[Python-Dev] PEP 428: Pathlib -> stat caching (original) (raw)

Antoine Pitrou solipsis at pitrou.net
Mon Sep 16 22:05:46 CEST 2013

On Mon, 16 Sep 2013 15:48:54 -0400 Brett Cannon <brett at python.org> wrote:

> > So I would like to propose the following API change: > > - Path.stat() (and stat-accessing methods such as getmtime()...) > returns an uncached stat object by default > > - Path.cachestat() can be called to return the stat() and cache it > for future use, such that any future call to stat(), cachestat() or > a stat-accessing function reuses that cached stat > > In other words, only if you use cachestat() at least once is the > stat() value cached and reused by the Path object. > (also, it's a per-Path decision) >

Any reason why stat() can't get a keyword-only cached=True argument instead? Or have stat() never cache() but statcache() always so that people can choose if they want fresh or cached based on API and not whether some library happened to make a decision for them?

  1. Because you also want the helper functions (get_mtime(), etc.) to cache the value too. It's not only about stat().

  2. Because of the reverse use case where you want a library to reuse a cached value despite the library not using an explicit caching call.

Basically, the rationale is:

  1. Caching should be opt-in, which is what this new API achieves.

  2. Once you have asked for caching, most always you also want the subsequent accesses to be cached.

I realize there should be a third method clear_cache(), though ;-)

Regards

Antoine.

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