How to Call a Service from a ROS2 Launch File

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This one is pretty straight forward, but took me a non-trivial amount of searching to find for myself. To call a ros2 service from a ros2 launch file, add the following to your launch file (see the official docs for more on launch files):

from launch.substitutions import FindExecutable
from launch.actions import ExecuteProcess


            " service call ",
            "/namespace/service_to_call ",
            "example_msgs/srv/ExampleMsg ",
            '"{param_1: True, param_2: 0.0}"',

Note the following:

Don't forget to include the shell=True argument, as the command will fail with a confusing "File not found" error without it.