Python:打印'％r k %% k'％'a'中的两个％符号做什么? [英] Python: What does the two % signs in print '%r k%%k'%'a' do?

问题描述

我在研究奎因时遇到了这个问题.我很想知道以下%%的行为

I came across this while researching quines. I am curious to know what %% does in the following

print '%r k%%k'%'a'

我知道％r接受传递的参数的字符串表示形式(在这种情况下为'a')，并将其添加到带引号的字符串中，因此在这种情况下，它会输出'a'k％k.我不知道k %% k是做什么的?如果删除％符号之一，则会出现错误.如果我都没有％r，我也会得到一个错误.但是，当我在ks(或任何字母)之间同时有％r和两个％符号时，它会打印出几乎相同的内容，但缺少一个％(在这种情况下，k％k为k %% k).这是怎么回事?

I understand that %r takes the string representation of the argument that's passed (in this case 'a') and adds it to the string with quotes, so in this case it prints 'a' k%k. I can't figure out what k%%k does? If I remove one of the % signs, I get an error. If I have both without the %r, I get an error too. However, when I have both %r and the two % signs in between to ks (or any alphabet), it prints out nearly the same thing, but with one % missing (k%k in this case for k%%k). What is happening here?

推荐答案

%%是单个%字符的转义符；您不能使用该字符:

%% is the escape for a single % character; you could not otherwise use that character:

>>> '%s: %%' % 'One percent character'
'One percent character: %'

请参见 字符串格式设置操作记录:

%
不转换任何参数，结果为'%'字符.

%
No argument is converted, results in a '%' character in the result.

通过删除一个%字符，您形成了%k格式，但是没有转换类型k.该错误消息反映出:

By removing one % character, you formed the %k format, but there is no conversion type k. The error message reflects that:

>>> '%k' % 'No such format type'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: unsupported format character 'k' (0x6b) at index 1

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