), "overridden configs should be preserved"
    assert (
        '"deepLinking": true' not in response.text
    ), "overridden configs should not include the old value"
    assert (
        '"syntaxHighlight": false' not in response.text
    ), "not used parameters should not be included"
    assert (
        '"dom_id": "#swagger-ui"' in response.text
    ), "default configs should be preserved"

* **`300`** and above are for "Redirection".  Responses with these status codes may or may not have a body, except for `304`, "Not Modified", which must not have one.
* **`400`** and above are for "Client error" responses. These are the second type you would probably use the most.
    * An example is `404`, for a "Not Found" response.

        user_dict = db[username]
        return UserInDB(**user_dict)


def authenticate_user(fake_db, username: str, password: str):
    user = get_user(fake_db, username)
    if not user:
        return False
    if not verify_password(password, user.hashed_password):
        return False
    return user


def create_access_token(data: dict, expires_delta: timedelta | None = None):
    to_encode = data.copy()

        user_dict = db[username]
        return UserInDB(**user_dict)


def authenticate_user(fake_db, username: str, password: str):
    user = get_user(fake_db, username)
    if not user:
        return False
    if not verify_password(password, user.hashed_password):
        return False
    return user


def create_access_token(data: dict, expires_delta: timedelta | None = None):
    to_encode = data.copy()

    responses={404: {"description": "Not found"}},
)


fake_items_db = {"plumbus": {"name": "Plumbus"}, "gun": {"name": "Portal Gun"}}


@router.get("/")
async def read_items():
    return fake_items_db


@router.get("/{item_id}")
async def read_item(item_id: str):
    if item_id not in fake_items_db:
        raise HTTPException(status_code=404, detail="Item not found")

# TODO: remove when deprecating Pydantic v1
def test_upload_file_invalid():
    with pytest.raises(ValueError):
        UploadFile.validate("not a Starlette UploadFile")


def test_upload_file_invalid_pydantic_v2():
    with pytest.raises(ValueError):
        UploadFile._validate("not a Starlette UploadFile", {})


def test_default_placeholder_equals():
    placeholder_1 = Default("a")
    placeholder_2 = Default("a")

app = FastAPI()


@app.post("/files/")
async def create_file(file: Union[bytes, None] = File(default=None)):
    if not file:
        return {"message": "No file sent"}
    else:
        return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(file: Union[UploadFile, None] = None):
    if not file:
        return {"message": "No upload file sent"}
    else:

async def login(form_data: OAuth2PasswordRequestForm = Depends()):
    user_dict = fake_users_db.get(form_data.username)
    if not user_dict:
        raise HTTPException(status_code=400, detail="Incorrect username or password")
    user = UserInDB(**user_dict)
    hashed_password = fake_hash_password(form_data.password)
    if not hashed_password == user.hashed_password:
        raise HTTPException(status_code=400, detail="Incorrect username or password")

from fastapi import FastAPI

description = """
ChimichangApp API helps you do awesome stuff. 🚀

## Items

You can **read items**.

## Users

You will be able to:

* **Create users** (_not implemented_).
* **Read users** (_not implemented_).
"""

app = FastAPI(
    title="ChimichangApp",
    description=description,
    summary="Deadpool's favorite app. Nuff said.",
    version="0.0.1",

When you declare a default value for non-path parameters (for now, we have only seen query parameters), then it is not required.

If you don't want to add a specific value but just make it optional, set the default as `None`.

But when you want to make a query parameter required, you can just not declare any default value:

```Python hl_lines="6-7"
{!../../../docs_src/query_params/tutorial005.py!}
```