### Anote sua versão `fastapi`

A primeira coisa que você deve fazer é "fixar" a versão do **FastAPI** que está utilizando para a última versão específica que você sabe que funciona corretamente para a sua aplicação.

Por exemplo, vamos dizer que você esteja utilizando a versão `0.45.0` no seu _app_.

Se você usa um arquivo `requirements.txt`, dá para especificar a versão assim:

```txt

#### 🗒

❌:

```Python
connect_args={"check_same_thread": False}
```

...💪 🕴 `SQLite`. ⚫️ 🚫 💪 🎏 💽.

!!! info "📡 ℹ"

    🔢 🗄 🔜 🕴 ✔ 1️⃣ 🧵 🔗 ⏮️ ⚫️, 🤔 👈 🔠 🧵 🔜 🍵 🔬 📨.

    👉 ❎ 😫 🤝 🎏 🔗 🎏 👜 (🎏 📨).

    ✋️ FastAPI, ⚙️ 😐 🔢 (`def`) 🌅 🌘 1️⃣ 🧵 💪 🔗 ⏮️ 💽 🎏 📨, 👥 💪 ⚒ 🗄 💭 👈 ⚫️ 🔜 ✔ 👈 ⏮️ `connect_args={"check_same_thread": False}`.

Donc pour équilibrer tout ça, imaginez l'histoire suivante :

> Vous devez nettoyer une grande et sale maison.

*Oui, c'est toute l'histoire*.

---

Il n'y a plus d'attente 🕙 nulle part, juste beaucoup de travail à effectuer, dans différentes pièces de la maison.

query_extractor --> query_or_cookie_extractor --> read_query
```

## Using the same dependency multiple times

If one of your dependencies is declared multiple times for the same *path operation*, for example, multiple dependencies have a common sub-dependency, **FastAPI** will know to call that sub-dependency only once per request.

This will be especially useful when you use it in a **large code base** where you use **the same dependencies** over and over again in **many *path operations***.

## To `async` or not to `async`

As dependencies will also be called by **FastAPI** (the same as your *path operation functions*), the same rules apply while defining your functions.

http://127.0.0.1:8000/items/
```

would be the same as going to:

```
http://127.0.0.1:8000/items/?skip=0&limit=10
```

But if you go to, for example:

```
http://127.0.0.1:8000/items/?skip=20
```

The parameter values in your function will be:

* `skip=20`: because you set it in the URL
* `limit=10`: because that was the default value

## Optional parameters

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

    ```Python hl_lines="17"
    {!> ../../../docs_src/dependencies/tutorial006.py!}
    ```

These dependencies will be executed/solved the same way as normal dependencies. But their value (if they return any) won't be passed to your *path operation function*.

!!! tip
    Some editors check for unused function parameters, and show them as errors.

{!../../../docs_src/response_status_code/tutorial002.py!}
```

They are just a convenience, they hold the same number, but that way you can use the editor's autocomplete to find them:

<img src="/img/tutorial/response-status-code/image02.png">

!!! note "Technical Details"
    You could also use `from starlette import status`.

```Python hl_lines="9-13  36-53"
{!../../../docs_src/openapi_webhooks/tutorial001.py!}
```

The webhooks that you define will end up in the **OpenAPI** schema and the automatic **docs UI**.

!!! info

The process that happens when your API app calls the *external API* is named a "callback". Because the software that the external developer wrote sends a request to your API and then your API *calls back*, sending a request to an *external API* (that was probably created by the same developer).