cpython/Include/rangeobject.h

/* Range object interface */

/*
A range object represents an integer range.  This is an immutable object;
a range cannot change its value after creation.

Range objects behave like the corresponding tuple objects except that
they are represented by a start, stop, and step datamembers.
*/

extern DL_IMPORT(PyTypeObject) PyRange_Type;

#define PyRange_Check(op) ((op)->ob_type == &PyRange_Type)

extern DL_IMPORT(PyObject *) PyRange_New(long, long, long, int);