## Retornar una `Response` directamente

Adicionalmente, puedes añadir headers cuando se retorne una `Response` directamente.

Crea un response tal como se describe en [Retornar una respuesta directamente](response-directly.md){.internal-link target=_blank} y pasa los headers como un parámetro adicional:

```Python hl_lines="10-12"
{!../../../docs_src/response_headers/tutorial001.py!}
```

We will talk a lot about the running "**process**", so it's useful to have clarity about what it means, and what's the difference with the word "**program**".

### What is a Program

The word **program** is commonly used to describe many things:

* The **code** that you write, the **Python files**.
* The **file** that can be **executed** by the operating system, for example: `python`, `python.exe` or `uvicorn`.

That means that, clients using your API don't have to check if the value exists or not, they can **assume the field will always be there**, but just that in some cases it will have the default value of `None`.

The way to describe this in OpenAPI, is to mark that field as **required**, because it will always be there.

Because of that, the JSON Schema for a model can be different depending on if it's used for **input or output**:

That extra info will be added as-is to the output **JSON Schema** for that model, and it will be used in the API docs.

=== "Pydantic v2"

    In Pydantic version 2, you would use the attribute `model_config`, that takes a `dict` as described in <a href="https://docs.pydantic.dev/latest/usage/model_config/" class="external-link" target="_blank">Pydantic's docs: Model Config</a>.

Aqui estão várias formas de se fazer isso.

## `schema_extra` do Pydantic

Você pode declarar um `example` para um modelo Pydantic usando `Config` e `schema_extra`, conforme descrito em <a href="https://docs.pydantic.dev/latest/concepts/json_schema/#schema-customization" class="external-link" target="_blank">Documentação do Pydantic: Schema customization</a>:

```Python hl_lines="15-23"

### Concurrencia y Hamburguesas

El concepto de código **asíncrono** descrito anteriormente a veces también se llama **"concurrencia"**. Es diferente del **"paralelismo"**.

**Concurrencia** y **paralelismo** ambos se relacionan con "cosas diferentes que suceden más o menos al mismo tiempo".

and you are already setting **replication** at the cluster level, with multiple **containers**. In those cases, you are better off **building an image from scratch** as described above: [Build a Docker Image for FastAPI](#build-a-docker-image-for-fastapi).

This image would be useful mainly in the special cases described above in [Containers with Multiple Processes and Special Cases](#containers-with-multiple-processes-and-special-cases). For example, if your application is **simple enough**...

You can also declare the `Response` parameter in dependencies, and set headers (and cookies) in them.

## Return a `Response` directly

You can also add headers when you return a `Response` directly.

Create a response as described in [Return a Response Directly](response-directly.md){.internal-link target=_blank} and pass the headers as an additional parameter:

```Python hl_lines="10-12"
{!../../../docs_src/response_headers/tutorial001.py!}
```

## Repaso

* Importa `FastAPI`.
* Crea un instance de `app`.
* Escribe un **decorador de operación de path** (como `@app.get("/")`).
* Escribe una **función de la operación de path** (como `def root(): ...` arriba).

have a model with all the attributes marked as optional (with default values or `None`).

    To distinguish from the models with all optional values for **updates** and models with required values for **creation**, you can use the ideas described in [Extra Models](extra-models.md){.internal-link target=_blank}....