You can connect the debugger in your editor, for example with Visual Studio Code or PyCharm.

## Call `uvicorn`

In your FastAPI application, import and run `uvicorn` directly:

```python
import uvicorn
from fastapi import FastAPI

app = FastAPI()


@app.get("/")
def root():
    a = "a"
    b = "b" + a
    return {"hello world": b}


if __name__ == "__main__":
    uvicorn.run(app, host="0.0.0.0", port=8000)
```

### About `__name__ == "__main__"`

The main purpose of the `__name__ == "__main__"` is to have some code that is executed when your file is called with:

```console
$ uv run python myapp.py
```

but is not called when another file imports it, like in:

```Python
from myapp import app
```

#### More details

Let's say your file is named `myapp.py`.

If you run it with:

```console
$ uv run python myapp.py
```

then the internal variable `__name__` in your file, created automatically by Python, will have as value the string `"__main__"`.

So, the section:

```Python
    uvicorn.run(app, host="0.0.0.0", port=8000)
```

will run.

***

This won't happen if you import that module (file).

So, if you have another file `importer.py` with:

```Python
from myapp import app

# Some more code
```

in that case, the automatically created variable `__name__` inside of `myapp.py` will not have the value `"__main__"`.

So, the line:

```Python
    uvicorn.run(app, host="0.0.0.0", port=8000)
```

will not be executed.

:::callout{intent="note"}
For more information, check [the official Python docs](https://docs.python.org/3/library/__main__.html).
:::

## Run your code with your debugger

Because you are running the Uvicorn server directly from your code, you can call your Python program (your FastAPI application) directly from the debugger.

***

For example, in Visual Studio Code, you can:

- Go to the "Debug" panel.
- "Add configuration...".
- Select "Python"
- Run the debugger with the option "`Python: Current File (Integrated Terminal)`".

It will then start the server with your **FastAPI** code, stop at your breakpoints, etc.

Here's how it might look:

<img src="../img/tutorial/debugging/image01.png" alt="">

***

If you use PyCharm, you can:

- Open the "Run" menu.
- Select the option "Debug...".
- Then a context menu shows up.
- Select the file to debug (in this case, `main.py`).

It will then start the server with your **FastAPI** code, stop at your breakpoints, etc.

Here's how it might look:

<img src="../img/tutorial/debugging/image02.png" alt="">

## Related pages

- [About](./about-index.md)
- [Advanced User Guide](./advanced-user-guide-index.md)
- [Deployment](./deployment-index.md)
- [FastAPI](./fastapi-index.md)
- [FastAPI Docs](../index.md)
- [Features](./features-index.md)
- [How To - Recipes](./how-to-recipes-index.md)
- [Learn](./learn-index.md)
- [More](./more-index.md)
- [OpenAPI](./openapi-index.md)

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