* `main`: el archivo `main.py` (el"modulo" de Python).
* `app`: el objeto creado dentro de `main.py` con la línea `app = FastAPI()`.
* `--reload`: hace que el servidor se reinicie después de cambios en el código. Esta opción solo debe ser usada en desarrollo.

</details>

### Revísalo

You can use simple tools like `htop` to see the CPU and RAM used in your server or the amount used by each process. Or you can use more complex monitoring tools, which may be distributed across servers, etc.

## Recap

        <directory></directory>
        <includes>
          <include>pom.xml</include>
          <include>src/**</include>
        </includes>
      </resource>
      <resource>
        <directory>src/main/resources</directory>
      </resource>
    </resources>
  </build>

    * New docs at [Dependencies with `yield`](https://fastapi.tiangolo.com/tutorial/dependencies/dependencies-with-yield/).
    * Updated database docs [SQL (Relational) Databases: Main **FastAPI** app](https://fastapi.tiangolo.com/tutorial/sql-databases/#main-fastapi-app).
    * PR [#595](https://github.com/tiangolo/fastapi/pull/595).

    </div>

!!! note
    The command `uvicorn main:app` refers to:

    * `main`: the file `main.py` (the Python "module").
    * `app`: the object created inside of `main.py` with the line `app = FastAPI()`.

    It is equivalent to:

    ```Python
    from main import app
    ```

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

```Python
{!../../../docs_src/first_steps/tutorial001.py!}
```

Copy that to a file `main.py`.

Run the live server:

<div class="termy">

```console
$ <font color="#4E9A06">fastapi</font> dev <u style="text-decoration-style:single">main.py</u>
<font color="#3465A4">INFO    </font> Using path <font color="#3465A4">main.py</font>

        <directory></directory>
        <includes>
          <include>pom.xml</include>
          <include>src/**</include>
        </includes>
      </resource>
      <resource>
        <directory>src/main/resources</directory>
      </resource>
    </resources>
  </build>

### Providing the `root_path`

To achieve this, you can use the command line option `--root-path` like:

<div class="termy">

```console
$ fastapi run main.py --root-path /api/v1

<span style="color: green;">INFO</span>:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
```

</div>

If you use Hypercorn, it also has the option `--root-path`.

### The main app file

Now we create a dependency that returns a new `config.Settings()`.

=== "Python 3.9+"

    ```Python hl_lines="6  12-13"
    {!> ../../../docs_src/settings/app02_an_py39/main.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="6  12-13"
    {!> ../../../docs_src/settings/app02_an/main.py!}
    ```

=== "Python 3.8+ non-Annotated"

To run any of the examples, copy the code to a file `main.py`, and start `fastapi dev` with:

<div class="termy">

```console
$ <font color="#4E9A06">fastapi</font> dev <u style="text-decoration-style:single">main.py</u>
<font color="#3465A4">INFO    </font> Using path <font color="#3465A4">main.py</font>