problem with python in c++ (boost::python)

[aquavitae]

I'm having trouble using boost::python. This is my code:

int main(int argc, char *argv[]) {
Py_Initialize();
dict globals;
globals["a"] = 4;

try {
object result = eval(str(QString("a+3").toStdString()), globals);
} catch (error_already_set const &) {
PyErr_Print();
}
return 0;
}


and this is the error I get when I run it:

Traceback (most recent call last):
File "<string>", line 1, in <module>
TypeError: 'NoneType' object is unsubscriptable

Can anyone help?

[kripkenstein]

I am having the exact same problem... did you perhaps figure it out meanwhile? Or can someone else help us out here?

[catchmeifyoutry]

I'm having trouble using boost::python. This is my code:

int main(int argc, char *argv[]) {
Py_Initialize();
dict globals;
globals["a"] = 4;

try {
object result = eval(str(QString("a+3").toStdString()), globals);
} catch (error_already_set const &) {
PyErr_Print();
}
return 0;
}


and this is the error I get when I run it:

Traceback (most recent call last):
File "<string>", line 1, in <module>
TypeError: 'NoneType' object is unsubscriptable

Can anyone help?


Try something like this?

#include <boost/python.hpp>
#include <iostream>

// compiled as: g++ python.cpp -o p -lpython2.5 -lboost_python -I /usr/include/python2.5

using namespace boost::python;

int main(int argc, char *argv[])
{
Py_Initialize();

try {
object main_module = import("__main__");
object main_namespace = main_module.attr("__dict__");

dict globals;
globals["a"] = 4;
object result = eval(str(std::string("a+3")), main_namespace, globals);
std::cout << extract<int>(result) << std::endl;

} catch (error_already_set const &) {
PyErr_Print();
}
return 0;
}



Documentation with examples on:
http://www.boost.org/doc/libs/1_35_0/libs/python/doc/v2/exec.html

For me this works, but I've take out the QString part ...
cheers.

[kripkenstein]

catchmeifyoutry, your code worked, and I think I figured it out. It seems that calling eval() with three parameters is fine, as you did, but with only two - as in the tutorial examples - doesn't work (even though it compiles fine).

Thanks!

[catchmeifyoutry]

catchmeifyoutry, your code worked, and I think I figured it out. It seems that calling eval() with three parameters is fine, as you did, but with only two - as in the tutorial examples - doesn't work (even though it compiles fine).

Thanks!

Sweet!
no problem.