value = "zh";
        assertEquals("zh", systemHelper.normalizeLang(value));

        value = "zh-cn";
        assertEquals("zh_CN", systemHelper.normalizeLang(value));

        value = "zh_CN";
        assertEquals("zh_CN", systemHelper.normalizeLang(value));

        value = "zh-tw";
        assertEquals("zh_TW", systemHelper.normalizeLang(value));

        value = "zh_TW";

        assertArrays(new String[] { "ja", "zh-cn" }, fessConfig.normalizeQueryLanguages(new String[] { "ja", "zh" }));
        assertArrays(new String[] { "ja", "zh-cn" }, fessConfig.normalizeQueryLanguages(new String[] { "ja", "zh_CN" }));
        assertArrays(new String[] { "ja", "zh-cn" }, fessConfig.normalizeQueryLanguages(new String[] { "ja", "zh-cn" }));

// 現在就可以讀取到環境變數了

Hello Wade Wilson from Python

// 在此之後這個環境變數將不再存在
$ python main.py

Hello World from Python
```

</div>

/// tip

你可以在 <a href="https://12factor.net/zh_cn/config" class="external-link" target="_blank">The Twelve-Factor App: 配置</a>中了解更多資訊。

///

## 型別和驗證

這些環境變數只能處理**文字字串**，因為它們是位於 Python 範疇之外的，必須與其他程式和作業系統的其餘部分相容（甚至與不同的作業系統相容，如 Linux、Windows、macOS）。

supported.uploaded.files=license.properties
# Supported languages.
supported.languages=ar,bg,bn,ca,ckb_IQ,cs,da,de,el,en_IE,en,es,et,eu,fa,fi,fr,gl,gu,he,hi,hr,hu,hy,id,it,ja,ko,lt,lv,mk,ml,nl,no,pa,pl,pt_BR,pt,ro,ru,si,sq,sv,ta,te,th,tl,tr,uk,ur,vi,zh_CN,zh_TW,zh
# Length of API access token.
api.access.token.length=60
# Whether API access token is required.
api.access.token.required=false
# API access token request parameter.
api.access.token.request.parameter=

    /** The key of the configuration. e.g. ar,bg,bn,ca,ckb_IQ,cs,da,de,el,en_IE,en,es,et,eu,fa,fi,fr,gl,gu,he,hi,hr,hu,hy,id,it,ja,ko,lt,lv,mk,ml,nl,no,pa,pl,pt_BR,pt,ro,ru,si,sq,sv,ta,te,th,tl,tr,uk,ur,vi,zh_CN,zh_TW,zh */
    String SUPPORTED_LANGUAGES = "supported.languages";

    /** The key of the configuration. e.g. 60 */
    String API_ACCESS_TOKEN_LENGTH = "api.access.token.length";