Dictionary Objects — Python 3.11.15 documentation

# 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