[Python-Dev] PEP 460: allowing %d and %f and mojibake (original) (raw)

Glenn Linderman v+python at g.nevcal.com
Sun Jan 12 02:10:37 CET 2014

On 1/11/2014 1:50 PM, Ethan Furman wrote:

Perhaps that's the problem. According to the docs: ======================================================================== object.bytes(self)

Called by bytes() to compute a byte-string representation of an object. This should return a bytes object. ======================================================================== Obviously, with the plethora of different binary possibilities for representing a number (how many bytes? endianness? which complement?), we would be well within our rights to decide that the "byte-string representation" of the numeric types is the ASCII equivalent of their repr or str, and implement bytes appropriately for them. Any other object that wants to be represented easily in a byte stream would also have to implement bytes. If necessary we could add bytes to str for /strict/ ASCII conversion (even latin-1 would have to be explicitly encoded)[1].

In spite of Victor's explanation of internals, which I didn't understand, this sounds like a very interesting idea, conceptually, that any object could implement its __bytes__representation.

On the other hand, it would probably have to be parameterized in the general case: for binary data values, one protocol or format may wish the data to be big-endian, and another may wish the data to be little-endian; for str, one protocol or format may require one encoding and another may require a different encoding, even (as for email) for different parts of the message. So it could be somewhat complex, yet would be very powerful in allowing complex objects, made up of other objects, some of which might have a variety of potential bytes formats (think TIFF files, for example) to convert themselves into a stream of bytes that fits the standard. On the flip side, one would want to convert the stream of bytes into the set of objects, which is a parsing problem.

This is a bit beyond what can be done automatically, just by calling bytes with no parameters, though.

What it may be, though, is a meta-operation from which the needed bytes operations can be determined. It may also not be an easy "compatible with existing Python 2 code with minor tweaks" solution, either. It would be more like a pickle protocol, but pickle defines its own formats, and thus is useless for creating standard formats.

I guess it would belong on python-ideas. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.python.org/pipermail/python-dev/attachments/20140111/0a8e52c3/attachment.html>

More information about the Python-Dev mailing list