app = FastAPI()


class UserBase(BaseModel):
    username: str
    email: EmailStr
    full_name: str | None = None


class UserIn(UserBase):
    password: str


class UserOut(UserBase):
    pass


class UserInDB(UserBase):
    hashed_password: str


def fake_password_hasher(raw_password: str):
    return "supersecret" + raw_password


def fake_save_user(user_in: UserIn):

#### Definieren eines *Pfadoperation-Dekorators*

```Python hl_lines="6"
{!../../../docs_src/first_steps/tutorial001.py!}
```

Das `@app.get("/")` sagt **FastAPI**, dass die Funktion direkt darunter für die Bearbeitung von Anfragen zuständig ist, die an:

 * den Pfad `/`
 * unter der Verwendung der <abbr title="eine HTTP GET Methode"><code>get</code>-Operation</abbr> gehen

class FooBaseModel(BaseModel):
    if PYDANTIC_V2:
        model_config = ConfigDict(extra="forbid")
    else:

        class Config:
            extra = "forbid"


class Foo(FooBaseModel):
    pass


app = FastAPI()


@app.post("/")
async def post(
    foo: Union[Foo, None] = None,
):
    return foo


client = TestClient(app)


def test_call_invalid():

* **Uvicorn**:
    * Bietet die beste Leistung, da außer dem Server selbst nicht viel zusätzlicher Code vorhanden ist.

The middleware function receives:

* The `request`.
* A function `call_next` that will receive the `request` as a parameter.
    * This function will pass the `request` to the corresponding *path operation*.
    * Then it returns the `response` generated by the corresponding *path operation*.
* You can then modify further the `response` before returning it.

* Sie können die `response` dann weiter modifizieren, bevor Sie sie zurückgeben.

```Python hl_lines="8-9  11  14"
{!../../../docs_src/middleware/tutorial001.py!}
```

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

    ---> 100%
    ```

    </div>

    ...or any other ASGI server.

## Run the Server Program

If you installed an ASGI server manually, you would normally need to pass an import string in a special format for it to import your FastAPI application:

=== "Uvicorn"

    <div class="termy">

    ```console
    $ uvicorn main:app --host 0.0.0.0 --port 80

## Recap

You can use Pydantic's `Field` to declare extra validations and metadata for model attributes.

!!! tip
    The main ("official") language is English, located at `docs/en/`.

Now run the live server for the docs in Spanish:

<div class="termy">

```console
// Use the command "live" and pass the language code as a CLI argument
$ python ./scripts/docs.py live es

<span style="color: green;">[INFO]</span> Serving on http://127.0.0.1:8008
<span style="color: green;">[INFO]</span> Start watching changes

def get_value_or_default(
    first_item: Union[DefaultPlaceholder, DefaultType],
    *extra_items: Union[DefaultPlaceholder, DefaultType],
) -> Union[DefaultPlaceholder, DefaultType]:
    """
    Pass items or `DefaultPlaceholder`s by descending priority.

    The first one to _not_ be a `DefaultPlaceholder` will be returned.

    Otherwise, the first item (a `DefaultPlaceholder`) will be returned.
    """