[Python-Dev] Updates to PEP 471, the os.scandir() proposal (original) (raw)

Nick Coghlan ncoghlan at gmail.com
Sat Jul 12 17:07:03 CEST 2014

On 11 Jul 2014 12:46, "Ben Hoyt" <benhoyt at gmail.com> wrote:

[replying to python-dev this time] >> The "onerror" approach can also deal with readdir failing, which the >> PEP currently glosses over. > > > Do we want this, though? I can see an error handler for individual entries, > but if one of the *dir commands fails that would seem to be fairly > catastrophic. Very much agreed that this isn't necessary for just readdir/FindNext errors. We've never had this level of detail before -- if listdir() fails half way through (very unlikely) it just bombs with OSError and you get no entries at all. If you really really want this (again very unlikely), you can always use call next() directly and catch OSError around that call.

Agreed - I think the PEP should point this out explicitly, and show that the approach it takes offers a lot of flexibility in error handling from "just let it fail", to a single try/catch around the whole loop, to try/catch just around the operations that might call lstat(), to try/catch around the individual iteration steps.

os.walk remains the higher level API that most code should be using, and that has to retain the current listdir based behaviour (any error = ignore all entries in that directory) for backwards compatibility reasons.

Cheers, Nick.

-Ben

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