Pythonのショッピングカートのプログラムコード

''''' 
Created on 2017年9月4日 
 
@author: len 
''' 
 
 
product_list = [ 
  ('Robot',200000), 
  ('MacPro',12000), 
  ('Iphone8',8888), 
  ('Hello World',1200), 
        ]  
shopping_list = [] 
user_salary=input("请输入你的工资：") 
if user_salary.isdigit(): 
  user_salary = int(user_salary) 
  while True: 
    print("商品如下：") 
    for index,item in enumerate(product_list):  
       
      print (index,item) 
    user_choice = input("请输入要购买的商品编号：") 
    if user_choice.isdigit(): 
      user_choice = int(user_choice) 
      if user_choice < len(product_list) and user_choice > -1: 
        p_item = product_list[user_choice] 
        if user_salary>=p_item[1]: 
          shopping_list.append(p_item) 
          user_salary-=p_item[1] 
          print("购买商品",p_item,"成功您的余额为",user_salary,"元！" ) 
        else: 
          print("您的余额为",user_salary,"余额不足以购买此商品，购买失败！") 
               
      else: 
        print("并无此产品！") 
    elif user_choice == "q": 
      print("--------shopping list-------") 
      for i in shopping_list: 
        print(i) 
      exit() 
    else: 
      print("invalidate！！！")