#---author:Administrator--- #---DATE:2019/4/15--- #---TIME:11:24--- menu = {
      '北京':{
          '朝阳区':{
              '国贸':{
                  '大裤衩':{},                 'CBD':{},                 '购物':{},             },             '双井':{},             '劲松':{},         },         '海淀区':{},         '昌平区':{},     },     '上海':{},     '山西':{}, } current_layer = menu parent_layers = [] while True:     for key in current_layer:         print(key)     chooice = input('>>>:').strip()     if len(chooice) == 0:continue     if chooice in current_layer:         parent_layers.append(current_layer)         current_layer = current_layer[chooice]     elif chooice == 'b':         if parent_layers:             current_layer = parent_layers.pop()     elif chooice == 'q':         exit()     else:         print('非法输入,请重新输入:')