Data from forms is normally encoded using the "media type" `application/x-www-form-urlencoded`.

But when the form includes files, it is encoded as `multipart/form-data`. You'll read about handling files in the next chapter.

    for (Field field : HttpHeaders.class.getDeclaredFields()) {
      /*
       * Coverage mode generates synthetic fields.  If we ever add private
       * fields, they will cause similar problems, and we may want to switch
       * this check to isAccessible().
       */
      if (!field.isSynthetic() && field.getType() == String.class) {
        builder.add(field);
      }
    }
    return builder.build();
  }

      // the result will definitely fit into a long
      long result = 1;
      for (int i = n1 + 1; i <= n2; i++) {
        result *= i;
      }
      return BigInteger.valueOf(result);
    }

    /*
     * We want each multiplication to have both sides with approximately the same number of digits.
     * Currently, we just divide the range in half.
     */
    int mid = (n1 + n2) >>> 1;

    return {"item_id": item_id, "q": q}
```

<details markdown="1">
<summary>Або використайте <code>async def</code>...</summary>

Якщо ваш код використовує `async` / `await`, скористайтеся `async def`:

```Python hl_lines="9  14"
from typing import Union

from fastapi import FastAPI

app = FastAPI()


@app.get("/")
async def read_root():

**FastAPI** 会创建一个 `BackgroundTasks` 类型的对象并作为该参数传入。

## 创建一个任务函数

创建要作为后台任务运行的函数。

它只是一个可以接收参数的标准函数。

它可以是 `async def` 或普通的 `def` 函数，**FastAPI** 知道如何正确处理。

在这种情况下，任务函数将写入一个文件（模拟发送电子邮件）。

由于写操作不使用 `async` 和 `await`，我们用普通的 `def` 定义函数：

{* ../../docs_src/background_tasks/tutorial001.py hl[6:9] *}

## 添加后台任务

在你的 *路径操作函数* 里，用 `.add_task()` 方法将任务函数传到 *后台任务* 对象中：

{* ../../docs_src/background_tasks/tutorial001.py hl[14] *}

			if w == nil {
				disks[i] = OfflineDisk
			}
		}
		if err == nil {
			if length := int64(len(data[test.offset:])); n != length {
				t.Errorf("Test %d: invalid number of bytes written: got: #%d want #%d", i, n, length)
			}
			writers := make([]io.Writer, len(disks))
			for i, disk := range disks {
				if disk == nil {
					continue
				}

为你需要检查的地方用标准的Python表达式写个简单的 `assert` 语句（重申，标准的`pytest`）。

{* ../../docs_src/app_testing/tutorial001.py hl[2,12,15:18] *}

/// tip | 提示

注意测试函数是普通的 `def`，不是 `async def`。

还有client的调用也是普通的调用，不是用 `await`。

这让你可以直接使用 `pytest` 而不会遇到麻烦。

///

/// note | 技术细节

你也可以用 `from starlette.testclient import TestClient`。

**FastAPI** 提供了和 `starlette.testclient` 一样的 `fastapi.testclient`，只是为了方便开发者。但它直接来自Starlette。

# renaming the wheels as uploading to PyPI would fail with "File already exists"
# error. In order to upload to PyPI, we unpack the wheel and change the tag
# inside a metadata file to the one we want (e.g cp38-cp38-win_amd) and then
# re-pack it to generate it as a platform specific wheel with this new wheel
#tag.
python3 -m wheel unpack "${pure_python_whl}"

# Remove the pure python wheel.
rm -rf "${pure_python_whl}"

{* ../../docs_src/app_testing/tutorial001_py39.py hl[2,12,15:18] *}

/// tip | Dica

Observe que as funções de teste são `def` normais, não `async def`.

E as chamadas para o cliente também são chamadas normais, não usando `await`.

Isso permite que você use `pytest` diretamente sem complicações.

///

/// note | Detalhes Técnicos

Você também pode usar `from starlette.testclient import TestClient`.

Mais vous pouvez retourner une `JSONResponse` directement à partir de vos *opérations de chemin*.

Cela peut être utile, par exemple, pour retourner des en-têtes personnalisés ou des cookies.

## Renvoyer une `Response`

En fait, vous pouvez retourner n'importe quelle `Response` ou n'importe quelle sous-classe de celle-ci.

/// note | Remarque

`JSONResponse` est elle-même une sous-classe de `Response`.

///