## Run it { #run-it }

/// info

The [`python-multipart`](https://github.com/Kludex/python-multipart) package is automatically installed with **FastAPI** when you run the `pip install "fastapi[standard]"` command.

However, if you use the `pip install fastapi` command, the `python-multipart` package is not included by default.

각각의 독립적인 OpenAPI와 문서 UI를 갖는 두 개의 독립적인 FastAPI 애플리케이션이 필요하다면, 메인 앱을 두고 하나(또는 그 이상)의 하위 애플리케이션을 "마운트"할 수 있습니다.

## **FastAPI** 애플리케이션 마운트 { #mounting-a-fastapi-application }

"마운트"란 완전히 "독립적인" 애플리케이션을 특정 경로에 추가하고, 그 하위 애플리케이션에 선언된 _경로 처리_로 해당 경로 아래의 모든 것을 처리하도록 하는 것을 의미합니다.

### 최상위 애플리케이션 { #top-level-application }

먼저, 메인 최상위 **FastAPI** 애플리케이션과 그 *경로 처리*를 생성합니다:

**FastAPI** 使用 [OpenAPI](https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.1.0.md) 生成概图，所以能兼容很多工具。

因此，**FastAPI** 还内置了 ReDoc 生成的备选 API 文档，可在此查看 [http://127.0.0.1:8000/redoc](http://127.0.0.1:8000/redoc)：

<img src="/img/tutorial/path-params/image02.png">

同样，还有很多兼容工具，包括多种语言的代码生成工具。

## Pydantic { #pydantic }

### FastAPI Data Filtering { #fastapi-data-filtering }

Now, for FastAPI, it will see the return type and make sure that what you return includes **only** the fields that are declared in the type.

**FastAPI** has its own `HTTPException`.

And **FastAPI**'s `HTTPException` error class inherits from Starlette's `HTTPException` error class.

The only difference is that **FastAPI**'s `HTTPException` accepts any JSON-able data for the `detail` field, while Starlette's `HTTPException` only accepts strings for it.

So, you can keep raising **FastAPI**'s `HTTPException` as normally in your code.

from contextlib import asynccontextmanager

from fastapi import FastAPI
from fastapi.testclient import TestClient

items = {}


@asynccontextmanager
async def lifespan(app: FastAPI):
    items["foo"] = {"name": "Fighters"}
    items["bar"] = {"name": "Tenders"}
    yield
    # clean up items
    items.clear()


app = FastAPI(lifespan=lifespan)


@app.get("/items/{item_id}")
async def read_items(item_id: str):

from collections.abc import AsyncIterable, Iterable

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None


items = [
    Item(name="Plumbus", description="A multi-purpose household device."),
    Item(name="Portal Gun", description="A portal opening device."),
    Item(name="Meeseeks Box", description="A box that summons a Meeseeks."),
]

from fastapi import FastAPI
from fastapi.responses import FileResponse

some_file_path = "large-video-file.mp4"
app = FastAPI()


@app.get("/")
async def main():

# 設定 Swagger UI { #configure-swagger-ui }

你可以設定一些額外的 [Swagger UI 參數](https://swagger.io/docs/open-source-tools/swagger-ui/usage/configuration/)。

要設定它們，建立 `FastAPI()` 應用物件時，或呼叫 `get_swagger_ui_html()` 函式時，傳入參數 `swagger_ui_parameters`。

`swagger_ui_parameters` 接受一個 dict，內容會直接傳給 Swagger UI 作為設定。

FastAPI 會把這些設定轉換成 **JSON**，以便與 JavaScript 相容，因為 Swagger UI 需要的是這種格式。

## 停用語法醒目提示 { #disable-syntax-highlighting }

from fastapi import FastAPI
from fastapi.responses import FileResponse

some_file_path = "large-video-file.mp4"
app = FastAPI()


@app.get("/", response_class=FileResponse)
async def main():