# About FastAPI versions

**FastAPI** is already being used in production in many applications and systems. And the test coverage is kept at 100%. But its development is still moving quickly.

New features are added frequently, bugs are fixed regularly, and the code is still continuously improving.

* You can then modify further the `response` before returning it.

```Python hl_lines="8-9  11  14"
{!../../../docs_src/middleware/tutorial001.py!}
```

!!! tip
    Keep in mind that custom proprietary headers can be added <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers" class="external-link" target="_blank">using the 'X-' prefix</a>.

        ),
    ] = _Unset,
    openapi_examples: Annotated[
        Optional[Dict[str, Example]],
        Doc(
            """
            OpenAPI-specific examples.

            It will be added to the generated OpenAPI (e.g. visible at `/docs`).

            Swagger UI (that provides the `/docs` interface) has better support for the
            OpenAPI-specific examples than the JSON Schema `examples`, that's the main

* If you translate pages, add a single pull request per page translated. That will make it much easier for others to review it.

If you added the return type annotation, tools and editors would complain with a (correct) error telling you that your function is returning a type (e.g. a dict) that is different from what you declared (e.g. a Pydantic model).

It is also commonly used for other applications that don't necessarily need a database, user management, or any of the many features that come pre-built in Django. Although many of these features can be added with plug-ins.

This decoupling of parts, and being a "microframework" that could be extended to cover exactly what is needed was a key feature that I wanted to keep.

So, the prefix in this case is `/items`.

We can also add a list of `tags` and extra `responses` that will be applied to all the *path operations* included in this router.

And we can add a list of `dependencies` that will be added to all the *path operations* in the router and will be executed/solved for each request made to them.

!!! tip

### Order of tags

The order of each tag metadata dictionary also defines the order shown in the docs UI.

For example, even though `users` would go after `items` in alphabetical order, it is shown before them, because we added their metadata as the first dictionary in the list.

## OpenAPI URL

By default, the OpenAPI schema is served at `/openapi.json`.

But you can configure it with the parameter `openapi_url`.

The key updated docs are:

* Python Types Intro:
    * [Type Hints with Metadata Annotations](https://fastapi.tiangolo.com/python-types/#type-hints-with-metadata-annotations).

```

Here, the `shutdown` event handler function will write a text line `"Application shutdown"` to a file `log.txt`.

!!! info
    In the `open()` function, the `mode="a"` means "append", so, the line will be added after whatever is on that file, without overwriting the previous contents.

!!! tip
    Notice that in this case we are using a standard Python `open()` function that interacts with a file.