↩️ *➡ 🛠️* 🔬 ✔, 👆 💪 ⚒ 💭 👈 ➡ `/users/me` 📣 ⏭ 1️⃣ `/users/{user_id}`:

```Python hl_lines="6  11"
{!../../../docs_src/path_params/tutorial003.py!}
```

⏪, ➡ `/users/{user_id}` 🔜 🏏 `/users/me`, "💭" 👈 ⚫️ 📨 🔢 `user_id` ⏮️ 💲 `"me"`.

➡, 👆 🚫🔜 ↔ ➡ 🛠️:

```Python hl_lines="6  11"
{!../../../docs_src/path_params/tutorial003b.py!}
```

🥇 🕐 🔜 🕧 ⚙️ ↩️ ➡ 🏏 🥇.

## 🔁 💲

```Python hl_lines="6  11"
{!../../../docs_src/path_params/tutorial003.py!}
```

Otherwise, the path for `/users/{user_id}` would match also for `/users/me`, "thinking" that it's receiving a parameter `user_id` with a value of `"me"`.

Similarly, you cannot redefine a path operation:

```Python hl_lines="6  11"
{!../../../docs_src/path_params/tutorial003b.py!}
```

```Python hl_lines="6-7"
{!../../../docs_src/path_params/tutorial001.py!}
```

这段代码把路径参数 `item_id` 的值传递给路径函数的参数 `item_id`。

运行示例并访问 <a href="http://127.0.0.1:8000/items/foo" class="external-link" target="_blank">http://127.0.0.1:8000/items/foo</a>，可获得如下响应：

```JSON
{"item_id":"foo"}
```

## 声明路径参数的类型

使用 Python 标准类型注解，声明路径操作函数中路径参数的类型。

```Python hl_lines="7"