How to call specific Python functions from QT GUI

[lfreeman6490]

@JonB Yes I did run QMake, it's now telling me

LNK1104: cannot open file 'python27_d.lib'

[JonB]

@lfreeman6490
So when you ran qmake the include error went away?

You are now in the link situation I described. You'd better tell the linker, via the .pro file, where to look for the python27_d.lib it is seeking from your LIBS += -lpython2.7 .... (Though I don't think from the error mesaage it can come from your LIBS += -lpython2.7.)

[lfreeman6490]

@JonB I do not have a 'python27_d.lib' file in my python download at all, I only have 'python27.lib'. I'm looking where to get one from

[JonB]

@lfreeman6490
The _d suffix looks like it's looking for a debug version of the library, that's all I know.

[lfreeman6490]

For anybody in the future that may come across this. Thanks to @JonB I was able to have in my .pro file

INCLUDEPATH += C:/Python27/include

win32:LIBS += -LC:/Python27/libs -lpython27

and then in my main.cpp file

#ifdef _DEBUG
    #undef _DEBUG
    #include <Python.h>
#else
    #include <Python.h>
#endif

The reason for the if loop is to circumvent the debug python.h file being loaded. By providing both routes the path to 'python.h'

Found from
https://stackoverflow.com/questions/16200997/why-doesnt-include-python-h-work

[JonB]

@lfreeman6490 said in How to call specific Python functions from QT GUI:

Found from
https://stackoverflow.com/questions/16200997/why-doesnt-include-python-h-work

Good spot! That's a nasty one!

For anyone following this link to the stackoverflow topic, you should look at https://stackoverflow.com/a/32425901/489865 answer on that page, not just the accepted solution one.

[lfreeman6490]

@JonB Would you know how should I proceed with my original issue, that is calling specific Python functions. The path I've been trying to down isn't getting me very far. I've been using this so far.

void f_pathloss::on_pb_connect_disconnect_clicked()
{
    PyObject *pName, *pModule, *pDict, *pFunc;
    PyObject *pArgs, *pValue;

    Py_Initialize();

    pName = PyString_FromString((char*)"test_program");
    pModule = PyImport_Import(pName);

    pFunc = PyObject_GetAttrString(pModule, "test_function");

    PyXDECREF(pFunc);
    pValue = PyObject_CallObject(pFunc, pArgs);
}

where 'test_function' is in 'test_program'.py. All that test_function does is return a string that simply says "this is a c++ test". I have seen QProcess mentioned, but that seems to mainly work when you want to run the entire script, not just a single function.

For the code I've pasted above, once the user hits the connect_disconnect_clicked() button, I want to call a function.

[JonB]

@lfreeman6490
I have never done any of this. You show code, which looks reasonable, but say nothing about what happens when you call it, or step through it in debugger? @mrjj linked to an example, it looks similar. You would benefit from some error checking code here.

QProcess is to do with running an external program, or OS command. You can run a whole Python script that way, but I don't think it's what you should be looking at.

[lfreeman6490]

@JonB Well nothing happens when I do it. It builds successfully and launches the GUI, once I click the button nothing happens. There isn't an error thrown at all either. Just wanted to ask and see

[JonB]

@lfreeman6490
So start debugging that function! I take it you actually have a test_function in the test_program, else what do you expect.

Maybe you need the different code in https://sites.northwestern.edu/yihanzhang/2019/08/22/how-to-invoke-python-function-from-c/, I don't know?