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<!DOCTYPE html><html><head>
<title>0</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" href="file:///c:\Users\12783\.vscode\extensions\shd101wyy.markdown-preview-enhanced-0.6.10\node_modules\@shd101wyy\mume\dependencies\katex\katex.min.css">
<style>
/**
* prism.js Github theme based on GitHub's theme.
* @author Sam Clarke
*/
code[class*="language-"],
pre[class*="language-"] {
color: #333;
background: none;
font-family: Consolas, "Liberation Mono", Menlo, Courier, monospace;
text-align: left;
white-space: pre;
word-spacing: normal;
word-break: normal;
word-wrap: normal;
line-height: 1.4;
-moz-tab-size: 8;
-o-tab-size: 8;
tab-size: 8;
-webkit-hyphens: none;
-moz-hyphens: none;
-ms-hyphens: none;
hyphens: none;
}
/* Code blocks */
pre[class*="language-"] {
padding: .8em;
overflow: auto;
/* border: 1px solid #ddd; */
border-radius: 3px;
/* background: #fff; */
background: #f5f5f5;
}
/* Inline code */
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padding: .1em;
border-radius: .3em;
white-space: normal;
background: #f5f5f5;
}
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.token.blockquote {
color: #969896;
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color: #183691;
}
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color: #333;
}
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.token.important,
.token.keyword,
.token.rule,
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color: #a71d5d;
}
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color: #183691;
}
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color: #0086b3;
}
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color: #63a35c;
}
.token.function,
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.token.pseudo-element,
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.token.class-name,
.token.pseudo-class,
.token.id,
.token.url-reference .token.variable,
.token.attr-name {
color: #795da3;
}
.token.entity {
cursor: help;
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.token.title,
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font-weight: bold;
color: #1d3e81;
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color: #ed6a43;
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background-color: #eaffea;
color: #55a532;
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.token.deleted {
background-color: #ffecec;
color: #bd2c00;
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.token.bold {
font-weight: bold;
}
.token.italic {
font-style: italic;
}
/* JSON */
.language-json .token.property {
color: #183691;
}
.language-markup .token.tag .token.punctuation {
color: #333;
}
/* CSS */
code.language-css,
.language-css .token.function {
color: #0086b3;
}
/* YAML */
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color: #63a35c;
}
code.language-yaml {
color: #183691;
}
/* Ruby */
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color: #333;
}
/* Markdown */
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color: #795da3;
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/* Makefile */
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color: #795da3;
}
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color: #183691;
}
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color: #0086b3;
}
/* Bash */
.language-bash .token.keyword {
color: #0086b3;
}
/* highlight */
pre[data-line] {
position: relative;
padding: 1em 0 1em 3em;
}
pre[data-line] .line-highlight-wrapper {
position: absolute;
top: 0;
left: 0;
background-color: transparent;
display: block;
width: 100%;
}
pre[data-line] .line-highlight {
position: absolute;
left: 0;
right: 0;
padding: inherit 0;
margin-top: 1em;
background: hsla(24, 20%, 50%,.08);
background: linear-gradient(to right, hsla(24, 20%, 50%,.1) 70%, hsla(24, 20%, 50%,0));
pointer-events: none;
line-height: inherit;
white-space: pre;
}
pre[data-line] .line-highlight:before,
pre[data-line] .line-highlight[data-end]:after {
content: attr(data-start);
position: absolute;
top: .4em;
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min-width: 1em;
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color: hsl(24, 20%, 95%);
font: bold 65%/1.5 sans-serif;
text-align: center;
vertical-align: .3em;
border-radius: 999px;
text-shadow: none;
box-shadow: 0 1px white;
}
pre[data-line] .line-highlight[data-end]:after {
content: attr(data-end);
top: auto;
bottom: .4em;
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<div class="mume markdown-preview ">
<h1 class="mume-header" id="%E7%88%AC%E8%99%AB">爬虫</h1>
<div class="md-toc">
<details style="padding:0;;padding-left:0px;" open>
<summary class="md-toc-link-wrapper">
<a href="#爬虫" class="md-toc-link"><p>爬虫</p>
</a>
</summary>
<div>
<details style="padding:0;;padding-left:24px;" open>
<summary class="md-toc-link-wrapper">
<a href="#request库" class="md-toc-link"><p>Request库</p>
</a>
</summary>
<div>
<div class="md-toc-link-wrapper" style="padding:0;;display:list-item;list-style:square;margin-left:42px">
<a href="#response对象的属性" class="md-toc-link">
<p>Response对象的属性</p>
</a></div><div class="md-toc-link-wrapper" style="padding:0;;display:list-item;list-style:square;margin-left:42px">
<a href="#requests库异常" class="md-toc-link">
<p>Requests库异常</p>
</a></div><div class="md-toc-link-wrapper" style="padding:0;;display:list-item;list-style:square;margin-left:42px">
<a href="#搜索引擎关键词提交" class="md-toc-link">
<p>搜索引擎关键词提交</p>
</a></div>
</div>
</details>
<div class="md-toc-link-wrapper" style="padding:0;;display:list-item;list-style:square;margin-left:42px">
<a href="#robots协议" class="md-toc-link">
<p>Robots协议</p>
</a></div><details style="padding:0;;padding-left:24px;" open>
<summary class="md-toc-link-wrapper">
<a href="#beautiful-soup库" class="md-toc-link"><p>Beautiful Soup库</p>
</a>
</summary>
<div>
<div class="md-toc-link-wrapper" style="padding:0;;display:list-item;list-style:square;margin-left:42px">
<a href="#基本元素" class="md-toc-link">
<p>基本元素</p>
</a></div><div class="md-toc-link-wrapper" style="padding:0;;display:list-item;list-style:square;margin-left:42px">
<a href="#内容遍历方法" class="md-toc-link">
<p>内容遍历方法</p>
</a></div><div class="md-toc-link-wrapper" style="padding:0;;display:list-item;list-style:square;margin-left:42px">
<a href="#bs4库的prettify方法" class="md-toc-link">
<p>bs4库的prettify()方法</p>
</a></div>
</div>
</details>
<div class="md-toc-link-wrapper" style="padding:0;;display:list-item;list-style:square;margin-left:42px">
<a href="#re正则表达式库" class="md-toc-link">
<p>Re正则表达式库</p>
</a></div>
</div>
</details>
</div>
<h2 class="mume-header" id="request%E5%BA%93">Request库</h2>
<pre data-role="codeBlock" data-info="python" class="language-python"><span class="token keyword keyword-import">import</span> requests
r <span class="token operator">=</span> requests<span class="token punctuation">.</span>get<span class="token punctuation">(</span><span class="token string">"url"</span><span class="token punctuation">)</span>
</pre><h3 class="mume-header" id="response%E5%AF%B9%E8%B1%A1%E7%9A%84%E5%B1%9E%E6%80%A7">Response对象的属性</h3>
<table>
<thead>
<tr>
<th>属性</th>
<th>说明</th>
</tr>
</thead>
<tbody>
<tr>
<td>r.status_code</td>
<td>http请求的返回状态，200表示连接成功，404表示失败</td>
</tr>
<tr>
<td>r.text</td>
<td>http响应内容的字符串形式。即url对应的页面内容</td>
</tr>
<tr>
<td>r.encoding</td>
<td>从http header中猜测的响应内容编码方式</td>
</tr>
<tr>
<td>r.apparent_encoding</td>
<td>从内容中分析出的响应内容编码方式</td>
</tr>
<tr>
<td>r.content</td>
<td>http响应内容的二进制形式</td>
</tr>
</tbody>
</table>
<h3 class="mume-header" id="requests%E5%BA%93%E5%BC%82%E5%B8%B8">Requests库异常</h3>
<table>
<thead>
<tr>
<th>类型</th>
<th>说明</th>
</tr>
</thead>
<tbody>
<tr>
<td>requests.ConnectionError</td>
<td>网络连接错误异常，如DNS查询失败、拒绝连接等</td>
</tr>
<tr>
<td>requests.HTTPError</td>
<td>HTTP错误异常</td>
</tr>
<tr>
<td>requests.URLRequired</td>
<td>URL缺失异常</td>
</tr>
<tr>
<td>requests.TooManyRedirects</td>
<td>超过最大重定向次数，产生重定向异常</td>
</tr>
<tr>
<td>requests.ConnectTimeout</td>
<td>连接远程服务器超时异常</td>
</tr>
<tr>
<td>requests.Timeout</td>
<td>请求URL超时，产生超时异常</td>
</tr>
</tbody>
</table>
<pre data-role="codeBlock" data-info="python" class="language-python">r<span class="token punctuation">.</span>raise_for_status<span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token comment">#如果不是200，产生异常HTTPError</span>
</pre><h3 class="mume-header" id="%E6%90%9C%E7%B4%A2%E5%BC%95%E6%93%8E%E5%85%B3%E9%94%AE%E8%AF%8D%E6%8F%90%E4%BA%A4">搜索引擎关键词提交</h3>
<pre data-role="codeBlock" data-info="python" class="language-python">kv <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token string">'wd'</span><span class="token punctuation">:</span> keyword<span class="token punctuation">}</span>
r <span class="token operator">=</span> requests<span class="token punctuation">.</span>get<span class="token punctuation">(</span>url<span class="token punctuation">,</span>params<span class="token operator">=</span>kv<span class="token punctuation">)</span>
</pre><h2 class="mume-header" id="robots%E5%8D%8F%E8%AE%AE">Robots协议</h2>
<p>作用：网站告知网络爬虫哪些页面可以爬取，哪些不行</p>
<p>形式： 在网站根目录下的robots.txt</p>
<pre data-role="codeBlock" data-info="python" class="language-python"><span class="token comment">#当拒绝爬虫时可修改HTTP头部</span>
kv <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token string">'user-agent'</span><span class="token punctuation">:</span><span class="token string">'Mozilla/5.0'</span><span class="token punctuation">}</span>
r <span class="token operator">=</span> requests<span class="token punctuation">.</span>get<span class="token punctuation">(</span>url<span class="token punctuation">,</span>headers <span class="token operator">=</span> kv<span class="token punctuation">)</span>
</pre><h2 class="mume-header" id="beautiful-soup%E5%BA%93">Beautiful Soup库</h2>
<pre data-role="codeBlock" data-info="python" class="language-python"><span class="token keyword keyword-from">from</span> bs4 <span class="token keyword keyword-import">import</span> BeautifulSoup
soup <span class="token operator">=</span> BeautifulSoup<span class="token punctuation">(</span>demo<span class="token punctuation">,</span><span class="token string">'html.parser'</span><span class="token punctuation">)</span>
</pre><h3 class="mume-header" id="%E5%9F%BA%E6%9C%AC%E5%85%83%E7%B4%A0">基本元素</h3>
<table>
<thead>
<tr>
<th>基本元素</th>
<th>说明</th>
</tr>
</thead>
<tbody>
<tr>
<td>Tag</td>
<td>标签，最基本的信息组织单元，分别用<>和</>标明开头和结尾</td>
</tr>
<tr>
<td>Name</td>
<td>标签的名字，<p>...</p>的名字是'p',格式：<tag>.name</td>
</tr>
<tr>
<td>Attributes</td>
<td>标签的属性，字典形式组织，格式：<tag>.attrs</td>
</tr>
<tr>
<td>NavigableString</td>
<td>标签内非属性字符串，<>...</>中的字符串，格式：<tag>.string</td>
</tr>
<tr>
<td>Comment</td>
<td>标签内字符串的注释部分，一种特殊的Comment类型</td>
</tr>
</tbody>
</table>
<h3 class="mume-header" id="%E5%86%85%E5%AE%B9%E9%81%8D%E5%8E%86%E6%96%B9%E6%B3%95">内容遍历方法</h3>
<ol>
<li>标签树的下行遍历</li>
</ol>
<table>
<thead>
<tr>
<th>属性</th>
<th>说明</th>
</tr>
</thead>
<tbody>
<tr>
<td>.contents</td>
<td>子节点的列表，将<tag>所有儿子节点存入列表</td>
</tr>
<tr>
<td>.children</td>
<td>子节点的迭代类型，与.contents类似，用于循环遍历儿子节点</td>
</tr>
<tr>
<td>.descendants</td>
<td>子孙节点的迭代类型，包含所有子孙节点，用于循环遍历</td>
</tr>
</tbody>
</table>
<pre data-role="codeBlock" data-info="python" class="language-python"><span class="token keyword keyword-for">for</span> child <span class="token keyword keyword-in">in</span> soup<span class="token punctuation">.</span>body<span class="token punctuation">.</span>children<span class="token operator">/</span>descendants<span class="token punctuation">:</span>
<span class="token keyword keyword-print">print</span><span class="token punctuation">(</span>child<span class="token punctuation">)</span>
</pre><ol start="2">
<li>标签树的上行遍历</li>
</ol>
<table>
<thead>
<tr>
<th>属性</th>
<th>说明</th>
</tr>
</thead>
<tbody>
<tr>
<td>.parent</td>
<td>节点的父亲标签</td>
</tr>
<tr>
<td>.parents</td>
<td>节点先辈标签的迭代类型，用于循环遍历先辈节点</td>
</tr>
</tbody>
</table>
<ol start="3">
<li>标签树的平行遍历</li>
</ol>
<table>
<thead>
<tr>
<th>属性</th>
<th>说明</th>
</tr>
</thead>
<tbody>
<tr>
<td>.next_sibling</td>
<td>返回按照HTML文本顺序的下一个平行节点标签</td>
</tr>
<tr>
<td>.previous_sibling</td>
<td>返回按照HTML文本顺序的上一个平行节点标签</td>
</tr>
<tr>
<td>.next_siblings</td>
<td>迭代类型，返回按照HTML文本顺序的后续所有平行节点标签</td>
</tr>
<tr>
<td>.previous_siblings</td>
<td>迭代类型，返回按照HTML文本顺序的前序所有平行节点标签</td>
</tr>
</tbody>
</table>
<pre data-role="codeBlock" data-info="python" class="language-python"><span class="token keyword keyword-for">for</span> sibling <span class="token keyword keyword-in">in</span> soup<span class="token punctuation">.</span>a<span class="token punctuation">.</span>next_siblings<span class="token operator">/</span><span class="token punctuation">.</span>previous_siblings<span class="token punctuation">:</span>
<span class="token keyword keyword-print">print</span><span class="token punctuation">(</span>sibling<span class="token punctuation">)</span>
</pre><h3 class="mume-header" id="bs4%E5%BA%93%E7%9A%84prettify%E6%96%B9%E6%B3%95">bs4库的prettify()方法</h3>
<pre data-role="codeBlock" data-info="python" class="language-python"><span class="token keyword keyword-print">print</span><span class="token punctuation">(</span>soup<span class="token punctuation">.</span>prettify<span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
</pre><h3>内容查找</h3>
<pre data-role="codeBlock" data-info="python" class="language-python"> soup<span class="token punctuation">.</span>find_all<span class="token punctuation">(</span>name<span class="token punctuation">,</span>attrs<span class="token punctuation">,</span>recursive<span class="token punctuation">,</span>strinng<span class="token punctuation">,</span><span class="token operator">**</span>kwargs<span class="token punctuation">)</span>
<span class="token comment">#返回一个列表类型，存储查找的内容</span>
</pre><table>
<thead>
<tr>
<th>属性</th>
<th>说明</th>
</tr>
</thead>
<tbody>
<tr>
<td>name</td>
<td>对标签内容的检索字符串</td>
</tr>
<tr>
<td>attrs</td>
<td>对标签属性值的检索字符串，可标注属性检索</td>
</tr>
<tr>
<td>recursive</td>
<td>是否对子孙全部检索，默认为True</td>
</tr>
<tr>
<td>string</td>
<td><>...</>中字符串区域的检索字符串</td>
</tr>
</tbody>
</table>
<pre data-role="codeBlock" data-info="python" class="language-python">soup<span class="token punctuation">.</span>find_all<span class="token punctuation">(</span>string <span class="token operator">=</span> re<span class="token punctuation">.</span><span class="token builtin">compile</span><span class="token punctuation">(</span><span class="token string">"link"</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token comment">#将标签中出现link的字符串域全部检索出来</span>
</pre><pre data-role="codeBlock" data-info="python" class="language-python">soup<span class="token punctuation">(</span><span class="token punctuation">)</span> 等价于 soup<span class="token punctuation">.</span>find_all<span class="token punctuation">(</span><span class="token punctuation">)</span>
</pre><p><strong>扩展方法</strong></p>
<table>
<thead>
<tr>
<th>方法</th>
<th>说明</th>
</tr>
</thead>
<tbody>
<tr>
<td><>.find()</td>
<td>搜索且只返回一个结果，字符串类型，同.find_all()参数</td>
</tr>
<tr>
<td><>.find_parents()</td>
<td>在先辈节点中搜索，返回列表类型，同.find_all()参数</td>
</tr>
<tr>
<td><>.find_parent</td>
<td>在先辈节点中返回一个结果，字符串类型，同.find_all()参数</td>
</tr>
<tr>
<td><>.find_next_siblings()</td>
<td>在后续平行节点中搜索，返回列表类型，同.find_all()参数</td>
</tr>
<tr>
<td><>.find_next_sibling()</td>
<td>在后续平行节点中返回一个结果，字符串类型，同.find_all()参数</td>
</tr>
<tr>
<td><>.find_previous()_silbings()</td>
<td>在前序平行节点中搜索，返回列表类型，同.find_all()参数</td>
</tr>
<tr>
<td><>.find_previous_silbing()</td>
<td>在前序平行节点中返回一个结果，字符串类型，同.find_all()参数</td>
</tr>
</tbody>
</table>
<h2 class="mume-header" id="re%E6%AD%A3%E5%88%99%E8%A1%A8%E8%BE%BE%E5%BC%8F%E5%BA%93">Re正则表达式库</h2>
<p>正则表达式是用来简洁表达一组字符串的表达式<br>
<code>import re</code></p>
<h3>正则表达式的常用操作符</h3>
<table>
<thead>
<tr>
<th>操作符</th>
<th>说明</th>
<th>实例</th>
</tr>
</thead>
<tbody>
<tr>
<td>.</td>
<td>表示任何单个字符</td>
<td></td>
</tr>
<tr>
<td>[]</td>
<td>字符集，对单个字符给出取值范围</td>
<td>[abc]表示a、b、c，[a-z]表示a到z单个字符</td>
</tr>
<tr>
<td>[^]</td>
<td>非字符集，对单个字符给出排除范围</td>
<td>[^abc]表示非a或非b或c的单个字符</td>
</tr>
<tr>
<td>*</td>
<td>前一个字符0次或无限次扩展</td>
<td>abc*表示ab、abc、abcc、abccc等</td>
</tr>
<tr>
<td>+</td>
<td>前一个字符1次或无限次扩展</td>
<td>abc+表示abc、abcc等</td>
</tr>
<tr>
<td>?</td>
<td>前一个字符0或1次扩展</td>
<td>abc?表示ab、abc</td>
</tr>
<tr>
<td>|</td>
<td>左右表达式任意一个</td>
<td>abc|def表示abc、def</td>
</tr>
<tr>
<td>{m}</td>
<td>扩展前一个字符m次</td>
<td>ab{2}c表示abbc</td>
</tr>
<tr>
<td>{m,n}</td>
<td>扩展前一个字符m至n次(含n)</td>
<td>ab{1,2}c表示abc、abbc</td>
</tr>
<tr>
<td>^</td>
<td>匹配字符串开头</td>
<td>^abc表示abc且在一个字符串的开头</td>
</tr>
<tr>
<td>$</td>
<td>匹配字符串结尾</td>
<td>abc$表示abc且在一个字符串的结尾</td>
</tr>
<tr>
<td>()</td>
<td>分组标记，内部只能使用|操作符</td>
<td>(abc)表示，(abc</td>
</tr>
<tr>
<td>\d</td>
<td>数字，等价于[0-9]</td>
<td></td>
</tr>
<tr>
<td>\w</td>
<td>单词字符，等价于[A-Za-z0-9]</td>
<td></td>
</tr>
</tbody>
</table>
<p><strong>经典正则表达式实例</strong></p>
<p><code>^[A-Za-z]+$</code> 由26个字母组成的字符串<br>
<code>^[A-Za-z0-9]+$</code> 由26个字母和数字组成的字符串<br>
<code>^-?\d+$</code> 整数形式的字符串<br>
<code>^[0-9]*[1-9][0-9]*$</code> 正整数形式的字符串<br>
<code>[1-9]\d{5}</code> 中国境内邮政编码，6位<br>
<code>[\u4e00-\u9fa5]</code> 匹配中文字符<br>
<code>\d{3}-\d{8}|\d{4}-\d{7}</code>国内电话号码，010-68913536<br>
<code>(([1-9]?\d|1\d{2}|2[0-4]\d|25[0-5]).){3}([1-9]?\d|1\d{2}|2[0-4]\d|25[0-5])</code> ip地址</p>
<h3>Re库的基本使用</h3>
<ol>
<li>正则表达式的表示类型</li>
</ol>
<p>raw string类型(原生字符串类型，不包括转义符) ，表示为：r"text"<br>
例如：r"[1-9]\d{5}"</p>
<p>string类型(包括转义符)，更繁琐</p>
<ol start="2">
<li>Re库的主要功能函数</li>
</ol>
<table>
<thead>
<tr>
<th>函数</th>
<th>说明</th>
</tr>
</thead>
<tbody>
<tr>
<td>re.search(pattern,string,flags=0)</td>
<td>在一个字符串中匹配正则表达式的第一个位置，返回match对象。<code>pattern:正则表达式的字符串或原生字符串表示</code> <code>string:待匹配字符串</code> <code>flags:正则表达式使用时的控制标记</code></td>
</tr>
<tr>
<td>re.match(pattern,string,flags=0)</td>
<td>从一个字符串的开始位置起匹配正则表达式，返回match对象。<code>pattern:正则表达式的字符串或原生字符串表示</code> <code>string:待匹配字符串</code> <code>flags:正则表达式使用时的控制标记</code></td>
</tr>
<tr>
<td>re.findall(pattern,string,flags=0)</td>
<td>搜索字符串，以列表形式返回全部能匹配的子串。<code>pattern:正则表达式的字符串或原生字符串表示</code> <code>string:待匹配字符串</code> <code>flags:正则表达式使用时的控制标记</code></td>
</tr>
<tr>
<td>re.split(pattern,string,maxsplit=0,flags=0)</td>
<td>将一个字符串按照正则表达式匹配结果进行分割，返回列表类型。<code>pattern:正则表达式的字符串或原生字符串表示</code> <code>string:待匹配字符串</code> <code>maxsplit:最大分割数，剩余部分作为最后一个元素输出</code> <code>flags:正则表达式使用时的控制标记</code></td>
</tr>
<tr>
<td>re.finditer(pattern,string,flags=0)</td>
<td>搜索字符串，返回一个匹配结果的迭代类型，每个迭代元素是match对象。<code>pattern:正则表达式的字符串或原生字符串表示</code> <code>string:待匹配字符串</code> <code>flags:正则表达式使用时的控制标记</code></td>
</tr>
<tr>
<td>re.sub(pattern,repl,string,count=0,flags=0)</td>
<td>在一个字符串中替换所有匹配正则表达式的字串，返回替换后的字符串。<code>pattern:正则表达式的字符串或原生字符串表示</code> <code>repl:替换匹配字符串的字符串</code> <code>string:待匹配字符串</code> <code>count:匹配的最大替换次数</code> <code>flags:正则表达式使用时的控制标记</code></td>
</tr>
</tbody>
</table>
<ol start="3">
<li>flags:正则表达式使用时的控制标记</li>
</ol>
<table>
<thead>
<tr>
<th>常用标记</th>
<th>说明</th>
</tr>
</thead>
<tbody>
<tr>
<td>re.I re.IGNORECASE</td>
<td>忽略正则表达式的大小写，[A-Z]能够匹配小写内容</td>
</tr>
<tr>
<td>re.M re.MULTILINE</td>
<td>正则表达式中的^操作符能够将给定字符串的每行当作匹配开始</td>
</tr>
<tr>
<td>re.S re.DOTALL</td>
<td>正则表达式中的.操作符能够匹配所有字符，默认匹配除换行外的所有字符</td>
</tr>
</tbody>
</table>
<ol start="4">
<li>Re库的另一种等价用法：</li>
</ol>
<blockquote>
<p>rst = re.search(pattern,string) 函数式用法：一次性操作</p>
</blockquote>
<blockquote>
<p>pat = re.compile(pattern) 面向对象用法，编译后的多次操作<br>
rst = pat.search(string)</p>
</blockquote>
<p><strong>compile函数</strong></p>
<pre data-role="codeBlock" data-info="python" class="language-python">regex <span class="token operator">=</span> re<span class="token punctuation">.</span><span class="token builtin">compile</span><span class="token punctuation">(</span>pattern<span class="token punctuation">,</span>flags<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">)</span>
</pre><p>经过封装的<mark>regex</mark>为真正的正则表达式，可使用regex.search()等6种方法</p>
<h3>match对象</h3>
<ol>
<li>match对象的属性</li>
</ol>
<table>
<thead>
<tr>
<th>属性</th>
<th>说明</th>
</tr>
</thead>
<tbody>
<tr>
<td>.string</td>
<td>待匹配文本</td>
</tr>
<tr>
<td>.re</td>
<td>匹配时使用的pattern对象(正则表达式)</td>
</tr>
<tr>
<td>.pos</td>
<td>正则表达式搜索文本的开始位置</td>
</tr>
<tr>
<td>.endpos</td>
<td>正则表达式搜索文本的结束位置</td>
</tr>
</tbody>
</table>
<ol start="2">
<li>match对象的方法</li>
</ol>
<table>
<thead>
<tr>
<th>方法</th>
<th>说明</th>
</tr>
</thead>
<tbody>
<tr>
<td>.group(0)</td>
<td>获得匹配后的字符串</td>
</tr>
<tr>
<td>.start()</td>
<td>匹配字符串在原始字符串的开始位置</td>
</tr>
<tr>
<td>.end()</td>
<td>匹配字符串在原始字符串的结束位置</td>
</tr>
<tr>
<td>.span()</td>
<td>返回(.start(),.end())</td>
</tr>
</tbody>
</table>
<h3>贪婪匹配和最小匹配</h3>
<blockquote>
<p>贪婪匹配：Re库默认采用贪婪匹配，即输出匹配最长的字串</p>
</blockquote>
<p><strong>最小匹配操作符</strong></p>
<table>
<thead>
<tr>
<th>操作符</th>
<th>说明</th>
</tr>
</thead>
<tbody>
<tr>
<td>*?</td>
<td>前一个字符0次或无数次扩展，最小匹配</td>
</tr>
<tr>
<td>+?</td>
<td>前一次字符1次或无限次扩展，最小匹配</td>
</tr>
<tr>
<td>??</td>
<td>前一个字符0次或一次扩展，最小匹配</td>
</tr>
<tr>
<td>{m,n}?</td>
<td>扩展前一个字符m至n次，最小匹配</td>
</tr>
</tbody>
</table>
<h2>Scrapy爬虫框架</h2>
<blockquote>
<p>爬虫框架：是实现爬虫功能的一个软件结构和功能组件集合</p>
</blockquote>
<p><img src="scrapy%E7%88%AC%E8%99%AB%E6%A1%86%E6%9E%B6.png" alt="scrapy爬虫框架_1"><br>
<img src="./scrapy%E7%88%AC%E8%99%AB%E6%A1%86%E6%9E%B6_2.png" alt="scrapy爬虫框架_2"></p>
<p><mark>scrapy</mark>命令在<mark>cmd</mark>命令行中实现</p>
<pre data-role="codeBlock" data-info="cmd" class="language-cmd"><code>scrapy -h
</code></pre><blockquote>
<p>scrapy <command> [options] [args]</p>
</blockquote>
<h3>scrapy常用命令</h3>
<table>
<thead>
<tr>
<th>命令</th>
<th>说明</th>
<th>格式</th>
</tr>
</thead>
<tbody>
<tr>
<td>startproject</td>
<td>创建一个工程</td>
<td>scrapy startproject <name> [dir]</td>
</tr>
<tr>
<td>genspider</td>
<td>创建一个爬虫</td>
<td>scrapy genspider [options] <name> <domain></td>
</tr>
<tr>
<td>settings</td>
<td>获得爬虫配置信息</td>
<td>scrapy settings [options]</td>
</tr>
<tr>
<td>crawl</td>
<td>运行一个爬虫</td>
<td>scrapy crawl <spider></td>
</tr>
<tr>
<td>list</td>
<td>列出工程中所有爬虫</td>
<td>scrapy list</td>
</tr>
<tr>
<td>shell</td>
<td>启动URL调试命令行</td>
<td>scrapy shell [url]</td>
</tr>
</tbody>
</table>
<h3>爬虫实例</h3>
<pre data-role="codeBlock" data-info="cmd" class="language-cmd"><code>scrapy startproject python123demo
</code></pre><p><img src="./scrapy%E7%88%AC%E8%99%AB%E5%AE%9E%E4%BE%8B.png" alt="生成的工程目录"></p>
<h3>yield关键字</h3>
<p>yield 等价于 生成器</p>
<blockquote>
<p>生成器是一个不断产生值的函数</p>
</blockquote>
<blockquote>
<p>包含yield语句的函数是一个生成器</p>
</blockquote>
<blockquote>
<p>生成器每次产生一个值(yield语句)，函数被冻结，被唤醒后再产生一个值</p>
</blockquote>
<h3>scrapy爬虫基本使用</h3>
<p><img src="./scrapy%E7%88%AC%E8%99%AB%E5%9F%BA%E6%9C%AC%E4%BD%BF%E7%94%A8.png" alt="scrapy爬虫基本使用"></p>
<ol>
<li>Request类</li>
</ol>
<table>
<thead>
<tr>
<th>属性或方法</th>
<th>说明</th>
</tr>
</thead>
<tbody>
<tr>
<td>.url</td>
<td>Request对应的请求URL地址</td>
</tr>
<tr>
<td>.method</td>
<td>对应的请求方法,'GET''POST'等</td>
</tr>
<tr>
<td>.headers</td>
<td>字典类型风格的请求头</td>
</tr>
<tr>
<td>.body</td>
<td>请求内容主体，字符串类型</td>
</tr>
<tr>
<td>.meta</td>
<td>用户添加的扩展信息，在Scrapy内部模板间传递信息使用</td>
</tr>
<tr>
<td>.copy()</td>
<td>复制该请求</td>
</tr>
</tbody>
</table>
<ol start="2">
<li>Response类型</li>
</ol>
<table>
<thead>
<tr>
<th>属性或方法</th>
<th>说明</th>
</tr>
</thead>
<tbody>
<tr>
<td>.url</td>
<td>Response对应的请求URL地址</td>
</tr>
<tr>
<td>.status</td>
<td>HTTP状态码，默认是200</td>
</tr>
<tr>
<td>.headers</td>
<td>Response对应的头部信息</td>
</tr>
<tr>
<td>.body</td>