def main(self, config_filename, regex):
self._read_configuration_file(config_filename)<EOL>if self._constants_filename:<EOL><INDENT>self._io.title('<STR_LIT>')<EOL>self.connect()<EOL>self._get_old_columns()<EOL>self._get_columns()<EOL>self._enhance_columns()<EOL>self._merge_columns()<EOL>self._write_columns()<EOL>self._get_labels(regex)<EOL>self._fill_constants()<EOL>self.__write_constant_class()<EOL>self.disconnect()<EOL>self.__log_number_of_constants()<EOL><DEDENT>else:<EOL><INDENT>self._io.log_verbose('<STR_LIT>')<EOL><DEDENT>return <NUM_LIT:0><EOL>
:param str config_filename: The config filename.
:param str regex: The regular expression for columns which we want to use.

:rtype: int