```Python hl_lines="16"
{!../../../docs_src/path_params/tutorial005.py!}
```

### Documentation

Les valeurs disponibles pour le *paramètre de chemin* sont bien prédéfinies, la documentation les affiche correctement :

<img src="/img/tutorial/path-params/image03.png">

### Manipuler les *énumérations* Python

        final Map<String, Object> paramMap = new HashMap<>();
        paramMap.put("param1", "PARAM1");
        paramMap.put("param2", "PARAM2+");
        paramMap.put("param3", "PARAM3*");

        value = "\"abc\"";
        assertEquals("abc", dataStore.convertValue(Constants.DEFAULT_SCRIPT, value, paramMap));

        value = "param1";
        assertEquals("PARAM1", dataStore.convertValue(Constants.DEFAULT_SCRIPT, value, paramMap));

	return tok
}

func (p *Parser) back() {
	if p.inputPos == 0 {
		p.errorf("internal error: backing up before BOL")
	} else {
		p.inputPos--
	}
}

func (p *Parser) peek() lex.ScanToken {
	if p.more() {
		return p.input[p.inputPos].ScanToken
	}
	return scanner.EOF
}

func (p *Parser) more() bool {
	return p.inputPos < len(p.input)
}

## 可选参数

同理，把默认值设为 `None` 即可声明**可选的**查询参数：

=== "Python 3.10+"

    ```Python hl_lines="7"
    {!> ../../../docs_src/query_params/tutorial002_py310.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="9"
    {!> ../../../docs_src/query_params/tutorial002.py!}
    ```


本例中，查询参数 `q` 是可选的，默认值为 `None`。

!!! check "检查"

    注意，**FastAPI** 可以识别出 `item_id` 是路径参数，`q` 不是路径参数，而是查询参数。

```Python hl_lines="16"
{!../../../docs_src/path_params/tutorial005.py!}
```

### ✅ 🩺

↩️ 💪 💲 *➡ 🔢* 🔢, 🎓 🩺 💪 🎦 👫 🎆:

<img src="/img/tutorial/path-params/image03.png">

### 👷 ⏮️ 🐍 *🔢*

💲 *➡ 🔢* 🔜 *🔢 👨‍🎓*.

#### 🔬 *🔢 👨‍🎓*

👆 💪 🔬 ⚫️ ⏮️ *🔢 👨‍🎓* 👆 ✍ 🔢 `ModelName`:

```Python hl_lines="17"
{!../../../docs_src/path_params/tutorial005.py!}
```

#### 🤚 *🔢 💲*

=== "Python 3.10+"

    ```Python hl_lines="3"
    {!> ../../../docs_src/cookie_params/tutorial001_an_py310.py!}
    ```

=== "Python 3.9+"

    ```Python hl_lines="3"
    {!> ../../../docs_src/cookie_params/tutorial001_an_py39.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="3"
    {!> ../../../docs_src/cookie_params/tutorial001_an.py!}
    ```

=== "Python 3.10+ non-Annotated"

    !!! tip

```Python hl_lines="8  10"
{!../../../docs_src/query_params/tutorial004.py!}
```

## 필수 쿼리 매개변수

경로가 아닌 매개변수에 대한 기본값을 선언할 때(지금은 쿼리 매개변수만 보았습니다), 해당 매개변수는 필수적(Required)이지 않았습니다.

특정값을 추가하지 않고 선택적으로 만들기 위해선 기본값을 `None`으로 설정하면 됩니다.

그러나 쿼리 매개변수를 필수로 만들려면 단순히 기본값을 선언하지 않으면 됩니다:

```Python hl_lines="6-7"
{!../../../docs_src/query_params/tutorial005.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  11"
{!../../../docs_src/path_params/tutorial003.py!}
```

Иначе путь для `/users/{user_id}` также будет соответствовать `/users/me`, "подразумевая", что он получает параметр `user_id` со значением `"me"`.

Аналогично, вы не можете переопределить операцию с путем:

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

```Python hl_lines="16"
{!../../../docs_src/path_params/tutorial005.py!}
```

### 查看文档

 API 文档会显示预定义*路径参数*的可用值：

<img src="/img/tutorial/path-params/image03.png">

### 使用 Python _枚举类型_

*路径参数*的值是枚举的元素。

#### 比较*枚举元素*

枚举类 `ModelName` 中的*枚举元素*支持比较操作：

```Python hl_lines="17"
{!../../../docs_src/path_params/tutorial005.py!}
```

#### 获取*枚举值*