Python代码if语句失效：输入‘no’无法终止问答程序的问题

问题原因 #

你这段代码的问题出在缩进错误：你仅将print("Let's play! ")和score = 0纳入了if playing.lower() == "yes"的代码块，而后续所有的问答、得分计算逻辑都在if块之外。Python靠缩进区分代码块，不在if块内的代码会无条件执行，所以不管你输入yes还是no，问答环节都会强制运行。

修改方案 #

把所有问答流程、结果输出的代码都缩进，放到if的代码块内部；同时可以添加else分支，处理用户输入no的场景：

print("Welcome to my quiz page!")
playing = input("Do you want to play? ")
if playing.lower() == "yes":   
    print("Let's play! ")
    score = 0

    answer = input("What is the capital of Japan? ")
    if answer.lower() == "tokyo":
        print("Correct!")
        score += 1
    else:
        print("Incorrect!")

    answer = input("What is a female Japanese dress called? ")
    if answer.lower() == "kimono":
        print("Correct!")
        score += 1
    else:
        print("Incorrect!")

    answer = input("What are Japanese gang members called? ")
    if answer.lower() == "yakuza":
        print("Correct!")
        score += 1
    else:
        print("Incorrect!")

    print("You've got " + str(score) + " questions correct!")
    print("You've got " + str((score / 3) * 100) + "%")
else:
    print("Okay, maybe next time!")

这样修改后，只有用户输入yes时才会启动问答流程；输入no（或其他非yes内容）时，程序会输出提示后直接终止。

内容的提问来源于stack exchange，提问作者Wii