Type Objects¶

Perhaps one of the most important structures of the Python object system is the structure that defines a new type: thePyTypeObjectstructure. Type objects can be handled using any of thePyObject_*or PyType_*functions, but do not offer much that’s interesting to most Python applications. These objects are fundamental to how objects behave, so they are very important to the interpreter itself and to any extension module that implements new types.

Type objects are fairly large compared to most of the standard types. The reason for the size is that each type object stores a large number of values, mostly C function pointers, each of which implements a small part of the type’s functionality. The fields of the type object are examined in detail in this section. The fields will be described in the order in which they occur in the structure.

In addition to the following quick reference, theExamples section provides at-a-glance insight into the meaning and use of PyTypeObject.

Quick Reference¶

“tp slots”¶

PyTypeObject Slot[1]	Type	special methods/attrs	Info[2]
PyTypeObject Slot[1]	Type	special methods/attrs	O	T	D	I
<R>`tp_name`	const char *	__name__	X	X
`tp_basicsize`	`Py_ssize_t`		X	X		X
`tp_itemsize`	`Py_ssize_t`			X		X
`tp_dealloc`	`destructor`		X	X		X
`tp_vectorcall_offset`	`Py_ssize_t`			X		X
(`tp_getattr`)	`getattrfunc`	__getattribute__, __getattr__				G
(`tp_setattr`)	`setattrfunc`	__setattr__, __delattr__				G
`tp_as_async`	`PyAsyncMethods`*	sub-slots				%
`tp_repr`	`reprfunc`	__repr__	X	X		X
`tp_as_number`	`PyNumberMethods`*	sub-slots				%
`tp_as_sequence`	`PySequenceMethods`*	sub-slots				%
`tp_as_mapping`	`PyMappingMethods`*	sub-slots				%
`tp_hash`	`hashfunc`	__hash__	X			G
`tp_call`	`ternaryfunc`	__call__		X		X
`tp_str`	`reprfunc`	__str__	X			X
`tp_getattro`	`getattrofunc`	__getattribute__, __getattr__	X	X		G
`tp_setattro`	`setattrofunc`	__setattr__, __delattr__	X	X		G
`tp_as_buffer`	`PyBufferProcs`*					%
`tp_flags`	unsigned long		X	X		?
`tp_doc`	const char *	__doc__	X	X
`tp_traverse`	`traverseproc`			X		G
`tp_clear`	`inquiry`			X		G
`tp_richcompare`	`richcmpfunc`	__lt__, __le__, __eq__, __ne__, __gt__, __ge__	X			G
(`tp_weaklistoffset`)	`Py_ssize_t`			X		?
`tp_iter`	`getiterfunc`	__iter__				X
`tp_iternext`	`iternextfunc`	__next__				X
`tp_methods`	`PyMethodDef`[]		X	X
`tp_members`	`PyMemberDef`[]			X
`tp_getset`	`PyGetSetDef`[]		X	X
`tp_base`	`PyTypeObject`*	__base__			X
`tp_dict`	`PyObject`*	__dict__			?
`tp_descr_get`	`descrgetfunc`	__get__				X
`tp_descr_set`	`descrsetfunc`	__set__, __delete__				X
(`tp_dictoffset`)	`Py_ssize_t`			X		?
`tp_init`	`initproc`	__init__	X	X		X
`tp_alloc`	`allocfunc`		X		?	?
`tp_new`	`newfunc`	__new__	X	X	?	?
`tp_free`	`freefunc`		X	X	?	?
`tp_is_gc`	`inquiry`			X		X
<`tp_bases`>	`PyObject`*	__bases__			~
<`tp_mro`>	`PyObject`*	__mro__			~
[`tp_cache`]	`PyObject`*
[`tp_subclasses`]	void *	__subclasses__
[`tp_weaklist`]	`PyObject`*
(`tp_del`)	`destructor`
[`tp_version_tag`]	unsigned int
`tp_finalize`	`destructor`	__del__				X
`tp_vectorcall`	`vectorcallfunc`
[`tp_watched`]	unsigned char

sub-slots¶

Slot	Type	special methods
`am_await`	`unaryfunc`	__await__
`am_aiter`	`unaryfunc`	__aiter__
`am_anext`	`unaryfunc`	__anext__
`am_send`	`sendfunc`

`nb_add`	`binaryfunc`	__add__ __radd__
`nb_inplace_add`	`binaryfunc`	__iadd__
`nb_subtract`	`binaryfunc`	__sub__ __rsub__
`nb_inplace_subtract`	`binaryfunc`	__isub__
`nb_multiply`	`binaryfunc`	__mul__ __rmul__
`nb_inplace_multiply`	`binaryfunc`	__imul__
`nb_remainder`	`binaryfunc`	__mod__ __rmod__
`nb_inplace_remainder`	`binaryfunc`	__imod__
`nb_divmod`	`binaryfunc`	__divmod__ __rdivmod__
`nb_power`	`ternaryfunc`	__pow__ __rpow__
`nb_inplace_power`	`ternaryfunc`	__ipow__
`nb_negative`	`unaryfunc`	__neg__
`nb_positive`	`unaryfunc`	__pos__
`nb_absolute`	`unaryfunc`	__abs__
`nb_bool`	`inquiry`	__bool__
`nb_invert`	`unaryfunc`	__invert__
`nb_lshift`	`binaryfunc`	__lshift__ __rlshift__
`nb_inplace_lshift`	`binaryfunc`	__ilshift__
`nb_rshift`	`binaryfunc`	__rshift__ __rrshift__
`nb_inplace_rshift`	`binaryfunc`	__irshift__
`nb_and`	`binaryfunc`	__and__ __rand__
`nb_inplace_and`	`binaryfunc`	__iand__
`nb_xor`	`binaryfunc`	__xor__ __rxor__
`nb_inplace_xor`	`binaryfunc`	__ixor__
`nb_or`	`binaryfunc`	__or__ __ror__
`nb_inplace_or`	`binaryfunc`	__ior__
`nb_int`	`unaryfunc`	__int__
`nb_reserved`	void *
`nb_float`	`unaryfunc`	__float__
`nb_floor_divide`	`binaryfunc`	__floordiv__
`nb_inplace_floor_divide`	`binaryfunc`	__ifloordiv__
`nb_true_divide`	`binaryfunc`	__truediv__
`nb_inplace_true_divide`	`binaryfunc`	__itruediv__
`nb_index`	`unaryfunc`	__index__
`nb_matrix_multiply`	`binaryfunc`	__matmul__ __rmatmul__
`nb_inplace_matrix_multiply`	`binaryfunc`	__imatmul__

`mp_length`	`lenfunc`	__len__
`mp_subscript`	`binaryfunc`	__getitem__
`mp_ass_subscript`	`objobjargproc`	__setitem__, __delitem__

`sq_length`	`lenfunc`	__len__
`sq_concat`	`binaryfunc`	__add__
`sq_repeat`	`ssizeargfunc`	__mul__
`sq_item`	`ssizeargfunc`	__getitem__
`sq_ass_item`	`ssizeobjargproc`	__setitem__ __delitem__
`sq_contains`	`objobjproc`	__contains__
`sq_inplace_concat`	`binaryfunc`	__iadd__
`sq_inplace_repeat`	`ssizeargfunc`	__imul__

`bf_getbuffer`	`getbufferproc()`
`bf_releasebuffer`	`releasebufferproc()`

slot typedefs¶

typedef	Parameter Types	Return Type
`allocfunc`	`PyTypeObject`* `Py_ssize_t`	`PyObject`*
`destructor`	`PyObject`*	void
`freefunc`	void *	void
`traverseproc`	`PyObject`* `visitproc` void *	int
`newfunc`	`PyObject`* `PyObject`* `PyObject`*	`PyObject`*
`initproc`	`PyObject`* `PyObject`* `PyObject`*	int
`reprfunc`	`PyObject`*	`PyObject`*
`getattrfunc`	`PyObject`* const char *	`PyObject`*
`setattrfunc`	`PyObject`* const char * `PyObject`*	int
`getattrofunc`	`PyObject`* `PyObject`*	`PyObject`*
`setattrofunc`	`PyObject`* `PyObject`* `PyObject`*	int
`descrgetfunc`	`PyObject`* `PyObject`* `PyObject`*	`PyObject`*
`descrsetfunc`	`PyObject`* `PyObject`* `PyObject`*	int
`hashfunc`	`PyObject`*	Py_hash_t
`richcmpfunc`	`PyObject`* `PyObject`* int	`PyObject`*
`getiterfunc`	`PyObject`*	`PyObject`*
`iternextfunc`	`PyObject`*	`PyObject`*
`lenfunc`	`PyObject`*	`Py_ssize_t`
`getbufferproc`	`PyObject`* `Py_buffer`* int	int
`releasebufferproc`	`PyObject`* `Py_buffer`*	void
`inquiry`	`PyObject`*	int
`unaryfunc`	`PyObject`*	`PyObject`*
`binaryfunc`	`PyObject`* `PyObject`*	`PyObject`*
`ternaryfunc`	`PyObject`* `PyObject`* `PyObject`*	`PyObject`*
`ssizeargfunc`	`PyObject`* `Py_ssize_t`	`PyObject`*
`ssizeobjargproc`	`PyObject`* `Py_ssize_t` `PyObject`*	int
`objobjproc`	`PyObject`* `PyObject`*	int
`objobjargproc`	`PyObject`* `PyObject`* `PyObject`*	int

SeeSlot Type typedefsbelow for more detail.

PyTypeObject Definition¶

The structure definition forPyTypeObjectcan be found in Include/object.h.For convenience of reference, this repeats the definition found there:

typedefstruct_typeobject{
PyObject_VAR_HEAD
constchar*tp_name;/* For printing, in format "<module>.<name>" */
Py_ssize_ttp_basicsize,tp_itemsize;/* For allocation */

/* Methods to implement standard operations */

destructortp_dealloc;
Py_ssize_ttp_vectorcall_offset;
getattrfunctp_getattr;
setattrfunctp_setattr;
PyAsyncMethods*tp_as_async;/* formerly known as tp_compare (Python 2)
or tp_reserved (Python 3) */
reprfunctp_repr;

/* Method suites for standard classes */

PyNumberMethods*tp_as_number;
PySequenceMethods*tp_as_sequence;
PyMappingMethods*tp_as_mapping;

/* More standard operations (here for binary compatibility) */

hashfunctp_hash;
ternaryfunctp_call;
reprfunctp_str;
getattrofunctp_getattro;
setattrofunctp_setattro;

/* Functions to access object as input/output buffer */
PyBufferProcs*tp_as_buffer;

/* Flags to define presence of optional/expanded features */
unsignedlongtp_flags;

constchar*tp_doc;/* Documentation string */

/* Assigned meaning in release 2.0 */
/* call function for all accessible objects */
traverseproctp_traverse;

/* delete references to contained objects */
inquirytp_clear;

/* Assigned meaning in release 2.1 */
/* rich comparisons */
richcmpfunctp_richcompare;

/* weak reference enabler */
Py_ssize_ttp_weaklistoffset;

/* Iterators */
getiterfunctp_iter;
iternextfunctp_iternext;

/* Attribute descriptor and subclassing stuff */
structPyMethodDef*tp_methods;
structPyMemberDef*tp_members;
structPyGetSetDef*tp_getset;
// Strong reference on a heap type, borrowed reference on a static type
struct_typeobject*tp_base;
PyObject*tp_dict;
descrgetfunctp_descr_get;
descrsetfunctp_descr_set;
Py_ssize_ttp_dictoffset;
initproctp_init;
allocfunctp_alloc;
newfunctp_new;
freefunctp_free;/* Low-level free-memory routine */
inquirytp_is_gc;/* For PyObject_IS_GC */
PyObject*tp_bases;
PyObject*tp_mro;/* method resolution order */
PyObject*tp_cache;
PyObject*tp_subclasses;
PyObject*tp_weaklist;
destructortp_del;

/* Type attribute cache version tag. Added in version 2.6 */
unsignedinttp_version_tag;

destructortp_finalize;
vectorcallfunctp_vectorcall;

/* bitset of which type-watchers care about this type */
unsignedchartp_watched;
}PyTypeObject;

PyObject Slots¶

The type object structure extends thePyVarObjectstructure. The ob_sizefield is used for dynamic types (created bytype_new(), usually called from a class statement). Note thatPyType_Type(the metatype) initializestp_itemsize,which means that its instances (i.e. type objects)musthave theob_sizefield.

Py_ssize_tPyObject.ob_refcnt¶

Part of theStable ABI.

This is the type object’s reference count, initialized to1by the PyObject_HEAD_INITmacro. Note that forstatically allocated type objects,the type’s instances (objects whoseob_type points back to the type) donotcount as references. But for dynamically allocated type objects,the instancesdo count as references.

Inheritance:

This field is not inherited by subtypes.

PyTypeObject*PyObject.ob_type¶

Part of theStable ABI.

This is the type’s type, in other words its metatype. It is initialized by the argument to thePyObject_HEAD_INITmacro, and its value should normally be &PyType_Type.However, for dynamically loadable extension modules that must be usable on Windows (at least), the compiler complains that this is not a valid initializer. Therefore, the convention is to passNULLto the PyObject_HEAD_INITmacro and to initialize this field explicitly at the start of the module’s initialization function, before doing anything else. This is typically done like this:

Foo_Type.ob_type=&PyType_Type;

This should be done before any instances of the type are created. PyType_Ready()checks ifob_typeisNULL,and if so, initializes it to theob_typefield of the base class. PyType_Ready()will not change this field if it is non-zero.

Inheritance:

This field is inherited by subtypes.

PyObject*PyObject._ob_next¶

PyObject*PyObject._ob_prev¶

These fields are only present when the macroPy_TRACE_REFSis defined (see theconfigure--with-trace-refsoption).

Their initialization toNULLis taken care of by the PyObject_HEAD_INITmacro. Forstatically allocated objects,these fields always remainNULL.Fordynamically allocated objects,these two fields are used to link the object into a doubly linked list ofalllive objects on the heap.

This could be used for various debugging purposes; currently the only uses are thesys.getobjects()function and to print the objects that are still alive at the end of a run when the environment variable PYTHONDUMPREFSis set.

Inheritance:

These fields are not inherited by subtypes.

PyVarObject Slots¶

Py_ssize_tPyVarObject.ob_size¶

Part of theStable ABI.

Forstatically allocated type objects,this should be initialized to zero. Fordynamically allocated type objects,this field has a special internal meaning.

Inheritance:

This field is not inherited by subtypes.

PyTypeObject Slots¶

Each slot has a section describing inheritance. IfPyType_Ready() may set a value when the field is set toNULLthen there will also be a “Default” section. (Note that many fields set onPyBaseObject_Type andPyType_Typeeffectively act as defaults.)

constchar*PyTypeObject.tp_name¶

Pointer to a NUL-terminated string containing the name of the type. For types that are accessible as module globals, the string should be the full module name, followed by a dot, followed by the type name; for built-in types, it should be just the type name. If the module is a submodule of a package, the full package name is part of the full module name. For example, a type named Tdefined in moduleMin subpackageQin packageP should have thetp_nameinitializer"P.Q.M.T".

Fordynamically allocated type objects, this should just be the type name, and the module name explicitly stored in the type dict as the value for key '__module__'.

Forstatically allocated type objects, thetp_namefield should contain a dot. Everything before the last dot is made accessible as the__module__ attribute, and everything after the last dot is made accessible as the __name__attribute.

If no dot is present, the entiretp_namefield is made accessible as the __name__attribute, and the__module__attribute is undefined (unless explicitly set in the dictionary, as explained above). This means your type will be impossible to pickle. Additionally, it will not be listed in module documentations created with pydoc.

This field must not beNULL.It is the only required field inPyTypeObject()(other than potentially tp_itemsize).

Inheritance:

This field is not inherited by subtypes.

Py_ssize_tPyTypeObject.tp_basicsize¶

Py_ssize_tPyTypeObject.tp_itemsize¶

These fields allow calculating the size in bytes of instances of the type.

There are two kinds of types: types with fixed-length instances have a zero tp_itemsizefield, types with variable-length instances have a non-zero tp_itemsizefield. For a type with fixed-length instances, all instances have the same size, given intp_basicsize.

For a type with variable-length instances, the instances must have an ob_sizefield, and the instance size istp_basicsizeplus N timestp_itemsize,where N is the “length” of the object. The value of N is typically stored in the instance’sob_sizefield. There are exceptions: for example, ints use a negativeob_sizeto indicate a negative number, and N isabs(ob_size)there. Also, the presence of an ob_sizefield in the instance layout doesn’t mean that the instance structure is variable-length (for example, the structure for the list type has fixed-length instances, yet those instances have a meaningfulob_size field).

The basic size includes the fields in the instance declared by the macro PyObject_HEADorPyObject_VAR_HEAD(whichever is used to declare the instance struct) and this in turn includes the_ob_prevand _ob_nextfields if they are present. This means that the only correct way to get an initializer for thetp_basicsizeis to use the sizeofoperator on the struct used to declare the instance layout. The basic size does not include the GC header size.

A note about alignment: if the variable items require a particular alignment, this should be taken care of by the value oftp_basicsize.Example: suppose a type implements an array ofdouble.tp_itemsizeis sizeof(double).It is the programmer’s responsibility that tp_basicsizeis a multiple ofsizeof(double)(assuming this is the alignment requirement fordouble).

For any type with variable-length instances, this field must not beNULL.

Inheritance:

These fields are inherited separately by subtypes. If the base type has a non-zerotp_itemsize,it is generally not safe to set tp_itemsizeto a different non-zero value in a subtype (though this depends on the implementation of the base type).

destructorPyTypeObject.tp_dealloc¶

A pointer to the instance destructor function. This function must be defined unless the type guarantees that its instances will never be deallocated (as is the case for the singletonsNoneandEllipsis). The function signature is:

voidtp_dealloc(PyObject*self);

The destructor function is called by thePy_DECREF()and Py_XDECREF()macros when the new reference count is zero. At this point, the instance is still in existence, but there are no references to it. The destructor function should free all references which the instance owns, free all memory buffers owned by the instance (using the freeing function corresponding to the allocation function used to allocate the buffer), and call the type’s tp_freefunction. If the type is not subtypable (doesn’t have thePy_TPFLAGS_BASETYPEflag bit set), it is permissible to call the object deallocator directly instead of via tp_free.The object deallocator should be the one used to allocate the instance; this is normallyPyObject_Del()if the instance was allocated usingPyObject_NeworPyObject_NewVar,or PyObject_GC_Del()if the instance was allocated using PyObject_GC_NeworPyObject_GC_NewVar.

If the type supports garbage collection (has thePy_TPFLAGS_HAVE_GC flag bit set), the destructor should callPyObject_GC_UnTrack() before clearing any member fields.

staticvoidfoo_dealloc(foo_object*self){
PyObject_GC_UnTrack(self);
Py_CLEAR(self->ref);
Py_TYPE(self)->tp_free((PyObject*)self);
}

Finally, if the type is heap allocated (Py_TPFLAGS_HEAPTYPE), the deallocator should release the owned reference to its type object (viaPy_DECREF()) after calling the type deallocator. In order to avoid dangling pointers, the recommended way to achieve this is:

staticvoidfoo_dealloc(foo_object*self){
PyTypeObject*tp=Py_TYPE(self);
// free references and buffers here
tp->tp_free(self);
Py_DECREF(tp);
}

Inheritance:

This field is inherited by subtypes.

Py_ssize_tPyTypeObject.tp_vectorcall_offset¶

An optional offset to a per-instance function that implements calling the object using thevectorcall protocol, a more efficient alternative of the simplertp_call.

This field is only used if the flagPy_TPFLAGS_HAVE_VECTORCALL is set. If so, this must be a positive integer containing the offset in the instance of avectorcallfuncpointer.

Thevectorcallfuncpointer may beNULL,in which case the instance behaves as ifPy_TPFLAGS_HAVE_VECTORCALLwas not set: calling the instance falls back totp_call.

Any class that setsPy_TPFLAGS_HAVE_VECTORCALLmust also set tp_calland make sure its behaviour is consistent with thevectorcallfuncfunction. This can be done by settingtp_calltoPyVectorcall_Call().

Changed in version 3.8:Before version 3.8, this slot was namedtp_print. In Python 2.x, it was used for printing to a file. In Python 3.0 to 3.7, it was unused.

Changed in version 3.12:Before version 3.12, it was not recommended for mutable heap typesto implement the vectorcall protocol. When a user sets__call__in Python code, onlytp_callis updated, likely making it inconsistent with the vectorcall function. Since 3.12, setting__call__will disable vectorcall optimization by clearing thePy_TPFLAGS_HAVE_VECTORCALLflag.

Inheritance:

This field is always inherited. However, thePy_TPFLAGS_HAVE_VECTORCALLflag is not always inherited. If it’s not set, then the subclass won’t use vectorcall,except when PyVectorcall_Call()is explicitly called.

getattrfuncPyTypeObject.tp_getattr¶

An optional pointer to the get-attribute-string function.

This field is deprecated. When it is defined, it should point to a function that acts the same as thetp_getattrofunction, but taking a C string instead of a Python string object to give the attribute name.

Inheritance:

Group:tp_getattr,tp_getattro

This field is inherited by subtypes together withtp_getattro:a subtype inherits bothtp_getattrandtp_getattrofrom its base type when the subtype’stp_getattrandtp_getattroare bothNULL.

setattrfuncPyTypeObject.tp_setattr¶

An optional pointer to the function for setting and deleting attributes.

This field is deprecated. When it is defined, it should point to a function that acts the same as thetp_setattrofunction, but taking a C string instead of a Python string object to give the attribute name.

Inheritance:

Group:tp_setattr,tp_setattro

This field is inherited by subtypes together withtp_setattro:a subtype inherits bothtp_setattrandtp_setattrofrom its base type when the subtype’stp_setattrandtp_setattroare bothNULL.

PyAsyncMethods*PyTypeObject.tp_as_async¶

Pointer to an additional structure that contains fields relevant only to objects which implementawaitableandasynchronous iterator protocols at the C-level. SeeAsync Object Structuresfor details.

Added in version 3.5:Formerly known astp_compareandtp_reserved.

Inheritance:

Thetp_as_asyncfield is not inherited, but the contained fields are inherited individually.

reprfuncPyTypeObject.tp_repr¶

An optional pointer to a function that implements the built-in function repr().

The signature is the same as forPyObject_Repr():

PyObject*tp_repr(PyObject*self);

The function must return a string or a Unicode object. Ideally, this function should return a string that, when passed to eval(),given a suitable environment, returns an object with the same value. If this is not feasible, it should return a string starting with '<'and ending with'>'from which both the type and the value of the object can be deduced.

Inheritance:

This field is inherited by subtypes.

Default:

When this field is not set, a string of the form<%sobjectat%p>is returned, where%sis replaced by the type name, and%pby the object’s memory address.

PyNumberMethods*PyTypeObject.tp_as_number¶

Pointer to an additional structure that contains fields relevant only to objects which implement the number protocol. These fields are documented in Number Object Structures.

Inheritance:

Thetp_as_numberfield is not inherited, but the contained fields are inherited individually.

PySequenceMethods*PyTypeObject.tp_as_sequence¶

Pointer to an additional structure that contains fields relevant only to objects which implement the sequence protocol. These fields are documented inSequence Object Structures.

Inheritance:

Thetp_as_sequencefield is not inherited, but the contained fields are inherited individually.

PyMappingMethods*PyTypeObject.tp_as_mapping¶

Pointer to an additional structure that contains fields relevant only to objects which implement the mapping protocol. These fields are documented in Mapping Object Structures.

Inheritance:

Thetp_as_mappingfield is not inherited, but the contained fields are inherited individually.

hashfuncPyTypeObject.tp_hash¶

An optional pointer to a function that implements the built-in function hash().

The signature is the same as forPyObject_Hash():

Py_hash_ttp_hash(PyObject*);

The value-1should not be returned as a normal return value; when an error occurs during the computation of the hash value, the function should set an exception and return-1.

When this field is not set (andtp_richcompareis not set), an attempt to take the hash of the object raisesTypeError. This is the same as setting it toPyObject_HashNotImplemented().

This field can be set explicitly toPyObject_HashNotImplemented()to block inheritance of the hash method from a parent type. This is interpreted as the equivalent of__hash__=Noneat the Python level, causing isinstance(o,collections.Hashable)to correctly returnFalse.Note that the converse is also true - setting__hash__=Noneon a class at the Python level will result in thetp_hashslot being set to PyObject_HashNotImplemented().

Inheritance:

Group:tp_hash,tp_richcompare

This field is inherited by subtypes together with tp_richcompare:a subtype inherits both of tp_richcompareandtp_hash,when the subtype’s tp_richcompareandtp_hashare bothNULL.

ternaryfuncPyTypeObject.tp_call¶

An optional pointer to a function that implements calling the object. This should beNULLif the object is not callable. The signature is the same as forPyObject_Call():

PyObject*tp_call(PyObject*self,PyObject*args,PyObject*kwargs);

Inheritance:

This field is inherited by subtypes.

reprfuncPyTypeObject.tp_str¶

An optional pointer to a function that implements the built-in operation str().(Note thatstris a type now, andstr()calls the constructor for that type. This constructor callsPyObject_Str()to do the actual work, andPyObject_Str()will call this handler.)

The signature is the same as forPyObject_Str():

PyObject*tp_str(PyObject*self);

The function must return a string or a Unicode object. It should be a “friendly” string representation of the object, as this is the representation that will be used, among other things, by theprint()function.

Inheritance:

This field is inherited by subtypes.

Default:

When this field is not set,PyObject_Repr()is called to return a string representation.

getattrofuncPyTypeObject.tp_getattro¶

An optional pointer to the get-attribute function.

The signature is the same as forPyObject_GetAttr():

PyObject*tp_getattro(PyObject*self,PyObject*attr);

It is usually convenient to set this field toPyObject_GenericGetAttr(), which implements the normal way of looking for object attributes.

Inheritance:

Group:tp_getattr,tp_getattro

This field is inherited by subtypes together withtp_getattr:a subtype inherits bothtp_getattrandtp_getattrofrom its base type when the subtype’stp_getattrandtp_getattroare bothNULL.

Default:

PyBaseObject_TypeusesPyObject_GenericGetAttr().

setattrofuncPyTypeObject.tp_setattro¶

An optional pointer to the function for setting and deleting attributes.

The signature is the same as forPyObject_SetAttr():

inttp_setattro(PyObject*self,PyObject*attr,PyObject*value);

In addition, settingvaluetoNULLto delete an attribute must be supported. It is usually convenient to set this field to PyObject_GenericSetAttr(),which implements the normal way of setting object attributes.

Inheritance:

Group:tp_setattr,tp_setattro

This field is inherited by subtypes together withtp_setattr:a subtype inherits bothtp_setattrandtp_setattrofrom its base type when the subtype’stp_setattrandtp_setattroare bothNULL.

Default:

PyBaseObject_TypeusesPyObject_GenericSetAttr().

PyBufferProcs*PyTypeObject.tp_as_buffer¶

Pointer to an additional structure that contains fields relevant only to objects which implement the buffer interface. These fields are documented in Buffer Object Structures.

Inheritance:

Thetp_as_bufferfield is not inherited, but the contained fields are inherited individually.

unsignedlongPyTypeObject.tp_flags¶

This field is a bit mask of various flags. Some flags indicate variant semantics for certain situations; others are used to indicate that certain fields in the type object (or in the extension structures referenced via tp_as_number,tp_as_sequence,tp_as_mapping,and tp_as_buffer) that were historically not always present are valid; if such a flag bit is clear, the type fields it guards must not be accessed and must be considered to have a zero orNULLvalue instead.

Inheritance:

Inheritance of this field is complicated. Most flag bits are inherited individually, i.e. if the base type has a flag bit set, the subtype inherits this flag bit. The flag bits that pertain to extension structures are strictly inherited if the extension structure is inherited, i.e. the base type’s value of the flag bit is copied into the subtype together with a pointer to the extension structure. ThePy_TPFLAGS_HAVE_GCflag bit is inherited together with thetp_traverseandtp_clearfields, i.e. if the Py_TPFLAGS_HAVE_GCflag bit is clear in the subtype and the tp_traverseandtp_clearfields in the subtype exist and have NULLvalues. .. XXX are most flag bitsreallyinherited individually?

Default:

PyBaseObject_Typeuses Py_TPFLAGS_DEFAULT|Py_TPFLAGS_BASETYPE.

Bit Masks:

The following bit masks are currently defined; these can be ORed together using the|operator to form the value of thetp_flagsfield. The macro PyType_HasFeature()takes a type and a flags value,tpandf,and checks whethertp->tp_flags&fis non-zero.

Py_TPFLAGS_HEAPTYPE¶

This bit is set when the type object itself is allocated on the heap, for example, types created dynamically usingPyType_FromSpec().In this case, theob_typefield of its instances is considered a reference to the type, and the type object is INCREF’ed when a new instance is created, and DECREF’ed when an instance is destroyed (this does not apply to instances of subtypes; only the type referenced by the instance’s ob_type gets INCREF’ed or DECREF’ed). Heap types should alsosupport garbage collection as they can form a reference cycle with their own module object.

Inheritance:

???

Py_TPFLAGS_BASETYPE¶

This bit is set when the type can be used as the base type of another type. If this bit is clear, the type cannot be subtyped (similar to a “final” class in Java).

Inheritance:

???

Py_TPFLAGS_READY¶

This bit is set when the type object has been fully initialized by PyType_Ready().

Inheritance:

???

Py_TPFLAGS_READYING¶

This bit is set whilePyType_Ready()is in the process of initializing the type object.

Inheritance:

???

Py_TPFLAGS_HAVE_GC¶

This bit is set when the object supports garbage collection. If this bit is set, instances must be created usingPyObject_GC_Newand destroyed usingPyObject_GC_Del().More information in section Supporting Cyclic Garbage Collection.This bit also implies that the GC-related fieldstp_traverseandtp_clearare present in the type object.

Inheritance:

Group:Py_TPFLAGS_HAVE_GC,tp_traverse,tp_clear

ThePy_TPFLAGS_HAVE_GCflag bit is inherited together with thetp_traverseandtp_clear fields, i.e. if thePy_TPFLAGS_HAVE_GCflag bit is clear in the subtype and thetp_traverseand tp_clearfields in the subtype exist and haveNULL values.

Py_TPFLAGS_DEFAULT¶

This is a bitmask of all the bits that pertain to the existence of certain fields in the type object and its extension structures. Currently, it includes the following bits:Py_TPFLAGS_HAVE_STACKLESS_EXTENSION.

Inheritance:

???

Py_TPFLAGS_METHOD_DESCRIPTOR¶

This bit indicates that objects behave like unbound methods.

If this flag is set fortype(meth),then:

meth.__get__(obj,cls)(*args,**kwds)(withobjnot None) must be equivalent tometh(obj,*args,**kwds).
meth.__get__(None,cls)(*args,**kwds) must be equivalent tometh(*args,**kwds).

This flag enables an optimization for typical method calls like obj.meth():it avoids creating a temporary “bound method” object for obj.meth.

Added in version 3.8.

Inheritance:

This flag is never inherited by types without the Py_TPFLAGS_IMMUTABLETYPEflag set. For extension types, it is inherited whenevertp_descr_getis inherited.

Py_TPFLAGS_MANAGED_DICT¶

This bit indicates that instances of the class have a__dict__ attribute, and that the space for the dictionary is managed by the VM.

If this flag is set,Py_TPFLAGS_HAVE_GCshould also be set.

Added in version 3.12.

Inheritance:

This flag is inherited unless the tp_dictoffsetfield is set in a superclass.

Py_TPFLAGS_MANAGED_WEAKREF¶

This bit indicates that instances of the class should be weakly referenceable.

Added in version 3.12.

Inheritance:

This flag is inherited unless the tp_weaklistoffsetfield is set in a superclass.

Py_TPFLAGS_ITEMS_AT_END¶

Only usable with variable-size types, i.e. ones with non-zero tp_itemsize.

Indicates that the variable-sized portion of an instance of this type is at the end of the instance’s memory area, at an offset of Py_TYPE(obj)->tp_basicsize(which may be different in each subclass).

When setting this flag, be sure that all superclasses either use this memory layout, or are not variable-sized. Python does not check this.

Added in version 3.12.

Inheritance:

This flag is inherited.

Py_TPFLAGS_LONG_SUBCLASS¶

Py_TPFLAGS_LIST_SUBCLASS¶

Py_TPFLAGS_TUPLE_SUBCLASS¶

Py_TPFLAGS_BYTES_SUBCLASS¶

Py_TPFLAGS_UNICODE_SUBCLASS¶

Py_TPFLAGS_DICT_SUBCLASS¶

Py_TPFLAGS_BASE_EXC_SUBCLASS¶

Py_TPFLAGS_TYPE_SUBCLASS¶: These flags are used by functions such as PyLong_Check()to quickly determine if a type is a subclass of a built-in type; such specific checks are faster than a generic check, likePyObject_IsInstance().Custom types that inherit from built-ins should have theirtp_flags set appropriately, or the code that interacts with such types will behave differently depending on what kind of check is used.

Py_TPFLAGS_HAVE_FINALIZE¶: This bit is set when thetp_finalizeslot is present in the type structure.

Added in version 3.4.

Deprecated since version 3.8:This flag isn’t necessary anymore, as the interpreter assumes the tp_finalizeslot is always present in the type structure.

Py_TPFLAGS_HAVE_VECTORCALL¶

This bit is set when the class implements thevectorcall protocol. Seetp_vectorcall_offsetfor details.

Inheritance:

This bit is inherited iftp_callis also inherited.

Added in version 3.9.

Changed in version 3.12:This flag is now removed from a class when the class’s __call__()method is reassigned.

This flag can now be inherited by mutable classes.

Py_TPFLAGS_IMMUTABLETYPE¶

This bit is set for type objects that are immutable: type attributes cannot be set nor deleted.

PyType_Ready()automatically applies this flag to static types.

Inheritance:

This flag is not inherited.

Added in version 3.10.

Py_TPFLAGS_DISALLOW_INSTANTIATION¶

Disallow creating instances of the type: set tp_newto NULL and don’t create the__new__ key in the type dictionary.

The flag must be set before creating the type, not after. For example, it must be set beforePyType_Ready()is called on the type.

The flag is set automatically onstatic typesif tp_baseis NULL or&PyBaseObject_Typeand tp_newis NULL.

Inheritance:

This flag is not inherited. However, subclasses will not be instantiable unless they provide a non-NULLtp_new(which is only possible via the C API).

Note

To disallow instantiating a class directly but allow instantiating its subclasses (e.g. for anabstract base class), do not use this flag. Instead, maketp_newonly succeed for subclasses.

Added in version 3.10.

Py_TPFLAGS_MAPPING¶

This bit indicates that instances of the class may match mapping patterns when used as the subject of amatchblock. It is automatically set when registering or subclassingcollections.abc.Mapping,and unset when registeringcollections.abc.Sequence.

Note

Py_TPFLAGS_MAPPINGandPy_TPFLAGS_SEQUENCEare mutually exclusive; it is an error to enable both flags simultaneously.

Inheritance:

This flag is inherited by types that do not already set Py_TPFLAGS_SEQUENCE.

See also

PEP 634– Structural Pattern Matching: Specification

Added in version 3.10.

Py_TPFLAGS_VALID_VERSION_TAG¶: Internal. Do not set or unset this flag. To indicate that a class has changed callPyType_Modified()

Warning

This flag is present in header files, but is an internal feature and should not be used. It will be removed in a future version of CPython

constchar*PyTypeObject.tp_doc¶

An optional pointer to a NUL-terminated C string giving the docstring for this type object. This is exposed as the__doc__attribute on the type and instances of the type.

Inheritance:

This field isnotinherited by subtypes.

traverseprocPyTypeObject.tp_traverse¶

An optional pointer to a traversal function for the garbage collector. This is only used if thePy_TPFLAGS_HAVE_GCflag bit is set. The signature is:

inttp_traverse(PyObject*self,visitprocvisit,void*arg);

More information about Python’s garbage collection scheme can be found in sectionSupporting Cyclic Garbage Collection.

Thetp_traversepointer is used by the garbage collector to detect reference cycles. A typical implementation of atp_traversefunction simply callsPy_VISIT()on each of the instance’s members that are Python objects that the instance owns. For example, this is functionlocal_traverse()from the _threadextension module:

staticint
local_traverse(localobject*self,visitprocvisit,void*arg)
{
Py_VISIT(self->args);
Py_VISIT(self->kw);
Py_VISIT(self->dict);
return0;
}

Note thatPy_VISIT()is called only on those members that can participate in reference cycles. Although there is also aself->keymember, it can only beNULLor a Python string and therefore cannot be part of a reference cycle.

On the other hand, even if you know a member can never be part of a cycle, as a debugging aid you may want to visit it anyway just so thegcmodule’s get_referents()function will include it.

Warning

When implementingtp_traverse,only the members that the instanceowns(by havingstrong referencesto them) must be visited. For instance, if an object supports weak references via the tp_weaklistslot, the pointer supporting the linked list (whattp_weaklistpoints to) mustnotbe visited as the instance does not directly own the weak references to itself (the weakreference list is there to support the weak reference machinery, but the instance has no strong reference to the elements inside it, as they are allowed to be removed even if the instance is still alive).

Note thatPy_VISIT()requires thevisitandargparameters to local_traverse()to have these specific names; don’t name them just anything.

Instances ofheap-allocated typeshold a reference to their type. Their traversal function must therefore either visit Py_TYPE(self),or delegate this responsibility by callingtp_traverseof another heap-allocated type (such as a heap-allocated superclass). If they do not, the type object may not be garbage-collected.

Changed in version 3.9:Heap-allocated types are expected to visitPy_TYPE(self)in tp_traverse.In earlier versions of Python, due to bug 40217,doing this may lead to crashes in subclasses.

Inheritance:

Group:Py_TPFLAGS_HAVE_GC,tp_traverse,tp_clear

This field is inherited by subtypes together withtp_clearand the Py_TPFLAGS_HAVE_GCflag bit: the flag bit,tp_traverse,and tp_clearare all inherited from the base type if they are all zero in the subtype.

inquiryPyTypeObject.tp_clear¶

An optional pointer to a clear function for the garbage collector. This is only used if thePy_TPFLAGS_HAVE_GCflag bit is set. The signature is:

inttp_clear(PyObject*);

Thetp_clearmember function is used to break reference cycles in cyclic garbage detected by the garbage collector. Taken together, alltp_clear functions in the system must combine to break all reference cycles. This is subtle, and if in any doubt supply atp_clearfunction. For example, the tuple type does not implement atp_clearfunction, because it’s possible to prove that no reference cycle can be composed entirely of tuples. Therefore thetp_clearfunctions of other types must be sufficient to break any cycle containing a tuple. This isn’t immediately obvious, and there’s rarely a good reason to avoid implementingtp_clear.

Implementations oftp_clearshould drop the instance’s references to those of its members that may be Python objects, and set its pointers to those members toNULL,as in the following example:

staticint
local_clear(localobject*self)
{
Py_CLEAR(self->key);
Py_CLEAR(self->args);
Py_CLEAR(self->kw);
Py_CLEAR(self->dict);
return0;
}

ThePy_CLEAR()macro should be used, because clearing references is delicate: the reference to the contained object must not be released (viaPy_DECREF()) until after the pointer to the contained object is set toNULL.This is because releasing the reference may cause the contained object to become trash, triggering a chain of reclamation activity that may include invoking arbitrary Python code (due to finalizers, or weakref callbacks, associated with the contained object). If it’s possible for such code to referenceselfagain, it’s important that the pointer to the contained object beNULLat that time, so thatselfknows the contained object can no longer be used. The Py_CLEAR()macro performs the operations in a safe order.

Note thattp_clearis notalwayscalled before an instance is deallocated. For example, when reference counting is enough to determine that an object is no longer used, the cyclic garbage collector is not involved andtp_deallocis called directly.

Because the goal oftp_clearfunctions is to break reference cycles, it’s not necessary to clear contained objects like Python strings or Python integers, which can’t participate in reference cycles. On the other hand, it may be convenient to clear all contained Python objects, and write the type’s tp_deallocfunction to invoketp_clear.

More information about Python’s garbage collection scheme can be found in sectionSupporting Cyclic Garbage Collection.

Inheritance:

Group:Py_TPFLAGS_HAVE_GC,tp_traverse,tp_clear

This field is inherited by subtypes together withtp_traverseand the Py_TPFLAGS_HAVE_GCflag bit: the flag bit,tp_traverse,and tp_clearare all inherited from the base type if they are all zero in the subtype.

richcmpfuncPyTypeObject.tp_richcompare¶

An optional pointer to the rich comparison function, whose signature is:

PyObject*tp_richcompare(PyObject*self,PyObject*other,intop);

The first parameter is guaranteed to be an instance of the type that is defined byPyTypeObject.

The function should return the result of the comparison (usuallyPy_True orPy_False). If the comparison is undefined, it must return Py_NotImplemented,if another error occurred it must returnNULLand set an exception condition.

The following constants are defined to be used as the third argument for tp_richcompareand forPyObject_RichCompare():

Constant	Comparison
Py_LT¶	`<`
Py_LE¶	`<=`
Py_EQ¶	`==`
Py_NE¶	`!=`
Py_GT¶	`>`
Py_GE¶	`>=`

The following macro is defined to ease writing rich comparison functions:

Py_RETURN_RICHCOMPARE(VAL_A,VAL_B,op)¶

ReturnPy_TrueorPy_Falsefrom the function, depending on the result of a comparison. VAL_A and VAL_B must be orderable by C comparison operators (for example, they may be C ints or floats). The third argument specifies the requested operation, as forPyObject_RichCompare().

The returned value is a newstrong reference.

On error, sets an exception and returnsNULLfrom the function.

Added in version 3.7.

Inheritance:

Group:tp_hash,tp_richcompare

This field is inherited by subtypes together withtp_hash: a subtype inheritstp_richcompareandtp_hashwhen the subtype’stp_richcompareandtp_hashare both NULL.

Default:

PyBaseObject_Typeprovides atp_richcompare implementation, which may be inherited. However, if only tp_hashis defined, not even the inherited function is used and instances of the type will not be able to participate in any comparisons.

Py_ssize_tPyTypeObject.tp_weaklistoffset¶

While this field is still supported,Py_TPFLAGS_MANAGED_WEAKREF should be used instead, if at all possible.

If the instances of this type are weakly referenceable, this field is greater than zero and contains the offset in the instance structure of the weak reference list head (ignoring the GC header, if present); this offset is used by PyObject_ClearWeakRefs()and thePyWeakref_*functions. The instance structure needs to include a field of typePyObject*which is initialized toNULL.

Do not confuse this field withtp_weaklist;that is the list head for weak references to the type object itself.

It is an error to set both thePy_TPFLAGS_MANAGED_WEAKREFbit and tp_weaklistoffset.

Inheritance:

This field is inherited by subtypes, but see the rules listed below. A subtype may override this offset; this means that the subtype uses a different weak reference list head than the base type. Since the list head is always found via tp_weaklistoffset,this should not be a problem.

Default:

If thePy_TPFLAGS_MANAGED_WEAKREFbit is set in the tp_flagsfield, then tp_weaklistoffsetwill be set to a negative value, to indicate that it is unsafe to use this field.

getiterfuncPyTypeObject.tp_iter¶

An optional pointer to a function that returns aniteratorfor the object. Its presence normally signals that the instances of this type are iterable(although sequences may be iterable without this function).

This function has the same signature asPyObject_GetIter():

PyObject*tp_iter(PyObject*self);

Inheritance:

This field is inherited by subtypes.

iternextfuncPyTypeObject.tp_iternext¶

An optional pointer to a function that returns the next item in an iterator.The signature is:

PyObject*tp_iternext(PyObject*self);

When the iterator is exhausted, it must returnNULL;aStopIteration exception may or may not be set. When another error occurs, it must return NULLtoo. Its presence signals that the instances of this type are iterators.

Iterator types should also define thetp_iterfunction, and that function should return the iterator instance itself (not a new iterator instance).

This function has the same signature asPyIter_Next().

Inheritance:

This field is inherited by subtypes.

structPyMethodDef*PyTypeObject.tp_methods¶

An optional pointer to a staticNULL-terminated array ofPyMethodDef structures, declaring regular methods of this type.

For each entry in the array, an entry is added to the type’s dictionary (see tp_dictbelow) containing a method descriptor.

Inheritance:

This field is not inherited by subtypes (methods are inherited through a different mechanism).

structPyMemberDef*PyTypeObject.tp_members¶

An optional pointer to a staticNULL-terminated array ofPyMemberDef structures, declaring regular data members (fields or slots) of instances of this type.

For each entry in the array, an entry is added to the type’s dictionary (see tp_dictbelow) containing a member descriptor.

Inheritance:

This field is not inherited by subtypes (members are inherited through a different mechanism).

structPyGetSetDef*PyTypeObject.tp_getset¶

An optional pointer to a staticNULL-terminated array ofPyGetSetDef structures, declaring computed attributes of instances of this type.

For each entry in the array, an entry is added to the type’s dictionary (see tp_dictbelow) containing a getset descriptor.

Inheritance:

This field is not inherited by subtypes (computed attributes are inherited through a different mechanism).

PyTypeObject*PyTypeObject.tp_base¶

An optional pointer to a base type from which type properties are inherited. At this level, only single inheritance is supported; multiple inheritance require dynamically creating a type object by calling the metatype.

Note

Slot initialization is subject to the rules of initializing globals. C99 requires the initializers to be “address constants”. Function designators likePyType_GenericNew(),with implicit conversion to a pointer, are valid C99 address constants.

However, the unary ‘&’ operator applied to a non-static variable likePyBaseObject_Typeis not required to produce an address constant. Compilers may support this (gcc does), MSVC does not. Both compilers are strictly standard conforming in this particular behavior.

Consequently,tp_baseshould be set in the extension module’s init function.

Inheritance:

This field is not inherited by subtypes (obviously).

Default:

This field defaults to&PyBaseObject_Type(which to Python programmers is known as the typeobject).

PyObject*PyTypeObject.tp_dict¶

The type’s dictionary is stored here byPyType_Ready().

This field should normally be initialized toNULLbefore PyType_Ready is called; it may also be initialized to a dictionary containing initial attributes for the type. OncePyType_Ready()has initialized the type, extra attributes for the type may be added to this dictionary only if they don’t correspond to overloaded operations (like__add__()). Once initialization for the type has finished, this field should be treated as read-only.

Some types may not store their dictionary in this slot. UsePyType_GetDict()to retrieve the dictionary for an arbitrary type.

Changed in version 3.12:Internals detail: For static builtin types, this is alwaysNULL. Instead, the dict for such types is stored onPyInterpreterState. UsePyType_GetDict()to get the dict for an arbitrary type.

Inheritance:

This field is not inherited by subtypes (though the attributes defined in here are inherited through a different mechanism).

Default:

If this field isNULL,PyType_Ready()will assign a new dictionary to it.

Warning

It is not safe to usePyDict_SetItem()on or otherwise modify tp_dictwith the dictionary C-API.

descrgetfuncPyTypeObject.tp_descr_get¶

An optional pointer to a “descriptor get” function.

The function signature is:

PyObject*tp_descr_get(PyObject*self,PyObject*obj,PyObject*type);

Inheritance:

This field is inherited by subtypes.

descrsetfuncPyTypeObject.tp_descr_set¶

An optional pointer to a function for setting and deleting a descriptor’s value.

The function signature is:

inttp_descr_set(PyObject*self,PyObject*obj,PyObject*value);

Thevalueargument is set toNULLto delete the value.

Inheritance:

This field is inherited by subtypes.

Py_ssize_tPyTypeObject.tp_dictoffset¶

While this field is still supported,Py_TPFLAGS_MANAGED_DICTshould be used instead, if at all possible.

If the instances of this type have a dictionary containing instance variables, this field is non-zero and contains the offset in the instances of the type of the instance variable dictionary; this offset is used by PyObject_GenericGetAttr().

Do not confuse this field withtp_dict;that is the dictionary for attributes of the type object itself.

The value specifies the offset of the dictionary from the start of the instance structure.

Thetp_dictoffsetshould be regarded as write-only. To get the pointer to the dictionary callPyObject_GenericGetDict(). CallingPyObject_GenericGetDict()may need to allocate memory for the dictionary, so it is may be more efficient to callPyObject_GetAttr() when accessing an attribute on the object.

It is an error to set both thePy_TPFLAGS_MANAGED_WEAKREFbit and tp_dictoffset.

Inheritance:

This field is inherited by subtypes. A subtype should not override this offset; doing so could be unsafe, if C code tries to access the dictionary at the previous offset. To properly support inheritance, usePy_TPFLAGS_MANAGED_DICT.

Default:

This slot has no default. Forstatic types,if the field isNULLthen no__dict__gets created for instances.

If thePy_TPFLAGS_MANAGED_DICTbit is set in the tp_dictfield, then tp_dictoffsetwill be set to-1,to indicate that it is unsafe to use this field.

initprocPyTypeObject.tp_init¶

An optional pointer to an instance initialization function.

This function corresponds to the__init__()method of classes. Like __init__(),it is possible to create an instance without calling __init__(),and it is possible to reinitialize an instance by calling its __init__()method again.

The function signature is:

inttp_init(PyObject*self,PyObject*args,PyObject*kwds);

The self argument is the instance to be initialized; theargsandkwds arguments represent positional and keyword arguments of the call to __init__().

Thetp_initfunction, if notNULL,is called when an instance is created normally by calling its type, after the type’stp_newfunction has returned an instance of the type. If thetp_newfunction returns an instance of some other type that is not a subtype of the original type, no tp_initfunction is called; iftp_newreturns an instance of a subtype of the original type, the subtype’stp_initis called.

Returns0on success,-1and sets an exception on error.

Inheritance:

This field is inherited by subtypes.

Default:

Forstatic typesthis field does not have a default.

allocfuncPyTypeObject.tp_alloc¶

An optional pointer to an instance allocation function.

The function signature is:

PyObject*tp_alloc(PyTypeObject*self,Py_ssize_tnitems);

Inheritance:

This field is inherited by static subtypes, but not by dynamic subtypes (subtypes created by a class statement).

Default:

For dynamic subtypes, this field is always set to PyType_GenericAlloc(),to force a standard heap allocation strategy.

For static subtypes,PyBaseObject_Typeuses PyType_GenericAlloc().That is the recommended value for all statically defined types.

newfuncPyTypeObject.tp_new¶

An optional pointer to an instance creation function.

The function signature is:

PyObject*tp_new(PyTypeObject*subtype,PyObject*args,PyObject*kwds);

Thesubtypeargument is the type of the object being created; theargsand kwdsarguments represent positional and keyword arguments of the call to the type. Note thatsubtypedoesn’t have to equal the type whosetp_new function is called; it may be a subtype of that type (but not an unrelated type).

Thetp_newfunction should callsubtype->tp_alloc(subtype,nitems) to allocate space for the object, and then do only as much further initialization as is absolutely necessary. Initialization that can safely be ignored or repeated should be placed in thetp_inithandler. A good rule of thumb is that for immutable types, all initialization should take place intp_new,while for mutable types, most initialization should be deferred totp_init.

Set thePy_TPFLAGS_DISALLOW_INSTANTIATIONflag to disallow creating instances of the type in Python.

Inheritance:

This field is inherited by subtypes, except it is not inherited by static typeswhosetp_base isNULLor&PyBaseObject_Type.

Default:

Forstatic typesthis field has no default. This means if the slot is defined asNULL,the type cannot be called to create new instances; presumably there is some other way to create instances, like a factory function.

freefuncPyTypeObject.tp_free¶

An optional pointer to an instance deallocation function. Its signature is:

voidtp_free(void*self);

An initializer that is compatible with this signature isPyObject_Free().

Inheritance:

This field is inherited by static subtypes, but not by dynamic subtypes (subtypes created by a class statement)

Default:

In dynamic subtypes, this field is set to a deallocator suitable to matchPyType_GenericAlloc()and the value of the Py_TPFLAGS_HAVE_GCflag bit.

For static subtypes,PyBaseObject_TypeusesPyObject_Del().

inquiryPyTypeObject.tp_is_gc¶

An optional pointer to a function called by the garbage collector.

The garbage collector needs to know whether a particular object is collectible or not. Normally, it is sufficient to look at the object’s type’s tp_flagsfield, and check thePy_TPFLAGS_HAVE_GCflag bit. But some types have a mixture of statically and dynamically allocated instances, and the statically allocated instances are not collectible. Such types should define this function; it should return1for a collectible instance, and 0for a non-collectible instance. The signature is:

inttp_is_gc(PyObject*self);

(The only example of this are types themselves. The metatype, PyType_Type,defines this function to distinguish between statically anddynamically allocated types.)

Inheritance:

This field is inherited by subtypes.

Default:

This slot has no default. If this field isNULL, Py_TPFLAGS_HAVE_GCis used as the functional equivalent.

PyObject*PyTypeObject.tp_bases¶

Tuple of base types.

This field should be set toNULLand treated as read-only. Python will fill it in when the type isinitialized.

For dynamically created classes, thePy_tp_bases slotcan be used instead of thebasesargument ofPyType_FromSpecWithBases(). The argument form is preferred.

Warning

Multiple inheritance does not work well for statically defined types. If you settp_basesto a tuple, Python will not raise an error, but some slots will only be inherited from the first base.

Inheritance:

This field is not inherited.

PyObject*PyTypeObject.tp_mro¶

Tuple containing the expanded set of base types, starting with the type itself and ending withobject,in Method Resolution Order.

This field should be set toNULLand treated as read-only. Python will fill it in when the type isinitialized.

Inheritance:

This field is not inherited; it is calculated fresh by PyType_Ready().

PyObject*PyTypeObject.tp_cache¶

Unused. Internal use only.

Inheritance:

This field is not inherited.

void*PyTypeObject.tp_subclasses¶

A collection of subclasses. Internal use only. May be an invalid pointer.

To get a list of subclasses, call the Python method __subclasses__().

Changed in version 3.12:For some types, this field does not hold a validPyObject*. The type was changed tovoid*to indicate this.

Inheritance:

This field is not inherited.

PyObject*PyTypeObject.tp_weaklist¶

Weak reference list head, for weak references to this type object. Not inherited. Internal use only.

Changed in version 3.12:Internals detail: For the static builtin types this is alwaysNULL, even if weakrefs are added. Instead, the weakrefs for each are stored onPyInterpreterState.Use the public C-API or the internal _PyObject_GET_WEAKREFS_LISTPTR()macro to avoid the distinction.

Inheritance:

This field is not inherited.

destructorPyTypeObject.tp_del¶: This field is deprecated. Usetp_finalizeinstead.

unsignedintPyTypeObject.tp_version_tag¶

Used to index into the method cache. Internal use only.

Inheritance:

This field is not inherited.

destructorPyTypeObject.tp_finalize¶

An optional pointer to an instance finalization function. Its signature is:

voidtp_finalize(PyObject*self);

Iftp_finalizeis set, the interpreter calls it once when finalizing an instance. It is called either from the garbage collector (if the instance is part of an isolated reference cycle) or just before the object is deallocated. Either way, it is guaranteed to be called before attempting to break reference cycles, ensuring that it finds the object in a sane state.

tp_finalizeshould not mutate the current exception status; therefore, a recommended way to write a non-trivial finalizer is:

staticvoid
local_finalize(PyObject*self)
{
PyObject*error_type,*error_value,*error_traceback;

/* Save the current exception, if any. */
PyErr_Fetch(&error_type,&error_value,&error_traceback);

/*... */

/* Restore the saved exception. */
PyErr_Restore(error_type,error_value,error_traceback);
}

Also, note that, in a garbage collected Python, tp_deallocmay be called from any Python thread, not just the thread which created the object (if the object becomes part of a refcount cycle, that cycle might be collected by a garbage collection on any thread). This is not a problem for Python API calls, since the thread on which tp_dealloc is called will own the Global Interpreter Lock (GIL). However, if the object being destroyed in turn destroys objects from some other C or C++ library, care should be taken to ensure that destroying those objects on the thread which called tp_dealloc will not violate any assumptions of the library.

Inheritance:

This field is inherited by subtypes.

Added in version 3.4.

Changed in version 3.8:Before version 3.8 it was necessary to set the Py_TPFLAGS_HAVE_FINALIZEflags bit in order for this field to be used. This is no longer required.

Static Types¶

Traditionally, types defined in C code arestatic,that is, a staticPyTypeObjectstructure is defined directly in code and initialized usingPyType_Ready().

This results in types that are limited relative to types defined in Python:

Static types are limited to one base, i.e. they cannot use multiple inheritance.
Static type objects (but not necessarily their instances) are immutable. It is not possible to add or modify the type object’s attributes from Python.
Static type objects are shared across sub-interpreters,so they should not include any subinterpreter-specific state.

Also, sincePyTypeObjectis only part of theLimited APIas an opaque struct, any extension modules using static types must be compiled for a specific Python minor version.

Heap Types¶

An alternative tostatic typesisheap-allocated types, orheap typesfor short, which correspond closely to classes created by Python’sclassstatement. Heap types have thePy_TPFLAGS_HEAPTYPE flag set.

This is done by filling aPyType_Specstructure and calling PyType_FromSpec(),PyType_FromSpecWithBases(), PyType_FromModuleAndSpec(),orPyType_FromMetaclass().

Number Object Structures¶

typePyNumberMethods¶

This structure holds pointers to the functions which an object uses to implement the number protocol. Each function is used by the function of similar name documented in theNumber Protocolsection.

Here is the structure definition:

typedefstruct{
binaryfuncnb_add;
binaryfuncnb_subtract;
binaryfuncnb_multiply;
binaryfuncnb_remainder;
binaryfuncnb_divmod;
ternaryfuncnb_power;
unaryfuncnb_negative;
unaryfuncnb_positive;
unaryfuncnb_absolute;
inquirynb_bool;
unaryfuncnb_invert;
binaryfuncnb_lshift;
binaryfuncnb_rshift;
binaryfuncnb_and;
binaryfuncnb_xor;
binaryfuncnb_or;
unaryfuncnb_int;
void*nb_reserved;
unaryfuncnb_float;

binaryfuncnb_inplace_add;
binaryfuncnb_inplace_subtract;
binaryfuncnb_inplace_multiply;
binaryfuncnb_inplace_remainder;
ternaryfuncnb_inplace_power;
binaryfuncnb_inplace_lshift;
binaryfuncnb_inplace_rshift;
binaryfuncnb_inplace_and;
binaryfuncnb_inplace_xor;
binaryfuncnb_inplace_or;

binaryfuncnb_floor_divide;
binaryfuncnb_true_divide;
binaryfuncnb_inplace_floor_divide;
binaryfuncnb_inplace_true_divide;

unaryfuncnb_index;

binaryfuncnb_matrix_multiply;
binaryfuncnb_inplace_matrix_multiply;
}PyNumberMethods;

Note

Binary and ternary functions must check the type of all their operands, and implement the necessary conversions (at least one of the operands is an instance of the defined type). If the operation is not defined for the given operands, binary and ternary functions must return Py_NotImplemented,if another error occurred they must returnNULL and set an exception.

Note

Thenb_reservedfield should always beNULL.It was previously callednb_long,and was renamed in Python 3.0.1.

binaryfuncPyNumberMethods.nb_add¶

binaryfuncPyNumberMethods.nb_subtract¶

binaryfuncPyNumberMethods.nb_multiply¶

binaryfuncPyNumberMethods.nb_remainder¶

binaryfuncPyNumberMethods.nb_divmod¶

ternaryfuncPyNumberMethods.nb_power¶

unaryfuncPyNumberMethods.nb_negative¶

unaryfuncPyNumberMethods.nb_positive¶

unaryfuncPyNumberMethods.nb_absolute¶

inquiryPyNumberMethods.nb_bool¶

unaryfuncPyNumberMethods.nb_invert¶

binaryfuncPyNumberMethods.nb_lshift¶

binaryfuncPyNumberMethods.nb_rshift¶

binaryfuncPyNumberMethods.nb_and¶

binaryfuncPyNumberMethods.nb_xor¶

binaryfuncPyNumberMethods.nb_or¶

unaryfuncPyNumberMethods.nb_int¶

void*PyNumberMethods.nb_reserved¶

unaryfuncPyNumberMethods.nb_float¶

binaryfuncPyNumberMethods.nb_inplace_add¶

binaryfuncPyNumberMethods.nb_inplace_subtract¶

binaryfuncPyNumberMethods.nb_inplace_multiply¶

binaryfuncPyNumberMethods.nb_inplace_remainder¶

ternaryfuncPyNumberMethods.nb_inplace_power¶

binaryfuncPyNumberMethods.nb_inplace_lshift¶

binaryfuncPyNumberMethods.nb_inplace_rshift¶

binaryfuncPyNumberMethods.nb_inplace_and¶

binaryfuncPyNumberMethods.nb_inplace_xor¶

binaryfuncPyNumberMethods.nb_inplace_or¶

binaryfuncPyNumberMethods.nb_floor_divide¶

binaryfuncPyNumberMethods.nb_true_divide¶

binaryfuncPyNumberMethods.nb_inplace_floor_divide¶

binaryfuncPyNumberMethods.nb_inplace_true_divide¶

unaryfuncPyNumberMethods.nb_index¶

binaryfuncPyNumberMethods.nb_matrix_multiply¶

binaryfuncPyNumberMethods.nb_inplace_matrix_multiply¶

Mapping Object Structures¶

typePyMappingMethods¶: This structure holds pointers to the functions which an object uses to implement the mapping protocol. It has three members:

lenfuncPyMappingMethods.mp_length¶: This function is used byPyMapping_Size()and PyObject_Size(),and has the same signature. This slot may be set to NULLif the object has no defined length.

binaryfuncPyMappingMethods.mp_subscript¶: This function is used byPyObject_GetItem()and PySequence_GetSlice(),and has the same signature as PyObject_GetItem().This slot must be filled for the PyMapping_Check()function to return1,it can beNULL otherwise.

objobjargprocPyMappingMethods.mp_ass_subscript¶: This function is used byPyObject_SetItem(), PyObject_DelItem(),PySequence_SetSlice()and PySequence_DelSlice().It has the same signature as PyObject_SetItem(),butvcan also be set toNULLto delete an item. If this slot isNULL,the object does not support item assignment and deletion.

Sequence Object Structures¶

typePySequenceMethods¶: This structure holds pointers to the functions which an object uses to implement the sequence protocol.

lenfuncPySequenceMethods.sq_length¶: This function is used byPySequence_Size()and PyObject_Size(),and has the same signature. It is also used for handling negative indices via thesq_item and thesq_ass_itemslots.

binaryfuncPySequenceMethods.sq_concat¶: This function is used byPySequence_Concat()and has the same signature. It is also used by the+operator, after trying the numeric addition via thenb_addslot.

ssizeargfuncPySequenceMethods.sq_repeat¶: This function is used byPySequence_Repeat()and has the same signature. It is also used by the*operator, after trying numeric multiplication via thenb_multiplyslot.

ssizeargfuncPySequenceMethods.sq_item¶

This function is used byPySequence_GetItem()and has the same signature. It is also used byPyObject_GetItem(),after trying the subscription via themp_subscriptslot. This slot must be filled for thePySequence_Check() function to return1,it can beNULLotherwise.

Negative indexes are handled as follows: if thesq_lengthslot is filled, it is called and the sequence length is used to compute a positive index which is passed tosq_item.Ifsq_lengthisNULL, the index is passed as is to the function.

ssizeobjargprocPySequenceMethods.sq_ass_item¶: This function is used byPySequence_SetItem()and has the same signature. It is also used byPyObject_SetItem()and PyObject_DelItem(),after trying the item assignment and deletion via themp_ass_subscriptslot. This slot may be left toNULLif the object does not support item assignment and deletion.

objobjprocPySequenceMethods.sq_contains¶: This function may be used byPySequence_Contains()and has the same signature. This slot may be left toNULL,in this case PySequence_Contains()simply traverses the sequence until it finds a match.

binaryfuncPySequenceMethods.sq_inplace_concat¶: This function is used byPySequence_InPlaceConcat()and has the same signature. It should modify its first operand, and return it. This slot may be left toNULL,in this casePySequence_InPlaceConcat() will fall back toPySequence_Concat().It is also used by the augmented assignment+=,after trying numeric in-place addition via thenb_inplace_addslot.

ssizeargfuncPySequenceMethods.sq_inplace_repeat¶: This function is used byPySequence_InPlaceRepeat()and has the same signature. It should modify its first operand, and return it. This slot may be left toNULL,in this casePySequence_InPlaceRepeat() will fall back toPySequence_Repeat().It is also used by the augmented assignment*=,after trying numeric in-place multiplication via thenb_inplace_multiplyslot.

Buffer Object Structures¶

typePyBufferProcs¶: This structure holds pointers to the functions required by the Buffer protocol.The protocol defines how an exporter object can expose its internal data to consumer objects.

getbufferprocPyBufferProcs.bf_getbuffer¶

The signature of this function is:

int(PyObject*exporter,Py_buffer*view,intflags);

Handle a request toexporterto fill inviewas specified byflags. Except for point (3), an implementation of this function MUST take these steps:

Check if the request can be met. If not, raiseBufferError, setview->objtoNULLand return-1.
Fill in the requested fields.
Increment an internal counter for the number of exports.
Setview->objtoexporterand incrementview->obj.
Return0.

Ifexporteris part of a chain or tree of buffer providers, two main schemes can be used:

Re-export: Each member of the tree acts as the exporting object and setsview->objto a new reference to itself.
Redirect: The buffer request is redirected to the root object of the tree. Here,view->objwill be a new reference to the root object.

The individual fields ofvieware described in section Buffer structure,the rules how an exporter must react to specific requests are in section Buffer request types.

All memory pointed to in thePy_bufferstructure belongs to the exporter and must remain valid until there are no consumers left. format,shape, strides,suboffsets andinternal are read-only for the consumer.

PyBuffer_FillInfo()provides an easy way of exposing a simple bytes buffer while dealing correctly with all request types.

PyObject_GetBuffer()is the interface for the consumer that wraps this function.

releasebufferprocPyBufferProcs.bf_releasebuffer¶

The signature of this function is:

void(PyObject*exporter,Py_buffer*view);

Handle a request to release the resources of the buffer. If no resources need to be released,PyBufferProcs.bf_releasebuffermay be NULL.Otherwise, a standard implementation of this function will take these optional steps:

Decrement an internal counter for the number of exports.
If the counter is0,free all memory associated withview.

The exporter MUST use theinternalfield to keep track of buffer-specific resources. This field is guaranteed to remain constant, while a consumer MAY pass a copy of the original buffer as the viewargument.

This function MUST NOT decrementview->obj,since that is done automatically inPyBuffer_Release()(this scheme is useful for breaking reference cycles).

PyBuffer_Release()is the interface for the consumer that wraps this function.

Async Object Structures¶

Added in version 3.5.

typePyAsyncMethods¶

This structure holds pointers to the functions required to implement awaitableandasynchronous iteratorobjects.

Here is the structure definition:

typedefstruct{
unaryfuncam_await;
unaryfuncam_aiter;
unaryfuncam_anext;
sendfuncam_send;
}PyAsyncMethods;

unaryfuncPyAsyncMethods.am_await¶

The signature of this function is:

PyObject*am_await(PyObject*self);

The returned object must be aniterator,i.e.PyIter_Check() must return1for it.

This slot may be set toNULLif an object is not anawaitable.

unaryfuncPyAsyncMethods.am_aiter¶

The signature of this function is:

PyObject*am_aiter(PyObject*self);

Must return anasynchronous iteratorobject. See__anext__()for details.

This slot may be set toNULLif an object does not implement asynchronous iteration protocol.

unaryfuncPyAsyncMethods.am_anext¶

The signature of this function is:

PyObject*am_anext(PyObject*self);

Must return anawaitableobject. See__anext__()for details. This slot may be set toNULL.

sendfuncPyAsyncMethods.am_send¶

The signature of this function is:

PySendResultam_send(PyObject*self,PyObject*arg,PyObject**result);

SeePyIter_Send()for details. This slot may be set toNULL.

Added in version 3.10.

Slot Type typedefs¶

typedefPyObject*(*allocfunc)(PyTypeObject*cls,Py_ssize_tnitems)¶

Part of theStable ABI.

The purpose of this function is to separate memory allocation from memory initialization. It should return a pointer to a block of memory of adequate length for the instance, suitably aligned, and initialized to zeros, but with ob_refcntset to1andob_typeset to the type argument. If the type’stp_itemsizeis non-zero, the object’sob_sizefield should be initialized tonitemsand the length of the allocated memory block should betp_basicsize+nitems*tp_itemsize,rounded up to a multiple of sizeof(void*);otherwise,nitemsis not used and the length of the block should betp_basicsize.

This function should not do any other instance initialization, not even to allocate additional memory; that should be done bytp_new.

typedefvoid(*destructor)(PyObject*)¶: Part of theStable ABI.

typedefvoid(*freefunc)(void*)¶: Seetp_free.

typedefPyObject*(*newfunc)(PyObject*,PyObject*,PyObject*)¶: Part of theStable ABI.
Seetp_new.

typedefint(*initproc)(PyObject*,PyObject*,PyObject*)¶: Part of theStable ABI.
Seetp_init.

typedefPyObject*(*reprfunc)(PyObject*)¶: Part of theStable ABI.
Seetp_repr.

typedefPyObject*(*getattrfunc)(PyObject*self,char*attr)¶: Part of theStable ABI.
Return the value of the named attribute for the object.

typedefint(*setattrfunc)(PyObject*self,char*attr,PyObject*value)¶: Part of theStable ABI.
Set the value of the named attribute for the object. The value argument is set toNULLto delete the attribute.

typedefPyObject*(*getattrofunc)(PyObject*self,PyObject*attr)¶

Part of theStable ABI.

Return the value of the named attribute for the object.

Seetp_getattro.

typedefint(*setattrofunc)(PyObject*self,PyObject*attr,PyObject*value)¶

Part of theStable ABI.

Set the value of the named attribute for the object. The value argument is set toNULLto delete the attribute.

Seetp_setattro.

typedefPyObject*(*descrgetfunc)(PyObject*,PyObject*,PyObject*)¶: Part of theStable ABI.
Seetp_descr_get.

typedefint(*descrsetfunc)(PyObject*,PyObject*,PyObject*)¶: Part of theStable ABI.
Seetp_descr_set.

typedefPy_hash_t(*hashfunc)(PyObject*)¶: Part of theStable ABI.
Seetp_hash.

typedefPyObject*(*richcmpfunc)(PyObject*,PyObject*,int)¶: Part of theStable ABI.
Seetp_richcompare.

typedefPyObject*(*getiterfunc)(PyObject*)¶: Part of theStable ABI.
Seetp_iter.

typedefPyObject*(*iternextfunc)(PyObject*)¶: Part of theStable ABI.
Seetp_iternext.

typedefPy_ssize_t(*lenfunc)(PyObject*)¶: Part of theStable ABI.

typedefint(*getbufferproc)(PyObject*,Py_buffer*,int)¶: Part of theStable ABIsince version 3.12.

typedefvoid(*releasebufferproc)(PyObject*,Py_buffer*)¶: Part of theStable ABIsince version 3.12.

typedefPyObject*(*unaryfunc)(PyObject*)¶: Part of theStable ABI.

typedefPyObject*(*binaryfunc)(PyObject*,PyObject*)¶: Part of theStable ABI.

typedefPySendResult(*sendfunc)(PyObject*,PyObject*,PyObject**)¶: Seeam_send.

typedefPyObject*(*ternaryfunc)(PyObject*,PyObject*,PyObject*)¶: Part of theStable ABI.

typedefPyObject*(*ssizeargfunc)(PyObject*,Py_ssize_t)¶: Part of theStable ABI.

typedefint(*ssizeobjargproc)(PyObject*,Py_ssize_t,PyObject*)¶: Part of theStable ABI.

typedefint(*objobjproc)(PyObject*,PyObject*)¶: Part of theStable ABI.

typedefint(*objobjargproc)(PyObject*,PyObject*,PyObject*)¶: Part of theStable ABI.

Examples¶

The following are simple examples of Python type definitions. They include common usage you may encounter. Some demonstrate tricky corner cases. For more examples, practical info, and a tutorial, see Defining Extension Types: TutorialandDefining Extension Types: Assorted Topics.

A basicstatic type:

typedefstruct{
PyObject_HEAD
constchar*data;
}MyObject;

staticPyTypeObjectMyObject_Type={
PyVarObject_HEAD_INIT(NULL,0)
.tp_name="mymod.MyObject",
.tp_basicsize=sizeof(MyObject),
.tp_doc=PyDoc_STR("My objects"),
.tp_new=myobj_new,
.tp_dealloc=(destructor)myobj_dealloc,
.tp_repr=(reprfunc)myobj_repr,
};

You may also find older code (especially in the CPython code base) with a more verbose initializer:

staticPyTypeObjectMyObject_Type={
PyVarObject_HEAD_INIT(NULL,0)
"mymod.MyObject",/* tp_name */
sizeof(MyObject),/* tp_basicsize */
0,/* tp_itemsize */
(destructor)myobj_dealloc,/* tp_dealloc */
0,/* tp_vectorcall_offset */
0,/* tp_getattr */
0,/* tp_setattr */
0,/* tp_as_async */
(reprfunc)myobj_repr,/* tp_repr */
0,/* tp_as_number */
0,/* tp_as_sequence */
0,/* tp_as_mapping */
0,/* tp_hash */
0,/* tp_call */
0,/* tp_str */
0,/* tp_getattro */
0,/* tp_setattro */
0,/* tp_as_buffer */
0,/* tp_flags */
PyDoc_STR("My objects"),/* tp_doc */
0,/* tp_traverse */
0,/* tp_clear */
0,/* tp_richcompare */
0,/* tp_weaklistoffset */
0,/* tp_iter */
0,/* tp_iternext */
0,/* tp_methods */
0,/* tp_members */
0,/* tp_getset */
0,/* tp_base */
0,/* tp_dict */
0,/* tp_descr_get */
0,/* tp_descr_set */
0,/* tp_dictoffset */
0,/* tp_init */
0,/* tp_alloc */
myobj_new,/* tp_new */
};

A type that supports weakrefs, instance dicts, and hashing:

typedefstruct{
PyObject_HEAD
constchar*data;
}MyObject;

staticPyTypeObjectMyObject_Type={
PyVarObject_HEAD_INIT(NULL,0)
.tp_name="mymod.MyObject",
.tp_basicsize=sizeof(MyObject),
.tp_doc=PyDoc_STR("My objects"),
.tp_flags=Py_TPFLAGS_DEFAULT|Py_TPFLAGS_BASETYPE|
Py_TPFLAGS_HAVE_GC|Py_TPFLAGS_MANAGED_DICT|
Py_TPFLAGS_MANAGED_WEAKREF,
.tp_new=myobj_new,
.tp_traverse=(traverseproc)myobj_traverse,
.tp_clear=(inquiry)myobj_clear,
.tp_alloc=PyType_GenericNew,
.tp_dealloc=(destructor)myobj_dealloc,
.tp_repr=(reprfunc)myobj_repr,
.tp_hash=(hashfunc)myobj_hash,
.tp_richcompare=PyBaseObject_Type.tp_richcompare,
};

A str subclass that cannot be subclassed and cannot be called to create instances (e.g. uses a separate factory func) using Py_TPFLAGS_DISALLOW_INSTANTIATIONflag:

typedefstruct{
PyUnicodeObjectraw;
char*extra;
}MyStr;

staticPyTypeObjectMyStr_Type={
PyVarObject_HEAD_INIT(NULL,0)
.tp_name="mymod.MyStr",
.tp_basicsize=sizeof(MyStr),
.tp_base=NULL,// set to &PyUnicode_Type in module init
.tp_doc=PyDoc_STR("my custom str"),
.tp_flags=Py_TPFLAGS_DEFAULT|Py_TPFLAGS_DISALLOW_INSTANTIATION,
.tp_repr=(reprfunc)myobj_repr,
};

The simpleststatic typewith fixed-length instances:

typedefstruct{
PyObject_HEAD
}MyObject;

staticPyTypeObjectMyObject_Type={
PyVarObject_HEAD_INIT(NULL,0)
.tp_name="mymod.MyObject",
};

The simpleststatic typewith variable-length instances:

typedefstruct{
PyObject_VAR_HEAD
constchar*data[1];
}MyObject;

staticPyTypeObjectMyObject_Type={
PyVarObject_HEAD_INIT(NULL,0)
.tp_name="mymod.MyObject",
.tp_basicsize=sizeof(MyObject)-sizeof(char*),
.tp_itemsize=sizeof(char*),
};

Type Objects¶

Quick Reference¶

“tp slots”¶

sub-slots¶

slot typedefs¶

PyTypeObject Definition¶

PyObject Slots¶

PyVarObject Slots¶

PyTypeObject Slots¶

Static Types¶

Heap Types¶

Number Object Structures¶

Mapping Object Structures¶

Sequence Object Structures¶

Buffer Object Structures¶

Async Object Structures¶

Slot Type typedefs¶

Examples¶

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