For example you could have a file `main.py` with:

```Python hl_lines="3"
import os

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

!!! tip
    The second argument to <a href="https://docs.python.org/3.8/library/os.html#os.getenv" class="external-link" target="_blank">`os.getenv()`</a> is the default value to return.

这种做法相当常见，有一个名称，这些环境变量通常放在一个名为 `.env` 的文件中，该文件被称为“dotenv”。

!!! tip
    以点 (`.`) 开头的文件是 Unix-like 系统（如 Linux 和 macOS）中的隐藏文件。

    但是，dotenv 文件实际上不一定要具有确切的文件名。

Pydantic 支持使用外部库从这些类型的文件中读取。您可以在<a href="https://docs.pydantic.dev/latest/concepts/pydantic_settings/#dotenv-env-support" class="external-link" target="_blank">Pydantic 设置: Dotenv (.env) 支持</a>中阅读更多相关信息。

!!! tip

🖼 👆 💪 ✔️ 📁 `main.py` ⏮️:

```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> 🔢 💲 📨.

    🚥 🚫 🚚, ⚫️ `None` 🔢, 📥 👥 🚚 `"World"` 🔢 💲 ⚙️.

⤴️ 👆 💪 🤙 👈 🐍 📋:

// should be mirrored here.
func test1435(t *testing.T) {
	if syscall.Getuid() != 0 {
		t.Skip("skipping root only test")
	}
	if testing.Short() && testenv.Builder() != "" && os.Getenv("USER") == "swarming" {
		// The Go build system's swarming user is known not to be root.
		// Unfortunately, it sometimes appears as root due the current

        }
    }

    private static void downloadFileFromURL(String urlString, File destination) throws Exception {
        if (System.getenv("MVNW_USERNAME") != null && System.getenv("MVNW_PASSWORD") != null) {
            String username = System.getenv("MVNW_USERNAME");
            char[] password = System.getenv("MVNW_PASSWORD").toCharArray();
            Authenticator.setDefault(new Authenticator() {
                @Override

    val isCiServer = CI_ENVIRONMENT_VARIABLE in System.getenv()
    val isTravis = "TRAVIS" in System.getenv()
    val isGhActions = "GITHUB_ACTIONS" in System.getenv()
    val isTeamCity = "TEAMCITY_VERSION" in System.getenv()
    val isTeamCityParallelTestsEnabled
        get() = "TEAMCITY_PARALLEL_TESTS_ENABLED" in System.getenv()
    val isCodeQl: Boolean by lazy {

	ldflagsStr += " -X github.com/minio/minio/cmd.GOPATH=" + os.Getenv("GOPATH")
	ldflagsStr += " -X github.com/minio/minio/cmd.GOROOT=" + os.Getenv("GOROOT")
	return ldflagsStr
}

// genReleaseTag prints release tag to the console for easy git tagging.
func releaseTag(version string) (string, time.Time) {
	relPrefix := "DEVELOPMENT"
	if prefix := os.Getenv("MINIO_RELEASE"); prefix != "" {
		relPrefix = prefix
	}

			log.Printf("failed to ping sqlDB, got error %v", err)
			os.Exit(1)
		}

		RunMigrations()
	}
}

func OpenTestConnection(cfg *gorm.Config) (db *gorm.DB, err error) {
	dbDSN := os.Getenv("GORM_DSN")
	switch os.Getenv("GORM_DIALECT") {
	case "mysql":
		log.Println("testing mysql...")
		if dbDSN == "" {
			dbDSN = mysqlDSN
		}
		db, err = gorm.Open(mysql.Open(dbDSN), cfg)
	case "postgres":

	"context"
	"fmt"
	"log"
	"net/http"
	"os"

	cr "github.com/minio/minio-go/v7/pkg/credentials"
	cmd "github.com/minio/minio/cmd"
)

func main() {
	ctx := context.Background()

	endpoint := os.Getenv("MINIO_ENDPOINT")
	if endpoint == "" {
		log.Fatalf("Please specify a MinIO server endpoint environment variable like:\n\n\texport MINIO_ENDPOINT=http://localhost:9000")
	}

	appParams := cmd.OpenIDClientAppParams{

  __path__ = [_tf_api_dir]
elif _tf_api_dir not in __path__:
  __path__.append(_tf_api_dir)

# Hook external TensorFlow modules.

# Load tensorflow-io-gcs-filesystem if enabled
if (_os.getenv("TF_USE_MODULAR_FILESYSTEM", "0") == "true" or
    _os.getenv("TF_USE_MODULAR_FILESYSTEM", "0") == "1"):
  import tensorflow_io_gcs_filesystem as _tensorflow_io_gcs_filesystem

# Lazy-load Keras v2/3.
_tf_uses_legacy_keras = (