The None Object - Python 3.5.9 documentation 编辑

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.)