1 static PyDictEntry *
 2 lookdict(PyDictObject *mp, PyObject *key, register long hash)
 3 {
 4     register size_t i;
 5     register size_t perturb;
 6     register PyDictEntry *freeslot;
 7     register size_t mask = (size_t)mp->ma_mask;
 8     PyDictEntry *ep0 = mp->ma_table;
 9     register PyDictEntry *ep;
10     register int cmp;
11     PyObject *startkey;
12
13     i = (size_t)hash & mask;
14     ep = &ep0[i];
15     if (ep->me_key == NULL || ep->me_key == key) //【1】
16         return ep;
17
18     if (ep->me_key == dummy)
19         freeslot = ep;
20     else {
21 //进到这里说明 ep->me-key !=NULL && ep->me_key!=key && ep->me_key==Active
22         if (ep->me_hash == hash) {
23             startkey = ep->me_key;
24             Py_INCREF(startkey);
25             cmp = PyObject_RichCompareBool(startkey, key, Py_EQ); //[2]这里为啥要再比较一次？
26             Py_DECREF(startkey);
27             if (cmp < 0)
28                 return NULL;
29             if (ep0 == mp->ma_table && ep->me_key == startkey) {//[3]这里明显是相等的，为啥要再判断一次？
30                 if (cmp > 0)
31                     return ep;
32             }
33             else {
34                 /* The compare did major nasty stuff to the
35                  * dict:  start over.
36                  * XXX A clever adversary could prevent this
37                  * XXX from terminating.
38                  */
39                 return lookdict(mp, key, hash);
40             }
41         }
42         freeslot = NULL;
43     }