@app.get("/callable-gen-dependency")
async def get_callable_gen_dependency(value: str = Depends(callable_gen_dependency)):
    return value


@app.get("/async-callable-dependency")
async def get_async_callable_dependency(
    value: str = Depends(async_callable_dependency),
):
    return value


@app.get("/async-callable-gen-dependency")
async def get_async_callable_gen_dependency(
    value: str = Depends(async_callable_gen_dependency),
):

import time
from typing import Callable

from fastapi import APIRouter, FastAPI, Request, Response
from fastapi.routing import APIRoute


class TimedRoute(APIRoute):
    def get_route_handler(self) -> Callable:
        original_route_handler = super().get_route_handler()

        async def custom_route_handler(request: Request) -> Response:
            before = time.time()
            response: Response = await original_route_handler(request)

# Abhängigkeiten – `Depends()` und `Security()`

## `Depends()`

Abhängigkeiten werden hauptsächlich mit der speziellen Funktion `Depends()` behandelt, die ein Callable entgegennimmt.

Hier finden Sie deren Referenz und Parameter.

Sie können sie direkt von `fastapi` importieren:

```python
from fastapi import Depends
```

::: fastapi.Depends

## `Security()`

from typing import Callable, List

from fastapi import Body, FastAPI, HTTPException, Request, Response
from fastapi.exceptions import RequestValidationError
from fastapi.routing import APIRoute


class ValidationErrorLoggingRoute(APIRoute):
    def get_route_handler(self) -> Callable:
        original_route_handler = super().get_route_handler()

        async def custom_route_handler(request: Request) -> Response:
            try:

from contextvars import ContextVar
from typing import Any, Awaitable, Callable, Dict, Optional

from fastapi import Depends, FastAPI, Request, Response
from fastapi.testclient import TestClient

legacy_request_state_context_var: ContextVar[Optional[Dict[str, Any]]] = ContextVar(
    "legacy_request_state_context_var", default=None
)

app = FastAPI()


async def set_up_request_state_dependency():
    request_state = {"user": "deadpond"}

from typing import Any, Callable, List, Optional, Sequence

from fastapi._compat import ModelField
from fastapi.security.base import SecurityBase


class SecurityRequirement:
    def __init__(
        self, security_scheme: SecurityBase, scopes: Optional[Sequence[str]] = None
    ):
        self.security_scheme = security_scheme
        self.scopes = scopes


class Dependant:
    def __init__(
        self,
        *,

The `oauth2_scheme` variable is an instance of `OAuth2PasswordBearer`, but it is also a "callable".

It could be called as:

```Python
oauth2_scheme(some, parameters)
```

So, it can be used with `Depends`.

### Use it

But we want to be able to parameterize that fixed content.

## A "callable" instance

In Python there's a way to make an instance of a class a "callable".

Not the class itself (which is already a callable), but an instance of that class.

To do that, we declare a method `__call__`:

=== "Python 3.9+"

    ```Python hl_lines="12"

# Dependencies - `Depends()` and `Security()`

## `Depends()`

Dependencies are handled mainly with the special function `Depends()` that takes a callable.

Here is the reference for it and its parameters.

You can import it directly from `fastapi`:

```python
from fastapi import Depends
```

::: fastapi.Depends

## `Security()`

Aber wir wollen diesen vordefinierten Inhalt per Parameter festlegen können.

## Eine „aufrufbare“ Instanz

In Python gibt es eine Möglichkeit, eine Instanz einer Klasse „aufrufbar“ („callable“) zu machen.

Nicht die Klasse selbst (die bereits aufrufbar ist), sondern eine Instanz dieser Klasse.

Dazu deklarieren wir eine Methode `__call__`:

=== "Python 3.9+"

    ```Python hl_lines="12"