Raw string substitution problem

[Ed Keith]

--- On Wed, 12/16/09, Gabriel Genellina <gagsl-py2 at yahoo.com.ar> wrote:

> From: Gabriel Genellina <gagsl-py2 at yahoo.com.ar>
> Subject: Re: Raw string substitution problem
> To: python-list at python.org
> Date: Wednesday, December 16, 2009, 9:35 AM
> En Wed, 16 Dec 2009 11:09:32 -0300,
> Ed Keith <e_d_k at yahoo.com>
> escribió:
> 
> > I am having a problem when substituting a raw string.
> When I do the following:
> > 
> > re.sub('abc', r'a\nb\nc', '123abcdefg')
> > 
> > I get
> > 
> > """
> > 123a
> > b
> > cdefg
> > """
> > 
> > what I want is
> > 
> > r'123a\nb\ncdefg'
> 
> From http://docs.python.org/library/re.html#re.sub
> 
>     re.sub(pattern, repl, string[, count])
> 
>     ...repl can be a string or a function;
> if
>     it is a string, any backslash escapes
> in
>     it are processed. That is, \n is
> converted
>     to a single newline character, \r is
>     converted to a linefeed, and so forth.
> 
> So you'll have to double your backslashes:
> 
> py> re.sub('abc', r'a\\nb\\nc', '123abcdefg')
> '123a\\nb\\ncdefg'
> 
> --Gabriel Genellina
> 
> --http://mail.python.org/mailman/listinfo/python-list
> 

That is going to be a nontrivial exercise. I have control over the pattern, but the texts to be substituted and substituted into will be read from user supplied files. I need to reproduce the exact text the is read from the file. 

Maybe what I should do is use re to break the string into two pieces, the part before the pattern to be replaces and the part after it, then splice the replacement text in between them. Seems like doing it the hard way, but it should work. 

Thanks,

   -EdK