It is quite an extensive specification and covers several complex use cases.

It includes ways to authenticate using a "third party".

That's what all the systems with "login with Facebook, Google, X (Twitter), GitHub" use underneath.

### OAuth 1 { #oauth-1 }

There was an OAuth 1, which is very different from OAuth2, and more complex, as it included direct specifications on how to encrypt the communication.

But there are situations where you might need to access the `Request` object directly.

## Details about the `Request` object { #details-about-the-request-object }

As **FastAPI** is actually **Starlette** underneath, with a layer of several tools on top, you can use Starlette's <a href="https://www.starlette.dev/requests/" class="external-link" target="_blank">`Request`</a> object directly when you need to.

## HTTPX { #httpx }

Even if your **FastAPI** application uses normal `def` functions instead of `async def`, it is still an `async` application underneath.

func unwrapErrs(err error) (leafErr error) {
	uerr := errors.Unwrap(err)
	depth := 1
	for uerr != nil {
		// Save the current `uerr`
		leafErr = uerr
		// continue to look for leaf errors underneath
		uerr = errors.Unwrap(leafErr)
		depth++
		if depth == unwrapErrsDepth {
			// If we have reached enough depth we
			// do not further recurse down, this
			// is done to avoid any unnecessary

And of course, it supports the same:

* data validation
* data serialization
* data documentation, etc.

This works the same way as with Pydantic models. And it is actually achieved in the same way underneath, using Pydantic.

/// info

Keep in mind that dataclasses can't do everything Pydantic models can do.

So, you might still need to use Pydantic models.

		return http.ErrServerClosed
	}
	srv.listenerMutex.Unlock()

	if atomic.AddUint32(&srv.inShutdown, 1) > 1 {
		// shutdown in progress
		return http.ErrServerClosed
	}

	// Close underneath HTTP listener.
	srv.listenerMutex.Lock()
	err := srv.listener.Close()
	srv.listenerMutex.Unlock()
	if err != nil {
		return err
	}

	// Wait for opened connection to be closed up to Shutdown timeout.

		return deadlineconn.New(result.conn).WithReadDeadline(listener.opts.IdleTimeout).WithWriteDeadline(listener.opts.IdleTimeout), result.err
	case <-listener.ctxDoneCh:
	}
	return nil, syscall.EINVAL
}

// Close - closes underneath all TCP listeners.
func (listener *httpListener) Close() (err error) {
	listener.ctxCanceler()

	for i := range listener.listeners {
		listener.listeners[i].Close()
	}

	return nil
}

`UploadFile` has the following `async` methods. They all call the corresponding file methods underneath (using the internal `SpooledTemporaryFile`).

* `write(data)`: Writes `data` (`str` or `bytes`) to the file.
* `read(size)`: Reads `size` (`int`) bytes/characters of the file.

Because of that, it's now recommended to instead use the `lifespan` as explained above.

## Technical Details { #technical-details }

Just a technical detail for the curious nerds. 🤓

Underneath, in the ASGI technical specification, this is part of the <a href="https://asgi.readthedocs.io/en/latest/specs/lifespan.html" class="external-link" target="_blank">Lifespan Protocol</a>, and it defines events called `startup` and `shutdown`.

Import `SQLModel` and create a database model:

{* ../../docs_src/sql_databases/tutorial001_an_py310.py ln[1:11] hl[7:11] *}

The `Hero` class is very similar to a Pydantic model (in fact, underneath, it actually *is a Pydantic model*).

There are a few differences: