Is it possible to test for a previously created folder on the hard drive I'd like to create a folder on the hard-drive for the first time the selected model is exported.

After this, the script will fail, because the folder being created by os.mkdir already exists:

directoryPath = "//_MODEL_FOLDERS_/"
path = bpy.path.abspath(directoryPath)

# fails if dir exists
os.mkdir(path + obj.name)


It should be tested.

So does anyone know of a way to test if a folder already exists before trying to create it?
I would suggest to use os.path.join() instead of +.

To test you can use os.path.exists(os.path.join(path, obj.name))