Python: What Does The Two % Signs In Print '%r K%%k'%'a' Do?

I came across this while researching quines. I am curious to know what %% does in the following print '%r k%%k'%'a' I understand that %r takes the string representation of the argu

Solution 1:

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

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

See the String Formatting Operations documention:

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

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