How to call specific Python functions from QT GUI

lfreeman6490

@JonB I made those changes. My .pro file now has

INCLUDEPATH += C:\Python27-32\include
LIBS += -lpython2.7

and then I tried both

#include <Python.h>
#include "Python.h"

along with giving the full path in the include statement, all of them gave me the same error. The error message changes based on what is being included. Instead of it being

Cannot open include file: 'Python27-32/include/Python.h'. No such file or directory

it is

Cannot open include file: 'Python.h'. No such file or directory

JonB

@lfreeman6490
One more time: how could your code error with

Cannot open include file: 'Python27-32/include/Python.h'. No such file or directory

if you no longer have any reference to

#include <Python27-32/include/Python.h>

in your code?

UPDATE
You have now changed your previous post to a different error message, having stated twice you that you got the error message.

lfreeman6490

@JonB As I said, it changed from

Cannot open include file: 'Python27-32/include/Python.h'. No such file or directory

to

Cannot open include file: 'Python.h'. No such file or directory

JonB

@lfreeman6490
No, you did not state that. You stated that the error message was the same. When it was not. Which I then have to deal with....

Please state error messages correctly.

Let's start with: what OS are you on?

lfreeman6490

This post is deleted!

lfreeman6490

@JonB I'm on windows 10
Python 2.7, 32 bit
QTCreator 3.0.1

JonB

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

Either way, it is the same error

No, it is not. It has different text, which I need if I am able to help you. Up to you whether you want help, but I'm not going to spend time when someone says an error is the same when it is different. You might know what's on your screen, I do not.

After you made the change to the .pro file, did you re-run qmake?

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?