#1   簡單版  切換
goods = {
    '華為':{
        'A系':{'A1':[1000,1100,1200,],'A2':[2000,2100,2200,],'A3':[3000,3100,3200,],},
        'B系':{'B1':[4000,4200,4400,],'B2':[5000,5200,5400,],'B3':[6000,6200,6400,],},
        'C系':{'C1':[7000,7300,7600,],'C2':[8000,8300,8600,],'C3':[9000,9300,9600,],},},
    '小米':{
        'M系':{'M1':[610,630,650,],'M2':[710,730,750,],'M3':[810,830,850,],},
        
 
'N系':{'N1':[920,950,980,],'N2':[1020,1050,1080,],'N3':[1120,1150,1180],},
        'L系':{'L1':[1230,1270,1300,],'L2':[1430,1470,1500,],'L3':[1630,1670,1700,],},},
    '魅族':{
        'X系':{'X1':[599,699,799,],'X2':[699,799,899,],'X3':[799,899,999,],},
        'Y系':{'Y1':[1099,1199,1299,],'Y2':[1299,1399,1499,],'Y3':[1499,1599,1699,],},
        
 
'Z系':{'Z1':[2099,2199,2299,],'Z2':[2399,2499,2599,],'Z3':[2699,2799,2899,],},},}



menu = [goods]

while 1:
    for good in goods:
        print(good)

    choose = input("請選擇》》》")
    if choose in goods:
        #將當前的遍歷字典加入到menu列表中，方便返回時呼叫
        menu.append(goods)
        #把使用者選擇的字典，賦值給goods
        goods = goods[choose]

    
 
elif choose.upper()=="B":
        #使用者選擇返回上一級時，把記錄列表中最後一項賦值給要迴圈的goods,然後再把最後一項一個字典刪除
        goods = menu[-1]
        menu.pop()
    elif choose.lower()=="q":
        break
    else:
        print("你輸入有誤，請重新選擇")

 2.目錄逐層進入和返回上一層的實現 

import os

def switch_dir(path):

    menu = [path]

    while 1:
        lst = os.listdir(path)

        for el in lst:
            print(el)

        choose = input("請選擇(../表示切換到上層目錄)》》》")
        if choose in lst and os.path.isdir(os.path.join(path, choose)):

            menu.append(path)
            path = os.path.join(path, choose)

        elif choose.strip() =="../":#
            path = menu[-1]

            if len(menu)==1:
                print("已經是家目錄了，沒有上一層目錄了")
            else:
                menu.pop()

        elif choose.upper()=="Q":
            break

        else:
            print("輸入有誤或為非資料夾")

path = "d:\home"
switch_dir(path)