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学习笔记个人资源，针对基础知识列举

<link href="/image.php?url=https://csdnimg.cn/release/download_crawler_static/css/base.min.css" rel="stylesheet"/><link href="/image.php?url=https://csdnimg.cn/release/download_crawler_static/css/fancy.min.css" rel="stylesheet"/><link href="/image.php?url=https://csdnimg.cn/release/download_crawler_static/90017795/5/raw.css" rel="stylesheet"/><div id="sidebar" style="display: none"><div id="outline"></div></div><div class="pf w0 h0" data-page-no="1" id="pf1"><div class="pc pc1 w0 h0"><img alt="" class="bi x0 y0 w1 h1" src="/image.php?url=https://csdnimg.cn/release/download_crawler_static/90017795/bg1.jpg"/><div class="t m0 x1 h2 y1 ff1 fs0 fc0 sc0 ls0 ws0">Py<span class="_ _0"></span>thon<span class="_ _1"> </span><span class="ff2 sc1">基础</span></div><div class="t m0 x1 h3 y2 ff3 fs1 fc0 sc0 ls0 ws0">P<span class="ff4">ython<span class="_ _2"> </span><span class="ff5 sc1">基础</span></span></div><div class="t m0 x1 h4 y3 ff3 fs2 fc0 sc0 ls0 ws0">1</div><div class="t m0 x2 h5 y4 ff5 fs2 fc0 sc0 ls0 ws0">、</div><div class="t m0 x3 h4 y3 ff3 fs2 fc0 sc0 ls0 ws0">Python</div><div class="t m0 x4 h5 y4 ff5 fs2 fc0 sc0 ls0 ws0">是完全面向对<span class="_ _3"></span>象的语言</div><div class="t m0 x5 h5 y5 ff5 fs2 fc0 sc0 ls0 ws0">函数、模块、<span class="_ _3"></span>数字、字符串<span class="_ _3"></span>都是对象，在</div><div class="t m0 x6 h4 y6 ff3 fs2 fc0 sc0 ls0 ws0">Python</div><div class="t m0 x7 h5 y5 ff5 fs2 fc0 sc0 ls0 ws0">中一切皆对象</div><div class="t m0 x5 h5 y7 ff5 fs2 fc0 sc0 ls0 ws0">完全支持继承<span class="_ _3"></span>、重载、多重<span class="_ _3"></span>继承支持重载<span class="_ _3"></span>运算符，也支<span class="_ _3"></span>持泛型设计</div><div class="t m0 x1 h4 y8 ff3 fs2 fc0 sc0 ls0 ws0">2</div><div class="t m0 x2 h5 y9 ff5 fs2 fc0 sc0 ls0 ws0">、</div><div class="t m0 x3 h4 y8 ff3 fs2 fc0 sc0 ls0 ws0">Python</div><div class="t m0 x4 h5 y9 ff5 fs2 fc0 sc0 ls0 ws0">拥有一个强<span class="_ _3"></span>大的标准库<span class="_ _3"></span>，</div><div class="t m0 x8 h4 y8 ff3 fs2 fc0 sc0 ls0 ws0">Python</div><div class="t m0 x9 h5 y9 ff5 fs2 fc0 sc0 ls0 ws0">语言的核心<span class="_ _3"></span>只包含数字<span class="_ _3"></span>、字符串、<span class="_ _3"></span>列表、字典<span class="_ _3"></span>、</div><div class="t m0 x1 h5 ya ff5 fs2 fc0 sc0 ls0 ws0">文件等<span class="_ _3"></span>常见类<span class="_ _3"></span>型和函<span class="_ _3"></span>数，而<span class="_ _3"></span>由</div><div class="t m0 xa h4 yb ff3 fs2 fc0 sc0 ls0 ws0">Python</div><div class="t m0 xb h5 ya ff5 fs2 fc0 sc0 ls0 ws0">标准库<span class="_ _3"></span>提供了<span class="_ _3"></span>系统管<span class="_ _3"></span>理、网<span class="_ _3"></span>络通信<span class="_ _3"></span>、文<span class="_ _3"></span>本处理<span class="_ _3"></span>、数据</div><div class="t m0 x1 h5 yc ff5 fs2 fc0 sc0 ls0 ws0">库接口、图形<span class="_ _3"></span>系统、</div><div class="t m0 xc h4 yd ff3 fs2 fc0 sc0 ls0 ws0">XML</div><div class="t m0 xd h5 yc ff5 fs2 fc0 sc0 ls0 ws0">处理等额外的<span class="_ _3"></span>功能</div><div class="t m0 x1 h4 ye ff3 fs2 fc0 sc0 ls0 ws0">3</div><div class="t m0 x2 h5 yf ff5 fs2 fc0 sc0 ls0 ws0">、</div><div class="t m0 x3 h4 ye ff3 fs2 fc0 sc0 ls0 ws0">Python</div><div class="t m0 x4 h5 yf ff5 fs2 fc0 sc0 ls0 ws0">社区提供了<span class="_ _3"></span>大量的第三方<span class="_ _3"></span>模块，使用方式与标准<span class="_ _3"></span>库类似。它们的功能覆盖科学<span class="_ _3"></span>计</div><div class="t m0 x1 h5 y10 ff5 fs2 fc0 sc0 ls0 ws0">算、人工智能<span class="_ _3"></span>、机嚣学习、</div><div class="t m0 xe h4 y11 ff3 fs2 fc0 sc0 ls0 ws0">Web</div><div class="t m0 xf h5 y10 ff5 fs2 fc0 sc0 ls0 ws0">开发、数据库<span class="_ _3"></span>接口、图形系<span class="_ _3"></span>统多个领域</div><div class="t m0 x1 h6 y12 ff5 fs1 fc0 sc1 ls0 ws0">面向对象的思维方式</div><div class="t m0 x1 h4 y13 ff3 fs2 fc0 sc0 ls0 ws0">1</div><div class="t m0 x2 h5 y14 ff5 fs2 fc0 sc0 ls0 ws0">、面向对象是<span class="_ _3"></span>一种思维方式<span class="_ _3"></span>，也是一门程<span class="_ _3"></span>序设计技术</div><div class="t m0 x1 h4 y15 ff3 fs2 fc0 sc0 ls0 ws0">2</div><div class="t m0 x2 h5 y16 ff5 fs2 fc0 sc0 ls0 ws0">、<span class="_ _4"></span>要解决一个问<span class="_ _3"></span>题前，<span class="_ _4"></span>首先<span class="_ _3"></span>考虑由谁来做<span class="_ _3"></span>，<span class="_ _4"></span>怎么做事情是<span class="_ _3"></span>谁的职责，<span class="_ _0"></span>最后把事情做好就<span class="_ _3"></span>行</div><div class="t m0 x10 h4 y15 ff3 fs2 fc0 sc0 ls0 ws0">!</div><div class="t m0 x5 h5 y17 ff5 fs2 fc0 sc0 ls0 ws0">对象就是谁</div><div class="t m0 x1 h4 y18 ff3 fs2 fc0 sc0 ls0 ws0">3</div><div class="t m0 x2 h5 y19 ff5 fs2 fc0 sc0 ls0 ws0">、要解决复杂<span class="_ _3"></span>的问题，就可<span class="_ _3"></span>以找多个不同<span class="_ _3"></span>的对象，名司<span class="_ _3"></span>其收，共同实<span class="_ _3"></span>观，终完成需<span class="_ _3"></span>求</div><div class="t m0 x1 h6 y1a ff5 fs1 fc0 sc1 ls0 ws0">解释器执行原理</div><div class="t m0 x1 h4 y1b ff3 fs2 fc0 sc0 ls0 ws0">1</div><div class="t m0 x2 h5 y1c ff5 fs2 fc0 sc0 ls0 ws0">、程序运行<span class="_ _3"></span>之前，程序是<span class="_ _3"></span>保存在硬盘中<span class="_ _3"></span>的</div><div class="t m0 x1 h4 y1d ff3 fs2 fc0 sc0 ls0 ws0">2</div><div class="t m0 x2 h5 y1e ff5 fs2 fc0 sc0 ls0 ws0">、当要运行<span class="_ _3"></span>一个程序时</div><div class="t m0 x11 h5 y1f ff5 fs2 fc0 sc0 ls0 ws0">操作系统会首<span class="_ _3"></span>先让</div><div class="t m0 x12 h4 y20 ff3 fs2 fc0 sc0 ls0 ws0">CPU</div><div class="t m0 x13 h5 y1f ff5 fs2 fc0 sc0 ls0 ws0">把程序复制到<span class="_ _3"></span>内存中</div><div class="t m0 x11 h4 y21 ff3 fs2 fc0 sc0 ls0 ws0">CPU</div><div class="t m0 x14 h5 y22 ff5 fs2 fc0 sc0 ls0 ws0">执行内存中的<span class="_ _3"></span>程序代码</div><div class="t m0 x3 h5 y23 ff5 fs2 fc0 sc0 ls0 ws0">程序要执行，<span class="_ _3"></span>首先要被加载<span class="_ _3"></span>到内存</div><div class="t m0 x1 h6 y24 ff4 fs1 fc0 sc0 ls0 ws0">Python<span class="_ _2"> </span><span class="ff5 sc1">程序执行原理</span></div><div class="t m0 x1 h4 y25 ff3 fs2 fc0 sc0 ls0 ws0">1</div><div class="t m0 x2 h5 y26 ff5 fs2 fc0 sc0 ls0 ws0">、操作系统<span class="_ _3"></span>会首先让</div><div class="t m0 x15 h4 y25 ff3 fs2 fc0 sc0 ls0 ws0">CPU</div><div class="t m0 x16 h5 y26 ff5 fs2 fc0 sc0 ls0 ws0">把</div><div class="t m0 x17 h4 y25 ff3 fs2 fc0 sc0 ls0 ws0">Python</div><div class="t m0 x18 h5 y26 ff5 fs2 fc0 sc0 ls0 ws0">解释器的程序<span class="_ _3"></span>复制到内存中</div><div class="t m0 x1 h4 y27 ff3 fs2 fc0 sc0 ls0 ws0">2</div><div class="t m0 x2 h5 y28 ff5 fs2 fc0 sc0 ls0 ws0">、</div><div class="t m0 x3 h4 y27 ff3 fs2 fc0 sc0 ls0 ws0">Python</div><div class="t m0 x4 h5 y28 ff5 fs2 fc0 sc0 ls0 ws0">解释器根据语<span class="_ _3"></span>法规则，从上<span class="_ _3"></span>向下让</div><div class="t m0 x19 h4 y27 ff3 fs2 fc0 sc0 ls0 ws0">CPU</div><div class="t m0 x1a h5 y28 ff5 fs2 fc0 sc0 ls0 ws0">翻译</div><div class="t m0 x1b h4 y27 ff3 fs2 fc0 sc0 ls0 ws0">Python</div><div class="t m0 x1c h5 y28 ff5 fs2 fc0 sc0 ls0 ws0">程序中的代码</div><div class="t m0 x1 h4 y29 ff3 fs2 fc0 sc0 ls0 ws0">3</div><div class="t m0 x2 h5 y2a ff5 fs2 fc0 sc0 ls0 ws0">、</div><div class="t m0 x3 h4 y29 ff3 fs2 fc0 sc0 ls0 ws0">CPU</div><div class="t m0 x1d h5 y2a ff5 fs2 fc0 sc0 ls0 ws0">负责执行翻译<span class="_ _3"></span>完成的代码</div></div><div class="pi" data-data='{"ctm":[1.611830,0.000000,0.000000,1.611830,0.000000,0.000000]}'></div></div><div id="pf2" class="pf w0 h0" data-page-no="2"><div class="pc pc2 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="/image.php?url=https://csdnimg.cn/release/download_crawler_static/90017795/bg2.jpg"><div class="t m0 x1 h2 y2b ff2 fs0 fc0 sc1 ls0 ws0">列表、元组<span class="ff1 sc0">(tuple)</span>、字典、字符串</div><div class="t m0 x1 h6 y2c ff5 fs1 fc0 sc1 ls0 ws0">列表</div><div class="t m0 x1 h4 y2d ff3 fs2 fc0 sc0 ls0 ws0">1<span class="ff5">、列表可以<span class="_ _3"></span>嵌套；</span></div><div class="t m0 x1 h6 y2e ff5 fs1 fc0 sc1 ls0 ws0">元组</div><div class="t m0 x1 h4 y2f ff3 fs2 fc0 sc0 ls0 ws0">1<span class="ff5">、元组不同<span class="_ _3"></span>于列表的是</span>:<span class="_"> </span><span class="ff5">元组<span class="_ _3"></span>不能修改，用<span class="_ _3"></span></span>()<span class="ff5">表示；</span>(<span class="ff5">不能<span class="_ _3"></span>增删改</span>)</div><div class="t m0 x1e h4 y30 ff5 fs2 fc0 sc0 ls0 ws0">元组<span class="_ _3"></span>一般<span class="_ _3"></span>保存<span class="_ _3"></span>不同<span class="_ _3"></span>类<span class="_ _3"></span>型的<span class="_ _3"></span>数据；<span class="_ _3"></span><span class="fc1">只有<span class="_ _3"></span>一个<span class="_ _3"></span>元素<span class="_ _3"></span>的<span class="_ _3"></span>元组<span class="_ _3"></span><span class="ff3">:<span class="_ _2"> </span>single_tuple<span class="_ _2"> </span>=<span class="_ _2"> </span>(5,)<span class="_"> </span></span>，<span class="_ _3"></span>也就<span class="_ _3"></span>是<span class="_ _3"></span>说元</span></div><div class="t m0 x1e h4 y31 ff5 fs2 fc1 sc0 ls0 ws0">组中只包<span class="_ _3"></span>含一个元<span class="_ _3"></span>素时，需要<span class="_ _3"></span>在元素<span class="_ _3"></span>后面添加<span class="_ _3"></span>逗号；不<span class="_ _3"></span>能这样写<span class="_ _5"> </span><span class="ff3">single_tuple<span class="_ _2"> </span>=<span class="_ _2"> </span>(5)</span>，这</div><div class="t m0 x1e h5 y32 ff5 fs2 fc1 sc0 ls0 ws0">样是一个整形<span class="_ _3"></span>的变量<span class="fc0">；另外，<span class="_ _3"></span>创建元组也可<span class="_ _3"></span>以不加上括号<span class="_ _3"></span>；</span></div><div class="c x1f y33 w2 h7"><div class="t m0 x20 h4 y34 ff5 fs2 fc0 sc0 ls0 ws0">交互式环境中<span class="_ _3"></span>使用<span class="_ _2"> </span><span class="ff3">exit()</span>或者<span class="_ _2"> </span><span class="ff3">ctrl+D<span class="_ _6"> </span></span>退出；</div><div class="t m0 x20 h4 y35 ff3 fs2 fc0 sc0 ls0 ws0">9<span class="_ _7"> </span>//<span class="_ _7"> </span>2<span class="_ _2"> </span><span class="ff5">表示<span class="_ _3"></span>取结果的整数<span class="_ _3"></span>，乘方使用<span class="_ _3"></span></span>**<span class="ff5">；</span></div><div class="t m0 x20 h4 y36 ff5 fs2 fc0 sc0 ls0 ws0">乘法可以用在<span class="_"> </span>字符<span class="_ _3"></span>串中<span class="_"> </span>也就<span class="_ _3"></span>是说<span class="_"> </span><span class="ff3">"_<span class="_ _2"> </span>"<span class="_ _7"> </span>*<span class="_ _7"> </span>5<span class="_"> </span></span>会输出<span class="_ _6"> </span><span class="ff3">5<span class="_ _2"> </span></span>个<span class="_"> </span><span class="ff3">“_<span class="_ _3"></span>”<span class="_"> </span></span>；</div><div class="t m0 x20 h4 y37 ff5 fs2 fc0 sc0 ls0 ws0">数据<span class="_ _3"></span>类型<span class="_ _3"></span>分为<span class="_ _5"> </span>数字<span class="_ _3"></span>型和<span class="_ _3"></span>非<span class="_ _3"></span>数字型<span class="_ _3"></span><span class="ff3">:<span class="_ _7"> </span>(1)<span class="_ _3"></span></span>数<span class="_ _3"></span>字型<span class="_ _5"> </span><span class="ff3">:<span class="_"> </span></span>整<span class="_ _3"></span>形<span class="_ _3"></span>、浮点<span class="_ _3"></span>型、<span class="_ _3"></span>布尔<span class="_ _3"></span>型、<span class="_ _3"></span>复数<span class="_ _3"></span>型。<span class="_ _3"></span><span class="ff3">(2)</span>非<span class="_ _3"></span>数<span class="_ _3"></span>字</div><div class="t m0 x20 h4 y38 ff5 fs2 fc0 sc0 ls0 ws0">型<span class="ff3">:<span class="_"> </span></span>字符串、列表、元<span class="_ _3"></span>组、字典。<span class="_ _3"></span><span class="ff3">type(</span>变量<span class="_ _3"></span>名<span class="ff3">)<span class="_"> </span></span>查看变量类型；</div><div class="t m0 x20 h4 y39 ff3 fs2 fc0 sc0 ls0 ws0">python3<span class="_ _2"> </span><span class="ff5">中没<span class="_ _3"></span>有<span class="_ _2"> </span></span>long<span class="ff5">，只有<span class="_ _6"> </span></span>int<span class="ff5">；</span></div><div class="t m0 x20 h4 y3a ff5 fs2 fc0 sc0 ls0 ws0">变量的输入<span class="ff3">:<span class="_ _2"> </span>input()</span>函数。注<span class="_ _3"></span>意<span class="ff3">:<span class="_ _7"> </span>inpu<span class="_ _3"></span>t()</span>函数输入<span class="_ _3"></span>的数据类型都<span class="_ _3"></span>是字符串类型<span class="_ _3"></span>；</div><div class="t m0 x20 h4 y3b ff5 fs2 fc0 sc0 ls0 ws0">在<span class="_ _2"> </span><span class="ff3">python<span class="_ _2"> </span></span>中，<span class="_ _8"></span>如果变量名<span class="_ _3"></span>需要两个或多<span class="_ _3"></span>个单词组成<span class="_ _3"></span>时，<span class="_ _8"></span>可以按照下面的方式<span class="_ _3"></span><span class="ff3">:<span class="_"> </span></span>①每个单词都</div><div class="t m0 x20 h4 y3c ff5 fs2 fc0 sc0 ls0 ws0">是小写，单词<span class="_ _3"></span>和单词之间使<span class="_ _3"></span>用<span class="ff3">_</span>下划线连接；<span class="_ _3"></span>②使用驼峰<span class="_ _3"></span>规则；</div><div class="t m0 x20 h4 y3d ff3 fs2 fc0 sc0 ls0 ws0">print<span class="_ _2"> </span><span class="ff5">函<span class="_ _3"></span>数如<span class="_ _3"></span>果不<span class="_ _3"></span>想输<span class="_ _3"></span>出换<span class="_ _3"></span>行，<span class="_ _3"></span>在<span class="_ _3"></span>后面<span class="_ _3"></span>加<span class="_ _3"></span>上一<span class="_ _3"></span>个<span class="_ _6"> </span></span>end=""(<span class="ff5">例<span class="_ _3"></span>如<span class="_ _6"> </span></span>print(<span class="ff5">“<span class="_ _3"></span></span>a<span class="_ _3"></span><span class="ff5">”</span>,end=""<span class="_ _3"></span>)<span class="_ _7"> </span>)<span class="_ _3"></span><span class="ff5">；<span class="_ _3"></span>单纯<span class="_ _3"></span>的只</span></div><div class="t m0 x20 h4 y3e ff5 fs2 fc0 sc0 ls0 ws0">想输出一个换<span class="_ _3"></span>行可以使用<span class="_ _2"> </span><span class="ff3">print()<span class="_ _3"></span></span>或者<span class="_ _2"> </span><span class="ff3">print("")</span>；</div><div class="t m0 x20 h4 y3f ff3 fs2 fc0 sc0 ls0 ws0">\t(<span class="ff5">制表符</span>(<span class="ff5">对齐<span class="_ _3"></span></span>))<span class="ff5">和</span>\n<span class="_ _2"> </span><span class="ff5">转义字符<span class="_ _3"></span>；</span></div><div class="t m0 x20 h4 y40 ff5 fs2 fc0 sc0 ls0 ws0">关于函数的注<span class="_ _3"></span>释，写在函数<span class="_ _3"></span>的下面，加上<span class="_ _3"></span>三个<span class="ff3">"""</span>。以<span class="_ _3"></span>及文档注释（<span class="_ _3"></span>段落注释）单行<span class="_ _3"></span>用<span class="ff3">”#”;</span></div><div class="t m0 x20 h4 y41 ff5 fs2 fc0 sc0 ls0 ws0">因为函数体相<span class="_ _3"></span>对比较独立，<span class="_ _3"></span>函数定义的上<span class="_ _3"></span>方，应该和其<span class="_ _3"></span>他代码<span class="ff3">(</span>包括注释<span class="_ _3"></span><span class="ff3">)</span>保留两个空行<span class="_ _3"></span>；</div><div class="t m0 x20 h4 y42 ff3 fs2 fc0 sc0 ls0 ws0">import<span class="_ _7"> </span><span class="ff5">导入的文件可以<span class="_ _7"> </span></span>python<span class="_ _7"> </span><span class="ff5">解释器将模块<span class="_ _3"></span>解释成一个<span class="_ _7"> </span></span>pyc<span class="_ _9"> </span><span class="ff5">二进制文件</span>(<span class="_ _3"></span><span class="ff5">类似<span class="_ _9"> </span></span>Java<span class="_ _9"> </span><span class="ff5">的</span>.class?)<span class="ff5">；</span></div><div class="t m0 x20 h4 y43 ff3 fs2 fc0 sc0 ls0 ws0">python<span class="_ _2"> </span><span class="ff5">中关键字<span class="_ _3"></span>后面不需要加<span class="_ _3"></span>括号</span>(<span class="ff5">如<span class="_ _2"> </span></span>del<span class="_"> </span><span class="ff5">关键<span class="_ _3"></span>字</span>)<span class="ff5">；</span></div><div class="t m0 x20 h4 y44 ff5 fs2 fc0 sc0 ls0 ws0">方法和函数<span class="_ _3"></span>的异同<span class="ff3">:<span class="_ _7"> </span>①</span>方<span class="_ _3"></span>法和函数<span class="_ _3"></span>类似，<span class="_ _8"></span>同样是封装了独<span class="_ _3"></span>立的功能；<span class="_ _8"></span><span class="ff3">②<span class="ff5">方法需<span class="_ _3"></span>要通过对象来</span></span></div><div class="t m0 x20 h4 y45 ff5 fs2 fc0 sc0 ls0 ws0">调用，<span class="_ _a"></span>表示针对这<span class="_ _3"></span>个对象要做的<span class="_ _3"></span>操作<span class="ff3">③<span class="_ _3"></span></span>函数需要记<span class="_ _3"></span>住，<span class="_ _a"></span>但是方法是<span class="_ _3"></span>对象的<span class="ff3">"</span>函数<span class="ff3">"<span class="_ _3"></span></span>，<span class="_ _a"></span>方法不需</div><div class="t m0 x20 h4 y46 ff5 fs2 fc0 sc0 ls0 ws0">要记住<span class="ff3">(IDE<span class="_ _2"> </span></span>提示<span class="_ _3"></span>或者<span class="_ _2"> </span><span class="ff3">IPyt<span class="_ _3"></span>hon<span class="_ _2"> </span></span>中<span class="_ _2"> </span><span class="ff3">T<span class="_ _4"></span>AB<span class="_ _2"> </span><span class="ff5">补全</span>)<span class="_ _3"></span><span class="ff5">；</span></span></div><div class="t m0 x20 h4 y47 ff5 fs2 fc0 sc0 ls0 ws0">变量赋值的几<span class="_ _3"></span>种特殊的方式<span class="_ _3"></span><span class="ff3">:</span></div><div class="t m0 x20 h4 y48 ff3 fs2 fc0 sc0 ls0 ws0">a<span class="_ _7"> </span>=<span class="_ _7"> </span>b<span class="_ _2"> </span>=<span class="_ _7"> </span>c<span class="_ _7"> </span>=<span class="_ _2"> </span>1<span class="_ _b"> </span>#<span class="_"> </span><span class="ff5">三个都是<span class="_ _6"> </span></span>1</div><div class="t m0 x20 h4 y49 ff3 fs2 fc0 sc0 ls0 ws0">a,<span class="_ _7"> </span>b,<span class="_ _7"> </span>c<span class="_ _2"> </span>=<span class="_ _7"> </span>1,<span class="_ _2"> </span>2,<span class="_ _7"> </span>"hello"<span class="_ _c"> </span>#<span class="_ _7"> </span>a<span class="_ _7"> </span>=<span class="_ _2"> </span>1,<span class="_ _7"> </span>b<span class="_ _2"> </span>=<span class="_ _7"> </span>2,<span class="_ _7"> </span>c<span class="_ _2"> </span>=<span class="_ _7"> </span>"hello"</div><div class="t m0 x20 h4 y4a ff3 fs2 fc0 sc0 ls0 ws0">a,<span class="_ _7"> </span>b<span class="_ _7"> </span>=<span class="_ _2"> </span>0,<span class="_ _7"> </span>1</div><div class="t m0 x20 h4 y4b ff3 fs2 fc0 sc0 ls0 ws0">a,<span class="_ _7"> </span>b<span class="_ _7"> </span>=<span class="_ _2"> </span>b,<span class="_ _7"> </span>a+b<span class="_ _c"> </span>#<span class="_"> </span><span class="ff5">右边表达式的执行<span class="_ _3"></span>顺序是从左往<span class="_ _3"></span>右的。</span></div><div class="t m0 x20 h4 y4c ff3 fs2 fc0 sc0 ls0 ws0">print(a)<span class="_ _b"> </span>#<span class="_ _7"> </span>1</div><div class="t m0 x20 h4 y4d ff3 fs2 fc0 sc0 ls0 ws0">print(b)<span class="_ _b"> </span>#<span class="_ _7"> </span>1</div><div class="t m0 x20 h4 y4e ff5 fs2 fc0 sc0 ls0 ws0">逻辑运算符<span class="ff3">:and<span class="_ _3"></span></span>、<span class="ff3">or</span>、<span class="ff3">not</span>，成<span class="_ _3"></span>员运算符<span class="_ _2"> </span><span class="ff3">in<span class="_ _3"></span></span>、<span class="ff3">not<span class="_ _7"> </span>in<span class="_ _3"></span></span>，身份运算符<span class="_ _6"> </span><span class="ff3">is</span>、<span class="ff3">is<span class="_ _2"> </span>not</span>；</div></div><div class="c x21 y4f w3 h8"><div class="t m0 x20 h4 y50 ff3 fs2 fc0 sc0 ls0 ws0">x<span class="_ _7"> </span>=<span class="_ _7"> </span>[['a',<span class="_ _2"> </span>'b',<span class="_ _2"> </span>'c'],<span class="_ _7"> </span>[1,<span class="_ _7"> </span>2,<span class="_ _2"> </span>3]]</div><div class="t m0 x20 h4 y51 ff3 fs2 fc0 sc0 ls0 ws0">print(x[0])<span class="_ _b"> </span>#<span class="_ _7"> </span>[<span class="_ _3"></span>'a',<span class="_ _7"> </span>'b',<span class="_ _2"> </span>'c']</div><div class="t m0 x20 h4 y52 ff3 fs2 fc0 sc0 ls0 ws0">print(x[0][1])<span class="_ _b"> </span>#<span class="_ _2"> </span>'b'</div></div></div><div class="pi" data-data='{"ctm":[1.611830,0.000000,0.000000,1.611830,0.000000,0.000000]}'></div></div><div id="pf3" class="pf w0 h0" data-page-no="3"><div class="pc pc3 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="/image.php?url=https://csdnimg.cn/release/download_crawler_static/90017795/bg3.jpg"><div class="t m0 x1 h4 y53 ff3 fs2 fc0 sc0 ls0 ws0">2<span class="ff5">、元组的<span class="_ _3"></span>用途</span>:<span class="_ _2"> </span>①<span class="_"> </span><span class="ff5">作为函<span class="_ _3"></span>数的<span class="_ _3"></span>参数和返<span class="_ _3"></span>回值；</span>②<span class="ff5">格<span class="_ _3"></span>式化字<span class="_ _3"></span>符串</span>(<span class="ff5">格式字<span class="_ _3"></span>符串<span class="_ _3"></span>本身就是<span class="_ _3"></span>一个</span></div><div class="t m0 x1e h4 y54 ff5 fs2 fc0 sc0 ls0 ws0">元组<span class="ff3">)</span>；③让列<span class="_ _3"></span>表不可以被修<span class="_ _3"></span>改，保护数据<span class="_ _3"></span>安全；</div><div class="t m0 x1e h4 y55 ff5 fs2 fc0 sc0 ls0 ws0">格式化字符串<span class="_ _3"></span>和元组的关系<span class="_ _3"></span>，看下面的三<span class="_ _3"></span>个<span class="_ _2"> </span><span class="ff3">print<span class="_ _2"> </span></span>输出是一样的<span class="_ _3"></span><span class="ff3">:</span></div><div class="t m0 x1 h4 y56 ff3 fs2 fc0 sc0 ls0 ws0">3<span class="ff5">、<span class="_ _8"></span>元<span class="_ _3"></span>组和列表可<span class="_ _3"></span>以相互转换<span class="_"> </span><span class="ff3">:<span class="_ _2"> </span>①</span>使用<span class="_ _6"> </span><span class="ff3">list(</span>元组<span class="ff3">)</span>将元组<span class="_ _3"></span>转换成列表<span class="_ _3"></span>；<span class="_ _8"></span><span class="ff3">②<span class="_ _3"></span><span class="ff5">使用<span class="_ _2"> </span></span>tuple<span class="_ _2"> </span><span class="ff5">将<span class="_ _3"></span>列表转</span></span></span></div><div class="t m0 x1e h5 y57 ff5 fs2 fc0 sc0 ls0 ws0">换成元组；</div><div class="t m0 x1 h6 y58 ff5 fs1 fc0 sc1 ls0 ws0">字典</div><div class="t m0 x1 h4 y59 ff3 fs2 fc0 sc0 ls0 ws0">1<span class="ff5">、<span class="_ _0"></span>字典：<span class="ff3">①</span>键必须是唯<span class="_ _3"></span>一的<span class="_"> </span><span class="ff3">②</span>值可以<span class="_ _3"></span>取任意类型<span class="_ _3"></span>，但是键只能使用字符<span class="_ _3"></span>串、<span class="_ _0"></span>数字或者元</span></div><div class="t m0 x22 h4 y5a ff5 fs2 fc0 sc0 ls0 ws0">组<span class="ff3">(</span>键是不可<span class="_ _3"></span>变类型<span class="ff3">)</span>。</div><div class="t m0 x23 h4 y5b ff5 fs2 fc0 sc0 ls0 ws0">遍历字典<span class="_ _3"></span>的时候<span class="_ _2"> </span><span class="ff3">for<span class="_ _2"> </span>k<span class="_ _7"> </span>in<span class="_ _7"> </span>dict<span class="_ _5"> </span></span>中的<span class="_ _2"> </span><span class="ff3">k<span class="_ _6"> </span></span>是键，<span class="_ _d"></span>而不是值<span class="_ _3"></span>。<span class="_ _e"></span>（普通的<span class="_ _2"> </span><span class="ff3">for</span>）<span class="_ _d"></span>，<span class="_ _f"></span>不过也可<span class="_ _3"></span>以通过<span class="_ _2"> </span><span class="ff3">items()</span></div><div class="t m0 x23 h4 y5c ff5 fs2 fc0 sc0 ls0 ws0">方法遍历键值<span class="_ _3"></span>对<span class="ff3">:</span></div><div class="t m0 x23 h4 y5d ff5 fs2 fc0 sc0 ls0 ws0">字符串<span class="_ _3"></span>中的转义<span class="_ _3"></span>字符<span class="_ _3"></span>：<span class="ff3">\n<span class="_ _2"> </span></span>表<span class="_ _3"></span>示换行，<span class="_ _3"></span>而<span class="ff3">\r<span class="_ _6"> </span></span>表示回<span class="_ _3"></span>车，字符<span class="_ _3"></span>串中<span class="_ _3"></span>的函数<span class="_ _2"> </span><span class="ff3">isspa<span class="_ _3"></span>ce()<span class="_"> </span></span>判断<span class="_ _3"></span>的时</div><div class="t m0 x23 h4 y5e ff5 fs2 fc0 sc0 ls0 ws0">候<span class="ff3">\t\n\<span class="_ _3"></span>r<span class="_ _2"> </span></span>都是表示的空白字<span class="_ _3"></span>符；</div><div class="t m0 x23 h4 y5f ff3 fs2 fc0 sc0 ls0 ws0">isdecimla()<span class="_ _3"></span><span class="ff5">、</span>isdigit()<span class="_ _3"></span><span class="ff5">、</span>isnumeric()<span class="ff5">都不<span class="_ _3"></span>能判断字符串<span class="_ _3"></span>中的小数</span>(<span class="_ _3"></span><span class="ff5">可以判断字符<span class="_ _3"></span>串中的整数<span class="_ _3"></span></span>)<span class="ff5">；</span></div><div class="t m0 x23 h4 y60 ff5 fs2 fc0 sc0 ls0 ws0">集合<span class="_ _6"> </span><span class="ff3">set<span class="_ _2"> </span></span>的<span class="_ _3"></span>使用<span class="_ _3"></span><span class="ff3">:<span class="_"> </span></span>可<span class="_ _3"></span>以<span class="_ _3"></span>使用<span class="_ _3"></span>大括<span class="_ _3"></span>号<span class="_ _5"> </span><span class="ff3">{<span class="_ _2"> </span>}<span class="_"> </span></span>或者<span class="_ _5"> </span><span class="ff3">set(<span class="_ _3"></span>)<span class="_"> </span></span>函<span class="_ _3"></span>数创<span class="_ _3"></span>建集<span class="_ _3"></span>合<span class="_ _3"></span>，注意<span class="_ _3"></span>：创<span class="_ _3"></span>建<span class="_ _3"></span>一个<span class="_ _3"></span>空<span class="_ _3"></span>集合</div><div class="t m0 x23 h4 y61 ff5 fs2 fc0 sc0 ls0 ws0">必<span class="_ _10"></span>须<span class="_ _10"></span>用<span class="_ _11"> </span><span class="ff3">set()<span class="_ _12"> </span></span>而<span class="_ _10"></span>不<span class="_ _10"></span>是<span class="_ _10"></span><span class="ff3">{<span class="_ _6"> </span>}<span class="_ _10"></span></span>，<span class="_ _10"></span>因<span class="_ _10"></span>为<span class="_ _10"></span><span class="ff3">{<span class="_ _6"> </span>}<span class="_ _10"></span></span>是<span class="_ _10"></span>用<span class="_ _10"></span>来<span class="_ _3"></span>创<span class="_ _10"></span>建<span class="_ _10"></span>一<span class="_ _10"></span>个<span class="_ _10"></span>空<span class="_ _10"></span>字<span class="_ _10"></span>典<span class="_ _10"></span>。<span class="_ _11"> </span>集<span class="_ _10"></span>合<span class="_ _10"></span>还<span class="_ _10"></span>有<span class="_ _10"></span>一<span class="_ _10"></span>些<span class="_ _10"></span>方<span class="_ _10"></span>法<span class="_ _13"> </span><span class="ff3">add()<span class="_ _10"></span></span>、</div><div class="t m0 x23 h4 y62 ff3 fs2 fc0 sc0 ls0 ws0">update()<span class="ff5">、</span>pop()<span class="ff5">等；</span></div><div class="c x24 y63 w4 h9"><div class="t m0 x20 h4 y64 ff3 fs2 fc0 sc0 ls0 ws0">tup<span class="_ _7"> </span>=<span class="_ _2"> </span>"a",<span class="_ _7"> </span>"b",<span class="_ _2"> </span>"c",<span class="_ _7"> </span>"d"</div><div class="t m0 x20 h4 y65 ff3 fs2 fc0 sc0 ls0 ws0">print(tup)<span class="_ _b"> </span>#('a',<span class="_ _2"> </span>'b',<span class="_ _7"> </span>'c',<span class="_ _2"> </span>'d')</div><div class="t m0 x20 h4 y66 ff3 fs2 fc0 sc0 ls0 ws0">print(type(tup))<span class="_ _c"> </span>#<class<span class="_ _7"> </span>'tup<span class="_ _3"></span>le'></div><div class="t m0 x20 h4 y67 ff3 fs2 fc0 sc0 ls0 ws0">tup2<span class="_ _7"> </span>=<span class="_ _2"> </span>("a",)<span class="_ _b"> </span>#<span class="_"> </span><span class="ff5">一个<span class="_ _3"></span>元素的元组<span class="_ _5"> </span></span>(<span class="ff5">后面必须加上一个<span class="_ _3"></span>逗号</span>)</div><div class="t m0 x20 h4 y68 ff3 fs2 fc0 sc0 ls0 ws0">print(tup2)<span class="_ _b"> </span>#<span class="_ _3"></span>('a',)</div><div class="t m0 x20 h4 y69 ff3 fs2 fc0 sc0 ls0 ws0">print(type(tup2<span class="_ _3"></span>))<span class="_ _b"> </span>#<class<span class="_ _2"> </span>'tuple'></div></div><div class="c x21 y6a w5 ha"><div class="t m0 x20 h4 y6b ff3 fs2 fc0 sc0 ls0 ws0">#</div><div class="t m0 x25 h5 y6c ff5 fs2 fc0 sc0 ls0 ws0">元组和格式化<span class="_ _3"></span>字符串的关系</div><div class="t m0 x20 h4 y6d ff3 fs2 fc0 sc0 ls0 ws0">info_tuple<span class="_ _7"> </span>=<span class="_ _7"> </span>("</div><div class="t m0 x26 h5 y6e ff5 fs2 fc0 sc0 ls0 ws0">小明</div><div class="t m0 x27 h4 y6d ff3 fs2 fc0 sc0 ls0 ws0">",<span class="_ _7"> </span>21,<span class="_ _2"> </span>1.85)</div><div class="t m0 x20 h4 y6f ff3 fs2 fc0 sc0 ls0 ws0">print("%s</div><div class="t m0 x28 h5 y70 ff5 fs2 fc0 sc0 ls0 ws0">年龄是</div><div class="t m0 x27 h4 y6f ff3 fs2 fc0 sc0 ls0 ws0">%d</div><div class="t m0 x29 h5 y70 ff5 fs2 fc0 sc0 ls0 ws0">身高是</div><div class="t m0 x2a h4 y6f ff3 fs2 fc0 sc0 ls0 ws0">%.2f"<span class="_ _7"> </span>%<span class="_ _2"> </span>("</div><div class="t m0 x2b h5 y70 ff5 fs2 fc0 sc0 ls0 ws0">小明</div><div class="t m0 x2c h4 y6f ff3 fs2 fc0 sc0 ls0 ws0">",<span class="_ _7"> </span>21,<span class="_ _2"> </span>1.85))</div><div class="t m0 x20 h4 y71 ff3 fs2 fc0 sc0 ls0 ws0">print("%s</div><div class="t m0 x28 h5 y72 ff5 fs2 fc0 sc0 ls0 ws0">年龄是</div><div class="t m0 x27 h4 y71 ff3 fs2 fc0 sc0 ls0 ws0">%d</div><div class="t m0 x29 h5 y72 ff5 fs2 fc0 sc0 ls0 ws0">身高是</div><div class="t m0 x2a h4 y71 ff3 fs2 fc0 sc0 ls0 ws0">%.2f"<span class="_ _7"> </span>%<span class="_ _2"> </span>info_<span class="_ _0"></span>tuple)</div><div class="t m0 x20 h4 y73 ff3 fs2 fc0 sc0 ls0 ws0">info_str<span class="_ _9"> </span>=<span class="_ _2"> </span>"%s</div><div class="t m0 x2d h5 y74 ff5 fs2 fc0 sc0 ls0 ws0">年龄是</div><div class="t m0 x21 h4 y73 ff3 fs2 fc0 sc0 ls0 ws0">%d</div><div class="t m0 x1d h5 y74 ff5 fs2 fc0 sc0 ls0 ws0">身高是</div><div class="t m0 x2e h4 y73 ff3 fs2 fc0 sc0 ls0 ws0">%.2f"<span class="_ _2"> </span>%<span class="_ _7"> </span>info_tuple</div><div class="t m0 x20 h4 y75 ff3 fs2 fc0 sc0 ls0 ws0">print(info_str<span class="_ _0"></span>)</div></div><div class="c x2f y76 w6 hb"><div class="t m0 x20 h4 y77 ff3 fs2 fc0 sc0 ls0 ws0">dict_student<span class="_ _7"> </span>=<span class="_ _2"> </span>{'name':<span class="_ _2"> </span>'xiaoming',<span class="_ _2"> </span>'age':<span class="_ _7"> </span>'18',<span class="_ _2"> </span>'qq':<span class="_ _7"> </span>"123<span class="_ _3"></span>4"}</div><div class="t m0 x20 h4 y78 ff3 fs2 fc0 sc0 ls0 ws0">#</div><div class="t m0 x25 h5 y79 ff5 fs2 fc1 sc0 ls0 ws0">遍历方式一</div><div class="t m0 x20 h4 y7a ff3 fs2 fc0 sc0 ls0 ws0">for<span class="_ _9"> </span>k<span class="_ _2"> </span>in<span class="_ _7"> </span>dic<span class="_ _3"></span>t_student:<span class="_ _b"> </span>#<span class="_ _7"> </span>k</div><div class="t m0 x30 h5 y7b ff5 fs2 fc0 sc0 ls0 ws0">是</div><div class="t m0 x14 h4 y7a ff3 fs2 fc0 sc0 ls0 ws0">ke<span class="_ _0"></span>y</div><div class="t m0 x31 h5 y7b ff5 fs2 fc0 sc0 ls0 ws0">（键）</div><div class="t m0 x32 h4 y7c ff3 fs2 fc0 sc0 ls0 ws0">print(k,<span class="_ _7"> </span>end=<span class="_ _3"></span>"<span class="_ _7"> </span>")</div><div class="t m0 x32 h4 y7d ff3 fs2 fc0 sc0 ls0 ws0">print(dict_student[k<span class="_ _3"></span>])</div><div class="t m0 x20 h4 y7e ff3 fs2 fc0 sc0 ls0 ws0">#</div><div class="t m0 x25 h5 y7f ff5 fs2 fc1 sc0 ls0 ws0">遍历方式二</div><div class="t m0 x20 h4 y80 ff3 fs2 fc0 sc0 ls0 ws0">for<span class="_ _9"> </span>k<span class="_ _3"></span>,<span class="_ _7"> </span>v<span class="_ _7"> </span>in<span class="_ _2"> </span>dict_student.items():</div><div class="t m0 x32 h4 y81 ff3 fs2 fc0 sc0 ls0 ws0">print(k,<span class="_ _7"> </span>v)</div></div></div><div class="pi" data-data='{"ctm":[1.611830,0.000000,0.000000,1.611830,0.000000,0.000000]}'></div></div><div id="pf4" class="pf w0 h0" data-page-no="4"><div class="pc pc4 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="/image.php?url=https://csdnimg.cn/release/download_crawler_static/90017795/bg4.jpg"><div class="t m0 x23 h4 y82 ff4 fs2 fc0 sc0 ls0 ws0">2<span class="ff5 sc1">、相关<span class="_ _3"></span>公共方<span class="_ _3"></span>法</span>:<span class="_ _2"> </span><span class="ff3">len<span class="ff5">、</span>del<span class="ff5">、</span>max<span class="ff5">、</span>min(<span class="ff5">只会<span class="_ _3"></span>比较字典<span class="_ _3"></span>的<span class="_ _2"> </span></span>ke<span class="_ _0"></span>y)<span class="ff5">；</span>in<span class="ff5">、</span>not<span class="_ _7"> </span>in<span class="_ _2"> </span><span class="ff5">的<span class="_ _3"></span>使用</span>(<span class="_ _3"></span><span class="ff5">类似<span class="_ _3"></span>数据</span></span></div><div class="t m0 x5 h4 y83 ff5 fs2 fc0 sc0 ls0 ws0">库<span class="ff3">…)</span>；</div><div class="t m0 x23 h4 y56 ff3 fs2 fc1 sc0 ls0 ws0">pass<span class="_ _6"> </span><span class="ff5 fc0">关<span class="_ _3"></span>键字<span class="_ _3"></span>的使<span class="_ _3"></span>用<span class="ff3">:<span class="_ _5"> </span></span>比<span class="_ _3"></span>如<span class="_ _2"> </span><span class="ff3">if<span class="_ _2"> </span>…<span class="_ _5"> </span></span>下<span class="_ _3"></span>面没<span class="_ _3"></span>有<span class="_ _3"></span>写语<span class="_ _3"></span>句，<span class="_ _3"></span><span class="ff3">python<span class="_ _6"> </span></span>会<span class="_ _3"></span>提示<span class="_ _3"></span>报<span class="_ _3"></span>错，<span class="_ _3"></span>但是<span class="_ _3"></span>你<span class="_ _3"></span>可以<span class="_ _3"></span>写<span class="_ _3"></span>一个</span></div><div class="t m0 x23 h4 y57 ff3 fs2 fc0 sc0 ls0 ws0">pass<span class="_ _2"> </span><span class="ff5">就不会<span class="_ _3"></span>报错了；<span class="_ _8"></span>也就是说如果在<span class="_ _3"></span>开发程序时，<span class="_ _8"></span>不希望立即<span class="_ _3"></span>编写分支内部<span class="_ _3"></span>的代码，<span class="_ _8"></span>可以</span></div><div class="t m0 x23 h4 y84 ff5 fs2 fc0 sc0 ls0 ws0">使用<span class="_ _2"> </span><span class="ff3">pass<span class="_ _2"> </span></span>作为<span class="_ _3"></span>一个占位符；<span class="_ _3"></span>可以保证程序<span class="_ _3"></span>代码结构正确<span class="_ _3"></span>；</div><div class="t m0 x23 h4 y85 ff3 fs2 fc1 sc0 ls0 ws0">TODO<span class="_ _7"> </span><span class="ff5 fc0">关键<span class="_ _3"></span>字的使用，<span class="_ _14"></span>在编写程序框<span class="_ _3"></span>架的时候，<span class="_ _14"></span>可以用<span class="_ _2"> </span><span class="ff3">TODO<span class="_ _2"> </span></span>标示某个地方还没<span class="_ _3"></span>有做某事；</span></div><div class="c x23 y86 w7 hc"><div class="t m0 x20 h4 y87 ff3 fs2 fc0 sc0 ls0 ws0">student<span class="_ _7"> </span>=<span class="_ _7"> </span>{'T<span class="_ _4"></span>om',<span class="_ _2"> </span>'Jim',<span class="_ _7"> </span>'Mary<span class="_ _3"></span>',<span class="_ _7"> </span>'T<span class="_ _4"></span>om',<span class="_ _2"> </span>'Jack',<span class="_ _7"> </span>'Rose'}</div><div class="t m0 x20 h4 y88 ff3 fs2 fc0 sc0 ls0 ws0">print(student)<span class="_ _b"> </span>#<span class="_"> </span><span class="ff5">输出集合，重<span class="_ _3"></span>复的元素被自<span class="_ _3"></span>动去掉：</span>{'Jim<span class="_ _3"></span>',<span class="_ _7"> </span>'Mary<span class="_ _3"></span>',<span class="_ _7"> </span>'Ja<span class="_ _3"></span>ck',<span class="_ _7"> </span>'Rose',<span class="_ _2"> </span>'T<span class="_ _a"></span>om'}</div><div class="t m0 x20 h4 y89 ff3 fs2 fc0 sc0 ls0 ws0">if<span class="_ _7"> </span>'Rose'<span class="_ _7"> </span>in<span class="_ _2"> </span>student:</div><div class="t m0 x32 h4 y8a ff3 fs2 fc0 sc0 ls0 ws0">print('Rose<span class="_"> </span><span class="ff5">在集合中</span>')<span class="_ _b"> </span>#Rose<span class="_"> </span><span class="ff5">在集合中</span></div><div class="t m0 x20 h4 y8b ff3 fs2 fc0 sc0 ls0 ws0">else:</div><div class="t m0 x32 h4 y8c ff3 fs2 fc0 sc0 ls0 ws0">print('Rose<span class="_"> </span><span class="ff5">不在集合中</span>')</div><div class="t m0 x20 h4 y8d ff3 fs2 fc0 sc0 ls0 ws0">#<span class="_ _7"> </span>set<span class="_ _2"> </span><span class="ff5">可以进行集合<span class="_ _3"></span>运算</span></div><div class="t m0 x20 h4 y8e ff3 fs2 fc0 sc0 ls0 ws0">a<span class="_ _7"> </span>=<span class="_ _7"> </span>set('a<span class="_ _3"></span>bracadabra')</div><div class="t m0 x20 h4 y8f ff3 fs2 fc0 sc0 ls0 ws0">b<span class="_ _7"> </span>=<span class="_ _7"> </span>set('alaca<span class="_ _3"></span>zam')</div><div class="t m0 x20 h4 y90 ff3 fs2 fc0 sc0 ls0 ws0">print(a<span class="_ _7"> </span>-<span class="_ _7"> </span>b)<span class="_ _c"> </span>#<span class="_ _7"> </span>a<span class="_ _2"> </span><span class="ff5">和<span class="_ _2"> </span></span>b<span class="_ _6"> </span><span class="ff5">的差集</span>{'b',<span class="_ _2"> </span>'d',<span class="_ _7"> </span>'r'}</div><div class="t m0 x20 h4 y91 ff3 fs2 fc0 sc0 ls0 ws0">print(a<span class="_ _7"> </span>|<span class="_ _2"> </span>b)<span class="_ _b"> </span>#<span class="_ _7"> </span>a<span class="_ _2"> </span><span class="ff5">和<span class="_ _6"> </span></span>b<span class="_ _2"> </span><span class="ff5">的并集</span>{'b',<span class="_ _7"> </span>'l',<span class="_ _2"> </span>'c',<span class="_ _2"> </span>'d',<span class="_ _7"> </span>'z',<span class="_ _2"> </span>'m',<span class="_ _7"> </span>'a',<span class="_ _2"> </span>'r'}</div><div class="t m0 x20 h4 y92 ff3 fs2 fc0 sc0 ls0 ws0">print(a<span class="_ _7"> </span>&<span class="_ _7"> </span>b<span class="_ _3"></span>)<span class="_ _b"> </span>#<span class="_ _7"> </span>a<span class="_ _6"> </span><span class="ff5">和<span class="_ _2"> </span></span>b<span class="_ _2"> </span><span class="ff5">的交集</span>{'c',<span class="_ _2"> </span>'a'}</div><div class="t m0 x20 h4 y93 ff3 fs2 fc0 sc0 ls0 ws0">print(a<span class="_ _7"> </span>^<span class="_ _7"> </span>b<span class="_ _3"></span>)<span class="_ _b"> </span>#<span class="_ _7"> </span>a<span class="_ _2"> </span><span class="ff5">和<span class="_ _2"> </span></span>b<span class="_ _2"> </span><span class="ff5">中不<span class="_ _3"></span>同时存在的元<span class="_ _3"></span>素</span>{'b',<span class="_ _2"> </span>'m',<span class="_ _7"> </span>'l',<span class="_ _2"> </span>'r',<span class="_ _7"> </span>'d',<span class="_ _2"> </span>'z'}</div></div><div class="c x2 y94 w8 hd"><div class="t m0 x20 h5 y95 ff4 fs2 fc0 sc0 ls0 ws0">#<span class="ff5 sc1">迭代<span class="_ _3"></span>器的使用</span></div><div class="t m0 x32 h4 y96 ff5 fs2 fc0 sc0 ls0 ws0">在设计模式<span class="_ _3"></span>中<span class="_ _2"> </span><span class="ff3">iterat<span class="_ _0"></span>or<span class="_ _2"> </span><span class="ff5">模式被定义<span class="_ _3"></span>为：<span class="_ _15"></span>提供一种方<span class="_ _3"></span>法，<span class="_ _15"></span>可以按序访<span class="_ _3"></span>问某一<span class="_ _3"></span>聚合物<span class="_ _15"></span>（容</span></span></div><div class="t m0 x20 h5 y97 ff5 fs2 fc0 sc0 ls0 ws0">器）<span class="_ _a"></span>所含元<span class="_ _3"></span>素，<span class="_ _a"></span>且不暴<span class="_ _3"></span>露该聚合物的<span class="_ _3"></span>内部表达方式<span class="_ _3"></span>。<span class="_ _16"> </span>迭代器实现<span class="_ _3"></span>原理：<span class="_ _a"></span>迭代器<span class="_ _3"></span>是一种</div><div class="t m0 x20 h4 y98 ff5 fs2 fc0 sc0 ls0 ws0">行为类似指针<span class="_ _3"></span>的对象，因此<span class="_ _3"></span>迭代器实现上<span class="_ _3"></span>首先需要对<span class="_ _3"></span><span class="ff3">"<span class="_ _7"> </span>*<span class="_ _7"> </span>"<span class="_ _5"> </span></span>和<span class="_"> </span><span class="ff3">"<span class="_ _7"> </span>-<span class="_ _3"></span>><span class="_ _7"> </span>"</span>进行重载<span class="_ _3"></span>。</div><div class="t m0 x20 h4 y99 ff3 fs2 fc0 sc0 ls0 ws0">import<span class="_ _2"> </span>sys<span class="_ _b"> </span>#<span class="_"> </span><span class="ff5">引入<span class="_"> </span></span>s<span class="_ _0"></span>ys<span class="_"> </span><span class="ff5">模块</span></div><div class="t m0 x20 h4 y9a ff3 fs2 fc0 sc0 ls0 ws0">lst<span class="_ _7"> </span>=<span class="_ _7"> </span>[1,<span class="_ _2"> </span>2,<span class="_ _7"> </span>3,<span class="_ _2"> </span>4]</div><div class="t m0 x20 h4 y9b ff3 fs2 fc0 sc0 ls0 ws0">it<span class="_ _7"> </span>=<span class="_ _2"> </span>iter(lst)<span class="_ _b"> </span>#<span class="_"> </span><span class="ff5">创建迭代器对<span class="_ _3"></span>象</span></div><div class="t m0 x20 h4 y9c ff3 fs2 fc0 sc0 ls0 ws0">for<span class="_ _7"> </span>x<span class="_ _7"> </span>in<span class="_ _7"> </span>i<span class="_ _3"></span>t:<span class="_ _17"> </span>#<span class="_"> </span><span class="ff5">使用<span class="_ _2"> </span></span>for<span class="_"> </span><span class="ff5">遍历迭代器</span></div><div class="t m0 x32 h4 y9d ff3 fs2 fc0 sc0 ls0 ws0">print(x,<span class="_ _7"> </span>end=<span class="_ _3"></span>"<span class="_ _7"> </span>")</div><div class="t m0 x20 h4 y9e ff3 fs2 fc0 sc0 ls0 ws0">print()<span class="_ _b"> </span>#1<span class="_ _2"> </span>2<span class="_ _7"> </span>3<span class="_ _7"> </span>4</div><div class="t m0 x20 h4 y9f ff3 fs2 fc0 sc0 ls0 ws0">it<span class="_ _7"> </span>=<span class="_ _2"> </span>iter(lst)<span class="_ _b"> </span>#<span class="_"> </span><span class="ff5">之前那个已经<span class="_ _3"></span>到了最后了，<span class="_ _3"></span>再次获取</span></div><div class="t m0 x20 h4 ya0 ff3 fs2 fc0 sc0 ls0 ws0">while<span class="_ _7"> </span>Tr<span class="_ _0"></span>ue:<span class="_ _b"> </span>#<span class="_"> </span><span class="ff5">使用<span class="_ _2"> </span></span>next<span class="_ _7"> </span>+<span class="_ _2"> </span>while<span class="_ _2"> </span><span class="ff5">遍历</span></div><div class="t m0 x32 h4 ya1 ff3 fs2 fc0 sc0 ls0 ws0">try:</div><div class="t m0 x33 h4 ya2 ff3 fs2 fc0 sc0 ls0 ws0">print(next(it),<span class="_ _2"> </span>end="<span class="_ _7"> </span>")</div><div class="t m0 x32 h4 ya3 ff3 fs2 fc0 sc0 ls0 ws0">except<span class="_ _9"> </span>StopI<span class="_ _3"></span>tera<span class="_ _0"></span>tion:<span class="_ _b"> </span>#<span class="_"> </span><span class="ff5">防止无限循环</span></div><div class="t m0 x33 h4 ya4 ff3 fs2 fc0 sc0 ls0 ws0">sys.e<span class="_ _0"></span>xit()<span class="_ _b"> </span>#<span class="_"> </span><span class="ff5">退出程序</span></div><div class="t m0 x20 h4 ya5 ff3 fs2 fc0 sc0 ls0 ws0">print()<span class="_ _b"> </span>#1<span class="_ _2"> </span>2<span class="_ _7"> </span>3<span class="_ _7"> </span>4</div></div></div><div class="pi" data-data='{"ctm":[1.611830,0.000000,0.000000,1.611830,0.000000,0.000000]}'></div></div><div id="pf5" class="pf w0 h0" data-page-no="5"><div class="pc pc5 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="/image.php?url=https://csdnimg.cn/release/download_crawler_static/90017795/bg5.jpg"><div class="t m0 x1 h6 ya6 ff5 fs1 fc0 sc1 ls0 ws0">字符串</div><div class="t m0 x1 h3 ya7 ff3 fs1 fc0 sc0 ls0 ws0">1<span class="ff5">、字符串常<span class="_ _0"></span>用语法</span></div><div class="t m0 x23 h4 ya8 ff5 fs2 fc0 sc0 ls0 ws0">（<span class="ff3">1<span class="_ _3"></span></span>）<span class="_ _3"></span>字<span class="_ _3"></span>符<span class="_ _3"></span>串中<span class="_ _3"></span>切片<span class="_ _6"> </span><span class="ff3">slice<span class="_ _6"> </span></span>的<span class="_ _3"></span>使<span class="_ _3"></span>用<span class="_ _3"></span><span class="ff3">:<span class="_ _7"> </span>①<span class="_ _3"></span></span>类<span class="_ _3"></span>似<span class="_ _3"></span>截<span class="_ _3"></span>取，<span class="_ _3"></span>但<span class="_ _3"></span>是可<span class="_ _3"></span>以<span class="_ _3"></span>指<span class="_ _3"></span>定步<span class="_ _3"></span>长<span class="_ _3"></span>；<span class="ff3">②<span class="_ _3"></span>python<span class="_ _6"> </span></span>中<span class="_ _3"></span>支<span class="_ _3"></span>持倒</div><div class="t m0 x5 h4 ya9 ff5 fs2 fc0 sc0 ls0 ws0">序索引，最后<span class="_ _3"></span>一个是<span class="ff3">-<span class="_ _3"></span>1</span>，倒数第二个是<span class="ff3">-<span class="_ _3"></span>2…</span>；</div><div class="t m0 x23 h4 y84 ff5 fs2 fc0 sc0 ls0 ws0">（<span class="ff3">2</span>）<span class="ff3">replace()</span>实现<span class="_ _3"></span>字符替换：字<span class="_ _3"></span>符串可通过<span class="_ _3"></span><span class="ff3">[]</span>可以获取指定<span class="_ _3"></span>位置字符，但<span class="_ _3"></span>不可改变</div><div class="t m0 x23 h4 y5b ff5 fs2 fc0 sc0 ls0 ws0">（<span class="ff3">3</span>）<span class="_ _4"></span><span class="ff3">spl<span class="_ _3"></span>it()<span class="ff5">可以基<span class="_ _3"></span>于指定分隔<span class="_ _3"></span>符将字符串分<span class="_ _3"></span>隔成多个子<span class="_ _3"></span>字符串<span class="_ _4"></span>（<span class="_ _3"></span>存储到列表<span class="_ _3"></span>中）<span class="_ _4"></span>。<span class="_ _4"></span>如果不</span></span></div><div class="t m0 x23 h4 y5c ff5 fs2 fc0 sc0 ls0 ws0">指定分隔符，<span class="_ _3"></span>则默认使用空<span class="_ _3"></span>白字符（换行<span class="_ _3"></span>符<span class="ff3">/</span>空格<span class="_ _3"></span><span class="ff3">/</span>制表符）。</div><div class="t m0 x23 h4 yaa ff5 fs2 fc0 sc0 ls0 ws0">（<span class="ff3">4</span>）<span class="ff3">joi<span class="_ _3"></span>n()</span>的作用和<span class="_ _2"> </span><span class="ff3">sp<span class="_ _3"></span>lit()</span>作用刚好相反<span class="_ _3"></span>，用于将一系<span class="_ _3"></span>列子字符串用<span class="_ _3"></span>指定符号连接<span class="_ _3"></span>起来</div><div class="t m0 x23 h4 yab ff5 fs2 fc0 sc0 ls0 ws0">（<span class="ff3">5</span>）常用查<span class="_ _3"></span>找方法</div><div class="c x34 yac w9 he"><div class="t m0 x35 h5 yad ff5 fs2 fc0 sc0 ls0 ws0">方法和使用示<span class="_ _3"></span>例</div></div><div class="c x36 yac wa he"><div class="t m0 x37 h5 yad ff5 fs2 fc0 sc0 ls0 ws0">说明</div></div><div class="c x34 yae w9 he"><div class="t m0 x38 h4 yaf ff3 fs2 fc0 sc0 ls0 ws0">len(a)</div></div><div class="c x36 yae wa he"><div class="t m0 x26 h5 yb0 ff5 fs2 fc0 sc0 ls0 ws0">字符串</div><div class="t m0 x34 h4 yb1 ff3 fs2 fc0 sc0 ls0 ws0">a</div><div class="t m0 x39 h5 yb0 ff5 fs2 fc0 sc0 ls0 ws0">的长度</div></div><div class="c x34 yb2 w9 he"><div class="t m0 x3a h4 yb3 ff3 fs2 fc0 sc0 ls0 ws0">a.startswith(‘abcdef<span class="_ _0"></span>g’)</div></div><div class="c x36 yb2 wa he"><div class="t m0 x3b h5 yb4 ff5 fs2 fc0 sc0 ls0 ws0">以指定字符串<span class="_ _3"></span>开头</div></div><div class="c x34 yb5 w9 he"><div class="t m0 x3c h4 yb6 ff3 fs2 fc0 sc0 ls0 ws0">a.endswith(‘xyz<span class="_ _3"></span>’)</div></div><div class="c x36 yb5 wa he"><div class="t m0 x3b h5 yb7 ff5 fs2 fc0 sc0 ls0 ws0">以指定字符串<span class="_ _3"></span>结尾</div></div><div class="c x34 yb8 w9 he"><div class="t m0 x3d h4 yb9 ff3 fs2 fc0 sc0 ls0 ws0">a.find(‘<span class="_ _0"></span>g<span class="_ _3"></span>’)</div></div><div class="c x36 yb8 wa he"><div class="t m0 x3e h5 yba ff5 fs2 fc0 sc0 ls0 ws0">第一次出现指<span class="_ _3"></span>定字符串的位<span class="_ _3"></span>置</div></div><div class="c x34 ybb w9 he"><div class="t m0 x3f h4 ybc ff3 fs2 fc0 sc0 ls0 ws0">a.rfind(‘g<span class="_ _3"></span>’)</div></div><div class="c x36 ybb wa he"><div class="t m0 x40 h5 ybd ff5 fs2 fc0 sc0 ls0 ws0">最后一次出现<span class="_ _3"></span>指定字符串的<span class="_ _3"></span>位置</div></div><div class="c x34 ybe w9 he"><div class="t m0 x41 h4 ybf ff3 fs2 fc0 sc0 ls0 ws0">a.count(‘<span class="_ _0"></span>d’)</div></div><div class="c x36 ybe wa he"><div class="t m0 x28 h5 yad ff5 fs2 fc0 sc0 ls0 ws0">指定字符串出<span class="_ _3"></span>现了几次</div></div><div class="c x34 yc0 w9 hf"><div class="t m0 x41 h4 yc1 ff3 fs2 fc0 sc0 ls0 ws0">a.jsalnum()</div></div><div class="c x36 yc0 wa hf"><div class="t m0 x42 h5 yc2 ff5 fs2 fc0 sc0 ls0 ws0">所有字符全是<span class="_ _3"></span>数字或字母</div></div><div class="c x43 yc3 wb h10"><div class="t m0 x20 h4 yc4 ff3 fs2 fc0 sc0 ls0 ws0">#<span class="_"> </span><span class="ff5">切片的使用</span></div><div class="t m0 x20 h4 yc5 ff3 fs2 fc0 sc0 ls0 ws0">num_str<span class="_ _7"> </span>=<span class="_ _7"> </span>"<span class="_ _3"></span>12345678"</div><div class="t m0 x20 h4 yc6 ff3 fs2 fc0 sc0 ls0 ws0">print(num_str[2:6])<span class="_ _b"> </span>#<span class="_ _2"> </span>[2,5]<span class="_ _17"> </span>3456</div><div class="t m0 x20 h4 yc7 ff3 fs2 fc0 sc0 ls0 ws0">print(num_str[2:])<span class="_ _b"> </span>#<span class="_"> </span><span class="ff5">从<span class="_ _2"> </span></span>2<span class="_ _6"> </span><span class="ff5">位置到结束<span class="_ _17"> </span></span>345<span class="_ _3"></span>678</div><div class="t m0 x20 h4 yc8 ff3 fs2 fc0 sc0 ls0 ws0">print(num_str[0:6])<span class="_ _b"> </span>#<span class="_"> </span><span class="ff5">输出<span class="_ _3"></span></span>[0,5]<span class="ff5">的<span class="_ _17"> </span></span>123<span class="_ _3"></span>456</div><div class="t m0 x20 h4 yc9 ff3 fs2 fc0 sc0 ls0 ws0">print(num_str[:6])<span class="_ _b"> </span>#<span class="_"> </span><span class="ff5">一开<span class="_ _3"></span>始到<span class="_ _2"> </span></span>5<span class="_ _2"> </span><span class="ff5">的<span class="_ _17"> </span></span>123<span class="_ _3"></span>456</div><div class="t m0 x20 h4 yca ff3 fs2 fc0 sc0 ls0 ws0">print(num_str[:])<span class="_ _b"> </span>#<span class="_"> </span><span class="ff5">全部<span class="_ _3"></span>输出<span class="_ _17"> </span></span>123456<span class="_ _3"></span>78</div><div class="t m0 x20 h4 ycb ff3 fs2 fc0 sc0 ls0 ws0">print(num_str[::2])<span class="_ _b"> </span>#<span class="_ _5"> </span><span class="ff5">指定步长<span class="_ _c"> </span>第三个参数指<span class="_ _3"></span>定步长<span class="_ _17"> </span></span>1357</div><div class="t m0 x20 h4 ycc ff3 fs2 fc0 sc0 ls0 ws0">print(num_str[1::2])<span class="_ _c"> </span>#<span class="_"> </span><span class="ff5">从第一个开始<span class="_ _c"> </span>步长为<span class="_ _2"> </span></span>2<span class="_ _17"> </span>2468</div><div class="t m0 x20 h4 ycd ff3 fs2 fc0 sc0 ls0 ws0">print(num_str[-1])<span class="_ _b"> </span>#<span class="_ _5"> </span><span class="ff5">输出最后<span class="_ _3"></span>一个位置的<span class="_ _17"> </span></span>8</div><div class="t m0 x20 h4 yce ff3 fs2 fc0 sc0 ls0 ws0">print(num_str[2:-1])<span class="_ _c"> </span>#<span class="_"> </span><span class="ff5">从第二个开始到倒<span class="_ _3"></span>数第二个<span class="_ _17"> </span></span>345<span class="_ _3"></span>67</div><div class="t m0 x20 h4 ycf ff3 fs2 fc0 sc0 ls0 ws0">#<span class="_"> </span><span class="ff5">一个面试题<span class="_"> </span>逆序<span class="_ _3"></span>输出</span></div><div class="t m0 x20 h4 yd0 ff3 fs2 fc0 sc0 ls0 ws0">print(num_str[-1::-1])<span class="_ _c"> </span>#<span class="_"> </span><span class="ff5">步长为</span>-1<span class="_ _2"> </span><span class="ff5">代表<span class="_ _3"></span>向左切片，从<span class="_ _3"></span>最后一个开始<span class="_ _3"></span>切<span class="_ _17"> </span></span>8765432<span class="_ _3"></span>1</div><div class="t m0 x20 h4 yd1 ff3 fs2 fc0 sc0 ls0 ws0">print(num_str[::-1])<span class="_ _c"> </span>#87654321</div></div><div class="c x34 yd2 w4 h11"><div class="t m0 x20 h4 yd3 ff3 fs2 fc0 sc0 ls0 ws0">a<span class="_ _7"> </span>=<span class="_ _7"> </span>‘abcdefghijklmnopqrstuvwxyz’</div><div class="t m0 x20 h4 yd4 ff3 fs2 fc0 sc0 ls0 ws0">a<span class="_ _7"> </span>=<span class="_ _7"> </span>a<span class="_ _3"></span>.replace(‘<span class="_ _0"></span>c’<span class="_ _8"></span>,<span class="_ _0"></span>’<span class="ff5">高</span>’)<span class="_ _17"> </span>#‘<span class="_ _0"></span>ab<span class="_ _2"> </span><span class="ff5">高<span class="_ _2"> </span></span>defghijklmnopqrstuvwxyz’</div></div><div class="c x34 yd5 wc h12"><div class="t m0 x20 h4 yd6 ff3 fs2 fc0 sc0 ls0 ws0">a<span class="_ _7"> </span>=<span class="_ _7"> </span>“to<span class="_ _2"> </span>be<span class="_ _7"> </span>or<span class="_ _7"> </span>not<span class="_ _2"> </span>to<span class="_ _7"> </span>be”</div><div class="t m0 x20 h4 yd7 ff3 fs2 fc0 sc0 ls0 ws0">a.split()<span class="_ _b"> </span>#[‘to’<span class="_ _a"></span>,<span class="_ _4"></span>’<span class="_ _3"></span>be’<span class="_ _a"></span>,<span class="_ _4"></span>’<span class="_ _4"></span>or<span class="_ _3"></span>’<span class="_ _4"></span>,<span class="_ _4"></span>’not’<span class="_ _4"></span>,<span class="_ _a"></span>’<span class="_ _3"></span>to’<span class="_ _a"></span>,<span class="_ _a"></span>’<span class="_ _3"></span>be’]</div><div class="t m0 x20 h4 yd8 ff3 fs2 fc0 sc0 ls0 ws0">a.split(‘be’)<span class="_ _c"> </span>#[‘to’<span class="_ _a"></span>,<span class="_ _4"></span>’<span class="_ _4"></span>or<span class="_ _7"> </span>not<span class="_ _2"> </span>to’]</div></div><div class="c x34 yd9 wc h13"><div class="t m0 x20 h4 yda ff3 fs2 fc0 sc0 ls0 ws0">a<span class="_ _7"> </span>=<span class="_ _7"> </span>[‘sxt<span class="_ _3"></span>’<span class="_ _a"></span>,<span class="_ _4"></span>’<span class="_ _4"></span>sxt100’<span class="_ _4"></span>,<span class="_ _4"></span>’<span class="_ _4"></span>sxt200’<span class="_ _3"></span>]</div><div class="t m0 x20 h4 ydb ff3 fs2 fc0 sc0 ls0 ws0">‘*’<span class="_ _a"></span>.join(a)<span class="_ _b"> </span>#<span class="_ _2"> </span>’<span class="_ _4"></span>sxt*sxt100*sxt20<span class="_ _3"></span>0’</div></div></div><div class="pi" data-data='{"ctm":[1.611830,0.000000,0.000000,1.611830,0.000000,0.000000]}'></div></div>

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