Python：while循環/控制語句沒有達到想要的結果，我該如何解決這個問題？

Question

cost = int(input("Enter the cost:\n")) 
payment = int(input("Deposit a coin or note:\n")) 

if payment >= cost: 
    change = payment - cost 
    print (change) 

elif payment < cost: 
    while payment < cost: 
     payment = int(input("Deposit a coin or note:\n")) 
     change = cost - payment 
     print (change) 
     break 

我基本上想要「改變」的價值。

以上是錯誤的，因爲它不是'存儲'第一次付款的價值，如果它低於成本，意識到我的壞錯誤。

cost = int(input("Enter the cost:\n")) 
payment = 0 
while payment < cost: 
    firstpayment = int(input("Deposit a coin or note:\n")) 
    payment = payment + firstpayment 
    if payment > cost: 
     change = payment - cost 
     print ("Your change is: $",change) 

Answer 1

循環條件說：

while payment< cost: 

所以，當支付比成本更環路會自動存在。因此，一個更簡單的方法將是，

while payment<cost: 
    #do something 
change = payment-cost 

表兄弟姐妹，當循環結束時，我們知道，支付應> =成本...