Hi, On Wed, 01 May 2013 09:32:28 +0200 Pieter Nagel <pie...@nagel.co.za> wrote: > Hi all, > > I write as a python lover for over 13 years who's always wanted > something like PEP 428 in Python. > > I am concerned about the caching of stat() results as currently defined > in the PEP. This means that all behaviour built on top of stat(), such > as p.is_dir(), p.is_file(), p.st_size and the like can indefinitely hold > on to stale data until restat() is called, and I consider this > confusing.
I understand it might be confusing. On the other hand, if you call is_dir() then is_file() (then perhaps another metadata-reading operation), and there's a race condition where the file is modified in-between, you could have pretty much nonsensical results, if not for the caching. > Isn't the whole notion that stat() need to be cached for performance > issues somewhat of a historical relic of older OS's and filesystem > performance? AFAIK linux already has stat() caching as a side-effect of > the filesystem layer's metadata caching. How does Windows and Mac OS > fare here? Are there benchmarks proving that this is serious enough to > complicate the API? Surprisingly enough, some network filesystems have rather bad stat() performance. This has been reported for years as an issue with Python's import machinery, until 3.3 added a caching scheme where stat() calls are no more issued for each and every path directory and each and every imported module. But as written above caching is also a matter of functionality. I'll let other people chime in. > If the ability to cache stat() calls is deemed important enough, how > about a different API where is_file(), is_dir() and the like are added > as methods on the result object that stat() returns? That's a good idea too. It isn't straightforward since os.stat() is implemented in C. Regards Antoine. _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
