简单购物车

数据结构：
goods = [
{"name": "电脑", "price": 1999},
{"name": "鼠标", "price": 10},
{"name": "游艇", "price": 20},
{"name": "美女", "price": 998},
......
]

功能要求：
基础要求：

1、启动程序后，输入用户名密码后，让用户输入工资，然后打印商品列表

2、允许用户根据商品编号购买商品

3、用户选择商品后，检测余额是否够，够就直接扣款，不够就提醒

4、可随时退出，退出时，打印已购买商品和余额

5、在用户使用过程中， 关键输出，如余额，商品已加入购物车等消息，需高亮显示


扩展需求：

1、用户下一次登录后，输入用户名密码，直接回到上次的状态，即上次消费的余额什么的还是那些，再次登录可继续购买

2、允许查询之前的消费记录

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# @Date    : 2018-04-29 12:16:23
# @Author  : hjc (284738209@qq.com)
# @Link    : http://www.cnblogs.com/tootooman/
# @Version : 2


import os
import re
import time
import json

goods = [
    {"name": "电脑", "price": 1999},
    {"name": "鼠标", "price": 10},
    {"name": "游艇", "price": 20},
    {"name": "美女", "price": 998},
]

userdb = 'userdb'
if not os.path.isfile(userdb):
    db = open(userdb, 'w', encoding='utf8')
    db.write('{}')
    db.close()

shopping_car = {}


flag = True

while flag:
    username = input('用户名:').strip()
    password = input('密码:').strip()
    with open(userdb, 'r+') as users:
        users_data = json.load(users)
        if username in users_data:
            if password == users_data[username]:
                # os.path.isfile(username)
                check = input('是否要查看消费历史[y：查看/任意键：进入商城]：').strip()
                f = open(username, 'r', encoding='utf8')
                if check == 'y':
                    print('start'.center(60, '-'))
                    for line in f:
                        print(line)
                    print('end'.center(60, '-'))

                ret = ''
                f.seek(0)
                for line in f:
                    ret = re.findall('余额.*', line)
                salary = int(ret[0].split('：')[-1])

                f.close()
                break
            else:
                print('用户名或密码错误。')

        else:
            print('你不是会员！系统已自动帮你注册会员！')
            users.seek(0)
            users_data[username] = password
            json.dump(users_data, users)
            while 1:
                salary = input('兜里有多少钱：:').strip()
                if salary.isdigit():
                    salary = int(salary)
                    f = open(username, 'w', encoding='utf8')
                    f.close()
                    flag = False
                    break
                else:
                    print('你兜里的不是钱！')

while 1:
    title = '''
    %s
    %s
    %s
    ''' % (''.center(60, '*'), '商品列表'.center(60, ' '), ''.center(60, '*'))
    print(title)
    for i in range(len(goods)):
        info = '''
        商品编号：%s    商品名称：%s    商品价格：%s
        ''' % (i, goods[i]['name'], goods[i]['price'])
        print(info)
    choice = input('输入商品编号[q：结算]:').strip()
    if choice.isdigit():
        choice = int(choice)
        if choice >= 0 and choice < len(goods):
            if salary >= goods[choice]['price']:
                goods_name = goods[choice]['name']
                goods_price = goods[choice]['price']
                salary -= goods_price
                if shopping_car.get(goods_name):
                    shopping_car[goods_name]['total'] += 1
                    print('33[1;32m%s33[0m已放到购物车，购买后兜里还剩 33[1;31m%s33[0m' % (
                        goods_name, salary))
                else:
                    shopping_car[goods_name] = {}
                    shopping_car[goods_name]['price'] = goods_price
                    shopping_car[goods_name]['total'] = 1
                    print('33[1;32m%s33[0m已放到购物车，购买后兜里还剩 33[1;31m%s33[0m' % (
                        goods_name, salary))
            else:
                print('兜里钱不够！兜里还剩 33[1;31m%s33[0m ！' % (salary,))
                while 1:
                    get_money = input('要不要借一点？[n：不要]：').strip()
                    if get_money.isdigit():
                        get_money = int(get_money)
                        salary += get_money
                        print('借 钱 成 功！当前余额为：%s' % (salary,))
                        break
                    elif get_money == 'n':
                        break
                    else:
                        print('信不信我揍你。。。')
        else:
            print('没有相关商品。')
    elif choice == 'q':
        if len(shopping_car) != 0:
            pay_time = time.strftime('%Y-%m-%d %H:%M:%S', time.localtime())
            print('购物车信息：买完兜里还剩 33[1;31m%s33[0m' % (salary))
            with open(username, 'a+', encoding='utf8') as f:
                f.write('%s
' % (pay_time.center(50, '=')))
                for item in shopping_car:
                    shopping_list = '''
                    商品名称：%s    商品价格：%s    已买数量：%s    合计：%s
                    ''' % (item,
                           shopping_car[item]['price'],
                           shopping_car[item]['total'],
                           shopping_car[item]['total'] *
                           shopping_car[item]['price'],
                           )
                    print(shopping_list.strip())
                    f.write('%s
' % (shopping_list.strip()))
                f.write('余额：%s
' % (salary))
            break
        else:
            print('没有买任何东西。')
            break