第四章 Python中的List对象

列表对象的定义：
typedef struct {
    PyObject_VAR_HEAD
    /* Vector of pointers to list elements.  list[0] is ob_item[0], etc. */
    PyObject **ob_item;

    /* ob_item contains space for 'allocated' elements.  The number
     * currently in use is ob_size.
     * Invariants:
     *     0 <= ob_size <= allocated
     *     len(list) == ob_size
     *     ob_item == NULL implies ob_size == allocated == 0
     * list.sort() temporarily sets allocated to -1 to detect mutations.
     *
     * Items must normally not be NULL, except during construction when
     * the list is not yet visible outside the function that builds it.
     */
    Py_ssize_t allocated;
} PyListObject;



通过PyList_New(size)来创建PyListObject

有一个free_list来缓存申请的PyListObject
当调用list_dealloc销毁PyListObject时，把对象的元素清空。同时放到free_list中。
即free_list不像整数类型的free_list会在python初始化时就申请空间，而只是回收已申请的空间