separate_input_output_schemas = request.param
    app = FastAPI(separate_input_output_schemas=separate_input_output_schemas)

    from pydantic import BaseModel, computed_field

    class Rectangle(BaseModel):
        width: int
        length: int

        @computed_field
        @property
        def area(self) -> int:
            return self.width * self.length

    @app.get("/")
    def read_root() -> Rectangle:

### Create it { #create-it }

Create a file `main.py` with:

```Python
from typing import Union

from fastapi import FastAPI

app = FastAPI()


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}
```

<details markdown="1">

from typing import Annotated

from fastapi import FastAPI, File, UploadFile

app = FastAPI()


@app.post("/files/")
async def create_file(file: Annotated[bytes, File(description="A file read as bytes")]):
    return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(
    file: Annotated[UploadFile, File(description="A file read as UploadFile")],
):

これが「*パスオペレーションデコレータ*」です。

///

他のオペレーションも使用できます:

* `@app.post()`
* `@app.put()`
* `@app.delete()`

また、よりエキゾチックなものも使用できます:

* `@app.options()`
* `@app.head()`
* `@app.patch()`
* `@app.trace()`

/// tip | 豆知識

各オペレーション (HTTPメソッド)は自由に使用できます。

**FastAPI**は特定の意味づけを強制しません。

ここでの情報は、要件ではなくガイドラインとして提示されます。

from fastapi.testclient import TestClient
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",
    response_class=Response,

from typing import Optional

from fastapi import FastAPI, Security
from fastapi.security import HTTPAuthorizationCredentials, HTTPBearer
from fastapi.testclient import TestClient

app = FastAPI()

security = HTTPBearer(auto_error=False)


@app.get("/users/me")
def read_current_user(
    credentials: Optional[HTTPAuthorizationCredentials] = Security(security),
):
    if credentials is None:

from fastapi.testclient import TestClient

app = FastAPI()

oauth2_scheme = OAuth2AuthorizationCodeBearer(
    authorizationUrl="authorize",
    tokenUrl="token",
    description="OAuth2 Code Bearer",
    auto_error=True,
)


@app.get("/items/")
async def read_items(token: Optional[str] = Security(oauth2_scheme)):
    return {"token": token}


client = TestClient(app)


def test_no_token():

from fastapi.testclient import TestClient

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/token", auto_error=False)


@app.get("/items/")
async def read_items(token: Optional[str] = Security(oauth2_scheme)):
    if token is None:
        return {"msg": "Create an account first"}
    return {"token": token}


client = TestClient(app)


def test_no_token():

import pytest
from fastapi import FastAPI
from fastapi.testclient import TestClient


@pytest.fixture(name="app", scope="module")
def get_app():
    with pytest.warns(DeprecationWarning):
        from docs_src.events.tutorial001_py39 import app
    yield app


def test_events(app: FastAPI):
    with TestClient(app) as client:
        response = client.get("/items/foo")
        assert response.status_code == 200, response.text

from starlette.testclient import TestClient

app = FastAPI()


class Item(BaseModel):
    name: str = Field(alias="aliased_name")
    price: Optional[float] = None
    owner_ids: Optional[list[int]] = None


@app.get("/items/valid", response_model=Item)
def get_valid():
    return Item(aliased_name="valid", price=1.0)


@app.get("/items/coerce", response_model=Item)
def get_coerce():