Beachten Sie, dass Sie keine spezielle Klasse erstellen und diese irgendwo an **FastAPI** übergeben müssen, um sie zu „registrieren“ oder so ähnlich.

Sie übergeben es einfach an `Depends` und **FastAPI** weiß, wie der Rest erledigt wird.

///

## `Annotated`-Abhängigkeiten wiederverwenden { #share-annotated-dependencies }

In den Beispielen oben sehen Sie, dass es ein kleines bisschen **Codeverdoppelung** gibt.

This also means that if you are inside a utility function that you are calling inside of your *path operation function*, and you raise the `HTTPException` from inside of that utility function, it won't run the rest of the code in the *path operation function*, it will terminate that request right away and send the HTTP error from the `HTTPException` to the client.

/// check

Notice that you don't have to create a special class and pass it somewhere to **FastAPI** to "register" it or anything similar.

You just pass it to `Depends` and **FastAPI** knows how to do the rest.

///

## Share `Annotated` dependencies { #share-annotated-dependencies }

In the examples above, you see that there's a tiny bit of **code duplication**.

        }

        /**
         * A comparable value for the empty-string qualifier. This one is used to determine if a given qualifier makes
         * the version older than one without a qualifier, or more recent.
         */
        private static final String RELEASE_VERSION_INDEX = String.valueOf(QUALIFIERS.indexOf(""));

        private final String value;

        StringItem(String value, boolean followedByDigit) {

Par exemple, si le **serveur d'application** ne reçoit des communications que du **proxy** de confiance, vous pouvez définir `--forwarded-allow-ips="*"` pour lui faire faire confiance à toutes les IP entrantes, puisqu'il ne recevra des requêtes que depuis l'IP utilisée par le **proxy**.

The important thing to remember is that **the first *type parameter*** you pass to `Annotated` is the **actual type**. The rest, is just metadata for other tools.

For now, you just need to know that `Annotated` exists, and that it's standard Python. 😎

Later you will see how **powerful** it can be.

/// tip

<div style="text-align: right; margin-right: 10%;">Kabir Khan - <strong>Microsoft</strong> <a href="https://github.com/fastapi/fastapi/pull/26"><small>(ref)</small></a></div>

---

"_We adopted the **FastAPI** library to spawn a **REST** server that can be queried to obtain **predictions**. [for Ludwig]_"

<div style="text-align: right; margin-right: 10%;">Kabir Khan - <strong>Microsoft</strong> <a href="https://github.com/fastapi/fastapi/pull/26"><small>(ref)</small></a></div>

---

"_我們採用了 **FastAPI** 函式庫來啟動一個 **REST** 伺服器，供查詢以取得**預測**。[for Ludwig]_"

<div style="text-align: right; margin-right: 10%;">Piero Molino, Yaroslav Dudin, and Sai Sumanth Miryala - <strong>Uber</strong> <a href="https://eng.uber.com/ludwig-v0-2/"><small>(ref)</small></a></div>

     * {@code expectedValuesPerKey} is a good estimate.
     *
     * <p>This may be called more than once; each newly added key will use the most recent call to
     * {@link #expectedValuesPerKey} as its hint.
     *
     * @throws IllegalArgumentException if {@code expectedValuesPerKey} is negative
     * @since 33.3.0
     */
    @CanIgnoreReturnValue

    This is where we'll put the `requirements.txt` file and the `app` directory.

3. Copy the file with the requirements to the `/code` directory.

    Copy **only** the file with the requirements first, not the rest of the code.

    As this file **doesn't change often**, Docker will detect it and use the **cache** for this step, enabling the cache for the next step too.

4. Install the package dependencies in the requirements file.