# 字典对象

`PyDictObject`

  Python 的字典对象是 `PyObject` 的子类型。

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)

  Insert value into the dictionary p using key as a key. key should be a `char*`. The key object is created using `PyUnicode_FromString(key)`. Return `0` on success or `-1` on failure.

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。

PyObject* `PyDict_GetItemWithError`(PyObject *p, PyObject *key)

  Variant of `PyDict_GetItem()` that does not suppress exceptions. Return NULL with an exception set if an exception occurred. Return NULL without an exception set if the key wasn’t present.

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

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

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

  This is the same as the Python-level `dict.setdefault()`. If present, it returns the value corresponding to key from the dictionary p. If the key is not in the dict, it is inserted with value defaultobj and defaultobj is returned. This function evaluates the hash function of key only once, instead of evaluating it independently for the lookup and the insertion.

  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.