Der erste Wert ist der Typ. Sie können `Header` die gehabten Extra Validierungs- und Beschreibungsparameter hinzufügen. Danach können Sie einen Defaultwert vergeben:

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

/// note | Technische Details

///

## Declarar atributos del modelo

Después puedes utilizar `Field` con los atributos del modelo:

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

`Field` funciona de la misma manera que `Query`, `Path` y `Body`, tiene todos los mismos parámetros, etc.

/// note | Detalles técnicos

     * @param path The FTP path to check.
     * @return true if it matches, false otherwise.
     */
    boolean matches(final String path) {
        if (StringUtil.isBlank(path)) {
            return false;
        }

        try {
            final int pos = path.indexOf('/', 6);
            final URI uri = new URI(pos == -1 ? path : path.substring(0, pos));

        wagon.addExpectedContent("path", "lower-case-checksum");
        wagon.addExpectedContent("path.sha1", "2a25dc564a3b34f68237fc849066cbc7bb7a36a1");
        wagonManager.getArtifact(artifact, repo, null, false);

        wagon.clearExpectedContent();
        wagon.addExpectedContent("path", "upper-case-checksum");
        wagon.addExpectedContent("path.sha1", "B7BB97D7D0B9244398D9B47296907F73313663E6");

These are the special functions that you can put in *path operation function* parameters or dependency functions with `Annotated` to get data from the request.

It includes:

* `Query()`
* `Path()`
* `Body()`
* `Cookie()`
* `Header()`
* `Form()`
* `File()`

You can import them all directly from `fastapi`:

```python
from fastapi import Body, Cookie, File, Form, Header, Path, Query
```

::: fastapi.Query

這意味著從環境變數中讀取的**任何值**在 Python 中都將是一個 `str`，任何型別轉換或驗證都必須在程式碼中完成。

你將在[進階使用者指南 - 設定和環境變數](./advanced/settings.md)中了解更多關於使用環境變數處理**應用程式設定**的資訊。

## `PATH` 環境變數

有一個**特殊的**環境變數稱為 **`PATH`**，作業系統（Linux、macOS、Windows）用它來查找要執行的程式。

`PATH` 變數的值是一個長字串，由 Linux 和 macOS 上的冒號 `:` 分隔的目錄組成，而在 Windows 上則是由分號 `;` 分隔的。

例如，`PATH` 環境變數可能如下所示：

//// tab | Linux, macOS

```plaintext
/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin
```

    }

    // Happy path: handleDFSReferral returns a resolved path
    @Test
    @DisplayName("handleDFSReferral returns resolved UNC path as stubbed")
    void handleDfsReferralValidInputs() {
        // Edge-like Windows UNC-style: a single backslash in the path
        String reqPath = "\\";
        String resolved = "smb://server/share/path";

Primero crea un nuevo `APIRouter` que contendrá uno o más callbacks.

{* ../../docs_src/openapi_callbacks/tutorial001.py hl[3,25] *}

### Crear la *path operation* del callback

Para crear la *path operation* del callback utiliza el mismo `APIRouter` que creaste anteriormente.

Debería verse como una *path operation* normal de FastAPI:

* Probablemente debería tener una declaración del body que debería recibir, por ejemplo `body: InvoiceEvent`.

        assertEquals("Singleton context is already initialized", e.getMessage());
    }

    @Test
    void testInitLoadsJcifsPropertiesFile(@TempDir Path tempDir) throws IOException, CIFSException {
        // Test that jcifs.properties file is loaded
        Path jcifsPropertiesPath = tempDir.resolve("jcifs.properties");
        Files.writeString(jcifsPropertiesPath, "jcifs.smb.client.nativeOs=FileOS");

 *     <li>{@linkplain org.apache.maven.api.services.ProjectManager#attachArtifact(Session, Project, Path) artifacts to be attached to a project}</li>
 * </ul>
 *
 * <p>For the main artifact and attached artifacts, the
 * {@link org.apache.maven.api.services.ArtifactManager ArtifactManager} service must be used
 * to point the artifact to a {@link Path} during the packaging phase.</p>
 *
 * @since 4.0.0
 * @see Project#getMainArtifact()