この場合（`Annotated` を使わない場合）、関数内のデフォルト値 `None` を `Query()` に置き換える必要があるため、`Query(default=None)` のパラメータでデフォルト値を設定する必要があります。これは（少なくとも FastAPI にとっては）そのデフォルト値を定義するのと同じ目的を果たします。

なので:

```Python
q: str | None = Query(default=None)
```

...はデフォルト値 `None` を持つオプショナルなパラメータになり、以下と同じです:


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

ただし `Query` のバージョンでは、クエリパラメータであることを明示的に宣言しています。

    font-size: 10pt;
    color: #000000;
    text-decoration: none
}
a.plain {
    display: inline;
    float: none;
    width: auto;
    height: auto
}
a.sort {
    display: block;
    float: left;
    width: 100px;
    height: 15px;
    font-family: Verdana, sans-serif;
    font-size: 8pt;
    font-weight: bold;
    text-decoration: none;
    color: #000000;
    background-color: #d0d0d0;

 */
@Experimental
@Immutable
public enum DependencyScope {

    /**
     * None. Allows you to declare dependencies (for example to alter reactor build order) but in reality dependencies
     * in this scope are not part of any path scope.
     */
    NONE("none", false),

    /**
     * Undefined. When no scope is explicitly given, UNDEFINED will be used, but its meaning will depend on

from typing import Annotated

from fastapi import Body, FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None


@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Annotated[Item, Body(embed=True)]):
    results = {"item_id": item_id, "item": item}

class SubItem(BaseModel):
    subname: str
    sub_description: str | None = None
    tags: list[str] = []
    model_config = {"json_schema_serialization_defaults_required": True}


class Item(BaseModel):
    name: str
    description: str | None = None
    sub: SubItem | None = None
    model_config = {"json_schema_serialization_defaults_required": True}

from pydantic.v1 import BaseModel


class Item(BaseModel):
    name: str
    description: str | None = None

    assert response.json() == {
        "name": "Special Offer",
        "description": None,
        "price": 38.6,
        "items": [
            {
                "name": "Foo",
                "description": None,
                "price": 35.4,
                "tax": None,
                "tags": [],
                "images": [
                    {

from fastapi import Body, FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None


@app.put("/items/{item_id}")
async def update_item(
    item_id: int,
    item: Item = Body(
        examples=[
            {
                "name": "Foo",
                "description": "A very nice Item",

class User(BaseModel):
    username: str


def get_current_user(oauth_header: str | None = Security(api_key)):
    if oauth_header is None:
        return None
    user = User(username=oauth_header)
    return user


@app.get("/users/me")
def read_current_user(current_user: User = Depends(get_current_user)):
    if current_user is None:
        return {"msg": "Create an account first"}
    else:
        return current_user

from typing import Annotated

from fastapi import Body, FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None


@app.put("/items/{item_id}")
async def update_item(
    item_id: int,
    item: Annotated[
        Item,
        Body(
            examples=[
                {