## `Header` importieren { #import-header }

Importieren Sie zuerst `Header`:

{* ../../docs_src/header_params/tutorial001_an_py310.py hl[3] *}

## `Header`-Parameter deklarieren { #declare-header-parameters }

Deklarieren Sie dann die Header-Parameter mit derselben Struktur wie bei `Path`, `Query` und `Cookie`.

Sie können den Defaultwert sowie alle zusätzlichen Validierungs- oder Annotationsparameter definieren:

定义 `Header` 参数的方式与定义 `Query`、`Path`、`Cookie` 参数相同。

## 导入 `Header` { #import-header }

首先，导入 `Header`：

{* ../../docs_src/header_params/tutorial001_an_py310.py hl[3] *}

## 声明 `Header` 参数 { #declare-header-parameters }

然后，使用和 `Path`、`Query`、`Cookie` 一样的结构定义 header 参数。

第一个值是默认值，还可以传递所有验证参数或注释参数：

{* ../../docs_src/header_params/tutorial001_an_py310.py hl[9] *}

/// note | 技术细节

   *
   * @param throwable the Throwable to possibly propagate
   * @param declaredType1 any checked exception type declared by the calling method
   * @param declaredType2 any other checked exception type declared by the calling method
   * @deprecated Use a combination of two calls to {@link #throwIfInstanceOf} and one call to {@link

     * converter.apply(), anyway. If clients use only converter.convert(), then their nullness
     * checkers are unlikely to ever look at the annotations on this declaration.
     *
     * Historical note: At one point, we'd declared this method as accepting and returning nullable
     * values. For details on that, see earlier revisions of this file.
     */
    return convert(a);
  }

  /**

 *   used by [GenerateLicenseFile] to normalise inconsistent spellings across the Maven ecosystem
 *
 * ## Adding a new dependency with an unrecognised license
 *
 * If `./gradlew generateLicenseFile` fails with "declare a license name not registered in
 * License.kt", add the raw POM name string to the [aliases] list of the matching entry, or
 * create a new entry if the license is genuinely new.
 *

                }

                currentFilePath?.let { filePath ->
                    when {
                        line.contains("These transitive dependencies should be declared directly:") -> {
                            dependencyFixes.addToMap(filePath, extractDependencies(index))
                        }

Обратите внимание, что функция `Field` импортируется непосредственно из `pydantic`, а не из `fastapi`, как все остальные функции (`Query`, `Path`, `Body` и т.д.).

///

## Объявление атрибутов модели { #declare-model-attributes }

Вы можете использовать функцию `Field` с атрибутами модели:

{* ../../docs_src/body_fields/tutorial001_an_py310.py hl[11:14] *}

 *       typically because the type forbids nullable type arguments: For example, {@code
 *       ImmutableList.get} returns {@code E}, but that value is never {@code null}. (Accordingly,
 *       {@code ImmutableList} is declared to forbid {@code ImmutableList<@Nullable String>}.)
 *   <li>methods whose return type is a type variable but which can return {@code null} regardless
 *       of the type argument supplied by the user of the class: For example, {@code

 *       typically because the type forbids nullable type arguments: For example, {@code
 *       ImmutableList.get} returns {@code E}, but that value is never {@code null}. (Accordingly,
 *       {@code ImmutableList} is declared to forbid {@code ImmutableList<@Nullable String>}.)
 *   <li>methods whose return type is a type variable but which can return {@code null} regardless
 *       of the type argument supplied by the user of the class: For example, {@code

 *       typically because the type forbids nullable type arguments: For example, {@code
 *       ImmutableList.get} returns {@code E}, but that value is never {@code null}. (Accordingly,
 *       {@code ImmutableList} is declared to forbid {@code ImmutableList<@Nullable String>}.)
 *   <li>methods whose return type is a type variable but which can return {@code null} regardless
 *       of the type argument supplied by the user of the class: For example, {@code