Python 类型错误：% 不支持的操作数类型：'NoneType' 和 'str'
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TypeError: unsupported operand type(s) for %: 'NoneType' and 'str'
提问by user3586591
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:
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，我到了我有这个代码的地步：
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
I do not really know the difference between %r, %sand %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.
我真的不知道%r,%s和之间的区别%d。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解决它。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？先感谢您。
回答by Martijn Pieters
You want to apply %to the stringinstead:
要应用%到的字符串，而不是：
print("I said: %r" % x)
Your code is applying it to the return value of the print()call, which returns None.
您的代码将其应用于print()调用的返回值，该调用返回None.
Alternatively, you can switch to using str.format():
或者，您可以切换到使用str.format()：
print("I said: {!r}".format(x))
回答by A.J. Uppal
You are calling the %outside of the print()function. This tries to see if the actual function printcan be printed as %r, and because printdoesn't return anything, it tries to get %rfor the value None(hence the NoneTypeerror). Change it to:
您正在调用函数的%外部print()。这会尝试查看实际函数是否print可以打印为%r，并且由于print不返回任何内容，因此它尝试获取%r该值None（因此出现NoneType错误）。将其更改为：
print("I said: %r" %(x))
The following code:
以下代码：
#!/usr/local/bin/python3
x = "Hello"
print ("Hello World! %s") %(x)
Raises the following error:
引发以下错误：
Hello World! %s
Traceback (most recent call last):
File "main.py", line 3, in
print ("Hello World! %s") %(x)
TypeError: unsupported operand type(s) for %: 'NoneType' and 'str'
Changing the code to the following works:
将代码更改为以下工作：
#!/usr/local/bin/python3
x = "Hello"
print ("Hello World! %s" %(x))
Output:
输出：
Hello World! Hello
