Error starting .py with roslaunch

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Hi,

I am trying to start a python script to allow keyboard control of two dynamixel MX28T servo motors.

But when I try

roslaunch pantilt pt_keyboard.py

I get the following error message.

"Invalid roslaunch XML syntax: not well-formed (invalid token): line 1, column 1"

I thought first I could not run a .py file with roslaunch. But I saw another guy doing it. I already googled for a solution, but haven't found the answer for my specific problem.

Anybody who has an Idea?

Thanks for helping!