Run a launch script in subscriber callback

edit

I want to spawn a robot B when robot A pass certain location. Currently, my implementation is having a subscriber subscribe to odom of robot A. When robot A odom msg.pose.pose.position>1, run the launch script ( to launch robot B) in callback. I unsubscribe to the node afterwards since I only need to spawn the robot B once. but I was getting the bad call back error.

(a lot of red lines: [ERROR] [1648267836.094904, 23.063000]: bad callback: <function callback="" at="" 0x7f8b743a9310=""> Traceback (most recent call last): File "/opt/ros/noetic/lib/python3/dist-packages/rospy/topics.py", line 750, in _invoke_callback cb(msg) File "/home/xxx/catkin_ws/src/beginner_tutorials/scripts/py_launch.py", line 28, in callback py_launch() )

is it possible to run a launch script in the subscriber callback? or is there a better way to achieve the above?

#! /usr/bin/env python3

import roslaunch
import rospy
from nav_msgs.msg import Odometry


count=0

    def callback(msg):
        global count
        print(msg.pose.pose.position.z)
    if msg.pose.pose.position.z>1:
        count=count+1
    else:
        pass
    print(count)


if count==1:

    count=count+1

    odom_sub.unregister()

    py_launch()


def py_launch():
    uuid = roslaunch.rlutil.get_or_generate_uuid(None, False)
    roslaunch.configure_logging(uuid)
    launch = roslaunch.parent.ROSLaunchParent(uuid, ["/home/xxx/catkin_ws/src/beginner_tutorials/launch/test_replace.launch"])
launch.start()
rospy.loginfo("started")

rospy.sleep(3)


launch.shutdown()

def odom_listen():
    global odom_sub
    odom_sub = rospy.Subscriber('/odom', Odometry, callback)


if __name__ == '__main__':
    rospy.init_node('en_Mapping', anonymous=True)

    odom_listen()


rospy.spin()