Special Character problem in regexp by python

Question

I apply some regular expression on xml file to find and replace values. Normally it works.(I heard the voices saying "use xml parsers". Meanwhile I can not.) But if there is a special character in the value, it ruins everything.

Think I have a xml file like below:

<fieldset>
  <idle1>
     <value>something\\n</value>
  </idle1>
  <idle2>
    <value>blabla</value>
  </idle2>
</fieldset>

If I try to replace value in "<idle2><value>" node, value of "<idle1><value>" node becomes "something\n". And when it comes to writing to file, xml becomes:

    <fieldset>
      <idle1>
         <value>something
</value>
      </idle1>
      <idle2>
        <value>blabla</value>
      </idle2>
    </fieldset>

Well both in search and replace i use "r" string literal. But it seems not working. I solve the problem. For every search and replace, I replace "\n"s with "\\n" and then I write result to the file. But it is not an efficient way to use.

Is there something I could not see? I just want to write "\\n" to the files. Is this so much for me to want it?

Edit: here is my regexs':

for search :

self.searchPattern=(<fieldset>)(.*?)(<idle2>)(.*?)(<value>)(.*?)(</value>)(.*?)(</idle2>)(.*?)(</fieldset>)

for replace :

self.replacePattern=`\g<1>\g<2>\g<3>\g<4><value>denemeasdasd\\\\n</value>\g<8>\g<9>\g<10>\g<11>`

this is the python code for search:

self.pattern = re.compile(r''''''+self.searchPattern+'''''', flags = re.S | re.U)

and this is for replacing

outtext = self.pattern.sub(r''''''+self.replacePattern+'''''',r''''''+self.match.group(0)+'''''')

Answer 1

I don't understand your explanations.

Personnaly, I wrote this:

import re

RE = ('(^([ \t]+)<(idle2)>(?:\n|\r\n?)[ \t]+<value>)'
      '(.*?)'
      '(?=</value>(?:\n|\r\n?)\\2</\\3>)')

print repr(ch),'\n'
print ch
print '\n-------------------------------------------------'
print repr(re.sub(RE,'\\1AAA',ch,flags = re.M)) , '\n'
print re.sub(RE,'\\1-----HHHHHHXXXXXXX-------',ch,flags = re.M)

result

'<fieldset>\n  <idle1>\n    <value>something\\n</value>\n  </idle1>\n  <idle2>\n    <value>blabla</value>\n  </idle2>\n</fieldset>'

<fieldset>
  <idle1>
    <value>something\n</value>
  </idle1>
  <idle2>
    <value>blabla</value>
  </idle2>
</fieldset>

-------------------------------------------------
'<fieldset>\n  <idle1>\n    <value>something\\n</value>\n  </idle1>\n  <idle2>\n    <value>AAA</value>\n  </idle2>\n</fieldset>'

<fieldset>
  <idle1>
    <value>something\n</value>
  </idle1>
  <idle2>
    <value>-----HHHHHHXXXXXXX-------</value>
  </idle2>
</fieldset>

Is it what you want ?