///

### 导入 `Depends` { #import-depends }

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[3] *}

### 在“dependant”中声明依赖项 { #declare-the-dependency-in-the-dependant }

与在*路径操作函数*的参数中使用 `Body`、`Query` 等相同，给参数使用 `Depends` 来声明一个新的依赖项：

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[13,18] *}

虽然你在函数参数中使用 `Depends` 的方式与 `Body`、`Query` 等相同，但 `Depends` 的工作方式略有不同。

这里只能给 `Depends` 传入一个参数。

//// tab | Python 3.10+

```Python hl_lines="1"
async def needy_dependency(fresh_value: Annotated[str, Depends(get_value, use_cache=False)]):
    return {"fresh_value": fresh_value}
```

////

//// tab | Python 3.10+ без Annotated

/// tip | Подсказка

/// info | Información Técnica

`Security` es en realidad una subclase de `Depends`, y tiene solo un parámetro extra que veremos más adelante.

Pero al usar `Security` en lugar de `Depends`, **FastAPI** sabrá que puede declarar scopes de seguridad, usarlos internamente y documentar la API con OpenAPI.

Pero cuando importas `Query`, `Path`, `Depends`, `Security` y otros de `fastapi`, en realidad son funciones que devuelven clases especiales.

   * population, this is an estimator of the population standard deviation of the population which
   * is less biased than {@link #populationStandardDeviation()} (the unbiased estimator depends on
   * the distribution). The count must be greater than one.
   *
   * <p>This is not guaranteed to return zero when the dataset consists of the same value multiple

from collections.abc import Awaitable, Callable
from contextvars import ContextVar
from typing import Any

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

legacy_request_state_context_var: ContextVar[dict[str, Any] | None] = ContextVar(
    "legacy_request_state_context_var", default=None
)

app = FastAPI()


async def set_up_request_state_dependency():

/// info | Détails techniques

`Security` est en réalité une sous-classe de `Depends`, et elle n’a qu’un paramètre supplémentaire que nous verrons plus tard.

Mais en utilisant `Security` au lieu de `Depends`, **FastAPI** saura qu’il peut déclarer des scopes de sécurité, les utiliser en interne et documenter l’API avec OpenAPI.

    return User()


@app.get("/items/")
def read_items(user: User = Depends(get_current_user)):
    ...


@app.post("/items/")
def create_item(*, user: User = Depends(get_current_user), item: Item):
    ...


@app.get("/items/{item_id}")
def read_item(*, user: User = Depends(get_current_user), item_id: int):
    ...


@app.delete("/items/{item_id}")

To understand more about it, see the section [Benchmarks](https://fastapi.tiangolo.com/benchmarks/).

## Dependencies

FastAPI depends on Pydantic and Starlette.

### `standard` Dependencies

When you install FastAPI with `pip install "fastapi[standard]"` it comes with the `standard` group of optional dependencies:

Used by Pydantic:

{* ../../docs_src/security/tutorial002_an_py310.py hl[19:22,26:27] *}

## Den aktuellen Benutzer einfügen { #inject-the-current-user }

Und jetzt können wir wiederum `Depends` mit unserem `get_current_user` in der *Pfadoperation* verwenden:

{* ../../docs_src/security/tutorial002_an_py310.py hl[31] *}

Beachten Sie, dass wir als Typ von `current_user` das Pydantic-Modell `User` deklarieren.

      return className.indexOf('$') == -1;
    }

    /**
     * Loads (but doesn't link or initialize) the class.
     *
     * @throws LinkageError when there were errors in loading classes that this class depends on.
     *     For example, {@link NoClassDefFoundError}.
     */
    public Class<?> load() {
      try {
        return loader.loadClass(className);
      } catch (ClassNotFoundException e) {