data = {
    ‘北京‘: {
        ‘朝陽‘: {},
        ‘海澱‘: {},
        ‘昌平‘: {},
    },
    ‘上海‘: {},
    ‘四川‘: {
        ‘廣元‘:{
            ‘利州區‘:{},
            ‘昭化‘:{},
            ‘朝天三區‘:{},
        },
        ‘成都‘:{
            ‘金牛區‘: {},
            ‘成華區‘: {},
            ‘高新區‘: {},
        },
        ‘綿陽‘:{
            ‘涪城區‘: {},
            ‘遊仙區‘: {},
            ‘農科區‘: {},
        },
    },
}

current_layer = data
parent_layers = []
while True:
    for i in current_layer: #循環字典中的key
        print(i)
    choice = input(‘請輸入:‘)
    if choice in current_layer:
        parent_layers.append(current_layer)
        current_layer = current_layer[choice]
    elif choice == ‘b‘:
        if parent_layers:
            current_layer = parent_layers.pop()
    elif choice == ‘q‘:
        current_layer = data
    elif choice == ‘e‘:
        exit()
    else:
        print(‘您的輸入有誤，請重新輸入：‘)

省市區縣，實現逐層訪問，並逐層返回！