```Python hl_lines="1  3"
    {!> ../../../docs_src/path_params_numeric_validations/tutorial001_an_py310.py!}
    ```

=== "Python 3.9+"

    ```Python hl_lines="1  3"
    {!> ../../../docs_src/path_params_numeric_validations/tutorial001_an_py39.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="3-4"
    {!> ../../../docs_src/path_params_numeric_validations/tutorial001_an.py!}
    ```

=== "Python 3.10+"

    ```Python hl_lines="17-19"
    {!> ../../../docs_src/body_multiple_params/tutorial001_py310.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="19-21"
    {!> ../../../docs_src/body_multiple_params/tutorial001.py!}
    ```

!!! note "Nota"

# 查询参数和字符串校验

**FastAPI** 允许你为参数声明额外的信息和校验。

让我们以下面的应用程序为例：

=== "Python 3.10+"

    ```Python hl_lines="7"
    {!> ../../../docs_src/query_params_str_validations/tutorial001_py310.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="9"
    {!> ../../../docs_src/query_params_str_validations/tutorial001.py!}
    ```

查询参数 `q` 的类型为 `str`，默认值为 `None`，因此它是可选的。

## 额外的校验

    return client


@needs_py310
def test_query_params_str_validations_no_query():
    client = get_client()
    response = client.get("/items/")
    assert response.status_code == 200
    assert response.json() == "Hello World"


@needs_py310
def test_query_params_str_validations_q_fixedquery():
    client = get_client()
    response = client.get("/items/", params={"q": "fixedquery"})
    assert response.status_code == 200

    ```Python hl_lines="10"
    {!> ../../../docs_src/query_params_str_validations/tutorial003_an_py310.py!}
    ```

=== "Python 3.9+"

    ```Python hl_lines="10"
    {!> ../../../docs_src/query_params_str_validations/tutorial003_an_py39.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="11"
    {!> ../../../docs_src/query_params_str_validations/tutorial003_an.py!}
    ```

    peer.acceptFrame() // SYN_REPLY
    peer.sendFrame().pushPromise(3, 2, headerEntries("b", "banana"))
    peer.acceptFrame() // RST_STREAM
    peer.play()

    // Play it back.
    val connection = connect(peer)
    connection.newStream(headerEntries("b", "banana"), false)

    // Verify the peer received what was expected.
    assertThat(peer.takeFrame().type).isEqualTo(Http2.TYPE_HEADERS)

                    NavigableMap<String, String> map = new SafeTreeMap<>();
                    putEntries(map, entries);
                    map.put("banana", "toast");
                    map.put("eggplant", "spam");
                    return Maps.filterKeys(map, FILTER_KEYS);
                  }
                })

```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 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!}
```

## 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。