编译将自动转义或忽略特殊字符的正则表达式

Question

I'm using the results of one regex to build another regex, more or less like this:

regex = '(?P<prev>.+?)(?P<hook>\%\%.+?\%\%)(?P<next>.+?$)'
match = re.search(regex, content, re.S)

comparisonRegex = match.group('prev') + 
    '(?P<desiredContent>desireable)' + match.group('next')
match = re.search(comparisonRegex, otherContent, re.S)

this approach works fine, but sometimes it will throw this error:

  File "/path/to/my/script/refactor_static.py", line 92, in dynamicContent
    match = re.search(comparisonRegex, crawlFileContent, re.S)
  File "/usr/lib/python2.7/re.py", line 142, in search
    return _compile(pattern, flags).search(string)
  File "/usr/lib/python2.7/re.py", line 244, in _compile
    raise error, v # invalid expression
sre_constants.error: bad character range

I'm fairly confident this is because the content I'm searching through and using as a new regex has invalid characters or sequences in it, but I'm not sure how to approach this. Is there an argument I can pass that will essentially tell it to compile all the letters as literals and not as special characters? So far I haven't been able to find anything in the python regex guide .

Answer 1

re.escape

regex = '(?P<prev>.?+)(\%\%.+?\%\%)(?P<next>.+?$)'
match = re.search(regex, content, re.S)

comparisonRegex = re.escape(match.group('prev')) + 
    '(?P<desiredContent>desireable)' + re.escape(match.group('next'))
match = re.search(comparisonRegex, otherContent, re.S)