Can't download file using files_download_to_file

This is the Python SDK, correct?

calling print(dbx.files_list_folder("")) will show the full ListFolderResult object. 

To iterate over the results and print just the path, you'll want something like this:

res = dbx.files_list_folder("")
    for entry in res.entries:
        print(entry.path_lower)

That will return valid paths that you can use with the files_download_to_file call.