cpython/Include/cpython/listobject.h

#ifndef Py_CPYTHON_LISTOBJECT_H
#  error "this header file must not be included directly"
#endif

PyListObject;

/* Cast argument to PyListObject* type. */
#define _PyList_CAST(op) …

// Macros and static inline functions, trading safety for speed

static inline Py_ssize_t PyList_GET_SIZE(PyObject *op) { … }
#define PyList_GET_SIZE(op) …

#define PyList_GET_ITEM(op, index) …

static inline void
PyList_SET_ITEM(PyObject *op, Py_ssize_t index, PyObject *value) { … }
#define PyList_SET_ITEM(op, index, value) …

PyAPI_FUNC(int) PyList_Extend(PyObject *self, PyObject *iterable);
PyAPI_FUNC(int) PyList_Clear(PyObject *self);