# An importlib.util.LazyLoader test, based on example from# https://docs.python.org/3/library/importlib.html#implementing-lazy-importsimportsysimportimportlib.utildeflazy_import(name):spec=importlib.util.find_spec(name)loader=importlib.util.LazyLoader(spec.loader)spec.loader=loadermodule=importlib.util.module_from_spec(spec)sys.modules[name]=moduleloader.exec_module(module)returnmodule# Lazy-load the module...lazy_module=lazy_import(sys.argv[1])# ... and then trigger load by listing its contentsprint(dir(lazy_module))

$python3test_program.pyjson['JSONDecodeError','JSONDecoder','JSONEncoder','__all__','__author__','__builtins__','__cached__','__doc__','__file__','__loader__','__name__','__package__','__path__','__spec__','__version__','_default_decoder','_default_encoder','codecs','decoder','detect_encoding','dump','dumps','encoder','load','loads','scanner']

$python3test_program.pytyping['ABCMeta','AbstractSet','Annotated','Any','AnyStr','AsyncGenerator','AsyncIterable','AsyncIterator','Awaitable','BinaryIO','ByteString','CT_co','Callable','ChainMap','ClassVar','Collection','Concatenate','Container','Coroutine','Counter','DefaultDict','Deque','Dict','EXCLUDED_ATTRIBUTES','Final','ForwardRef','FrozenSet','Generator','Generic','GenericAlias','Hashable','IO','ItemsView','Iterable','Iterator','KT','KeysView','List','Literal','LiteralString','Mapping','MappingView','MethodDescriptorType','MethodWrapperType','MutableMapping','MutableSequence','MutableSet','NamedTuple','NamedTupleMeta','Never','NewType','NoReturn','NotRequired','Optional','OrderedDict','ParamSpec','ParamSpecArgs','ParamSpecKwargs','Protocol','Required','Reversible','Self','Sequence','Set','Sized','SupportsAbs','SupportsBytes','SupportsComplex','SupportsFloat','SupportsIndex','SupportsInt','SupportsRound','T','TYPE_CHECKING','T_co','T_contra','Text','TextIO','Tuple','Type','TypeAlias','TypeAliasType','TypeGuard','TypeVar','TypeVarTuple','TypedDict','Union','Unpack','VT','VT_co','V_co','ValuesView','WrapperDescriptorType','_ASSERT_NEVER_REPR_MAX_LENGTH','_AnnotatedAlias','_AnyMeta','_BaseGenericAlias','_CallableGenericAlias','_CallableType','_ConcatenateGenericAlias','_DeprecatedGenericAlias','_Final','_Func','_GenericAlias','_IdentityCallable','_LiteralGenericAlias','_NamedTuple','_NotIterable','_PROTO_ALLOWLIST','_ProtocolMeta','_SPECIAL_NAMES','_Sentinel','_SpecialForm','_SpecialGenericAlias','_TYPING_INTERNALS','_TupleType','_TypedCacheSpecialForm','_TypedDict','_TypedDictMeta','_TypingEllipsis','_UnionGenericAlias','_UnpackGenericAlias','__all__','__builtins__','__cached__','__doc__','__file__','__getattr__','__loader__','__name__','__package__','__spec__','_abc_instancecheck','_abc_subclasscheck','_alias','_allow_reckless_class_checks','_allowed_types','_caches','_caller','_check_generic','_cleanups','_collect_parameters','_deduplicate','_eval_type','_flatten_literal_params','_generic_class_getitem','_generic_init_subclass','_get_protocol_attrs','_idfunc','_is_dunder','_is_param_expr','_is_typevar_like','_is_unpacked_typevartuple','_lazy_load_getattr_static','_make_nmtuple','_make_union','_namedtuple_mro_entries','_no_init_or_replace_init','_overload_dummy','_overload_registry','_paramspec_prepare_subst','_paramspec_subst','_prohibited','_proto_hook','_remove_dups_flatten','_sentinel','_should_unflatten_callable_args','_special','_strip_annotations','_tp_cache','_type_check','_type_check_issubclass_arg_1','_type_convert','_type_repr','_typevar_subst','_typevartuple_prepare_subst','_unpack_args','_value_and_type_iter','abstractmethod','assert_never','assert_type','cast','clear_overloads','collections','copyreg','dataclass_transform','defaultdict','final','functools','get_args','get_origin','get_overloads','get_protocol_members','get_type_hints','is_protocol','is_typeddict','no_type_check','no_type_check_decorator','operator','overload','override','reveal_type','runtime_checkable','sys','types']

$ python3 test_program.py jsonTraceback (most recent call last):  File"/home/rok/tmp/pyi-py313/test_program.py", line21, in<module>print(dir(lazy_module))~~~^^^^^^^^^^^^^  File"<frozen importlib.util>", line209, in__getattribute__  File"<frozen importlib._bootstrap_external>", line1015, inexec_module  File"<frozen importlib._bootstrap>", line488, in_call_with_frames_removed  File"/home/rok/python3.13-bin/lib/python3.13/json/__init__.py", line106, in<module>from .decoderimport JSONDecoder, JSONDecodeError  File"/home/rok/python3.13-bin/lib/python3.13/json/decoder.py", line5, in<module>from jsonimport scanner  File"<frozen importlib.util>", line209, in__getattribute__  File"/home/rok/python3.13-bin/lib/python3.13/json/__init__.py", line106, in<module>from .decoderimport JSONDecoder, JSONDecodeErrorImportError:cannot import name 'JSONDecoder' from partially initialized module 'json.decoder' (most likely due to a circular import) (/home/rok/python3.13-bin/lib/python3.13/json/decoder.py)

$ python3 test_program.py typingTraceback (most recent call last):  File"/home/rok/tmp/pyi-py313/test_program.py", line21, in<module>print(dir(lazy_module))~~~^^^^^^^^^^^^^  File"<frozen importlib.util>", line209, in__getattribute__  File"<frozen importlib._bootstrap_external>", line1015, inexec_module  File"<frozen importlib._bootstrap>", line488, in_call_with_frames_removed  File"/home/rok/python3.13-bin/lib/python3.13/typing.py", line1961, in<module>classProtocol(Generic,metaclass=_ProtocolMeta):...<49 lines>...cls.__init__= _no_init_or_replace_init  File"/home/rok/python3.13-bin/lib/python3.13/typing.py", line1870, in__new__returnsuper().__new__(mcls, name, bases, namespace,**kwargs)~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^  File"<frozen abc>", line106, in__new__  File"<frozen importlib.util>", line209, in__getattribute__  File"<frozen importlib._bootstrap_external>", line1015, inexec_module  File"<frozen importlib._bootstrap>", line488, in_call_with_frames_removed  File"/home/rok/python3.13-bin/lib/python3.13/typing.py", line1961, in<module>classProtocol(Generic,metaclass=_ProtocolMeta):...<49 lines>...cls.__init__= _no_init_or_replace_init  File"/home/rok/python3.13-bin/lib/python3.13/typing.py", line1870, in__new__returnsuper().__new__(mcls, name, bases, namespace,**kwargs)~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^[...]  File"/home/rok/python3.13-bin/lib/python3.13/typing.py", line1870, in__new__returnsuper().__new__(mcls, name, bases, namespace,**kwargs)~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^  File"<frozen abc>", line106, in__new__  File"<frozen importlib.util>", line209, in__getattribute__  File"<frozen importlib._bootstrap_external>", line1015, inexec_module  File"<frozen importlib._bootstrap>", line488, in_call_with_frames_removed  File"/home/rok/python3.13-bin/lib/python3.13/typing.py", line1961, in<module>classProtocol(Generic,metaclass=_ProtocolMeta):...<49 lines>...cls.__init__= _no_init_or_replace_init  File"/home/rok/python3.13-bin/lib/python3.13/typing.py", line1870, in__new__returnsuper().__new__(mcls, name, bases, namespace,**kwargs)~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^  File"<frozen abc>", line106, in__new__  File"<frozen importlib.util>", line209, in__getattribute__  File"<frozen importlib._bootstrap_external>", line1015, inexec_module  File"<frozen importlib._bootstrap>", line488, in_call_with_frames_removed  File"/home/rok/python3.13-bin/lib/python3.13/typing.py", line1961, in<module>classProtocol(Generic,metaclass=_ProtocolMeta):...<49 lines>...cls.__init__= _no_init_or_replace_init  File"/home/rok/python3.13-bin/lib/python3.13/typing.py", line1870, in__new__returnsuper().__new__(mcls, name, bases, namespace,**kwargs)~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^  File"<frozen abc>", line106, in__new__  File"<frozen importlib.util>", line209, in__getattribute__  File"<frozen importlib._bootstrap_external>", line1011, inexec_module  File"<frozen importlib._bootstrap_external>", line1089, inget_codeRecursionError:maximum recursion depth exceeded