Object Protocol¶

PyObject *Py_GetConstant(unsigned int constant_id)¶

Part of the Stable ABI since version 3.13.

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 functions 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().

void PyObject_Dump(PyObject *op)¶

Dump an object op to stderr. This should only be used for debugging.

The output is intended to try dumping objects even after memory corruption:

Information is written starting with fields that are the least likely to crash when accessed.
This function can be called without an attached thread state, but it’s not recommended to do so: it can cause deadlocks.
An object that does not belong to the current interpreter may be dumped, but this may also cause crashes or unintended behavior.
Implement a heuristic to detect if the object memory has been freed. Don’t display the object contents in this case, only its memory address.
The output format may change at any time.

Example of output:

object address  : 0x7f80124702c0
object refcount : 2
object type     : 0x9902e0
object type name: str
object repr     : 'abcdef'

Added in version 3.15.

int PyObject_HasAttrWithError(PyObject *o, PyObject *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 aren’t propagated, but instead given to sys.unraisablehook(). 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.

The function must not be called with a NULL v and an exception set. This case can arise from forgetting NULL checks and would delete the attribute.

Changed in version 3.15: Must not be called with NULL value if an exception is set.

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 function must not be called with a NULL v and an exception set. This case can arise from forgetting NULL checks and would delete the attribute.

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