```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">
<summary>或可以使用 <code>async def</code>...</summary>

如果你的程式使用 `async` / `await`，請使用 `async def`：

```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">
<summary>Or use <code>async def</code>...</summary>

{!../../docs_src/bigger_applications/app/routers/items.py!}
```

➡ 🔠 *➡ 🛠️* ✔️ ▶️ ⏮️ `/`, 💖:

```Python hl_lines="1"
@router.get("/{item_id}")
async def read_item(item_id: str):
    ...
```

...🔡 🔜 🚫 🔌 🏁 `/`.

, 🔡 👉 💼 `/items`.

👥 💪 🚮 📇 `tags` & ➕ `responses` 👈 🔜 ✔ 🌐 *➡ 🛠️* 🔌 👉 📻.

{!../../docs_src/bigger_applications/app/routers/items.py!}
```

As the path of each *path operation* has to start with `/`, like in:

```Python hl_lines="1"
@router.get("/{item_id}")
async def read_item(item_id: str):
    ...
```

...the prefix must not include a final `/`.

So, the prefix in this case is `/items`.

```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}
```

### 📁

🔜 🎏 🏗 📁 ✍ 📁 `Dockerfile` ⏮️:

```{ .dockerfile .annotate }
# (1)
FROM python:3.9

{!../../docs_src/bigger_applications/app/routers/items.py!}
```

Da der Pfad jeder *Pfadoperation* mit `/` beginnen muss, wie in:

```Python hl_lines="1"
@router.get("/{item_id}")
async def read_item(item_id: str):
    ...
```

... darf das Präfix kein abschließendes `/` enthalten.

Das Präfix lautet in diesem Fall also `/items`.

{!../../docs_src/bigger_applications/app/routers/items.py!}
```

Como o caminho de cada *operação de rota* deve começar com `/`, como em:

```Python hl_lines="1"
@router.get("/{item_id}")
async def read_item(item_id: str):
    ...
```

...o prefixo não deve incluir um `/` final.

Então, o prefixo neste caso é `/items`.

{!../../docs_src/bigger_applications/app/routers/items.py!}
```

由于每个*路径操作*的路径都必须以 `/` 开头，例如：

```Python hl_lines="1"
@router.get("/{item_id}")
async def read_item(item_id: str):
    ...
```

...前缀不能以 `/` 作为结尾。

因此，本例中的前缀为 `/items`。

我们还可以添加一个 `tags` 列表和额外的 `responses` 列表，这些参数将应用于此路由器中包含的所有*路径操作*。

```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}
```

### Dockerfile

Now in the same project directory create a file `Dockerfile` with:

```{ .dockerfile .annotate }

```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}
```

### Dockerfile

В этой же директории создайте файл `Dockerfile` и заполните его:

```{ .dockerfile .annotate }