type(None).__module__ returns wrong module

[rafalkrupinski]

Bug report

Bug description:

t=type(None)
print(f'{t.__module__}.{t.__name__}')
# prints builtins.NoneType
# actual module: types

CPython versions tested on:

3.12, 3.13

Operating systems tested on:

Linux

[Eclips4]

Hello!
It's not a bug. None is defined as builtins attribute in the builtins module:

cpython/Python/bltinmodule.c

Line 3336 in c5b0c90

SETBUILTIN("None", Py_None);

[rafalkrupinski]

@Eclips4 It's tot about None, but NoneType

[Eclips4]

@Eclips4 It's tot about None, but NoneType

Oh, yes, I've misread your message. What made you think that NoneType was coming from types module?

[rafalkrupinski]

WDYM

>>> from builtins import NoneType
Traceback (most recent call last):
  File "<python-input-3>", line 1, in <module>
    from builtins import NoneType
ImportError: cannot import name 'NoneType' from 'builtins' (unknown location)

>>> from types import NoneType
>>> print(NoneType)
<class 'NoneType'>

[Eclips4]

WDYM

>>> from builtins import NoneType
Traceback (most recent call last):
  File "<python-input-3>", line 1, in <module>
    from builtins import NoneType
ImportError: cannot import name 'NoneType' from 'builtins' (unknown location)

>>> from types import NoneType
>>> print(NoneType)
<class 'NoneType'>

That's doesnt mean that NoneType is coming from types. In fact, NoneType is defined in Objects/object.c:

cpython/Objects/object.c

Lines 2119 to 2158 in d61542b

	PyTypeObject _PyNone_Type = {
	PyVarObject_HEAD_INIT(&PyType_Type, 0)
	"NoneType",
	0,
	0,
	none_dealloc, /*tp_dealloc*/
	0, /*tp_vectorcall_offset*/
	0, /*tp_getattr*/
	0, /*tp_setattr*/
	0, /*tp_as_async*/
	none_repr, /*tp_repr*/
	&none_as_number, /*tp_as_number*/
	0, /*tp_as_sequence*/
	0, /*tp_as_mapping*/
	(hashfunc)none_hash,/*tp_hash */
	0, /*tp_call */
	0, /*tp_str */
	0, /*tp_getattro */
	0, /*tp_setattro */
	0, /*tp_as_buffer */
	Py_TPFLAGS_DEFAULT, /*tp_flags */
	none_doc, /*tp_doc */
	0, /*tp_traverse */
	0, /*tp_clear */
	_Py_BaseObject_RichCompare, /*tp_richcompare */
	0, /*tp_weaklistoffset */
	0, /*tp_iter */
	0, /*tp_iternext */
	0, /*tp_methods */
	0, /*tp_members */
	0, /*tp_getset */
	0, /*tp_base */
	0, /*tp_dict */
	0, /*tp_descr_get */
	0, /*tp_descr_set */
	0, /*tp_dictoffset */
	0, /*tp_init */
	0, /*tp_alloc */
	none_new, /*tp_new */
	};

Why do you see builtins in the __module__ of a NoneType? Well, because NoneType is a special object and doesn't actually have a module, so interpreter is doing some hacky stuff:

cpython/Objects/typeobject.c

Line 1418 in d61542b

mod = &_Py_ID(builtins);

This is a long-standing behavior and I don't think we should change it.

[rafalkrupinski]

NoneType was introduced in 3.10, so not that long, and #63637 says it was in types. How about adding an alias for compatibility?

[Eclips4]

NoneType was introduced in 3.10, so not that long, and #63637 says it was in types. How about adding an alias for compatibility?

NoneType as type of None wasn't introduced in 3.10, it was introduced much earlier. I don't understand what alias could be added here.

[rafalkrupinski]

@Eclips4 I'm getting a feeling you're being dismissive towards me.

Why do you see builtins in the module of a NoneType? Well, because NoneType is a special object and doesn't actually have a module, so interpreter is doing some hacky stuff:

I don't have a problem with builtins in __module__, only with NoneType missing from builtins. it's just not there, from python perspective. importing NoneType from builtins raises ImportError!

[Eclips4]

@Eclips4 I'm getting a feeling you're being dismissive towards me.

Sorry, I just didn't understand you previously. I didn't mean to be dismissive or offend you.

I now understand your confusion and summarize our conversation for others:
type(None).__module__ returns "builtins" and in fact if we would try to import type(None).__name__ from "builtins" it would fail with ImportError. As possible solution we could change it module to types where in fact we have a NoneType.
The same applies for type(some_function), type(some_lambda) and many others.