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

Antoine Pitrou solipsis at pitrou.net
Thu Sep 7 17:56:59 EDT 2017

On Thu, 07 Sep 2017 14:40:33 -0700 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? > > 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.

Also, while some/many of us have fast development machines with performant SSDs, Python can be used in situations where "disk" I/O is still slow (imagine a Raspberry Pi system or similar, grinding through a SD card or USB key to load py and pyc files).

Regards

Antoine.

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