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: Annotated[CommonHeaders, Header()]):

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):

from typing import Annotated

from fastapi import APIRouter, Depends, FastAPI, WebSocket
from fastapi.testclient import TestClient


def dependency_list() -> list[str]:
    return []


DepList = Annotated[list[str], Depends(dependency_list)]


def create_dependency(name: str):
    def fun(deps: DepList):
        deps.append(name)

    return Depends(fun)


router = APIRouter(dependencies=[create_dependency("router")])

     * Encodes a wide string pointer in NDR format.
     *
     * @param buf the NDR buffer
     * @param str the string to encode (can be null)
     * @throws NdrException if encoding fails
     */
    private void encodeWideStringPointer(NdrBuffer buf, String str) throws NdrException {
        if (str == null || str.isEmpty()) {
            buf.enc_ndr_long(0); // NULL pointer
        } else {

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


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


class ItemV2(BaseModelV2):
    name: str
    description: Union[str, None] = None
    size: float


app = FastAPI()


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

from fastapi import FastAPI
from pydantic import BaseModel


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


app = FastAPI()


@app.post("/items/")
async def create_item(item: Item):

from dataclasses import dataclass

from fastapi import FastAPI


@dataclass
class Item:
    name: str
    price: float
    description: str | None = None
    tax: float | None = None


app = FastAPI()


@app.post("/items/")
async def create_item(item: Item):

    * Les clés de ce dictionnaire sont de type `str`.
    * Les valeurs de ce dictionnaire sont de type `float`.

#### `Optional`

Vous pouvez aussi utiliser `Optional` pour déclarer qu'une variable a un type, comme `str` mais qu'il est "optionnel" signifiant qu'il pourrait aussi être `None`.

{*../../docs_src/python_types/tutorial009.py hl[1,4] *}

        // Verify field initialization through toString
        String str = notifyChange.toString();
        assertTrue(str.contains("NtTransNotifyChange"));
        assertTrue(str.contains("fid=0x" + Hexdump.toHexString(fid, 4)));
        assertTrue(str.contains("filter=0x" + Hexdump.toHexString(completionFilter, 4)));
        assertTrue(str.contains("watchTree=" + watchTree));
    }

    @Test

```Python hl_lines="1  4"
{!../../docs_src/python_types/tutorial009.py!}
```

Використання `Optional[str]` замість просто `str` дозволить редактору допомогти вам виявити помилки, коли ви могли б вважати, що значенням завжди є `str`, хоча насправді воно також може бути `None`.

`Optional[Something]` насправді є скороченням для `Union[Something, None]`, вони еквівалентні.

Це також означає, що в Python 3.10 ви можете використовувати `Something | None`: