trouble with regex with escaped metachars (URGENT please O:-)

[Fernando Rodriguez]

Hi,

I have a filewhose contents looks like this:

Compression=bzip/9
OutputBaseFilename=$<OutputFileName>
OutputDir=$<OutputDir>
LicenseFile=Z:\apps\easyjob\main\I18N\US\res\license.txt

The tokens $<...> must be susbtituted by some user-provided string.  The
problem is that those user-provided strings might contain metacharacters, so I
escape them. And that's where I get into trouble.

Here's the code I'm using:

        def substitute(name, value, cts):
            """
            Finds all the occs in  cts of $<name>
            and replaces them with value
            """
            
            pat = re.compile("\$<" + name + ">", re.IGNORECASE)

            return pat.sub(val, cts)  # this line causes the error (see below)

        def escapeMetachars( s ):
            """
            All metacharacters in the user provided substitution must
            be escaped
            """
            meta = r'\.^$+*?{[|()'
            esc = ''

            for c in s:
                if c in meta:
                    esc += '\\' + c
                else:
                    esc += c

            return esc

cts = """Compression=bzip/9
OutputBaseFilename=$<OutputFileName>
OutputDir=$<OutputDir>
LicenseFile=Z:\apps\easyjob\main\I18N\US\res\license.txt"""

name = 'OutputDir'
value = "c:\\apps\\whatever\\"  # contains the backslash metachar

print substitute( escapeMetachars(name), value,  cts)

I get this error:
Traceback (most recent call last):
  File "<pyshell#38>", line 1, in -toplevel-
    pat.sub(s,cts)
  File "C:\ARCHIV~1\python23\Lib\sre.py", line 257, in _subx
    template = _compile_repl(template, pattern)
  File "C:\ARCHIV~1\python23\Lib\sre.py", line 244, in _compile_repl
    raise error, v # invalid expression
error: bogus escape (end of line)

What on earth is this? O:-)

PS: I can't use string.replace() for the susbtitution,because it must be
case-insensitive: the user might enter OUTPUTDIR, and it should still work.