NoneType is basically deprecated but None behaves differently

[justinvanwinkle]

Bug report

Bug description:

python 3.13

# Add a code block here, if required

>>> from types import NoneType
>>> None | int
None | int

>>> int | None
int | None

>>> None | int == int | None
True

>>> NoneType | int == None | int
True

>>> NoneType | NoneType
<class 'NoneType'>

>>> NoneType | NoneType == NoneType
True

>>> from typing import Union

>>> Union[None, None]
<class 'NoneType'>

>>> NoneType | None
<class 'NoneType'>

>>> None | NoneType
<class 'NoneType'>

>>> Union[None, NoneType]
<class 'NoneType'>

>>> None | None
Traceback (most recent call last):
  File "<python-input-50>", line 1, in <module>
    None | None
    ~~~~~^~~~~~
TypeError: unsupported operand type(s) for |: 'NoneType' and 'NoneType'

CPython versions tested on:

3.13

Operating systems tested on:

Linux

[picnixz]

NoneType is basically deprecated

That's not true. NoneType is not deprecated, as it can be used in some places (we even exposed it in 3.10!) where one needs type expressions.

As for why None | None does not work, this is the expected behaviour. We're not in a type context so we're using the | for instances, not for classes. Also, changing this would be a breaking change if, for instance, one tries x | y and both are None. We would like that to raise but not to silently convert it to None.

The TYPE | None and None | TYPE working is mostly synctactic sugar I think.

cc @JelleZijlstra for more details / confirmation.

[JelleZijlstra]

It's unfortunate that None | None doesn't work (it's sometimes useful if it did work in a typing context) but not really avoidable.

[picnixz]

I guess it's to be closed as wont fix? I'm not sure we want to make None | None == NoneType at runtime right?