@property<EOL><INDENT>def n_file(self):<DEDENT>
self.assert_is_dir_and_exists()<EOL>n = <NUM_LIT:0><EOL>for _ in self.select_file(recursive=True):<EOL><INDENT>n += <NUM_LIT:1><EOL><DEDENT>return n<EOL>
Count how many files in this directory. Including file in sub folder.