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Connecting a Python client
The power of CARLA simulator resides in its ability to be controlled programmatically with an external client. This client can control most of the aspects of simulation, from environment to duration of each episode, it can retrieve data from different sensors, and send control instructions to the player vehicle.
PythonClient contents
In the release package, inside the "PythonClient" folder, we provide the Python API module together with some use examples.
| File or folder | Description |
|---|---|
| carla/ | Contains the "carla" module, the Python API for communicating with the simulator. |
| client_example.py | Basic usage example of the "carla" module. |
| manual_control.py | A GUI client in which the vehicle can be controlled manually. |
| point_cloud_example.py | Usage example for converting depth images into a point cloud in world coordinates. |
| run_benchmark.py | Run the CoRL'17 benchmark with a trivial agent. |
| view_start_positions.py | Show all the possible start positions in a map |
!!! note
If you are building CARLA from source, the Python code is inside the
"PythonClient" folder in the CARLA repository. Bear in mind that the
master branch contains latest fixes and changes that might be incompatible
with the release version. Consider using the latest release code.
Install dependencies
We recommend using Python 3.5, but all the Python code in the "carla" module and given examples is also compatible with Python 2.7.
Install the dependencies with "pip" using the requirements file provided
$ pip install -r PythonClient/requirements.txt
Running the client example
The "client_example.py" script contains a basic usage example for using the "carla" module. We recommend taking a look at the source-code of this script if you plan to familiarize with the CARLA Python API.
Launching the client
The script tries to connect to a CARLA simulator instance running in server mode. Now we are going to launch the script with "autopilot" enabled
$ ./client_example.py --autopilot
The script now will try repeatedly to connect with the server, since we haven't started the simulator yet it will keep printing an error until we launch the server.
!!! note By default CARLA uses the ports 2000, 2001, and 2002. Make sure to have these ports available.
Launching the simulator in server mode
To launch CARLA simulator in server mode we just need to pass the
-carla-server argument
$ ./CarlaUE4.sh -carla-server
Once the map is loaded, the vehicle should start driving around controlled by the Python script.
!!! important Before you start running your own experiments, it is important to know the details for running the simulator at fixed time-step for achieving maximum speed and repeatability. We will cover this in the next item Configuring the simulation.
Saving images to disk
Now you can stop the client script and relaunch it with different options. For instance now we are going to save to disk the images of the two cameras that the client attaches to the vehicle
$ ./client_example.py --autopilot --images-to-disk
And _"out" folder should have appeared in your working directory containing each captured frame as PNG.
You can see all the available options in the script's help
$ ./client_example.py --help
Running other examples
The other scripts present in the "PythonClient" folder run in a similar fashion. We recommend now launching "manual_control.py" for a GUI interface implemented with PyGame.