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Re: Regex substitution trouble

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On 28Oct2014 04:02, massi_srb@msn.com <massi_srb@msn.com> wrote:
>I'm not really sure if this is the right place to ask about regular 
>expressions, but since I'm usin python I thought I could give a try :-)
>Here is the problem, I'm trying to write a regex in order to substitute all the occurences in the form $"somechars" with another string. This is what I wrote:
>
>newstring = re.sub(ur"""(?u)(\$\"[\s\w]+\")""", subst, oldstring)
>
>This works pretty well, but it has a problem, I would need it also to handle the case in which the internal string contains the double quotes, but only if preceeded by a backslash, that is something like $"somechars_with\\"doublequotes".
>Can anyone help me to correct it?

People seem to be making this harder than it should be.

I'd just be fixing up your definition of what's inside the quotes. There seem 
to be 3 kinds of things:

   - not a double quote or backslash
   - a backslash followed by a double quote
   - a backslash followed by not a double quote

Kind 3 is a policy call - take the following character or not? I would go with 
treating it like kind 2 myself.

So you have:

   1 [^\\"]
   2 \\"
   3 \\[^"]

and fold 2 and 3 into:

   2+3 \\.

So your regexp inner becomes:

   ([^\\"]|\\.)*

and the whole thing becomes:

   \$"(([^\\"]|\\.)*)"

and as a raw string:
   
   ur'\$"(([^\\"]|\\.)*)"'

choosing single quotes to be more readable given the double quotes in the 
regexp.

Cheers,
Cameron Simpson <cs@zip.com.au>
-- 
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Regex substitution trouble massi_srb@msn.com - 2014-10-28 04:02 -0700
  Re: Regex substitution trouble Chris Angelico <rosuav@gmail.com> - 2014-10-28 22:24 +1100
    Re: Regex substitution trouble massi_srb@msn.com - 2014-10-28 05:28 -0700
      Re: Regex substitution trouble Chris Angelico <rosuav@gmail.com> - 2014-10-28 23:59 +1100
      Re: Regex substitution trouble MRAB <python@mrabarnett.plus.com> - 2014-10-28 17:52 +0000
  Re: Regex substitution trouble TP <wingusr@gmail.com> - 2014-10-28 06:25 -0700
  Re: Regex substitution trouble Tim <jtim.arnold@gmail.com> - 2014-10-28 09:38 -0700
  Re: Regex substitution trouble Cameron Simpson <cs@zip.com.au> - 2014-10-29 13:14 +1100
  Re: Regex substitution trouble Eugene <hexumg@gmail.com> - 2014-11-05 13:44 +0300

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