[C++-sig] How to get output from python embedded in VC++

[Horváth Imre István]

Hi John!

If you want to embed python in c++ app and exchange data between c++ and
python, take a look at the boost::python library.
It's also a platform independent solution (my app's target platforms are
windows vs2015 and linux CentOS7).

You can do something like this:

    using namespace boost::python;
    Py_Initialize();
    try {
        boost::python::object main_module =
boost::python::import("__main__");
        boost::python::object main_namespace =
main_module.attr("__dict__");

        boost::python::dict mydata;
        mydata["x"] = 5;
        mydata["foo"] = boost::python::dict();
        mydata["foo"]["bar1"] = "data1";
        mydata["foo"]["bar2"] = "data2";

        // you can declare variables in the python namespace from c++
        main_namespace["mydata"] = mydata;

        // in the script there is a mydata variable: {'x': 5, 'foo':
{'bar1': 'data1', 'bar2': 'data2'}}
        boost::python::object ignored = exec_file("script.py",
main_namespace, main_namespace);
        
        // declare a variable named return_value in the script, 
        // and you can extract it's value to c++ like this
        std::wstring output =
extract<std::wstring>(main_namespace["return_value"]);

    } catch( boost::python::error_already_set) {
        PyErr_Print();
    }

(If your python script has some output, don't forget to redirect boost
std::cout etc)

Best regards:
Imre


2017. 07. 20, csütörtök keltezéssel 11.25-kor Jian ezt írta:
> Dear Gurus,
> 
> I want to embed python interpreter in my program. What I want is to
> redirect those output to a control such as RICHEDIT which can be
> modified as a output window in my program. So I can write *.py files
> outside of program and invoke it inside program as a script file. In
> order to get information output by the *.py file I need to get the
> stdin&stdout. I have tried some workflow but not perfect.
> 
> 1). I have tried use Allocconsle(). But I can only get the output info
> printed by std::out & printf() in the current code. all things which
> are printed by python35.dll are missing. I used print('xxxx') in the
> *.py file to test the output. Those *.py files are OK in command line
> mode.
> 
> 2). I also tried to derive class basic_streambuf and overwrite the
> in/out functions. It works only for output from std::out. Text from
> printf() as well as from dlls are missing.
> 
> 3). then I tried to use linker settings as below. 
> 
> #pragma comment( linker,
> "/subsystem:console /entry:wWinMainCRTStartup" )
> 
> A cmd window is created along with the program. everything output from
> current process and dlls are retrieved successfully as I want. But the
> cmd window is not easy to control.
> 
> Is there a better way for this purpose? 
> 
> Thanks in advance for your kind help.
> 
> Best Regards,
> 
> John. 
> 
> 
> 
> 
>  
> 
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