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/body_updates/tutorial002.py!}
```

### 使用 Pydantic 的 `update` 参数

接下来，用 `.copy()` 为已有模型创建调用 `update` 参数的副本，该参数为包含更新数据的 `dict`。

例如，`stored_item_model.copy(update=update_data)`：

R8 / ProGuard
-------------

R8 and ProGuard are both code optimizers for `.class` files.

R8 is the [default optimizer][r8] in Android Studio 3.4 and newer. It works well with all
releases of OkHttp.

ProGuard was the previous default. We’re [tracking problems][proguard_problems] with interactions

```

////

//// tab | Python 3.9+

```Python hl_lines="1  3"
{!> ../../docs_src/path_params_numeric_validations/tutorial001_an_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="3-4"
{!> ../../docs_src/path_params_numeric_validations/tutorial001_an.py!}
```

////

//// tab | Python 3.10+ non-Annotated

/// tip

Prefer to use the `Annotated` version if possible.

///

		<-cdone
	}
}

// Borrowed from rwmutex_test.go
func TestParallelReaders(t *testing.T) {
	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(-1))
	doTestParallelReaders(1, 4)
	doTestParallelReaders(3, 4)
	doTestParallelReaders(4, 2)
}

// Borrowed from rwmutex_test.go
func reader(resource string, numIterations int, activity *int32, cdone chan bool) {
	rwm := NewDRWMutex(ds, resource)

     This License is not intended to limit any rights You have under applicable
     copyright doctrines of fair use, fair dealing, or other equivalents.

2.7. Conditions

     Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the licenses granted in
     Section 2.1.


3. Responsibilities

3.1. Distribution of Source Form

     All distribution of Covered Software in Source Code Form, including any

  static final String E21 = "2-1";
  static final String E13 = "1-3";
  static final String E14 = "1-4";
  static final String E23 = "2-3";
  static final String E31 = "3-1";
  static final String E34 = "3-4";
  static final String E41 = "4-1";
  static final String E15 = "1-5";
  static final String EDGE_NOT_IN_GRAPH = "edgeNotInGraph";

  // TODO(user): Consider separating Strings that we've defined here to capture

    assertThat(map.keys()).containsExactly("bar", "foo", "bar", "bar").inOrder();
    map.keys().remove("bar"); // bar is no longer the first key!
    assertEquals("{foo=[2], bar=[3, 4]}", map.toString());
  }

  public void testLinkedValues() {
    Multimap<String, Integer> map = create();
    map.put("bar", 1);
    map.put("foo", 2);
    map.put("bar", 3);
    map.put("bar", 4);

```

/// info | "Дополнительная информация"

<a href="https://docs.python.org/3/library/enum.html" class="external-link" target="_blank">Перечисления (enum) доступны в Python</a> начиная с версии 3.4.

///

/// tip | "Подсказка"

Если интересно, то "AlexNet", "ResNet" и "LeNet" - это названия <abbr title="Технически, это архитектуры моделей глубокого обучения">моделей</abbr> машинного обучения.

///

{!../../docs_src/path_params/tutorial005.py!}
```

/// info

<a href="https://docs.python.org/3/library/enum.html" class="external-link" target="_blank">Enumerationen (oder kurz Enums)</a> gibt es in Python seit Version 3.4.

///

/// tip | "Tipp"

Falls Sie sich fragen, was „AlexNet“, „ResNet“ und „LeNet“ ist, das sind Namen von <abbr title="Genau genommen, Deep-Learning-Modellarchitekturen">Modellen</abbr> für maschinelles Lernen.

     This License is not intended to limit any rights You have under applicable
     copyright doctrines of fair use, fair dealing, or other equivalents.

2.7. Conditions

     Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the licenses granted in
     Section 2.1.


3. Responsibilities

3.1. Distribution of Source Form

     All distribution of Covered Software in Source Code Form, including any