shoulderp, self.elbowp, self.waistv, self.shoulderv, self.elbowv]
        #print(q)

    def get_states(self, timeout=None):
        self._event.wait(timeout)
        q = [self.waistp, self.shoulderp, self.elbowp, self.waistv, self.shoulderv, self.elbowv]
        return q

if __name__ == '__main__':
    rospy.init_node('robot_control_node', anonymous=True)
    p = Robotreacher()
    rospy.Subscriber('/rx150/joint_states', JointState, p)
    n = p.get_states()
    print(n)

All the indentations are correct. cannot get the joint states to print nor get their values.