* `tax: float = 10.5` has a default of `10.5`.
* `tags: List[str] = []` has a default of an empty list: `[]`.

but you might want to omit them from the result if they were not actually stored.

For example, if you have models with many optional attributes in a NoSQL database, but you don't want to send very long JSON responses full of default values.

They are, more or less, at opposite ends, complementing each other.

Requests has a very simple and intuitive design, it's very easy to use, with sensible defaults. But at the same time, it's very powerful and customizable.

That's why, as said in the official website:

> Requests is one of the most downloaded Python packages of all time

            exclude_none=exclude_none,
            exclude_defaults=exclude_defaults,
        )
        if "__root__" in obj_dict:
            obj_dict = obj_dict["__root__"]
        return jsonable_encoder(
            obj_dict,
            exclude_none=exclude_none,
            exclude_defaults=exclude_defaults,
            # TODO: remove when deprecating Pydantic v1
            custom_encoder=encoders,

!!! info
    Sie können auch:

    * `response_model_exclude_defaults=True`
    * `response_model_exclude_none=True`

    verwenden, wie in der <a href="https://docs.pydantic.dev/1.10/usage/exporting_models/#modeldict" class="external-link" target="_blank">Pydantic Dokumentation</a> für `exclude_defaults` und `exclude_none` beschrieben.

#### Daten mit Werten für Felder mit Defaultwerten

!!! info
    👆 💪 ⚙️:

    * `response_model_exclude_defaults=True`
    * `response_model_exclude_none=True`

    🔬 <a href="https://docs.pydantic.dev/latest/concepts/serialization/#modeldict" class="external-link" target="_blank">Pydantic 🩺</a> `exclude_defaults` &amp; `exclude_none`.

#### 📊 ⏮️ 💲 🏑 ⏮️ 🔢

✋️ 🚥 👆 📊 ✔️ 💲 🏷 🏑 ⏮️ 🔢 💲, 💖 🏬 ⏮️ 🆔 `bar`:

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

Peewee has some heavy assumptions about its defaults and about how it should be used.

If you are developing an application with an older non-async framework, and can work with all its defaults, **it can be a great tool**.

<img src="/img/tutorial/query-params-str-validations/image02.png">

### Query-Parameter-Liste / Mehrere Werte mit Defaults

Und Sie können auch eine Default-`list`e von Werten definieren, wenn keine übergeben werden:

=== "Python 3.9+"

    ```Python hl_lines="9"
    {!> ../../../docs_src/query_params_str_validations/tutorial012_an_py39.py!}

    tags: List[str] = []
    if PYDANTIC_V2:
        model_config = {"json_schema_serialization_defaults_required": True}


class Item(BaseModel):
    name: str
    description: Optional[str] = None
    sub: Optional[SubItem] = None
    if PYDANTIC_V2:
        model_config = {"json_schema_serialization_defaults_required": True}


def get_app_client(separate_input_output_schemas: bool = True) -> TestClient:

        json_schema_extra: Union[Dict[str, Any], None] = None,
        **extra: Any,
    ):
        assert default is ..., "Path parameters cannot have a default value"
        self.in_ = self.in_
        super().__init__(
            default=default,
            default_factory=default_factory,
            annotation=annotation,
            alias=alias,
            alias_priority=alias_priority,

                }
            ]
        }
    )


def test_query_int_default():
    response = client.get("/query/int/default")
    assert response.status_code == 200
    assert response.json() == "foo bar 10"


def test_query_int_default_query_50():
    response = client.get("/query/int/default?query=50")
    assert response.status_code == 200
    assert response.json() == "foo bar 50"