Why does this error comes?

Course Support ROS Beginners Exam
4

Yes.

You have imported two differrent Empty objects, so the last one imported wins. You should import (and use) the second one with another name. E.g:

from std_msgs.msg import Empty as EmptyMsg

Other suggestions:

  • Create the service last, just before rospy.spin(), so that all the global variables used with the callback will already exist.
  • Remove the rate object - it’s useless here: Proper use of rospy.Rate or ros::Rate
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