Re: [Pyparsing] Escaping quotes and such

[Kjell M. F. <kj...@gm...>]

On Tue, May 6, 2008 at 12:42 AM, Gre7g Luterman <haf...@ya...> wrote:
> Hey guys!  My parser has been working great, but I've
>  run into a small snag in parsing C-style escapes.  For
>  example:
>
>  >>> import pyparsing as PP
>  >>> P = PP.QuotedString(quoteChar='"', escChar="\\")
>  >>> P.parseString('"This is a quote: \\"   This is a
>  CR: \\n"')
>  (['This is a quote: "   This is a CR: n'], {})
>
>  As you can see, specifying escChar="\\" worked well at
>  first, as the parser recognized that \" is a character
>  in the string and not an end of quote. HOWEVER, when
>  the \n didn't match the \" pattern it was looking for,
>  instead of leaving it alone, it completely dropped the
>  \.
>
>  I need it to leave that \ intact so that I can find
>  other string constants such as \n, \7, \xFF, etc.  I
>  do this by re-parsing the strings with my code.
>  Perhaps that is not best?  What should I do?
>

I stumbled upon the same problem some time ago. According to Paul,
there is a bug in QuotedString. You can find a discussion of the
problem, and a workaround here:
http://pyparsing.wikispaces.com/message/view/home/3778969

Here is what I ended up with:
-----

ffrom pyparsing import Regex
import re

s = '"This is a quote: \\"   This is a CR: \\n"'

qstring2 = Regex(r'\"(?:\\\"|\\\\|[^"])*\"', re.MULTILINE)
print qstring2.parseString(s)

Output:

['"This is a quote: \\"   This is a CR: \\n"']

----

Hope this helps!

- Kjell Magne Fauske