We can get a greater speed up for walkdir() without resorting to
caching, too. Some operating systems and file system report the file
type in the dirent struct that is returned by readdir(). This reduces
the number of stat calls to zero.
Yes, definitely. This is exactly what my os.walk() replacement, "Betterwalk", does:
On Windows you get *all* stat information from iterating the directory entries (FindFirstFile etc). And on Linux most of the time you get enough for os.walk() not to need an extra stat (though it does depend on the file system).
I still hope to clean up Betterwalk and make a C version so we can use it in the standard library. In many cases it speeds up os.walk() by several times, even an order of magnitude in some cases. I intend for it to be a drop-in replacement for os.walk(), just faster.