查找两个字符之间的正则表达式

Question

I have a txt file which contains the following line.

<KEY key="Spread" keyvalue="FILENAME">

How can I extract FILENAME from the above using regular expressions So far I have tried (in my python script):

if '"Spread" keyvalue' in line:
    n = re.search(r'\keyvalue="(.*)', line)
    name = n.group()
    print name

This gives an output of:

keyvalue="FILENAME">

but I only want to output:

FILENAME

What is the regular expression I need?

Answer 1

Change your regex to,

n = re.search(r'\bkeyvalue="(.*?)"', line)
name = n.group(1)

Example:

>>> import re
>>> s = '''<KEY key="Spread" keyvalue="FILENAME">'''
>>> n = re.search(r'\bkeyvalue="(.*?)"', s)
>>> n.group(1)
'FILENAME'
>>> 

OR

Use BeautifulSoup.

>>> from bs4 import BeautifulSoup
>>> xml = '''<KEY key="Spread" keyvalue="FILENAME">'''
>>> soup = BeautifulSoup(xml, 'lxml')
>>> s = soup.find('key', attrs={'key':'Spread'})
>>> s.get('keyvalue', None)
'FILENAME'

Answer 2

Another pattern to try:

>>> line = '<KEY key="Spread" keyvalue="FILENAME">'
>>> re.findall('\s+keyvalue=\"([^"]+)\"', line)
['FILENAME']

Answer 3

Try following regex. I'm using lookbehind feature.:

(?<=keyvalue=\").*?(?=\")

Your code should look like:

line = '<KEY key="Spread" keyvalue="FILENAME">'

match = re.search(r"(?<=keyvalue=\").*?(?=\")", line, re.MULTILINE)
if match:
    result = match.group()
    print(result)

If match is successful, it should print FILENAME .