购物车登陆购物版

*****************购物车
import os
product_list = [['Iphone7',5800],
                ['Coffee',30],
                ['疙瘩汤',10],
                ['Python Book',99],
                ['Bike',199],
                ['ViVo X9',2499],

                ]

shopping_cart={}
current_userinfo=[]
db_file=r'db.txt'
while True:
    print('''
    1 注册
    2 登录
    3 购物
    ''')
    choice=input('请选择:').strip()
    if choice =='1':
        while True:
            name=input('username:')
            password=input('password:')
            conf_password=input('conf password')
            balance=input('balance:')
            if password ==conf_password:
                with open(db_file,'a') as f:
                    f.write('%s,%s,%s
'%(name,password,balance))
                break
            else:
                print('两次密码不一致')
    elif  choice =='2':
        count=0
        tag=True
        while tag:
            if count ==3:
                print('错误过多，退出')
                break
            name=input('name')
            password=input('password')
            with open(db_file,'r') as f:
                for line in f:
                    user_info=line.split(',')
                    user_name=user_info[0]
                    user_password=user_info[1]
                    user_balance=int(user_info[2])
                    if user_name == name and user_password == password:
                        current_userinfo=[user_name,user_balance]
                        print('登录成功')
                        print('用户信息为：',current_userinfo)
                        tag=False
                        break
                    else:
                        print('用户名密码错误')
                        count+=1


    elif choice == '3':
        if len(current_userinfo) == 0:
            print('33[49m请先登陆...33[0m')
        else:
            #登陆成功后，开始购物
            uname_of_db=current_userinfo[0]
            balance_of_db=current_userinfo[1]

            print('尊敬的用户[%s] 您的余额为[%s],祝您购物愉快' %(
                uname_of_db,
                balance_of_db
            ))

            tag=True
            while tag:
                for index,product in enumerate(product_list):
                    print(index,product)
                choice=input('输入商品编号购物，输入q退出>>: ').strip()
                if choice.isdigit():
                    choice=int(choice)
                    if choice < 0 or choice >= len(product_list):continue

                    pname=product_list[choice][0]
                    pprice=product_list[choice][1]
                    if balance_of_db > pprice:
                        if pname in shopping_cart: # 原来已经购买过
                            shopping_cart[pname]['count']+=1
                        else:
                            shopping_cart[pname]={'pprice':pprice,'count':1}

                        balance_of_db-=pprice # 扣钱
                        current_userinfo[1]=balance_of_db # 更新用户余额
                        print(pname + " 添加到购物车，余额为： " + str(balance_of_db))

                    else:
                        print("产品价格是{price},你还差{lack_price}".format(
                            price=pprice,
                            lack_price=(pprice - balance_of_db)
                        ))
                    print(shopping_cart)
                elif choice == 'q':
                    print("""
                    ---------------------------------已购买商品列表---------------------------------
                    id          商品                   数量             单价               总价
                    """)

                    total_cost=0
                    for i,key in enumerate(shopping_cart):
                        print('%22s%18s%18s%18s%18s' %(
                            i,
                            key,
                            shopping_cart[key]['count'],
                            shopping_cart[key]['pprice'],
                            shopping_cart[key]['pprice'] * shopping_cart[key]['count']
                        ))
                        total_cost+=shopping_cart[key]['pprice'] * shopping_cart[key]['count']

                    print("""
                    您的总花费为: %s
                    您的余额为: %s
                    ---------------------------------end---------------------------------
                    """ %(total_cost,balance_of_db))

                    while tag:
                        inp=input('确认购买(yes/no?)>>: ').strip()
                        if inp not in ['Y','N','y','n','yes','no']:continue
                        if inp in ['Y','y','yes']:
                            # 将余额写入文件

                            src_file=db_file
                            dst_file=r'%s.swap' %db_file
                            with open(src_file,'r',encoding='utf-8') as read_f,
                                open(dst_file,'w',encoding='utf-8') as write_f:
                                for line in read_f:
                                    if line.startswith(uname_of_db):
                                        l=line.strip('
').split(',')
                                        l[-1]=str(balance_of_db)
                                        line=','.join(l)+'
'

                                    write_f.write(line)
                            os.remove(src_file)
                            os.rename(dst_file,src_file)

                            print('购买成功，请耐心等待发货')

                        shopping_cart={}
                        current_userinfo=[]
                        tag=False
    else:
        print('非法输入')