深入源码解析Python中的对象与类型

/* PyObject_HEAD defines the initial segment of every PyObject. */
#define PyObject_HEAD          \
  _PyObject_HEAD_EXTRA        \
  Py_ssize_t ob_refcnt;        \
  struct _typeobject *ob_type;

 typedef struct _object {
   PyObject_HEAD
 } PyObject;

typedef struct {
  PyObject_VAR_HEAD
} PyVarObject;

#define PyObject_VAR_HEAD        \
 PyObject_HEAD            \
 Py_ssize_t ob_size; /* Number of items in variable part */

>>> a = 1
>>> a
1

>>> type(a)
<type 'int'>

#等价的两个
>>> type(type(a))
<type 'type'>
>>> type(int)
<type 'type'>

#还是等价的两个
>>> type(type(type(a)))
<type 'type'>
>>> type(type(int))
<type 'type'>

typedef struct _typeobject {

 /* MARK: base, 注意, 是个变长对象*/
 PyObject_VAR_HEAD
 const char *tp_name; /* For printing, in format "<module>.<name>" */ //类型名
 Py_ssize_t tp_basicsize, tp_itemsize; /* For allocation */ // 创建该类型对象时分配的内存空间大小


 // 一堆方法定义, 函数和指针
 /* Methods to implement standard operations */
 printfunc tp_print;
 hashfunc tp_hash;

 /* Method suites for standard classes */
 PyNumberMethods *tp_as_number;  // 数值对象操作
 PySequenceMethods *tp_as_sequence; // 序列对象操作
 PyMappingMethods *tp_as_mapping; // 字典对象操作

 // 一堆属性定义
 ....

} PyTypeObject;

PyTypeObject PyType_Type = {
 PyVarObject_HEAD_INIT(&PyType_Type, 0)
 "type",                   /* tp_name */
 sizeof(PyHeapTypeObject),          /* tp_basicsize */
 sizeof(PyMemberDef),            /* tp_itemsize */
 (destructor)type_dealloc,          /* tp_dealloc */

 // type对象的方法和属性初始化值
 .....

};

# 1. int 的 类型 是`type`
>>> type(int)
<type 'type'>

# 2. type 的类型 还是`type`, 对应上面说明第二点
>>> type(type(int))
<type 'type'>

PyTypeObject PyInt_Type = {
 PyVarObject_HEAD_INIT(&PyType_Type, 0)
 "int",
 sizeof(PyIntObject),
 0,

 // int类型的相关方法和属性值
 ....

 (hashfunc)int_hash,             /* tp_hash */

};

  *ob_type = &PyType_Type

>>> type(1)
<type 'int'>

>>> type(type(1))
<type 'type'>

typedef struct {
  PyObject_HEAD
  long ob_ival;
} PyIntObject;