python-三级菜单

'''
程序: 三级菜单

要求:

打印省、市、县三级菜单
可返回上一级
可随时退出程序
'''

info = {
'北京':{
'昌平':{
'沙河':["oldboy","test"],
'天通苑':["我爱我家","链家地产"]
},
'朝阳':{
'望京':["奔驰","陌陌"],
'国贸':["CICC","HP"]
},
'海淀':{}
},
'上海':{
'浦东':[]
},
'广州':{},
'深圳':{}
}

exit_flag = False
while not exit_flag:
for i in info:
print(i)
user_choice = input("你的选择是1>>>")
if user_choice in info:
while not exit_flag:
for i2 in info[user_choice]:
print("\t",i2)
user_choice2 = input("你的选择是2>>>")
if user_choice2 in info[user_choice]:
while not exit_flag:
for i3 in info[user_choice][user_choice2]:
print("\t\t",i3)
user_choice3 = input("你的选择是3>>>")
if user_choice3 in info[user_choice][user_choice2]:
while not exit_flag:
for i4 in info[user_choice][user_choice2][user_choice3]:
print("\t\t\t",i4)
user_choice4 = input("最后一层，请输入“b”返回>>>")
if user_choice4 == "b":
break
                            elif user_choice4 == "q":
exit_flag = True
                    elif user_choice3 == "b":
break
                    elif user_choice3 == "q":
exit_flag = True
            elif user_choice2 == "b":
break
            elif user_choice2 == "q":
exit_flag = True
    elif user_choice == "b":
break
    elif user_choice == "q":
exit_flag = True