{* ../../docs_src/path_params/tutorial001_py39.py hl[6:7] *}

El valor del parámetro de path `item_id` se pasará a tu función como el argumento `item_id`.

Así que, si ejecutas este ejemplo y vas a <a href="http://127.0.0.1:8000/items/foo" class="external-link" target="_blank">http://127.0.0.1:8000/items/foo</a>, verás un response de:

```JSON
{"item_id":"foo"}

            when(mockTree.isSMB2()).thenReturn(false);
            when(mockFile.getType()).thenReturn(SmbConstants.TYPE_NAMED_PIPE);

            // Cause send to throw to stop execution so we can verify arguments
            doAnswer(inv -> {
                throw new SmbException("stop");
            }).when(mockTree)
                    .send(any(jcifs.internal.CommonServerMessageBlockRequest.class),

///

Lo único nuevo es `callbacks=invoices_callback_router.routes` como un argumento para el *decorador de path operation*. Veremos qué es eso a continuación.

## Documentar el callback { #documenting-the-callback }

El código real del callback dependerá mucho de tu propia aplicación API.

    /** Empty headers. */
    @JvmField
    val EMPTY = Headers(emptyArray())

    /**
     * Returns headers for the alternating header names and values. There must be an even number of
     * arguments, and they must alternate between header names and values.
     */
    @JvmStatic
    @JvmName("of")
    fun headersOf(vararg namesAndValues: String): Headers = commonHeadersOf(*namesAndValues)

#### Über `**user_dict` { #about-user-dict }

`UserInDB(**user_dict)` bedeutet:

*Übergib die Schlüssel und Werte des `user_dict` direkt als Schlüssel-Wert-Argumente, äquivalent zu:*

```Python
UserInDB(
    username = user_dict["username"],
    email = user_dict["email"],
    full_name = user_dict["full_name"],
    disabled = user_dict["disabled"],

{* ../../docs_src/security/tutorial003_an_py310.py hl[82:85] *}

#### About `**user_dict` { #about-user-dict }

`UserInDB(**user_dict)` means:

*Pass the keys and values of the `user_dict` directly as key-value arguments, equivalent to:*

```Python
UserInDB(
    username = user_dict["username"],
    email = user_dict["email"],
    full_name = user_dict["full_name"],
    disabled = user_dict["disabled"],

	"none":   sarama.CompressionNone,
	"gzip":   sarama.CompressionGZIP,
	"snappy": sarama.CompressionSnappy,
	"lz4":    sarama.CompressionLZ4,
	"zstd":   sarama.CompressionZSTD,
}

// KafkaArgs - Kafka target arguments.
type KafkaArgs struct {
	Enable             bool          `json:"enable"`
	Brokers            []xnet.Host   `json:"brokers"`
	Topic              string        `json:"topic"`

l(t,e,n){return e&&s(t.prototype,e),n&&s(t,n),Object.defineProperty(t,"prototype",{writable:!1}),t}function r(){return r=Object.assign?Object.assign.bind():function(t){for(var e=1;e<arguments.length;e++){var n=arguments[e];for(var i in n)Object.prototype.hasOwnProperty.call(n,i)&&(t[i]=n[i])}return t},r.apply(this,arguments)}function u(t,e){return u=Object.setPrototypeOf?Object.setPrototypeOf.bind():function(t,e){return t.__proto__=e,t},u(t,e)}var f="transitionend";var d={TRANSITION_END:"bsTransitio...

Por ejemplo, podrías tener un archivo `main.py` con:

```Python hl_lines="3"
import os

name = os.getenv("MY_NAME", "World")
print(f"Hello {name} from Python")
```

/// tip | Consejo

El segundo argumento de <a href="https://docs.python.org/3.8/library/os.html#os.getenv" class="external-link" target="_blank">`os.getenv()`</a> es el valor por defecto a retornar.

Os seguintes argumentos são suportados: