!!! info
    You can also use:

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

    as described in <a href="https://docs.pydantic.dev/latest/concepts/serialization/#modeldict" class="external-link" target="_blank">the Pydantic docs</a> for `exclude_defaults` and `exclude_none`.

!!! info
    你还可以使用：

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

    参考 <a href="https://docs.pydantic.dev/latest/concepts/serialization/#modeldict" class="external-link" target="_blank">Pydantic 文档</a> 中对 `exclude_defaults` 和 `exclude_none` 的描述。

#### 默认值字段有实际值的数据

!!! info "情報"
    以下も使用することができます:

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

    `PATCH` 没有 `PUT` 知名，也怎么不常用。

    很多人甚至只用 `PUT` 实现部分更新。

    **FastAPI** 对此没有任何限制，可以**随意**互换使用这两种操作。

    但本指南也会分别介绍这两种操作各自的用途。

### 使用 Pydantic 的 `exclude_unset` 参数

更新部分数据时，可以在 Pydantic 模型的 `.dict()` 中使用 `exclude_unset` 参数。

比如，`item.dict(exclude_unset=True)`。

这段代码生成的 `dict` 只包含创建 `item` 模型时显式设置的数据，而不包括默认值。

然后再用它生成一个只含已设置（在请求中所发送）数据，且省略了默认值的 `dict`：

```Python hl_lines="34"

{!../../../docs_src/dataclasses/tutorial003.py!}
```

1. We still import `field` from standard `dataclasses`.

2. `pydantic.dataclasses` is a drop-in replacement for `dataclasses`.

3. The `Author` dataclass includes a list of `Item` dataclasses.

4. The `Author` dataclass is used as the `response_model` parameter.

5. You can use other standard type annotations with dataclasses as the request body.

This schema definition includes your API paths, the possible parameters they take, etc.

#### Data "schema"

The term "schema" might also refer to the shape of some data, like a JSON content.

In that case, it would mean the JSON attributes, and data types they have, etc.

#### OpenAPI and JSON Schema

!!! 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.

!!! 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`.

#### 📊 ⏮️ 💲 🏑 ⏮️ 🔢

    # Extra Pydantic data types
    "pydantic-extra-types >=2.0.0",
]

[tool.pdm]
version = { source = "file", path = "fastapi/__init__.py" }
distribution = true

[tool.pdm.build]
source-includes = [
    "tests/",
    "docs_src/",
    "requirements*.txt",
    "scripts/",
    # For a test
    "docs/en/docs/img/favicon.png",
    ]

        * Change *path operation decorators* parameter default for `response_model_exclude` from `set()` to `None` (as is in Pydantic).
    * In `encoders.jsonable_encoder`:
        * Remove deprecated `skip_defaults`, use instead `exclude_unset`.
        * Set default of `exclude` from `set()` to `None` (as is in Pydantic).