And then we use it when creating the `FastAPI` app.

Then you could disable OpenAPI (including the UI docs) by setting the environment variable `OPENAPI_URL` to the empty string, like:

<div class="termy">

```console
$ OPENAPI_URL= uvicorn main:app

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

</div>

    ```

* `description: Union[str, None] = None` (or `str | None = None` in Python 3.10) has a default of `None`.
* `tax: float = 10.5` has a default of `10.5`.
* `tags: List[str] = []` has a default of an empty list: `[]`.

but you might want to omit them from the result if they were not actually stored.

    For example, in `app/main.py` you could have a line like:

    ```
    from app.routers import items
    ```

* The `app` directory contains everything. And it has an empty file `app/__init__.py`, so it is a "Python package" (a collection of "Python modules"): `app`.

```Python hl_lines="23-29"
{!../../../docs_src/sql_databases_peewee/sql_app/main.py!}
```

Here we have an empty `yield` because we are actually not using the database object directly.

### Fixes

* 🐛 Fix `RuntimeError` raised when `HTTPException` has a status code with no content. PR [#5365](https://github.com/tiangolo/fastapi/pull/5365) by [@iudeen](https://github.com/iudeen).
* 🐛 Fix empty reponse body when default `status_code` is empty but the a `Response` parameter with `response.status_code` is set. PR [#5360](https://github.com/tiangolo/fastapi/pull/5360) by [@tmeckel](https://github.com/tmeckel).

### Docs

    FastAPI will still be able to override it.

Then you can reset your overrides (remove them) by setting `app.dependency_overrides` to be an empty `dict`:

```Python
app.dependency_overrides = {}
```

!!! tip

```
.
└── sql_app
    ├── __init__.py
    ├── crud.py
    ├── database.py
    ├── main.py
    ├── models.py
    └── schemas.py
```

The file `__init__.py` is just an empty file, but it tells Python that `sql_app` with all its modules (Python files) is a package.

Now let's see what each file/module does.

## Install `SQLAlchemy`

First you need to install `SQLAlchemy`:

```

</div>

!!! info
    There are other formats and tools to define and install package dependencies.

### Create the **FastAPI** Code

* Create an `app` directory and enter it.
* Create an empty file `__init__.py`.
* Create a `main.py` file with:

```Python
from typing import Union

from fastapi import FastAPI

app = FastAPI()


@app.get("/")
def read_root():