=== "Python 3.10+"

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

=== "Python 3.9+"

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

=== "Python 3.8+"

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

=== "Python 3.10+ nicht annotiert"

=== "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!}
    ```

Bu durumda, `q` fonksiyon parametresi isteğe bağlı olacak ve varsayılan değer olarak `None` alacaktır.

!!! check "Ek bilgi"

=== "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!}
    ```

In diesem Fall wird der Funktionsparameter `q` optional, und standardmäßig `None` sein.

!!! check

    {!> ../../../docs_src/query_params/tutorial006.py!}
    ```

=== "🐍 3️⃣.1️⃣0️⃣ & 🔛"

    ```Python hl_lines="8"
    {!> ../../../docs_src/query_params/tutorial006_py310.py!}
    ```

👉 💼, 📤 3️⃣ 🔢 🔢:

* `needy`, ✔ `str`.
* `skip`, `int` ⏮️ 🔢 💲 `0`.
* `limit`, 📦 `int`.

!!! tip

=== "Python 3.10+"

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

=== "Python 3.9+"

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

=== "Python 3.8+"

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

=== "Python 3.10+ non-Annotated"

    !!! tip

=== "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+ Annotated가 없는 경우"

    !!! tip "팁"

=== "Python 3.10+"

    ```Python hl_lines="7"
    {!> ../../../docs_src/header_params/tutorial003_py310.py!}
    ```

=== "Python 3.9+"

    ```Python hl_lines="9"
    {!> ../../../docs_src/header_params/tutorial003_py39.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="9"
    {!> ../../../docs_src/header_params/tutorial003.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。

```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="7"
    {!> ../../../docs_src/cookie_params/tutorial001_py310.py!}
    ```

=== "Python 3.8+"

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

!!! note "Технические детали"
    `Cookie` - это класс, родственный `Path` и `Query`. Он также наследуется от общего класса `Param`.