## `Field` additional arguments

When using `Field()` with Pydantic models, you can also declare additional `examples`:

//// tab | Python 3.10+

```Python hl_lines="2  8-11"
{!> ../../docs_src/schema_extra_example/tutorial002_py310.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="4  10-13"
{!> ../../docs_src/schema_extra_example/tutorial002.py!}
```

////

## `examples` in JSON Schema - OpenAPI

```

////

//// tab | Python 3.10+ 没Annotated

/// tip

尽可能选择使用 `Annotated` 的版本。

///

```Python hl_lines="11  13  20  23"
{!> ../../docs_src/background_tasks/tutorial002_py310.py!}
```

////

//// tab | Python 3.8+ 没Annotated

/// tip

尽可能选择使用 `Annotated` 的版本。

///

```Python hl_lines="13  15  22  25"

    "price": 42.0,
    "tax": 3.2
}
```

但是你也可以声明多个请求体参数，例如 `item` 和 `user`：

//// tab | Python 3.10+

```Python hl_lines="20"
{!> ../../docs_src/body_multiple_params/tutorial002_py310.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="22"
{!> ../../docs_src/body_multiple_params/tutorial002.py!}
```

////

在这种情况下，**FastAPI** 将注意到该函数中有多个请求体参数（两个 Pydantic 模型参数）。

Let's say you have a Pydantic model with default values, like this one:

{* ../../docs_src/separate_openapi_schemas/tutorial001_py310.py ln[1:7] hl[7] *}

### Model for Input

If you use this model as an input like here:

{* ../../docs_src/separate_openapi_schemas/tutorial001_py310.py ln[1:15] hl[14] *}

...then the `description` field will **not be required**. Because it has a default value of `None`.

//// tab | Python 3.10+

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

////

//// tab | Python 3.8+

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

////

```

////

//// tab | Python 3.10+ 非带注解版本

/// tip

如果可能，请尽量使用 `Annotated` 版本。

///

```Python hl_lines="66-67  79"
{!> ../../docs_src/websockets/tutorial002_py310.py!}
```

////

//// tab | Python 3.8+ 非带注解版本

/// tip

如果可能，请尽量使用 `Annotated` 版本。

///

```Python hl_lines="68-69  81"
{!> ../../docs_src/websockets/tutorial002.py!}

////

//// tab | Python 3.10+ nicht annotiert

/// tip | "Tipp"

Bevorzugen Sie die `Annotated`-Version, falls möglich.

///

```Python hl_lines="11  13  20  23"
{!> ../../docs_src/background_tasks/tutorial002_py310.py!}
```

////

//// tab | Python 3.8+ nicht annotiert

/// tip | "Tipp"

Bevorzugen Sie die `Annotated`-Version, falls möglich.

///

```Python hl_lines="13  15  22  25"

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

////

//// tab | Python 3.8+

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

////

## 创建数据模型

把数据模型声明为继承 `BaseModel` 的类。

使用 Python 标准类型声明所有属性：

//// tab | Python 3.10+

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

////

//// tab | Python 3.8+

///

## Das Modell verwenden

Innerhalb der Funktion können Sie alle Attribute des Modells direkt verwenden:

//// tab | Python 3.10+

```Python hl_lines="19"
{!> ../../docs_src/body/tutorial002_py310.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="21"
{!> ../../docs_src/body/tutorial002.py!}
```

////

## Requestbody- + Pfad-Parameter

//// tab | Python 3.10+

```Python hl_lines="7  13-14  17-18  21-22"
{!> ../../docs_src/extra_models/tutorial002_py310.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="9  15-16  19-20  23-24"
{!> ../../docs_src/extra_models/tutorial002.py!}
```

////

## `Union` или `anyOf`