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

Benjamin Peterson benjamin at python.org
Thu Sep 7 18:46:42 EDT 2017

On Thu, Sep 7, 2017, at 14:43, Guido van Rossum wrote:

On Thu, Sep 7, 2017 at 2:40 PM, Benjamin Peterson <benjamin at python.org> wrote:

> > > On Thu, Sep 7, 2017, at 14:19, Guido van Rossum wrote: > > Nice one. > > > > It would be nice to specify the various APIs needed as well. > > The compileall and pycompile ones? > Yes, and the SipHash mod to specify the key you mentioned.

Done.

> > > Why do you keep the mtime-based format as an option? (Maybe because it's > > faster? Did you measure it?) > > I haven't actually measured anything, but stating a file will definitely > be faster than reading it completely and hashing it. I suppose if the > speed difference between timestamp-based and hash-based pycs turned out > to be small we could feel good about dropping the timestamp format > completely. However, that difference might be hard to determine > definitely as I expect the speed hit will vary widely based on system > parameters such as disk speed and page cache size. > > My goal in this PEP was to preserve the current pyc invalidation > behavior, which works well today for many use cases, as the default. The > hash-based pycs are reserved for distribution and other power use cases. > OK, maybe you can clarify that a bit in the PEP.

I've added a paragraph to the Rationale section.

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