It is equivalent to:

    ```Python
    from main import app
    ```

!!! warning
    Uvicorn and others support a `--reload` option that is useful during development.

    The `--reload` option consumes much more resources, is more unstable, etc.

    It helps a lot during **development**, but you **shouldn't** use it in **production**.

## Hypercorn with Trio

!!! info
    As this is a WebSocket it doesn't really make sense to raise an `HTTPException`, instead we raise a `WebSocketException`.

    You can use a closing code from the <a href="https://tools.ietf.org/html/rfc6455#section-7.4.1" class="external-link" target="_blank">valid codes defined in the specification</a>.

### Try the WebSockets with dependencies

If your file is named `main.py`, run your application with:

<div class="termy">

### Check the docs

Now you can start your app and go to <a href="http://127.0.0.1:8000/docs" class="external-link" target="_blank">http://127.0.0.1:8000/docs</a>.

You will see your docs including a "Callbacks" section for your *path operation* that shows how the *external API* should look like:

# Tutorial - User Guide

This tutorial shows you how to use **FastAPI** with most of its features, step by step.

Each section gradually builds on the previous ones, but it's structured to separate topics, so that you can go directly to any specific one to solve your specific API needs.

It is also built to work as a future reference.

So you can come back and see exactly what you need.

## Run the code