# Custom Request and APIRoute class { #custom-request-and-apiroute-class }

In some cases, you may want to override the logic used by the `Request` and `APIRoute` classes.

In particular, this may be a good alternative to logic in a middleware.

For example, if you want to read or manipulate the request body before it is processed by your application.

/// danger

This is an "advanced" feature.

# Request Forms and Files

Puedes definir archivos y campos de formulario al mismo tiempo usando `File` y `Form`.

/// info | Información

Para recibir archivos subidos y/o form data, primero instala <a href="https://github.com/Kludex/python-multipart" class="external-link" target="_blank">`python-multipart`</a>.

Asegúrate de crear un [entorno virtual](../virtual-environments.md){.internal-link target=_blank}, actívalo y luego instálalo, por ejemplo:

Sebastián Ramírez <******@****.***> 1731896744 +0100

Sebastián Ramírez <******@****.***> 1731896744 +0100

Sebastián Ramírez <******@****.***> 1731896744 +0100

	AND	$0x43210000, R4			// AND	$1126236160, R4			// 1e42861484f81400
	AND	$0x43210000, R5, R4		// AND	$1126236160, R5, R4		// 1e428614a4f81400
	AND	$0xffffffffc3210000, R4		// AND	$-1021247488, R4		// 1e42861584f81400
	AND	$0xffffffffc3210000, R5, R4	// AND	$-1021247488, R5, R4		// 1e428615a4f81400

	// AND C_ADDCON, [r1], r2
	AND	$0xfffffffffffffc21, R4		// AND	$-991, R4			// 1e84b00284f81400

Marshmallow and Webargs provide validation, parsing and serialization as plug-ins.

But documentation is still missing. Then APISpec was created.

It is a plug-in for many frameworks (and there's a plug-in for Starlette too).

The way it works is that you write the definition of the schema using YAML format inside the docstring of each function handling a route.

And it generates OpenAPI schemas.

# Concurrency and async / await { #concurrency-and-async-await }

Details about the `async def` syntax for *path operation functions* and some background about asynchronous code, concurrency, and parallelism.

## In a hurry? { #in-a-hurry }

<abbr title="too long; didn't read"><strong>TL;DR:</strong></abbr>

If you are using third party libraries that tell you to call them with `await`, like:

```Python
results = await some_library()
```

                           Version 2.0, January 2004
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      "Licensor" shall mean the copyright owner or entity authorized by

   See the License for the specific language governing permissions and
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                                 Apache License
                           Version 2.0, January 2004
                        http://www.apache.org/licenses/

   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION

   1. Definitions.

      "License" shall mean the terms and conditions for use, reproduction,