__init__.py 文件源码

def activate():
    """Install the path-based import components."""
    # We should plug filefinder first to avoid plugging ROSDirectoryFinder, when it is not a ROS thing...

    filefinder2.activate()

    if ros_path_hook not in sys.path_hooks:
        # We need to be before FileFinder to be able to find our '.msg' and '.srv' files without making a namespace package
        # Note this must be early in the path_hook list, since we change the logic
        # and a namespace package becomes a ros importable package.
        sys.path_hooks.insert(filefinder2.get_filefinder_index_in_path_hooks(), ros_path_hook)

    if ROSPathFinder not in sys.meta_path:
        # adding metahook, before the usual pathfinder, to avoid interferences with python namespace mechanism...
        sys.meta_path.insert(filefinder2.get_pathfinder_index_in_meta_hooks(), ROSPathFinder)

    # Resetting sys.path_importer_cache
    # to support the case where we have an implicit (msg/srv) package inside an already loaded package,
    # since we need to replace the default importer.
    sys.path_importer_cache.clear()