</div>

Und öffnen Sie die Dokumentation unter <a href="http://127.0.0.1:8000/docs" class="external-link" target="_blank">http://127.0.0.1:8000/docs</a>.

Sie sehen die automatische API-Dokumentation für die Hauptanwendung, welche nur deren eigene _Pfadoperationen_ anzeigt:

<img src="/img/tutorial/sub-applications/image01.png">

            AND LOWER THAN CURRENT BASE VERSION (from `version.txt` on this branch).
            The difference must identically match <a href="${mainApiChangesJsonFile.asFile.path}">accepted-public-api-changes.json</a> like .json file in <a href="${apiChangesJsonDirectory.asFile.path}">accepted-changes</a> directory, no more, no less - otherwise the task will fail.
            </p>
            ${writeFilterPreset(project)}

{!../../docs_src/middleware/tutorial001.py!}
```

/// tip

✔️ 🤯 👈 🛃 © 🎚 💪 🚮 <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers" class="external-link" target="_blank">⚙️ '✖-' 🔡</a>.

✋️ 🚥 👆 ✔️ 🛃 🎚 👈 👆 💚 👩‍💻 🖥 💪 👀, 👆 💪 🚮 👫 👆 ⚜ 📳 ([⚜ (✖️-🇨🇳 ℹ 🤝)](cors.md){.internal-link target=_blank}) ⚙️ 🔢 `expose_headers` 📄 <a href="https://www.starlette.io/middleware/#corsmiddleware" class="external-link" target="_blank">💃 ⚜ 🩺</a>.

///

## Benutzerdefinierte Header

Beachten Sie, dass benutzerdefinierte proprietäre Header <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers" class="external-link" target="_blank">mittels des Präfix 'X-'</a> hinzugefügt werden können.

## Details zum `Request`-Objekt

Da **FastAPI** unter der Haube eigentlich **Starlette** ist, mit einer Ebene von mehreren Tools darüber, können Sie Starlette's <a href="https://www.starlette.io/requests/" class="external-link" target="_blank">`Request`</a>-Objekt direkt verwenden, wenn Sie es benötigen.

And as the `Response` can be used frequently to set headers and cookies, **FastAPI** also provides it at `fastapi.Response`.

///

## Custom Headers

Keep in mind that custom proprietary headers can be added <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers" class="external-link" target="_blank">using the 'X-' prefix</a>.

 * override one or more methods to modify the behavior of the backing map as desired per the <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * <p><b>{@code default} method warning:</b> This class forwards calls to <i>only some</i> {@code
 * default} methods. Specifically, it forwards calls only for methods that existed <a
 * href="https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ConcurrentMap.html">before

 *
 * <ul>
 *   <li><a
 *       href="https://github.com/google/guava/wiki/GraphsExplained#equals-hashcode-and-graph-equivalence">
 *       {@code equals()}, {@code hashCode()}, and graph equivalence</a>
 *   <li><a href="https://github.com/google/guava/wiki/GraphsExplained#synchronization">
 *       Synchronization policy</a>
 *   <li><a href="https://github.com/google/guava/wiki/GraphsExplained#notes-for-implementors">Notes

 *
 * <h2>Prefer <a href="https://github.com/ben-manes/caffeine/wiki">Caffeine</a> over Guava's caching
 * API</h2>
 *
 * <p>The successor to Guava's caching API is <a
 * href="https://github.com/ben-manes/caffeine/wiki">Caffeine</a>. Its API is designed to make it a
 * nearly drop-in replacement. It requires Java 8+, and is not available for Android or GWT/J2CL,

Например, у вас есть файл `main.py`:

```Python hl_lines="3"
import os

name = os.getenv("MY_NAME", "World")
print(f"Hello {name} from Python")
```

/// tip

Второй аргумент <a href=«https://docs.python.org/3.8/library/os.html#os.getenv» class=«external-link» target=«_blank»>`os.getenv()`</a> - это возвращаемое по умолчанию значение.