code: def blksize(path):
      
      diskfreespace = win32file.GetDiskFreeSpace
      dirname = os.path.dirname(fullpath(path))
      try:
          cluster_sectors, sector_size = diskfreespace(dirname)[:2]
          size = cluster_sectors * sector_size
  
      except win32file.error as e:
          if e.winerror != winerror.ERROR_NOT_READY:
              raise
          sleep(3)
          size = blksize(dirname)
  
      return size
docs: Get optimal file system buffer size (in bytes) for I/O calls.