# 简单的购物小程序

product_list = [
  ['surface pro 4', 7800],
  ['dell xps 15', 12000],
  ['macbook', 12000],
  ['小米6', 2499],
  ['iphone7', 4600],
  ['坚果Pro', 1499]
]
shopping_list = []


# 判断输入的薪水格式是否正确
while True:
  salary = input('\n请输入您的薪水：')
  if not salary.isdigit():          # 薪水不是数字，结束循环
    print('\n输入格式有误！请重新输入...')
    continue
  break


balance = salary = int(salary)

print('\n-----------欢迎购买------------\n')

# 生成带序号的商品列表
for index, item in enumerate(product_list):
  print(index, item)


# 判断输入的序号是否符合要求
while True:

  while True:
    i = input('\n输入您要购买的商品序号，或输入 q 取消购买：')
    if i == 'q':                 # 输入 q 退出购买界面
      while True:
        a = input('\n是否继续购买？(Y/N)：')
        if a != 'n' and a != 'N' and a != 'y' and a != 'Y':
          print('\n输入格式有误，请重试...')
          continue
        elif a == 'y' or a == 'Y':         # 继续购买
          break
        else:                    # 购买完毕
          if balance == salary:       # 没有买任何东西
            print('\n交易结束，购买失败...')
            exit()
          else:               # 结算  
            print('\n您已成功购买以下商品：\n')
            for item in shopping_list:
              print(item)
            print('\n共消费金额 %d 元，余额 %d 元' % (salary - balance, balance))
            exit()
      continue

    if not i.isdigit():             # 序号不是数字，结束循环
      print('\n输入格式有误！请重新输入...')
      continue

    i = int(i)

    if i < 0 or i >= len(product_list):  # 序号范围不正确，结束循环
      print('\n此商品不存在，请重新输入...')
      continue
    break

  product = product_list[i]
  price = int(product[1])

  # 判断余额是否充足，够就直接扣款，不够提醒
  if price <= balance:
    balance -= price
    shopping_list.append(product_list[i])
    print('\n您已成功购买 %s ，当前余额为 %d 元' %(product, balance))
  else:
    print('\n购买失败，您的余额不足...')

  while True:
    a = input('\n是否继续购买？(Y/N)：')
    if a != 'n' and a != 'N' and a != 'y' and a != 'Y':
      print('\n输入格式有误，请重试...')
      continue
    break

  if a == 'Y' or a == 'y':
    continue
  else:
    break

if balance == salary:
  print('\n交易结束，购买失败...')
  exit()
else:
  print('\n您已成功购买以下商品：\n')
  for item in shopping_list:
    print(item)
  print('\n共消费金额 %d 元，余额 %d 元' %(salary-balance, balance))
  exit()