<div class="main"> <div class="ad_class"><div class="notice tracking-ad" data-mod="popu_3"> <a href="http://blog.csdn.net/blogdevteam/article/details/61917361"><font color="red">CSDN日报20170313——《测定程序员的代码基因》</font></a> <a href="http://blog.csdn.net/turingbooks/article/details/58072986"><font color="blue">程序员2月书讯</font></a> <a href="http://edu.csdn.net/huiyiCourse/detail/284?ref=blog&loc=r3"><font color="red">【直播】用面向协议的思想简化网络请求</font></a> <a href="http://blog.csdn.net/blogdevteam/article/details/60961185"><font color="blue">博客一键搬家活动开始啦</font></a></div> </div> <link href="http://static.blog.csdn.net/css/comment1.css" type="text/css" rel="stylesheet"><link href="http://static.blog.csdn.net/css/style1.css" type="text/css" rel="stylesheet"><script language="JavaScript" type="text/javascript" src="http://download.csdn.net/js/jquery.cookie.js"></script><script type="text/javascript" src="http://c.csdnimg.cn/rabbit/search-service/main.js"></script><link rel="stylesheet" href="http://static.blog.csdn.net/public/res-min/markdown_views.css?v=1.0"><link rel="stylesheet" href="http://static.blog.csdn.net/css/category.css?v=1.0"><script type="text/javascript" src="http://static.blog.csdn.net/public/res/bower-libs/MathJax/MathJax.js?config=TeX-AMS_HTML"></script><script type="text/javascript" src="http://static.blog.csdn.net/scripts/web-storage-cache.min.js"></script><script type="text/javascript" src="http://static.blog.csdn.net/scripts/replace.min.js"></script> <script type="text/ecmascript"> window.quickReplyflag = true; var isBole = false; var fasrc="http://my.csdn.net/my/favorite/miniadd?t=Python%e4%b8%ad%e7%9a%84None%e4%b8%8e+NULL(%e5%8d%b3%e7%a9%ba%e5%ad%97%e7%ac%a6)%e7%9a%84%e5%8c%ba%e5%88%ab&u=http://blog.csdn.net/li_danny/article/details/49815761" </script><div id="article_details" class="details"> <div class="article_title"> <span class="ico ico_type_Original"></span> <h1> <span class="link_title"><a href="/li_danny/article/details/49815761"> Python中的None与 NULL(即空字符)的区别 </a></span> </h1></div> <div class="article_manage clearfix"> <div class="article_l"> <span class="link_categories"> 标签： <a href="http://www.csdn.net/tag/python" target="_blank" onclick="_gaq.push(['_trackEvent','function', 'onclick', 'blog_articles_tag']);">python</a><a href="http://www.csdn.net/tag/None" target="_blank" onclick="_gaq.push(['_trackEvent','function', 'onclick', 'blog_articles_tag']);">None</a><a href="http://www.csdn.net/tag/Null" target="_blank" onclick="_gaq.push(['_trackEvent','function', 'onclick', 'blog_articles_tag']);">Null</a><a href="http://www.csdn.net/tag/%e5%af%b9%e8%b1%a1" target="_blank" onclick="_gaq.push(['_trackEvent','function', 'onclick', 'blog_articles_tag']);">对象</a><a href="http://www.csdn.net/tag/dir" target="_blank" onclick="_gaq.push(['_trackEvent','function', 'onclick', 'blog_articles_tag']);">dir</a> </span> </div> <div class="article_r"> <span class="link_postdate">2015-11-13 11:50</span> <span class="link_view" title="阅读次数">12532人阅读</span> <span class="link_comments" title="评论次数"> <a href="#comments" onclick="_gaq.push(['_trackEvent','function', 'onclick', 'blog_articles_pinglun'])">评论</a>(0)</span> <span class="link_collect tracking-ad" data-mod="popu_171"> <a href="javascript:void(0);" onclick="javascript:collectArticle('Python%e4%b8%ad%e7%9a%84None%e4%b8%8e+NULL(%e5%8d%b3%e7%a9%ba%e5%ad%97%e7%ac%a6)%e7%9a%84%e5%8c%ba%e5%88%ab','49815761');return false;" title="收藏">收藏</a></span> <span class="link_report"> <a href="#report" onclick="javascript:report(49815761,2);return false;" title="举报">举报</a></span> </div> </div> <div class="embody" style="display:none" id="embody"> <span class="embody_t">本文章已收录于：</span> <div class="embody_c" id="lib" value="{"err":0,"msg":"ok","data":[]}"></div> </div> <style type="text/css"> .embody{ padding:10px 10px 10px; margin:0 -20px; border-bottom:solid 1px #ededed; } .embody_b{ margin:0 ; padding:10px 0; } .embody .embody_t,.embody .embody_c{ display: inline-block; margin-right:10px; } .embody_t{ font-size: 12px; color:#999; } .embody_c{ font-size: 12px; } .embody_c img,.embody_c em{ display: inline-block; vertical-align: middle; } .embody_c img{ width:30px; height:30px; } .embody_c em{ margin: 0 20px 0 10px; color:#333; font-style: normal; } </style> <script type="text/javascript"> $(function () { try { var lib = eval("("+$("#lib").attr("value")+")"); var html = ""; if (lib.err == 0) { $.each(lib.data, function (i) { var obj = lib.data[i]; //html += '<img src="' + obj.logo + '"/>' + obj.name + " "; html += ' <a href="' + obj.url + '" target="_blank">'; html += ' <img src="' + obj.logo + '">'; html += ' <em><b>' + obj.name + '</b></em>'; html += ' </a>'; }); if (html != "") { setTimeout(function () { $("#lib").html(html); $("#embody").show(); }, 100); } } } catch (err) { } }); </script> <div class="category clearfix"> <div class="category_l"> <img src="http://static.blog.csdn.net/images/category_icon.jpg"> <span>分类：</span> </div> <div class="category_r"> <label onclick="GetCategoryArticles('5941803','Li_Danny','top','49815761');"> <span onclick="_gaq.push(['_trackEvent','function', 'onclick', 'blog_articles_fenlei']);">Python语言学习<em>（1）</em></span> <img class="arrow-down" src="http://static.blog.csdn.net/images/arrow_triangle _down.jpg" style="display:inline;"> <img class="arrow-up" src="http://static.blog.csdn.net/images/arrow_triangle_up.jpg" style="display:none;"> <div class="subItem"> <div class="subItem_t"><a href="http://blog.csdn.net/Li_Danny/article/category/5941803" target="_blank">作者同类文章</a><i class="J_close">X</i></div> <ul class="subItem_l" id="top_5941803"> </ul> </div> </label> </div> </div> <script type="text/javascript" src="http://static.blog.csdn.net/scripts/category.js"></script> <div class="bog_copyright"> <p class="copyright_p">版权声明：本文为博主原创文章，未经博主允许不得转载。</p> </div> <div style="clear:both"></div><div style="border:solid 1px #ccc; background:#eee; float:left; min-width:200px;padding:4px 10px;"><p style="text-align:right;margin:0;"><span style="float:left;">目录<a href="#" title="系统根据文章中H1到H6标签自动生成文章目录">(?)</a></span><a href="#" onclick="javascript:return openct(this);" title="展开">[+]</a></p><ol style="display:none;margin-left:14px;padding-left:14px;line-height:160%;"><li><a href="#t0">首先要了解Pythond的对象的概念</a></li><li><a href="#t1">数据类型也是对象</a></li><li><a href="#t2">Python中的None与 NULL即空字符的区别</a></li><li><a href="#t3">总结</a></li></ol></div><div style="clear:both"></div><div id="article_content" class="article_content"> <div class="markdown_views"><h2 id="1首先要了解pythond的对象的概念"><a name="t0"></a>1.首先要了解Pythond的对象的概念：</h2><p><a href="http://lib.csdn.net/base/python" class="replace_word" title="Python知识库" target="_blank" style="color:#df3434; font-weight:bold;">Python</a>中，万物皆对象，所有的操作都是针对对象的，那什么是对象，5是一个int对象，‘oblong’是一个str对象，异常也是一个对象，抽象一点是，人，猫，够也是一个对象</p><p>那对于一个对象，它就有包括两方面的特征： <br>属性：去描述它的特征 <br>方法： 它所具有的行为 <br>所以，对象=属性+方法 （其实方法也是一种属性，一种区别于数据属性的可调用属性</p><p>把具有相同属性和方法的对象就可以归为一类，即Classl。类就好比是一张蓝图，使用一个类可以创建多个对象实例 <br>即人，猫，狗都属于哺乳动物类</p><blockquote> <p>类是对象的抽象化，对象是类的实例化。类不代表具体的事物，而对象表示具体的事物</p></blockquote><p>类也是有属性和方法的。</p><h2 id="2数据类型也是对象"><a name="t1"></a>2.数据类型也是对象</h2><p>实际上Pyhton在面向对象程序设计时，才会有对象这个概念，而在面向过程型程序设计时，我们讨论最多的就是数据类型。</p><p>Python提供的基本数据类型主要有：布尔类型、整型、浮点型、字符串、列表、元组、集合、字典等</p><p>数据类型也可以看做是一个”类“ <br>每一种数据类型都是一个对象，也具有其自己的属性和方法</p><h2 id="3python中的none与-null即空字符的区别"><a name="t2"></a>3.Python中的None与 NULL(即空字符)的区别</h2><p>了解以上概念，就不难理解None 与null的区别 <br>(1)是不同的一种数据类型</p><pre class="prettyprint" name="code"><code class="hljs haskell has-numbering">>>><span class="hljs-typedef"><span class="hljs-keyword">type</span><span class="hljs-container">(<span class="hljs-type">None</span>)</span></span><<span class="hljs-keyword">class</span> '<span class="hljs-type">NoneType'</span>></code><ul class="pre-numbering"><li>1</li><li>2</li></ul><div class="save_code tracking-ad" data-mod="popu_249"><a href="javascript:;"><img src="http://static.blog.csdn.net/images/save_snippets.png"></a></div><ul class="pre-numbering"><li>1</li><li>2</li></ul></pre><p>表示该值是一个空对象，空值是Python里一个特殊的值，用None表示。None不能理解为0，因为0是有意义的，而None是一个特殊的空值。</p><pre class="prettyprint" name="code"><code class="hljs ocaml has-numbering">>>><span class="hljs-class"><span class="hljs-keyword">type</span>(</span><span class="hljs-string">''</span>)<<span class="hljs-keyword">class</span> <span class="hljs-string">''</span>str<span class="hljs-string">'></span></code><ul class="pre-numbering"><li>1</li><li>2</li></ul><div class="save_code tracking-ad" data-mod="popu_249" style="display: none;"><a href="javascript:;"><img src="http://static.blog.csdn.net/images/save_snippets_01.png"></a></div><ul class="pre-numbering"><li>1</li><li>2</li></ul></pre><p>你可以将None赋值给任何变量，也可以将任何变量赋值给一个None值得对象</p><p>(2)判断的时候 均是False</p><pre class="prettyprint" name="code"><code class="hljs python has-numbering"><span class="hljs-prompt">>>> </span>ff=<span class="hljs-keyword">None</span><span class="hljs-prompt">>>> </span><span class="hljs-keyword">if</span> ff: print(<span class="hljs-string">'ff is define'</span>)执行结果：无打印！</code><ul class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li></ul><div class="save_code tracking-ad" data-mod="popu_249"><a href="javascript:;"><img src="http://static.blog.csdn.net/images/save_snippets.png"></a></div><ul class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li></ul></pre><p>(3)属性不同</p><p>使用dir()函数返回参数的属性、方法列表。如果参数包含方法<strong>dir</strong>()，该方法将被调用。如果参数不包含<strong>dir</strong>()，该方法将最大限度地收集参数信息。</p><pre class="prettyprint" name="code"><code class="hljs rust has-numbering"><span class="hljs-keyword">dir</span>(None)[<span class="hljs-string">'__bool__'</span>, <span class="hljs-string">'__class__'</span>, <span class="hljs-string">'__delattr__'</span>, <span class="hljs-string">'__dir__'</span>, <span class="hljs-string">'__doc__'</span>, <span class="hljs-string">'__eq__'</span>, <span class="hljs-string">'__format__'</span>, <span class="hljs-string">'__ge__'</span>, <span class="hljs-string">'__getattribute__'</span>, <span class="hljs-string">'__gt__'</span>, <span class="hljs-string">'__hash__'</span>, <span class="hljs-string">'__init__'</span>, <span class="hljs-string">'__le__'</span>, <span class="hljs-string">'__lt__'</span>, <span class="hljs-string">'__ne__'</span>, <span class="hljs-string">'__new__'</span>, <span class="hljs-string">'__reduce__'</span>, <span class="hljs-string">'__reduce_ex__'</span>, <span class="hljs-string">'__repr__'</span>, <span class="hljs-string">'__setattr__'</span>, <span class="hljs-string">'__sizeof__'</span>, <span class="hljs-string">'__str__'</span>, <span class="hljs-string">'__subclasshook__'</span>]</code><ul class="pre-numbering"><li>1</li><li>2</li></ul><div class="save_code tracking-ad" data-mod="popu_249" style="display: none;"><a href="javascript:;"><img src="http://static.blog.csdn.net/images/save_snippets_01.png"></a></div><ul class="pre-numbering"><li>1</li><li>2</li></ul></pre><pre class="prettyprint" name="code"><code class="hljs rust has-numbering"><span class="hljs-keyword">dir</span>(<span class="hljs-string">''</span>)[<span class="hljs-string">'__add__'</span>, <span class="hljs-string">'__class__'</span>, <span class="hljs-string">'__contains__'</span>, <span class="hljs-string">'__delattr__'</span>, <span class="hljs-string">'__dir__'</span>, <span class="hljs-string">'__doc__'</span>, <span class="hljs-string">'__eq__'</span>, <span class="hljs-string">'__format__'</span>, <span class="hljs-string">'__ge__'</span>, <span class="hljs-string">'__getattribute__'</span>, <span class="hljs-string">'__getitem__'</span>, <span class="hljs-string">'__getnewargs__'</span>, <span class="hljs-string">'__gt__'</span>, <span class="hljs-string">'__hash__'</span>, <span class="hljs-string">'__init__'</span>, <span class="hljs-string">'__iter__'</span>, <span class="hljs-string">'__le__'</span>, <span class="hljs-string">'__len__'</span>, <span class="hljs-string">'__lt__'</span>, <span class="hljs-string">'__mod__'</span>, <span class="hljs-string">'__mul__'</span>, <span class="hljs-string">'__ne__'</span>, <span class="hljs-string">'__new__'</span>, <span class="hljs-string">'__reduce__'</span>, <span class="hljs-string">'__reduce_ex__'</span>, <span class="hljs-string">'__repr__'</span>, <span class="hljs-string">'__rmod__'</span>, <span class="hljs-string">'__rmul__'</span>, <span class="hljs-string">'__setattr__'</span>, <span class="hljs-string">'__sizeof__'</span>, <span class="hljs-string">'__str__'</span>, <span class="hljs-string">'__subclasshook__'</span>, <span class="hljs-string">'capitalize'</span>, <span class="hljs-string">'casefold'</span>, <span class="hljs-string">'center'</span>, <span class="hljs-string">'count'</span>, <span class="hljs-string">'encode'</span>, <span class="hljs-string">'endswith'</span>, <span class="hljs-string">'expandtabs'</span>, <span class="hljs-string">'find'</span>, <span class="hljs-string">'format'</span>, <span class="hljs-string">'format_map'</span>, <span class="hljs-string">'index'</span>, <span class="hljs-string">'isalnum'</span>, <span class="hljs-string">'isalpha'</span>, <span class="hljs-string">'isdecimal'</span>, <span class="hljs-string">'isdigit'</span>, <span class="hljs-string">'isidentifier'</span>, <span class="hljs-string">'islower'</span>, <span class="hljs-string">'isnumeric'</span>, <span class="hljs-string">'isprintable'</span>, <span class="hljs-string">'isspace'</span>, <span class="hljs-string">'istitle'</span>, <span class="hljs-string">'isupper'</span>, <span class="hljs-string">'join'</span>, <span class="hljs-string">'ljust'</span>, <span class="hljs-string">'lower'</span>, <span class="hljs-string">'lstrip'</span>, <span class="hljs-string">'maketrans'</span>, <span class="hljs-string">'partition'</span>, <span class="hljs-string">'replace'</span>, <span class="hljs-string">'rfind'</span>, <span class="hljs-string">'rindex'</span>, <span class="hljs-string">'rjust'</span>, <span class="hljs-string">'rpartition'</span>, <span class="hljs-string">'rsplit'</span>, <span class="hljs-string">'rstrip'</span>, <span class="hljs-string">'split'</span>, <span class="hljs-string">'splitlines'</span>, <span class="hljs-string">'startswith'</span>, <span class="hljs-string">'strip'</span>, <span class="hljs-string">'swapcase'</span>, <span class="hljs-string">'title'</span>, <span class="hljs-string">'translate'</span>, <span class="hljs-string">'upper'</span>, <span class="hljs-string">'zfill'</span>]</code><ul class="pre-numbering"><li>1</li><li>2</li></ul><div class="save_code tracking-ad" data-mod="popu_249" style="display: none;"><a href="javascript:;"><img src="http://static.blog.csdn.net/images/save_snippets_01.png"></a></div><ul class="pre-numbering"><li>1</li><li>2</li></ul></pre><h2 id="总结"><a name="t3"></a>总结：</h2><p>本文解释了None与 NULL(即空字符)的区别,以及Python中对象，类的概念，以及type()，dir()函数的使用。</p></div> <script type="text/javascript"> $(function () { $('pre.prettyprint code').each(function () { var lines = $(this).text().split('\n').length; var $numbering = $('<ul></ul>').addClass('pre-numbering').hide(); $(this).addClass('has-numbering').parent().append($numbering); for (i = 1; i <= lines; i++) { $numbering.append($('<li></li>').text(i)); }; $numbering.fadeIn(1700); }); }); </script> </div><!-- Baidu Button BEGIN --><div class="bdsharebuttonbox tracking-ad bdshare-button-style0-16" style="float: right;" data-mod="popu_172" data-bd-bind="1489421004882"><a href="#" class="bds_more" data-cmd="more" style="background-position:0 0 !important; background-image: url(http://bdimg.share.baidu.com/static/api/img/share/icons_0_16.png?v=d754dcc0.png) !important"></a><a href="#" class="bds_qzone" data-cmd="qzone" title="分享到QQ空间" style="background-position:0 -52px !important"></a><a href="#" class="bds_tsina" data-cmd="tsina" title="分享到新浪微博" style="background-position:0 -104px !important"></a><a href="#" class="bds_tqq" data-cmd="tqq" title="分享到腾讯微博" style="background-position:0 -260px !important"></a><a href="#" class="bds_renren" data-cmd="renren" title="分享到人人网" style="background-position:0 -208px !important"></a><a href="#" class="bds_weixin" data-cmd="weixin" title="分享到微信" style="background-position:0 -1612px !important"></a></div><script>window._bd_share_config = { "common": { "bdSnsKey": {}, "bdText": "", "bdMini": "1", "bdMiniList": false, "bdPic": "", "bdStyle": "0", "bdSize": "16" }, "share": {} }; with (document) 0[(getElementsByTagName('head')[0] || body).appendChild(createElement('script')).src = 'http://bdimg.share.baidu.com/static/api/js/share.js?v=89860593.js?cdnversion=' + ~(-new Date() / 36e5)];</script><!-- Baidu Button END --> <link rel="stylesheet" href="http://static.blog.csdn.net/css/blog_detail.css"> <!--172.16.140.13--><!-- Baidu Button BEGIN --><script type="text/javascript" id="bdshare_js" data="type=tools&uid=1536434" src="http://bdimg.share.baidu.com/static/js/bds_s_v2.js?cdnversion=413729"></script><script type="text/javascript"> document.getElementById("bdshell_js").src = "http://bdimg.share.baidu.com/static/js/shell_v2.js?cdnversion=" + Math.ceil(new Date()/3600000)</script><!-- Baidu Button END --> <div id="digg" articleid="49815761"> <dl id="btnDigg" class="digg digg_enable" onclick="btndigga();"> <dt>顶</dt> <dd>3</dd> </dl> <dl id="btnBury" class="digg digg_enable" onclick="btnburya();"> <dt>踩</dt> <dd>0</dd> </dl> </div> <div class="tracking-ad" data-mod="popu_222"><a href="javascript:void(0);"> </a> </div> <div class="tracking-ad" data-mod="popu_223"> <a href="javascript:void(0);"> </a></div> <script type="text/javascript"> function btndigga() { $(".tracking-ad[data-mod='popu_222'] a").click(); } function btnburya() { $(".tracking-ad[data-mod='popu_223'] a").click(); } </script> <ul class="article_next_prev"> <li class="prev_article"><span onclick="_gaq.push(['_trackEvent','function', 'onclick', 'blog_articles_shangyipian']);location.href='/li_danny/article/details/49803175';">上一篇</span><a href="/li_danny/article/details/49803175" onclick="_gaq.push(['_trackEvent','function', 'onclick', 'blog_articles_shangyipian'])">ASCII、Unicode、GBK和UTF-8字符编码的区别联系</a></li> <li class="next_article"><span onclick="_gaq.push(['_trackEvent','function', 'onclick', 'blog_articles_xiayipian']);location.href='/li_danny/article/details/49890783';">下一篇</span><a href="/li_danny/article/details/49890783" onclick="_gaq.push(['_trackEvent','function', 'onclick', 'blog_articles_xiayipian'])">解析#define NULL ((void *)0)——野指针，空指针和 void*</a></li> </ul> <div style="clear:both; height:10px;"></div> <div class="similar_article" style=""> <h4>我的同类文章</h4> <div class="similar_c" style="margin:20px 0px 0px 0px"> <div class="similar_c_t"> <label class="similar_cur"> <span style="cursor:pointer" onclick="GetCategoryArticles('5941803','Li_Danny','foot','49815761');">Python语言学习<em>（1）</em></span> </label> </div> <div class="similar_wrap tracking-ad" data-mod="popu_141" style="max-height:195px;"> <a href="http://blog.csdn.net" style="display:none">http://blog.csdn.net</a> <ul class="similar_list fl"><li><em>•</em><a href="http://blog.csdn.net/Li_Danny/article/details/49739785" id="foot_aritcle_49739785undefined4526368836151009" target="_blank" title="Python3.4(Pyhon)代码如何打包成.exe可执行文件——详细教程">Python3.4(Pyhon)代码如何打包成.exe可执行文件——详细教程</a><span>2015-11-09</span><label><i>阅读</i><b>2439</b></label></li> </ul> <ul class="similar_list fr"></ul> </div> </div> </div> <script type="text/javascript"> $(function () { GetCategoryArticles('5941803', 'Li_Danny','foot','49815761'); }); </script> </div> <div> <ins data-revive-zoneid="205" data-revive-id="8c38e720de1c90a6f6ff52f3f89c4d57"></ins> </div><div id="suggest"></div> <script language="javascript" type="text/javascript"> $(function(){ $.get("/Li_Danny/svc/GetSuggestContent/49815761",function(data){ $("#suggest").html(data); }); }); </script> <style>.blog-ass-articl dd {color: #369;width: 99%; /*修改行*/float: left;overflow: hidden;font: normal normal 12px/23px "SimSun";height: 23px;margin: 0;padding: 0 0 0 10px;margin-right: 30px;background: url(http://static.blog.csdn.net/skin/default/images/blog-dot-red3.gif) no-repeat 0 10px;}</style> <link rel="stylesheet" href="http://static.blog.csdn.net/css/replace.css"><div id="relate" data-mod="popu_218" class="tracking-ad" style="display: block;"> <div class="relate_t"> <h3><span>参考知识库</span></h3> </div> <div class="relate_c"><dl class="relate_list"><dt><a target="_blank" href="http://lib.csdn.net/base/python"><img src="http://img.knowledge.csdn.net/upload/base/1452500783406_406.jpg" alt="img"></a></dt><dd><h4><a target="_blank" href="http://lib.csdn.net/base/python">Python知识库</a></h4><p><label><span>20909</span><em>关注</em><i>|</i><span>1342</span><em>收录</em></label></p></dd></dl></div></div> <dl class="blog-ass-articl" id="res-relatived"> <div class="embody embody_b" id="libkeyparent" style="display:none"> <span class="embody_t">更多资料请参考：</span> <div class="embody_c" id="libkey"></div> </div> <dt><span>猜你在找</span></dt> <div id="adCollege" style="width: 42%;float: left;"> <script src="http://csdnimg.cn/jobreco/job_reco.js" type="text/javascript"></script> <script type="text/javascript"> csdn.position.showEdu({ sourceType: "blog", searchType: "detail", searchKey: "49815761", username: "guizaijianchic", recordcount: "5", containerId: "adCollege" //容器DIV的id。 }); setEduLoc(); function setEduLoc() { var edus = $("#adCollege div dd a"); if (edus.length == 0) { setTimeout(function () { setEduLoc(); }, 500); } else { var eduLoc = "?ref=blog&loc=0"; $.each(edus, function (index,item) { var href = $(this).attr("href") + eduLoc; $(this).attr("href", href); }); } } </script> <div class="tracking-ad" data-mod="popu_84"><dd style="background:url(http://static.blog.csdn.net/skin/default/images/blog-dot-red3.gif) no-repeat 0 10px; white-space: nowrap;"><a href="http://edu.csdn.net/course/detail/4307?ref=blog&loc=0" title="python面向对象" strategy="v4:content" target="_blank">python面向对象</a></dd><dd style="background:url(http://static.blog.csdn.net/skin/default/images/blog-dot-red3.gif) no-repeat 0 10px; white-space: nowrap;"><a href="http://edu.csdn.net/course/detail/747?ref=blog&loc=0" title="Python自动化开发基础 装饰器-异常处理-面向对象编程 day4" strategy="v4:content" target="_blank">Python自动化开发基础 装饰器-异常处理-面向对象编程 day4</a></dd><dd style="background:url(http://static.blog.csdn.net/skin/default/images/blog-dot-red3.gif) no-repeat 0 10px; white-space: nowrap;"><a href="http://edu.csdn.net/course/detail/744?ref=blog&loc=0" title="Python自动化开发基础 列表-字典-IO处理 day2" strategy="v4:content" target="_blank">Python自动化开发基础 列表-字典-IO处理 day2</a></dd><dd style="background:url(http://static.blog.csdn.net/skin/default/images/blog-dot-red3.gif) no-repeat 0 10px; white-space: nowrap;"><a href="http://edu.csdn.net/course/detail/3569?ref=blog&loc=0" title="Python数据分析与挖掘经典案例实战" strategy="v4:content" target="_blank">Python数据分析与挖掘经典案例实战</a></dd><dd style="background:url(http://static.blog.csdn.net/skin/default/images/blog-dot-red3.gif) no-repeat 0 10px; white-space: nowrap;"><a href="http://edu.csdn.net/course/detail/2556?ref=blog&loc=0" title="Python基础编程1小时快速实战掌握" strategy="v4:content" target="_blank">Python基础编程1小时快速实战掌握</a></dd></div></div> <div id="res" data-mod="popu_36" class="tracking-ad" style="width: 42%; float: left; margin-right: 30px; display: none;"></div> </dl><script type="text/javascript"> $(function () { setTimeout(function () { var searchtitletags = 'Python中的None与 NULL(即空字符)的区别' + ',' + $("#tags").html(); searchService({ index: 'blog', query: searchtitletags, from: 5, size: 5, appendTo: '#res', url: 'recommend', his: 2, client: "blog_cf_enhance", tmpl: '<dd style="background:url(http://static.blog.csdn.net/skin/default/images/blog-dot-red3.gif) no-repeat 0 10px;"><a href="#{ url }" title="#{ title }" strategy="#{ strategy }">#{ title }</a></dd>' }); }, 500); }); </script> <div id="ad_cen"> <ins data-revive-zoneid="71" data-revive-id="8c38e720de1c90a6f6ff52f3f89c4d57"></ins> </div> <!-- 广告位开始 --> <ins data-revive-zoneid="72" data-revive-id="8c38e720de1c90a6f6ff52f3f89c4d57"></ins> <!-- 广告位结束 --><div class="comment_class"> <div id="comment_title" class="panel_head"> <span class="see_comment">查看评论</span><a name="comments"></a></div> <div id="comment_list"><br> 暂无评论<br><br><div class="clear"></div></div> <div id="comment_bar"> </div> <div id="comment_form"><a name="commentbox"></a><a name="reply"></a><a name="quote"></a><form action="/Li_Danny/comment/submit?id=49815761" method="post" onsubmit="return subform(this);"><div class="commentform"><div class="panel_head">发表评论</div><ul><li class="left">用 户 名：</li><li class="right">guizaijianchic</li></ul><ul><li class="left">评论内容：</li><li class="right" style="position:relative;"><div id="ubbtools"><a href="#insertcode" code="code"><img src="http://static.blog.csdn.net/images/ubb/code.gif" border="0" alt="插入代码" title="插入代码"></a></div><div id="lang_list" style="position: absolute; top: 28px; left: 0px; display: none;"><a class="long_name" href="#html">HTML/XML</a><a class="long_name" href="#objc">objective-c</a><a class="zhong_name" href="#delphi">Delphi</a><a class="zhong_name" href="#ruby">Ruby</a><a href="#php">PHP</a><a class="duan_name" href="#csharp">C#</a><a style=" border-right: none;" class="duan_name" href="#cpp">C++</a><a style=" border-bottom:none;" class="long_name" href="#javascript">JavaScript</a><a style=" border-bottom:none;" class="long_name" href="#vb">Visual Basic</a><a style=" border-bottom:none;" class="zhong_name" href="#python">Python</a><a style=" border-bottom:none;" class="zhong_name" href="#java">Java</a><a style="border-bottom:none;" class="duan_name" href="#css">CSS</a><a style="border-bottom:none;" class="duan_name" href="#sql">SQL</a><a style="border:none;" class="duan_name" href="#plain">其它</a></div><textarea class="comment_content" name="comment_content" id="comment_content" style="width: 400px; height: 200px;"></textarea></li></ul><ul><input type="hidden" id="comment_replyId" name="comment_replyId"><input type="hidden" id="comment_userId" name="comment_userId" value="521203"><input type="hidden" id="commentId" name="commentId" value=""><input type="submit" class="comment_btn" value="提交"> <span id="tip_comment" style="color: Red; display: none;"></span></ul></div></form></div> <div class="announce"> * 以上用户言论只代表其个人观点，不代表CSDN网站的观点或立场<a name="reply"></a><a name="quote"></a></div></div><script type="text/javascript"> var fileName = '49815761'; var commentscount = 0; var islock = false</script><script type="text/javascript" src="http://static.blog.csdn.net/scripts/comment.js"></script> <div id="ad_bot"> </div><div id="report_dialog"></div><div id="d-top" style="bottom:60px;"> <a id="quick-reply" class="btn btn-top q-reply" title="快速回复" style="display:none;"> <img src="http://static.blog.csdn.net/images/blog-icon-reply.png" alt="快速回复"> </a> <a id="d-top-a" class="btn btn-top backtop" style="display: none;" title="返回顶部" onclick="_gaq.push(['_trackEvent','function', 'onclick', 'blog_articles_huidaodingbu'])"> <img src="http://static.blog.csdn.net/images/top.png" alt="TOP"> </a></div><script type="text/javascript"> $(function () { $("#ad_frm_0").height("90px"); setTimeout(function(){ $("#ad_frm_2").height("200px"); },1000); }); </script><style type="text/css"> .tag_list { background: none repeat scroll 0 0 #FFFFFF; border: 1px solid #D7CBC1; color: #000000; font-size: 12px; line-height: 20px; list-style: none outside none; margin: 10px 2% 0 1%; padding: 1px; } .tag_list h5 { background: none repeat scroll 0 0 #E0DBD3; color: #47381C; font-size: 12px; height: 24px; line-height: 24px; padding: 0 5px; margin: 0; } .tag_list h5 a { color: #47381C; } .classify { margin: 10px 0; padding: 4px 12px 8px; } .classify a { margin-right: 20px; white-space: nowrap; }</style><div class="tag_list" style=""> <h5> <a href="http://www.csdn.net/tag/" target="_blank">核心技术类目</a></h5> <div class="classify"><a title="全部主题" href="http://www.csdn.net/tag" target="_blank" onclick="LogClickCount(this,336);">全部主题</a><a title="Hadoop" href="http://g.csdn.net/5272865" target="_blank" onclick="LogClickCount(this,336);">Hadoop</a><a title="AWS" href="http://g.csdn.net/5272866" target="_blank" onclick="LogClickCount(this,336);">AWS</a><a title="移动游戏" href="http://g.csdn.net/5272870" target="_blank" onclick="LogClickCount(this,336);">移动游戏</a><a title="Java" href="http://g.csdn.net/5272871" target="_blank" onclick="LogClickCount(this,336);">Java</a><a title="Android" href="http://g.csdn.net/5272872" target="_blank" onclick="LogClickCount(this,336);">Android</a><a title="iOS" href="http://g.csdn.net/5272873" target="_blank" onclick="LogClickCount(this,336);">iOS</a><a title="Swift" href="http://g.csdn.net/5272868" target="_blank" onclick="LogClickCount(this,336);">Swift</a><a title="智能硬件" href="http://g.csdn.net/5272869" target="_blank" onclick="LogClickCount(this,336);">智能硬件</a><a title="Docker" href="http://g.csdn.net/5272867" target="_blank" onclick="LogClickCount(this,336);">Docker</a><a title="OpenStack" href="http://g.csdn.net/5272925" target="_blank" onclick="LogClickCount(this,336);">OpenStack</a><a title="VPN" href="http://www.csdn.net/tag/vpn" target="_blank" onclick="LogClickCount(this,336);">VPN</a><a title="Spark" href="http://g.csdn.net/5272924" target="_blank" onclick="LogClickCount(this,336);">Spark</a><a title="ERP" href="http://www.csdn.net/tag/erp" target="_blank" onclick="LogClickCount(this,336);">ERP</a><a title="IE10" href="http://www.csdn.net/tag/ie10" target="_blank" onclick="LogClickCount(this,336);">IE10</a><a title="Eclipse" href="http://www.csdn.net/tag/eclipse" target="_blank" onclick="LogClickCount(this,336);">Eclipse</a><a title="CRM" href="http://www.csdn.net/tag/crm" target="_blank" onclick="LogClickCount(this,336);">CRM</a><a title="JavaScript" href="http://www.csdn.net/tag/javascript" target="_blank" onclick="LogClickCount(this,336);">JavaScript</a><a title="数据库" href="http://www.csdn.net/tag/数据库" target="_blank" onclick="LogClickCount(this,336);">数据库</a><a title="Ubuntu" href="http://www.csdn.net/tag/ubuntu" target="_blank" onclick="LogClickCount(this,336);">Ubuntu</a><a title="NFC" href="http://www.csdn.net/tag/nfc" target="_blank" onclick="LogClickCount(this,336);">NFC</a><a title="WAP" href="http://www.csdn.net/tag/wap" target="_blank" onclick="LogClickCount(this,336);">WAP</a><a title="jQuery" href="http://www.csdn.net/tag/jquery" target="_blank" onclick="LogClickCount(this,336);">jQuery</a><a title="BI" href="http://www.csdn.net/tag/bi" target="_blank" onclick="LogClickCount(this,336);">BI</a><a title="HTML5" href="http://www.csdn.net/tag/html5" target="_blank" onclick="LogClickCount(this,336);">HTML5</a><a title="Spring" href="http://www.csdn.net/tag/spring" target="_blank" onclick="LogClickCount(this,336);">Spring</a><a title="Apache" href="http://www.csdn.net/tag/apache" target="_blank" onclick="LogClickCount(this,336);">Apache</a><a title=".NET" href="http://www.csdn.net/tag/.net" target="_blank" onclick="LogClickCount(this,336);">.NET</a><a title="API" href="http://www.csdn.net/tag/api" target="_blank" onclick="LogClickCount(this,336);">API</a><a title="HTML" href="http://www.csdn.net/tag/html" target="_blank" onclick="LogClickCount(this,336);">HTML</a><a title="SDK" href="http://www.csdn.net/tag/sdk" target="_blank" onclick="LogClickCount(this,336);">SDK</a><a title="IIS" href="http://www.csdn.net/tag/iis" target="_blank" onclick="LogClickCount(this,336);">IIS</a><a title="Fedora" href="http://www.csdn.net/tag/fedora" target="_blank" onclick="LogClickCount(this,336);">Fedora</a><a title="XML" href="http://www.csdn.net/tag/xml" target="_blank" onclick="LogClickCount(this,336);">XML</a><a title="LBS" href="http://www.csdn.net/tag/lbs" target="_blank" onclick="LogClickCount(this,336);">LBS</a><a title="Unity" href="http://www.csdn.net/tag/unity" target="_blank" onclick="LogClickCount(this,336);">Unity</a><a title="Splashtop" href="http://www.csdn.net/tag/splashtop" target="_blank" onclick="LogClickCount(this,336);">Splashtop</a><a title="UML" href="http://www.csdn.net/tag/uml" target="_blank" onclick="LogClickCount(this,336);">UML</a><a title="components" href="http://www.csdn.net/tag/components" target="_blank" onclick="LogClickCount(this,336);">components</a><a title="Windows Mobile" href="http://www.csdn.net/tag/windowsmobile" target="_blank" onclick="LogClickCount(this,336);">Windows Mobile</a><a title="Rails" href="http://www.csdn.net/tag/rails" target="_blank" onclick="LogClickCount(this,336);">Rails</a><a title="QEMU" href="http://www.csdn.net/tag/qemu" target="_blank" onclick="LogClickCount(this,336);">QEMU</a><a title="KDE" href="http://www.csdn.net/tag/kde" target="_blank" onclick="LogClickCount(this,336);">KDE</a><a title="Cassandra" href="http://www.csdn.net/tag/cassandra" target="_blank" onclick="LogClickCount(this,336);">Cassandra</a><a title="CloudStack" href="http://www.csdn.net/tag/cloudstack" target="_blank" onclick="LogClickCount(this,336);">CloudStack</a><a title="FTC" href="http://www.csdn.net/tag/ftc" target="_blank" onclick="LogClickCount(this,336);">FTC</a><a title="coremail" href="http://www.csdn.net/tag/coremail" target="_blank" onclick="LogClickCount(this,336);">coremail</a><a title="OPhone " href="http://www.csdn.net/tag/ophone " target="_blank" onclick="LogClickCount(this,336);">OPhone </a><a title="CouchBase" href="http://www.csdn.net/tag/couchbase" target="_blank" onclick="LogClickCount(this,336);">CouchBase</a><a title="云计算" href="http://www.csdn.net/tag/云计算" target="_blank" onclick="LogClickCount(this,336);">云计算</a><a title="iOS6" href="http://www.csdn.net/tag/iOS6" target="_blank" onclick="LogClickCount(this,336);">iOS6</a><a title="Rackspace " href="http://www.csdn.net/tag/rackspace " target="_blank" onclick="LogClickCount(this,336);">Rackspace </a><a title="Web App" href="http://www.csdn.net/tag/webapp" target="_blank" onclick="LogClickCount(this,336);">Web App</a><a title="SpringSide" href="http://www.csdn.net/tag/springside" target="_blank" onclick="LogClickCount(this,336);">SpringSide</a><a title="Maemo" href="http://www.csdn.net/tag/maemo" target="_blank" onclick="LogClickCount(this,336);">Maemo</a><a title="Compuware" href="http://www.csdn.net/tag/compuware" target="_blank" onclick="LogClickCount(this,336);">Compuware</a><a title="大数据" href="http://www.csdn.net/tag/大数据" target="_blank" onclick="LogClickCount(this,336);">大数据</a><a title="aptech" href="http://www.csdn.net/tag/aptech" target="_blank" onclick="LogClickCount(this,336);">aptech</a><a title="Perl" href="http://www.csdn.net/tag/perl" target="_blank" onclick="LogClickCount(this,336);">Perl</a><a title="Tornado" href="http://www.csdn.net/tag/tornado" target="_blank" onclick="LogClickCount(this,336);">Tornado</a><a title="Ruby" href="http://www.csdn.net/tag/ruby" target="_blank" onclick="LogClickCount(this,336);">Ruby</a><a title="Hibernate" href="http://www.csdn.net/hibernate" target="_blank" onclick="LogClickCount(this,336);">Hibernate</a><a title="ThinkPHP" href="http://www.csdn.net/tag/thinkphp" target="_blank" onclick="LogClickCount(this,336);">ThinkPHP</a><a title="HBase" href="http://www.csdn.net/tag/hbase" target="_blank" onclick="LogClickCount(this,336);">HBase</a><a title="Pure" href="http://www.csdn.net/tag/pure" target="_blank" onclick="LogClickCount(this,336);">Pure</a><a title="Solr" href="http://www.csdn.net/tag/solr" target="_blank" onclick="LogClickCount(this,336);">Solr</a><a title="Angular" href="http://www.csdn.net/tag/angular" target="_blank" onclick="LogClickCount(this,336);">Angular</a><a title="Cloud Foundry" href="http://www.csdn.net/tag/cloudfoundry" target="_blank" onclick="LogClickCount(this,336);">Cloud Foundry</a><a title="Redis" href="http://www.csdn.net/tag/redis" target="_blank" onclick="LogClickCount(this,336);">Redis</a><a title="Scala" href="http://www.csdn.net/tag/scala" target="_blank" onclick="LogClickCount(this,336);">Scala</a><a title="Django" href="http://www.csdn.net/tag/django" target="_blank" onclick="LogClickCount(this,336);">Django</a><a title="Bootstrap" href="http://www.csdn.net/tag/bootstrap" target="_blank" onclick="LogClickCount(this,336);">Bootstrap</a> </div></div> <script language="javascript" type="text/javascript"> $(function(){ setTimeout(function(){ $.get("/Li_Danny/svc/GetTagContent",function(data){ $(".tag_list").html(data).show(); }); }); },500); </script> <div id="pop_win" style="display:none ;position: absolute; z-index: 10000; border: 1px solid rgb(220, 220, 220); top: 222.5px; left: 630px; opacity: 1; background: none 0px 0px repeat scroll rgb(255, 255, 255);"> </div><div id="popup_mask"></div><style> #popup_mask { position: absolute; width: 100%; height: 100%; background: #000; z-index: 9999; left: 0px; top: 0px; opacity: 0.3; filter: alpha(opacity=30); display: none; }</style><script type="text/javascript"> $(function(){ setTimeout(function(){ $(".comment_body:contains('回复')").each(function(index,item){ var u=$(this).text().split('：')[0].toString().replace("回复","") var thisComment=$(this); if(u) { $.getJSON("https://passport.csdn.net/get/nick?callback=?", {users: u}, function(a) { if(a!=null&&a.data!=null&&a.data.length>0) { nick=a.data[0].n; if(u!=nick) { thisComment.text(thisComment.text().replace(u,nick)); } } }); } }); },200); setTimeout(function(){ $(".math").each(function(index,value){$(this).find("span").last().css("color","#fff"); }) },5000); setTimeout(function(){ $(".math").each(function(index,value){$(this).find("span").last().css("color","#fff"); }) },10000); setTimeout(function(){ $(".math").each(function(index,value){$(this).find("span").last().css("color","#fff"); }) },15000); setTimeout(function(){ $("a img[src='http://js.tongji.linezing.com/stats.gif']").parent().css({"position":"absolute","left":"50%"}); },300); }); function loginbox(){ var $logpop=$("#pop_win"); $logpop.html('<iframe src="https://passport.csdn.net/account/loginbox?service=http://static.blog.csdn.net/callback.htm" frameborder="0" height="600" width="400" scrolling="no"></iframe>'); $('#popup_mask').css({ opacity: 0.5, width: $( document ).width() + 'px', height: $( document ).height() + 'px' }); $('#popup_mask').css("display","block"); $logpop.css( { top: ($( window ).height() - $logpop.height())/ 2 + $( window ).scrollTop() + 'px', left:($( window ).width() - $logpop.width())/ 2 } ); setTimeout( function () { $logpop.show(); $logpop.css( { opacity: 1 } ); }, 200 ); $('#popup_mask').unbind("click"); $('#popup_mask').bind("click", function(){ $('#popup_mask').hide(); var $clopop = $("#pop_win"); $("#common_ask_div_sc").css("display","none"); $clopop.css( { opacity: 0 } ); setTimeout( function () { $clopop.hide(); }, 350 ); return false; }); } </script> <script language="javascript" type="text/javascript" src="http://ads.csdn.net/js/async_new.js"></script> <div class="clear"> </div> </div>
<div class="markdown_views"><h2 id="1首先要了解pythond的对象的概念"><a name="t0"></a>1.首先要了解Pythond的对象的概念：</h2><p><a href="http://lib.csdn.net/base/python" class="replace_word" title="Python知识库" target="_blank" style="color:#df3434; font-weight:bold;">Python</a>中，万物皆对象，所有的操作都是针对对象的，那什么是对象，5是一个int对象，‘oblong’是一个str对象，异常也是一个对象，抽象一点是，人，猫，够也是一个对象</p><p>那对于一个对象，它就有包括两方面的特征： <br>属性：去描述它的特征 <br>方法： 它所具有的行为 <br>所以，对象=属性+方法 （其实方法也是一种属性，一种区别于数据属性的可调用属性</p><p>把具有相同属性和方法的对象就可以归为一类，即Classl。类就好比是一张蓝图，使用一个类可以创建多个对象实例 <br>即人，猫，狗都属于哺乳动物类</p><blockquote> <p>类是对象的抽象化，对象是类的实例化。类不代表具体的事物，而对象表示具体的事物</p></blockquote><p>类也是有属性和方法的。</p><h2 id="2数据类型也是对象"><a name="t1"></a>2.数据类型也是对象</h2><p>实际上Pyhton在面向对象程序设计时，才会有对象这个概念，而在面向过程型程序设计时，我们讨论最多的就是数据类型。</p><p>Python提供的基本数据类型主要有：布尔类型、整型、浮点型、字符串、列表、元组、集合、字典等</p><p>数据类型也可以看做是一个”类“ <br>每一种数据类型都是一个对象，也具有其自己的属性和方法</p><h2 id="3python中的none与-null即空字符的区别"><a name="t2"></a>3.Python中的None与 NULL(即空字符)的区别</h2><p>了解以上概念，就不难理解None 与null的区别 <br>(1)是不同的一种数据类型</p><pre class="prettyprint" name="code"><code class="hljs haskell has-numbering">>>><span class="hljs-typedef"><span class="hljs-keyword">type</span><span class="hljs-container">(<span class="hljs-type">None</span>)</span></span><<span class="hljs-keyword">class</span> '<span class="hljs-type">NoneType'</span>></code><ul class="pre-numbering"><li>1</li><li>2</li></ul><div class="save_code tracking-ad" data-mod="popu_249" style="display: none;"><a href="javascript:;"><img src="http://static.blog.csdn.net/images/save_snippets_01.png"></a></div><ul class="pre-numbering"><li>1</li><li>2</li></ul></pre><p>表示该值是一个空对象，空值是Python里一个特殊的值，用None表示。None不能理解为0，因为0是有意义的，而None是一个特殊的空值。</p><pre class="prettyprint" name="code"><code class="hljs ocaml has-numbering">>>><span class="hljs-class"><span class="hljs-keyword">type</span>(</span><span class="hljs-string">''</span>)<<span class="hljs-keyword">class</span> <span class="hljs-string">''</span>str<span class="hljs-string">'></span></code><ul class="pre-numbering"><li>1</li><li>2</li></ul><div class="save_code tracking-ad" data-mod="popu_249" style="display: none;"><a href="javascript:;"><img src="http://static.blog.csdn.net/images/save_snippets_01.png"></a></div><ul class="pre-numbering"><li>1</li><li>2</li></ul></pre><p>你可以将None赋值给任何变量，也可以将任何变量赋值给一个None值得对象</p><p>(2)判断的时候 均是False</p><pre class="prettyprint" name="code"><code class="hljs python has-numbering"><span class="hljs-prompt">>>> </span>ff=<span class="hljs-keyword">None</span><span class="hljs-prompt">>>> </span><span class="hljs-keyword">if</span> ff: print(<span class="hljs-string">'ff is define'</span>)执行结果：无打印！</code><ul class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li></ul><div class="save_code tracking-ad" data-mod="popu_249" style="display: none;"><a href="javascript:;"><img src="http://static.blog.csdn.net/images/save_snippets.png"></a></div><ul class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li></ul></pre><p>(3)属性不同</p><p>使用dir()函数返回参数的属性、方法列表。如果参数包含方法<strong>dir</strong>()，该方法将被调用。如果参数不包含<strong>dir</strong>()，该方法将最大限度地收集参数信息。</p><pre class="prettyprint" name="code"><code class="hljs rust has-numbering"><span class="hljs-keyword">dir</span>(None)[<span class="hljs-string">'__bool__'</span>, <span class="hljs-string">'__class__'</span>, <span class="hljs-string">'__delattr__'</span>, <span class="hljs-string">'__dir__'</span>, <span class="hljs-string">'__doc__'</span>, <span class="hljs-string">'__eq__'</span>, <span class="hljs-string">'__format__'</span>, <span class="hljs-string">'__ge__'</span>, <span class="hljs-string">'__getattribute__'</span>, <span class="hljs-string">'__gt__'</span>, <span class="hljs-string">'__hash__'</span>, <span class="hljs-string">'__init__'</span>, <span class="hljs-string">'__le__'</span>, <span class="hljs-string">'__lt__'</span>, <span class="hljs-string">'__ne__'</span>, <span class="hljs-string">'__new__'</span>, <span class="hljs-string">'__reduce__'</span>, <span class="hljs-string">'__reduce_ex__'</span>, <span class="hljs-string">'__repr__'</span>, <span class="hljs-string">'__setattr__'</span>, <span class="hljs-string">'__sizeof__'</span>, <span class="hljs-string">'__str__'</span>, <span class="hljs-string">'__subclasshook__'</span>]</code><ul class="pre-numbering"><li>1</li><li>2</li></ul><div class="save_code tracking-ad" data-mod="popu_249"><a href="javascript:;"><img src="http://static.blog.csdn.net/images/save_snippets.png"></a></div><ul class="pre-numbering"><li>1</li><li>2</li></ul></pre><pre class="prettyprint" name="code"><code class="hljs rust has-numbering"><span class="hljs-keyword">dir</span>(<span class="hljs-string">''</span>)[<span class="hljs-string">'__add__'</span>, <span class="hljs-string">'__class__'</span>, <span class="hljs-string">'__contains__'</span>, <span class="hljs-string">'__delattr__'</span>, <span class="hljs-string">'__dir__'</span>, <span class="hljs-string">'__doc__'</span>, <span class="hljs-string">'__eq__'</span>, <span class="hljs-string">'__format__'</span>, <span class="hljs-string">'__ge__'</span>, <span class="hljs-string">'__getattribute__'</span>, <span class="hljs-string">'__getitem__'</span>, <span class="hljs-string">'__getnewargs__'</span>, <span class="hljs-string">'__gt__'</span>, <span class="hljs-string">'__hash__'</span>, <span class="hljs-string">'__init__'</span>, <span class="hljs-string">'__iter__'</span>, <span class="hljs-string">'__le__'</span>, <span class="hljs-string">'__len__'</span>, <span class="hljs-string">'__lt__'</span>, <span class="hljs-string">'__mod__'</span>, <span class="hljs-string">'__mul__'</span>, <span class="hljs-string">'__ne__'</span>, <span class="hljs-string">'__new__'</span>, <span class="hljs-string">'__reduce__'</span>, <span class="hljs-string">'__reduce_ex__'</span>, <span class="hljs-string">'__repr__'</span>, <span class="hljs-string">'__rmod__'</span>, <span class="hljs-string">'__rmul__'</span>, <span class="hljs-string">'__setattr__'</span>, <span class="hljs-string">'__sizeof__'</span>, <span class="hljs-string">'__str__'</span>, <span class="hljs-string">'__subclasshook__'</span>, <span class="hljs-string">'capitalize'</span>, <span class="hljs-string">'casefold'</span>, <span class="hljs-string">'center'</span>, <span class="hljs-string">'count'</span>, <span class="hljs-string">'encode'</span>, <span class="hljs-string">'endswith'</span>, <span class="hljs-string">'expandtabs'</span>, <span class="hljs-string">'find'</span>, <span class="hljs-string">'format'</span>, <span class="hljs-string">'format_map'</span>, <span class="hljs-string">'index'</span>, <span class="hljs-string">'isalnum'</span>, <span class="hljs-string">'isalpha'</span>, <span class="hljs-string">'isdecimal'</span>, <span class="hljs-string">'isdigit'</span>, <span class="hljs-string">'isidentifier'</span>, <span class="hljs-string">'islower'</span>, <span class="hljs-string">'isnumeric'</span>, <span class="hljs-string">'isprintable'</span>, <span class="hljs-string">'isspace'</span>, <span class="hljs-string">'istitle'</span>, <span class="hljs-string">'isupper'</span>, <span class="hljs-string">'join'</span>, <span class="hljs-string">'ljust'</span>, <span class="hljs-string">'lower'</span>, <span class="hljs-string">'lstrip'</span>, <span class="hljs-string">'maketrans'</span>, <span class="hljs-string">'partition'</span>, <span class="hljs-string">'replace'</span>, <span class="hljs-string">'rfind'</span>, <span class="hljs-string">'rindex'</span>, <span class="hljs-string">'rjust'</span>, <span class="hljs-string">'rpartition'</span>, <span class="hljs-string">'rsplit'</span>, <span class="hljs-string">'rstrip'</span>, <span class="hljs-string">'split'</span>, <span class="hljs-string">'splitlines'</span>, <span class="hljs-string">'startswith'</span>, <span class="hljs-string">'strip'</span>, <span class="hljs-string">'swapcase'</span>, <span class="hljs-string">'title'</span>, <span class="hljs-string">'translate'</span>, <span class="hljs-string">'upper'</span>, <span class="hljs-string">'zfill'</span>]</code><ul class="pre-numbering"><li>1</li><li>2</li></ul><div class="save_code tracking-ad" data-mod="popu_249" style="display: none;"><a href="javascript:;"><img src="http://static.blog.csdn.net/images/save_snippets_01.png"></a></div><ul class="pre-numbering"><li>1</li><li>2</li></ul></pre><h2 id="总结"><a name="t3"></a>总结：</h2><p>本文解释了None与 NULL(即空字符)的区别,以及Python中对象，类的概念，以及type()，dir()函数的使用。</p></div>
0 0
