Object Protocol

PyObject *Py_GetConstant(unsigned int constant_id)

Part of the Stable ABI since version 3.13.

Get a strong reference to a constant.

Set an exception and return NULL if constant_id is invalid.

constant_id must be one of these constant identifiers:

Constant Identifier	Value	Returned object
Py_CONSTANT_NONE	0	None
Py_CONSTANT_FALSE	1	False
Py_CONSTANT_TRUE	2	True
Py_CONSTANT_ELLIPSIS	3	Ellipsis
Py_CONSTANT_NOT_IMPLEMENTED	4	NotImplemented
Py_CONSTANT_ZERO	5	0
Py_CONSTANT_ONE	6	1
Py_CONSTANT_EMPTY_STR	7	''
Py_CONSTANT_EMPTY_BYTES	8	b''
Py_CONSTANT_EMPTY_TUPLE	9	()

Numeric values are only given for projects which cannot use the constant identifiers.

Added in version 3.13.

CPython implementation detail: In CPython, all of these constants are immortal.

PyObject *Py_GetConstantBorrowed(unsigned int constant_id)

Part of the Stable ABI since version 3.13.

Similar to Py_GetConstant(), but return a borrowed reference.

This function is primarily intended for backwards compatibility: using Py_GetConstant() is recommended for new code.

The reference is borrowed from the interpreter, and is valid until the interpreter finalization.

Added in version 3.13.

PyObject *Py_NotImplemented

The NotImplemented singleton, used to signal that an operation is not implemented for the given type combination.

Py_RETURN_NOTIMPLEMENTED

Properly handle returning Py_NotImplemented from within a C function (that is, create a new strong reference to NotImplemented and return it).

Py_PRINT_RAW

Flag to be used with multiple functions that print the object (like PyObject_Print() and PyFile_WriteObject()). If passed, these function would use the str() of the object instead of the repr().

int PyObject_Print(PyObject *o, FILE *fp, int flags)

Print an object o, on file fp. Returns -1 on error. The flags argument is used to enable certain printing options. The only option currently supported is Py_PRINT_RAW; if given, the str() of the object is written instead of the repr().

int PyObject_HasAttrWithError(PyObject *o, const char *attr_name)

Part of the Stable ABI since version 3.13.

Returns 1 if o has the attribute attr_name, and 0 otherwise. This is equivalent to the Python expression hasattr(o, attr_name). On failure, return -1.

Added in version 3.13.

int PyObject_HasAttrStringWithError(PyObject *o, const char *attr_name)

Part of the Stable ABI since version 3.13.

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

Added in version 3.13.

int PyObject_HasAttr(PyObject *o, PyObject *attr_name)

Part of the Stable ABI.

Returns 1 if o has the attribute attr_name, and 0 otherwise. This function always succeeds.

Note

Exceptions that occur when this calls __getattr__() and __getattribute__() methods are silently ignored. For proper error handling, use PyObject_HasAttrWithError(), PyObject_GetOptionalAttr() or PyObject_GetAttr() instead.

int PyObject_HasAttrString(PyObject *o, const char *attr_name)

Part of the Stable ABI.

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

Note

Exceptions that occur when this calls __getattr__() and __getattribute__() methods or while creating the temporary str object are silently ignored. For proper error handling, use PyObject_HasAttrStringWithError(), PyObject_GetOptionalAttrString() or PyObject_GetAttrString() instead.

PyObject *PyObject_GetAttr(PyObject *o, PyObject *attr_name)

Return value: New reference. Part of the Stable ABI.

Retrieve an attribute named attr_name from object o. Returns the attribute value on success, or NULL on failure. This is the equivalent of the Python expression o.attr_name.

If the missing attribute should not be treated as a failure, you can use PyObject_GetOptionalAttr() instead.

PyObject *PyObject_GetAttrString(PyObject *o, const char *attr_name)

Return value: New reference. Part of the Stable ABI.

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

If the missing attribute should not be treated as a failure, you can use PyObject_GetOptionalAttrString() instead.

int PyObject_GetOptionalAttr(PyObject *obj, PyObject *attr_name, PyObject **result);

Part of the Stable ABI since version 3.13.

Variant of PyObject_GetAttr() which doesn’t raise AttributeError if the attribute is not found.

If the attribute is found, return 1 and set *result to a new strong reference to the attribute. If the attribute is not found, return 0 and set *result to NULL; the AttributeError is silenced. If an error other than AttributeError is raised, return -1 and set *result to NULL.

Added in version 3.13.

int PyObject_GetOptionalAttrString(PyObject *obj, const char *attr_name, PyObject **result);

Part of the Stable ABI since version 3.13.

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

Added in version 3.13.

PyObject *PyObject_GenericGetAttr(PyObject *o, PyObject *name)

Return value: New reference. Part of the Stable ABI.

Generic attribute getter function that is meant to be put into a type object’s tp_getattro slot. It looks for a descriptor in the dictionary of classes in the object’s MRO as well as an attribute in the object’s __dict__ (if present). As outlined in Implementing Descriptors, data descriptors take preference over instance attributes, while non-data descriptors don’t. Otherwise, an AttributeError is raised.

int PyObject_SetAttr(PyObject *o, PyObject *attr_name, PyObject *v)

Part of the Stable ABI.

Set the value of the attribute named attr_name, for object o, to the value v. Raise an exception and return -1 on failure; return 0 on success. This is the equivalent of the Python statement o.attr_name = v.

If v is NULL, the attribute is deleted. This behaviour is deprecated in favour of using PyObject_DelAttr(), but there are currently no plans to remove it.

int PyObject_SetAttrString(PyObject *o, const char *attr_name, PyObject *v)

Part of the Stable ABI.

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

If v is NULL, the attribute is deleted, but this feature is deprecated in favour of using PyObject_DelAttrString().

The number of different attribute names passed to this function should be kept small, usually by using a statically allocated string as attr_name. For attribute names that aren’t known at compile time, prefer calling PyUnicode_FromString() and PyObject_SetAttr() directly. For more details, see PyUnicode_InternFromString(), which may be used internally to create a key object.

int PyObject_GenericSetAttr(PyObject *o, PyObject *name, PyObject *value)

Part of the Stable ABI.

Generic attribute setter and deleter function that is meant to be put into a type object’s tp_setattro slot. It looks for a data descriptor in the dictionary of classes in the object’s MRO, and if found it takes preference over setting or deleting the attribute in the instance dictionary. Otherwise, the attribute is set or deleted in the object’s __dict__ (if present). On success, 0 is returned, otherwise an AttributeError is raised and -1 is returned.

int PyObject_DelAttr(PyObject *o, PyObject *attr_name)

Part of the Stable ABI since version 3.13.

Delete attribute named attr_name, for object o. Returns -1 on failure. This is the equivalent of the Python statement del o.attr_name.

int PyObject_DelAttrString(PyObject *o, const char *attr_name)

Part of the Stable ABI since version 3.13.

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

The number of different attribute names passed to this function should be kept small, usually by using a statically allocated string as attr_name. For attribute names that aren’t known at compile time, prefer calling PyUnicode_FromString() and PyObject_DelAttr() directly. For more details, see PyUnicode_InternFromString(), which may be used internally to create a key object for lookup.

PyObject *PyObject_GenericGetDict(PyObject *o, void *context)

Return value: New reference. Part of the Stable ABI since version 3.10.

A generic implementation for the getter of a __dict__ descriptor. It creates the dictionary if necessary.

This function may also be called to get the __dict__ of the object o. Pass NULL for context when calling it. Since this function may need to allocate memory for the dictionary, it may be more efficient to call PyObject_GetAttr() when accessing an attribute on the object.

On failure, returns NULL with an exception set.

Added in version 3.3.

int PyObject_GenericSetDict(PyObject *o, PyObject *value, void *context)

Part of the Stable ABI since version 3.7.

A generic implementation for the setter of a __dict__ descriptor. This implementation does not allow the dictionary to be deleted.

Added in version 3.3.

PyObject **_PyObject_GetDictPtr(PyObject *obj)

Return a pointer to __dict__ of the object obj. If there is no __dict__, return NULL without setting an exception.

This function may need to allocate memory for the dictionary, so it may be more efficient to call PyObject_GetAttr() when accessing an attribute on the object.

PyObject *PyObject_RichCompare(PyObject *o1, PyObject *o2, int opid)

Return value: New reference. Part of the Stable ABI.

Compare the values of o1 and o2 using the operation specified by opid, which must be one of Py_LT, Py_LE, Py_EQ, Py_NE, Py_GT, or Py_GE, corresponding to <, <=, ==, !=, >, or >= respectively. This is the equivalent of the Python expression o1 op o2, where op is the operator corresponding to opid. Returns the value of the comparison on success, or NULL on failure.

int PyObject_RichCompareBool(PyObject *o1, PyObject *o2, int opid)

Part of the Stable ABI.

Compare the values of o1 and o2 using the operation specified by opid, like PyObject_RichCompare(), but returns -1 on error, 0 if the result is false, 1 otherwise.

Note

If o1 and o2 are the same object, PyObject_RichCompareBool() will always return 1 for Py_EQ and 0 for Py_NE.

PyObject *PyObject_Format(PyObject *obj, PyObject *format_spec)

Part of the Stable ABI.

Format obj using format_spec. This is equivalent to the Python expression format(obj, format_spec).

format_spec may be NULL. In this case the call is equivalent to format(obj). Returns the formatted string on success, NULL on failure.

PyObject *PyObject_Repr(PyObject *o)

Return value: New reference. Part of the Stable ABI.

Compute a string representation of object o. Returns the string representation on success, NULL on failure. This is the equivalent of the Python expression repr(o). Called by the repr() built-in function.

Changed in version 3.4: This function now includes a debug assertion to help ensure that it does not silently discard an active exception.

PyObject *PyObject_ASCII(PyObject *o)

Return value: New reference. Part of the Stable ABI.

As PyObject_Repr(), compute a string representation of object o, but escape the non-ASCII characters in the string returned by PyObject_Repr() with \x, \u or \U escapes. This generates a string similar to that returned by PyObject_Repr() in Python 2. Called by the ascii() built-in function.

PyObject *PyObject_Str(PyObject *o)

Return value: New reference. Part of the Stable ABI.

Compute a string representation of object o. Returns the string representation on success, NULL on failure. This is the equivalent of the Python expression str(o). Called by the str() built-in function and, therefore, by the print() function.

Changed in version 3.4: This function now includes a debug assertion to help ensure that it does not silently discard an active exception.

PyObject *PyObject_Bytes(PyObject *o)

Return value: New reference. Part of the Stable ABI.

Compute a bytes representation of object o. NULL is returned on failure and a bytes object on success. This is equivalent to the Python expression bytes(o), when o is not an integer. Unlike bytes(o), a TypeError is raised when o is an integer instead of a zero-initialized bytes object.

int PyObject_IsSubclass(PyObject *derived, PyObject *cls)

Part of the Stable ABI.

Return 1 if the class derived is identical to or derived from the class cls, otherwise return 0. In case of an error, return -1.

If cls is a tuple, the check will be done against every entry in cls. The result will be 1 when at least one of the checks returns 1, otherwise it will be 0.

If cls has a __subclasscheck__() method, it will be called to determine the subclass status as described in PEP 3119. Otherwise, derived is a subclass of cls if it is a direct or indirect subclass, i.e. contained in cls.__mro__.

Normally only class objects, i.e. instances of type or a derived class, are considered classes. However, objects can override this by having a __bases__ attribute (which must be a tuple of base classes).

int PyObject_IsInstance(PyObject *inst, PyObject *cls)

Part of the Stable ABI.

Return 1 if inst is an instance of the class cls or a subclass of cls, or 0 if not. On error, returns -1 and sets an exception.

If cls is a tuple, the check will be done against every entry in cls. The result will be 1 when at least one of the checks returns 1, otherwise it will be 0.

If cls has a __instancecheck__() method, it will be called to determine the subclass status as described in PEP 3119. Otherwise, inst is an instance of cls if its class is a subclass of cls.

An instance inst can override what is considered its class by having a __class__ attribute.

An object cls can override if it is considered a class, and what its base classes are, by having a __bases__ attribute (which must be a tuple of base classes).

Py_hash_t PyObject_Hash(PyObject *o)

Part of the Stable ABI.

Compute and return the hash value of an object o. On failure, return -1. This is the equivalent of the Python expression hash(o).

Changed in version 3.2: The return type is now Py_hash_t. This is a signed integer the same size as Py_ssize_t.

Py_hash_t PyObject_HashNotImplemented(PyObject *o)

Part of the Stable ABI.

Set a TypeError indicating that type(o) is not hashable and return -1. This function receives special treatment when stored in a tp_hash slot, allowing a type to explicitly indicate to the interpreter that it is not hashable.

int PyObject_IsTrue(PyObject *o)

Part of the Stable ABI.

Returns 1 if the object o is considered to be true, and 0 otherwise. This is equivalent to the Python expression not not o. On failure, return -1.

int PyObject_Not(PyObject *o)

Part of the Stable ABI.

Returns 0 if the object o is considered to be true, and 1 otherwise. This is equivalent to the Python expression not o. On failure, return -1.

PyObject *PyObject_Type(PyObject *o)

Return value: New reference. Part of the Stable ABI.

When o is non-NULL, returns a type object corresponding to the object type of object o. On failure, raises SystemError and returns NULL. This is equivalent to the Python expression type(o). This function creates a new strong reference to the return value. There’s really no reason to use this function instead of the Py_TYPE() function, which returns a pointer of type PyTypeObject*, except when a new strong reference is needed.

int PyObject_TypeCheck(PyObject *o, PyTypeObject *type)

Return non-zero if the object o is of type type or a subtype of type, and 0 otherwise. Both parameters must be non-NULL.

Py_ssize_t PyObject_Size(PyObject *o)

Py_ssize_t PyObject_Length(PyObject *o)

Part of the Stable ABI.

Return the length of object o. If the object o provides either the sequence and mapping protocols, the sequence length is returned. On error, -1 is returned. This is the equivalent to the Python expression len(o).

Py_ssize_t PyObject_LengthHint(PyObject *o, Py_ssize_t defaultvalue)

Return an estimated length for the object o. First try to return its actual length, then an estimate using __length_hint__(), and finally return the default value. On error return -1. This is the equivalent to the Python expression operator.length_hint(o, defaultvalue).

Added in version 3.4.

PyObject *PyObject_GetItem(PyObject *o, PyObject *key)

Return value: New reference. Part of the Stable ABI.

Return element of o corresponding to the object key or NULL on failure. This is the equivalent of the Python expression o[key].

int PyObject_SetItem(PyObject *o, PyObject *key, PyObject *v)

Part of the Stable ABI.

Map the object key to the value v. Raise an exception and return -1 on failure; return 0 on success. This is the equivalent of the Python statement o[key] = v. This function does not steal a reference to v.

int PyObject_DelItem(PyObject *o, PyObject *key)

Part of the Stable ABI.

Remove the mapping for the object key from the object o. Return -1 on failure. This is equivalent to the Python statement del o[key].

PyObject *PyObject_Dir(PyObject *o)

Return value: New reference. Part of the Stable ABI.

This is equivalent to the Python expression dir(o), returning a (possibly empty) list of strings appropriate for the object argument, or NULL if there was an error. If the argument is NULL, this is like the Python dir(), returning the names of the current locals; in this case, if no execution frame is active then NULL is returned but PyErr_Occurred() will return false.

PyObject *PyObject_GetIter(PyObject *o)

Return value: New reference. Part of the Stable ABI.

This is equivalent to the Python expression iter(o). It returns a new iterator for the object argument, or the object itself if the object is already an iterator. Raises TypeError and returns NULL if the object cannot be iterated.

PyObject *PyObject_GetAIter(PyObject *o)

Return value: New reference. Part of the Stable ABI since version 3.10.

This is the equivalent to the Python expression aiter(o). Takes an AsyncIterable object and returns an AsyncIterator for it. This is typically a new iterator but if the argument is an AsyncIterator, this returns itself. Raises TypeError and returns NULL if the object cannot be iterated.

Added in version 3.10.

void *PyObject_GetTypeData(PyObject *o, PyTypeObject *cls)

Part of the Stable ABI since version 3.12.

Get a pointer to subclass-specific data reserved for cls.

The object o must be an instance of cls, and cls must have been created using negative PyType_Spec.basicsize. Python does not check this.

On error, set an exception and return NULL.

Added in version 3.12.

Py_ssize_t PyType_GetTypeDataSize(PyTypeObject *cls)

Part of the Stable ABI since version 3.12.

Return the size of the instance memory space reserved for cls, i.e. the size of the memory PyObject_GetTypeData() returns.

This may be larger than requested using -PyType_Spec.basicsize; it is safe to use this larger size (e.g. with memset()).

The type cls must have been created using negative PyType_Spec.basicsize. Python does not check this.

On error, set an exception and return a negative value.

Added in version 3.12.

void *PyObject_GetItemData(PyObject *o)

Get a pointer to per-item data for a class with Py_TPFLAGS_ITEMS_AT_END.

On error, set an exception and return NULL. TypeError is raised if o does not have Py_TPFLAGS_ITEMS_AT_END set.

Added in version 3.12.

int PyObject_VisitManagedDict(PyObject *obj, visitproc visit, void *arg)

Visit the managed dictionary of obj.

This function must only be called in a traverse function of the type which has the Py_TPFLAGS_MANAGED_DICT flag set.

Added in version 3.13.

void PyObject_ClearManagedDict(PyObject *obj)

Clear the managed dictionary of obj.

This function must only be called in a traverse function of the type which has the Py_TPFLAGS_MANAGED_DICT flag set.

Added in version 3.13.

int PyUnstable_Object_EnableDeferredRefcount(PyObject *obj)

This is Unstable API. It may change without warning in minor releases.

Enable deferred reference counting on obj, if supported by the runtime. In the free-threaded build, this allows the interpreter to avoid reference count adjustments to obj, which may improve multi-threaded performance. The tradeoff is that obj will only be deallocated by the tracing garbage collector.

This function returns 1 if deferred reference counting is enabled on obj (including when it was enabled before the call), and 0 if deferred reference counting is not supported or if the hint was ignored by the runtime. This function is thread-safe, and cannot fail.

This function does nothing on builds with the GIL enabled, which do not support deferred reference counting. This also does nothing if obj is not an object tracked by the garbage collector (see gc.is_tracked() and PyObject_GC_IsTracked()).

This function is intended to be used soon after obj is created, by the code that creates it.

Added in version 3.14.