<blockquote markdown="1">

**FastAPI** wouldn't exist if not for the previous work of others.

There have been many tools created before that have helped inspire its creation.

I have been avoiding the creation of a new framework for several years. First I tried to solve all the features covered by **FastAPI** using many different frameworks, plug-ins, and tools.

!!! check "Inspired **FastAPI** to"
    Find ways to get great performance.

    Along with Hug (as Hug is based on Falcon) inspired **FastAPI** to declare a `response` parameter in functions.

code {
  direction: ltr;
  display: inline-block;
}

.illustration {
  margin-top: 2em;
  margin-bottom: 2em;
}

/* Screenshots */
/*
Simulate a browser window frame.
Inspired by Termynal's CSS tricks with modifications
*/

.screenshot {
  display: block;
  background-color: #d3e0de;
  border-radius: 4px;
  padding: 45px 5px 5px;
  position: relative;

But there are specific cases where it's useful to get the `Request` object.

## Use the `Request` object directly

Let's imagine you want to get the client's IP address/host inside of your *path operation function*.

For that you need to access the request directly.

```Python hl_lines="1  7-8"
{!../../../docs_src/using_request_directly/tutorial001.py!}
```

* It contains an `app/main.py` file. As it is inside a Python package (a directory with a file `__init__.py`), it is a "module" of that package: `app.main`.
* There's also an `app/dependencies.py` file, just like `app/main.py`, it is a "module": `app.dependencies`.
* There's a subdirectory `app/routers/` with another file `__init__.py`, so it's a "Python subpackage": `app.routers`.

    },
    "user": {
        "username": "dave",
        "full_name": "Dave Grohl"
    }
}
```

!!! note
    Notice that even though the `item` was declared the same way as before, it is now expected to be inside of the body with a key `item`.


**FastAPI** will do the automatic conversion from the request, so that the parameter `item` receives it's specific content and the same for `user`.

#### Union

You can declare that a variable can be any of **several types**, for example, an `int` or a `str`.

In Python 3.6 and above (including Python 3.10) you can use the `Union` type from `typing` and put inside the square brackets the possible types to accept.

    But this example is still valid and it shows how to interact with the internal components.

We can also use this same approach to access the request body in an exception handler.

All we need to do is handle the request inside a `try`/`except` block:

```Python hl_lines="13  15"
{!../../../docs_src/custom_request_and_route/tutorial002.py!}
```

If you are not familiar with the `f"userprofile::{username}"`, it is a Python "<a href="https://docs.python.org/3/glossary.html#term-f-string" class="external-link" target="_blank">f-string</a>".

Any variable that is put inside of `{}` in an f-string will be expanded / injected in the string.

### `dict` unpacking

Create metadata for your tags and pass it to the `openapi_tags` parameter:

```Python hl_lines="3-16  18"
{!../../../docs_src/metadata/tutorial004.py!}
```

Notice that you can use Markdown inside of the descriptions, for example "login" will be shown in bold (**login**) and "fancy" will be shown in italics (_fancy_).

!!! tip
    You don't have to add metadata for all the tags that you use.

### Use your tags