```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}
```

### 도커파일

이제 같은 프로젝트 디렉터리에 다음과 같은 파일 `Dockerfile`을 생성합니다:

```{ .dockerfile .annotate }
# (1)

使い方はとても簡単です。例えば、`GET`リクエストを実行するには、このように書けば良いです:

```Python
response = requests.get("http://example.com/some/url")
```

対応するFastAPIのパスオペレーションはこのようになります:

```Python hl_lines="1"
@app.get("/some/url")
def read_url():
    return {"message": "Hello World"}
```

 `requests.get(...)` と`@app.get(...)` には類似点が見受けられます。

!!! check "**FastAPI**へ与えたインスピレーション"
    * シンプルで直感的なAPIを持っている点。
    * HTTPメソッド名を直接利用し、単純で直感的である。

# Custom Response - HTML, Stream, File, others

By default, **FastAPI** will return the responses using `JSONResponse`.

You can override it by returning a `Response` directly as seen in [Return a Response directly](response-directly.md){.internal-link target=_blank}.

    tasks.add_task(bg, state)
    return state


# Sync versions


@app.get("/sync_async")
def get_sync_async(state: str = Depends(asyncgen_state)):
    return state


@app.get("/sync_sync")
def get_sync_sync(state: str = Depends(generator_state)):
    return state


@app.get("/sync_async_raise")

    return JSONResponse(None, headers={"x-fastapi-item-id": item_id})


@app.options("/items/{item_id}")
def options_item(item_id: str):
    return JSONResponse(None, headers={"x-fastapi-item-id": item_id})


@app.patch("/items/{item_id}")
def patch_item(item_id: str, item: Item):
    return {"item_id": item_id, "item": item}


@app.trace("/items/{item_id}")
def trace_item(item_id: str):

            It defaults to [swagger_ui_default_parameters][fastapi.openapi.docs.swagger_ui_default_parameters].
            """
        ),
    ] = None,
) -> HTMLResponse:
    """
    Generate and return the HTML  that loads Swagger UI for the interactive
    API docs (normally served at `/docs`).

    You would only call this function yourself if you needed to override some parts,

@user_router.get("/")
def get_users():
    return [{"user_id": "u1"}, {"user_id": "u2"}]


@user_router.get("/{user_id}")
def get_user(user_id: str):
    return {"user_id": user_id}


@item_router.get("/")
def get_items(user_id: Optional[str] = None):
    if user_id is None:
        return [{"item_id": "i1", "user_id": "u1"}, {"item_id": "i2", "user_id": "u2"}]
    else:
        return [{"item_id": "i2", "user_id": user_id}]

    if oauth_header is None:
        return None
    user = User(username=oauth_header)
    return user


@app.post("/login")
def login(form_data: OAuth2PasswordRequestFormStrict = Depends()):
    return form_data


@app.get("/users/me")
def read_users_me(current_user: Optional[User] = Depends(get_current_user)):
    if current_user is None:
        return {"msg": "Create an account first"}
    return current_user

## Return the token

The response of the `token` endpoint must be a JSON object.

It should have a `token_type`. In our case, as we are using "Bearer" tokens, the token type should be "`bearer`".

And it should have an `access_token`, with a string containing our access token.

For this simple example, we are going to just be completely insecure and return the same `username` as the token.

    is_offer: Union[bool, None] = None


@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}


@app.put("/items/{item_id}")
def update_item(item_id: int, item: Item):
    return {"item_name": item.name, "item_id": item_id}
```