在while循環中使用kwargs - Python 3

Question

在下面的代碼中，我試圖檢查一個值（b）是否是kwargs中的一個鍵，如果是，則執行其餘部分。

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，當我嘗試運行代碼時，它總是隻允許一個選項。我發現很難解釋，所以我會舉一個例子：

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 

它不會接受石，即使它在字典中，但是，它將接受藥水。其他時候，這將是另一種方式。

起初我以爲是因爲它是在一個while循環中，但現在我不太確定，而且我找不到任何可以幫助我在其他地方找到的東西。

對不起，如果這是非常具體的，但這給我很多麻煩。

Answer 1

當你遍歷所有的項目都打印出來：

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

的i變量最終持有kwargs的最後一個項目的名稱。這就是爲什麼它適用於'魔藥'而不是'石頭'。

正如穆罕默德回答，您需要檢查所有kwargs中的項目，而不僅僅是最後一個。

Answer 2

這可能是更好地分解成一個try..except條款：

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()