如何将空输入计为其他

Question

我是 python 新手，正在上课。下面是我的代码。我的问题是在我想要的最后一行，这样如果有人简单地按下回车，它就会被视为有人输入了（1/2/3 或 4）以外的输入，这基本上会用最后一个 elif 回复并重新启动问题.但目前它给了我这个：

SyntaxError: unexpected EOF while parsing. 

有人可以帮忙吗？

def menu_loop():
    ans = True
    while ans:
        print("""
        1. My freedom awaits me, give me my blade!
        2. I've never fought before, might you help me?
        3. I have already forsaken freedom, I will fight till the death.
        4. Fighting is for the wicked. I refuse to fight.

        Press enter to quit
        """)

        ans= input("What would you like to do now?")
        if ans == 1:
            main_loop()
            break
        elif ans == 2:
            instructions_loop()
            break
        elif ans == 3:
            gauntlet_loop()
            break
        elif ans == 4:
            print("\nMen... come relieve this man of his life.")
            time.sleep(2)
            end_game_loop()
            break
        elif ans == '': 
            print("\nDo you not speak Latin, slave?")

谢谢，感谢Christian，我找到了答案。我猜我从 Python 3 获得指示的网站是 Python 3，而我在 2（这是为了大学作业）。现在正在运行，非常感谢！

Answer 1

将最后一个 elif 条件改为elif not ans

def menu_loop():
    ans = True
    while ans:
        print("""
        1. My freedom awaits me, give me my blade!
        2. I've never fought before, might you help me?
        3. I have already forsaken freedom, I will fight till the death.
        4. Fighting is for the wicked. I refuse to fight.

        Press enter to quit
        """)

        ans = input("What would you like to do now?")
        if ans == 1:
            main_loop()
            break
        elif ans == 2:
            instructions_loop()
            break
        elif ans == 3:
            gauntlet_loop()
            break
        elif ans == 4:
            print("\nMen... come relieve this man of his life.")
            time.sleep(2)
            end_game_loop()
            break
        elif not ans: 
            print("\nDo you not speak Latin, slave?")

编辑：答案是针对 python 3。 对于 python 2.7，使用 raw_input 代替 input，并相应地使用 int(ans) 或字符串文字。

Answer 2

使用raw_input 而不是input。 input 将尝试评估输入，评估空字符串会引发错误。 raw_input 不评估，只是给你一个字符串。见this explanation。

def main_loop():
    pass
def instructions_loop():
    pass
def gauntlet_loop():
    pass
def end_game_loop():
    pass

next_loop_func = {
    '1': main_loop, 
    '2': instructions_loop, 
    '3': gauntlet_loop,
    '4': end_game_loop,
}
def menu_loop():
    while True:
        print("""
        1. My freedom awaits me, give me my blade!
        2. I've never fought before, might you help me?
        3. I have already forsaken freedom, I will fight till the death.
        4. Fighting is for the wicked. I refuse to fight.

        Press enter to quit
        """)

        ans = raw_input("What would you like to do now?")
        if ans in next_loop_func:
            next_loop_func[ans]
        else: 
            print("\nDo you not speak Latin, slave?")


menu_loop()

Answer 3

如果您使用的是 python 2，请更改：

ans = input("What would you like to do now?")

到：

ans = raw_input("What would you like to do now?")  

raw_input 返回一个字符串，而输入返回一个 integer 这在 python 3 中已更改，在 3 中只有 input 并且它返回一个字符串

因此，如果您使用的是 python 2，请将其更改为 raw_input，然后像这样调用您的其他条件：

if int(ans) == 1:
    main_loop()
    break