Object Protocol¶

PyObject*Py_GetConstant(unsignedintconstant_id)¶

Part of theStable ABI since version 3.13.

Get astrong reference to a constant.

Set an exception and returnNULL ifconstant_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 constantidentifiers.

Added in version 3.13.

CPython implementation detail: In CPython, all of these constants areimmortal.

PyObject*Py_GetConstantBorrowed(unsignedintconstant_id)¶

Part of theStable ABI since version 3.13.

Similar toPy_GetConstant(), but return aborrowedreference.

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

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

Added in version 3.13.

PyObject*Py_NotImplemented¶

TheNotImplemented singleton, used to signal that an operation isnot implemented for the given type combination.

Py_RETURN_NOTIMPLEMENTED¶

Properly handle returningPy_NotImplemented from within a Cfunction (that is, create a newstrong referencetoNotImplemented and return it).

Py_PRINT_RAW¶

Flag to be used with multiple functions that print the object (likePyObject_Print() andPyFile_WriteObject()).If passed, these functions use thestr() of the objectinstead of therepr().

intPyObject_Print(PyObject*o,FILE*fp,intflags)¶

Print an objecto, on filefp. Returns-1 on error. The flags argumentis used to enable certain printing options. The only option currently supportedisPy_PRINT_RAW; if given, thestr() of the object is writteninstead of therepr().

intPyObject_HasAttrWithError(PyObject*o,PyObject*attr_name)¶

Part of theStable ABI since version 3.13.

Returns1 ifo has the attributeattr_name, and0 otherwise.This is equivalent to the Python expressionhasattr(o,attr_name).On failure, return-1.

Added in version 3.13.

intPyObject_HasAttrStringWithError(PyObject*o,constchar*attr_name)¶

Part of theStable ABI since version 3.13.

This is the same asPyObject_HasAttrWithError(), butattr_name isspecified as aconstchar* UTF-8 encoded bytes string,rather than aPyObject*.

Added in version 3.13.

intPyObject_HasAttr(PyObject*o,PyObject*attr_name)¶

Part of theStable ABI.

Returns1 ifo has the attributeattr_name, and0 otherwise.This function always succeeds.

Note

Exceptions that occur when this calls__getattr__() and__getattribute__() methods aren’t propagated,but instead given tosys.unraisablehook().For proper error handling, usePyObject_HasAttrWithError(),PyObject_GetOptionalAttr() orPyObject_GetAttr() instead.

intPyObject_HasAttrString(PyObject*o,constchar*attr_name)¶

Part of theStable ABI.

This is the same asPyObject_HasAttr(), butattr_name isspecified as aconstchar* UTF-8 encoded bytes string,rather than aPyObject*.

Note

Exceptions that occur when this calls__getattr__() and__getattribute__() methods or while creating the temporarystr object are silently ignored.For proper error handling, usePyObject_HasAttrStringWithError(),PyObject_GetOptionalAttrString()orPyObject_GetAttrString() instead.

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

Return value: New reference. Part of theStable ABI.

Retrieve an attribute namedattr_name from objecto. Returns the attributevalue on success, orNULL on failure. This is the equivalent of the Pythonexpressiono.attr_name.

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

PyObject*PyObject_GetAttrString(PyObject*o,constchar*attr_name)¶

Return value: New reference. Part of theStable ABI.

This is the same asPyObject_GetAttr(), butattr_name isspecified as aconstchar* UTF-8 encoded bytes string,rather than aPyObject*.

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

intPyObject_GetOptionalAttr(PyObject*obj,PyObject*attr_name,PyObject**result);¶

Part of theStable ABI since version 3.13.

Variant ofPyObject_GetAttr() which doesn’t raiseAttributeError if the attribute is not found.

If the attribute is found, return1 and set*result to a newstrong reference to the attribute.If the attribute is not found, return0 and set*result toNULL;theAttributeError is silenced.If an error other thanAttributeError is raised, return-1 andset*result toNULL.

Added in version 3.13.

intPyObject_GetOptionalAttrString(PyObject*obj,constchar*attr_name,PyObject**result);¶

Part of theStable ABI since version 3.13.

This is the same asPyObject_GetOptionalAttr(), butattr_name isspecified as aconstchar* UTF-8 encoded bytes string,rather than aPyObject*.

Added in version 3.13.

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

Return value: New reference. Part of theStable ABI.

Generic attribute getter function that is meant to be put into a typeobject’stp_getattro slot. It looks for a descriptor in the dictionaryof classes in the object’s MRO as well as an attribute in the object’s__dict__ (if present). As outlined inImplementing Descriptors,data descriptors take preference over instance attributes, while non-datadescriptors don’t. Otherwise, anAttributeError is raised.

intPyObject_SetAttr(PyObject*o,PyObject*attr_name,PyObject*v)¶

Part of theStable ABI.

Set the value of the attribute namedattr_name, for objecto, to the valuev. Raise an exception and return-1 on failure;return0 on success. This is the equivalent of the Python statemento.attr_name=v.

Ifv isNULL, the attribute is deleted. This behaviour is deprecatedin favour of usingPyObject_DelAttr(), but there are currently noplans to remove it.

intPyObject_SetAttrString(PyObject*o,constchar*attr_name,PyObject*v)¶

Part of theStable ABI.

This is the same asPyObject_SetAttr(), butattr_name isspecified as aconstchar* UTF-8 encoded bytes string,rather than aPyObject*.

Ifv isNULL, the attribute is deleted, but this feature isdeprecated in favour of usingPyObject_DelAttrString().

The number of different attribute names passed to this functionshould be kept small, usually by using a statically allocated stringasattr_name.For attribute names that aren’t known at compile time, prefer callingPyUnicode_FromString() andPyObject_SetAttr() directly.For more details, seePyUnicode_InternFromString(), which may beused internally to create a key object.

intPyObject_GenericSetAttr(PyObject*o,PyObject*name,PyObject*value)¶

Part of theStable ABI.

Generic attribute setter and deleter function that is meantto be put into a type object’stp_setattroslot. It looks for a data descriptor in thedictionary of classes in the object’s MRO, and if found it takes preferenceover setting or deleting the attribute in the instance dictionary. Otherwise, theattribute is set or deleted in the object’s__dict__ (if present).On success,0 is returned, otherwise anAttributeErroris raised and-1 is returned.

intPyObject_DelAttr(PyObject*o,PyObject*attr_name)¶

Part of theStable ABI since version 3.13.

Delete attribute namedattr_name, for objecto. Returns-1 on failure.This is the equivalent of the Python statementdelo.attr_name.

intPyObject_DelAttrString(PyObject*o,constchar*attr_name)¶

Part of theStable ABI since version 3.13.

This is the same asPyObject_DelAttr(), butattr_name isspecified as aconstchar* UTF-8 encoded bytes string,rather than aPyObject*.

The number of different attribute names passed to this functionshould be kept small, usually by using a statically allocated stringasattr_name.For attribute names that aren’t known at compile time, prefer callingPyUnicode_FromString() andPyObject_DelAttr() directly.For more details, seePyUnicode_InternFromString(), which may beused internally to create a key object for lookup.

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

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

A generic implementation for the getter of a__dict__ descriptor. Itcreates the dictionary if necessary.

This function may also be called to get the__dict__of the objecto. PassNULL forcontext when calling it.Since this function may need to allocate memory for thedictionary, it may be more efficient to callPyObject_GetAttr()when accessing an attribute on the object.

On failure, returnsNULL with an exception set.

Added in version 3.3.

intPyObject_GenericSetDict(PyObject*o,PyObject*value,void*context)¶

Part of theStable ABI since version 3.7.

A generic implementation for the setter of a__dict__ descriptor. Thisimplementation 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 objectobj.If there is no__dict__, returnNULL without setting an exception.

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

PyObject*PyObject_RichCompare(PyObject*o1,PyObject*o2,intopid)¶

Return value: New reference. Part of theStable ABI.

Compare the values ofo1 ando2 using the operation specified byopid,which must be one ofPy_LT,Py_LE,Py_EQ,Py_NE,Py_GT, orPy_GE, corresponding to<,<=,==,!=,>, or>= respectively. This is the equivalent ofthe Python expressiono1opo2, whereop is the operator correspondingtoopid. Returns the value of the comparison on success, orNULL on failure.

intPyObject_RichCompareBool(PyObject*o1,PyObject*o2,intopid)¶

Part of theStable ABI.

Compare the values ofo1 ando2 using the operation specified byopid,likePyObject_RichCompare(), but returns-1 on error,0 ifthe result is false,1 otherwise.

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

Part of theStable ABI.

Formatobj usingformat_spec. This is equivalent to the Pythonexpressionformat(obj,format_spec).

format_spec may beNULL. In this case the call is equivalenttoformat(obj).Returns the formatted string on success,NULL on failure.

PyObject*PyObject_Repr(PyObject*o)¶

Return value: New reference. Part of theStable ABI.

Compute a string representation of objecto. Returns the stringrepresentation on success,NULL on failure. This is the equivalent of thePython expressionrepr(o). Called by therepr() built-in function.

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

PyObject*PyObject_ASCII(PyObject*o)¶

Return value: New reference. Part of theStable ABI.

AsPyObject_Repr(), compute a string representation of objecto, butescape the non-ASCII characters in the string returned byPyObject_Repr() with\x,\u or\U escapes. This generatesa string similar to that returned byPyObject_Repr() in Python 2.Called by theascii() built-in function.

PyObject*PyObject_Str(PyObject*o)¶

Return value: New reference. Part of theStable ABI.

Compute a string representation of objecto. Returns the stringrepresentation on success,NULL on failure. This is the equivalent of thePython expressionstr(o). Called by thestr() built-in functionand, therefore, by theprint() function.

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

PyObject*PyObject_Bytes(PyObject*o)¶

Return value: New reference. Part of theStable ABI.

Compute a bytes representation of objecto.NULL is returned onfailure and a bytes object on success. This is equivalent to the Pythonexpressionbytes(o), wheno is not an integer. Unlikebytes(o),a TypeError is raised wheno is an integer instead of a zero-initializedbytes object.

intPyObject_IsSubclass(PyObject*derived,PyObject*cls)¶

Part of theStable ABI.

Return1 if the classderived is identical to or derived from the classcls, otherwise return0. In case of an error, return-1.

Ifcls is a tuple, the check will be done against every entry incls.The result will be1 when at least one of the checks returns1,otherwise it will be0.

Ifcls has a__subclasscheck__() method, it will be called todetermine the subclass status as described inPEP 3119. Otherwise,derived is a subclass ofcls if it is a direct or indirect subclass,i.e. contained incls.__mro__.

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

intPyObject_IsInstance(PyObject*inst,PyObject*cls)¶

Part of theStable ABI.

Return1 ifinst is an instance of the classcls or a subclass ofcls, or0 if not. On error, returns-1 and sets an exception.

Ifcls is a tuple, the check will be done against every entry incls.The result will be1 when at least one of the checks returns1,otherwise it will be0.

Ifcls has a__instancecheck__() method, it will be called todetermine the subclass status as described inPEP 3119. Otherwise,instis an instance ofcls if its class is a subclass ofcls.

An instanceinst can override what is considered its class by having a__class__ attribute.

An objectcls can override if it is considered a class, and what its baseclasses are, by having a__bases__ attribute (which must be a tupleof base classes).

Py_hash_tPyObject_Hash(PyObject*o)¶

Part of theStable ABI.

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

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

Py_hash_tPyObject_HashNotImplemented(PyObject*o)¶

Part of theStable ABI.

Set aTypeError indicating thattype(o) is nothashable and return-1.This function receives special treatment when stored in atp_hash slot,allowing a type to explicitly indicate to the interpreter that it is nothashable.

intPyObject_IsTrue(PyObject*o)¶

Part of theStable ABI.

Returns1 if the objecto is considered to be true, and0 otherwise.This is equivalent to the Python expressionnotnoto. On failure, return-1.

intPyObject_Not(PyObject*o)¶

Part of theStable ABI.

Returns0 if the objecto is considered to be true, and1 otherwise.This is equivalent to the Python expressionnoto. On failure, return-1.

PyObject*PyObject_Type(PyObject*o)¶

Return value: New reference. Part of theStable ABI.

Wheno is non-NULL, returns a type object corresponding to the object typeof objecto. On failure, raisesSystemError and returnsNULL. Thisis equivalent to the Python expressiontype(o).This function creates a newstrong reference to the return value.There’s really no reason to use thisfunction instead of thePy_TYPE() function, which returns apointer of typePyTypeObject*, except when a newstrong reference is needed.

intPyObject_TypeCheck(PyObject*o,PyTypeObject*type)¶

Return non-zero if the objecto is of typetype or a subtype oftype, and0 otherwise. Both parameters must be non-NULL.

Py_ssize_tPyObject_Size(PyObject*o)¶

Py_ssize_tPyObject_Length(PyObject*o)¶

Part of theStable ABI.

Return the length of objecto. If the objecto provides either the sequenceand mapping protocols, the sequence length is returned. On error,-1 isreturned. This is the equivalent to the Python expressionlen(o).

Py_ssize_tPyObject_LengthHint(PyObject*o,Py_ssize_tdefaultvalue)¶

Return an estimated length for the objecto. First try to return itsactual length, then an estimate using__length_hint__(), andfinally return the default value. On error return-1. This is theequivalent to the Python expressionoperator.length_hint(o,defaultvalue).

Added in version 3.4.

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

Return value: New reference. Part of theStable ABI.

Return element ofo corresponding to the objectkey orNULL on failure.This is the equivalent of the Python expressiono[key].

intPyObject_SetItem(PyObject*o,PyObject*key,PyObject*v)¶

Part of theStable ABI.

Map the objectkey to the valuev. Raise an exception andreturn-1 on failure; return0 on success. This is theequivalent of the Python statemento[key]=v. This functiondoesnot steal a reference tov.

intPyObject_DelItem(PyObject*o,PyObject*key)¶

Part of theStable ABI.

Remove the mapping for the objectkey from the objecto. Return-1on failure. This is equivalent to the Python statementdelo[key].

intPyObject_DelItemString(PyObject*o,constchar*key)¶

Part of theStable ABI.

This is the same asPyObject_DelItem(), butkey isspecified as aconstchar* UTF-8 encoded bytes string,rather than aPyObject*.

PyObject*PyObject_Dir(PyObject*o)¶

Return value: New reference. Part of theStable ABI.

This is equivalent to the Python expressiondir(o), returning a (possiblyempty) list of strings appropriate for the object argument, orNULL if therewas an error. If the argument isNULL, this is like the Pythondir(),returning the names of the current locals; in this case, if no execution frameis active thenNULL is returned butPyErr_Occurred() will return false.

PyObject*PyObject_GetIter(PyObject*o)¶

Return value: New reference. Part of theStable ABI.

This is equivalent to the Python expressioniter(o). It returns a newiterator for the object argument, or the object itself if the object is alreadyan iterator. RaisesTypeError and returnsNULL if the object cannot beiterated.

PyObject*PyObject_SelfIter(PyObject*obj)¶

Return value: New reference. Part of theStable ABI.

This is equivalent to the Python__iter__(self):returnself method.It is intended foriterator types, to be used in thePyTypeObject.tp_iter slot.

PyObject*PyObject_GetAIter(PyObject*o)¶

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

This is the equivalent to the Python expressionaiter(o). Takes anAsyncIterable object and returns anAsyncIterator for it.This is typically a new iterator but if the argument is anAsyncIterator, this returns itself. RaisesTypeError andreturnsNULL if the object cannot be iterated.

Added in version 3.10.

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

Part of theStable ABI since version 3.12.

Get a pointer to subclass-specific data reserved forcls.

The objecto must be an instance ofcls, andcls must have beencreated using negativePyType_Spec.basicsize.Python does not check this.

On error, set an exception and returnNULL.

Added in version 3.12.

Py_ssize_tPyType_GetTypeDataSize(PyTypeObject*cls)¶

Part of theStable ABI since version 3.12.

Return the size of the instance memory space reserved forcls, i.e. the size of thememoryPyObject_GetTypeData() returns.

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

The typeclsmust have been created usingnegativePyType_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 withPy_TPFLAGS_ITEMS_AT_END.

On error, set an exception and returnNULL.TypeError is raised ifo does not havePy_TPFLAGS_ITEMS_AT_END set.

Added in version 3.12.

intPyObject_VisitManagedDict(PyObject*obj,visitprocvisit,void*arg)¶

Visit the managed dictionary ofobj.

This function must only be called in a traverse function of the type whichhas thePy_TPFLAGS_MANAGED_DICT flag set.

Added in version 3.13.

voidPyObject_ClearManagedDict(PyObject*obj)¶

Clear the managed dictionary ofobj.

This function must only be called in a clear function of the type whichhas thePy_TPFLAGS_MANAGED_DICT flag set.

Added in version 3.13.

intPyUnstable_Object_EnableDeferredRefcount(PyObject*obj)¶

This isUnstable API. It may change without warning in minor releases.

Enabledeferred reference counting onobj,if supported by the runtime. In thefree-threaded build,this allows the interpreter to avoid reference count adjustments toobj,which may improve multi-threaded performance. The tradeoff isthatobj will only be deallocated by the tracing garbage collector, andnot when the interpreter no longer has any references to it.

This function returns1 if deferred reference counting is enabled onobj,and0 if deferred reference counting is not supported or if the hint wasignored by the interpreter, such as when deferred reference counting is alreadyenabled onobj. This function is thread-safe, and cannot fail.

This function does nothing on builds with theGIL enabled, which donot support deferred reference counting. This also does nothing ifobj is notan object tracked by the garbage collector (seegc.is_tracked() andPyObject_GC_IsTracked()).

This function is intended to be used soon afterobj is created,by the code that creates it, such as in the object’stp_newslot.

Added in version 3.14.

intPyUnstable_Object_IsUniqueReferencedTemporary(PyObject*obj)¶

This isUnstable API. It may change without warning in minor releases.

Check ifobj is a unique temporary object.Returns1 ifobj is known to be a unique temporary object,and0 otherwise. This function cannot fail, but the check isconservative, and may return0 in some cases even ifobj is a uniquetemporary object.

If an object is a unique temporary, it is guaranteed that the current codehas the only reference to the object. For arguments to C functions, thisshould be used instead of checking if the reference count is1. Startingwith Python 3.14, the interpreter internally avoids some reference countmodifications when loading objects onto the operands stack byborrowing references when possible, which meansthat a reference count of1 by itself does not guarantee that a functionargument uniquely referenced.

In the example below,my_func is called with a unique temporary objectas its argument:

my_func([1,2,3])

In the example below,my_func isnot called with a unique temporaryobject as its argument, even if its refcount is1:

my_list=[1,2,3]my_func(my_list)

See also the functionPy_REFCNT().

Added in version 3.14.

intPyUnstable_IsImmortal(PyObject*obj)¶

This isUnstable API. It may change without warning in minor releases.

This function returns non-zero ifobj isimmortal, and zerootherwise. This function cannot fail.

Note

Objects that are immortal in one CPython version are not guaranteed tobe immortal in another.

Added in version 3.14.

intPyUnstable_TryIncRef(PyObject*obj)¶

This isUnstable API. It may change without warning in minor releases.

Increments the reference count ofobj if it is not zero. Returns1if the object’s reference count was successfully incremented. Otherwise,this function returns0.

PyUnstable_EnableTryIncRef() must have been calledearlier onobj or this function may spuriously return0 in thefree threading build.

This function is logically equivalent to the following C code, except thatit behaves atomically in thefree threading build:

if(Py_REFCNT(op)>0){Py_INCREF(op);return1;}return0;

This is intended as a building block for managing weak referenceswithout the overhead of a Pythonweak reference object.

Typically, correct use of this function requires support fromobj’sdeallocator (tp_dealloc).For example, the following sketch could be adapted to implement a“weakmap” that works like aWeakValueDictionaryfor a specific type:

PyMutexmutex;PyObject*add_entry(weakmap_key_type*key,PyObject*value){PyUnstable_EnableTryIncRef(value);weakmap_typeweakmap=...;PyMutex_Lock(&mutex);weakmap_add_entry(weakmap,key,value);PyMutex_Unlock(&mutex);Py_RETURN_NONE;}PyObject*get_value(weakmap_key_type*key){weakmap_typeweakmap=...;PyMutex_Lock(&mutex);PyObject*result=weakmap_find(weakmap,key);if(PyUnstable_TryIncRef(result)){// `result` is safe to usePyMutex_Unlock(&mutex);returnresult;}// if we get here, `result` is starting to be garbage-collected,// but has not been removed from the weakmap yetPyMutex_Unlock(&mutex);returnNULL;}// tp_dealloc function for weakmap valuesvoidvalue_dealloc(PyObject*value){weakmap_typeweakmap=...;PyMutex_Lock(&mutex);weakmap_remove_value(weakmap,value);...PyMutex_Unlock(&mutex);}

Added in version 3.14.

voidPyUnstable_EnableTryIncRef(PyObject*obj)¶

This isUnstable API. It may change without warning in minor releases.

Enables subsequent uses ofPyUnstable_TryIncRef() onobj. Thecaller must hold astrong reference toobj when calling this.

Added in version 3.14.

intPyUnstable_Object_IsUniquelyReferenced(PyObject*op)¶

This isUnstable API. It may change without warning in minor releases.

Determine ifop only has one reference.

On GIL-enabled builds, this function is equivalent toPy_REFCNT(op)==1.

On afree threaded build, this checks ifop’sreference count is equal to one and additionally checks ifopis only used by this thread.Py_REFCNT(op)==1 isnotthread-safe on free threaded builds; prefer this function.

The caller must hold anattached thread state, despite the factthat this function doesn’t call into the Python interpreter. This functioncannot fail.

Added in version 3.14.