__init__.py 文件源码

def register_namespace_handler(importer_type, namespace_handler):
    """Register `namespace_handler` to declare namespace packages

    `importer_type` is the type or class of a PEP 302 "Importer" (sys.path item
    handler), and `namespace_handler` is a callable like this::

        def namespace_handler(importer, path_entry, moduleName, module):
            # return a path_entry to use for child packages

    Namespace handlers are only called if the importer object has already
    agreed that it can handle the relevant path item, and they should only
    return a subpath if the module __path__ does not already contain an
    equivalent subpath.  For an example namespace handler, see
    ``pkg_resources.file_ns_handler``.
    """
    _namespace_handlers[importer_type] = namespace_handler