[Python-Dev] PEP 552: deterministic pycs (original) (raw)

Benjamin Peterson benjamin at python.org
Fri Sep 8 13:52:03 EDT 2017

Thank you all for the feedback. I've now updated the PEP to specify a 4-word pyc header with a bit field in every case.

On Fri, Sep 8, 2017, at 09:43, Nick Coghlan wrote:

On 8 September 2017 at 07:55, Antoine Pitrou <solipsis at pitrou.net> wrote: > On Fri, 8 Sep 2017 07:49:46 -0700 > Nick Coghlan <ncoghlan at gmail.com> wrote: >> > I'd rather a single magic number and a separate bitfield that tells >> > what the header encodes exactly. We don't have to fight for a tiny >> > size reduction of pyc files. >> >> One of Benjamin's goals was for the existing timestamp-based pyc >> format to remain completely unchanged, so we need some kind of marker >> in the magic number to indicate whether the file is using the new >> format or nor. > > I don't think that's a useful goal, as long as we bump the magic number.

Yeah, we (me, Benjamin, Greg) discussed that here, and we agree - there isn't actually any benefit to keeping the timestamp based pyc's using the same layout, since the magic number is already going to change anyway. Given that, I think your suggested 16 byte header layout would be a good one: 4 byte magic number, 4 bytes reserved for format flags, 8 bytes with an interpretation that depends on the format flags. Cheers, Nick. -- Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia

Python-Dev mailing list Python-Dev at python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/benjamin%40python.org

More information about the Python-Dev mailing list