This is not a limitation of **FastAPI**, it's part of the HTTP protocol.

///

## Recap

{!> ../../docs_src/query_params/tutorial002.py!}
```

////

В этом случае, параметр  `q` будет не обязательным и будет иметь значение `None` по умолчанию.

/// check | "Важно"

Также обратите внимание, что **FastAPI** достаточно умён чтобы заметить, что параметр `item_id` является path-параметром, а `q` нет, поэтому, это параметр запроса.

///

## Преобразование типа параметра запроса

가능하다면 `Annotated`가 달린 버전을 권장합니다.

///

```Python hl_lines="4"
{!> ../../docs_src/body_fields/tutorial001.py!}
```

////

/// warning | "경고"

`Field`는 다른 것들처럼 (`Query`, `Path`, `Body` 등) `fastapi`에서가 아닌 `pydantic`에서 바로 임포트 되는 점에 주의하세요.

///

## 모델 어트리뷰트 선언

그 다음 모델 어트리뷰트와 함께 `Field`를 사용할 수 있습니다:

//// tab | Python 3.10+

```Python hl_lines="11-14"

In that case, you can disable this feature in **FastAPI**, with the parameter `separate_input_output_schemas=False`.

/// info

Support for `separate_input_output_schemas` was added in FastAPI `0.102.0`. 🤓

///

{* ../../docs_src/separate_openapi_schemas/tutorial002_py310.py hl[10] *}

from fastapi.testclient import TestClient

from docs_src.cors.tutorial001 import app


def test_cors():
    client = TestClient(app)
    # Test pre-flight response
    headers = {
        "Origin": "https://localhost.tiangolo.com",
        "Access-Control-Request-Method": "GET",
        "Access-Control-Request-Headers": "X-Example",
    }
    response = client.options("/", headers=headers)
    assert response.status_code == 200, response.text

import os
from pathlib import Path

import pytest
from fastapi.testclient import TestClient


@pytest.fixture(scope="module")
def client():
    static_dir: Path = Path(os.getcwd()) / "static"
    print(static_dir)
    static_dir.mkdir(exist_ok=True)
    from docs_src.custom_docs_ui.tutorial002 import app

    with TestClient(app) as client:
        yield client
    static_dir.rmdir()

# Exécuter un serveur manuellement - Uvicorn

La principale chose dont vous avez besoin pour exécuter une application **FastAPI** sur une machine serveur distante est un programme serveur ASGI tel que **Uvicorn**.

Il existe 3 principales alternatives :

* <a href="https://www.uvicorn.org/" class="external-link" target="_blank">Uvicorn</a> : un serveur ASGI haute performance.

```Python hl_lines="9"
{!> ../../docs_src/query_params/tutorial002.py!}
```

////

In this case, the function parameter `q` will be optional, and will be `None` by default.

/// check

Also notice that **FastAPI** is smart enough to notice that the path parameter `item_id` is a path parameter and `q` is not, so, it's a query parameter.

///

## Query parameter type conversion

/// tip

尽可能选择使用 `Annotated` 的版本。

///

```Python hl_lines="4"
{!> ../../docs_src/body_fields/tutorial001.py!}
```

////

/// warning | "警告"

注意，与从 `fastapi` 导入 `Query`，`Path`、`Body` 不同，要直接从 `pydantic` 导入 `Field` 。

///

## 声明模型属性

然后，使用 `Field` 定义模型的属性：

//// tab | Python 3.10+

```Python hl_lines="11-14"

from dirty_equals import IsDict
from fastapi.testclient import TestClient

from docs_src.security.tutorial003_an import app

client = TestClient(app)


def test_login():
    response = client.post("/token", data={"username": "johndoe", "password": "secret"})
    assert response.status_code == 200, response.text
    assert response.json() == {"access_token": "johndoe", "token_type": "bearer"}


def test_login_incorrect_password():