* <abbr title="Mozilla Developer Network: documentation for developers, written by the Firefox people">MDN</abbr>
* <abbr title="Input/Output: disk reading or writing, network communications.">I/O</abbr>.

////

//// tab | Info

"title" attributes of "abbr" elements are translated following some specific instructions.

«Контекстные менеджеры» — это любые объекты Python, которые можно использовать в операторе `with`.

Например, <a href="https://docs.python.org/3/tutorial/inputoutput.html#reading-and-writing-files" class="external-link" target="_blank">можно использовать `with` для чтения файла</a>:

```Python
with open("./somefile.txt") as f:
    contents = f.read()
    print(contents)
```

    editor.commit()
  }

  @Test
  fun `Windows cannot write while reading`() {
    Assumptions.assumeTrue(windows)

    set("k1", "a", "a")
    val snapshot = cache["k1"]!!
    assertThat(cache.edit("k1")).isNull()
    snapshot.close()
  }

  @Test
  fun `can read while reading`() {
    set("k1", "a", "a")
    cache["k1"]!!.use { snapshot1 ->

	req, err := c.newRequest(ctx, httpMethod, u, body)
	if err != nil {
		return nil, &NetworkError{Err: err}
	}
	if length > 0 {
		req.ContentLength = length
	}

	_, expectTimeouts := ctx.Deadline()

	req, update := setupReqStatsUpdate(req)
	defer update()

	resp, err := c.httpClient.Do(req)
	if err != nil {
		if xnet.IsNetworkOrHostDown(err, expectTimeouts) {
			if !c.NoMetrics {

„Kontextmanager“ (Englisch „Context Manager“) sind bestimmte Python-Objekte, die Sie in einer `with`-Anweisung verwenden können.

Beispielsweise können Sie <a href="https://docs.python.org/3/tutorial/inputoutput.html#reading-and-writing-files" class="external-link" target="_blank">`with` verwenden, um eine Datei auszulesen</a>:

```Python
with open("./somefile.txt") as f:
    contents = f.read()
    print(contents)
```

Na sobrescrita da dependência definimos um novo valor para `admin_email` ao criar o novo objeto `Settings`, e então retornamos esse novo objeto.

Depois podemos testar que ele é usado.

## Lendo um arquivo `.env` { #reading-a-env-file }

Se você tiver muitas configurações que possivelmente mudam bastante, talvez em diferentes ambientes, pode ser útil colocá-las em um arquivo e então lê-las como se fossem variáveis de ambiente.

		if s3Error != testCase.s3Error {
			if _, err := io.ReadAll(testCase.req.Body); toAPIErrorCode(ctx, err) != testCase.s3Error {
				t.Fatalf("Test %d: Unexpected S3 error: want %d - got %d (got after reading request %s)", i, testCase.s3Error, s3Error, toAPIError(ctx, err).Code)
			}
		}
	}
}

func TestCheckAdminRequestAuthType(t *testing.T) {
	ctx, cancel := context.WithCancel(t.Context())
	defer cancel()

		ContentType: mime.TypeByExtension(filepath.Ext(object)),
	}

	var rc io.ReadCloser

	if file.UncompressedSize64 > 0 {
		// There may be number of header bytes before the content.
		// Reading 64K extra. This should more than cover name and any "extra" details.
		end := min(file.Offset+int64(file.CompressedSize64)+64<<10, zipObjInfo.Size)
		rs := &HTTPRangeSpec{Start: file.Offset, End: end}

	if err != nil {
		return "", fmt.Errorf("request err: %v", err)
	}
	// {
	// 	bodyBuf, err := io.ReadAll(resp.Body)
	// 	if err != nil {
	// 		return "", fmt.Errorf("Error reading body: %v", err)
	// 	}
	// 	fmt.Printf("bodyBuf (for LDAP login page): %s\n", string(bodyBuf))
	// }

	// Fill the login form with our test creds:
	// fmt.Printf("login form url: %s\n", lastReq.URL.String())

## 上下文管理器

### 什么是"上下文管理器"

"上下文管理器"是你可以在 `with` 语句中使用的任何Python对象。

例如，<a href="https://docs.python.org/zh-cn/3/tutorial/inputoutput.html#reading-and-writing-files" class="external-link" target="_blank">你可以使用`with`读取文件</a>：

```Python
with open("./somefile.txt") as f:
    contents = f.read()
    print(contents)
```