Passing arguments to launch file from Python API

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I found a hacky method that works at least in kinetic and possibly a few versions earlier- the roslaunch api for lunar looks to support arguments properly so that ought to be used (and hopefully it gets backported).

(I also described this partially and probably confusingly in https://answers.ros.org/question/1049... )

import sys
...
# override the sys.argv in roslaunch with our own,
# make sure there are no blank '' entries
sys.argv = ['roslaunch', 'foo', 'bar.launch', 'arg1:=234', etc.]
import roslaunch
roslaunch.main()

(In the api it looks like roslaunch.main(argv) ought to work without the sys.argv overriding, but I think the call to main in __init__ keeps that from working?)

It is then possible to put the above into a node and then launch that node like @Cerin describes, and furthermore make the list of args set by args from the scriptapi call (though making that generic to any arbitrary arguments to arbitrary launch files is more work again).

Some similar questions:

programmatic-way-to-stop-roslaunch (already mentioned above)

how-to-launch-a-launch-file-from-python-code

how-to-set-args-with-python-roslaunch

if-it-possible-to-launch-a-launch-file-from-python

parameters-roslaunch-from-python-script

Also programmatic rosrun questions:

start-a-node-from-python-code-rospy-equivalence-rosrun-rosgui-qt

TBD add some others

I've never had much luck digging into ROSLaunchRunner.... would it be okay if you run the roslaunch file as a subprocess of the Python script? You could use os.system or subprocess.Popen with the exact roslaunch command that you want run. I've done that quite a few times successfully.

Just follow the code below:

import roslaunch

cli_args = ['/home/mosaic/catkin_ws/src/robot/launch/id.launch','vel:=2.19']
roslaunch_args = cli_args[1:]
roslaunch_file = [(roslaunch.rlutil.resolve_launch_arguments(cli_args)[0], roslaunch_args)]

parent = roslaunch.parent.ROSLaunchParent(uuid, roslaunch_file)

parent.start()

reference: http://wiki.ros.org/roslaunch/API%20U...

This answer is for Melodic. You'll need to pass the arguments as individual entries in a Python list. To better understand this, take a look at the sample code in the API documentation (roslaunch/API Usage):

import roslaunch

cli_args = ['/home/mosaic/catkin_ws/src/robot/launch/id.launch','vel:=2.19']
roslaunch_args = cli_args[1:]
roslaunch_file = [(roslaunch.rlutil.resolve_launch_arguments(cli_args)[0], roslaunch_args)]

parent = roslaunch.parent.ROSLaunchParent(uuid, roslaunch_file)

parent.start()

cli_args is simply a Python list containing the launch file as list item 0 and arguments after 0, hence cli_args[1:]. Here's a modified version of their example to illustrate:

import roslaunch

arg0 = '/home/mosaic/catkin_ws/src/robot/launch/id.launch'
arg1 = 'vel:=2.19'
arg2 = 'udp_dest:=192.168.2.100'
arg3 = 'mode:=2048'
cli_args = [arg0, arg1, arg2, arg3]
roslaunch_args = cli_args[1:]
roslaunch_file = [(roslaunch.rlutil.resolve_launch_arguments(cli_args)[0], roslaunch_args)]

parent = roslaunch.parent.ROSLaunchParent(uuid, roslaunch_file)

parent.start()

(Note that you'll have to set the uuid for this to work. Just look at how they do it earlier in the document.)

This might be a too late. You can use roslaunch api to do this. See this example for basic usage: http://wiki.ros.org/roslaunch/API%20U...

To remap arguments, as you have asked, you can use args and remap_args as mentioned here: http://docs.ros.org/kinetic/api/rosla...