////

## 在 Python 中讀取環境變數

你也可以在 Python **之外**的終端機中建立環境變數（或使用其他方法），然後在 Python 中**讀取**它們。

例如，你可以建立一個名為 `main.py` 的檔案，其中包含以下內容：

```Python hl_lines="3"
import os

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

/// tip

第二個參數是 <a href="https://docs.python.org/zh-tw/3.8/library/os.html#os.getenv" class="external-link" target="_blank">`os.getenv()`</a> 的預設回傳值。

        Exception exception = new Exception() {
            @Override
            public void printStackTrace(java.io.PrintWriter writer) {
                // Simulate a normal stack trace output
                writer.println("Special test exception");
                writer.flush();
            }
        };

        monitorTarget.appendException(buf, exception);
        assertTrue(buf.toString().contains("Special test exception"));

        final CmdLineParser parser = new CmdLineParser(options);
        try {
            parser.parseArgument(args);
        } catch (final CmdLineException e) {
            System.err.println(e.getMessage());
            System.err.println("java " + Crawler.class.getCanonicalName() + " [options...] arguments...");
            parser.printUsage(System.err);
            return;
        }

        if (logger.isDebugEnabled()) {

</div>

////

### ✍ 🇨🇻 {🐍

👆 💪 ✍ 🌐 🔢 🏞 🐍, 📶 (⚖️ ⏮️ 🙆 🎏 👩‍🔬), &amp; ⤴️ ✍ 👫 🐍.

🖼 👆 💪 ✔️ 📁 `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> 🔢 💲 📨.

  private static final Escaper XML_ATTRIBUTE_ESCAPER;

  static {
    Escapers.Builder builder = Escapers.builder();
    // The char values \uFFFE and \uFFFF are explicitly not allowed in XML
    // (Unicode code points above \uFFFF are represented via surrogate pairs
    // which means they are treated as pairs of safe characters).
    builder.setSafeRange(Character.MIN_VALUE, '\uFFFD');

2018/12/26 17:49:36 listening on http://localhost:8888/
```

This will open the login page of keycloak, upon successful login, STS credentials along with any buckets discovered using the credentials will be printed on the screen, for example:

```
{
  "buckets": [
    "bucket-x"
  ],
  "credentials": {
    "AccessKeyID": "6N2BALX7ELO827DXS3GK",
    "SecretAccessKey": "23JKqAD+um8ObHqzfIh+bfqwG9V8qs9tFY6MqeFR+xxx",

		if envOnly {
			key = config.EnvPrefix + strings.ToTitle(subSys) + config.EnvWordDelimiter + strings.ToTitle(madmin.EnableKey)
		}
		help = append(help, config.HelpKV{
			Key:         key,
			Description: fmt.Sprintf("enable %s target, default is 'off'", subSys),
			Optional:    false,
			Type:        "on|off",
		})
	}

	for _, hkv := range h {
		key := hkv.Key
		if envOnly {

   * will silently add the missing nodes to the graph, then add the edge connecting them. We are not
   * using the proxy methods here as we want to test {@code addEdge} when the end-points are not
   * elements of the graph.
   */
  @Test
  public void addEdge_nodesNotInGraph() {
    assume().that(graphIsMutable()).isTrue();

    networkAsMutableNetwork.addNode(N1);

   * will silently add the missing nodes to the graph, then add the edge connecting them. We are not
   * using the proxy methods here as we want to test {@code addEdge} when the end-points are not
   * elements of the graph.
   */
  @Test
  public void addEdge_nodesNotInGraph() {
    assume().that(graphIsMutable()).isTrue();

    networkAsMutableNetwork.addNode(N1);

    }

    public void test_getUsedMemory() {
        assertTrue(MemoryUtil.getUsedMemory() >= 0);
    }

    public void test_sizeOf() throws Exception {
        // System.out.println("size: " + getObjectSize(""));
        assertEquals(24L, MemoryUtil.sizeOf(Integer.MAX_VALUE));
        assertEquals(24L, MemoryUtil.sizeOf(Long.MAX_VALUE));
        assertEquals(24L, MemoryUtil.sizeOf(Short.MAX_VALUE));