购物车作业01

li = ['手机','电脑','鼠标垫','键盘','鼠标']
print('欢迎光临!')
dic = {}
for x in li:
    print('{}\t{}'.format(li.index(x),x))
    dic.setdefault(li.index(x),x)
while 1:
    num = input('>>>/输入Q退出')
    if num.upper() == 'Q':
        break
    if num.isdigit():
        num = int(num)
        if num >= 0 and num < len(li):
            print(dic.get(num,None))
            break
        else:print('请输入有效的序号!')
    else:
        print('输入的不是商品序号,请重新输入!')
        continue