The None Object — Python documentation

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Python/docs/3.8/c-api/none

The None Object

Note that the PyTypeObject for None is not directly exposed in the Python/C API. Since None is a singleton, testing for object identity (using == in C) is sufficient. There is no PyNone_Check() function for the same reason.

PyObject *Py_None
The Python None object, denoting lack of value. This object has no methods. It needs to be treated just like any other object with respect to reference counts.
Py_RETURN_NONE
Properly handle returning Py_None from within a C function (that is, increment the reference count of None and return it.)