Você o coloca em cima de uma função. Como um chapéu decorativo (acho que é daí que vem o termo).

Um "decorador" pega a função abaixo e faz algo com ela.

Em nosso caso, este decorador informa ao **FastAPI** que a função abaixo corresponde a **rota** `/` com uma **operação** `get`.

É o "**decorador de rota**".

///

Você também pode usar as outras operações:

* `@app.post()`
* `@app.put()`
* `@app.delete()`

```Python
def get_settings():
    return Settings()
```

we would create that object for each request, and we would be reading the `.env` file for each request. ⚠️

But as we are using the `@lru_cache` decorator on top, the `Settings` object will be created only once, the first time it's called. ✔️

{* ../../docs_src/settings/app03_an_py39/main.py hl[1,11] *}

Pero también puedes declarar el `Response` que quieres usar (por ejemplo, cualquier subclase de `Response`), en el *path operation decorator* usando el parámetro `response_class`.

Los contenidos que devuelvas desde tu *path operation function* se colocarán dentro de esa `Response`.

///

## Create a middleware { #create-a-middleware }

To create a middleware you use the decorator `@app.middleware("http")` on top of a function.

The middleware function receives:

* The `request`.
* A function `call_next` that will receive the `request` as a parameter.

 * service. Subclasses should override one or more methods to modify the behavior of the backing
 * executor service as desired per the <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code
 * default} methods. Instead, it inherits their default implementations. When those implementations

#### Определите *декоратор операции пути (path operation decorator)*

{* ../../docs_src/first_steps/tutorial001.py hl[6] *}

Декоратор `@app.get("/")` указывает **FastAPI**, что функция, прямо под ним, отвечает за обработку запросов, поступающих по адресу:

* путь `/`
* использующих <abbr title="HTTP GET метод"><code>get</code> операцию</abbr>

/// info | `@decorator` Дополнительная информация

In solchen Fällen können Sie statt des Rückgabetyps den **Pfadoperation-Dekorator**-Parameter `response_model` verwenden.

Sie können `response_model` in jeder möglichen *Pfadoperation* verwenden:

* `@app.get()`
* `@app.post()`
* `@app.put()`
* `@app.delete()`
* usw.

#### Визначте декоратор операції шляху (path operation decorator)

{* ../../docs_src/first_steps/tutorial001.py hl[6] *}
Декоратор `@app.get("/")` вказує **FastAPI**, що функція нижче, відповідає за обробку запитів, які надходять до неї:

* шлях `/`
* використовуючи <abbr title="an HTTP GET method"><code>get</code> операцію</abbr>

/// info | `@decorator` Додаткова інформація

/// tip | Consejo

Puedes sobreescribir una dependencia utilizada en cualquier lugar de tu aplicación **FastAPI**.

La dependencia original podría ser utilizada en una *path operation function*, un *path operation decorator* (cuando no usas el valor de retorno), una llamada a `.include_router()`, etc.

FastAPI todavía podrá sobrescribirla.

///

But you can also declare the `Response` that you want to be used (e.g. any `Response` subclass), in the *path operation decorator* using the `response_class` parameter.

The contents that you return from your *path operation function* will be put inside of that `Response`.