然后，您可以调用该 Python 程序：

<div class="termy">

```console
// 这里我们还没有设置环境变量
$ python main.py

// 因为我们没有设置环境变量，所以我们得到默认值

Hello World from Python

// 但是如果我们先创建一个环境变量
$ export MY_NAME="Wade Wilson"

// 然后再次调用程序
$ python main.py

// 现在它可以读取环境变量

Hello Wade Wilson from Python
```

</div>

由于环境变量可以在代码之外设置，但可以由代码读取，并且不需要与其他文件一起存储（提交到 `git`），因此通常将它们用于配置或设置。

    deflatedBytes.writeInt(OCTETS_TO_ADD_BEFORE_INFLATION)

    val totalBytesToRead = inflater.bytesRead + deflatedBytes.size

    // We cannot read all, as the source does not close.
    // Instead, we ensure that all bytes from source have been processed by inflater.
    do {
      inflaterSource.readOrInflate(buffer, Long.MAX_VALUE)
    } while (inflater.bytesRead < totalBytesToRead && !inflater.finished())
  }

  @Throws(IOException::class)

import okio.ByteString.Companion.encodeUtf8
import okio.ByteString.Companion.toByteString
import org.junit.jupiter.api.Assertions.assertEquals
import org.junit.jupiter.api.Test

/** Original version of this class was lifted from `com.twitter.hpack.HuffmanTest`.  */
class HuffmanTest {
  @Test
  fun roundTripForRequestAndResponse() {
    val s = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
    for (i in s.indices) {

      documentation and/or other materials provided with the distribution.
    * Neither the name of the gonum project nor the names of its authors and
      contributors may be used to endorse or promote products derived from this
      software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

<module>
<source path="">
  <!-- Hack to keep collect from hiding collect.testing supersource: -->
  <exclude name="**/testing/**"/>
</source>

<!--
    We used to set this only for packages that had manual supersource. That
    worked everywhere that I know of except for one place: when running the GWT
    util.concurrent tests under Guava.

    The problem is that GWT responds poorly to two .gwt.xml files in the same
    Java package; see

GRADLE_TEMP="$(mktemp -d)"
trap 'rm -rf "${GRADLE_TEMP}"' EXIT

# The Gradle tests need the pom.xml only to read its version number.
# (And the file needs to be two directory levels up from the Gradle build file.)
# TODO(cpovirk): Find a better way to give them that information.
cp pom.xml "${GRADLE_TEMP}"

for version in 5.6.4 7.0.2; do
  # Enter a subshell so that we return to the current directory afterward.

documentation and/or other materials provided with the distribution.

3. Neither the name of the copyright holder nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
“AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

        String mavenVersion = rtInfo.getMavenVersion();

        if (mavenVersion == null || mavenVersion.isEmpty()) {
            throw new InitializationException("Unable to read Maven version from maven-core");
        }

        applicationVersion = new DefaultArtifactVersion(mavenVersion);
    }

in the documentation and/or other materials provided with the
distribution.
   * Neither the name of Google LLC nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

	s.tr = append(s.tr, tr)
}

func (s *Stack) Next() ScanToken {
	tos := s.tr[len(s.tr)-1]
	tok := tos.Next()
	for tok == scanner.EOF && len(s.tr) > 1 {
		tos.Close()
		// Pop the topmost item from the stack and resume with the next one down.
		s.tr = s.tr[:len(s.tr)-1]
		tok = s.Next()
	}
	return tok
}

func (s *Stack) Text() string {
	return s.tr[len(s.tr)-1].Text()
}