You can use the LangChain framework to build an AI assistant on WhatsApp with Python, OpenAI, and Twilio. The assistant uses a Wikipedia tool to search for information related to user queries and provides real-time answers based on up-to-date information from Wikipedia. To set up the backend, you need to configure your Twilio Sandbox for WhatsApp, create a new file called utils.py that handles sending messages through the Twilio Messaging API, and update the main.py script with the logic for sending WhatsApp messages to the OpenAI API. The assistant stores conversations in a PostgreSQL database using SQLAlchemy.