字典对象¶

type PyDictObject¶: 这个 PyObject 的子类型代表一个Python字典对象。

PyTypeObject PyDict_Type¶: Part of the Stable ABI.
Python字典类型表示为 PyTypeObject 的实例。这与Python层面的 dict 是相同的对象。

int PyDict_Check(PyObject *p)¶: 如果 p 是一个 dict 对象或者 dict 类型的子类型的实例则返回真值。此函数总是会成功执行。

int PyDict_CheckExact(PyObject *p)¶: 如果 p 是一个 dict 对象但不是 dict 类型的子类型的实例则返回真值。此函数总是会成功执行。

PyObject *PyDict_New()¶: Return value: New reference. Part of the Stable ABI.
返回一个新的空字典，失败时返回 NULL。

PyObject *PyDictProxy_New(PyObject *mapping)¶: Return value: New reference. Part of the Stable ABI.
返回 types.MappingProxyType 对象，用于强制执行只读行为的映射。这通常用于创建视图以防止修改非动态类类型的字典。

void PyDict_Clear(PyObject *p)¶: Part of the Stable ABI.
清空现有字典的所有键值对。

int PyDict_Contains(PyObject *p, PyObject *key)¶: Part of the Stable ABI.
确定 key 是否包含在字典 p 中。如果 key 匹配上 p 的某一项，则返回 1 ，否则返回 0 。返回 -1 表示出错。这等同于Python表达式 key in p 。

PyObject *PyDict_Copy(PyObject *p)¶: Return value: New reference. Part of the Stable ABI.
返回与 p 包含相同键值对的新字典。

int PyDict_SetItem(PyObject *p, PyObject *key, PyObject *val)¶: Part of the Stable ABI.
使用 key 作为键将 val 插入字典 p。 key 必须为 hashable；如果不是，则将引发 TypeError。成功时返回 0，失败时返回 -1。此函数不会附带对 val 的引用。

int PyDict_SetItemString(PyObject *p, const char *key, PyObject *val)¶: Part of the Stable ABI.
Insert val into the dictionary p using key as a key. key should be a const char*. The key object is created using PyUnicode_FromString(key). Return 0 on success or -1 on failure. This function does not steal a reference to val.

int PyDict_DelItem(PyObject *p, PyObject *key)¶: Part of the Stable ABI.
移除字典 p 中键为 key 的条目。 key 必须是可哈希的；如果不是，则会引发 TypeError。如果字典中没有 key，则会引发 KeyError。成功时返回 0，失败时返回 -1。

int PyDict_DelItemString(PyObject *p, const char *key)¶: Part of the Stable ABI.
移除字典 p 中由字符串 key 指定的键的条目。如果字典中没有 key，则会引发 KeyError。成功时返回 0，失败时返回 -1。

PyObject *PyDict_GetItem(PyObject *p, PyObject *key)¶

Return value: Borrowed reference. Part of the Stable ABI.

从字典 p 中返回以 key 为键的对象。如果键名 key 不存在但没有设置一个异常则返回 NULL。

需要注意的是，调用 __hash__() 和 __eq__() 方法产生的异常不会被抛出。改用 PyDict_GetItemWithError() 获得错误报告。

在 3.10 版更改: 在不保持 GIL 的情况下调用此 API 曾因历史原因而被允许。现在已不再被允许。

PyObject *PyDict_GetItemWithError(PyObject *p, PyObject *key)¶: Return value: Borrowed reference. Part of the Stable ABI.
PyDict_GetItem() 的变种，它不会屏蔽异常。当异常发生时将返回 NULL 并且设置一个异常。如果键不存在则返回 NULL 并且不会 设置一个异常。

PyObject *PyDict_GetItemString(PyObject *p, const char *key)¶

Return value: Borrowed reference. Part of the Stable ABI.

This is the same as PyDict_GetItem(), but key is specified as a const char*, rather than a PyObject*.

需要注意的是，调用 __hash__() 、 __eq__() 方法和创建一个临时的字符串对象时产生的异常不会被抛出。改用 PyDict_GetItemWithError() 获得错误报告。

PyObject *PyDict_SetDefault(PyObject *p, PyObject *key, PyObject *defaultobj)¶: Return value: Borrowed reference.
这跟Python层面的 dict.setdefault() 一样。如果键 key 存在，它返回在字典 p 里面对应的值。如果键不存在，它会和值 defaultobj 一起插入并返回 defaultobj 。这个函数只计算 key 的哈希函数一次，而不是在查找和插入时分别计算它。

3.4 新版功能.

PyObject *PyDict_Items(PyObject *p)¶: Return value: New reference. Part of the Stable ABI.
返回一个包含字典中所有键值项的 PyListObject。

PyObject *PyDict_Keys(PyObject *p)¶: Return value: New reference. Part of the Stable ABI.
返回一个包含字典中所有键(keys)的 PyListObject。

PyObject *PyDict_Values(PyObject *p)¶: Return value: New reference. Part of the Stable ABI.
返回一个包含字典中所有值(values)的 PyListObject。

Py_ssize_t PyDict_Size(PyObject *p)¶: Part of the Stable ABI.
返回字典中项目数，等价于对字典 p 使用 len(p)。

int PyDict_Next(PyObject *p, Py_ssize_t *ppos, PyObject **pkey, PyObject **pvalue)¶

Part of the Stable ABI.

Iterate over all key-value pairs in the dictionary p. The Py_ssize_t referred to by ppos must be initialized to 0 prior to the first call to this function to start the iteration; the function returns true for each pair in the dictionary, and false once all pairs have been reported. The parameters pkey and pvalue should either point to PyObject* variables that will be filled in with each key and value, respectively, or may be NULL. Any references returned through them are borrowed. ppos should not be altered during iteration. Its value represents offsets within the internal dictionary structure, and since the structure is sparse, the offsets are not consecutive.

例如：

PyObject *key, *value;
Py_ssize_t pos = 0;

while (PyDict_Next(self->dict, &pos, &key, &value)) {
    /* do something interesting with the values... */
    ...
}

字典 p 不应该在遍历期间发生改变。在遍历字典时，改变键中的值是安全的，但仅限于键的集合不发生改变。例如:

PyObject *key, *value;
Py_ssize_t pos = 0;

while (PyDict_Next(self->dict, &pos, &key, &value)) {
    long i = PyLong_AsLong(value);
    if (i == -1 && PyErr_Occurred()) {
        return -1;
    }
    PyObject *o = PyLong_FromLong(i + 1);
    if (o == NULL)
        return -1;
    if (PyDict_SetItem(self->dict, key, o) < 0) {
        Py_DECREF(o);
        return -1;
    }
    Py_DECREF(o);
}

int PyDict_Merge(PyObject *a, PyObject *b, int override)¶: Part of the Stable ABI.
对映射对象 b 进行迭代，将键值对添加到字典 a。 b 可以是一个字典，或任何支持 PyMapping_Keys() 和 PyObject_GetItem() 的对象。如果 override 为真值，则如果在 b 中找到相同的键则 a 中已存在的相应键值对将被替换，否则如果在 a 中没有相同的键则只是添加键值对。当成功时返回 0 或者当引发异常时返回 -1。

int PyDict_Update(PyObject *a, PyObject *b)¶: Part of the Stable ABI.
这与 C 中的 PyDict_Merge(a, b, 1) 一样，也类似于 Python 中的 a.update(b)，差别在于 PyDict_Update() 在第二个参数没有 “keys” 属性时不会回退到迭代键值对的序列。当成功时返回 0 或者当引发异常时返回 -1。

int PyDict_MergeFromSeq2(PyObject *a, PyObject *seq2, int override)¶

Part of the Stable ABI.

将 seq2 中的键值对更新或合并到字典 a。 seq2 必须为产生长度为 2 的用作键值对的元素的可迭代对象。当存在重复的键时，如果 override 真值则最后出现的键胜出。当成功时返回 0 或者当引发异常时返回 -1。等价的 Python 代码（返回值除外）:

def PyDict_MergeFromSeq2(a, seq2, override):
    for key, value in seq2:
        if override or key not in a:
            a[key] = value

int PyDict_AddWatcher(PyDict_WatchCallback callback)¶: Register callback as a dictionary watcher. Return a non-negative integer id which must be passed to future calls to PyDict_Watch(). In case of error (e.g. no more watcher IDs available), return -1 and set an exception.

3.12 新版功能.

int PyDict_ClearWatcher(int watcher_id)¶: Clear watcher identified by watcher_id previously returned from PyDict_AddWatcher(). Return 0 on success, -1 on error (e.g. if the given watcher_id was never registered.)

3.12 新版功能.

int PyDict_Watch(int watcher_id, PyObject *dict)¶: Mark dictionary dict as watched. The callback granted watcher_id by PyDict_AddWatcher() will be called when dict is modified or deallocated. Return 0 on success or -1 on error.

3.12 新版功能.

int PyDict_Unwatch(int watcher_id, PyObject *dict)¶: Mark dictionary dict as no longer watched. The callback granted watcher_id by PyDict_AddWatcher() will no longer be called when dict is modified or deallocated. The dict must previously have been watched by this watcher. Return 0 on success or -1 on error.

3.12 新版功能.

type PyDict_WatchEvent¶: Enumeration of possible dictionary watcher events: PyDict_EVENT_ADDED, PyDict_EVENT_MODIFIED, PyDict_EVENT_DELETED, PyDict_EVENT_CLONED, PyDict_EVENT_CLEARED, or PyDict_EVENT_DEALLOCATED.

3.12 新版功能.

typedef int (*PyDict_WatchCallback)(PyDict_WatchEvent event, PyObject *dict, PyObject *key, PyObject *new_value)¶

Type of a dict watcher callback function.

If event is PyDict_EVENT_CLEARED or PyDict_EVENT_DEALLOCATED, both key and new_value will be NULL. If event is PyDict_EVENT_ADDED or PyDict_EVENT_MODIFIED, new_value will be the new value for key. If event is PyDict_EVENT_DELETED, key is being deleted from the dictionary and new_value will be NULL.

PyDict_EVENT_CLONED occurs when dict was previously empty and another dict is merged into it. To maintain efficiency of this operation, per-key PyDict_EVENT_ADDED events are not issued in this case; instead a single PyDict_EVENT_CLONED is issued, and key will be the source dictionary.

The callback may inspect but must not modify dict; doing so could have unpredictable effects, including infinite recursion.

Callbacks occur before the notified modification to dict takes place, so the prior state of dict can be inspected.

If the callback returns with an exception set, it must return -1; this exception will be printed as an unraisable exception using PyErr_WriteUnraisable(). Otherwise it should return 0.

3.12 新版功能.

字典对象¶

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