## Primeira dependência "dependable" { #first-dependency-dependable }

Você pode criar uma primeira dependência ("dependable") dessa forma:

{* ../../docs_src/dependencies/tutorial005_an_py310.py hl[8:9] *}

Esse código declara um parâmetro de consulta opcional, `q`, com o tipo `str`, e então retorna esse parâmetro.

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

### Declarar la dependencia, en el "dependant" { #declare-the-dependency-in-the-dependant }

De la misma forma en que usas `Body`, `Query`, etc. con los parámetros de tu *path operation function*, usa `Depends` con un nuevo parámetro:

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

@pytest.fixture(
    name="client",
    params=[
        pytest.param("tutorial001_py39"),
        pytest.param("tutorial001_py310", marks=needs_py310),
        pytest.param("tutorial001_an_py39"),
        pytest.param("tutorial001_an_py310", marks=needs_py310),
    ],
)
def get_client(request: pytest.FixtureRequest) -> TestClient:
    mod = importlib.import_module(
        f"docs_src.path_params_numeric_validations.{request.param}"
    )

@pytest.fixture(
    name="client",
    params=[
        "tutorial002_py39",
        pytest.param("tutorial002_py310", marks=needs_py310),
        "tutorial002_an_py39",
        pytest.param("tutorial002_an_py310", marks=needs_py310),
    ],
)
def get_client(request: pytest.FixtureRequest):
    mod = importlib.import_module(f"docs_src.background_tasks.{request.param}")

    client = TestClient(mod.app)
    return client

## 导入 Path

首先，从 `fastapi` 导入 `Path`：

{* ../../docs_src/path_params_numeric_validations/tutorial001_an_py310.py hl[1,3] *}

## 声明元数据

你可以声明与 `Query` 相同的所有参数。

例如，要声明路径参数 `item_id`的 `title` 元数据值，你可以输入：

{* ../../docs_src/path_params_numeric_validations/tutorial001_an_py310.py hl[10] *}

/// note

路径参数总是必需的，因为它必须是路径的一部分。

所以，你应该在声明时使用 `...` 将其标记为必需参数。

@pytest.fixture(
    name="client",
    params=[
        pytest.param("tutorial001_py39"),
        pytest.param("tutorial001_py310", marks=needs_py310),
        pytest.param("tutorial001_an_py39"),
        pytest.param("tutorial001_an_py310", marks=needs_py310),
    ],
)
def get_client(request: pytest.FixtureRequest):
    mod = importlib.import_module(f"docs_src.extra_data_types.{request.param}")

    client = TestClient(mod.app)
    return client

### `OAuth2PasswordRequestForm` { #oauth2passwordrequestform }

Primeiro, importe `OAuth2PasswordRequestForm` e use-o como uma dependência com `Depends` na *operação de rota* para `/token`:

{* ../../docs_src/security/tutorial003_an_py310.py hl[4,78] *}

`OAuth2PasswordRequestForm` é uma dependência de classe que declara um corpo de formulário com:

* O `username`.
* A `password`.

Para lograr eso, importa `JSONResponse`, y devuelve tu contenido allí directamente, configurando el `status_code` que deseas:

{* ../../docs_src/additional_status_codes/tutorial001_an_py310.py hl[4,25] *}

/// warning | Advertencia

Cuando devuelves un `Response` directamente, como en el ejemplo anterior, se devuelve directamente.

No se serializará con un modelo, etc.

@pytest.fixture(
    name="client",
    params=[
        "tutorial001_py39",
        pytest.param("tutorial001_py310", marks=needs_py310),
        "tutorial001_an_py39",
        pytest.param("tutorial001_an_py310", marks=needs_py310),
    ],
)
def get_client(request: pytest.FixtureRequest):
    mod = importlib.import_module(f"docs_src.additional_status_codes.{request.param}")

    client = TestClient(mod.app)

@pytest.fixture(
    name="client",
    params=[
        pytest.param("tutorial009_py39"),
        pytest.param("tutorial009_py310", marks=needs_py310),
        pytest.param("tutorial009_an_py39"),
        pytest.param("tutorial009_an_py310", marks=needs_py310),
    ],
)
def get_client(request: pytest.FixtureRequest):
    mod = importlib.import_module(
        f"docs_src.query_params_str_validations.{request.param}"
    )