[Python-Dev] Issue 11406: adding os.scandir(), a directory iterator returning stat-like info (original) (raw)

Nick Coghlan ncoghlan at gmail.com
Sat May 11 16:34:14 CEST 2013

On Sat, May 11, 2013 at 2:24 PM, Ben Hoyt <benhoyt at gmail.com> wrote:

In all the practical examples I've seen (and written myself), I iterate over a directory and I just need to know whether it's a file or directory (or maybe a link). Occassionally you need the size as well, but that would just mean a similar check "if st.stsize is None: st = os.stat(...)", which on Linux/OS X would call stat(), but it'd still be free and fast on Windows.

Here's the full set of fields on a current stat object:

st_atime st_atime_ns st_blksize st_blocks st_ctime st_ctime_ns st_dev st_gid st_ino st_mode st_mtime st_mtime_ns st_nlink st_rdev st_size st_uid

Do we really want to publish an object with all of those as attributes potentially set to None, when the abstraction we're trying to present is intended primarily for the benefit of os.walk?

And if we're creating a custom object instead, why return a 2-tuple rather than making the entry's name an attribute of the custom object?

To me, that suggests a more reasonable API for os.scandir() might be for it to be an iterator over "dir_entry" objects:

name (as a string)
is_file()
is_dir()
is_link()
stat()
cached_stat (None or a stat object)

On all platforms, the query methods would not require a separate stat() call. On Windows, cached_stat would be populated with a full stat object when scandir builds the entry. On non-Windows platforms, cached_stat would initially be None, and you would have to call stat() to populate it.

If we find other details that we can reliably provide cross-platform from the dir information, then we can add more query methods or attributes to the dir_entry object.

Cheers, Nick.

-- Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia

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