类型错误:% 不支持的操作数类型:'NoneType' 和 'str'

问题描述

所以我对编程非常陌生，我从 Python 3 开始.我开始阅读Learn Python the Hard Way".现在，我得到了这段代码:

So I am VERY new to programming and I started with Python 3. I started reading "Learn Python the Hard Way". Now, I got to a point where I had this code:

x = "There are %d types of people." % 10
binary = "binary"
do_not = "don't"
y = "Those who know %s and those who %s" % (binary, do_not)

print(x)
print(y)
print("I said: %r") % x

我不太清楚%r、%s 和%d 之间的区别.我得到的错误是 TypeError: unsupported operand type(s) for %: 'NoneType' and 'str' 不知道该怎么做以及如何修复它.请解释我如何才能真正使它工作以及为什么它不起作用.另外，%r,d 和 s 有什么区别?任何有用的链接?提前致谢.

I do not really know the difference between %r, %s and %d. The error I get is TypeError: unsupported operand type(s) for %: 'NoneType' and 'str' No idea what to do and how to fix it. Please explain how I can actually make it work and why it won't work. Also, what is the difference between %r,d and s? Any useful links? Thank you in advance.

推荐答案

您想将 % 应用于 string 代替:

You want to apply % to the string instead:

print("I said: %r" % x)

您的代码将其应用于 print() 调用的返回值，该调用返回 None.

Your code is applying it to the return value of the print() call, which returns None.

或者，您可以切换到使用 str.format():

Alternatively, you can switch to using str.format():

print("I said: {!r}".format(x))

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