Pendant que vous êtes assis à table, en attendant que les burgers 🍔 soient prêts, vous pouvez passer ce temps à admirer à quel point votre crush 😍 est géniale, mignonne et intelligente ✨😍✨.

You can limit the lines used from the docstring of a *path operation function* for OpenAPI.

Adding an `\f` (an escaped "form feed" character) causes **FastAPI** to truncate the output used for OpenAPI at this point.

It won't show up in the documentation, but other tools (such as Sphinx) will be able to use the rest.

```Python hl_lines="19-29"
{!../../../docs_src/path_operation_advanced_configuration/tutorial004.py!}
```

* **Asynchronous Code**
* **`async` and `await`**
* **Coroutines**

## Asynchronous Code

Asynchronous code just means that the language 💬 has a way to tell the computer / program 🤖 that at some point in the code, it 🤖 will have to wait for *something else* to finish somewhere else. Let's say that *something else* is called "slow-file" 📝.

```Python hl_lines="2"
{!../../../docs_src/python_types/tutorial001.py!}
```

### Limitations

C'est un programme très simple.

Mais maintenant imaginez que vous l'écriviez de zéro.

À un certain point vous auriez commencé la définition de la fonction, vous aviez les paramètres prêts.

Mais vous aviez besoin de "cette méthode qui convertit la première lettre en majuscule".

* ✏️ Fix typo in `fastapi/security/oauth2.py`. PR [#11368](https://github.com/tiangolo/fastapi/pull/11368) by [@shandongbinzhou](https://github.com/shandongbinzhou).
* 📝 Update links to Pydantic docs to point to new website. PR [#11328](https://github.com/tiangolo/fastapi/pull/11328) by [@alejsdev](https://github.com/alejsdev).

If you are helping a lot of people with their questions, you will become an official [FastAPI Expert](fastapi-people.md#fastapi-experts){.internal-link target=_blank}. 🎉

Just remember, the most important point is: try to be kind. People come with their frustrations and in many cases don't ask in the best way, but try as best as you can to be kind. 🤗

Let's check back those deployment concepts from before:

* Security - HTTPS
* Running on startup
* Restarts
* **Replication (the number of processes running)**
* Memory
* Previous steps before starting

Up to this point, with all the tutorials in the docs, you have probably been running a **server program** like Uvicorn, running a **single process**.

    !!! tip
        Prefer to use the `Annotated` version if possible.

    ```Python hl_lines="3  77-79"
    {!> ../../../docs_src/security/tutorial003.py!}
    ```

### Check the password

At this point we have the user data from our database, but we haven't checked the password.

Let's put that data in the Pydantic `UserInDB` model first.

## A dependency with `yield` and `try`

If you use a `try` block in a dependency with `yield`, you'll receive any exception that was thrown when using the dependency.

For example, if some code at some point in the middle, in another dependency or in a *path operation*, made a database transaction "rollback" or create any other error, you will receive the exception in your dependency.

    {!> ../../../docs_src/python_types/tutorial009b.py!}
    ```

#### Sử dụng `Union` hay `Optional`

If you are using a Python version below 3.10, here's a tip from my very **subjective** point of view:

Nếu bạn đang sử dụng phiên bản Python dưới 3.10, đây là một mẹo từ ý kiến rất "chủ quan" của tôi:

* 🚨 Tránh sử dụng `Optional[SomeType]`
* Thay vào đó ✨ **sử dụng `Union[SomeType, None]`** ✨.