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

[Paul Moore]

On 9 July 2014 21:24, Victor Stinner <victor.stinner at gmail.com> wrote:
> Example where you may sometimes need is_dir(), but not always
> ---
> for entry in os.scandir(path):
>   if ignore_entry(entry.name):
>      # this entry is not interesting, lstat_result is useless here
>      continue
>   if entry.is_dir():  # fetch required data if needed
>      continue
>   ...
> ---

That is an extremely good point, and articulates why I've always been
a bit uncomfortable with the whole ensure_stat idea.

> I don't understand why you are all focused on handling os.stat() and
> os.lstat() errors. See for example the os.walk() function which is an
> old function (python 2.6!): it doesn't catch erros on isdir(), even if
> it has an onerror parameter... It only handles errors on listdir().
> IMO errors on os.stat() and os.lstat() are very rare under very
> specific conditions. The most common case is that you can get the
> status if you can list files.

Personally, I'm only focused on it as a response to others feeling
it's important. I'm on Windows, where there are no extra stat calls,
so all *I* care about is having an API that deals with the use cases
others are concerned about without making it too hard for me to use it
on Windows where I don't have to worry about all this.

If POSIX users come to a consensus that error handling doesn't need
special treatment, I'm more than happy to go back to the PEP version.
(Much as previously happened with the race condition debate).

Paul