In this video we show how to get the model state of a model in Gazebo using ROS Topics with Python. See question: https://answers.ros.org/question/261782/how-to-use-getmodelstate-service-from-gazebo-in-python/

Q: I try to get the state of a model in Gazebo but the returned value is always zero.

A: You have to call the /gazebo/get_model_state service passing the name of the model and the name of a link.