Calling a Python Script using C++ in QT Creator

Question

I have a Python script that takes three folders as input. I am trying to create a GUI in which I browse for the three folder locations, then call the Python script with those as parameters. I've already create the GUI and can browse for the folder locations, but I seem to have problems calling the Python script using either QProcess or Python.h.

QProcess:

QString arg1 = ui->folder1->text();
QString arg2 = ui->folder2->text();
QString arg3 = ui->folder3->text();

QProcess p;
QString script = "python script.py";
QStringList params;

params << arg1 << arg2 << arg3;
p.start(script, params);
p.waitForFinished(-1);

QString p_stdout = p.readAll();
ui->displayOutput->setText(p_stdout);

Python.h:

QString arg1 = ui->folder1->text();
QString arg2 = ui->folder2->text();
QString arg3 = ui->folder3->text();

const char* args1 = arg1.toUtf8().constData();
const char* args2 = arg2.toUtf8().constData();
const char* args3 = arg3.toUtf8().constData();

PyObject *pName, *pModule, *pDict, *pFunc, *pValue, *pResult, *pArgs;

// Initialize Python Interpreter
Py_Initialize();

// Convert python script's name into Python string
pName = PyString_FromString("script");

// Import the file as a Python module
pModule = PyImport_Import(pName);

// Create a dictionary for the contents of the module
pDict = PyModule_GetDict(pModule);

// Arguments
pArgs = PyTuple_New(3);
PyTuple_SetItem(pArgs, 0, PyString_FromString(args1));
PyTuple_SetItem(pArgs, 1, PyString_FromString(args2));
PyTuple_SetItem(pArgs, 2, PyString_FromString(args3));

pFunc = PyDict_GetItemString(pDict, "main");

pResult = PyObject_CallObject(pFunc, pArgs);

Py_Finalize();

I will say that when I do run the Python.h in either debug or Release, the program crashes when I press the button to run the code. Is there a better way to run either code without running into issues?

Edit: It is able to run without arguments using the QProcess method, yet will not run when I include the arguments, which are folder paths. I made a function to put quotations to those folders that have whitespace in them, but it still won't run. Is there a way to pass in the folders as parameters so that the Python script can run?

You should specify the path where the script lies. QProceas gives such a possibility. Also an empty space in the scripts name requires maybe a backslash. — Cristi
– Cristi, Commented Jan 31, 2017 at 15:02
When I use the QProcess method, nothing happens, as if the button has no code. I don't know if I'm missing anything else. — Anthony Reid
– Anthony Reid, Commented Jan 31, 2017 at 15:23
I don't think it finds the path to your script. See my first comment. Have you tried QProcess::SetWorkingDirectory ? — Cristi
– Cristi, Commented Jan 31, 2017 at 15:40
That works, but now I believe the issue is that the folders that have spaces in them is causing it to not run. — Anthony Reid
– Anthony Reid, Commented Jan 31, 2017 at 16:18

Anthony Reid · Accepted Answer · 2017-02-02 14:35:58Z

1

So after trying different methods, this is what works for me on Windows

QString cmd_qt = QString("python %1script.py %2 %3 %4").arg(filename1).arg(filename3).arg(filename4).arg(filename5);
const char* cmd = cmd_qt.toLocal8Bit().constData();
system(cmd);

This just calls the Python function via command prompt. I don't know if this is the most efficient way. but it works for now. If there is a better way, let me know.

answered Feb 2, 2017 at 14:35

Anthony Reid

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Developer · Accepted Answer · 2020-12-02 18:34:57Z

0

QString script = "python "+ "../folder1/script.py;
const char* cmd = script.toLocal8Bit().constData();
system(cmd);

is not reading the content correctly.

The output shows Invalid Test_log directory always.

But when running the python script.py from command line directly gives proper o/p. Thepython path is set in my envionment variable .

 log_dir = '../Test_Logs/'
if not os.path.exists(log_dir):
    print('Invalid Test_log directory')
    exit()

answered Dec 2, 2020 at 18:34

Developer

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