How to set parameters names for python nodes in roslaunch

edit

Please use the args attribute of the <node> tag. To assist you better, I made a sample code. Please see below:

1. I created my_args.launch file as shown below:

   ravi@dell:~/ros_ws/src/ros_tutorials/rospy_tutorials/001_talker_listener$ cat my_args.launch 
   <launch>
       <node pkg="rospy_tutorials" type="listener.py" name="listener" args="/dev/ttyUSB0" output="screen" />
   </launch>
   

2. I edited the listener.py so that it can capture sys.argv[1] as shown below:

   #!/usr/bin/env python
   # license removed for brevity
   import sys
   import rospy
   from std_msgs.msg import String
   
   def callback(data):
       rospy.loginfo(rospy.get_caller_id() + 'I heard %s', data.data)
   
   def listener(param):
       rospy.init_node('listener', anonymous=True)
       rospy.loginfo('param:' + param)
       rospy.Subscriber('chatter', String, callback)
       rospy.spin()
   
   if __name__ == '__main__':
       listener(sys.argv[1])
   

3. Finally, I ran the launch file. I can see the value in the terminal. Please see below:

   $ roslaunch rospy_tutorials my_args.launch 
   ... logging to /home/ravi/.ros/log/828983fa-2e9e-11ed-bbf8-d707e2da4a66/roslaunch-dell-90235.log
   Checking log directory for disk usage. This may take a while.
   Press Ctrl-C to interrupt
   Done checking log file disk usage. Usage is <1GB.
   
   started roslaunch server http://dell:33681/
   
   SUMMARY
   ========
   
   PARAMETERS
    * /rosdistro: noetic
    * /rosversion: 1.15.14
   
   NODES
     /
       listener (rospy_tutorials/listener.py)
   
   ROS_MASTER_URI=http://localhost:11311
   
   process[listener-1]: started with pid [90264]
   [INFO] [1662549440.441759]: param:/dev/ttyUSB0
   [INFO] [1662549452.298103]: /listenerI heard hello world 1662549452.294159
   [INFO] [1662549452.398594]: /listenerI heard hello world 1662549452.3944724
   [INFO] [1662549452.498860]: /listenerI heard hello world 1662549452.4945526
   [INFO] [1662549452.596540]: /listenerI heard hello world 1662549452.5943813
   

Please note that the original package in this post is taken from ros/ros_tutorials repository.