为 Python 写一个 C++ 扩展模块( 三 ) _Python

PyObject *MyClass_new(PyTypeObject *type, PyObject *args, PyObject *kwds){
std::cout << "MtClass_new() called!" << std::endl;
MyClassObject *self;
self = (MyClassObject*) type->tp_alloc(type, 0);
if(self != NULL){ // -> 分配成功
// 赋初始值
self->m_value = https://www.isolves.com/it/cxkf/yy/Python/2023-01-03/0;
self->m_myclass = NULL;
}
return (PyObject*) self;
}

实际的初始化发生在MyClass_init中，它对应于 Python 中的 docs.python.org 方法：

int MyClass_init(PyObject *self, PyObject *args, PyObject *kwds){
((MyClassObject *)self)->m_value = https://www.isolves.com/it/cxkf/yy/Python/2023-01-03/123;
MyClassObject* m = (MyClassObject*)self;
m->m_myclass = (MyClass*)PyObject_Malloc(sizeof(MyClass));
if(!m->m_myclass){
PyErr_SetString(PyExc_RuntimeError, "Memory allocation failed");
return -1;
}
try {
new (m->m_myclass) MyClass();
} catch (const std::exception& ex) {
PyObject_Free(m->m_myclass);
m->m_myclass = NULL;
m->m_value = https://www.isolves.com/it/cxkf/yy/Python/2023-01-03/0;
PyErr_SetString(PyExc_RuntimeError, ex.what());
return -1;
} catch(...) {
PyObject_Free(m->m_myclass);
m->m_myclass = NULL;
m->m_value = https://www.isolves.com/it/cxkf/yy/Python/2023-01-03/0;
PyErr_SetString(PyExc_RuntimeError, "Initialization failed");
return -1;
}
return 0;
}

如果你想在初始化过程中传递参数，必须在此时调用 docs.python.org 。简单起见，本例将忽略初始化过程中传递的所有参数。在函数的第一部分中，PyObject指针（self）被强转为MyClassObject类型的指针，以便访问其他成员。此外，还分配了 C++ 类的内存，并执行了构造函数。
注意，为了防止内存泄漏，必须仔细执行异常处理和内存分配（还有释放）。当引用计数将为零时，MyClass_dealloc函数负责释放所有相关的堆内存。在文档中有一个章节专门讲述关于 C 和 C++ 扩展的内存管理。