[Python-Dev] RFC: PEP 460: Add bytes % args and bytes.format(args) to Python 3.5 (original) (raw)

Cameron Simpson cs at zip.com.au
Sat Jan 11 05:14:25 CET 2014

On 11Jan2014 00:43, Juraj Sukop <juraj.sukop at gmail.com> wrote:

On Fri, Jan 10, 2014 at 11:12 PM, Victor Stinner <victor.stinner at gmail.com>wrote: > What not building "10 0 obj ... stream" and "endstream endobj" in > Unicode and then encode to ASCII? Example: > > data = b''.join(( > ("%d %d obj ... stream" % (10, 0)).encode('ascii'), > binaryimagedata, > ("endstream endobj").encode('ascii'), > ))

The key is "encode to ASCII" which means that the result is bytes. Then, there is this "11 0 obj" which should also be bytes. But it has no "binaryimagedata" - only lots of numbers waiting to be somehow converted to bytes. I already mentioned the problems with ".encode('ascii')" but it does not stop here. Numbers may appear not only inside "streams" but almost anywhere: in the header there is PDF version, an image has to have "width" and "height", at the end of PDF there is a structure containing offsets to all of the objects in file. Basically, to ".encode('ascii')" every possible number is not exactly simple or pretty.

Hi Juraj,

Might I suggest a helper function (outside the PEP scope) instead of arguing for support for %f et al?

Thus:

def bytify(things, encoding='ascii'): for thing: if isinstance(thing, bytes): yield thing else: yield str(thing).encode('ascii')

Then one's embedding in PDF might become, more readably:

data = b' '.join( bytify( [ 10, 0, obj, binary_image_data, ... ] ) )

Of course, bytify might be augmented with whatever encoding facilities might suit your needs.

Cheers,

Cameron Simpson <cs at zip.com.au>

We tend to overestimate the short-term impact of technological change and underestimate its long-term impact. - Amara's Law

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