"price": 50.2,
        "tax": 10.5,
        "tags": [],
    }


@needs_py39
def test_put(client: TestClient):
    response = client.put(
        "/items/bar", json={"name": "Barz", "price": 3, "description": None}
    )
    assert response.json() == {
        "name": "Barz",
        "description": None,
        "price": 3,
        "tax": 10.5,
        "tags": [],
    }


@needs_py39
@needs_pydanticv2

    ```

## Set-Typen

Aber dann denken wir darüber nach und stellen fest, dass sich die Tags nicht wiederholen sollen, es sollen eindeutige Strings sein.

Python hat einen Datentyp speziell für Mengen eindeutiger Dinge: das <abbr title="Menge">`set`</abbr>.

Deklarieren wir also `tags` als Set von Strings.

=== "Python 3.10+"

    ```Python hl_lines="12"

<img src="/img/tutorial/generate-clients/image05.png">

## FastAPI App with Tags

In many cases your FastAPI app will be bigger, and you will probably use tags to separate different groups of *path operations*.

For example, you could have a section for **items** and another section for **users**, and they could be separated by tags:

=== "Python 3.9+"

    ```Python hl_lines="21  26  34"

    assert response.json() == {
        "openapi": "3.1.0",
        "info": {"title": "FastAPI", "version": "0.1.0"},
        "paths": {
            "/users/": {
                "get": {
                    "tags": ["users"],
                    "summary": "Read Users",
                    "operationId": "read_users_users__get",
                    "parameters": [
                        {

    assert response.json() == {
        "openapi": "3.1.0",
        "info": {"title": "FastAPI", "version": "0.1.0"},
        "paths": {
            "/users/": {
                "get": {
                    "tags": ["users"],
                    "summary": "Read Users",
                    "operationId": "read_users_users__get",
                    "parameters": [
                        {

```Python hl_lines="3  5-6"
{
    "name": "Baz",
    "description": None,
    "price": 50.2,
    "tax": 10.5,
    "tags": []
}
```

FastAPI is smart enough (actually, Pydantic is smart enough) to realize that, even though `description`, `tax`, and `tags` have the same values as the defaults, they were set explicitly (instead of taken from the defaults).

So, they will be included in the JSON response.

### Add some custom `tags`, `responses`, and `dependencies`

We are not adding the prefix `/items` nor the `tags=["items"]` to each *path operation* because we added them to the `APIRouter`.

But we can still add _more_ `tags` that will be applied to a specific *path operation*, and also some extra `responses` specific to that *path operation*:

这将引用 `app/` 的往上一级，带有其自己的 `__init __.py` 等文件的某个包。但是我们并没有这个包。因此，这将在我们的示例中引发错误。🚨

但是现在你知道了它的工作原理，因此无论它们多么复杂，你都可以在自己的应用程序中使用相对导入。🤓

### 添加一些自定义的 `tags`、`responses` 和 `dependencies`

我们不打算在每个*路径操作*中添加前缀 `/items` 或 `tags =["items"]`，因为我们将它们添加到了 `APIRouter` 中。

但是我们仍然可以添加*更多*将会应用于特定的*路径操作*的 `tags`，以及一些特定于该*路径操作*的额外 `responses`：

```Python hl_lines="30-31" title="app/routers/items.py"

    ```

=== "Python 3.8+"

    ```Python hl_lines="14"
    {!> ../../../docs_src/body_nested_models/tutorial001.py!}
    ```

Это приведёт к тому, что обьект `tags` преобразуется в список, несмотря на то что тип его элементов не объявлен.

## Определение полей содержащих список с определением типов его элементов

```Python hl_lines="3  5-6"
{
    "name": "Baz",
    "description": None,
    "price": 50.2,
    "tax": 10.5,
    "tags": []
}
```

dann ist FastAPI klug genug (tatsächlich ist Pydantic klug genug) zu erkennen, dass, obwohl `description`, `tax`, und `tags` die gleichen Werte haben wie ihre Defaultwerte, sie explizit gesetzt wurden (statt dass sie von den Defaultwerten genommen wurden).