[Python-Dev] PEP 460: allowing %d and %f and mojibake

Kristján Valur Jónsson kristjan at ccpgames.com
Sat Jan 11 20:40:31 CET 2014

Hi there.
How about a compromise?
Personally, I think adding the full complement of integer/float formatting to bytes is a bit over the top.
How about just supporting two format specifiers?
%b : interpolate a bytes object.  If it doesn't have the buffer interface, error.
%s : interpolate a str object, encoded to ASCII using 'strict' conversion.  

This should cover the most common use cases.
In particular, you could do this:

Headers.append('Content-Length: %s'%(len(data),))

And then subsequently:
Packet = b'%b%b'%(b"join(headers), data)

For more complex formatting, you delegate to the more capable string class, but benefit from automatic ASCII conversion:

Data = b"percentage = %s" % ("%4.2f" % (value,))

I think interpolating bytes objecst is very important.  And support for automatic ASCII conversion in the process will help us cover all of the numeric use cases.


-----Original Message-----
From: Python-Dev [mailto:python-dev-bounces+kristjan=ccpgames.com at python.org] On Behalf Of Victor Stinner
Sent: 11. janúar 2014 17:42
To: Python Dev
Subject: [Python-Dev] PEP 460: allowing %d and %f and mojibake


I'm in favor of adding support of formatting integer and floatting point numbers in the PEP 460: %d, %u, %o, %x, %f with padding and precision (%10d, %010d, %1.5f) and sign (%-i, %+i) but without alternate format ("{:#x}"). %s would also accept int and float for convenience.

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