How to Build a Custom AI Chatbot from Scratch with the OpenAI API

1. Setting Up Your Development Environment

• Create a new Python virtual environment and install the openai and python-dotenv packages.
• Obtain your OpenAI API key from the platform dashboard and store it securely in a .env file.
• Verify your setup with a quick “Hello, AI” request using the ChatCompletion endpoint.

2. Designing the Chatbot’s Base Prompt

• Write a system message that defines the chatbot’s personality, tone, and knowledge boundaries.
• Include clear instructions for handling off-topic or sensitive queries to maintain safety and focus.
• Test a few sample user inputs to refine the prompt until the responses align with your goal.

3. Building the Core Chat Loop

• Implement a simple while loop that captures user input and sends the full conversation history to the API.
• Manage token limits by truncating older messages with a sliding window approach.
• Add graceful exit commands (e.g., “/quit”) and error handling for API rate limits or timeouts.

4. Adding Context Memory with a Local Database

• Choose a lightweight option like SQLite or JSON file to persist conversation history across sessions.
• Store each exchange with timestamps and a session ID so the chatbot can recall past discussions.
• Write helper functions to retrieve and prepend relevant context before sending the API request.

5. Enhancing Responses with Custom Tools (Function Calling)

• Define two example functions: one to fetch live weather data, another to perform mathematical calculations.
• Register these functions with the OpenAI API using the tools parameter in the chat endpoint.
• Parse the API’s function call response, execute the tool locally, and feed the result back into the chat.

6. Deploying as a Web Interface (FastAPI + HTML)

• Set up a FastAPI server with two endpoints: one to render the chat UI and one to handle POST requests for messages.
• Create a minimal HTML page with a text input and a message area, using JavaScript to send and display responses.
• Run

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  Written byTheo Grant

  Theo Grant explores real-world AI applications, automation workflows, and hands-on tutorials at AI In Action Hub. Theo breaks down complex AI concepts into practical guides that help professionals and creators leverage AI in their daily work.