!!! tip
    Pydantic ✔️ 🎁 🎭 🕐❔ 👆 ⚙️ `Optional` ⚖️ `Union[Something, None]` 🍵 🔢 💲, 👆 💪 ✍ 🌅 🔃 ⚫️ Pydantic 🩺 🔃 <a href="https://docs.pydantic.dev/latest/concepts/models/#required-optional-fields" class="external-link" target="_blank">✔ 📦 🏑</a>.

## 🆎 🔑 **FastAPI**

**FastAPI** ✊ 📈 👫 🆎 🔑 📚 👜.

⏮️ **FastAPI** 👆 📣 🔢 ⏮️ 🆎 🔑 &amp; 👆 🤚:

* **👨‍🎨 🐕‍🦺**.

If you already have a code base that uses <a href="https://docs.peewee-orm.com/en/latest/" class="external-link" target="_blank">Peewee ORM</a>, you can check here how to use it with **FastAPI**.

!!! warning "Python 3.7+ required"
    You will need Python 3.7 or above to safely use Peewee with FastAPI.

## Peewee for async

Peewee was not designed for async frameworks, or with them in mind.

* `instagram_basic` is used by Facebook / Instagram.
* `https://www.googleapis.com/auth/drive` is used by Google.

!!! info
    In OAuth2 a "scope" is just a string that declares a specific permission required.

    It doesn't matter if it has other characters like `:` or if it is a URL.

    Those details are implementation specific.

    For OAuth2 they are just strings.

## Code to get the `username` and `password`

    ```

!!! info
    Notice that `response_description` refers specifically to the response, the `description` refers to the *path operation* in general.

!!! check
    OpenAPI specifies that each *path operation* requires a response description.

    So, if you don't provide one, **FastAPI** will automatically generate one of "Successful response".

<img src="/img/tutorial/path-operation-configuration/image03.png">

* Even dependencies can have dependencies, creating a hierarchy or **"graph" of dependencies**.
* All **automatically handled** by the framework.
* All the dependencies can require data from requests and **augment the path operation** constraints and automatic documentation.
* **Automatic validation** even for *path operation* parameters defined in dependencies.

## What is "Dependency Injection"

**"Dependency Injection"** means, in programming, that there is a way for your code (in this case, your *path operation functions*) to declare things that it requires to work and use: "dependencies".

And then, that system (in this case **FastAPI**) will take care of doing whatever is needed to provide your code with those needed dependencies ("inject" the dependencies).

* Si le paramètre est déclaré comme ayant pour type un **modèle Pydantic**, il sera interprété comme faisant partie du **corps** de la requête.

!!! note
    **FastAPI** saura que la valeur de `q` n'est pas requise grâce à la valeur par défaut `=None`.

---

Common examples of CPU bound operations are things that require complex math processing.

For example:

* **Audio** or **image processing**.
* **Computer vision**: an image is composed of millions of pixels, each pixel has 3 values / colors, processing that normally requires computing something on those pixels, all at the same time.

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**:

* for **input** the `description` will **not be required**
* for **output** it will be **required** (and possibly `None`, or in JSON terms, `null`)

### Model for Output in Docs

=== "Python 3.8+"

    ```Python hl_lines="7-11"
    {!> ../../../docs_src/body/tutorial001.py!}
    ```

The same as when declaring query parameters, when a model attribute has a default value, it is not required. Otherwise, it is required. Use `None` to make it just optional.

For example, this model above declares a JSON "`object`" (or Python `dict`) like:

```JSON
{
    "name": "Foo",
    "description": "An optional description",