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)¶

Thread safety: Atomic.

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)¶

Thread safety: Atomic.

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. Thread safety: Atomic.

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.

The first argument can be a dict, a frozendict, or a mapping.

Changed in version 3.15: Also accept frozendict.

PyTypeObject PyDictProxy_Type¶

Part of the Stable ABI.

The type object for mapping proxy objects created by PyDictProxy_New() and for the read-only __dict__ attribute of many built-in types. A PyDictProxy_Type instance provides a dynamic, read-only view of an underlying dictionary: changes to the underlying dictionary are reflected in the proxy, but the proxy itself does not support mutation operations. This corresponds to types.MappingProxyType in Python.

void PyDict_Clear(PyObject *p)¶

Part of the Stable ABI. Thread safety: Atomic.

Empty an existing dictionary of all key-value pairs.

Do nothing if the argument is not a dict or a dict subclass.

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

Part of the Stable ABI. Thread safety: Safe for concurrent use on the same object.

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

The first argument can be a dict or a frozendict.

Note

The operation is atomic on free threading when key is str, int, float, bool or bytes.

Changed in version 3.15: Also accept frozendict.

int PyDict_ContainsString(PyObject *p, const char *key)¶

Thread safety: Atomic.

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

The first argument can be a dict or a frozendict.

Added in version 3.13.

Changed in version 3.15: Also accept frozendict.

PyObject *PyDict_Copy(PyObject *p)¶

Return value: New reference. Part of the Stable ABI. Thread safety: Atomic.

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. Thread safety: Safe for concurrent use on the same object.

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.

Note

The operation is atomic on free threading when key is str, int, float, bool or bytes.

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

Part of the Stable ABI. Thread safety: Atomic.

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. Thread safety: Safe for concurrent use on the same object.

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.

Note

The operation is atomic on free threading when key is str, int, float, bool or bytes.

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

Part of the Stable ABI. Thread safety: Atomic.

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

int PyDict_GetItemRef(PyObject *p, PyObject *key, PyObject **result)¶

Part of the Stable ABI since version 3.13. Thread safety: Safe for concurrent use on the same object.

Return a new strong reference to the object from dictionary p which has a key key:

• If the key is present, set *result to a new strong reference to the value and return 1.

• If the key is missing, set *result to NULL and return 0.

• On error, raise an exception, set *result to NULL and return -1.

The first argument can be a dict or a frozendict.

Note

The operation is atomic on free threading when key is str, int, float, bool or bytes.

Added in version 3.13.

Changed in version 3.15: Also accept frozendict.

See also the PyObject_GetItem() function.

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

Return value: Borrowed reference. Part of the Stable ABI. Thread safety: Safe to call from multiple threads with external synchronization only.

Return a borrowed reference to the object from dictionary p which has a key key. Return NULL if the key key is missing without setting an exception.

The first argument can be a dict or a frozendict.

Note

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

Note

In the free-threaded build, the returned borrowed reference may become invalid if another thread modifies the dictionary concurrently. Prefer PyDict_GetItemRef(), which returns a strong reference.

Changed in version 3.10: Calling this API without an attached thread state had been allowed for historical reason. It is no longer allowed.

Changed in version 3.15: Also accept frozendict.

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

Return value: Borrowed reference. Part of the Stable ABI. Thread safety: Safe to call from multiple threads with external synchronization only.

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.

Note

In the free-threaded build, the returned borrowed reference may become invalid if another thread modifies the dictionary concurrently. Prefer PyDict_GetItemRef(), which returns a strong reference.

Changed in version 3.15: Also accept frozendict.

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

Return value: Borrowed reference. Part of the Stable ABI. Thread safety: Safe to call from multiple threads with external synchronization only.

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.

Note

In the free-threaded build, the returned borrowed reference may become invalid if another thread modifies the dictionary concurrently. Prefer PyDict_GetItemStringRef(), which returns a strong reference.

Changed in version 3.15: Also accept frozendict.

int PyDict_GetItemStringRef(PyObject *p, const char *key, PyObject **result)¶

Part of the Stable ABI since version 3.13. Thread safety: Atomic.

Similar to PyDict_GetItemRef(), but key is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

Added in version 3.13.

Changed in version 3.15: Also accept frozendict.

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

Return value: Borrowed reference. Thread safety: Safe to call from multiple threads with external synchronization only.

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.

Added in version 3.4.

Note

In the free-threaded build, the returned borrowed reference may become invalid if another thread modifies the dictionary concurrently. Prefer PyDict_SetDefaultRef(), which returns a strong reference.

int PyDict_SetDefaultRef(PyObject *p, PyObject *key, PyObject *default_value, PyObject **result)¶

Part of the Stable ABI since version 3.15. Thread safety: Safe for concurrent use on the same object.

Inserts default_value into the dictionary p with a key of key if the key is not already present in the dictionary. If result is not NULL, then *result is set to a strong reference to either default_value, if the key was not present, or the existing value, if key was already present in the dictionary. Returns 1 if the key was present and default_value was not inserted, or 0 if the key was not present and default_value was inserted. On failure, returns -1, sets an exception, and sets *result to NULL.

For clarity: if you have a strong reference to default_value before calling this function, then after it returns, you hold a strong reference to both default_value and *result (if it’s not NULL). These may refer to the same object: in that case you hold two separate references to it.

Note

The operation is atomic on free threading when key is str, int, float, bool or bytes.

Added in version 3.13.

int PyDict_Pop(PyObject *p, PyObject *key, PyObject **result)¶

Thread safety: Safe for concurrent use on the same object.

Remove key from dictionary p and optionally return the removed value. Do not raise KeyError if the key is missing.

• If the key is present, set *result to a new reference to the removed value if result is not NULL, and return 1.

• If the key is missing, set *result to NULL if result is not NULL, and return 0.

• On error, raise an exception and return -1.

Similar to dict.pop(), but without the default value and not raising KeyError if the key is missing.

Note

The operation is atomic on free threading when key is str, int, float, bool or bytes.

Added in version 3.13.

int PyDict_PopString(PyObject *p, const char *key, PyObject **result)¶

Thread safety: Atomic.

Similar to PyDict_Pop(), but key is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

Added in version 3.13.

PyObject *PyDict_Items(PyObject *p)¶

Return value: New reference. Part of the Stable ABI. Thread safety: Atomic.

Return a PyListObject containing all the items from the dictionary.

The first argument can be a dict or a frozendict.

Changed in version 3.15: Also accept frozendict.

PyObject *PyDict_Keys(PyObject *p)¶

Return value: New reference. Part of the Stable ABI. Thread safety: Atomic.

Return a PyListObject containing all the keys from the dictionary.

The first argument can be a dict or a frozendict.

Changed in version 3.15: Also accept frozendict.

PyObject *PyDict_Values(PyObject *p)¶

Return value: New reference. Part of the Stable ABI. Thread safety: Atomic.

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

The first argument can be a dict or a frozendict.

Changed in version 3.15: Also accept frozendict.

Py_ssize_t PyDict_Size(PyObject *p)¶

Part of the Stable ABI. Thread safety: Atomic.

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

The argument can be a dict or a frozendict.

Changed in version 3.15: Also accept frozendict.

Py_ssize_t PyDict_GET_SIZE(PyObject *p)¶

Thread safety: Atomic.

Similar to PyDict_Size(), but without error checking.

Changed in version 3.15: Also accept frozendict.

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

Part of the Stable ABI. Thread safety: Safe to call from multiple threads with external synchronization only.

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.

The first argument can be a dict or a frozendict.

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);
}

The function is not thread-safe in the free-threaded build without external synchronization for a mutable dict. You can use Py_BEGIN_CRITICAL_SECTION to lock the dictionary while iterating over it:

Py_BEGIN_CRITICAL_SECTION(self->dict);
while (PyDict_Next(self->dict, &pos, &key, &value)) {
    ...
}
Py_END_CRITICAL_SECTION();

The function is thread-safe on a frozendict.

Note

On the free-threaded build, this function can be used safely inside a critical section. However, the references returned for pkey and pvalue are borrowed and are only valid while the critical section is held. If you need to use these objects outside the critical section or when the critical section can be suspended, create a strong reference (for example, using Py_NewRef()).

Changed in version 3.15: Also accept frozendict.

int PyDict_Merge(PyObject *a, PyObject *b, int override)¶

Part of the Stable ABI. Thread safety: Safe for concurrent use on the same object.

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.

Note

In the free-threaded build, when b is a dict (with the standard iterator), both a and b are locked for the duration of the operation. When b is a non-dict mapping, only a is locked; b may be concurrently modified by another thread.

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

Part of the Stable ABI. Thread safety: Safe for concurrent use on the same object.

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.

Note

In the free-threaded build, when b is a dict (with the standard iterator), both a and b are locked for the duration of the operation. When b is a non-dict mapping, only a is locked; b may be concurrently modified by another thread.

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

Part of the Stable ABI. Thread safety: Safe for concurrent use on the same object.

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

Note

In the free-threaded build, only a is locked. The iteration over seq2 is not synchronized; seq2 may be concurrently modified by another thread.

PyObject *PyDict_AsFrozenDictAndClear(PyObject *dict)¶

Return a new frozendict created from the existing dict instance.

Transfers all keys and values from dict to the newly allocated frozendict. Clears the input dict on success. Returns NULL with the exception set on error.

This function is intended for building a frozendict instance via a temporary dict that is not exposed to user code. To “freeze” an arbitrary dictionary, for example one received from the user as an argument, prefer PyFrozenDict_New() to leave the source intact.

CPython implementation detail: Works with O(1) complexity.

Added in version 3.16.

int PyDict_AddWatcher(PyDict_WatchCallback callback)¶

Thread safety: Safe to call from multiple threads with external synchronization only.

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.

Note

This function is not internally synchronized. In the free-threaded build, callers should ensure no concurrent calls to PyDict_AddWatcher() or PyDict_ClearWatcher() are in progress.

Added in version 3.12.

int PyDict_ClearWatcher(int watcher_id)¶

Thread safety: Safe to call from multiple threads with external synchronization only.

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.)

Note

This function is not internally synchronized. In the free-threaded build, callers should ensure no concurrent calls to PyDict_AddWatcher() or PyDict_ClearWatcher() are in progress.

Added in version 3.12.

int PyDict_Watch(int watcher_id, PyObject *dict)¶

Thread safety: Safe to call without external synchronization on distinct objects.

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.

Added in version 3.12.

int PyDict_Unwatch(int watcher_id, PyObject *dict)¶

Thread safety: Safe to call without external synchronization on distinct objects.

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.

Added in version 3.12.

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.

Added in version 3.12.

PY_FOREACH_DICT_EVENT(V)¶

Apply the macro V to each suffix of PyDict_WatchEvent constants. Currently expands to V(ADDED) V(MODIFIED) V(DELETED) V(CLONED) V(CLEARED) V(DEALLOCATED). The macro V must accept one event name and supply any punctuation needed between expansions.

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. Do not trigger Python code execution in the callback, as it could modify the dict as a side effect.

If event is PyDict_EVENT_DEALLOCATED, taking a new reference in the callback to the about-to-be-destroyed dictionary will resurrect it and prevent it from being freed at this time. When the resurrected object is destroyed later, any watcher callbacks active at that time will be called again.

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

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

There may already be a pending exception set on entry to the callback. In this case, the callback should return 0 with the same exception still set. This means the callback may not call any other API that can set an exception unless it saves and clears the exception state first, and restores it before returning.

Added in version 3.12.