Yes that looks like an improvement, though I wonder what’s wrong with your original proposal (performance maybe?). In any case, it definitely needs a comment explaining the first isdir() avoids competing failures that mask EEXIST, and the exception handling avoids the race to create the directory.

A test case for the test suite would also be good. I understand it should be easy to do for Windows, just make a directory with an absolute path including a drive root like d:\.