code: def _init_digit_argument(self, keyinfo):
          
          c = self.console
          line = self.l_buffer.get_line_text()
          self._digit_argument_oldprompt = self.prompt
          queue = self.process_keyevent_queue
          queue = self.process_keyevent_queue
          queue.append(self._process_digit_argument_keyevent)
  
          if keyinfo.char == "-":
              self.argument = -1
          elif keyinfo.char in u"0123456789":
              self.argument = int(keyinfo.char)
          log(u"<%s> %s"%(self.argument, type(self.argument)))
          self.prompt = u"(arg: %s) "%self.argument
          log(u"arg-init %s %s"%(self.argument, keyinfo.char))
docs: Initialize search prompt