python __slots__ 使你的代码更加节省内存

cf2000

/* PyDict_MINSIZE is the minimum size of a dictionary.  This many slots are　　
* allocated directly in the dict object (in the ma_smalltable member).
　　
* It must be a power of 2, and at least 4.  8 allows dicts with no more
　　
* than 5 active entries to live in ma_smalltable (and so avoid an
　　
* additional malloc); instrumentation suggested this suffices for the
　　
* majority of dicts (consisting mostly of usually-small instance dicts and
　　
* usually-small dicts created to pass keyword arguments).
　　
*/
　　
#define PyDict_MINSIZE 8
　　

　　
typedef struct {
　　
    /* Cached hash code of me_key.  Note that hash codes are C longs.
　　
     * We have to use Py_ssize_t instead because dict_popitem() abuses
　　
     * me_hash to hold a search finger.
　　
     */
　　
    Py_ssize_t me_hash;
　　
    PyObject *me_key;
　　
    PyObject *me_value;
　　
} PyDictEntry;
　　

　　
/*
　　
To ensure the lookup algorithm terminates, there must be at least one Unused
　　
slot (NULL key) in the table.
　　
The value ma_fill is the number of non-NULL keys (sum of Active and Dummy);
　　
ma_used is the number of non-NULL, non-dummy keys (== the number of non-NULL
　　
values == the number of Active items).
　　
To avoid slowing down lookups on a near-full table, we resize the table when
　　
it's two-thirds full.
　　
*/
　　
typedef struct _dictobject PyDictObject;
　　
struct _dictobject {
　　
    PyObject_HEAD
　　
    Py_ssize_t ma_fill;  /* # Active + # Dummy */
　　
    Py_ssize_t ma_used;  /* # Active */
　　

　　
    /* The table contains ma_mask + 1 slots, and that's a power of 2.
　　
     * We store the mask instead of the size because the mask is more
　　
     * frequently needed.
　　
     */
　　
    Py_ssize_t ma_mask;
　　

　　
    /* ma_table points to ma_smalltable for small tables, else to
　　
     * additional malloc'ed memory.  ma_table is never NULL!  This rule
　　
     * saves repeated runtime null-tests in the workhorse getitem and
　　
     * setitem calls.
　　
     */
　　
    PyDictEntry *ma_table;
　　
    PyDictEntry *(*ma_lookup)(PyDictObject *mp, PyObject *key, long hash);
　　
    PyDictEntry ma_smalltable[PyDict_MINSIZE];
　　
};