<p>我正在做一个登录系统。它要求用户回答问题(“你已经有账户了吗?”)虽然答案不是“是”还是“否”,但它应该继续询问。在</p>
<pre><code>print('Welcome to the quiz!')
print('Do you already have an account? ')
have_acc = input()
while have_acc != ('Yes') or have_acc != ('No') or have_acc != ('yes') or have_acc != ('no'):
print('Please enter Yes or No')
have_acc = input()
</code></pre>
<p>输出</p>
^{pr2}$