Python正则表达式

import  re
s   =   'Hello  from    csev@umich.edu  to  cwen@iupui.edu  about   the meeting @2PM'
lst =   re.findall('\S+@\S+',   s)
print   lst

要注意，\S+是指有至少一个的非空字符。 上面的输出结果是['csev@umich.edu', 'cwen@iupui.edu']

将搜索与抽取结合：

import re
target='//home//moon//Desktop//mbox-short.txt'
mes=open(target)

for line in mes:
    line=line.rstrip()
    if re.search('^X\S*: +',line):
        print line

运行这个程序,经过过滤的数据仅保留如下内容:
X-DSPAM-Confidence: 0.8475
X-DSPAM-Probability: 0.0000
X-DSPAM-Confidence: 0.6178
X-DSPAM-Probability: 0.0000

正则表达式括号

import re
target='//home//moon//Desktop//mbox-short.txt'
mes=open(target)

for line in mes:
    line=line.rstrip()
    x=re.findall('^X\S*: ([0-9.]+)',line)
    if len(x)>0:
        print x 

程序运行结果如下:
[‘0.8475’]
[‘0.0000’]
[‘0.6178’]
[‘0.0000’]
[‘0.6961’]
[‘0.0000’]