python-实现3级菜单（作业课）

 #任务：
 #显示3级菜单
 #1级菜单#显示 3个城市 => 1北京 2上海 3广州
 #2级菜单  #显示 选择1 北京 => B1 B2 B3
 #2级菜单  #显示 选择2 上海 => S1 S2 S3
 #2级菜单  #显示 选择3 广州 => G1 G2 G3

 #3级菜单  #显示 选择B1 => b1_1 b1_2 b1_3
 #3级菜单  #显示 选择B2 => b2_1 b2_2 b2_3
 #3级菜单  #显示 选择B3 => b3_1 b3_2 b3_3

 #3级菜单  #显示 选择S1 => s1_1 s1_2 s1_3
 #3级菜单  #显示 选择S2 => s2_1 s2_2 s2_3
 #3级菜单  #显示 选择S3 => s3_1 s3_2 s3_3

 #3级菜单  #显示 选择G1 => g1_1 g1_2 g1_3
 #3级菜单  #显示 选择G2 => g2_1 g2_2 g2_3
 #3级菜单  #显示 选择G3 => g3_1 g3_2 g3_3

 #选择Q键 退出程序， 选择R键 返回上一级菜单

 curPage = 0; #当前页数
 minPage = 0; #最小页数
 maxPage = 3; #最大页数
 showVal = "1.北京 2.上海 3.广州 R.上一页 Q.退出"
 selectVal = "北京"

 while True:
     print("-----------------------------------")
     print("|"+showVal+"|") #显示具体内容
     print("-----------------------------------")
     userVal = input("input your select: ") #用户输入的值

     if userVal == "Q" or userVal == "q":
         break

     if userVal == "":
         if curPage == 0:
             selectVal = "北京"
             showVal = "   1.B1 2.B2 3.B3 R.上一页 Q.退出  "
             curPage += 1;
         elif curPage == 1:
             if selectVal == "北京":
                 showVal = "         b1_1 b1_2 b1_3          "
             elif selectVal == "上海":
                 showVal = "         s1_1 s1_2 s1_3          "
             elif selectVal == "广州":
                 showVal = "         g1_1 g1_2 g1_3          "
             curPage += 1;
     elif userVal == "":
         if curPage == 0:
             selectVal = "上海"
             showVal = "   1.S1 2.S2 3.S3 R.上一页 Q.退出  "
             curPage += 1;
         elif curPage == 1:
             if selectVal == "北京":
                 showVal = "         b2_1 b2_2 b2_3         "
             elif selectVal == "上海":
                 showVal = "         s2_1 s2_2 s2_3         "
             elif selectVal == "广州":
                 showVal = "         g2_1 g2_2 g2_3         "
             curPage += 1;
     elif userVal == "":
         if curPage == 0:
             selectVal = "广州"
             showVal = "   1.G1 2.G2 3.G3 R.上一页 Q.退出  "
             curPage += 1;
         elif curPage == 1:
             if selectVal == "北京":
                 showVal = "         b3_1 b3_2 b3_3         "
             elif selectVal == "上海":
                 showVal = "         s3_1 s3_2 s3_3         "
             elif selectVal == "广州":
                 showVal = "         g3_1 g3_2 g3_3         "
             curPage += 1;
     elif userVal == "r" or userVal == "R":
         if curPage <= 1:
             showVal = "1.北京 2.上海 3.广州 R.上一页 Q.退出"
             curPage = 0
         else:
             if selectVal == "北京":
                 showVal = "         1.B1 2.B2 3.B3         "
                 curPage -= 1;
             elif selectVal == "上海":
                 showVal = "         1.S1 2.S2 3.S3         "
                 curPage -= 1;
             elif selectVal == "广州":
                 showVal = "         1.G1 2.G2 3.G3         "
                 curPage -= 1;
     else:
         print("->没有找到对应的城市，请重新输入<-")
 print("GAME OVER")