One issue with your code - what would you expect str(test) to produce? "dir/test.txt" or "dir\test.txt"? That's the point of the "flavour" - is it a Windows path or a Unix path?

Agreed that an easier method of creating Path subclasses that handle this type of thing would be useful, but any solution needs to make sure that developers don't overlook the Windows vs Unix implications.

Can you give an actual use case (as opposed to the toy example)?