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Building a Custom AI Chatbot with LangChain and OpenAI: A Step-by-Step Tutorial

1. Prerequisites and Environment Setup

• Install Python 3.9+ and set up a virtual environment (e.g., python -m venv chatbot-env).
• Obtain an OpenAI API key and store it as an environment variable (OPENAI_API_KEY).
• Install required packages: langchain, openai, streamlit, and python-dotenv.

2. Designing the Conversation Flow

• Map out user intents and system prompts using a decision tree or JSON schema.
• Define a system message that sets the chatbot’s personality and constraints (e.g., “You are a helpful assistant for AI tutorials”).
• Implement a simple loop that captures user input and appends it to the conversation history.

3. Implementing Conversational Memory

• Use LangChain’s ConversationBufferMemory to store recent exchanges and maintain context.
• Set a maximum token limit for memory to avoid exceeding OpenAI’s context window.
• Test memory by asking follow‑up questions that reference earlier parts of the conversation.

4. Building the Chat Interface with Streamlit

• Create a Streamlit app with a text input field and a “Send” button.
• Display the conversation history in a scrollable chat log using st.chat_message.
• Add a “Clear Chat” button that resets both the UI and the memory object.

5. Adding Error Handling and Rate Limiting

• Wrap API calls in try‑except blocks to catch openai.RateLimitError and openai.APIConnectionError.
• Implement exponential backoff using Python’s time.sleep or the tenacity library.
• Display user‑friendly error messages (e.g., “I’m a bit overloaded, please try again in a moment”).

6. Deploying Your Chatbot

• Push the Streamlit app to GitHub and connect it to Streamlit Community Cloud for free hosting.
• Set the OPENAI_API

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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.