[Baypiggies] regex puzzle

Aaron Maxwell amax at redsymbol.net
Tue Mar 11 18:47:12 CET 2008

Hi all,

I'm writing a tool with a command line interface, using the cmd module.  It 
has a "log search" command, which accepts a regex pattern as an argument.

After tokenizing the input, I finally get what the user typed as the regex 
pattern into a variable search_str:

  regex = re.compile(search_str)
  return [line for line in loglines if regex.search(line)]

The problem is that search_str is a variable of type str, not a raw string.  
So the user will have to escape many characters: e.g., "\\bREPO" instead 
of "\bREPO" as the pattern.

What I'd like to do is allow the user to type in the regular expression 
directly, without them having to escape it.  Can someone suggest a good 

I could obviously have my code escape search_str, coding it to manually 
replace each special character (http://docs.python.org/ref/strings.html).   
But that seems unpythonic (by which I mean "tedious and error prone" :)  
There was a thread [0] that suggested using str.encode(), but I did not find 
that to work - for example, with '\bRE'.encode('string_escape'), \b is 
interpreted as '\x08', the backspace character.

Suggestions appreciated.  


[0] http://mail.python.org/pipermail/python-list/2004-December/296389.html

Aaron Maxwell

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