In this tutorial, we’ll walk through the steps to create a minimal LLM app.

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Prerequisites

Before getting started, make sure you have the following:
  • A working installation of Chainlit
  • Basic understanding of Python programming

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Step 1: Create a Python file

Create a new Python file named app.py in your project directory. This file will contain the main logic for your LLM application.

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Step 2: Write the Application Logic

In app.py, import the Chainlit package and define a function that will handle incoming messages from the chatbot UI. Decorate the function with the @cl.on_message decorator to ensure it gets called whenever a user inputs a message. Here’s the basic structure of the script:
app.py
import chainlit as cl


@cl.on_message
async def main(message: cl.Message):
    # Your custom logic goes here...

    # Send a response back to the user
    await cl.Message(
        content=f"Received: {message.content}",
    ).send()
The main function will be called every time a user inputs a message in the chatbot UI. You can put your custom logic within the function to process the user’s input, such as analyzing the text, calling an API, or computing a result. The Message class is responsible for sending a reply back to the user. In this example, we simply send a message containing the user’s input.

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Step 3: Run the Application

To start your Chainlit app, open a terminal and navigate to the directory containing app.py. Then run the following command: 
chainlit run app.py -w
The -w flag tells Chainlit to enable auto-reloading, so you don’t need to restart the server every time you make changes to your application. Your chatbot UI should now be accessible at http://localhost:8000. PythonExample

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Next Steps

Concepts

Learn about the core concepts of Chainlit

Cookbook

Explore the Chainlit cookbook for more examples