作业：购物商城

商品展示，价格

买，加入购物车

付款，钱不够

具体实现了如下功能：
　　　　1、可购买的商品信息显示
　　　　2、显示购物车内的商品信息、数量、总金额
　　　　3、购物车内的商品数量进行增加、减少和商品的删除
　　　　4、用户余额的充值
　　　　5、用户购买完成进行结账，将最终余额回写到用户文件中。

一、用户文件说明：

kevin 123 50000sky 123 54000mobi 123 80000

其中第一列为用户名，第二列为密码，第三列为帐户余额。

二、流程图如下：

import sys,os,getpass,time

def input_handle(s):'''用户输入字符数字转化为数字'''if s.isdigit(): #判断用户输入是否是字符数字
 s = int(s) #是的话就进行转换return s

def framework(user="",init_money='',now_money='',recharge_money='',value=''):'''架构函数，展示用户的基本信息'''os.system("clear")
 init_money = int(init_money)
 now_money = int(now_money)
 recharge_money = int(recharge_money)
 message = '''******************************************************************************* 33[32;1m欢迎来到小猪猪购物商城33[0m*******************************************************************************会员：%s	金额：%d	当前余额：%d	充值金额：%d	购物车:%d''' %(user,init_money,now_money,recharge_money,value) print(message)

def goods_list_show(my_dict):'''商品展示模块，用于展示商品'''local_dict = {}'''对商品列表进行遍历并加上数字编号'''i = 1print("商品列表：")
 print("=================================================================================================")
 print("%-5s %-15s %-10s %-10s %-10s" %("编号","商品名称","商品价格(元)","商品总数量(个)","商品剩余数量(个)"))for k in my_dict.keys():
 v = my_dict[k]if type(v) == dict:
 print("%-5s %-20s %-15d %-18d %-10d" %(i,k,v['price'],v['num'],v['sum']))
 local_dict[i] = [k,v["price"],v['num'],v['sum']]
 i += 1print("=================================================================================================")return local_dict

def cart_goods_show(show_dict):'''显示购物车商品,并加上数字编号'''show_all_sum = 0show_all_num = 0'''对商品列表进行遍历并加上数字编号'''message = ('编号',"商品名称","商品价格(元)","商品总数量(个)","购买数量(个)","购买金额(元)")
 print("%-5s 	 %-20s 	 %-10s 	 %-10s 	 %-10s 	 %-10s" %message)for k in show_dict:
 v = show_dict[k]if type(v) is dict:
 print("%-5s 	 %-10s 	 %-10d 	 %-10d 	 %-10d 	 %-10d" %(k,v[0],v[1],v[2],v[3],v[4]))
 show_all_num += v[4]
 show_all_num += 1print("请确认你购买的商品，总金额：%d元"%(show_all_sum))return (show_all_sum,show_all_num)

def cart_goods_modify(modify_dict,modify_goods_dict):'''购物车商品修改列表'''a_flag = 1while a_flag:
 index = input("请输入商品编号|完成修改(q):" %modify_dict[index][2])if len(index) != 0:
 index = input_handle(index)if index == "q":breakelif index in modify_dict:
 b_flag = 1name = modify_dict[index][0]while b_flag:
 num = input("请输入新的商品数量(最大值为%d)|完成修改(q)：" %modify_dict[index][2])if len(num) != 0:
 num = input_handle(num)if num == 'q':breakelif num == 0:
 modify_goods_dict[name]['num'] = modify_dict[index][2]
 del modify_dict[index]
 b_flag = 0elif num > 0 and num <= modify_dict[index][2]:
 modify_dict[index][3] = num
 modify_dict[index][4] = modify_dict[index][1] * num
 modify_goods_dict[name]['num'] = modify_dict[index][2] - num
 b_flag = 0else:
 passelse:
 passreturn (modify_dict,modify_goods_dict)

def shopping_cart_show(my_cart,my_goods_dict):'''购物车展示'''print("欢迎来到你的购物车".center(80,"#"))
 goods_all_sum = 0goods_all_num = 0if my_cart:'''调用购物车商品列表函数,并返回商品总金额和总数量'''(goods_all_sum,goods_all_num) = cart_goods_show(my_cart)
 choice = input("请进行如下操作：修改记录(c)|继续购物(!c)")if choice == "c":
 (my_shop_cart,my_goods_dict) = cart_goods_modify(my_cart,my_goods_dict)
 (goods_all_sum,goods_all_num) = cart_goods_show(my_cart)else:
 passelse:
 print("您当前的购物车为空".center(80,"#"))

 time.sleep(2)return (goods_all_sum,goods_all_num,my_goods_dict)

def balance_recharge(recharge_init_balance,recharge_now_balance,recharge_money):
 recharge_flag = 1while recharge_flag:
 recharge_num = input("请输入充值金额|返回(b)|退出(q)：")if len(recharge_num) != 0:
 recharge_num = input_handle(recharge_num)if recharge_num == "q":
 sys.exit(0)
 elif recharge_num == 'b':breakelif type(recharge_flag) is int and recharge_num > 0:
 recharge_init_balance += recharge_num
 recharge_now_balance += recharge_num
 recharge_money += recharge_num
 recharge_flag = 0print("充值成功，请查收".center(80,"#"))else:
 passreturn (recharge_init_balance,recharge_now_balance,recharge_money)

def user_billing(billing_list,my_cart,billing_balance):'''结帐模块'''print("欢迎来到结帐模块".center(80,"#"))if my_cart:'''调用购物车商品列表函数'''cart_goods_show(my_cart)
 billing_flag = input("请确认是否商品结算(y|n)：")if billing_flag == "y":
 billing_file = open("info.txt",'w')for user_info in billing_list:
 billing_file.writelines(user_info)
 billing_file.close()
 sys.exit("结帐成功，您当前余额：%d".center(80,"#") %billing_balance)else:
 print("退出结算菜单，继续购物".center(80,"#"))
 time.sleep(2)else:
 print("您当前的购物车为空，无需结算！")
 time.sleep(2)'''主程序开始'''if __name__ == "__main__":
 goods_list = { 'iphone6': {'price':6000,'num':10,'sum':10}, 'ipad': {'price':3000,'num':20,'sum':20}, 'mi4': {'price':2000,'num':43,'sum':43}, 'huawei6_plus': {'price':1999,'num':8,'sum':8},
 }
 i = 0while i < 3: #只要用户登录不超过3次就不断循环
 username = input("请输入用户名：")
 password = input("请输入密码：")
 user_file = open("info.txt",'r')
 user_list = user_file.readlines()
 user_file.close()for user_line in user_list:'''分别获取当前账号、密码和余额信息'''user,passwd,init_balance = user_line.strip('
').split()
 init_balance = int(init_balance)
 now_balance = init_balance
 my_goods_sum = 0if user == username and password == passwd:
 user_shopping_cart = {}
 user_shopping_cart_count = 0recharge_value = 0line_num = user_list.index(user_line)
 first_flag = 1while first_flag:'''调用框架函数

输出用户信息'''framework(username,init_balance,now_balance,recharge_value,user_shopping_cart_count) goods_output_dict = goods_list_show(goods_list) #输出商品信息 goods_index = input("请选择菜单：输入商品编号 | 购物车(c) | 余额充值(r) | 结账(b) | 退出(q) :")if len(goods_index) != 0: goods_index = input_handle(goods_index)if goods_index == 'q': sys.exit(0) elif goods_index == 'c':'''调用购物车显示函数，并返回购物车商品总金额'''(my_goods_sum,user_shopping_cart_count,goods_list) = shopping_cart_show(user_shopping_cart,goods_list) now_balance = init_balance - my_goods_sumif now_balance < 0: print("您的余额不足，请及时充值！") time.sleep(2) elif goods_index == 'r': (init_balance,now_balance,recharge_value) = balance_recharge(init_balance,now_balance,recharge_value) elif goods_index == 'b':'''更新用户的余额'''user_list[line_num] = user + ' ' + passwd + ' ' + repr(now_balance) + ' 'user_billing(user_list,user_shopping_cart,now_balance) elif goods_index in goods_output_dict:'''取出goods_index商品列表信息并进行赋值和展示'''(goods_name,goods_price,goods_num) = (goods_output_dict[goods_index][0],goods_output_dict[goods_index][1],goods_output_dict[goods_index][2]) print('【 编号：%-5d 名称：%-15s 价格：%-5d（元） 数量：%-5d（个）】' % (goods_index, goods_name, goods_price, goods_num)) second_flag = 1while second_flag: buy_num = input('请输入购买商品个数(最大值为%d) | 返回(b) | 退出(q): ' % goods_num)if len(buy_num) != 0: buy_num = input_handle(buy_num)if buy_num == 'q': sys.exit(0) elif buy_num == 'b':breakelif type(buy_num) is int and buy_num > 0 and buy_num <= goods_num: my_goods_sum = goods_price * buy_numif my_goods_sum <= now_balance: print('购买商品 %s 总价格为 : %d' % (goods_name, my_goods_sum)) add_flag = input("请确认是否加入购物车（y | n)：")if add_flag == "y":'''判断购物车不存在该商品'''if goods_index not in user_shopping_cart: user_shopping_cart_count += 1'''购物车商品数量加一'''user_shopping_cart[goods_index] = [goods_name,goods_price,goods_num,buy_num,my_goods_sum]else: user_shopping_cart[goods_index][3] += buy_num user_shopping_cart[goods_index][4] += my_goods_sum now_balance -= my_goods_sum goods_list[goods_name]['num'] -= buy_num second_flag = 0else:breakelse: print("您的余额不足，请充值或重新选择，谢谢！") time.sleep(2)else: passelse: passelse:if i != 2: print('用户或密码错误，请重新输入，还有 %d 次机会' % (2 - i)) i += 1else: sys.exit('用户或密码输入错误超过三次，退出系统,欢迎下次光临')

上述代码不难，难的是思路，思路很重要，要知道如何一步一步去操作，用的也都是我们常用的知识，其实归根揭底我们写程序，大部分使用的都是字符串，字典，列表的功能。还有一些模块之类的。在写程序的过程中，思路显得尤为重要。知道了思路，就考虑如何使用代码去实现，上面程序中学到了如下知识点；

1、输出格式对其：print("%-5s %-15s %-10s %-10s %-10s" %("编号","商品名称","商品价格(元)","商品总数量(个)","商品剩余数量(个)"))，上面代码能够实现对其格式的功能，让我们输出的字符串格式统一，比如上述代码中，编号左对齐5个字符，商品名称左对齐15个字符等等；

2、str.center()的使用，如print("欢迎来到你的购物车".center(80,"#"))；

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