```

////

//// tab | Python 3.9+

```Python hl_lines="7  48  55-56  59-60  69-75"
{!> ../../docs_src/security/tutorial004_an_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="7  49  56-57  60-61  70-76"
{!> ../../docs_src/security/tutorial004_an.py!}
```

////

//// tab | Python 3.10+ nicht annotiert

/// tip | "Tipp"

//// tab | Python 3.10+

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

////

//// tab | 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

```

<details>
<summary>👀 Visualização completa do arquivo</summary>

```Python
{!> ../../docs_src/separate_openapi_schemas/tutorial001_py39.py!}
```

</details>

////

//// tab | Python 3.8+

```Python hl_lines="9"
{!> ../../docs_src/separate_openapi_schemas/tutorial001.py[ln:1-9]!}

# Code below omitted 👇
```

<details>
<summary>👀 Visualização completa do arquivo</summary>

```Python

```

////

//// tab | Python 3.8+

```Python hl_lines="23-28"
{!> ../../docs_src/schema_extra_example/tutorial003_an.py!}
```

////

//// tab | Python 3.10+ non-Annotated

/// tip

尽可能选择使用 `Annotated` 的版本。

///

```Python hl_lines="18-23"
{!> ../../docs_src/schema_extra_example/tutorial003_py310.py!}
```

////

//// tab | Python 3.8+ non-Annotated

/// tip

///

## Імпортуйте `BaseModel` від Pydantic

Спочатку вам потрібно імпортувати `BaseModel` з `pydantic`:

//// tab | Python 3.8 і вище

```Python hl_lines="4"
{!> ../../docs_src/body/tutorial001.py!}
```

////

//// tab | Python 3.10 і вище

```Python hl_lines="2"
{!> ../../docs_src/body/tutorial001_py310.py!}
```

//// tab | Python 3.10+

```Python hl_lines="1"
{!> ../../docs_src/python_types/tutorial009_py310.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="1  4"
{!> ../../docs_src/python_types/tutorial009.py!}
```

////

//// tab | Python 3.8+ বিকল্প

```Python hl_lines="1  4"
{!> ../../docs_src/python_types/tutorial009b.py!}
```

////

#### `Union` বা `Optional` ব্যবহার

```

////

//// tab | Python 3.9+

```Python hl_lines="8-11"
{!> ../../docs_src/dependencies/tutorial001_an_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="9-12"
{!> ../../docs_src/dependencies/tutorial001_an.py!}
```

////

//// tab | Python 3.10+ non-Annotated

/// tip | "Dica"

Utilize a versão com `Annotated` se possível.

//// tab | Python 3.9+

```Python
{!> ../../docs_src/security/tutorial001_an_py39.py!}
```

////

//// tab | Python 3.8+

```Python
{!> ../../docs_src/security/tutorial001_an.py!}
```

////

//// tab | Python 3.8+ non-Annotated

/// tip

Prefer to use the `Annotated` version if possible.

///

```Python
{!> ../../docs_src/security/tutorial001.py!}
```

```

<details>
<summary>👀 Vollständige Dateivorschau</summary>

```Python
{!> ../../docs_src/separate_openapi_schemas/tutorial001_py39.py!}
```

</details>

////

//// tab | Python 3.8+

```Python hl_lines="9"
{!> ../../docs_src/separate_openapi_schemas/tutorial001.py[ln:1-9]!}

# Code unterhalb weggelassen 👇
```

<details>
<summary>👀 Vollständige Dateivorschau</summary>

```Python

## 可选参数

同理，把默认值设为 `None` 即可声明**可选的**查询参数：

//// tab | Python 3.10+

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

////

//// tab | 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。