Trying to transmit a 1 by 4 array message to subscriber

edit

I am having trouble trying to publish correctly a 1 by 4 array message generated using a for loop based on test data. My system is a ubuntu 16.04 running Kinetic.
The error occurred in the pub.publish(message) line. Below is my code:

# Import Packages
import sys

sys.path.remove('/opt/ros/kinetic/lib/python2.7/dist-packages')

from raisim_gym.algo.ppo2 import PPO2
import os
import math
import argparse
import pickle

def action2Thrust(mylist):       
    _actionMean = 2.5
    _actionStd = 2

    Newthrust = mylist.astype(float)*_actionStd
    Newthrust += _actionMean
    return Newthrust


# Have to add the path again so that import rospy works. 
sys.path.append('/opt/ros/kinetic/lib/python2.7/dist-packages')

import rospy
from std_msgs.msg import String
from transmit_thrust.msg import ThrustAction


# Function to map the action value to true thrust range none negative to the range between 
# 0.5 to 4.5 scale

if __name__ == '__main__':
    try:
        # configuration
        parser = argparse.ArgumentParser()
        parser.add_argument('-w', '--weight', help='trained weight path', type=str, default='')
        args = parser.parse_args()

        weight_path = args.weight

        if weight_path == "":
            print("Can't find trained weight, please provide a trained weight with --weight switch\n")

        else:

            print("Loaded weight from {}\n".format(weight_path))
            model = PPO2.load(weight_path)

         # Needed to load observations here to test this script would be using pickle here
            with open('/home/ted/raisim_workspace/raisimGym/scripts/obArray.pickle', 'rb') as f:
                obs = pickle.load(f)
         # Needed to instantiate an array to save Thrust for outputting         
            ThrustArray = ThrustAction()
            pub = rospy.Publisher('chatter', ThrustAction, queue_size=10)
            rospy.init_node('talker', anonymous=True)
            rate = rospy.Rate(100) # 10hz

            for i in range(len(obs)):

                action, _ = model.predict(obs[i])
                # print("Action: {}".format(action))

                Thrust = action2Thrust(action)
                # print("Thrust: {}".format(Thrust))

                ThrustArray = Thrust

                while not rospy.is_shutdown():
                    rospy.loginfo(ThrustArray)
                    pub.publish(ThrustArray)
                    rate.sleep()

    except rospy.ROSInterruptException:
        pass

The obs obtain a set of test data in a large array in the form of 18 by 47093, which is 18 columns and 47093 rows. The arrays are fed into a for loop generating individual thrust command of 1 by 4 which are published to the subscriber node. I have tried to replace the line:

ThrustArray = Thrust

to

ThrustArray.action = Thrust

where action is the attribute of ThrustArray.msg which is defined as a float32[]. Below is the error output：

[INFO] [1569343371.533475]: [[0.5
3.76598799 0.6819396 0.91531122]] Traceback (most recent call last):
File "/home/ted/catkin_ws/devel/lib/python2.7/dist-packages/transmit_thrust/msg/_ThrustAction.py", line 55, in serialize buff.write(struct.pack(pattern, *self.action)) struct.error: required argument is not a float

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/opt/ros/kinetic/lib/python2.7/dist-packages/rospy/topics.py", line 882, in publish self.impl.publish(data) File "/opt/ros/kinetic/lib/python2.7/dist-packages/rospy/topics.py", line 1066, in publish serialize_message(b, self.seq, message) File "/opt/ros/kinetic/lib/python2.7/dist-packages/rospy/msg.py", line 152, in serialize_message msg.serialize(b) File ...