def AddExts( baseFN, *exts ):
  """Return tuple of filenames obtained by adding specified extensions to the base name"""
  return tuple( [ baseFN + ( '.' if ext and not ( baseFN.endswith('.') or ext.startswith( '.' ) ) else '' ) + ext
                                           for extList in exts for ext in ( extList.strip().split() if extList.strip() else ('',) ) ] )