}

app = FastAPI()


class Item(BaseModel):
    id: str
    title: str
    description: Union[str, None] = None


@app.get("/items/{item_id}", response_model=Item)
async def read_main(item_id: str, x_token: Annotated[str, Header()]):
    if x_token != fake_secret_token:
        raise HTTPException(status_code=400, detail="Invalid X-Token header")

from fastapi import FastAPI
from fastapi.testclient import TestClient
from pydantic import BaseModel


class Model1(BaseModel):
    foo: str
    bar: str


class Model2(BaseModel):
    ref: Model1
    baz: str


class Model3(BaseModel):
    name: str
    age: int
    ref2: Model2


app = FastAPI()


@app.get(
    "/simple_include",
    response_model=Model2,

|------------|------|-------------|
| `title` | `str` | O título da API. |
| `summary` | `str` | Um breve resumo da API. <small>Disponível desde OpenAPI 3.1.0, FastAPI 0.99.0.</small> |
| `description` | `str` | Uma breve descrição da API. Pode usar Markdown. |
| `version` | `string` | A versão da API. Esta é a versão da sua aplicação, não do OpenAPI. Por exemplo, `2.5.0`. |

                    buf.append(", ");
                }
                buf.append(Array.get(obj, i));
            }
            buf.append(']');
            str = buf.toString();
        } else {
            str = String.valueOf(obj);
        }
        return str;
    }

{!../../docs_src/python_types/tutorial009.py!}
```

`str` yerine `Optional[str]` kullanmak editorün bu değerin her zaman `str` tipinde değil bazen `None` tipinde de olabileceğini belirtir ve hataları tespit etmemizde yardımcı olur.

#### Generic tipler

Köşeli parantez içinde tip parametreleri alan bu türler, örneğin:

* `List`
* `Tuple`
* `Set`
* `Dict`
* `Optional`
* ...and others.

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class Image(BaseModel):
    url: str
    name: str


class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None
    tags: set[str] = set()
    image: Image | None = None


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

from starlette.exceptions import WebSocketException as StarletteWebSocketException


class EndpointContext(TypedDict, total=False):
    function: str
    path: str
    file: str
    line: int


class HTTPException(StarletteHTTPException):
    """
    An HTTP exception you can raise in your own code to show errors to the client.

    app = FastAPI()

    class ModelB(BaseModel):
        username: str

    class ModelC(ModelB):
        password: str

    class ModelA(BaseModel):
        name: str
        description: Optional[str] = None
        foo: ModelB
        tags: dict[str, str] = {}

        @field_validator("name")
        def lower_username(cls, name: str, info: ValidationInfo):
            if not name.endswith("A"):

from pydantic import BaseModel

app = FastAPI()


class JsonApiResponse(JSONResponse):
    media_type = "application/vnd.api+json"


class Error(BaseModel):
    status: str
    title: str


class JsonApiError(BaseModel):
    errors: list[Error]


@app.get(
    "/a/{id}",
    response_class=JsonApiResponse,
    responses={422: {"description": "Error", "model": JsonApiError}},
)

from fastapi.testclient import TestClient
from pydantic import BaseModel

app = FastAPI()

api_key = APIKeyHeader(name="key", auto_error=False)


class User(BaseModel):
    username: str


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


@app.get("/users/me")