Function lazy_import

python/pyfory/utils.py:25–66

(
    name: str,
    package: str = None,
    globals_: Dict = None,  # pylint: disable=redefined-builtin
    locals_: Dict = None,  # pylint: disable=redefined-builtin
    rename: str = None,
    placeholder: bool = False,
)

# This method is derived from https://github.com/mars-project/mars/blob/c36c53fa22e10ef9477d9c454401a2f281375f31/mars/utils.py.
def lazy_import(
    name: str,
    package: str = None,
    globals_: Dict = None,  # pylint: disable=redefined-builtin
    locals_: Dict = None,  # pylint: disable=redefined-builtin
    rename: str = None,
    placeholder: bool = False,
):
    rename = rename or name
    prefix_name = name.split(".", 1)[0]
    globals_ = globals_ or inspect.currentframe().f_back.f_globals

    class LazyModule(object):
        def __init__(self):
            self._on_loads = []

        def __getattr__(self, item):
            if item.startswith("_pytest") or item in ("__bases__", "__test__"):
                raise AttributeError(item)

            real_mod = importlib.import_module(name, package=package)
            if rename in globals_:
                globals_[rename] = real_mod
            elif locals_ is not None:
                locals_[rename] = real_mod
            ret = getattr(real_mod, item)
            for on_load_func in self._on_loads:
                on_load_func()
            # make sure on_load hooks only executed once
            self._on_loads = []
            return ret

        def add_load_handler(self, func: Callable):
            self._on_loads.append(func)
            return func

    if importlib.util.find_spec(prefix_name) is not None:
        return LazyModule()
    elif placeholder:
        return ModulePlaceholder(prefix_name)
    else:
        return None


class ModulePlaceholder: