Publish a numpy.array in a UInt8MultiArray in python

edit

Hi all,

Pretty new to python and ROS. I have a node that subscribes to some data, in the callback it then does some calculations on that data and creates a new np.array. I then want to publish this new array in a UInt8MultiArray with a fixed size so that I can receive it with another node and send it over UDP.

The example below doesn't include the calculations but the output of the code at the moment is

[[  31.41386309  292.95704286    2.44705586]]
<type 'numpy.ndarray'>

I need to send these values with a fixed length over a Uint8MultiArray so that I can pack it and send it over UDP. I've tried multiple ways but can't seem to get it to work. I was wondering if someone can help with some example code or ideas/best ways.

#!/usr/bin/env python

import rospy
from std_msgs.msg import UInt8MultiArray
import struct
import math
import numpy as np


def callback(data):
    #Calculations before to create enu with data from callback.
    enu = **
    print(enu)
    print(type(enu))
    pub_packet.publish(gps_enu)

def lla2enu():
    global gps_enu, pub_packet
    rospy.init_node('lla2enu', anonymous=True)
    rate = rospy.Rate(250) # 10hz
    rospy.Subscriber("packet", UInt8MultiArray, callback)
    pub_packet = rospy.Publisher('gps_enu', UInt8MultiArray, queue_size=10)
    rospy.spin()

if __name__ == '__main__':
    try:
        lla2enu()
    except rospy.ROSInterruptException:
        pass

Any help is much appreciated. Thanks guys.