Python 函数为什么会默认返回 None？

<section style="font-family: "Helvetica Neue", Helvetica, "Hiragino Sans GB", "Microsoft YaHei", Arial, sans-serif;white-space: normal;letter-spacing: 0.544px;text-align: left;"><strong><span style="color: rgb(255, 76, 0);font-size: 15px;">推荐阅读：</span></strong></section><section style="margin-right: 16px;margin-left: 16px;font-family: "Helvetica Neue", Helvetica, "Hiragino Sans GB", "Microsoft YaHei", Arial, sans-serif;text-indent: 0em;white-space: normal;letter-spacing: 0.544px;line-height: 2em;text-align: left;"><span style="font-size: 15px;text-decoration: underline;"><strong><span style="color: rgb(0, 0, 0);">华为阿里腾讯下班时间曝光：所有的光鲜，都有加班的味道</span></strong></span></section><section style="margin-right: 16px;margin-left: 16px;font-family: "Helvetica Neue", Helvetica, "Hiragino Sans GB", "Microsoft YaHei", Arial, sans-serif;text-indent: 0em;white-space: normal;letter-spacing: 0.544px;line-height: 2em;text-align: left;"><span style="font-size: 15px;text-decoration: underline;"><strong>收获10400颗星！这个Python库有点黑科技，竟然可以伪造很多'假'的数据！<br  /></strong></span></section><section style="margin-right: 16px;margin-left: 16px;font-family: "Helvetica Neue", Helvetica, "Hiragino Sans GB", "Microsoft YaHei", Arial, sans-serif;text-indent: 0em;white-space: normal;letter-spacing: 0.544px;line-height: 2em;text-align: left;"><span style="font-size: 15px;text-decoration: underline;"><strong>哇塞！NASA 在GitHub上开源了火星探测车<br  /></strong></span></section><section style="margin-right: 16px;margin-left: 16px;font-family: "Helvetica Neue", Helvetica, "Hiragino Sans GB", "Microsoft YaHei", Arial, sans-serif;text-indent: 0em;white-space: normal;letter-spacing: 0.544px;line-height: 2em;text-align: left;"><span style="font-size: 15px;text-decoration: underline;"><strong>Github这个库火了，收获9000颗星！十行Python代码即可生成GUI界面</strong></span></section><section style="margin-right: 16px;margin-left: 16px;font-family: "Helvetica Neue", Helvetica, "Hiragino Sans GB", "Microsoft YaHei", Arial, sans-serif;white-space: normal;letter-spacing: 0.544px;line-height: 2em;text-align: left;">我去！Github 可以这样玩啦！<br  /></section><section style="font-family: "Helvetica Neue", Helvetica, "Hiragino Sans GB", "Microsoft YaHei", Arial, sans-serif;min-height: 1em;line-height: 1.8em;orphans: 4;font-size: 15px;letter-spacing: 0.1em;white-space: pre-wrap;margin: 2em 5px !important;"><span md-inline="plain"><img class="rich_pages" data-cropselx1="0" data-cropselx2="568" data-cropsely1="0" data-cropsely2="378" data-ratio="0.6564625850340136" data-s="300,640" data-type="png" data-w="1176"  style="box-sizing: border-box !important;visibility: visible !important;width: 677px !important;" src="https://www.zkxjob.com/wp-content/uploads/2022/05/wxsync-2022-05-4aee0237cdec4bba3fed02f5f75e5dd5.png"  /></span></section><section data-tool="mdnice编辑器" data-website="https://www.mdnice.com" style="padding-right: 10px;padding-left: 10px;text-align: left;font-family: Optima-Regular, Optima, PingFangSC-light, PingFangTC-light, "PingFang SC", Cambria, Cochin, Georgia, Times, "Times New Roman", serif;line-height: 1.6;letter-spacing: 0.034em;color: rgb(63, 63, 63);"><pre data-darkmode-bgcolor="rgb(36, 36, 36)" data-darkmode-original-bgcolor="rgb(255, 255, 255)" data-darkmode-color="rgb(168, 168, 168)" data-darkmode-original-color="rgb(62, 62, 62)" data-style="letter-spacing: 0.544px; font-weight: 700; text-align: -webkit-center; background-color: rgb(255, 255, 255); font-size: 16px; color: rgb(62, 62, 62); widows: 1; word-spacing: 2px;" class="js_darkmode__26" style="letter-spacing: 0.544px;color: rgb(62, 62, 62);text-align: center;"><pre style="letter-spacing: 0.544px;text-align: left;"><h1 style="white-space: pre-wrap;letter-spacing: 0.544px;font-family: 微软雅黑;"><section mpa-from-tpl="t"><pre style="letter-spacing: 0.544px;word-spacing: 1px;line-height: inherit;"><pre style="letter-spacing: 0.544px;line-height: inherit;"><section data-mpa-template="t" mpa-from-tpl="t"><section data-id="94086" data-color="#276ca3" data-tools="135编辑器" mpa-from-tpl="t"><section><section mpa-from-tpl="t"><pre style="color: rgb(63, 63, 63);letter-spacing: 0.544px;line-height: inherit;"><section data-mpa-template="t" mpa-from-tpl="t"><section data-id="94086" data-color="#276ca3" data-tools="135编辑器" mpa-from-tpl="t"><section><section mpa-from-tpl="t" style="display: inline-block;"><pre style="letter-spacing: 0.544px;line-height: inherit;"><pre data-darkmode-bgcolor-15882384789136="rgb(36, 36, 36)" data-darkmode-original-bgcolor-15882384789136="rgb(255, 255, 255)" data-style="letter-spacing: 0.544px; background-color: rgb(255, 255, 255); text-align: center; color: rgba(230, 230, 230, 0.9); font-size: 16px; line-height: 25.6px; overflow-wrap: break-word !important;" data-darkmode-bgcolor-15882396318564="rgb(36, 36, 36)" data-darkmode-original-bgcolor-15882396318564="rgb(255, 255, 255)" data-darkmode-color-15882396318564="rgba(230, 230, 230, 0.9)" 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data-tools="135编辑器" data-id="91842" data-darkmode-bgcolor-15860613985508="rgb(36, 36, 36)" data-darkmode-original-bgcolor-15860613985508="rgb(255, 255, 255)" data-darkmode-color-15860613985508="rgb(230, 230, 230)" data-darkmode-original-color-15860613985508="rgb(0, 0, 0)" data-darkmode-bgcolor-15870356070738="rgb(36, 36, 36)" data-darkmode-original-bgcolor-15870356070738="rgb(255, 255, 255)" data-darkmode-color-15870356070738="rgb(230, 230, 230)" data-darkmode-original-color-15870356070738="rgb(0, 0, 0)" data-darkmode-bgcolor-15870356071023="rgb(36, 36, 36)" data-darkmode-original-bgcolor-15870356071023="rgb(255, 255, 255)" data-darkmode-color-15870356071023="rgb(230, 230, 230)" data-darkmode-original-color-15870356071023="rgb(0, 0, 0)" data-darkmode-bgcolor-15882384789136="rgb(36, 36, 36)" data-darkmode-original-bgcolor-15882384789136="rgb(255, 255, 255)" data-darkmode-color-15882384789136="rgb(230, 230, 230)" data-darkmode-original-color-15882384789136="rgb(0, 0, 0)" data-darkmode-bgcolor-15882396318564="rgb(36, 36, 36)" data-darkmode-original-bgcolor-15882396318564="rgb(255, 255, 255)" data-darkmode-color-15882396318564="rgb(230, 230, 230)" data-darkmode-original-color-15882396318564="rgb(0, 0, 0)" data-darkmode-bgcolor-15900529136199="rgb(36, 36, 36)" data-darkmode-original-bgcolor-15900529136199="rgb(255, 255, 255)" data-darkmode-color-15900529136199="rgb(230, 230, 230)" data-darkmode-original-color-15900529136199="rgb(0, 0, 0)" style="letter-spacing: 0.544px;border-width: 0px;border-style: none;border-color: initial;"><section data-darkmode-bgcolor-15860613985508="rgb(36, 36, 36)" data-darkmode-original-bgcolor-15860613985508="rgb(255, 255, 255)" data-darkmode-color-15860613985508="rgb(230, 230, 230)" data-darkmode-original-color-15860613985508="rgb(0, 0, 0)" data-darkmode-bgcolor-15870356070738="rgb(36, 36, 36)" data-darkmode-original-bgcolor-15870356070738="rgb(255, 255, 255)" data-darkmode-color-15870356070738="rgb(230, 230, 230)" 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