## Optional parameters

The same way, you can declare optional query parameters, by setting their default to `None`:

=== "Python 3.10+"

    ```Python hl_lines="7"
    {!> ../../../docs_src/query_params/tutorial002_py310.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="9"
    {!> ../../../docs_src/query_params/tutorial002.py!}
    ```

* `Annotated` von `typing` (oder von `typing_extensions` in Python unter 3.9)

=== "Python 3.10+"

    In Python 3.9 oder darüber, ist `Annotated` Teil der Standardbibliothek, also können Sie es von `typing` importieren.

    ```Python hl_lines="1  3"
    {!> ../../../docs_src/query_params_str_validations/tutorial002_an_py310.py!}
    ```

=== "Python 3.8+"

    In Versionen unter Python 3.9 importieren Sie `Annotated` von `typing_extensions`.

=== "Python 3.10+"

    ```Python hl_lines="12"
    {!> ../../../docs_src/body_nested_models/tutorial003_py310.py!}
    ```

=== "Python 3.9+"

    ```Python hl_lines="14"
    {!> ../../../docs_src/body_nested_models/tutorial003_py39.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="1  14"
    {!> ../../../docs_src/body_nested_models/tutorial003.py!}
    ```

```Python
q: Union[str, None] = None
```

Ou como em Python 3.10 e versões superiores:

```Python
q: str | None = None
```

Por exemplo:

=== "Python 3.10+"

    ```Python hl_lines="26"
    {!> ../../../docs_src/body_multiple_params/tutorial004_py310.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="27"

=== "Python 3.10+ Pydantic v2"

    ```Python hl_lines="13-24"
    {!> ../../../docs_src/schema_extra_example/tutorial001_py310.py!}
    ```

=== "Python 3.10+ Pydantic v1"

    ```Python hl_lines="13-23"
    {!> ../../../docs_src/schema_extra_example/tutorial001_py310_pv1.py!}
    ```

=== "Python 3.8+ Pydantic v2"

    ```Python hl_lines="15-26"

=== "Python 3.10+ Pydantic v2"

    ```Python hl_lines="13-24"
    {!> ../../../docs_src/schema_extra_example/tutorial001_py310.py!}
    ```

=== "Python 3.10+ Pydantic v1"

    ```Python hl_lines="13-23"
    {!> ../../../docs_src/schema_extra_example/tutorial001_py310_pv1.py!}
    ```

=== "Python 3.8+ Pydantic v2"

    ```Python hl_lines="15-26"

Verwenden Sie Standard-Python-Typen für die Klassenattribute:

=== "Python 3.10+"

    ```Python hl_lines="5-9"
    {!> ../../../docs_src/body/tutorial001_py310.py!}
    ```

=== "Python 3.8+"

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

=== "Python 3.10+"

    ```Python hl_lines="2"
    {!> ../../../docs_src/body/tutorial001_py310.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="4"
    {!> ../../../docs_src/body/tutorial001.py!}
    ```

## Create your data model

Then you declare your data model as a class that inherits from `BaseModel`.

Use standard Python types for all the attributes:

=== "Python 3.10+"

    ```Python hl_lines="28-33"
    {!> ../../../docs_src/body_updates/tutorial001_py310.py!}
    ```

=== "Python 3.9+"

    ```Python hl_lines="30-35"
    {!> ../../../docs_src/body_updates/tutorial001_py39.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="30-35"
    {!> ../../../docs_src/body_updates/tutorial001.py!}

## Импорт `Header`

Сперва импортируйте `Header`:

=== "Python 3.10+"

    ```Python hl_lines="3"
    {!> ../../../docs_src/header_params/tutorial001_an_py310.py!}
    ```

=== "Python 3.9+"

    ```Python hl_lines="3"
    {!> ../../../docs_src/header_params/tutorial001_an_py39.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="3"
    {!> ../../../docs_src/header_params/tutorial001_an.py!}