[Pyparsing] Variable comment char

[Russell D. <Rus...@as...>]

I need to parse a rather evil format that has the following line:

[Comment Char] |_char

Which would change the comment char to '|'. The comment char can be
any non-alphanumeric printable other than [ or ] and the comment char
can be changed at any time and as many times as desired. The non
comment, non bracket characters are legal characters. Initially, I
figured I'd hold onto the ParserElement objects in self and modify
them in callbacks. However, it appears they get copied and thus
modifying them does nothing. So I made a Token class that has an
internal reference to something I can modify. This works for the
comment char, but then I have the issue of parsing tokens that
contains characters that could be comment characters. If I include all
non printables in that word, then comments don't get ignored. What's
the best way to do this?

class DynamicCharHolder():
    def __init__(self, char):
        self.match = char
    def getMatch(self):
        return self.match
    def setMatch(self, char):
        self.match = char

class DynamicChar(Token):
    def __init__(self, holder):
        super(DynamicChar, self).__init__()
        self.holder = holder
        self.name = "DynamicChar"
        self.mayReturnEmpty = False
        self.mayIndexError = False
    def parseImpl(self, instring, loc, doActions=True ):
        if (instring[loc] == self.holder.getMatch()):
                print "match '" + instring[loc] + "' at " + str(loc)
                return loc + 1, instring[loc]
        exc = self.myException
        exc.loc = loc
        exc.pstr = instring
        raise exc

class IBISParser:
    def setCommentDelim(self, tokens):
        self.holder.setMatch(tokens[0])
        print "New comment delim " + tokens[0]

    def __init__(self, text):
        self.holder = DynamicCharHolder("|")
        comment_delim = DynamicChar(self.holder)
        comment = comment_delim + restOfLine
[...]
        ibis_file.ignore(comment)