python 正则

1.正则有三种匹配方法

import re
re.match #从开始位置开始匹配，如果开头没有则无

re.search #搜索整个字符串

re.findall #搜索整个字符串，返回一个list

2.'|'  或规则

import re

s = 'I have a dog , I have a cat ,I have a dog'
r = re.findall(r'I have a (dog|cat)',s)
for i in r:print i
'''
dog
cat
dog
[Finished in 0.2s]
'''
r = re.findall(r'I have a (?:dog|cat)',s)
for i in r:print i
'''
I have a dog
I have a cat
I have a dog
[Finished in 0.2s]
'''

 --------实例------------

import re

data = '''<div class="ntes-nav-select-pop">
<ul class="ntes-nav-select-list clearfix">
<li data-module-name="n_topnavapplist_t_0">
<a href="http://m.163.com/newsapp/#f=topnav"><span><em class="ntes-nav-app-newsapp">网易新闻</em></span></a>'''

r = re.findall(r'(?:class=".+?"|href=".+?")',data)
for i in r:print i
'''
class="ntes-nav-select-pop"
class="ntes-nav-select-list clearfix"
href="http://m.163.com/newsapp/#f=topnav"
'''