If you can use the **latest versions of Python**, use the examples for the latest version, those will have the **best and simplest syntax**, for example, "**Python 3.10+**".

#### List

For example, let's define a variable to be a `list` of `str`.

=== "Python 3.9+"

    Declare the variable, with the same colon (`:`) syntax.

    As the type, put `list`.

# Paramètres de chemin

Vous pouvez déclarer des "paramètres" ou "variables" de chemin avec la même syntaxe que celle utilisée par le
<a href="https://docs.python.org/fr/3/library/string.html#format-string-syntax" class="external-link" target="_blank">formatage de chaîne Python</a> :


```Python hl_lines="6-7"
{!../../../docs_src/path_params/tutorial001.py!}
```

La valeur du paramètre `item_id` sera transmise à la fonction dans l'argument `item_id`.

And it generates OpenAPI schemas.

That's how it works in Flask, Starlette, Responder, etc.

But then, we have again the problem of having a micro-syntax, inside of a Python string (a big YAML).

The editor can't help much with that. And if we modify parameters or Marshmallow schemas and forget to also modify that YAML docstring, the generated schema would be obsolete.

* the path `/`
* using a <abbr title="an HTTP GET method"><code>get</code> operation</abbr>

!!! info "`@decorator` Info"
    That `@something` syntax in Python is called a "decorator".

    You put it on top of a function. Like a pretty decorative hat (I guess that's where the term came from).

    A "decorator" takes the function below and does something with it.

FastAPI converts the configurations to **JSON** to make them compatible with JavaScript, as that's what Swagger UI needs.

## Disable Syntax Highlighting

For example, you could disable syntax highlighting in Swagger UI.

Without changing the settings, syntax highlighting is enabled by default:

<img src="/img/tutorial/extending-openapi/image02.png">

But you can disable it by setting `syntaxHighlight` to `False`:

    ```

=== "Python 3.8+"

    ```Python hl_lines="31  37"
    {!> ../../../docs_src/response_model/tutorial005.py!}
    ```

!!! tip
    The syntax `{"name", "description"}` creates a `set` with those two values.

    It is equivalent to `set(["name", "description"])`.

#### Using `list`s instead of `set`s

![ReDoc](https://fastapi.tiangolo.com/img/index/index-06-redoc-02.png)

### Just Modern Python

It's all based on standard **Python type** declarations (thanks to Pydantic). No new syntax to learn. Just standard modern Python.

If you need a 2 minute refresher of how to use Python types (even if you don't use FastAPI), check the short tutorial: [Python Types](python-types.md){.internal-link target=_blank}.

![ReDoc](https://fastapi.tiangolo.com/img/index/index-06-redoc-02.png)

### Sadece modern Python

Tamamiyle standartlar **Python 3.8**'nın type hintlerine dayanıyor (Pydantic'in sayesinde). Yeni bir syntax öğrenmene gerek yok. Sadece modern Python.

# Concurrency and async / await

Details about the `async def` syntax for *path operation functions* and some background about asynchronous code, concurrency, and parallelism.

## In a hurry?

<abbr title="too long; didn't read"><strong>TL;DR:</strong></abbr>

If you are using third party libraries that tell you to call them with `await`, like:

```Python
results = await some_library()
```

* ✏ Fix typo in `docs/en/docs/python-types.md`. PR [#4886](https://github.com/tiangolo/fastapi/pull/4886) by [@MicaelJarniac](https://github.com/MicaelJarniac).
* 🎨 Fix syntax highlighting in docs for OpenAPI Callbacks. PR [#4368](https://github.com/tiangolo/fastapi/pull/4368) by [@xncbf](https://github.com/xncbf).