# 字典对象

`PyDictObject`

  这个 `PyObject` 的子类型代表一个Python字典对象。

PyTypeObject `PyDict_Type`

  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 是字典对象或者字典类型的子类型的实例，则返回真。

int `PyDict_CheckExact`(PyObject *p)

  如果 p 是字典对象但不是字典类型的子类型的实例，则返回真。

PyObject* `PyDict_New`()
  Return value: New reference.

  返回一个新的空字典或者返回 NULL 表示失败。

PyObject* `PyDictProxy_New`(PyObject *mapping)
  Return value: New reference.

  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)

  清空现有字典的所有键值对。

int `PyDict_Contains`(PyObject *p, PyObject *key)

  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.

  返回与 p 包含相同键值对的新词典。

int `PyDict_SetItem`(PyObject *p, PyObject *key, PyObject *val)

  使用 key 作为键将 value 插入字典 p 。 key 必须为 hashable ；如果不是，会抛出 `TypeError` 异常。成功返回 `0` ，失败返回 `-1` 。

int `PyDict_SetItemString`(PyObject *p, const char *key, PyObject *val)

  使用 key 作为键将 value 插入到字典 p 中。key 必须为 `const char*`。键对象是由 `PyUnicode_FromString(key)` 创建的。成功时返回 `0`，失败时返回 `-1`。

int `PyDict_DelItem`(PyObject *p, PyObject *key)

  使用键 key 删除字典 p 中的条目。 key 必须是可哈希的；如果不是，则抛出 `TypeError` 异常。成功时返回 `0` ，失败时返回 `-1` 。

int `PyDict_DelItemString`(PyObject *p, const char *key)

  删除字典 p 中的条目，其中包含由字符串 key 指定的键。成功时返回“0，失败时返回“-1”。

PyObject* `PyDict_GetItem`(PyObject *p, PyObject *key)
  Return value: Borrowed reference.

  返回字典 p 中 key 作为键的对象。如果键 key 不存在则返回 NULL ，但可以使用 without 设置例外。

  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。

PyObject* `PyDict_GetItemWithError`(PyObject *p, PyObject *key)
  Return value: Borrowed reference.

  变种的 `PyDict_GetItem()` 会抛出异常。当异常发生，返回 NULL 并 设置异常。当键不存在，返回 NULL 但不会 设置异常。

PyObject* `PyDict_GetItemString`(PyObject *p, const char *key)
  Return value: Borrowed reference.

  这与 `PyDict_GetItem()` 一样，但是 key 需要指定一个 `const char*` ，而不是 `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.

  Return a `PyListObject` containing all the items from the dictionary.

PyObject* `PyDict_Keys`(PyObject *p)
  Return value: New reference.

  Return a `PyListObject` containing all the keys from the dictionary.

PyObject* `PyDict_Values`(PyObject *p)
  Return value: New reference.

  Return a `PyListObject` containing all the values from the dictionary p.

Py_ssize_t `PyDict_Size`(PyObject *p)

  Return the number of items in the dictionary. This is equivalent to `len(p)` on a dictionary.

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

  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... */
          ...
      }

  The dictionary p should not be mutated during iteration. It is safe to modify the values of the keys as you iterate over the dictionary, but only so long as the set of keys does not change. For example:

      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)

  Iterate over mapping object b adding key-value pairs to dictionary a. b may be a dictionary, or any object supporting `PyMapping_Keys()` and `PyObject_GetItem()`. If override is true, existing pairs in a will be replaced if a matching key is found in b, otherwise pairs will only be added if there is not a matching key in a. Return `0` on success or `-1` if an exception was raised.

int `PyDict_Update`(PyObject *a, PyObject *b)

  This is the same as `PyDict_Merge(a, b, 1)` in C, and is similar to `a.update(b)` in Python except that `PyDict_Update()` doesn't fall back to the iterating over a sequence of key value pairs if the second argument has no "keys" attribute. Return `0` on success or `-1` if an exception was raised.

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

  Update or merge into dictionary a, from the key-value pairs in seq2. seq2 must be an iterable object producing iterable objects of length 2, viewed as key-value pairs. In case of duplicate keys, the last wins if override is true, else the first wins. Return `0` on success or `-1` if an exception was raised. Equivalent Python (except for the return value):

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

int `PyDict_ClearFreeList`()

  Clear the free list. Return the total number of freed items.

  3.3 新版功能.