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

Im Hintergrund erstellt das `open("./somefile.txt")` ein Objekt, das als „Kontextmanager“ bezeichnet wird.

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

Por baixo dos panos, o código `open("./somefile.txt")` cria um objeto que é chamado de "Gerenciador de Contexto".

					continue
				}
				filteredGws = append(filteredGws, gw)
			}
			err = printWaypointStatus(ctx, w, kubeClient, filteredGws)
			if err != nil {
				return fmt.Errorf("failed to print waypoint status: %v", err)
			}
			return w.Flush()
		},
	}

	waypointGenerateCmd := &cobra.Command{
		Use:   "generate",
		Short: "Generate a waypoint configuration",

		consoleapi.TLSPort = globalMinioConsolePort
		consoleapi.Hostname = globalMinioConsoleHost
	}

	return server, nil
}

// Check for updates and print a notification message
func checkUpdate(mode string) {
	updateURL := minioReleaseInfoURL
	if runtime.GOOS == globalWindowsOSName {
		updateURL = minioReleaseWindowsInfoURL
	}

	u, err := url.Parse(updateURL)

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

Под капотом" open("./somefile.txt") создаёт объект называемый "контекстным менеджером".

Когда блок `with` завершается, он обязательно закрывает файл, даже если были исключения.

// explicitly by running a TPUReplicatedOutput operation on the parallel device.
//
// TODO(allenl): There are some use-cases that are only supported by copying to
// host at the moment (e.g. debug print on a tensor, .numpy(), etc.). We either
// need to return something here or address these use-cases one by one.
TFE_TensorHandle* CopyTensorFromParallelDevice(TFE_Context* context,

	if b != '\r' || err != nil {
		if cr.debug {
			fmt.Printf("want %q, got %q\n", "\r", string(b))
		}
		cr.err = errMalformedEncoding
		return n, cr.err
	}
	b, err = cr.reader.ReadByte()
	if err == io.EOF {
		err = io.ErrUnexpectedEOF
	}
	if err != nil {
		cr.err = err
		return n, cr.err
	}
	if b != '\n' {
		if cr.debug {
			fmt.Printf("want %q, got %q\n", "\r", string(b))
		}

!important;\n    display: inline-flex !important;\n  }\n}\n\n@media print {\n  .d-print-none {\n    display: none !important;\n  }\n  .d-print-inline {\n    display: inline !important;\n  }\n  .d-print-inline-block {\n    display: inline-block !important;\n  }\n  .d-print-block {\n    display: block !important;\n  }\n  .d-print-table {\n    display: table !important;\n  }\n  .d-print-table-row {\n    display: table-row !important;\n  }\n  .d-print-table-cell {\n    display: table-cell !important;\n  }\n  .d-print-flex...

デフォルトの例外ハンドラを`fastapi.exception_handlers`からインポートして再利用することができます:

```Python hl_lines="2 3 4 5 15 21"
{!../../docs_src/handling_errors/tutorial006.py!}
```

この例では、非常に表現力のあるメッセージでエラーを`print`しています。

////

### 在 Python 中读取环境变量

您还可以在 Python 之外的地方（例如终端中或使用任何其他方法）创建环境变量，然后在 Python 中读取它们。

例如，您可以有一个名为 `main.py` 的文件，其中包含以下内容：

```Python hl_lines="3"
import os

name = os.getenv("MY_NAME", "World")
print(f"Hello {name} from Python")
```

/// tip

<a href="https://docs.python.org/3.8/library/os.html#os.getenv" class="external-link" target="_blank">`os.getenv()`</a> 的第二个参数是要返回的默认值。