Finding robot's position within slam_gmapping map in python

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I am relatively new to ROS. I am trying to move a turtlebot around using slam_gmapping in python. I can get the occupancy grid just fine, using a dynamic_map client via rospy. However, I cannot for the life of me figure out how to get the robot's position and orientation within that occupancy grid. I have spent about twenty hours on this and all of the help I can find is about how to run some ROS demo that will do it, but I cannot find anything talking about what topics publish this, or how to do this in python. Can someone please point me in the right direction? Thanks so much!