Question

我使用c ++来控制python 2.7，但调用该方法并没有向我返回正确的值。而且，代替参数5，方法得到1 - 为什么会这样呢？

PyObject * ws = PyImport_ImportModule("cppMethods"); //cppMethods.py
PyObject* klass = PyObject_GetAttrString(ws, "cppMethods"); //class
PyObject* instance = PyInstance_New(klass, NULL, NULL);
//call_method<int>(instance, "getSum", 1);
PyObject* result = PyObject_CallMethod(instance, "getSum", "i", 5);
auto res3 = PyInt_AsLong(result); //-1 here

class cppMethods():

    def getSum(self, a):
        print("This line will be printed.");
        print("a=",a);
        number = a + 3;
        print("number=",number);
        return number;

Answer 1

用于PyObject_CallMethod的格式字符串应该产生一个元组。 You need to parenthesize the string contents当只有一个值时强制一个元组：

PyObject_CallMethod(instance, "getSum", "(i)", 5)

Answer 2

这是怎么回事：

object module = import("cppMethods");
object _class = module.attr("cppMethods")();
auto res = _class.attr("getSum")(5);
int x = extract<int>(res);

PyObject_CallMethod返回-1

2 个答案: