from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


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

    model_config = {
        "json_schema_extra": {
            "examples": [
                {
                    "name": "Foo",
                    "description": "A very nice Item",
                    "price": 35.4,

如果你要回傳的每個 JSON 項目型別都是 `Item`（一個 Pydantic 模型），而且該函式是 async，你可以將回傳型別宣告為 `AsyncIterable[Item]`：

{* ../../docs_src/stream_json_lines/tutorial001_py310.py ln[1:24] hl[9:11,22] *}

如果你宣告了回傳型別，FastAPI 會用它來進行資料的**驗證**、在 OpenAPI 中**文件化**、**過濾**，並使用 Pydantic 進行**序列化**。

/// tip

由於 Pydantic 會在 **Rust** 端進行序列化，宣告回傳型別可獲得比未宣告時高得多的**效能**。

///

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


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


@app.post(
    "/items/",
    summary="Create an item",
    description="Create an item with all the information, name, description, price, tax and a set of unique tags",
)

Dépendances optionnelles supplémentaires pour Pydantic :

* [`pydantic-settings`](https://docs.pydantic.dev/latest/usage/pydantic_settings/) - pour la gestion des paramètres.
* [`pydantic-extra-types`](https://docs.pydantic.dev/latest/usage/types/extra_types/extra_types/) - pour des types supplémentaires à utiliser avec Pydantic.

Dépendances optionnelles supplémentaires pour FastAPI :

from typing import Annotated

from fastapi import Body, FastAPI
from pydantic import BaseModel, Field

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = Field(
        default=None, title="The description of the item", max_length=300
    )
    price: float = Field(gt=0, description="The price must be greater than zero")
    tax: float | None = None


@app.put("/items/{item_id}")

from fastapi import FastAPI
from pydantic import BaseModel, HttpUrl

app = FastAPI()


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


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


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

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 fastapi import Cookie, FastAPI
from pydantic import BaseModel

app = FastAPI()


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

    session_id: str
    fatebook_tracker: str | None = None
    googall_tracker: str | None = None


@app.get("/items/")
async def read_items(cookies: Cookies = Cookie()):

from typing import Annotated

from fastapi import Cookie, FastAPI
from pydantic import BaseModel

app = FastAPI()


class Cookies(BaseModel):
    session_id: str
    fatebook_tracker: str | None = None
    googall_tracker: str | None = None


@app.get("/items/")
async def read_items(cookies: Annotated[Cookies, Cookie()]):

每个被 yield 的项会被编码为 JSON，并放入 SSE 事件的 `data:` 字段发送。

如果你将返回类型声明为 `AsyncIterable[Item]`，FastAPI 将使用它通过 Pydantic对数据进行**校验**、**文档化**和**序列化**。

{* ../../docs_src/server_sent_events/tutorial001_py310.py ln[1:25] hl[10:12,23] *}

/// tip | 提示

由于 Pydantic 会在**Rust** 端序列化它，相比未声明返回类型，你将获得更高的**性能**。

///

### 非 async 的*路径操作函数* { #non-async-path-operation-functions }