Dictionary Objects
******************

type PyDictObject

   This subtype of "PyObject" represents a Python dictionary object.

PyTypeObject PyDict_Type
    * Part of the Stable ABI.*

   This instance of "PyTypeObject" represents the Python dictionary
   type.  This is the same object as "dict" in the Python layer.

int PyDict_Check(PyObject *p)

   Return true if *p* is a dict object or an instance of a subtype of
   the dict type.  This function always succeeds.

int PyDict_CheckExact(PyObject *p)

   Return true if *p* is a dict object, but not an instance of a
   subtype of the dict type.  This function always succeeds.

PyObject *PyDict_New()
    *Return value: New reference.** Part of the Stable ABI.*

   Return a new empty dictionary, or "NULL" on failure.

PyObject *PyDictProxy_New(PyObject *mapping)
    *Return value: New reference.** Part of the Stable ABI.*

   Return a "types.MappingProxyType" object for a mapping which
   enforces read-only behavior.  This is normally used to create a
   view to prevent modification of the dictionary for non-dynamic
   class types.

void PyDict_Clear(PyObject *p)
    * Part of the Stable ABI.*

   Empty an existing dictionary of all key-value pairs.

int PyDict_Contains(PyObject *p, PyObject *key)
    * Part of the Stable ABI.*

   Determine if dictionary *p* contains *key*.  If an item in *p* is
   matches *key*, return "1", otherwise return "0".  On error, return
   "-1". This is equivalent to the Python expression "key in p".

PyObject *PyDict_Copy(PyObject *p)
    *Return value: New reference.** Part of the Stable ABI.*

   Return a new dictionary that contains the same key-value pairs as
   *p*.

int PyDict_SetItem(PyObject *p, PyObject *key, PyObject *val)
    * Part of the Stable ABI.*

   Insert *val* into the dictionary *p* with a key of *key*.  *key*
   must be *hashable*; if it isn’t, "TypeError" will be raised. Return
   "0" on success or "-1" on failure.  This function *does not* steal
   a reference to *val*.

int PyDict_SetItemString(PyObject *p, const char *key, PyObject *val)
    * Part of the Stable ABI.*

   This is the same as "PyDict_SetItem()", but *key* is specified as a
   const char* UTF-8 encoded bytes string, rather than a PyObject*.

int PyDict_DelItem(PyObject *p, PyObject *key)
    * Part of the Stable ABI.*

   Remove the entry in dictionary *p* with key *key*. *key* must be
   *hashable*; if it isn’t, "TypeError" is raised. If *key* is not in
   the dictionary, "KeyError" is raised. Return "0" on success or "-1"
   on failure.

int PyDict_DelItemString(PyObject *p, const char *key)
    * Part of the Stable ABI.*

   This is the same as "PyDict_DelItem()", but *key* is specified as a
   const char* UTF-8 encoded bytes string, rather than a PyObject*.

PyObject *PyDict_GetItem(PyObject *p, PyObject *key)
    *Return value: Borrowed reference.** Part of the Stable ABI.*

   Return the object from dictionary *p* which has a key *key*.
   Return "NULL" if the key *key* is not present, but *without*
   setting an exception.

   Note:

     Exceptions that occur while this calls "__hash__()" and
     "__eq__()" methods are silently ignored. Prefer the
     "PyDict_GetItemWithError()" function instead.

   Changed in version 3.10: Calling this API without *GIL* held had
   been allowed for historical reason. It is no longer allowed.

PyObject *PyDict_GetItemWithError(PyObject *p, PyObject *key)
    *Return value: Borrowed reference.** Part of the Stable ABI.*

   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.** Part of the Stable ABI.*

   This is the same as "PyDict_GetItem()", but *key* is specified as a
   const char* UTF-8 encoded bytes string, rather than a PyObject*.

   Note:

     Exceptions that occur while this calls "__hash__()" and
     "__eq__()" methods or while creating the temporary "str" object
     are silently ignored. Prefer using the
     "PyDict_GetItemWithError()" function with your own
     "PyUnicode_FromString()" *key* instead.

PyObject *PyDict_SetDefault(PyObject *p, PyObject *key, PyObject *defaultobj)
    *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.

   New in version 3.4.

PyObject *PyDict_Items(PyObject *p)
    *Return value: New reference.** Part of the Stable ABI.*

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

PyObject *PyDict_Keys(PyObject *p)
    *Return value: New reference.** Part of the Stable ABI.*

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

PyObject *PyDict_Values(PyObject *p)
    *Return value: New reference.** Part of the Stable ABI.*

   Return a "PyListObject" containing all the values from the
   dictionary *p*.

Py_ssize_t PyDict_Size(PyObject *p)
    * Part of the Stable ABI.*

   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)
    * 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.

   For example:

      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)
    * Part of the Stable ABI.*

   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)
    * Part of the Stable ABI.*

   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)
    * Part of the Stable ABI.*

   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
