2017/6/8-python正则表达式的使用

#match()函数的使用

#\w匹配字母数字及下划线
# \s匹配任意空白字符，等价于 [\t\n\r\f].
# \d匹配任意数字，等价于 [0-9]
# [...]用来表示一组字符,单独列出：[amk] 匹配 'a'，'m'或'k'
# [^...]不在[]中的字符：[^abc] 匹配除了a,b,c之外的字符。
#^匹配字符串的开头
#{n}精确匹配n个前面表达式。
import re
content='Hello 123 4567 World_This is a Regex Demo'
print(len(content))
pattern=re.compile(r'^Hello\s\d\d\d\s\d{4}\s\w{10}')
result=re.match(pattern,content)
print(result)
print(result.group())
print(result.span())

41
<_sre.SRE_Match object; span=(0, 25), match='Hello 123 4567 World_This'>
Hello 123 4567 World_This
(0, 25)

#匹配目标

#group()会输出完整的匹配结果，而group(1)会输出第一个被()包围的匹配结果
import re
content='Hello 1234567 World_This is a Regex Demo'
pattern=re.compile(r'^Hello\s(\d{7})\s(\w{5})')
result=re.match(pattern,content)
print(result)
print(result.group())
print(result.group(1))
print(result.group(2))
print(result.span())

<_sre.SRE_Match object; span=(0, 19), match='Hello 1234567 World'>
Hello 1234567 World
1234567
World
(0, 19)

#通用匹配
#.匹配任意字符（除换行符外）
#*匹配0次或者多次
import re
content='Hello 123 4567 World_This is a Regex Demo'
pattern=re.compile(r'^Hello.*Demo$')
result=re.match(pattern,content)
print(result)
print(result.group())
print(result.span())

<_sre.SRE_Match object; span=(0, 41), match='Hello 123 4567 World_This is a Regex Demo'>
Hello 123 4567 World_This is a Regex Demo
(0, 41)

#贪婪匹配与非贪婪匹配

#01贪婪匹配
import re
content='Hello 1234567 World_This is a Regex Demo'
pattern=re.compile(r'^He.*(\d+).*Demo$')
result=re.match(pattern,content)
print(result)
print(result.group())
print(result.group(1))

<_sre.SRE_Match object; span=(0, 40), match='Hello 1234567 World_This is a Regex Demo'>
Hello 1234567 World_This is a Regex Demo
7

#02非贪婪匹配
import re
content='Hello 1234567 World_This is a Regex Demo'
pattern=re.compile(r'He.*?(\d+).*Demo$')
result=re.match(pattern,content)
print(result)
print(result.group())
print(result.group(1))

<_sre.SRE_Match object; span=(0, 40), match='Hello 1234567 World_This is a Regex Demo'>
Hello 1234567 World_This is a Regex Demo
1234567

#但这里注意，如果匹配的结果在字符串结尾，.*?就有可能匹配不到任何内容了，因为它会匹配尽可能少的字符，例如：
import re
content='https://www.baidu.com/search/error.html'
result1=re.match(r'^https.*search/(.*)',content)
result2=re.match(r'https.*search/(.*?)',content)
print(result1.group(1))
print(result2.group(1))

error.html

#修饰符
#正则表达式可以包含一些可选标志修饰符来控制匹配的模式。修饰符被指定为一个可选的标志。
import re
content = '''Hello 1234567 World_This
is a Regex Demo'''

pattern=re.compile(r'^He.*?(\d+).*?Demo$',re.S)
result=re.match(pattern,content)
print(result.group(1))

1234567

#转义匹配
import re
content='(百度)www.baidu.com'
pattern=re.compile(r'\(百度\)www\.baidu\.com')
result=re.match(pattern,content)
print(result.group())

(百度)www.baidu.com

#search()
import re
content = 'Extra stings Hello 1234567 World_This is a Regex Demo Extra stings'
pattern=re.compile('He.*?(\d+).*Demo')
result=re.search(pattern,content)
print(result.group())
print(result.group(1))

Hello 1234567 World_This is a Regex Demo
1234567

import re
html = '''<div id="songs-list">
    <h2 class="title">经典老歌</h2>
    <p class="introduction">
        经典老歌列表
    </p>
    <ul id="list" class="list-group">
        <li data-view="2">一路上有你</li>
        <li data-view="7">
            <a href="/2.mp3" singer="任贤齐">沧海一声笑</a>
        </li>
        <li data-view="4" class="active">
            <a href="/3.mp3" singer="齐秦">往事随风</a>
        </li>
        <li data-view="6"><a href="/4.mp3" singer="beyond">光辉岁月</a></li>
        <li data-view="5"><a href="/5.mp3" singer="陈慧琳">记事本</a></li>
        <li data-view="5">
            <a href="/6.mp3" singer="邓丽君"><i class="fa fa-user"></i>但愿人长久</a>
        </li>
    </ul>
</div>'''
result=re.search('<li.*?active.*?singer="(.*?)">(.*?)</a>',html,re.S)
if result:
    print(result.group(1), result.group(2))

齐秦 往事随风

#sub()方法
import re
content = '54aK54yr5oiR54ix5L2g'
result=re.sub('\d+','',content)
print(result)

aKyroiRixLg

log='2017-06-06 15:06:16,148 - root - DEBUG - logger debug message'
print(log.split('-'))

['2017', '06', '06 15:06:16,148 ', ' root ', ' DEBUG ', ' logger debug message']