def interpret(self):
        """Return value of text. Return False if text is invalid, raise exception if text is intermediate"""
        strn = self.lineEdit().text()
        suf = self.opts['suffix']
        if len(suf) > 0:
            if strn[-len(suf):] != suf:
                return False
            #raise Exception("Units are invalid.")
            strn = strn[:-len(suf)]
        try:
            val = fn.siEval(strn)
        except:
            #sys.excepthook(*sys.exc_info())
            #print "invalid"
            return False
        #print val
        return val
Return value of text. Return False if text is invalid, raise exception if text is intermediate