4.6、re.compile
re.compile 可以把正则表达式编译成一个正则对象
12 >>> help(re.compile)
compile(pattern, flags=0)

第一个参数：规则
第二个参数：标志位
实例：
>>> test="Hi, nice to meet you where are you from "
>>> k=re.compile(r'\w*o\w*') #匹配带o的字符串
>>> dir(k)
['__copy__', '__deepcopy__', 'findall', 'finditer', 'match', 'scanner', 'search', 'split', 'sub', 'subn']
>>> print k.findall(test) #显示所有包涵o的字符串
['to', 'you', 'you', 'from']
>>> print k.sub(lambda m: '[' + m.group(0) + ']',test) # 将字符串中含有o的单词用[]括起来
Hi, nice [to] meet [you] where are [you] [from]
>>>

五、用urllib2、re、os 模块下载文件的脚本
#!/usr/bin/env python
import urllib2
import re
import os
URL='http://image.baidu.com/channel/wallpaper'
read=urllib2.urlopen(URL).read()
pat = re.compile(r'src="http://.+ .js">')
urls=re.findall(pat,read)
for i in urls:
url= i.replace('src="','').replace('">','')
try:
iread=urllib2.urlopen(url).read()
name=os.path.basename(url)
with open(name,'wb') as jsname:
jsname.write(iread)
except:
print url,"url error"

推荐阅读：