> I would prefer to go the other route and don't expose lstat(). It's > cleaner and less confusing to have a property cached_lstat on the object > because it actually says what it contains. The property's internal code > can do a lstat() call if necessary.
Are you suggesting just accessing .cached_lstat could call os.lstat()? That seems very bad to me. It's a property access -- it looks cheap, therefore people will expect it to be. From PEP 8 "Avoid using properties for computationally expensive operations; the attribute notation makes the caller believe that access is (relatively) cheap." Even worse is error handling -- I'd expect the expression "entry.cached_lstat" to only ever raise AttributeError, not OSError in the case it calls stat under the covers. Calling code would have to have a try/except around what looked like a simple attribute access. For these two reasons I think lstat() should definitely be a function. > Your code example doesn't handle the case of a failing lstat() call. It > can happen when the file is removed or permission of a parent directory > changes. True. My isdir/isfile/islink implementations should catch any OSError from the lstat() and return False (like os.path.isdir etc do). But then calling code still doesn't need try/excepts around the isdir() calls. This is how os.walk() is implemented -- there's no extra error handling around the isdir() call. > Why not have both? The os module exposes and leaks the platform details > on more than on occasion. A low level function can expose name + dirent > struct on POSIX and name + stat_result on Windows. Then you can build a > high level API like os.scandir() in pure Python code. I wouldn't be opposed to that, but it's a scandir() implementation detail. If there's a scandir_helper_win() and scandir_helper_posix() written in C, and the rest is written in Python, that'd be fine by me. As long as the Python part didn't slow it down much. > The function should use fstatat(2) function (os.lstat with dir_fd) when > it is available on the current platform. It's better and more secure > than lstat() with a joined path. Sure. I'm primarily a Windows dev, so not too familiar with all the fancy stat* functions. But what you're saying makes sense. -Ben _______________________________________________ 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
