class CommonHeaders(BaseModel):
    host: str
    save_data: bool
    if_modified_since: Union[str, None] = None
    traceparent: Union[str, None] = None
    x_tag: list[str] = []


@app.get("/items/")
async def read_items(headers: CommonHeaders = Header()):

    media_type = "application/x-level-5"


async def dep0(response: Response):
    response.headers["x-level0"] = "True"


async def dep1(response: Response):
    response.headers["x-level1"] = "True"


async def dep2(response: Response):
    response.headers["x-level2"] = "True"


async def dep3(response: Response):
    response.headers["x-level3"] = "True"


async def dep4(response: Response):

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=[
                {
                    "name": "Foo",
                    "description": "A very nice Item",

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


app = FastAPI()


@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Item, q: Union[str, None] = None):
    result = {"item_id": item_id, **item.model_dump()}
    if q:
        result.update({"q": q})

    description: str | None = None
    price: float
    tax: float | None = None


class User(BaseModel):
    username: str
    full_name: str | None = None


@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Item, user: User, importance: int = Body()):
    results = {"item_id": item_id, "item": item, "user": user, "importance": importance}

//// tab | Python 3.9+

```Python hl_lines="1"
async def needy_dependency(fresh_value: Annotated[str, Depends(get_value, use_cache=False)]):
    return {"fresh_value": fresh_value}
```

////

//// tab | Python 3.9+ non-Annotated

/// tip

Prefer to use the `Annotated` version if possible.

///

```Python hl_lines="1"
async def needy_dependency(fresh_value: str = Depends(get_value, use_cache=False)):

from typing import Union

from fastapi import FastAPI, Response
from fastapi.responses import RedirectResponse

app = FastAPI()


@app.get("/portal", response_model=None)
async def get_portal(teleport: bool = False) -> Union[Response, dict]:
    if teleport:
        return RedirectResponse(url="https://www.youtube.com/watch?v=dQw4w9WgXcQ")

    name: str
    description: Union[str, None] = None
    price: float
    tax: Union[float, None] = None
    tags: set[str] = set()


@app.post("/items/", response_model=Item, status_code=status.HTTP_201_CREATED)
async def create_item(item: Item):

Это обычная функция, которая может принимать параметры.

Это может быть как `async def`, так и обычная функция `def`, **FastAPI** знает, как корректно её выполнить.

В этом случае функция задачи будет записывать данные в файл (имитируя отправку письма).

Так как операция записи не использует `async` и `await`, мы определим функцию как обычную `def`:

{* ../../docs_src/background_tasks/tutorial001_py39.py hl[6:9] *}

    name: str
    description: Union[str, None] = None
    price: float
    tax: Union[float, None] = None
    tags: set[str] = set()
    image: Union[Image, None] = None


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