/* Object and type object interface */
Objects are structures allocated on the heap. Special rules apply to
the use of objects to ensure they are properly garbage-collected.
Objects are never allocated statically or on the stack; they must be
accessed through special macros and functions only. (Type objects are
exceptions to the first rule; the standard types are represented by
statically initialized type objects, although work on type/class unification
for Python 2.2 made it possible to have heap-allocated type objects too).
An object has a 'reference count' that is increased or decreased when a
pointer to the object is copied or deleted; when the reference count
reaches zero there are no references to the object left and it can be
An object has a 'type' that determines what it represents and what kind
of data it contains. An object's type is fixed when it is created.
Types themselves are represented as objects; an object contains a
pointer to the corresponding type object. The type itself has a type
pointer pointing to the object representing the type 'type', which
contains a pointer to itself!).
Objects do not float around in memory; once allocated an object keeps
the same size and address. Objects that must hold variable-size data
can contain pointers to variable-size parts of the object. Not all
objects of the same type have the same size; but the size cannot change
after allocation. (These restrictions are made so a reference to an
object can be simply a pointer -- moving an object would require
updating all the pointers, and changing an object's size would require
moving it if there was another object right next to it.)
Objects are always accessed through pointers of the type 'PyObject *'.
The type 'PyObject' is a structure that only contains the reference count
and the type pointer. The actual memory allocated for an object
contains other data that can only be accessed after casting the pointer
to a pointer to a longer structure type. This longer type must start
with the reference count and type fields; the macro PyObject_HEAD should be
used for this (to accommodate for future changes). The implementation
of a particular object type can cast the object pointer to the proper
A standard interface exists for objects that contain an array of items
whose size is determined when the object is allocated.
/* Py_DEBUG implies Py_TRACE_REFS. */
#if defined(Py_DEBUG) && !defined(Py_TRACE_REFS)
/* Py_TRACE_REFS implies Py_REF_DEBUG. */
#if defined(Py_TRACE_REFS) && !defined(Py_REF_DEBUG)
#if defined(Py_LIMITED_API) && defined(Py_REF_DEBUG)
#error Py_LIMITED_API is incompatible with Py_DEBUG, Py_TRACE_REFS, and Py_REF_DEBUG
/* Define pointers to support a doubly-linked list of all live heap objects. */
#define _PyObject_HEAD_EXTRA \
struct _object *_ob_next; \
struct _object *_ob_prev;
#define _PyObject_EXTRA_INIT 0, 0,
#define _PyObject_HEAD_EXTRA
#define _PyObject_EXTRA_INIT
/* PyObject_HEAD defines the initial segment of every PyObject. */
#define PyObject_HEAD PyObject ob_base;
#define PyObject_HEAD_INIT(type) \
#define PyVarObject_HEAD_INIT(type, size) \
{ PyObject_HEAD_INIT(type) size },
/* PyObject_VAR_HEAD defines the initial segment of all variable-size
* container objects. These end with a declaration of an array with 1
* element, but enough space is malloc'ed so that the array actually
* has room for ob_size elements. Note that ob_size is an element count,
* not necessarily a byte count.
#define PyObject_VAR_HEAD PyVarObject ob_base;
#define Py_INVALID_SIZE (Py_ssize_t)-1
/* Nothing is actually declared to be a PyObject, but every pointer to
* a Python object can be cast to a PyObject*. This is inheritance built
* by hand. Similarly every pointer to a variable-size Python object can,
* in addition, be cast to PyVarObject*.
struct _typeobject *ob_type;
Py_ssize_t ob_size; /* Number of items in variable part */
#define Py_REFCNT(ob) (((PyObject*)(ob))->ob_refcnt)
#define Py_TYPE(ob) (((PyObject*)(ob))->ob_type)
#define Py_SIZE(ob) (((PyVarObject*)(ob))->ob_size)
/********************* String Literals ****************************************/
/* This structure helps managing static strings. The basic usage goes like this:
r = PyObject_CallMethod(o, "foo", "args", ...);
r = _PyObject_CallMethodId(o, &PyId_foo, "args", ...);
PyId_foo is a static variable, either on block level or file level. On first
usage, the string "foo" is interned, and the structures are linked. On interpreter
shutdown, all strings are released (through _PyUnicode_ClearStaticStrings).
Alternatively, _Py_static_string allows choosing the variable name.
_PyUnicode_FromId returns a borrowed reference to the interned string.
_PyObject_{Get,Set,Has}AttrId are __getattr__ versions using _Py_Identifier*.
typedef struct _Py_Identifier {
struct _Py_Identifier *next;
#define _Py_static_string_init(value) { .next = NULL, .string = value, .object = NULL }
#define _Py_static_string(varname, value) static _Py_Identifier varname = _Py_static_string_init(value)
#define _Py_IDENTIFIER(varname) _Py_static_string(PyId_##varname, #varname)
#endif /* !Py_LIMITED_API */
Type objects contain a string containing the type name (to help somewhat
in debugging), the allocation parameters (see PyObject_New() and
and methods for accessing objects of the type. Methods are optional, a
nil pointer meaning that particular kind of access is not available for
this type. The Py_DECREF() macro uses the tp_dealloc method without
checking for a nil pointer; it should always be implemented except if
the implementation can guarantee that the reference count will never
reach zero (e.g., for statically allocated type objects).
NB: the methods for certain type groups are now contained in separate
typedef PyObject * (*unaryfunc)(PyObject *);
typedef PyObject * (*binaryfunc)(PyObject *, PyObject *);
typedef PyObject * (*ternaryfunc)(PyObject *, PyObject *, PyObject *);
typedef int (*inquiry)(PyObject *);
typedef Py_ssize_t (*lenfunc)(PyObject *);
typedef PyObject *(*ssizeargfunc)(PyObject *, Py_ssize_t);
typedef PyObject *(*ssizessizeargfunc)(PyObject *, Py_ssize_t, Py_ssize_t);
typedef int(*ssizeobjargproc)(PyObject *, Py_ssize_t, PyObject *);
typedef int(*ssizessizeobjargproc)(PyObject *, Py_ssize_t, Py_ssize_t, PyObject *);
typedef int(*objobjargproc)(PyObject *, PyObject *, PyObject *);
typedef struct bufferinfo {
PyObject *obj; /* owned reference */
Py_ssize_t itemsize; /* This is Py_ssize_t so it can be
pointed to by strides in simple case.*/
typedef int (*getbufferproc)(PyObject *, Py_buffer *, int);
typedef void (*releasebufferproc)(PyObject *, Py_buffer *);
/* Maximum number of dimensions */
#define PyBUF_MAX_NDIM 64
/* Flags for getting buffers */
#define PyBUF_WRITABLE 0x0001
/* we used to include an E, backwards compatible alias */
#define PyBUF_WRITEABLE PyBUF_WRITABLE
#define PyBUF_FORMAT 0x0004
#define PyBUF_STRIDES (0x0010 | PyBUF_ND)
#define PyBUF_C_CONTIGUOUS (0x0020 | PyBUF_STRIDES)
#define PyBUF_F_CONTIGUOUS (0x0040 | PyBUF_STRIDES)
#define PyBUF_ANY_CONTIGUOUS (0x0080 | PyBUF_STRIDES)
#define PyBUF_INDIRECT (0x0100 | PyBUF_STRIDES)
#define PyBUF_CONTIG (PyBUF_ND | PyBUF_WRITABLE)
#define PyBUF_CONTIG_RO (PyBUF_ND)
#define PyBUF_STRIDED (PyBUF_STRIDES | PyBUF_WRITABLE)
#define PyBUF_STRIDED_RO (PyBUF_STRIDES)
#define PyBUF_RECORDS (PyBUF_STRIDES | PyBUF_WRITABLE | PyBUF_FORMAT)
#define PyBUF_RECORDS_RO (PyBUF_STRIDES | PyBUF_FORMAT)
#define PyBUF_FULL (PyBUF_INDIRECT | PyBUF_WRITABLE | PyBUF_FORMAT)
#define PyBUF_FULL_RO (PyBUF_INDIRECT | PyBUF_FORMAT)
#define PyBUF_WRITE 0x200
/* End buffer interface */
#endif /* Py_LIMITED_API */
typedef int (*objobjproc)(PyObject *, PyObject *);
typedef int (*visitproc)(PyObject *, void *);
typedef int (*traverseproc)(PyObject *, visitproc, void *);
/* Number implementations must check *both*
arguments for proper type and implement the necessary conversions
in the slot functions themselves. */
void *nb_reserved; /* the slot formerly known as nb_long */
binaryfunc nb_inplace_add;
binaryfunc nb_inplace_subtract;
binaryfunc nb_inplace_multiply;
binaryfunc nb_inplace_remainder;
ternaryfunc nb_inplace_power;
binaryfunc nb_inplace_lshift;
binaryfunc nb_inplace_rshift;
binaryfunc nb_inplace_and;
binaryfunc nb_inplace_xor;
binaryfunc nb_inplace_or;
binaryfunc nb_floor_divide;
binaryfunc nb_true_divide;
binaryfunc nb_inplace_floor_divide;
binaryfunc nb_inplace_true_divide;
binaryfunc nb_matrix_multiply;
binaryfunc nb_inplace_matrix_multiply;
ssizeobjargproc sq_ass_item;
binaryfunc sq_inplace_concat;
ssizeargfunc sq_inplace_repeat;
objobjargproc mp_ass_subscript;
getbufferproc bf_getbuffer;
releasebufferproc bf_releasebuffer;
#endif /* Py_LIMITED_API */
typedef void (*freefunc)(void *);
typedef void (*destructor)(PyObject *);
/* We can't provide a full compile-time check that limited-API
users won't implement tp_print. However, not defining printfunc
and making tp_print of a different function pointer type
should at least cause a warning in most cases. */
typedef int (*printfunc)(PyObject *, FILE *, int);
typedef PyObject *(*getattrfunc)(PyObject *, char *);
typedef PyObject *(*getattrofunc)(PyObject *, PyObject *);
typedef int (*setattrfunc)(PyObject *, char *, PyObject *);
typedef int (*setattrofunc)(PyObject *, PyObject *, PyObject *);
typedef PyObject *(*reprfunc)(PyObject *);
typedef Py_hash_t (*hashfunc)(PyObject *);
typedef PyObject *(*richcmpfunc) (PyObject *, PyObject *, int);
typedef PyObject *(*getiterfunc) (PyObject *);
typedef PyObject *(*iternextfunc) (PyObject *);
typedef PyObject *(*descrgetfunc) (PyObject *, PyObject *, PyObject *);
typedef int (*descrsetfunc) (PyObject *, PyObject *, PyObject *);
typedef int (*initproc)(PyObject *, PyObject *, PyObject *);
typedef PyObject *(*newfunc)(struct _typeobject *, PyObject *, PyObject *);
typedef PyObject *(*allocfunc)(struct _typeobject *, Py_ssize_t);
typedef struct _typeobject PyTypeObject; /* opaque */
typedef struct _typeobject {
const char *tp_name; /* For printing, in format "<module>.<name>" */
Py_ssize_t tp_basicsize, tp_itemsize; /* For allocation */
/* Methods to implement standard operations */
PyAsyncMethods *tp_as_async; /* formerly known as tp_compare (Python 2)
or tp_reserved (Python 3) */
/* Method suites for standard classes */
PyNumberMethods *tp_as_number;
PySequenceMethods *tp_as_sequence;
PyMappingMethods *tp_as_mapping;
/* More standard operations (here for binary compatibility) */
getattrofunc tp_getattro;
setattrofunc tp_setattro;
/* Functions to access object as input/output buffer */
PyBufferProcs *tp_as_buffer;
/* Flags to define presence of optional/expanded features */
const char *tp_doc; /* Documentation string */
/* Assigned meaning in release 2.0 */
/* call function for all accessible objects */
traverseproc tp_traverse;
/* delete references to contained objects */
/* Assigned meaning in release 2.1 */
richcmpfunc tp_richcompare;
/* weak reference enabler */
Py_ssize_t tp_weaklistoffset;
iternextfunc tp_iternext;
/* Attribute descriptor and subclassing stuff */
struct PyMethodDef *tp_methods;
struct PyMemberDef *tp_members;
struct PyGetSetDef *tp_getset;
struct _typeobject *tp_base;
descrgetfunc tp_descr_get;
descrsetfunc tp_descr_set;
Py_ssize_t tp_dictoffset;
freefunc tp_free; /* Low-level free-memory routine */
inquiry tp_is_gc; /* For PyObject_IS_GC */
PyObject *tp_mro; /* method resolution order */
/* Type attribute cache version tag. Added in version 2.6 */
unsigned int tp_version_tag;
/* these must be last and never explicitly initialized */
struct _typeobject *tp_prev;
struct _typeobject *tp_next;
int slot; /* slot id, see below */
void *pfunc; /* function pointer */
PyType_Slot *slots; /* terminated by slot==0. */
PyAPI_FUNC(PyObject*) PyType_FromSpec(PyType_Spec*);
#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03030000
PyAPI_FUNC(PyObject*) PyType_FromSpecWithBases(PyType_Spec*, PyObject*);
#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03040000
PyAPI_FUNC(void*) PyType_GetSlot(PyTypeObject*, int);
/* The *real* layout of a type object when allocated on the heap */
typedef struct _heaptypeobject {
/* Note: there's a dependency on the order of these members
in slotptr() in typeobject.c . */
PyNumberMethods as_number;
PyMappingMethods as_mapping;
PySequenceMethods as_sequence; /* as_sequence comes after as_mapping,
so that the mapping wins when both
the mapping and the sequence define
a given operator (e.g. __getitem__).
see add_operators() in typeobject.c . */
PyObject *ht_name, *ht_slots, *ht_qualname;
struct _dictkeysobject *ht_cached_keys;
/* here are optional user slots, followed by the members. */
/* access macro to the members which are floating "behind" the object */
#define PyHeapType_GET_MEMBERS(etype) \
((PyMemberDef *)(((char *)etype) + Py_TYPE(etype)->tp_basicsize))
PyAPI_FUNC(int) PyType_IsSubtype(PyTypeObject *, PyTypeObject *);
#define PyObject_TypeCheck(ob, tp) \
(Py_TYPE(ob) == (tp) || PyType_IsSubtype(Py_TYPE(ob), (tp)))
PyAPI_DATA(PyTypeObject) PyType_Type; /* built-in 'type' */
PyAPI_DATA(PyTypeObject) PyBaseObject_Type; /* built-in 'object' */
PyAPI_DATA(PyTypeObject) PySuper_Type; /* built-in 'super' */
PyAPI_FUNC(unsigned long) PyType_GetFlags(PyTypeObject*);
#define PyType_Check(op) \
PyType_FastSubclass(Py_TYPE(op), Py_TPFLAGS_TYPE_SUBCLASS)
#define PyType_CheckExact(op) (Py_TYPE(op) == &PyType_Type)
PyAPI_FUNC(int) PyType_Ready(PyTypeObject *);
PyAPI_FUNC(PyObject *) PyType_GenericAlloc(PyTypeObject *, Py_ssize_t);
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