var (
	mysqlDSN     = "gorm:gorm@tcp(localhost:9910)/gorm?charset=utf8&parseTime=True&loc=Local"
	postgresDSN  = "user=gorm password=gorm dbname=gorm host=localhost port=9920 sslmode=disable TimeZone=Asia/Shanghai"
	gaussdbDSN   = "user=gaussdb password=Gaussdb@123 dbname=gorm host=localhost port=9950 sslmode=disable TimeZone=Asia/Shanghai"
	sqlserverDSN = "sqlserver://sa:LoremIpsum86@localhost:9930?database=master"

```

</div>

then the internal variable `__name__` in your file, created automatically by Python, will have as value the string `"__main__"`.

So, the section:

```Python
    uvicorn.run(app, host="0.0.0.0", port=8000)
```

will run.

---

This won't happen if you import that module (file).

So, if you have another file `importer.py` with:

```Python
from myapp import app

# Some more code
```

Angenommen, Sie haben ein Frontend, das in Ihrem Browser unter `http://localhost:8080` läuft, und dessen JavaScript versucht, mit einem Backend zu kommunizieren, das unter `http://localhost` läuft (da wir keinen Port angegeben haben, geht der Browser vom Default-Port `80` aus).

const (
	defaultTTL            = 30
	defaultContextTimeout = 5 * time.Minute
)

// SrvRecord - represents a DNS service record
type SrvRecord struct {
	Host     string      `json:"host,omitempty"`
	Port     json.Number `json:"port,omitempty"`
	Priority int         `json:"priority,omitempty"`
	Weight   int         `json:"weight,omitempty"`
	Text     string      `json:"text,omitempty"`

</div>

dann hat in Ihrer Datei die interne Variable `__name__`, die von Python automatisch erstellt wird, als Wert den String `"__main__"`.

Daher wird der Abschnitt:

```Python
    uvicorn.run(app, host="0.0.0.0", port=8000)
```

ausgeführt.

---

Dies wird nicht passieren, wenn Sie das Modul (die Datei) importieren.

Wenn Sie also eine weitere Datei `importer.py` mit folgendem Inhalt haben:

```Python

		baseDialCtx = (&net.Dialer{
			Timeout:   30 * time.Second,
			KeepAlive: 30 * time.Second,
		}).DialContext
	}

	return func(ctx context.Context, network, addr string) (conn net.Conn, err error) {
		host, port, err := net.SplitHostPort(addr)
		if err != nil {
			return nil, err
		}

		if net.ParseIP(host) != nil {
			// For IP only setups there is no need for DNS lookups.
			return baseDialCtx(ctx, "tcp", addr)
		}

	Bucket          Bucket `json:"bucket"`
	Object          Object `json:"object"`
}

// Source represents client information who triggered the event.
type Source struct {
	Host      string `json:"host"`
	Port      string `json:"port"`
	UserAgent string `json:"userAgent"`
}

// Event represents event notification information defined in
// http://docs.aws.amazon.com/AmazonS3/latest/dev/notification-content-structure.html.
type Event struct {

	if errors.Is(err, syscall.EADDRINUSE) {
		return ErrPortAlreadyInUse(err).Msg("Specified port is already in use")
	} else if errors.Is(err, syscall.EACCES) || errors.Is(err, syscall.EPERM) {
		if netErr, ok := err.(*net.OpError); ok {
			return ErrPortAccess(netErr).Msg("Insufficient permissions to use specified port")
		}
	}

	// Failed to identify what type of error this, return a simple UI error

		store:      queueStore,
		cancel:     cancel,
		cancelCh:   ctx.Done(),
	}

	// Calculate the webhook addr with the port number format
	target.addr = args.Endpoint.Host
	if _, _, err := net.SplitHostPort(args.Endpoint.Host); err != nil && strings.Contains(err.Error(), "missing port in address") {
		switch strings.ToLower(args.Endpoint.Scheme) {
		case "http":
			target.addr += ":80"
		case "https":

所以，下面这部分代码才会运行：

```Python
    uvicorn.run(app, host="0.0.0.0", port=8000)
```

---

如果你是导入这个模块（文件）就不会这样。

因此，如果你的另一个文件 `importer.py` 像这样：

```Python
from myapp import app

# Some more code
```

在这种情况下，`myapp.py` 内部的自动变量不会有值为 `"__main__"` 的变量 `__name__`。

所以，下面这一行不会被执行：

```Python
    uvicorn.run(app, host="0.0.0.0", port=8000)
```

/// info