Anyone out there use simpleparse? If so, I have a problem that I can't seem to solve...I need to be able to parse this line: """Cen2 = Cen(OUT, "Cep", "ies", wh, 544, (wh/ht));""" with this grammar: grammar = r''' declaration := ws, line, (ws, line)*, ws line := (statement / assignment), ';', ws assignment := identifier, ws, '=', ws, statement statement := identifier, '(', arglist?, ')', chars? identifier := ([a-zA-Z0-9_.:])+ arglist := arg, (',', ws, arg)* arg := expr/ statement / identifier / num / str / curve / spline / union / conditional / definition definition := typedef?, ws, identifier, ws, '=', ws, arg typedef := ([a-zA-Z0-9_])+ expr := termlist, ( operator, termlist )+ termlist := ( '(', expr, ')' ) / term term := call / identifier / num call := identifier, '(', arglist?, ')' union := '{{', ws, (arg, ws, ';', ws)*, arg, ws, '}}' operator := ( '+' / '-' / '/' / '*' / '==' / '>=' / '<=' / '>' / '<' ) conditional := termlist, ws, '?', ws, termlist, ws, ':', ws, termlist curve := (list / num), '@', num spline := (cv, ',')*, cv cv := identifier, '@', num list := '[', arg, (',', ws, arg)*, ']' str := '"', ([;] / chars)*, '"' num := ( scinot / float / int ) <chars> := ('-' / '/' / '?' / [a-zA-Z0-9_.!@#$%^&\*\+=<> :])+ <int> := ([-+]?, [0-9]+) <float> := ([-+]?, [0-9\.]+) <scinot> := (float, 'e', int) <ws> := [ \t\n]* ''' But it fails. The problem is with how arglist/arg/expr are defined, which makes it unable to handle the parenthesized expression at the end of the line: (wh/ht) But everything I've tried to correct that problem fails. In the end, it needs to be able to parse that line with those parentheses around wh/ht, or without them. Recursive parsing of expressions just seems hard to do in simpleparse, and is beyond my parsing knowledge. Here's the code to get the parser going: from simpleparse.parser import Parser p = Parser(grammar, 'line') import pprint bad_line = """Cen2 = Cen(OUT, "Cep", "ies", wh, 544, (wh/ht));""" pprint.pprint(p.parse(bad_line)) Any help greatly appreciated, thanks, -Dave -- Presenting: mediocre nebula.