On 02/24/2014 02:33 PM, Nick Coghlan wrote:
Allowing %a also improves the consistency with text interpolation. In the case
of %r, the inconsistency is based on
needing to disallow arbitrary Unicode code points in the result and not wanting
to redefine %r as a second way to spell
%a. There's no corresponding reason to disallow %a - the result is guaranteed
to be ASCII compatible, so there's no risk
of data driven encoding errors, and no difference between doing the binary
interpolation directly, or doing text
interpolation and then encoding the result as ASCII.
As far as use cases go, as someone else mentioned, the main one is likely to be
binary logging and error reporting
formats, as it becomes a quick and easy way to embed a backslash escaped
string. However, my interest is more in
providing an obvious way to do it and in minimising the differences between
text and binary interpolation.
Jim Jewett had some use-cases that I'm happy to run with. (Thanks jJ!)
So final question for %a:
%a can only be used in Python 3 (3.2+, I believe) -- do we want to be able to
use %a as a short way of including text?
In Python2/3 code bases it will need to be '%s' % 'a string'.encode('ascii').
In Python 3 only code bases that could be shortened to '%a' % 'a string':
pro: much easier
if "mojibake" ( \x and \u sequences ) sneak in, the original data can
still be retrieved
cons: has surrounding quotes (would need to have bytes.__mod__ remove them)
--
~Ethan~
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