Python源码：字典

Posted 2021-03-23 python运维自动化之路

一、创建增加修改

1、实现代码

#创建
stu_info = { "xiedi":28, "liuhailin":27,"daiqiao":30,"hanwenhai":25,"chenqun":38}
print(stu_info)
#增加
stu_info["luoahong"]=32
print(stu_info)
#修改
stu_info["xiedi"]=29
print(stu_info)

输出结果

{‘xiedi‘: 28, ‘liuhailin‘: 27, ‘daiqiao‘: 30, ‘hanwenhai‘: 25, ‘chenqun‘: 38}
{‘xiedi‘: 28, ‘liuhailin‘: 27, ‘daiqiao‘: 30, ‘hanwenhai‘: 25, ‘chenqun‘: 38, ‘luoahong‘: 32}
{‘xiedi‘: 29, ‘liuhailin‘: 27, ‘daiqiao‘: 30, ‘hanwenhai‘: 25, ‘chenqun‘: 38, ‘luoahong‘: 32}

二、删除（del）

1、实现代码

del stu_info["chenqun"]
print(stu_info)

2、输出结果

{‘xiedi‘: 29, ‘liuhailin‘: 27, ‘daiqiao‘: 30, ‘hanwenhai‘: 25, ‘luoahong‘: 32}

 1、Dict_DelItem 

int
PyDict_DelItem(PyObject *op, PyObject *key)
{
    Py_hash_t hash;
    assert(key);
    if (!PyUnicode_CheckExact(key) ||
        (hash = ((PyASCIIObject *) key)->hash) == -1) {
        hash = PyObject_Hash(key);
        if (hash == -1)
            return -1;
    }

    return _PyDict_DelItem_KnownHash(op, key, hash);
}

2、Dict_DelItem_KnownHash

int
_PyDict_DelItem_KnownHash(PyObject *op, PyObject *key, Py_hash_t hash)
{
    Py_ssize_t ix;
    PyDictObject *mp;
    PyObject *old_value;

    if (!PyDict_Check(op)) {
        PyErr_BadInternalCall();
        return -1;
    }
    assert(key);
    assert(hash != -1);
    mp = (PyDictObject *)op;
    ix = (mp->ma_keys->dk_lookup)(mp, key, hash, &old_value);
    if (ix == DKIX_ERROR)
        return -1;
    if (ix == DKIX_EMPTY || old_value == NULL) {
        _PyErr_SetKeyError(key);
        return -1;
    }

    // Split table doesn‘t allow deletion.  Combine it.
    if (_PyDict_HasSplitTable(mp)) {
        if (dictresize(mp, DK_SIZE(mp->ma_keys))) {
            return -1;
        }
        ix = (mp->ma_keys->dk_lookup)(mp, key, hash, &old_value);
        assert(ix >= 0);
    }

    return delitem_common(mp, hash, ix, old_value);
}

/* This function promises that the predicate -> deletion sequence is atomic
 * (i.e. protected by the GIL), assuming the predicate itself doesn‘t
 * release the GIL.
 */

3、PyDict_DelItemIf

int
_PyDict_DelItemIf(PyObject *op, PyObject *key,
                  int (*predicate)(PyObject *value))
{
    Py_ssize_t hashpos, ix;
    PyDictObject *mp;
    Py_hash_t hash;
    PyObject *old_value;
    int res;

    if (!PyDict_Check(op)) {
        PyErr_BadInternalCall();
        return -1;
    }
    assert(key);
    hash = PyObject_Hash(key);
    if (hash == -1)
        return -1;
    mp = (PyDictObject *)op;
    ix = (mp->ma_keys->dk_lookup)(mp, key, hash, &old_value);
    if (ix == DKIX_ERROR)
        return -1;
    if (ix == DKIX_EMPTY || old_value == NULL) {
        _PyErr_SetKeyError(key);
        return -1;
    }

    // Split table doesn‘t allow deletion.  Combine it.
    if (_PyDict_HasSplitTable(mp)) {
        if (dictresize(mp, DK_SIZE(mp->ma_keys))) {
            return -1;
        }
        ix = (mp->ma_keys->dk_lookup)(mp, key, hash, &old_value);
        assert(ix >= 0);
    }

    res = predicate(old_value);
    if (res == -1)
        return -1;

    hashpos = lookdict_index(mp->ma_keys, hash, ix);
    assert(hashpos >= 0);

    if (res > 0)
        return delitem_common(mp, hashpos, ix, old_value);
    else
        return 0;
}

二、删除pop(k)

实现

stu_info = { "xiedi":28, "liuhailin":27,"daiqiao":30,"hanwenhai":25,"chenqun":38}
print(stu_info)
stu_info.pop("liuhailin")
print(stu_info)

输出结果：

{‘xiedi‘: 28, ‘liuhailin‘: 27, ‘daiqiao‘: 30, ‘hanwenhai‘: 25, ‘chenqun‘: 38}
{‘xiedi‘: 28, ‘daiqiao‘: 30, ‘hanwenhai‘: 25, ‘chenqun‘: 38}

1、_PyDict_Pop

PyObject *
_PyDict_Pop(PyObject *dict, PyObject *key, PyObject *deflt)
{
    Py_hash_t hash;

    if (((PyDictObject *)dict)->ma_used == 0) {
        if (deflt) {
            Py_INCREF(deflt);
            return deflt;
        }
        _PyErr_SetKeyError(key);
        return NULL;
    }
    if (!PyUnicode_CheckExact(key) ||
        (hash = ((PyASCIIObject *) key)->hash) == -1) {
        hash = PyObject_Hash(key);
        if (hash == -1)
            return NULL;
    }
    return _PyDict_Pop_KnownHash(dict, key, hash, deflt);
}

2、_PyDict_Pop_KnownHash

/* Internal version of dict.pop(). */
PyObject *
_PyDict_Pop_KnownHash(PyObject *dict, PyObject *key, Py_hash_t hash, PyObject *deflt)
{
    Py_ssize_t ix, hashpos;
    PyObject *old_value, *old_key;
    PyDictKeyEntry *ep;
    PyDictObject *mp;

    assert(PyDict_Check(dict));
    mp = (PyDictObject *)dict;

    if (mp->ma_used == 0) {
        if (deflt) {
            Py_INCREF(deflt);
            return deflt;
        }
        _PyErr_SetKeyError(key);
        return NULL;
    }
    ix = (mp->ma_keys->dk_lookup)(mp, key, hash, &old_value);
    if (ix == DKIX_ERROR)
        return NULL;
    if (ix == DKIX_EMPTY || old_value == NULL) {
        if (deflt) {
            Py_INCREF(deflt);
            return deflt;
        }
        _PyErr_SetKeyError(key);
        return NULL;
    }

    // Split table doesn‘t allow deletion.  Combine it.
    if (_PyDict_HasSplitTable(mp)) {
        if (dictresize(mp, DK_SIZE(mp->ma_keys))) {
            return NULL;
        }
        ix = (mp->ma_keys->dk_lookup)(mp, key, hash, &old_value);
        assert(ix >= 0);
    }

    hashpos = lookdict_index(mp->ma_keys, hash, ix);
    assert(hashpos >= 0);
    assert(old_value != NULL);
    mp->ma_used--;
    mp->ma_version_tag = DICT_NEXT_VERSION();
    dictkeys_set_index(mp->ma_keys, hashpos, DKIX_DUMMY);
    ep = &DK_ENTRIES(mp->ma_keys)[ix];
    ENSURE_ALLOWS_DELETIONS(mp);
    old_key = ep->me_key;
    ep->me_key = NULL;
    ep->me_value = NULL;
    Py_DECREF(old_key);

    ASSERT_CONSISTENT(mp);
    return old_value;
}

三、随机删除一个元素popitem()

stu_info = { "xiedi":28, "liuhailin":27,"daiqiao":30,"hanwenhai":25,"chenqun":38}
print(stu_info)
stu_info.popitem()
print(stu_info)

输出结果：

{‘xiedi‘: 28, ‘liuhailin‘: 27, ‘daiqiao‘: 30, ‘hanwenhai‘: 25, ‘chenqun‘: 38}
{‘xiedi‘: 28, ‘liuhailin‘: 27, ‘daiqiao‘: 30, ‘hanwenhai‘: 25}

1、dict_popitem_impl

/*[clinic input]
dict.popitem

Remove and return a (key, value) pair as a 2-tuple.

Pairs are returned in LIFO (last-in, first-out) order.
Raises KeyError if the dict is empty.
[clinic start generated code]*/

static PyObject *
dict_popitem_impl(PyDictObject *self)
/*[clinic end generated code: output=e65fcb04420d230d input=1c38a49f21f64941]*/
{
    Py_ssize_t i, j;
    PyDictKeyEntry *ep0, *ep;
    PyObject *res;

    /* Allocate the result tuple before checking the size.  Believe it
     * or not, this allocation could trigger a garbage collection which
     * could empty the dict, so if we checked the size first and that
     * happened, the result would be an infinite loop (searching for an
     * entry that no longer exists).  Note that the usual popitem()
     * idiom is "while d: k, v = d.popitem()". so needing to throw the
     * tuple away if the dict *is* empty isn‘t a significant
     * inefficiency -- possible, but unlikely in practice.
     */
    res = PyTuple_New(2);
    if (res == NULL)
        return NULL;
    if (self->ma_used == 0) {
        Py_DECREF(res);
        PyErr_SetString(PyExc_KeyError, "popitem(): dictionary is empty");
        return NULL;
    }
    /* Convert split table to combined table */
    if (self->ma_keys->dk_lookup == lookdict_split) {
        if (dictresize(self, DK_SIZE(self->ma_keys))) {
            Py_DECREF(res);
            return NULL;
        }
    }
    ENSURE_ALLOWS_DELETIONS(self);

    /* Pop last item */
    ep0 = DK_ENTRIES(self->ma_keys);
    i = self->ma_keys->dk_nentries - 1;
    while (i >= 0 && ep0[i].me_value == NULL) {
        i--;
    }
    assert(i >= 0);

    ep = &ep0[i];
    j = lookdict_index(self->ma_keys, ep->me_hash, i);
    assert(j >= 0);
    assert(dictkeys_get_index(self->ma_keys, j) == i);
    dictkeys_set_index(self->ma_keys, j, DKIX_DUMMY);

    PyTuple_SET_ITEM(res, 0, ep->me_key);
    PyTuple_SET_ITEM(res, 1, ep->me_value);
    ep->me_key = NULL;
    ep->me_value = NULL;
    /* We can‘t dk_usable++ since there is DKIX_DUMMY in indices */
    self->ma_keys->dk_nentries = i;
    self->ma_used--;
    self->ma_version_tag = DICT_NEXT_VERSION();
    ASSERT_CONSISTENT(self);
    return res;
}

四、查找（key值在字典中存在） 

1、dict_keys

static PyObject *
dict_keys(PyDictObject *mp)
{
    PyObject *v;
    Py_ssize_t i, j;
    PyDictKeyEntry *ep;
    Py_ssize_t n, offset;
    PyObject **value_ptr;

  again:
    n = mp->ma_used;
    v = PyList_New(n);
    if (v == NULL)
        return NULL;
    if (n != mp->ma_used) {
        /* Durnit.  The allocations caused the dict to resize.
         * Just start over, this shouldn‘t normally happen.
         */
        Py_DECREF(v);
        goto again;
    }
    ep = DK_ENTRIES(mp->ma_keys);
    if (mp->ma_values) {
        value_ptr = mp->ma_values;
        offset = sizeof(PyObject *);
    }
    else {
        value_ptr = &ep[0].me_value;
        offset = sizeof(PyDictKeyEntry);
    }
    for (i = 0, j = 0; j < n; i++) {
        if (*value_ptr != NULL) {
            PyObject *key = ep[i].me_key;
            Py_INCREF(key);
            PyList_SET_ITEM(v, j, key);
            j++;
        }
        value_ptr = (PyObject **)(((char *)value_ptr) + offset);
    }
    assert(j == n);
    return v;
}

2、PyDict_Keys

PyObject *
PyDict_Keys(PyObject *mp)
{
    if (mp == NULL || !PyDict_Check(mp)) {
        PyErr_BadInternalCall();
        return NULL;
    }
    return dict_keys((PyDictObject *)mp);
}

PyObject *
PyDict_Values(PyObject *mp)
{
    if (mp == NULL || !PyDict_Check(mp)) {
        PyErr_BadInternalCall();
        return NULL;
    }
    return dict_values((PyDictObject *)mp);
}

五、get(k)

1、dict_get_impl

static PyObject *
dict_get_impl(PyDictObject *self, PyObject *key, PyObject *default_value)
/*[clinic end generated code: output=bba707729dee05bf input=279ddb5790b6b107]*/
{
    PyObject *val = NULL;
    Py_hash_t hash;
    Py_ssize_t ix;

    if (!PyUnicode_CheckExact(key) ||
        (hash = ((PyASCIIObject *) key)->hash) == -1) {
        hash = PyObject_Hash(key);
        if (hash == -1)
            return NULL;
    }
    ix = (self->ma_keys->dk_lookup) (self, key, hash, &val);
    if (ix == DKIX_ERROR)
        return NULL;
    if (ix == DKIX_EMPTY || val == NULL) {
        val = default_value;
    }
    Py_INCREF(val);
    return val;
}

2、_PyDict_GetItem_KnownHash

/* Same as PyDict_GetItemWithError() but with hash supplied by caller.
   This returns NULL *with* an exception set if an exception occurred.
   It returns NULL *without* an exception set if the key wasn‘t present.
*/
PyObject *
_PyDict_GetItem_KnownHash(PyObject *op, PyObject *key, Py_hash_t hash)
{
    Py_ssize_t ix;
    PyDictObject *mp = (PyDictObject *)op;
    PyObject *value;

    if (!PyDict_Check(op)) {
        PyErr_BadInternalCall();
        return NULL;
    }

    ix = (mp->ma_keys->dk_lookup)(mp, key, hash, &value);
    if (ix < 0) {
        return NULL;
    }
    return value;
}

3、_PyDict_GetItemId

PyObject *
_PyDict_GetItemId(PyObject *dp, struct _Py_Identifier *key)
{
    PyObject *kv;
    kv = _PyUnicode_FromId(key); /* borrowed */
    if (kv == NULL) {
        PyErr_Clear();
        return NULL;
    }
    return PyDict_GetItem(dp, kv);
}

/* For backward compatibility with old dictionary interface */

4、PyDict_GetItemString

PyObject *
PyDict_GetItemString(PyObject *v, const char *key)
{
    PyObject *kv, *rv;
    kv = PyUnicode_FromString(key);
    if (kv == NULL) {
        PyErr_Clear();
        return NULL;
    }
    rv = PyDict_GetItem(v, kv);
    Py_DECREF(kv);
    return rv;
}

int
_PyDict_SetItemId(PyObject *v, struct _Py_Identifier *key, PyObject *item)
{
    PyObject *kv;
    kv = _PyUnicode_FromId(key); /* borrowed */
    if (kv == NULL)
        return -1;
    return PyDict_SetItem(v, kv, item);
}

int
PyDict_SetItemString(PyObject *v, const char *key, PyObject *item)
{
    PyObject *kv;
    int err;
    kv = PyUnicode_FromString(key);
    if (kv == NULL)
        return -1;
    PyUnicode_InternInPlace(&kv); /* XXX Should we really? */
    err = PyDict_SetItem(v, kv, item);
    Py_DECREF(kv);
    return err;
}

六、setdefault(k,v)

setdefault()表示去取字典中的key，如果取不到，则设置新值，相反如果取到，则返回原有默认值

1、dict_setdefault_impl　

/*[clinic input]
dict.setdefault
    key: object
    default: object = None
    /
Insert key with a value of default if key is not in the dictionary.
Return the value for key if key is in the dictionary, else default.
[clinic start generated code]*/

static PyObject *
dict_setdefault_impl(PyDictObject *self, PyObject *key,
                     PyObject *default_value)
/*[clinic end generated code: output=f8c1101ebf69e220 input=0f063756e815fd9d]*/
{
    PyObject *val;

    val = PyDict_SetDefault((PyObject *)self, key, default_value);
    Py_XINCREF(val);
    return val;
}

static PyObject *
dict_clear(PyDictObject *mp, PyObject *Py_UNUSED(ignored))
{
    PyDict_Clear((PyObject *)mp);
    Py_RETURN_NONE;
}

/*[clinic input]
dict.pop
    key: object
    default: object = NULL
    /

2、PyDict_SetDefault

PyObject *
PyDict_SetDefault(PyObject *d, PyObject *key, PyObject *defaultobj)
{
    PyDictObject *mp = (PyDictObject *)d;
    PyObject *value;
    Py_hash_t hash;

    if (!PyDict_Check(d)) {
        PyErr_BadInternalCall();
        return NULL;
    }

    if (!PyUnicode_CheckExact(key) ||
        (hash = ((PyASCIIObject *) key)->hash) == -1) {
        hash = PyObject_Hash(key);
        if (hash == -1)
            return NULL;
    }
    if (mp->ma_keys == Py_EMPTY_KEYS) {
        if (insert_to_emptydict(mp, key, hash, defaultobj) < 0) {
            return NULL;
        }
        return defaultobj;
    }

    if (mp->ma_values != NULL && !PyUnicode_CheckExact(key)) {
        if (insertion_resize(mp) < 0)
            return NULL;
    }

    Py_ssize_t ix = (mp->ma_keys->dk_lookup)(mp, key, hash, &value);
    if (ix == DKIX_ERROR)
        return NULL;

    if (_PyDict_HasSplitTable(mp) &&
        ((ix >= 0 && value == NULL && mp->ma_used != ix) ||
         (ix == DKIX_EMPTY && mp->ma_used != mp->ma_keys->dk_nentries))) {
        if (insertion_resize(mp) < 0) {
            return NULL;
        }
        ix = DKIX_EMPTY;
    }

    if (ix == DKIX_EMPTY) {
        PyDictKeyEntry *ep, *ep0;
        value = defaultobj;
        if (mp->ma_keys->dk_usable <= 0) {
            if (insertion_resize(mp) < 0) {
                return NULL;
            }
        }
        Py_ssize_t hashpos = find_empty_slot(mp->ma_keys, hash);
        ep0 = DK_ENTRIES(mp->ma_keys);
        ep = &ep0[mp->ma_keys->dk_nentries];
        dictkeys_set_index(mp->ma_keys, hashpos, mp->ma_keys->dk_nentries);
        Py_INCREF(key);
        Py_INCREF(value);
        MAINTAIN_TRACKING(mp, key, value);
        ep->me_key = key;
        ep->me_hash = hash;
        if (_PyDict_HasSplitTable(mp)) {
            assert(mp->ma_values[mp->ma_keys->dk_nentries] == NULL);
            mp->ma_values[mp->ma_keys->dk_nentries] = value;
        }
        else {
            ep->me_value = value;
        }
        mp->ma_used++;
        mp->ma_version_tag = DICT_NEXT_VERSION();
        mp->ma_keys->dk_usable--;
        mp->ma_keys->dk_nentries++;
        assert(mp->ma_keys->dk_usable >= 0);
    }
    else if (value == NULL) {
        value = defaultobj;
        assert(_PyDict_HasSplitTable(mp));
        assert(ix == mp->ma_used);
        Py_INCREF(value);
        MAINTAIN_TRACKING(mp, key, value);
        mp->ma_values[ix] = value;
        mp->ma_used++;
        mp->ma_version_tag = DICT_NEXT_VERSION();
    }

    ASSERT_CONSISTENT(mp);
    return value;
}

七、update(dict)

update()是把两个字典合并成一个新的字典，中间有交叉的key，更新替换成新值，没有交叉就直接创建

1、dict_update_common

static int
dict_update_common(PyObject *self, PyObject *args, PyObject *kwds,
                   const char *methname)
{
    PyObject *arg = NULL;
    int result = 0;

    if (!PyArg_UnpackTuple(args, methname, 0, 1, &arg)) {
        result = -1;
    }
    else if (arg != NULL) {
        if (PyDict_CheckExact(arg)) {
            result = PyDict_Merge(self, arg, 1);
        }
        else {
            _Py_IDENTIFIER(keys);
            PyObject *func;
            if (_PyObject_LookupAttrId(arg, &PyId_keys, &func) < 0) {
                result = -1;
            }
            else if (func != NULL) {
                Py_DECREF(func);
                result = PyDict_Merge(self, arg, 1);
            }
            else {
                result = PyDict_MergeFromSeq2(self, arg, 1);
            }
        }
    }

    if (result == 0 && kwds != NULL) {
        if (PyArg_ValidateKeywordArguments(kwds))
            result = PyDict_Merge(self, kwds, 1);
        else
            result = -1;
    }
    return result;
}

2、dict_update

static PyObject *
dict_update(PyObject *self, PyObject *args, PyObject *kwds)
{
    if (dict_update_common(self, args, kwds, "update") != -1)
        Py_RETURN_NONE;
    return NULL;
}

/* Update unconditionally replaces existing items.
   Merge has a 3rd argument ‘override‘; if set, it acts like Update,
   otherwise it leaves existing items unchanged.
   PyDict_{Update,Merge} update/merge from a mapping object.
   PyDict_MergeFromSeq2 updates/merges from any iterable object
   producing iterable objects of length 2.
*/

3、PyDict_Update

int
PyDict_Update(PyObject *a, PyObject *b)
{
    return dict_merge(a, b, 1);
}

八、items()将字典转换为列表

1、PyDict_Items

PyObject *
PyDict_Items(PyObject *mp)
{
    if (mp == NULL || !PyDict_Check(mp)) {
        PyErr_BadInternalCall();
        return NULL;
    }
    return dict_items((PyDictObject *)mp);
}

/* Return 1 if dicts equal, 0 if not, -1 if error.
 * Gets out as soon as any difference is detected.
 * Uses only Py_EQ comparison.
 */

九、fromkeys(list,默认值)

1、_PyDict_FromKeys

/* Internal version of dict.from_keys().  It is subclass-friendly. */
PyObject *
_PyDict_FromKeys(PyObject *cls, PyObject *iterable, PyObject *value)
{
    PyObject *it;       /* iter(iterable) */
    PyObject *key;
    PyObject *d;
    int status;

    d = _PyObject_CallNoArg(cls);
    if (d == NULL)
        return NULL;

    if (PyDict_CheckExact(d) && ((PyDictObject *)d)->ma_used == 0) {
        if (PyDict_CheckExact(iterable)) {
            PyDictObject *mp = (PyDictObject *)d;
            PyObject *oldvalue;
            Py_ssize_t pos = 0;
            PyObject *key;
            Py_hash_t hash;

            if (dictresize(mp, ESTIMATE_SIZE(PyDict_GET_SIZE(iterable)))) {
                Py_DECREF(d);
                return NULL;
            }

            while (_PyDict_Next(iterable, &pos, &key, &oldvalue, &hash)) {
                if (insertdict(mp, key, hash, value)) {
                    Py_DECREF(d);
                    return NULL;
                }
            }
            return d;
        }
        if (PyAnySet_CheckExact(iterable)) {
            PyDictObject *mp = (PyDictObject *)d;
            Py_ssize_t pos = 0;
            PyObject *key;
            Py_hash_t hash;

            if (dictresize(mp, ESTIMATE_SIZE(PySet_GET_SIZE(iterable)))) {
                Py_DECREF(d);
                return NULL;
            }

            while (_PySet_NextEntry(iterable, &pos, &key, &hash)) {
                if (insertdict(mp, key, hash, value)) {
                    Py_DECREF(d);
                    return NULL;
                }
            }
            return d;
        }
    }

    it = PyObject_GetIter(iterable);
    if (it == NULL){
        Py_DECREF(d);
        return NULL;
    }

    if (PyDict_CheckExact(d)) {
        while ((key = PyIter_Next(it)) != NULL) {
            status = PyDict_SetItem(d, key, value);
            Py_DECREF(key);
            if (status < 0)
                goto Fail;
        }
    } else {
        while ((key = PyIter_Next(it)) != NULL) {
            status = PyObject_SetItem(d, key, value);
            Py_DECREF(key);
            if (status < 0)
                goto Fail;
        }
    }

    if (PyErr_Occurred())
        goto Fail;
    Py_DECREF(it);
    return d;

Fail:
    Py_DECREF(it);
    Py_DECREF(d);
    return NULL;
}

2、dict_fromkeys_impl

static PyObject *
dict_fromkeys_impl(PyTypeObject *type, PyObject *iterable, PyObject *value)
/*[clinic end generated code: output=8fb98e4b10384999 input=382ba4855d0f74c3]*/
{
    return _PyDict_FromKeys((PyObject *)type, iterable, value);
}

static int
dict_update_common(PyObject *self, PyObject *args, PyObject *kwds,
                   const char *methname)
{
    PyObject *arg = NULL;
    int result = 0;

    if (!PyArg_UnpackTuple(args, methname, 0, 1, &arg)) {
        result = -1;
    }
    else if (arg != NULL) {
        if (PyDict_CheckExact(arg)) {
            result = PyDict_Merge(self, arg, 1);
        }
        else {
            _Py_IDENTIFIER(keys);
            PyObject *func;
            if (_PyObject_LookupAttrId(arg, &PyId_keys, &func) < 0) {
                result = -1;
            }
            else if (func != NULL) {
                Py_DECREF(func);
                result = PyDict_Merge(self, arg, 1);
            }
            else {
                result = PyDict_MergeFromSeq2(self, arg, 1);
            }
        }
    }

    if (result == 0 && kwds != NULL) {
        if (PyArg_ValidateKeywordArguments(kwds))
            result = PyDict_Merge(self, kwds, 1);
        else
            result = -1;
    }
    return result;
}

/* Note: dict.update() uses the METH_VARARGS|METH_KEYWORDS calling convention.
   Using METH_FASTCALL|METH_KEYWORDS would make dict.update(**dict2) calls
   slower, see the issue #29312. */

十、Clea清空字典

1、PyDict_ClearFreeList

int
PyDict_ClearFreeList(void)
{
    PyDictObject *op;
    int ret = numfree + numfreekeys;
    while (numfree) {
        op = free_list[--numfree];
        assert(PyDict_CheckExact(op));
        PyObject_GC_Del(op);
    }
    while (numfreekeys) {
        PyObject_FREE(keys_free_list[--numfreekeys]);
    }
    return ret;
}

2、PyDict_Clea

void
PyDict_Clear(PyObject *op)
{
    PyDictObject *mp;
    PyDictKeysObject *oldkeys;
    PyObject **oldvalues;
    Py_ssize_t i, n;

    if (!PyDict_Check(op))
        return;
    mp = ((PyDictObject *)op);
    oldkeys = mp->ma_keys;
    oldvalues = mp->ma_values;
    if (oldvalues == empty_values)
        return;
    /* Empty the dict... */
    dictkeys_incref(Py_EMPTY_KEYS);
    mp->ma_keys = Py_EMPTY_KEYS;
    mp->ma_values = empty_values;
    mp->ma_used = 0;
    mp->ma_version_tag = DICT_NEXT_VERSION();
    /* ...then clear the keys and values */
    if (oldvalues != NULL) {
        n = oldkeys->dk_nentries;
        for (i = 0; i < n; i++)
            Py_CLEAR(oldvalues[i]);
        free_values(oldvalues);
        dictkeys_decref(oldkeys);
    }
    else {
       assert(oldkeys->dk_refcnt == 1);
       dictkeys_decref(oldkeys);
    }
    ASSERT_CONSISTENT(mp);
}

3、dict_clear

static PyObject *
dict_clear(PyDictObject *mp, PyObject *Py_UNUSED(ignored))
{
    PyDict_Clear((PyObject *)mp);
    Py_RETURN_NONE;
}

4、dict_tp_clear

static int
dict_tp_clear(PyObject *op)
{
    PyDict_Clear(op);
    return 0;
}