/// note | Hinweis

FastAPI erkennt, dass der Wert von `q` nicht erforderlich ist, aufgrund des Defaultwertes `= None`.

Die Verwendung von `str | None` ermöglicht es Ihrem Editor, Ihnen bessere Unterstützung zu bieten und Fehler zu erkennen.

///

## Zusätzliche Validierung { #additional-validation }

from fastapi import Depends, FastAPI

app = FastAPI()


class FixedContentQueryChecker:
    def __init__(self, fixed_content: str):
        self.fixed_content = fixed_content

    def __call__(self, q: str = ""):
        if q:
            return self.fixed_content in q
        return False


checker = FixedContentQueryChecker("bar")


@app.get("/query-checker/")

from typing import Annotated

from fastapi import FastAPI, Header
from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    model_config = {"extra": "forbid"}

    host: str
    save_data: bool
    if_modified_since: str | None = None
    traceparent: str | None = None
    x_tag: list[str] = []


@app.get("/items/")
async def read_items(headers: Annotated[CommonHeaders, Header()]):

from typing import Union

from fastapi import FastAPI, Header
from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    model_config = {"extra": "forbid"}

    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()):

from fastapi import FastAPI

app = FastAPI()


@app.get("/items/{item_id}")
async def read_item(item_id: str, q: str | None = None, short: bool = False):
    item = {"item_id": item_id}
    if q:
        item.update({"q": q})
    if not short:
        item.update(
            {"description": "This is an amazing item that has a long description"}
        )

from typing import Union

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


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


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

from typing import Annotated, Union

from fastapi import FastAPI, Header
from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    model_config = {"extra": "forbid"}

    host: str
    save_data: bool
    if_modified_since: Union[str, None] = None
    traceparent: Union[str, None] = None
    x_tag: list[str] = []


@app.get("/items/")

from typing import Annotated

from fastapi import FastAPI, Path, Query

app = FastAPI()


@app.get("/items/{item_id}")
async def read_items(
    item_id: Annotated[int, Path(title="The ID of the item to get")],
    q: Annotated[str | None, Query(alias="item-query")] = None,
):
    results = {"item_id": item_id}
    if q:
        results.update({"q": q})

from fastapi import FastAPI
from pydantic import BaseModel as BaseModelV2
from pydantic.v1 import BaseModel


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


class ItemV2(BaseModelV2):
    name: str
    description: str | None = None
    size: float


app = FastAPI()


@app.post("/items/", response_model=ItemV2)
async def create_item(item: Item):

except ImportError:  # pragma: no cover
    cli_main = None  # type: ignore


def main() -> None:
    if not cli_main:  # type: ignore[truthy-function]
        message = 'To use the fastapi command, please install "fastapi[standard]":\n\n\tpip install "fastapi[standard]"\n'
        print(message)
        raise RuntimeError(message)  # noqa: B904