python3的循环问题

Question

我正在为我正在编写的一个小程序的一部分代码苦苦挣扎。请记住，我对此很陌生。

代码如下：

def sell():
    sell = input("\nGreetings! What would you like to do today?\nPress 1 to sell an animal\nPress 2 to buy an animal\nPress 3 If you want to see all the farms and their animals first\n")

    if sell == "1":
        whichs = input("Which animal do you want to sell?\nPress 1 for pig\nPress 2 for horse\nPress 3 for cow\nPress 4 for bull\n")
        if whichs == "1":
            print ("\nYou just sold\n",p[0])
            print ("\nYou now have 350gold")
            print ("\nThese are the animals you have left:")
            print (p[1], p[2], p[3]) #Prints the animals you have left from p list.
        elif whichs == "2":
            print ("\nYou just sold\n",p[1])
            print ("\nYou now have 350gold")
            print ("\nThese are the animals you have left:")
            print (p[0], p[2], p[3])
        elif whichs == "3":
            print ("\nYou just sold\n",p[2])
            print ("\nYou now have 360gold.")
            print ("\nThese are the animals you have left:")
            print (p[0], p[1], p[3])
        elif whichs == "4":
            print ("\nYou just sold\n",p[3])
            print ("\nYou now have 350gold.")
            print ("\nThese are the animals you have left:")
            print (p[0], p[1], p[2])
        else:
            print ("Error")

我希望这个循环，所以当用户卖掉一只动物时，他们会重新开始：

sell = input("\nGreetings! What would you like to do today?\nPress 1 to sell an animal\nPress 2 to buy an animal\nPress 3 If you want to see all the farms and their animals first\n")

我正在为如何做到这一点而苦苦挣扎。

Answer 1

其他两个答案告诉您使用 while 循环是正确的，但未能解决更普遍的问题：循环不应在 sell 函数的内部，而应在其外部，因为您的文字表明用户还可以购买东西或查看他的统计信息。您应该为所有这些动作创建单独的函数，然后创建一个循环来检查动作并调用适当的函数：

def buy():
    #...

def sell():
    #...

def stats():
    #...

while True:
    choice = input("1: Buy 2:Sell 3:Stats - press any other key to exit")
    if choice == "1": buy()
    elif choice == "2": sell()
    elif choice == "3": stats()
    else: break

可以通过使用更多的 Python 方法来优化循环，例如将选择映射到字典中的函数，但为了清楚起见，我用简单的 if 编写了它。

此外，如果您不选择将所有状态保存在全局变量中（您不应该这样做），那么将函数放入一个同时保存当前余额、库存和其他游戏参数的类中是有意义的.

Answer 2

def sell():
    looping = True

    while looping:
        sell = input("\nGreetings! ... Press Q for quit")

        if sell == "1":
            #rest of your code
        elif sell == "Q":
            looping = False

Answer 3

尝试使用while 循环：

def sell_function():
    while True:
        sell = input("\nGreetings! What would you like to do today?\nPress 1 to sell an animal\nPress 2 to buy an animal\nPress 3 If you want to see all the farms and their animals first\n")
        # ...
            else:
                print("Error")
                break        # Stop looping on error

我们也可以将变量设置为True，完成while variable，然后使用variable = False 而不是break，以获得相同的效果（在本例中）。

我重命名了您的函数，因为您使用了一个名为 sell 的变量并且有一个同名的函数，这可能会导致问题。此外，毫无疑问，您稍后会发现 break 和 continue 语句很有用。