Unable to run script using rosrun, how do I solve this? none of the scripts can run because of this issue [closed]

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Hi, beginner trying to learn to use ROS here, I'm trying to learn how to run python scripts in rosrun

$ rosrun my_robotics talker.py Traceback (most recent call last): File "/home/snuc/catkin_ws/src/my_robotics/src/talker.py", line 3, in <module> import rospy File "/home/snuc/catkin_ws/devel/lib/python2.7/dist-packages/rospy/__init__.py", line 34, in <module> exec(__fh.read()) File "<string>", line 47, in <module> ImportError: No module named msg