要求：
用户入口
1、商品信息存在文件里
2、已购商品，余额记录。
商家入口
可以添加商品，修改商品价格
Code：
商家入口：
# Author:P J J
import os
ps = '''
1 >>>>>> 修改商品
2 >>>>>> 添加商品
按q为退出程序
'''
# 打开两个文件，f文件为原来存取商品文件,f_new文件为修改后的商品文件
f = open('commodit', 'r', encoding='utf-8')
f_new = open('commodit_update', 'w+', encoding='utf-8')
file_list = f.readlines()
# 打印商品信息
while True:
productslist = []
# 从商品文件中读取出来的数据存放到productslist列表里
for line in file_list:
productname = line.strip().split()
productname, oldprice = line.strip("
").split()
productslist.append([productname, int(oldprice)])
choose = input("%s请选择：" %ps)
if choose =='1':
for index, item in enumerate(productslist):
print(index, item)
productindex = input("请输入要修改价格的商品序号:")
if productindex.isdigit():
productindex = int(productindex)
while True:
print('要修改商品信息:', productslist[productindex])
price = input("请输入要修改的价格:")
if price.isdigit():
price = int(price)
productslist[productindex][1]=price
break
else:
print("请正确的输入价格！")
continue
#已经修改好的商品列表循环写入f_new文件夹
for products in productslist:
insert_data = "%s %s" %(products[0],products[1])
f_new.write(insert_data+'
')
print("商品价格已经修改！")
# 替换原来的文件
f_new = open('commodit_update', 'r', encoding='utf-8')
data = f_new.readlines()
f = open('commodit', 'w+', encoding='utf-8')
for line in data:
f.write(line)
f.close()
f_new.close()
#删除替换文件
os.remove('commodit_update')
elif choose =='2':
# 添加商品
f = open('commodit', 'a+', encoding='utf-8')
pricename = input("请输入商品名:")
while True:
price = input("请输入商品价格:")
if price.isdigit():
f.writelines('%s %s
' % (pricename, price))
break
else:
print('输入错误请重新输入!')
continue
f.close()
continue
elif choose =='q':
break
else:
print("输入错误请重新输入")
continue买家入口：
# Author:P J J
productslist = []
f = open('commodit','r',encoding='utf-8')
for line in f:
productname,price = line.strip('
').split()
productslist.append((productname,int(price)))
print(productslist)
shopping_list = []
salary = input("请输入你的现金:")
if salary.isdigit():
salary = int(salary)
while True:
# for item in productslist:
# print(productslist.index(item),item)
for index,item in enumerate(productslist):
print(index,item)
#判断用户要输入
user_choice = input("请选择要买什啥>>>:")
if user_choice.isdigit():
user_choice = int(user_choice)
if user_choice < len(productslist) and user_choice >= 0:
p_item = productslist[user_choice]
if p_item[1] <= salary: #买得起
shopping_list.append(p_item)
salary -=p_item[1]
print("加入 %s 购物车你的余额是