PyBind11 析构函数未调用？

我有一个c++类包裹着PyBind11。问题是：当Python脚本结束c++ destructor不会被自动调用。这会导致不整齐的退出，因为网络资源需要由析构函数释放。

作为解决方法，有必要显式删除Python反对，但我不明白为什么！

请有人解释一下这里出了什么问题以及如何获得destructor当Python对象被垃圾收集了吗？

Pybind11绑定代码：

py::class_<pcs::Listener>(m, "listener")
    .def(py::init<const py::object &, const std::string &, const std::string &, const std::string &, const std::string &, const std::set<std::string> &, const std::string & , const bool & , const bool & >(), R"pbdoc(
    Monitors network traffic.

    When a desired data source is detected a client instance is connected to consume the data stream.

    Reconstructs data on receipt, like a jigsaw.  Makes requests to fill any gaps.  Verifies the data as sequential.

    Data is output by callback to Python.  Using the method specified in the constructor, which must accept a string argument.
)pbdoc");

在Python中：

#Function to callback
def print_string(str):
    print("Python; " + str)

lstnr = listener(print_string, 'tcp://127.0.0.1:9001', clientCertPath, serverCertPath, proxyCertPath, desiredSources, 'time_series_data', enableCurve, enableVerbose)

#Run for a minute
cnt = 0
while cnt < 60:
    cnt += 1
    time.sleep(1)

#Need to call the destructor explicity for some reason    
del lstnr

所以几年后我通过启用解决了这个问题Python 上下文管理器 https://docs.python.org/3/reference/datamodel.html#context-managers with通过添加支持__enter__ and __exit__方法处理我的PyBind11 https://pybind11.readthedocs.io/en/stable/index.html# code:

py::class_<pcs::Listener>(m, "listener")
.def(py::init<const py::object &, const std::string &, const std::string &, const std::string &, const std::string &, const std::set<std::string> &, const std::string & , const bool & , const bool & >(), R"pbdoc(
    Monitors network traffic.

    When a desired data source is detected a client instance is connected to consume the data stream.
    
    Specify 'type' as 'string' or 'market_data' to facilitate appropriate handling of BarData or string messages.

    Reconstructs data on receipt, like a jigsaw.  Makes requests to fill any gaps.  Verifies the data as sequential.

    Data is output by callback to Python.  Using the method specified in the constructor, which must accept a string argument.
)pbdoc")
.def("__enter__", &pcs::Listener::enter, R"pbdoc(
    Python 'with' context manager support.
)pbdoc")    
.def("__exit__", &pcs::Listener::exit, R"pbdoc(
    Python 'with' context manager support.
)pbdoc");

在C++类中添加相应的函数，如下所示：

//For Python 'with' context manager
auto enter(){std::cout << "Context Manager: Enter" << std::endl; return py::cast(this); }//returns a pointer to this object for 'with'....'as' python functionality
auto exit(py::handle type, py::handle value, py::handle traceback){ std::cout << "Context Manager: Exit: " << type << " " << value << " " << traceback <<  std::endl; }

N.B.

1. 返回的指针值来自enter()对as功能在一个with....as陈述。

2. 参数传递给exit(py::handle type, py::handle value, py::handle traceback)是有用的调试信息。

Python 用法：

with listener(cb, endpoint, clientCertPath, serverCertPath, proxyCertPath, desiredSources, type, enableCurve, enableVerbose):
cnt = 0
while cnt < 10:
    cnt += 1
    time.sleep(1)

Python 上下文管理器现在调用 C++ 对象的析构函数，从而顺利地释放网络资源。