Hi,
you're true, we miss an example for integrating both Python and R images with the main image. I've just pushed a commit to let you try and play with Python:
https://github.com/KnowageLabs/Knowage-Server-Docker/commit/b5955a4a2269ee0232b67ca4494fadb2bb1977d4
But I've to tell you that we are working on them because we see some strange behavior: for example, as you will see, the Check Environment button you will see when you create a new Python dataset doesn't work but the preview runs without problem.
Actually, the main image cannot configure itself to use the Python container: you have to set it up on your own. Login on Knowage as biadmin and use the Configuration Management to setup the python.* config: set the url to "http://knowagepython:5000" (where the hostname is the name of the service in the docker-compose.yml).
The next weeks I will probably work on it to automate this.