重复行消失，while循环问题答案

【问题标题】：Recurring line disappearance, issue with while loop重复行消失，while循环问题
【发布时间】：2019-07-23 01:54:47
【问题描述】：

*我是python新手，所以要温柔...

总体问题：我最近编写的多个代码存在问题，其中行被跳过，这显然是我的错误。我知道我一定是搞砸了一些东西，但我只是没有看到它。我最近的一期可以在这里找到：Is there any reason Python would skip a line?

现在，我想编写一个预售有限数量门票的应用程序。以下是条件：

“每个买家最多可以购买4张门票。共有15张门票可供预售。程序应提示用户他们要购买的门票数量，然后显示数量剩余门票。重复直到所有门票都售完，然后显示买家总数。"

正在发生类似的问题。

buy = int()
ticket_num = 15
buyers = 0

while ticket_num > 0:
    buy = int(input("How many tickets would you like to purchase? "))
    if buy > 4:
        print("You cannot buy that many (4 max).")
        buy = input("How many tickets would you like to purchase? ")
    else:
        ticket_num = ticket_num - buy
        print("There are currently", ticket_num, "remaining.")
        buyers = buyers + 1

print() 

print("The total number of buyers was:", buyers)

似乎没有读取“else”结构中的打印行，我不太明白为什么......

谁能帮我了解一下我的总体误解是什么......？

【问题讨论】：

标签： python if-statement while-loop

【解决方案1】：

我想通了。我对这个问题有一些不正确的地方：

我没有足够的条件语句 (elif) 来满足要求
我不需要在 if 语句中让 buy 变量再次收集输入，因为 while 循环已经导致程序再次提示输入。
我根本不需要将 buy 变量放在 while 循环之外，我只需在“if”语句中使用它之前对其进行初始化。

解决方法如下：

tickets = 15
buyers = 0
print("There are currently", tickets, "tickets available.")

while tickets > 0 :
    buy = int(input("How many tickets would you like to purchase? "))
    if buy <= 4 and tickets - buy >= 0:
        tickets = tickets - buy
        buyers = buyers + 1
        print("There are", tickets, "tickets remaining.")
    elif buy > 4:
        print("You cannot buy that many (4 max).")
    elif tickets - buy < 0:
        print("You can only buy what remains. Please see previous 'remaining' message.")

print()
print("There was a total of", buyers, "buyers.")

【讨论】：

【解决方案2】：

buy = int()
ticket_num = 15
buyers = 0

while ticket_num > 0:
    buy = int(input("How many tickets would you like to purchase? "))
    if buy > 4:
        print("You cannot buy that many (4 max).")
        #buy = input("How many tickets would you like to purchase? ")
    else:
        if ticket_num - buy>=0:
            ticket_num = ticket_num - buy
            print("There are currently", ticket_num, "remaining.")
            buyers = buyers + 1
        else:
            print("There are currently", ticket_num, "remaining. You can buy up to", ticket_num, "tickets")
print()

print("The total number of buyers was:", buyers)

这里是解决方案。问题是你得到了两次输入。首先在while下面。其次是 if 语句。

【讨论】：