在while循环中使用kwargs - Python 3

Question

在下面的代码中，我试图检查一个值（b）是否是kwargs中的一个键，如果是，则执行其余部分。

def shop(**kwargs): 
    buy = 1 
    print ("Welcome to the shop!") 
    for i, v in kwargs.items(): 
     print (" ", i, ": ", v) 
    while buy == 1: 
     b = input ("What would you like to buy? ").lower() 
     if b == i.lower(): 
      if v <= Player.gold: 
       Player.gold -= v 
       Player.inv_plus(i) 
       print ("You bought ", i, "for ", v, "gold!") 
       print ("Your gold: ", Player.gold) 
       print (Player.show_inv()) 
       print() 
      else: 
       print ("You don't have enough gold!") 
       print() 
     elif b == "exit": 
      buy = 0 
     else: 
      print ("We don't sell that item!") 
      print() 

shop(Stone=5, Potion=10) 

但是，当我尝试运行代码时，它总是只允许一个选项。我发现很难解释，所以我会举一个例子：

Welcome to the shop! 
    Stone : 5 
    Potion : 10 
What would you like to buy? stone 
We don't sell that item! 

What would you like to buy? potion 
You bought Potion for 10 gold! 
Your gold: 0 
Inventory: 
    Potion 6 
    Stone 2 

它不会接受石，即使它在字典中，但是，它将接受药水。其他时候，这将是另一种方式。

起初我以为是因为它是在一个while循环中，但现在我不太确定，而且我找不到任何可以帮助我在其他地方找到的东西。

对不起，如果这是非常具体的，但这给我很多麻烦。

Answer 1

当你遍历所有的项目都打印出来：

for i, v in kwargs.items(): 
    print (" ", i, ": ", v) 

的i变量最终持有kwargs的最后一个项目的名称。这就是为什么它适用于'魔药'而不是'石头'。

正如穆罕默德回答，您需要检查所有kwargs中的项目，而不仅仅是最后一个。

Answer 2

这可能是更好地分解成一个try..except条款：

def shop(**kwargs): 
    buy = 1 
    print ("Welcome to the shop!") 
    for i, v in kwargs.items(): 
     print (" ", i, ": ", v) 
    while True: 
     b = input ("What would you like to buy? ").lower() 
     if b == 'exit': 
      break 
     try: 
      v = kwargs[b.capitalize()] 
     except KeyError: 
      print ("We don't sell that item!") 
      print() 
      continue 
     if v <= Player.gold: 
      Player.gold -= v 
      Player.inv_plus(i) 
      print ("You bought ", b, "for ", v, "gold!") 
      print ("Your gold: ", Player.gold) 
      print (Player.show_inv()) 
      print() 
     else: 
      print ("You don't have enough gold!") 
      print()