query: str = Query(default=..., max_length=10),
    session: str = Cookie(default=..., min_length=3),
    x_trace: str = Header(default=..., title="Tracing header"),
):
    return {"message": "Hello World"}
```

...all these parameters are required because the default value is `...` (Ellipsis).

@app.get("/items/")
async def read_items(commons: dict = Depends(common_parameters)):
    return {"message": "Hello Items!", "params": commons}


@app.get("/users/")
async def read_users(commons: dict = Depends(common_parameters)):
    return {"message": "Hello Users!", "params": commons}


client = TestClient(app)


async def override_dependency(q: Union[str, None] = None):

    assert response.json() == {
        "message": "Hello Users!",
        "params": {"q": None, "skip": 5, "limit": 10},
    }


def test_override_in_users_with_q():
    response = client.get("/users/?q=foo")
    assert response.status_code == 200, response.text
    assert response.json() == {
        "message": "Hello Users!",
        "params": {"q": "foo", "skip": 5, "limit": 10},
    }

    from docs_src.dependency_testing.tutorial001_an_py310 import client

    response = client.get("/users/")
    assert response.status_code == 200, response.text
    assert response.json() == {
        "message": "Hello Users!",
        "params": {"q": None, "skip": 5, "limit": 10},
    }


@needs_py310
def test_override_in_users_with_q():
    from docs_src.dependency_testing.tutorial001_an_py310 import client

    $ echo "Hello $MY_NAME"

    Hello Wade Wilson
    ```

    </div>

=== "Windows PowerShell"

    <div class="termy">

    ```console
    // Erstelle eine Umgebungsvariable MY_NAME
    $ $Env:MY_NAME = "Wade Wilson"

    // Verwende sie mit anderen Programmen, etwa
    $ echo "Hello $Env:MY_NAME"

    Hello Wade Wilson
    ```

    </div>

```txt
Hello, World from Flask!
```

Und wenn Sie auf <a href="http://localhost:8000/v2" class="external-link" target="_blank">http://localhost:8000/v2</a> gehen, sehen Sie die Response von FastAPI:

```JSON
{
    "message": "Hello World"
}

from fastapi import FastAPI

app = FastAPI()


@app.get("/")
def root():

from typing import Optional


def say_hi(name: Optional[str] = None):
    if name is not None:
        print(f"Hey {name}!")
    else:

from fastapi import FastAPI

my_awesome_api = FastAPI()


@my_awesome_api.get("/")
async def root():

from fastapi import FastAPI

app = FastAPI(swagger_ui_parameters={"syntaxHighlight": False})


@app.get("/users/{username}")
async def read_user(username: str):