trying to get joint data from subscriber class function

edit

Here is the code

class Arm:
    def __init__(self):
        self.sub = rospy.Subscriber('/rx150/joint_states', JointState, self.callback)

    def 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]

    def return_waistp(self):
        return self.waistp

Here is the code I used to try to extract the data

arm = Arm()
print("joints states are", arm.return_waistp())

Below is the error I am getting

AttributeError: 'Arm' object has no attribute 'waistp'

here is new code

class Arm:
def __init__(self):
    self.sub = rospy.Subscriber('/rx150/joint_states', JointState, self.callback)
    self.waistp = None
    self.shoulderp = None
    self.elbowp = None
    self.waistv = None
    self.shoulderv = None
    self.elbowv = None

    self.is_everything_initialized = False
    rospy.spin()

def callback(self, data):
    if self.is_everything_initialized == False:
        self.is_everything_initialized = True
    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]

def joint_states(self):
    if self.is_everything_initialized:
        joint_states = [self.waistp, self.shoulderp, self.elbowp, self.waistv, self.shoulderv, self.elbowv]
        return joint_states
    else:
        joint_statesn = [0, 0, 0, 0, 0, 0]
        return joint_statesn

def simulate(episode, is_training): #global waistp, shoulderp, elbowp, waistv, shoulderv, elbowv

reward = 0
max_step = 20
is_done = False
episode_reward = 0
obs = np.array([0, 0, 0, 0, 0, 0, 0, 0, 0], dtype='float16')
next_obs = np.array([0, 0, 0, 0, 0, 0, 0, 0, 0], dtype='float16')
x_target = math.cos(math.radians(episode*6))*200
y_target = math.sin(math.radians(episode*6))*200
z_target = 250
waist_force = 0
shoulder_force = 0
elbow_force = 0
arm = Arm()
print("joints states are", arm.joint_states())
x = arm.joint_states()
waistp = x[0]
shoulderp = x[1]
elbowp = x[2]
waistv = x[3]
shoulderv = x[4]
elbowv = x[5]

joint states stay [0,0,0,0,0,0] though they are not updating