通用对象结构 ¶

Python 对象类型定义使用了大量 Structure。此节描述这些 Structure 及如何使用它们。

基对象类型和宏 ¶

All Python objects ultimately share a small number of fields at the beginning of the object’s representation in memory. These are represented by the PyObject and PyVarObject types, which are defined, in turn, by the expansions of some macros also used, whether directly or indirectly, in the definition of all other Python objects.

type PyObject ¶

属于 Limited API . (Only some members are part of the stable ABI.)

All object types are extensions of this type. This is a type which contains the information Python needs to treat a pointer to an object as an object. In a normal “release” build, it contains only the object’s reference count and a pointer to the corresponding type object. Nothing is actually declared to be a PyObject , but every pointer to a Python object can be cast to a PyObject * . Access to the members must be done by using the macros Py_REFCNT and Py_TYPE .

type PyVarObject ¶

属于 Limited API . (Only some members are part of the stable ABI.)

This is an extension of PyObject that adds the ob_size field. This is only used for objects that have some notion of length . This type does not often appear in the Python/C API. Access to the members must be done by using the macros Py_REFCNT , Py_TYPE ，和 Py_SIZE .

PyObject_HEAD ¶

This is a macro used when declaring new types which represent objects without a varying length. The PyObject_HEAD macro expands to:

PyObject ob_base;
						

See documentation of PyObject above.

PyObject_VAR_HEAD ¶

This is a macro used when declaring new types which represent objects with a length that varies from instance to instance. The PyObject_VAR_HEAD macro expands to:

PyVarObject ob_base;
						

See documentation of PyVarObject above.

int Py_Is ( PyObject * x , PyObject * y ) ¶

属于 稳定 ABI (应用程序二进制接口) since version 3.10.

Test if the x 对象是 y object, the same as x is y in Python.

3.10 版新增。

int Py_IsNone ( PyObject * x ) ¶

属于 稳定 ABI (应用程序二进制接口) since version 3.10.

Test if an object is the None singleton, the same as x is None in Python.

3.10 版新增。

int Py_IsTrue ( PyObject * x ) ¶

属于 稳定 ABI (应用程序二进制接口) since version 3.10.

Test if an object is the True singleton, the same as x is True in Python.

3.10 版新增。

int Py_IsFalse ( PyObject * x ) ¶

属于 稳定 ABI (应用程序二进制接口) since version 3.10.

Test if an object is the False singleton, the same as x is False in Python.

3.10 版新增。

PyTypeObject * Py_TYPE ( PyObject * o ) ¶

Get the type of the Python object o .

返回 借位引用 .

使用 Py_SET_TYPE() function to set an object type.

3.11 版改变： Py_TYPE() is changed to an inline static function. The parameter type is no longer const PyObject * .

int Py_IS_TYPE ( PyObject * o , PyTypeObject * type ) ¶

Return non-zero if the object o 类型为 type . Return zero otherwise. Equivalent to: Py_TYPE(o) == type .

3.9 版新增。

void Py_SET_TYPE ( PyObject * o , PyTypeObject * type ) ¶

设置对象 o type to type .

3.9 版新增。

Py_ssize_t Py_REFCNT ( PyObject * o ) ¶

Get the reference count of the Python object o .

使用 Py_SET_REFCNT() function to set an object reference count.

3.11 版改变： The parameter type is no longer const PyObject * .

3.10 版改变： Py_REFCNT() is changed to the inline static function.

void Py_SET_REFCNT ( PyObject * o , Py_ssize_t refcnt ) ¶

设置对象 o reference counter to refcnt .

3.9 版新增。

Py_ssize_t Py_SIZE ( PyVarObject * o ) ¶

Get the size of the Python object o .

使用 Py_SET_SIZE() function to set an object size.

3.11 版改变： Py_SIZE() is changed to an inline static function. The parameter type is no longer const PyVarObject * .

void Py_SET_SIZE ( PyVarObject * o , Py_ssize_t size ) ¶

设置对象 o size to size .

3.9 版新增。

PyObject_HEAD_INIT ( type ) ¶

This is a macro which expands to initialization values for a new PyObject type. This macro expands to:

_PyObject_EXTRA_INIT
1, type,
						

PyVarObject_HEAD_INIT ( type , size ) ¶

This is a macro which expands to initialization values for a new PyVarObject type, including the ob_size field. This macro expands to:

_PyObject_EXTRA_INIT
1, type, size,
						

实现函数和方法 ¶

type PyCFunction ¶

属于 稳定 ABI (应用程序二进制接口) .

Type of the functions used to implement most Python callables in C. Functions of this type take two PyObject * parameters and return one such value. If the return value is NULL , an exception shall have been set. If not NULL , the return value is interpreted as the return value of the function as exposed in Python. The function must return a new reference.

The function signature is:

PyObject *PyCFunction(PyObject *self,
                      PyObject *args);
							

type PyCFunctionWithKeywords ¶

属于 稳定 ABI (应用程序二进制接口) .

Type of the functions used to implement Python callables in C with signature METH_VARARGS | METH_KEYWORDS . The function signature is:

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

type _PyCFunctionFast ¶

Type of the functions used to implement Python callables in C with signature METH_FASTCALL . The function signature is:

PyObject *_PyCFunctionFast(PyObject *self,
                           PyObject *const *args,
                           Py_ssize_t nargs);
									

type _PyCFunctionFastWithKeywords ¶

Type of the functions used to implement Python callables in C with signature METH_FASTCALL | METH_KEYWORDS . The function signature is:

PyObject *_PyCFunctionFastWithKeywords(PyObject *self,
                                       PyObject *const *args,
                                       Py_ssize_t nargs,
                                       PyObject *kwnames);
										

type PyCMethod ¶

Type of the functions used to implement Python callables in C with signature METH_METHOD | METH_FASTCALL | METH_KEYWORDS . The function signature is:

PyObject *PyCMethod(PyObject *self,
                    PyTypeObject *defining_class,
                    PyObject *const *args,
                    Py_ssize_t nargs,
                    PyObject *kwnames)
											

3.9 版新增。

type PyMethodDef ¶

属于 稳定 ABI (应用程序二进制接口) (including all members).

Structure used to describe a method of an extension type. This structure has four fields:

字段	C 类型	含义
ml_name	const char *	name of the method
ml_meth	PyCFunction	pointer to the C implementation
ml_flags	int	flag bits indicating how the call should be constructed
ml_doc	const char *	points to the contents of the docstring

ml_meth is a C function pointer. The functions may be of different types, but they always return PyObject * . If the function is not of the PyCFunction , the compiler will require a cast in the method table. Even though PyCFunction defines the first parameter as PyObject * , it is common that the method implementation uses the specific C type of the self 对象。

ml_flags field is a bitfield which can include the following flags. The individual flags indicate either a calling convention or a binding convention.

There are these calling conventions:

METH_VARARGS ¶

This is the typical calling convention, where the methods have the type PyCFunction . The function expects two PyObject * values. The first one is the self object for methods; for module functions, it is the module object. The second parameter (often called args ) is a tuple object representing all arguments. This parameter is typically processed using PyArg_ParseTuple() or PyArg_UnpackTuple() .

METH_VARARGS | METH_KEYWORDS

Methods with these flags must be of type PyCFunctionWithKeywords . The function expects three parameters: self , args , kwargs where kwargs is a dictionary of all the keyword arguments or possibly NULL if there are no keyword arguments. The parameters are typically processed using PyArg_ParseTupleAndKeywords() .

METH_FASTCALL ¶

Fast calling convention supporting only positional arguments. The methods have the type _PyCFunctionFast . The first parameter is self , the second parameter is a C array of PyObject * values indicating the arguments and the third parameter is the number of arguments (the length of the array).

3.7 版新增。

3.10 版改变： METH_FASTCALL is now part of the stable ABI.

METH_FASTCALL | METH_KEYWORDS

Extension of METH_FASTCALL supporting also keyword arguments, with methods of type _PyCFunctionFastWithKeywords . Keyword arguments are passed the same way as in the vectorcall protocol : there is an additional fourth PyObject * parameter which is a tuple representing the names of the keyword arguments (which are guaranteed to be strings) or possibly NULL if there are no keywords. The values of the keyword arguments are stored in the args array, after the positional arguments.

3.7 版新增。

METH_METHOD | METH_FASTCALL | METH_KEYWORDS

Extension of METH_FASTCALL | METH_KEYWORDS supporting the defining class , that is, the class that contains the method in question. The defining class might be a superclass of Py_TYPE(self) .

The method needs to be of type PyCMethod , the same as for METH_FASTCALL | METH_KEYWORDS with defining_class argument added after self .

3.9 版新增。

METH_NOARGS ¶

Methods without parameters don’t need to check whether arguments are given if they are listed with the METH_NOARGS flag. They need to be of type PyCFunction . The first parameter is typically named self and will hold a reference to the module or object instance. In all cases the second parameter will be NULL .

The function must have 2 parameters. Since the second parameter is unused, Py_UNUSED can be used to prevent a compiler warning.

METH_O ¶

Methods with a single object argument can be listed with the METH_O flag, instead of invoking PyArg_ParseTuple() 采用 "O" argument. They have the type PyCFunction ，采用 self 参数，和 PyObject * parameter representing the single argument.

These two constants are not used to indicate the calling convention but the binding when use with methods of classes. These may not be used for functions defined for modules. At most one of these flags may be set for any given method.

METH_CLASS ¶

The method will be passed the type object as the first parameter rather than an instance of the type. This is used to create class methods , similar to what is created when using the classmethod() 内置函数。

METH_STATIC ¶

The method will be passed NULL as the first parameter rather than an instance of the type. This is used to create static methods , similar to what is created when using the staticmethod() 内置函数。

One other constant controls whether a method is loaded in place of another definition with the same method name.

METH_COEXIST ¶

The method will be loaded in place of existing definitions. Without METH_COEXIST , the default is to skip repeated definitions. Since slot wrappers are loaded before the method table, the existence of a sq_contains slot, for example, would generate a wrapped method named __contains__() and preclude the loading of a corresponding PyCFunction with the same name. With the flag defined, the PyCFunction will be loaded in place of the wrapper object and will co-exist with the slot. This is helpful because calls to PyCFunctions are optimized more than wrapper object calls.

访问扩展类型的属性 ¶

type PyMemberDef ¶

属于 稳定 ABI (应用程序二进制接口) (including all members).

Structure which describes an attribute of a type which corresponds to a C struct member. Its fields are:

字段	C 类型	含义
name	const char *	name of the member
type	int	the type of the member in the C struct
offset	Py_ssize_t	the offset in bytes that the member is located on the type’s object struct
flags	int	flag bits indicating if the field should be read-only or writable
doc	const char *	points to the contents of the docstring

type can be one of many T_ macros corresponding to various C types. When the member is accessed in Python, it will be converted to the equivalent Python type.

Macro name	C 类型
T_SHORT	short
T_INT	int
T_LONG	long
T_FLOAT	float
T_DOUBLE	double
T_STRING	const char *
T_OBJECT	PyObject *
T_OBJECT_EX	PyObject *
T_CHAR	char
T_BYTE	char
T_UBYTE	unsigned char
T_UINT	无符号 int
T_USHORT	unsigned short
T_ULONG	unsigned long
T_BOOL	char
T_LONGLONG	long long
T_ULONGLONG	unsigned long long
T_PYSSIZET	Py_ssize_t

T_OBJECT and T_OBJECT_EX differ in that T_OBJECT 返回 None if the member is NULL and T_OBJECT_EX 引发 AttributeError . Try to use T_OBJECT_EX over T_OBJECT 因为 T_OBJECT_EX handles use of the del statement on that attribute more correctly than T_OBJECT .

flags 可以是 0 for write and read access or READONLY for read-only access. Using T_STRING for type 隐含 READONLY . T_STRING data is interpreted as UTF-8. Only T_OBJECT and T_OBJECT_EX members can be deleted. (They are set to NULL ).

Heap allocated types (created using PyType_FromSpec() or similar), PyMemberDef may contain definitions for the special members __dictoffset__ , __weaklistoffset__ and __vectorcalloffset__ , corresponding to tp_dictoffset , tp_weaklistoffset and tp_vectorcall_offset in type objects. These must be defined with T_PYSSIZET and READONLY ，例如：

static PyMemberDef spam_type_members[] = {
    {"__dictoffset__", T_PYSSIZET, offsetof(Spam_object, dict), READONLY},
    {NULL}  /* Sentinel */
};
										

PyObject * PyMember_GetOne ( const char * obj_addr , struct PyMemberDef * m ) ¶

Get an attribute belonging to the object at address obj_addr . The attribute is described by PyMemberDef m 。返回 NULL 当出错时。

int PyMember_SetOne ( char * obj_addr , struct PyMemberDef * m , PyObject * o ) ¶

Set an attribute belonging to the object at address obj_addr to object o . The attribute to set is described by PyMemberDef m 。返回 0 if successful and a negative value on failure.

type PyGetSetDef ¶

属于 稳定 ABI (应用程序二进制接口) (including all members).

Structure to define property-like access for a type. See also description of the PyTypeObject.tp_getset 槽。

字段	C 类型	含义
名称	const char *	attribute name
get	getter	C function to get the attribute
set	setter	optional C function to set or delete the attribute, if omitted the attribute is readonly
doc	const char *	optional docstring
closure	void *	optional function pointer, providing additional data for getter and setter

get function takes one PyObject * parameter (the instance) and a function pointer (the associated closure ):

typedef PyObject *(*getter)(PyObject *, void *);
											

It should return a new reference on success or NULL with a set exception on failure.

set functions take two PyObject * parameters (the instance and the value to be set) and a function pointer (the associated closure ):

typedef int (*setter)(PyObject *, PyObject *, void *);
											

In case the attribute should be deleted the second parameter is NULL . Should return 0 当成功时或 -1 with a set exception on failure.

内容表

• 通用对象结构
  • 基对象类型和宏
  • 实现函数和方法
  • 访问扩展类型的属性

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