importutils.py 文件源码

def __enter__(self):
        # suppress writing of .pyc files:
        self.prev_dont_write_bytecode = sys.dont_write_bytecode
        sys.dont_write_bytecode = True

        if self.cleanup_import_caches:
            # remember which modules were already loaded before we run the import.
            self._backup_dict(sys.modules, 'modules', run_with_empty = False)
            self._backup_dict(sys.path_importer_cache, 'path_importer_cache', run_with_empty = True)