购物系统

0）登录能力，每个用户随机初始化余额， 自行初始化一些商品(dict 字典)
1）菜单功能：充值，给当前用户充值
2）菜单功能：购买商品，购买商品以后要扣钱，如果钱不够，则不能购买
3) 退出系统，打印出已经本次购买的商品和花了多少钱

user_info = {}                                                                    
user_info[101] = {"name":"hua1","pwd":"123456","balance":0}                       
user_info[102] = {"name":"hua2","pwd":"123456","balance":0}                       
user_info[103] = {"name":"hua3","pwd":"123456","balance":0}                       
user_info[104] = {"name":"hua4","pwd":"123456","balance":0}                       
username = input("请输入用户名：").strip()                                               
userpwd = input("请输入密码：").strip()                                                 
flag = False                                                                      
userid = ""                                                                       
for key in user_info:                                                             
#print(key)                                                                       
    if user_info[key]['name']== username:                                         
        if userpwd == user_info[key]['pwd']:                                      
            print("已登录")                                                          
            userid = key                                                          
        else:                                                                     
            print("用户名或密码错误")                                                     
            exit()                                                                
        flag = True                                                               
        break                                                                     
if flag == False:                                                                 
    print("用户名或密码错误")                                                             
    exit()                                                                        
#print(user_info)                                                                 
fruit_info = {}                                                                   
fruit_info["apple"] = 10                                                          
fruit_info["banana"] = 20                                                         
fruit_info["orange"] = 30                                                         
fruit_info["Grape"] = 20                                                          
fruit_info["Pear"] = 10                                                           
#print(fruit_info)                                                                
user_info[userid]['balance']=int(input("请输入充值金额:").strip())                       
print("当前账户余额：",user_info[userid]['balance'])                                     
print("商品信息：",fruit_info)                                                         
fruit = input("请选择需要的商品:").strip()                                                
#print(fruit_info[fruit])                                                         
if fruit_info[fruit] <= user_info[userid]['balance']:                             
    print("购买成功")                                                                 
    user_info[userid]['balance']=user_info[userid]['balance']-fruit_info[fruit]   
    print("您购买的商品是:", fruit)                                                      
    print("当前账户余额为：", user_info[userid]['balance'])                               
    exit()                                                                        
else:                                                                             
    print("余额不足，请充值")