概述
http://docs.python.org/3/library/re.html
代码：
import re
line = "Fat cats are smarter than dogs, is it right?"
m = re.match( r'(.*) are (.*?) ', line)
print ("匹配的结果: ", m)
print ("匹配的起始与终点: ", m.span())
print ('匹配的整句话', m.group(0))
print ('匹配的第一个结果', m.group(1))
print ('匹配的第二个结果', m.group(2))
print ('匹配的结果列表', m.groups())
运行结果：
C:ProgramDataAnaconda3python.exe E:/python/work/ana_test/test.py
匹配的结果: <re.Match object; span=(0, 21), match='Fat cats are smarter '>
匹配的起始与终点: (0, 21)
匹配的整句话 Fat cats are smarter
匹配的第一个结果 Fat cats
匹配的第二个结果 smarter
匹配的结果列表 ('Fat cats', 'smarter')
Process finished with exit code 0
贪婪模式：
import re
m_match = re.match('[0-9]+', '12345 is the first number, 23456 is the sencond')
m_search = re.search('[0-9]+', 'The first number is 12345, 23456 is the sencond')
m_findall = re.findall('[0-9]+', '12345 is the first number, 23456 is the sencond')
print (m_match.group())
print (m_search.group())
print (m_findall)
结果：
C:ProgramDataAnaconda3python.exe E:/python/work/ana_test/test.py
12345
12345
['12345', '23456']
Process finished with exit code 0
代码：
import requests
import re
link = "http://www.santostang.com/"
headers = {'User-Agent' : 'Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.1.6) Gecko/20091201 Firefox/3.5.6'}
r = requests.get(link, headers= headers)
html = r.text
title_list = re.findall('<h1 class="post-title"><a href=.*?>(.*?)</a></h1>', html)
print (title_list)
结果：
['第四章 – 4.3 通过selenium 模拟浏览器抓取', '第四章 – 4.2 解析真实地址抓取', '第四章- 动态网页抓取 (解析真实地址 + selenium)', 'Hello world!']
代码：
import requests
from bs4 import BeautifulSoup
link = "http://www.santostang.com/"
headers = {'User-Agent' : 'Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.1.6) Gecko/20091201 Firefox/3.5.6'}
r = requests.get(link, headers= headers)
soup = BeautifulSoup(r.text,"lxml")
first_title = soup.find("h1", class_="post-title").a.text.strip()
print ("第1篇文章的标题是：", first_title)
title_list = soup.find_all("h1", class_="post-title")
for i in range(len(title_list)):
title = title_list[i].a.text.strip()
print ('第 %s 篇文章的标题是：%s' %(i+1, title))
结果:
C:ProgramDataAnaconda3python.exe E:/python/work/ana_test/test.py
第1篇文章的标题是： 第四章 – 4.3 通过selenium 模拟浏览器抓取
第 1 篇文章的标题是：第四章 – 4.3 通过selenium 模拟浏览器抓取
第 2 篇文章的标题是：第四章 – 4.2 解析真实地址抓取
第 3 篇文章的标题是：第四章- 动态网页抓取 (解析真实地址 + selenium)
第 4 篇文章的标题是：Hello world!
Process finished with exit code 0
代码：
import re
html = """
<html>
<body>
<header id="header">
<h1 id="name">
唐松Santos
</h1>
<div class="sns">
<a href="http://www.santostang.com/feed/" rel="nofollow" target="_blank" title="RSS">
<i aria-hidden="true" class="fa fa-rss">
</i>
</a>
<a href="http://weibo.com/santostang" rel="nofollow" target="_blank" title="Weibo">
<i aria-hidden="true" class="fa fa-weibo">
</i>
</a>
<a href="https://www.linkedin.com/in/santostang" rel="nofollow" target="_blank" title="Linkedin">
<i aria-hidden="true" class="fa fa-linkedin">
</i>
</a>
<a href="mailto:tangsongsky@gmail.com" rel="nofollow" target="_blank" title="envelope">
<i aria-hidden="true" class="fa fa-envelope">
</i>
</a>
</div>
<div class="nav">
<ul>
<li>
<a href="http://www.santostang.com/">
首页
</a>
</li>
<li>
<a href="http://www.santostang.com/sample-page/">
关于我
</a>
</li>
<li>
<a href="http://www.santostang.com/python%e7%bd%91%e7%bb%9c%e7%88%ac%e8%99%ab%e4%bb%a3%e7%a0%81/">
爬虫书代码
</a>
</li>
<li>
<a href="http://www.santostang.com/%e5%8a%a0%e6%88%91%e5%be%ae%e4%bf%a1/">
加我微信
</a>
</li>
<li>
<a href="https://santostang.github.io/">
EnglishSite
</a>
</li>
</ul>
</div>
</header>
</body>
</html>
"""
from bs4 import BeautifulSoup
soup = BeautifulSoup(html, "lxml")
print (soup.prettify())
print ('----------- 1 -----------n')
print (soup.header.h1)
print ('----------- 2 -----------n')
print (soup.header.div.contents)
print ('----------- 3 -----------n')
print (soup.header.div.contents[1])
print ('----------- 4 -----------n')
for child in soup.header.div.children:
print (child)
print ('----------- 5 -----------n')
for child in soup.header.div.descendants:
print(child)
print ('----------- 6 -----------n')
a_tag = soup.header.div.a
a_tag.parent
print ('----------- 7 -----------n')
soup.find_all('div', class_='sns')
print ('----------- 8 -----------n')
for tag in soup.find_all(re.compile("^h")):
print(tag.name)
print ('----------- 9 -----------n')
soup.select("header h1")
print ('----------- 10 -----------n')
print (soup.select("header > h1"))
print ('----------- 11 -----------n')
print (soup.select("div > a"))
print ('----------- 12 -----------n')
print ( soup.select('a[href^="http://www.santostang.com/"]') )
print ('----------- 13 -----------n')
结果：
C:ProgramDataAnaconda3python.exe E:/python/work/ana_test/test.py
<html>
<body>
<header id="header">
<h1 id="name">
唐松Santos
</h1>
<div class="sns">
<a href="http://www.santostang.com/feed/" rel="nofollow" target="_blank" title="RSS">
<i aria-hidden="true" class="fa fa-rss">
</i>
</a>
<a href="http://weibo.com/santostang" rel="nofollow" target="_blank" title="Weibo">
<i aria-hidden="true" class="fa fa-weibo">
</i>
</a>
<a href="https://www.linkedin.com/in/santostang" rel="nofollow" target="_blank" title="Linkedin">
<i aria-hidden="true" class="fa fa-linkedin">
</i>
</a>
<a href="mailto:tangsongsky@gmail.com" rel="nofollow" target="_blank" title="envelope">
<i aria-hidden="true" class="fa fa-envelope">
</i>
</a>
</div>
<div class="nav">
<ul>
<li>
<a href="http://www.santostang.com/">
首页
</a>
</li>
<li>
<a href="http://www.santostang.com/sample-page/">
关于我
</a>
</li>
<li>
<a href="http://www.santostang.com/python%e7%bd%91%e7%bb%9c%e7%88%ac%e8%99%ab%e4%bb%a3%e7%a0%81/">
爬虫书代码
</a>
</li>
<li>
<a href="http://www.santostang.com/%e5%8a%a0%e6%88%91%e5%be%ae%e4%bf%a1/">
加我微信
</a>
</li>
<li>
<a href="https://santostang.github.io/">
EnglishSite
</a>
</li>
</ul>
</div>
</header>
</body>
</html>
----------- 1 -----------
<h1 id="name">
唐松Santos
</h1>
----------- 2 -----------
['n', <a href="http://www.santostang.com/feed/" rel="nofollow" target="_blank" title="RSS">
<i aria-hidden="true" class="fa fa-rss">
</i>
</a>, 'n', <a href="http://weibo.com/santostang" rel="nofollow" target="_blank" title="Weibo">
<i aria-hidden="true" class="fa fa-weibo">
</i>
</a>, 'n', <a href="https://www.linkedin.com/in/santostang" rel="nofollow" target="_blank" title="Linkedin">
<i aria-hidden="true" class="fa fa-linkedin">
</i>
</a>, 'n', <a href="mailto:tangsongsky@gmail.com" rel="nofollow" target="_blank" title="envelope">
<i aria-hidden="true" class="fa fa-envelope">
</i>
</a>, 'n']
----------- 3 -----------
<a href="http://www.santostang.com/feed/" rel="nofollow" target="_blank" title="RSS">
<i aria-hidden="true" class="fa fa-rss">
</i>
</a>
----------- 4 -----------
<a href="http://www.santostang.com/feed/" rel="nofollow" target="_blank" title="RSS">
<i aria-hidden="true" class="fa fa-rss">
</i>
</a>
<a href="http://weibo.com/santostang" rel="nofollow" target="_blank" title="Weibo">
<i aria-hidden="true" class="fa fa-weibo">
</i>
</a>
<a href="https://www.linkedin.com/in/santostang" rel="nofollow" target="_blank" title="Linkedin">
<i aria-hidden="true" class="fa fa-linkedin">
</i>
</a>
<a href="mailto:tangsongsky@gmail.com" rel="nofollow" target="_blank" title="envelope">
<i aria-hidden="true" class="fa fa-envelope">
</i>
</a>
----------- 5 -----------
<a href="http://www.santostang.com/feed/" rel="nofollow" target="_blank" title="RSS">
<i aria-hidden="true" class="fa fa-rss">
</i>
</a>
<i aria-hidden="true" class="fa fa-rss">
</i>
<a href="http://weibo.com/santostang" rel="nofollow" target="_blank" title="Weibo">
<i aria-hidden="true" class="fa fa-weibo">
</i>
</a>
<i aria-hidden="true" class="fa fa-weibo">
</i>
<a href="https://www.linkedin.com/in/santostang" rel="nofollow" target="_blank" title="Linkedin">
<i aria-hidden="true" class="fa fa-linkedin">
</i>
</a>
<i aria-hidden="true" class="fa fa-linkedin">
</i>
<a href="mailto:tangsongsky@gmail.com" rel="nofollow" target="_blank" title="envelope">
<i aria-hidden="true" class="fa fa-envelope">
</i>
</a>
<i aria-hidden="true" class="fa fa-envelope">
</i>
----------- 6 -----------
----------- 7 -----------
----------- 8 -----------
html
header
h1
----------- 9 -----------
----------- 10 -----------
[<h1 id="name">
唐松Santos
</h1>]
----------- 11 -----------
[<a href="http://www.santostang.com/feed/" rel="nofollow" target="_blank" title="RSS">
<i aria-hidden="true" class="fa fa-rss">
</i>
</a>, <a href="http://weibo.com/santostang" rel="nofollow" target="_blank" title="Weibo">
<i aria-hidden="true" class="fa fa-weibo">
</i>
</a>, <a href="https://www.linkedin.com/in/santostang" rel="nofollow" target="_blank" title="Linkedin">
<i aria-hidden="true" class="fa fa-linkedin">
</i>
</a>, <a href="mailto:tangsongsky@gmail.com" rel="nofollow" target="_blank" title="envelope">
<i aria-hidden="true" class="fa fa-envelope">
</i>
</a>]
----------- 12 -----------
[<a href="http://www.santostang.com/feed/" rel="nofollow" target="_blank" title="RSS">
<i aria-hidden="true" class="fa fa-rss">
</i>
</a>, <a href="http://www.santostang.com/">
首页
</a>, <a href="http://www.santostang.com/sample-page/">
关于我
</a>, <a href="http://www.santostang.com/python%e7%bd%91%e7%bb%9c%e7%88%ac%e8%99%ab%e4%bb%a3%e7%a0%81/">
爬虫书代码
</a>, <a href="http://www.santostang.com/%e5%8a%a0%e6%88%91%e5%be%ae%e4%bf%a1/">
加我微信
</a>]
----------- 13 -----------
Process finished with exit code 0
代码：
import requests
from lxml import etree
link = "http://www.santostang.com/"
headers = {'User-Agent' : 'Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.1.6) Gecko/20091201 Firefox/3.5.6'}
r = requests.get(link, headers= headers)
html = etree.HTML(r.text)
title_list = html.xpath('//h1[@class="post-title"]/a/text()')
print (title_list)
(稍后补充)
最后
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