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

Eric V. Smith eric at trueblade.com
Sat Jan 11 02:53:09 CET 2014

On 1/10/2014 8:12 PM, Antoine Pitrou wrote:

On Fri, 10 Jan 2014 16:23:53 -0800 Ethan Furman <ethan at stoneleaf.us> wrote:

On 01/08/2014 02:42 PM, Antoine Pitrou wrote:

With Victor's consent, I overhauled PEP 460 and made the feature set more restricted and consistent with the bytes/str separation. From the PEP: ============= Python 3 generally mandates that text be stored and manipulated as unicode (i.e. str objects, not bytes). In some cases, though, it makes sense to manipulate bytes objects directly. Typical usage is binary network protocols, where you can want to interpolate and assemble several bytes object (some of them literals, some of them compute) to produce complete protocol messages. For example, protocols such as HTTP or SIP have headers with ASCII names and opaque "textual" values using a varying and/or sometimes ill-defined encoding. Moreover, those headers can be followed by a binary body... which can be chunked and decorated with ASCII headers and trailers! As it stands now, the PEP talks about ASCII, about how it makes sense sometimes to work directly with bytes objects, and then refuses to allow % to embed ASCII text in the byte stream. Indeed I refuse for %-formatting to allow the mixing of bytes and str objects, in the same way that it is forbidden to concatenate "a" and b"b" together, or to write b"".join(["abc"]).

I think: 'a' + b'b' is different from: b'Content-Length: %d' % 42

The former we want to prevent, but I see nothing wrong with the latter.

So, I'm -1 on the PEP. It doesn't address the cases laid out in issue 3892. See for example http://bugs.python.org/issue3982#msg180432 .

Eric.

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