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The C and C++ Include Header Files

cat -n /usr/include/python3.14/cpython/listobject.h

     1	#ifndef Py_CPYTHON_LISTOBJECT_H
     2	#  error "this header file must not be included directly"
     3	#endif
     4	
     5	typedef struct {
     6	    PyObject_VAR_HEAD
     7	    /* Vector of pointers to list elements.  list[0] is ob_item[0], etc. */
     8	    PyObject **ob_item;
     9	
    10	    /* ob_item contains space for 'allocated' elements.  The number
    11	     * currently in use is ob_size.
    12	     * Invariants:
    13	     *     0 <= ob_size <= allocated
    14	     *     len(list) == ob_size
    15	     *     ob_item == NULL implies ob_size == allocated == 0
    16	     * list.sort() temporarily sets allocated to -1 to detect mutations.
    17	     *
    18	     * Items must normally not be NULL, except during construction when
    19	     * the list is not yet visible outside the function that builds it.
    20	     */
    21	    Py_ssize_t allocated;
    22	} PyListObject;
    23	
    24	/* Cast argument to PyListObject* type. */
    25	#define _PyList_CAST(op) \
    26	    (assert(PyList_Check(op)), _Py_CAST(PyListObject*, (op)))
    27	
    28	// Macros and static inline functions, trading safety for speed
    29	
    30	static inline Py_ssize_t PyList_GET_SIZE(PyObject *op) {
    31	    PyListObject *list = _PyList_CAST(op);
    32	#ifdef Py_GIL_DISABLED
    33	    return _Py_atomic_load_ssize_relaxed(&(_PyVarObject_CAST(list)->ob_size));
    34	#else
    35	    return Py_SIZE(list);
    36	#endif
    37	}
    38	#define PyList_GET_SIZE(op) PyList_GET_SIZE(_PyObject_CAST(op))
    39	
    40	#define PyList_GET_ITEM(op, index) (_PyList_CAST(op)->ob_item[(index)])
    41	
    42	static inline void
    43	PyList_SET_ITEM(PyObject *op, Py_ssize_t index, PyObject *value) {
    44	    PyListObject *list = _PyList_CAST(op);
    45	    assert(0 <= index);
    46	    assert(index < list->allocated);
    47	    list->ob_item[index] = value;
    48	}
    49	#define PyList_SET_ITEM(op, index, value) \
    50	    PyList_SET_ITEM(_PyObject_CAST(op), (index), _PyObject_CAST(value))
    51	
    52	PyAPI_FUNC(int) PyList_Extend(PyObject *self, PyObject *iterable);
    53	PyAPI_FUNC(int) PyList_Clear(PyObject *self);