//// tab | Python 3.10+

```Python hl_lines="22-29"
{!> ../../docs_src/schema_extra_example/tutorial003_an_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="22-29"
{!> ../../docs_src/schema_extra_example/tutorial003_an_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="23-30"

//// tab | Python 3.10+

```Python hl_lines="16  21"
{!> ../../docs_src/response_model/tutorial001_01_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="18  23"
{!> ../../docs_src/response_model/tutorial001_01_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="18  23"

这不是 **FastAPI** 的问题，而是 HTTP 协议的规定。

///

## 可选文件上传

您可以通过使用标准类型注解并将 None 作为默认值的方式将一个文件参数设为可选:

//// tab | Python 3.9+

```Python hl_lines="7  14"
{!> ../../docs_src/request_files/tutorial001_02_py310.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="9  17"

//// tab | Python 3.10+

```Python hl_lines="16  21"
{!> ../../docs_src/response_model/tutorial001_01_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="18  23"
{!> ../../docs_src/response_model/tutorial001_01_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="18  23"

Beachten Sie, dass wir jetzt keine Standardinstanz `settings = Settings()` erstellen.

### Die Haupt-Anwendungsdatei

Jetzt erstellen wir eine Abhängigkeit, die ein neues `config.Settings()` zurückgibt.

//// tab | Python 3.9+

```Python hl_lines="6  12-13"
{!> ../../docs_src/settings/app02_an_py39/main.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="6  12-13"

	_ = x[HandlerLoadPolicyMapping-33]
	_ = x[HandlerDeleteServiceAccount-34]
	_ = x[HandlerLoadServiceAccount-35]
	_ = x[HandlerDeleteUser-36]
	_ = x[HandlerLoadUser-37]
	_ = x[HandlerLoadGroup-38]
	_ = x[HandlerHealBucket-39]
	_ = x[HandlerMakeBucket-40]
	_ = x[HandlerHeadBucket-41]
	_ = x[HandlerDeleteBucket-42]
	_ = x[HandlerGetMetrics-43]
	_ = x[HandlerGetResourceMetrics-44]
	_ = x[HandlerGetMemInfo-45]
	_ = x[HandlerGetProcInfo-46]

```Python hl_lines="1  14-15  18-20  33"
{!> ../../docs_src/extra_models/tutorial003.py!}
```

////

## 模型列表

使用同样的方式也可以声明由对象列表构成的响应。

为此，请使用标准的 Python `typing.List`：

//// tab | Python 3.9+

```Python hl_lines="18"
{!> ../../docs_src/extra_models/tutorial004_py39.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="1  20"
{!> ../../docs_src/extra_models/tutorial004.py!}

## 导入 Path

首先，从 `fastapi` 导入 `Path`：

//// tab | Python 3.10+

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

////

//// tab | Python 3.9+

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

////

//// tab | Python 3.8+

```Python hl_lines="3-4"

```

Notice that now we don't create a default instance `settings = Settings()`.

### The main app file

Now we create a dependency that returns a new `config.Settings()`.

//// tab | Python 3.9+

```Python hl_lines="6  12-13"
{!> ../../docs_src/settings/app02_an_py39/main.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="6  12-13"

//// tab | Python 3.10+

```Python hl_lines="1  4-6  9-10  21-22  25-26"
{!> ../../docs_src/sql_databases/sql_app_py310/schemas.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="3  6-8  11-12  23-24  27-28"
{!> ../../docs_src/sql_databases/sql_app_py39/schemas.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="3  6-8  11-12  23-24  27-28"