code: def interpret(self):
          
          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
docs: Return value of text. Return False if text is invalid, raise exception if text is intermediate