def __init__(self, f, symbols, file_unit=angstrom):
if isinstance(f, str):<EOL><INDENT>self._auto_close = True<EOL>self._f = open(f, '<STR_LIT:w>')<EOL><DEDENT>else:<EOL><INDENT>self._auto_close = False<EOL>self._f = f<EOL><DEDENT>self.symbols = symbols<EOL>self.file_unit = file_unit<EOL>
Arguments:
 | ``f``  -- a filename or a file-like object to write to
 | ``symbols``  --  the atom symbols

Optional argument
 | ``file_unit``  --  the unit of the values written to file
                      [default=angstrom]