///

## Cookies with a Pydantic Model { #cookies-with-a-pydantic-model }

Declare the **cookie** parameters that you need in a **Pydantic model**, and then declare the parameter as `Cookie`:

{* ../../docs_src/cookie_param_models/tutorial001_an_py310.py hl[9:12,16] *}

**FastAPI** will **extract** the data for **each field** from the **cookies** received in the request and give you the Pydantic model you defined.

## Pydantic `Settings` { #pydantic-settings }

幸好，Pydantic 提供了很好的工具，可用來處理由環境變數而來的設定：[Pydantic：設定管理](https://docs.pydantic.dev/latest/concepts/pydantic_settings/)。

### 安裝 `pydantic-settings` { #install-pydantic-settings }

首先，請先建立你的[虛擬環境](../virtual-environments.md)，啟用它，然後安裝 `pydantic-settings` 套件：

<div class="termy">

```console
$ pip install pydantic-settings
---> 100%
```

</div>

    TypeGuard,
    TypeVar,
    Union,
    get_args,
    get_origin,
)

from fastapi.types import UnionType
from pydantic import BaseModel
from pydantic.version import VERSION as PYDANTIC_VERSION
from starlette.datastructures import UploadFile

_T = TypeVar("_T")

# Copy from Pydantic: pydantic/_internal/_typing_extra.py
WithArgsTypes: tuple[Any, ...] = (
    typing._GenericAlias,  # type: ignore[attr-defined]

# Header 参数模型 { #header-parameter-models }

如果您有一组相关的 **header 参数**，您可以创建一个 **Pydantic 模型**来声明它们。

这将允许您在**多个地方**能够**重用模型**，并且可以一次性声明所有参数的验证和元数据。😎

/// note | 注意

自 FastAPI 版本 `0.115.0` 起支持此功能。🤓

///

## 使用 Pydantic 模型的 Header 参数 { #header-parameters-with-a-pydantic-model }

在 **Pydantic 模型**中声明所需的 **header 参数**，然后将参数声明为 `Header` :

{* ../../docs_src/header_param_models/tutorial001_an_py310.py hl[9:14,18] *}

* 100% test coverage.
* 100% type annotated codebase.

## Pydantic 기능 { #pydantic-features }

**FastAPI**는 [**Pydantic**](https://docs.pydantic.dev/)과 완벽하게 호환되며(또한 이를 기반으로 합니다). 따라서 추가로 가지고 있는 Pydantic 코드도 모두 동작합니다.

데이터베이스를 위한 <abbr title="Object-Relational Mapper - 객체-관계 매퍼">ORM</abbr>, <abbr title="Object-Document Mapper - 객체-문서 매퍼">ODM</abbr>과 같은, Pydantic을 기반으로 하는 외부 라이브러리도 포함합니다.

This would allow you to **re-use the model** in **multiple places** and also to declare validations and metadata for all the parameters at once. 😎

/// note

This is supported since FastAPI version `0.115.0`. 🤓

///

## Header Parameters with a Pydantic Model { #header-parameters-with-a-pydantic-model }

from fastapi.types import IncEx, ModelNameMap, UnionType
from pydantic import BaseModel, ConfigDict, Field, TypeAdapter, create_model
from pydantic import PydanticSchemaGenerationError as PydanticSchemaGenerationError
from pydantic import PydanticUndefinedAnnotation as PydanticUndefinedAnnotation
from pydantic import ValidationError as ValidationError

这意味着，在 Python 中从环境变量读取的任何值都是 `str` 类型，任何到不同类型的转换或任何验证都必须在代码中完成。

## Pydantic 的 `Settings` { #pydantic-settings }

幸运的是，Pydantic 提供了一个很好的工具来处理来自环境变量的这些设置：[Pydantic：Settings 管理](https://docs.pydantic.dev/latest/concepts/pydantic_settings/)。

### 安装 `pydantic-settings` { #install-pydantic-settings }

首先，确保你创建并激活了[虚拟环境](../virtual-environments.md)，然后安装 `pydantic-settings` 包：

<div class="termy">

```console

你可以在 FastAPI 中使用 **Pydantic 模型**声明**表单字段**。

/// info | 信息

要使用表单，首先安装 [`python-multipart`](https://github.com/Kludex/python-multipart)。

确保你创建一个[虚拟环境](../virtual-environments.md)，激活它，然后再安装，例如：

```console
$ pip install python-multipart
```

///

/// note | 注意

自 FastAPI 版本 `0.113.0` 起支持此功能。🤓

///

## 表单的 Pydantic 模型 { #pydantic-models-for-forms }

        ```
    validations:
      required: true
  - type: input
    id: pydantic-version
    attributes:
      label: Pydantic Version
      description: |
        What Pydantic version are you using?

        You can find the Pydantic version with:

        ```bash
        python -c "import pydantic; print(pydantic.version.VERSION)"
        ```
    validations:
      required: true
  - type: input