Python:如何正确循环？

Question

我试图让嵌套循环正常工作，但我有很多麻烦。 我有一个列表的工作代码，但我想添加一个else语句，声明一个选项无效，然后再试一次，然后退出并返回到第一个循环，但我似乎无法让它工作，如果它不重复无效的打印代码列表中的每一项。 有人能告诉我我做错了什么吗？ 工作原理：

myNames = ["Jim", "Sarah", "Jason", "Lynne", "Ginny", "Joe", "Susan"]
myScores = [88, 92, 95, 84, 85, 92, 89]

print ("Student names: Jim, Sarah, Jason, Lynne, Ginny, Joe, Susan")
name = input("Please enter a students name to find their score or q to quit: ")

while name != 'q':
        for x in range(7):
            if myNames[x] == name:
                print(myNames[x])
                print(myScores[x])
        name = input("Please enter a students name to find their score or q to quit: ")

什么不起作用：

myNames = ["Jim", "Sarah", "Jason", "Lynne", "Ginny", "Joe", "Susan"]
myScores = [88, 92, 95, 84, 85, 92, 89]

print ("Student names: Jim, Sarah, Jason, Lynne, Ginny, Joe, Susan")
name = input("Please enter a students name to find their score or q to quit: ")

while name != 'q':
        for x in range(7):
            if myNames[x] == name:
                print(myNames[x])
                print(myScores[x])
            else:
                print("Invalid name please try again")
        name = input("Please enter a students name to find their score or q to quit: ")

Answer 1

您的程序将根据每个可接受的名称检查输入的名称，并为每个不匹配的名称打印一条消息。相反，只有在比较失败时才需要打印消息。有一种方法：

myNames = ["Jim", "Sarah", "Jason", "Lynne", "Ginny", "Joe", "Susan"]
myScores = [88, 92, 95, 84, 85, 92, 89]

print ("Student names: Jim, Sarah, Jason, Lynne, Ginny, Joe, Susan")
name = input("Please enter a students name to find their score or q to quit: ")

while name != 'q':
        for x in range(7):
            if myNames[x] == name:
                print(myNames[x])
                print(myScores[x])
                break
        else:
            print("Invalid name please try again")
        name = input("Please enter a students name to find their score or q to quit: ")

break语句在执行时立即退出循环。在Python中for:else：construct，else:分支仅当循环在其元素中一直运行而从未碰到break语句时才执行。因此，只有当比较失败时才会打印错误消息