from fastapi import Depends, FastAPI

app = FastAPI()


fake_items_db = [{"item_name": "Foo"}, {"item_name": "Bar"}, {"item_name": "Baz"}]


class CommonQueryParams:
    def __init__(self, q: str | None = None, skip: int = 0, limit: int = 100):
        self.q = q
        self.skip = skip
        self.limit = limit


@app.get("/items/")
async def read_items(commons=Depends(CommonQueryParams)):
    response = {}
    if commons.q:

from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    price: float
    is_offer: Union[bool, None] = None


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}


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

```Python hl_lines="11  13-14"
{!> ../../docs_src/response_model/tutorial004.py!}
```

////

* `description: Union[str, None] = None` (или `str | None = None` в Python 3.10), где `None` является значением по умолчанию.
* `tax: float = 10.5`, где `10.5` является значением по умолчанию.
* `tags: List[str] = []`, где пустой список `[]` является значением по умолчанию.

Sie können den `jsonable_encoder` verwenden, um die empfangenen Daten in etwas zu konvertieren, das als JSON gespeichert werden kann (in z. B. einer NoSQL-Datenbank). Zum Beispiel, um ein `datetime` in einen `str` zu konvertieren.

//// tab | Python 3.10+

```Python hl_lines="28-33"
{!> ../../docs_src/body_updates/tutorial001_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="30-35"

```Python
q: Union[str, None] = None
```

Ou como em Python 3.10 e versões superiores:

```Python
q: str | None = None
```

Por exemplo:

//// tab | Python 3.10+

```Python hl_lines="26"
{!> ../../docs_src/body_multiple_params/tutorial004_py310.py!}

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

Here the query parameter `needy` is a required query parameter of type `str`.

If you open in your browser a URL like:

```
http://127.0.0.1:8000/items/foo-item
```

...without adding the required parameter `needy`, you will see an error like:

```JSON
{

from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    price: float
    is_offer: Union[bool, None] = None


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}


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

            detail="Incorrect username or password",
            headers={"WWW-Authenticate": "Basic"},
        )
    return credentials.username


@app.get("/users/me")
def read_current_user(username: Annotated[str, Depends(get_current_username)]):

/// tip

Ce n'est probablement pas aussi important ou nécessaire si vous utilisez `Annotated`.

///

Disons que vous voulez déclarer le paramètre de requête `q` comme un `str` requis.

Et vous n'avez pas besoin de déclarer autre chose pour ce paramètre, donc vous n'avez pas vraiment besoin d'utiliser `Query`.

, 🔢 🔛 ⚫️ 🔜 🛠️ 🕐 🔠 🌀 ❌. & ⤴️ 💲 📨 🔠 👈 🌀 ❌ 🔜 ⚙️ 🔄 & 🔄 🕐❔ 🔢 🤙 ⏮️ ⚫️❔ 🎏 🌀 ❌.

🖼, 🚥 👆 ✔️ 🔢:

```Python
@lru_cache
def say_hi(name: str, salutation: str = "Ms."):
    return f"Hello {salutation} {name}"
```

👆 📋 💪 🛠️ 💖 👉:

```mermaid
sequenceDiagram

participant code as Code
participant function as say_hi()