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

Paul Moore p.f.moore at gmail.com
Sun Jan 12 18:26:15 CET 2014

On 12 January 2014 17:03, Ethan Furman <ethan at stoneleaf.us> wrote:

We know full well the difference between unicode and bytes, and we know full well that numbers and much of the text we need has an ASCII (bytes!) representation. When we do a b'Content Length: %d' % len(binarydata) we are expecting to get back a bytes object, /not/ a unicode object.

What I am struggling to understand here is what room for compromise there is. Clearly, for whatever reason,

b'Content Length: ' + str(len(binary_data)).encode('ascii'))

is not acceptable for you. OK, fair enough. Also, apparently, writing a helper

def int_to_bytes(n): return str(n).encode('ascii')

b'Content Length: ' + int_to_bytes(len(binary_data))

is unacceptable. But I'm not clear why it's unacceptable. Maybe I missed the explanation - God knows, the thread is long enough :-)

On the other hand, Nick has explained why b'Content Length: %d' % len(binary_data) is unacceptable to him (you don't have to agree with his opinion, just concede that he has explained his position in a way that you understand).

I'm not trying to argue you're wrong - I don't know your codebase, nor do I know your application area. But surely somewhere between "we must have % formatting including %d for bytes" and the above, there's a middle ground that you are willing to accept? Can you give any indications of what that might be? What, specifically, about the helper function is the problem? I don't think it is any less space efficient, it doesn't double-encode, and I don't think it's more difficult to understand (although it is a little longer, it trades that off against being a bit more explicit as to what's going on). Surely you're not arguing that your code must work unchanged (not "there's a way of writing the code so it works on Python 2 and 3", but "the code you currently have for Python 2 must work with no changes at all")?

Can you give an example of code that is nearly acceptable to you, which works in Python 2 and 3 today, and explain what improvements you would like to see to it in order to use it instead of waiting for a core change?

Paul

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