Also, there might be tools that expect and use it (now or in the future) and that might be useful for you or your users, now or in the future.

That's the benefit of standards...

///

## See it in action { #see-it-in-action }

Open the interactive docs: <a href="http://127.0.0.1:8000/docs" class="external-link" target="_blank">http://127.0.0.1:8000/docs</a>.

Esto no es una limitación de **FastAPI**, es parte del protocolo HTTP.

///

## Subida de Archivos Opcional

Puedes hacer un archivo opcional utilizando anotaciones de tipos estándar y estableciendo un valor por defecto de `None`:

{* ../../docs_src/request_files/tutorial001_02_an_py310.py hl[9,17] *}

## `UploadFile` con Metadatos Adicionales

    By doing it this way, we can put it in a `with` block, and that way, ensure that the file-like object is closed after finishing.

/// tip

Notice that here as we are using standard `open()` that doesn't support `async` and `await`, we declare the path operation with normal `def`.

///

### `FileResponse` { #fileresponse }

Asynchronously streams a file as the response.

Starlette (and **FastAPI**) are based on <a href="https://anyio.readthedocs.io/en/stable/" class="external-link" target="_blank">AnyIO</a>, which makes it compatible with both Python's standard library <a href="https://docs.python.org/3/library/asyncio-task.html" class="external-link" target="_blank">asyncio</a> and <a href="https://trio.readthedocs.io/en/stable/" class="external-link" target="_blank">Trio</a>.

	directoryHeaderSignature = 0x02014b50
	directoryEndSignature    = 0x06054b50
	directory64LocSignature  = 0x07064b50
	directory64EndSignature  = 0x06064b50
	dataDescriptorSignature  = 0x08074b50 // de-facto standard; required by OS X Finder
	fileHeaderLen            = 30         // + filename + extra
	directoryHeaderLen       = 46         // + filename + extra + comment
	directoryEndLen          = 22         // + comment

		if f == "" || len(f)%2 != 0 || strings.TrimLeft(f, "0123456789abcdef") != "" {
			return false
		}
	}
	return true
}

// It would be nice if the error messages always began with
// the standard file:line: prefix,
// but that's not where we are today.
// It might be at the beginning but it might be in the middle of the printed instruction.

  @InlineMe(replacement = "Boolean.hashCode(value)")
  public static int hashCode(boolean value) {
    return Boolean.hashCode(value);
  }

  /**
   * Compares the two specified {@code boolean} values in the standard way ({@code false} is
   * considered less than {@code true}). The sign of the value returned is the same as that of
   * {@code ((Boolean) a).compareTo(b)}.
   *

  @InlineMe(replacement = "Boolean.hashCode(value)")
  public static int hashCode(boolean value) {
    return Boolean.hashCode(value);
  }

  /**
   * Compares the two specified {@code boolean} values in the standard way ({@code false} is
   * considered less than {@code true}). The sign of the value returned is the same as that of
   * {@code ((Boolean) a).compareTo(b)}.
   *

///

For example, this custom validator checks that the item ID starts with `isbn-` for an <abbr title="ISBN means International Standard Book Number">ISBN</abbr> book number or with `imdb-` for an <abbr title="IMDB (Internet Movie Database) is a website with information about movies">IMDB</abbr> movie URL ID:

<div class="termy">

```console
$ pip install uvicorn[standard]

---> 100%
```

</div>

## Приклад

### Створіть

* Створіть файл `main.py` з:

```Python
from typing import Union

from fastapi import FastAPI