As my colleague mentioned market_price_edpgw_service_discovery.py is purely an example. We provide the source code for these examples so that developers can learn from them and potentially modify them as per their requirements.
In order to specify multiple RICs on the command line, you would make the necessary changes to allow for your requirement - this would be standard python code related reading command line parameters - nothing specific to the Websocket API interface.
Once you have made the changes to read multiple RICs from the command line, you can then refer to the Batch Websocket API Batch Request tutorial on how to change the JSON request message payload to request those multiple RICs.
You can also refer to the pywstestclient example on Github which allows comma-separated RICs on the command line and then uses them for a batch request. Note that this example does not perform service discovery and requires you to specify a specific EDP endpoint hostname.
To try out batch request feature (multiple RIC's), you can edit the python source code, and specify the ric variable as JSON Array. For e.g:
ric = ['CAD=','/DIS.N']