1.所谓组,即你查一次,可以查多种匹配的结果,每种结果即是一组
eg.
import re
pattern = re.compile(r'<div(.*?>)(.*?)</div>')
match = pattern.match('<div class="test">Hello <div>wa haha<div>test xxx</div></div>world</div>')
if match:
print match.group(2)
print match.group(1)
print match.group(0)
>>> ================================ RESTART ================================
>>>
Hello <div>wa haha<div>test xxx
class="test">
<div class="test">Hello <div>wa haha<div>test xxx</div>
>>>
其中group(0)比较特殊,所有组的合集
2.查找一个文件中所有的http(url)地址
import re
import urllib2
f = open('url.txt','r')
string = ""
while 1:
line = f.readline()
if not line:break
string += line
f.close()
urls = re.findall('http[s]?://(?:[a-zA-Z]|[0-9]|[$-_@.&+]|[!*\(\),]|(?:%[0-9a-fA-F][0-9a-fA-F]))+', string)
3.正则表达式中的空格包括\t\r\n\f\v等几种字符