Using the Python JSON engine

The Python JSON engine can be used to easily integrate simulators with a Python API. There is a minimal working example with two Python JSON engines exchanging simulation time, located in examples/tf_exchange directory. We explain how to run it on this page.

In order to create your engine, you can use examples/tf_exchange/engine_1.py (listed below) as a reference. Just modify the following methods of the Script class to suit your needs:

• initialize(): executed when the engine is initialized
• runLoop(timestep): executed when the engine is requested to advance its simulation (from EngineClient::runLoopStep)
• shutdown(): executed when the engine is requested to shutdown

"""Python Engine 1. Will get current engine time and make it accessible as a datapack"""
 
from nrp_core.engines.python_json import EngineScript
 
 
class Script(EngineScript):
    def initialize(self):
        """Initialize datapack1 with time"""
        print("Engine 1 is initializing. Registering datapack...")
        self._registerDataPack("datapack1")
        self._setDataPack("datapack1", {"time": self._time_ns, "timestep": 0 })
 
    def runLoop(self, timestep_ns):
        """Update datapack1 at every timestep"""
        self._setDataPack("datapack1", {"time": self._time_ns, "timestep": timestep_ns })
        print("DataPack 1 data is " + str(self._getDataPack("datapack1")))
 
    def shutdown(self):
        print("Engine 1 is shutting down")
 
    def reset(self):
        print("Engine 1 is resetting")

More details about the EngineScript and other Python JSON engine components can be found here.