There's a new version of the mergeall folder tree synchronization tool, which uses Python 3.5's os.scandir(), if available, to radically speed up its trees comparison phase. In testing on Windows 7 and 10, the new call speeds mergeall comparisons by a factor of 5 to 10, depending on devices. This is due entirely to the elimination of system calls that os.scandir() affords.
The savings is especially significant for large archives. For a 78G target use case of 50k files in 3k folders, comparison runtime fell from 40 to 7 seconds on a fast USB stick (6x); from 112 to 16 seconds on a slower stick (7x); and from 600 to 60 seconds on an ancient single-core machine (10x).
Also note that the scandir() call is standard in the os module in 3.5, but can also be had for older Python releases, including 2.7 and older 3.X, via a PyPI package. mergeall uses either form if present, and falls back on the original os.listdir() scheme as a last resort to continue supporting older Pythons (though a scandir() is now strongly recommended, for obvious reasons!).
All of which seems proof that language improvement and backward compatibility are not necessarily mutually exclusive. The details:
Main README: http://learning-python.com/mergeall/Readme.html
Download the package: http://learning-python.com/downloads/mergeall.zip