Re: [Boost-users] Exposing C++ Instances to Python

Subject: Re: [Boost-users] Exposing C++ Instances to Python
From: Leonhard Weber (lweberk_at_[hidden])
Date: 2010-05-25 10:30:48

Yes, but it seems I'm unable  to see the wood for the trees.

The concrete situation:
Im developing a Interface that supposedly is going to enable AIs being
written in Python for a C/C++ environment. What I get is a pointer to a
Callback Instance I have to deliver to the AI dev (Python side). The
Instance enables the AI dev to ask question about the Applications state so
the AI reacts accordingly. Now I have a boost::module wrapper for the Class
Im getting a reference of and successfully built a callback so the embedded
Python is able to fetch the Callback Instance coming from the App. But I run
into...

Sandbox:

// The Callback coming from the Application of which I am not allowed to
taint the Source Tree
struct EngineCallback
{
    void setInt(int number) { this->number = number; }
    void setLoop(bool loop) { this->loop = loop; }
    int getInt() { return this->number; }
    bool getLoop() { return this->loop; }

    int number;
    bool loop;
};

EngineCallback* test = new EngineCallback;

// Entrypoint for Python to come ant fetch the Application Callback
shared_ptr<EngineCallback> PyCallback( EngineCallback* &test ) { return
shared_ptr<EngineCallback>(test); } // The Problem? ...how to convert?

// The Wrapper for all this
BOOST_PYTHON_MODULE(EngineCallback)
{
    class_<EngineCallback, shared_ptr<EngineCallback>,
boost::noncopyable>("EngineCallback", no_init)
        .def("setInt", &EngineCallback::setInt)
        .def("setLoop", &EngineCallback::setLoop)
        .def("getInt", &EngineCallback::getInt)
        .def("getLoop", &EngineCallback::getLoop)
    ;

    def("PyCallback", &PyCallback);
}

# test.py
from EngineCallback import PyCallback
from EngineCallback import EngineCallback

test = PyCallback()
dir(test)

>>>>>> ends in:
Traceback (most recent call last):
  File "test.py", line 5, in <module>
    test = PyCallback()
Boost.Python.ArgumentError: Python argument types in
    EngineCallback.PyCallback()
did not match C++ signature:
    PyCallback(EngineCallback* {lvalue})

Conversions in PyCallback missing?, how/with what do I accomplish them?

I think Im having trouble with C/C++ more in general than anything else, but
I would appreciate if you could just point to the things I should look at to
understand and come up with a solution.

Thanks in advance,
lwk

On 25 May 2010 15:40, Steven Watanabe <watanabesj_at_[hidden]> wrote:

> AMDG
>
>
> Leonhard Weber wrote:
>
>> I'm in the same bind  this topic describes:
>> http://lists.boost.org/boost-users/2009/02/44749.php
>> Unfortunately the subject didn't tell about the resolution or approach he
>> took to succeed. Can anyone help me?
>>
>> Basically: I want to expose a C++ Instance to Python at runtime. I have a
>> pointer to the Instance and need to expose that instance to Python.
>>
>>
>
> Have you tried the Boost.Python documentation?
> http://www.boost.org/libs/python/
>
> In Christ,
> Steven Watanabe
>
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