How do I pass a variable through Python using C++ in Python.h

Question

I wanted to try out embedding Python into C++. I was able to get that to work but I wanted to start writing prints with variables which are in declared in c++. For example:

(C++)

int num = 43;
PyRun_SimpleString("print("+num+")");

char g;
std::cin>>g;
PyRun_SimpleString("print("+g+")");

I tried to figure out how to use other related functions, but I don't seen to find enough information.

Sin Han Jinn · Accepted Answer · 2022-11-24 02:31:10Z

2

To pass char,

Python script:

def test(person):
    return "Hello " + person;

C++:

PyObject *pName, *pModule, *pFunc, *pArgs, *pValue;
pName = PyUnicode_FromString((char*)"script");
pModule = PyImport_Import(pName);
pFunc = PyObject_GetAttrString(pModule, (char*)"test");
pArgs = PyTuple_Pack(1, PyUnicode_FromString((char*)"User"));
pValue = PyObject_CallObject(pFunc, pArgs);
auto result = _PyUnicode_AsString(pValue);
std::cout << result << std::endl;

Output:

Hello User

To pass integer it's the same like above. Here you are passing over double 2.0.

pArgs = PyTuple_Pack(1,PyFloat_FromDouble(2.0));
pValue = PyObject_CallObject(pFunc, pArgs);

You can refer to all the apis here >> https://docs.python.org/3/c-api/

edited Nov 24, 2022 at 2:31

answered Nov 24, 2022 at 2:24

Sin Han Jinn

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14 Comments

user20342224 Over a year ago

If you don't mind me asking but how would you use this? I'm not at all familiar with this.

Sin Han Jinn Over a year ago

I updated my code from initialization up till receiving results so it's easier. since you can run pyrunsimplestring, means your embedding has no issues. "script" is the name of your python file, script.py. while "test" is your function name. you can try it to understand

user20342224 Over a year ago

Thanks, but I'm running into an access violation reading location. Its being caused on the pFunc line. I set the py file; do I have to do anything with the module?

Sin Han Jinn Over a year ago

The pFunc line is loading the script. means possibly it's not able to find your script. make sure the naming is correct and the script location is within your environment. you can test it by adding the script on the same directory of your c++ exe OR you can set environment variable PATH for your user/admin to wherever your python file directory is.

user20342224 Over a year ago

Yes, I have my py file inside of the same folder location as my cpp file.

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