PyQt script under C++ Qt doesn't work under Windows.

david_qt · wrote on 5 Mar 2020, 19:53

I'm trying to run a Python (PyQt) script under a Qt C++ applciation. This script works fine from console (linux) and cmd (windows 10).

This is the script:

plugin_loader.py

#!/usr/bin/python
# -*- coding: utf-8 -*-

import imp
import os
import sys
import operator
from PyQt5 import QtCore, QtGui, QtWidgets, QtSql
from DialogoImprimir import DialogoImprimir

if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    myapp = DialogoImprimir()
    myapp.show()
    sys.exit(app.exec_())


def iniciar(*datos):
    app = QtWidgets.QApplication.instance()
    print (app)
    if app is None:
        app = QtWidgets.QApplication([])
    myapp = DialogoImprimir()
    myapp.show()
    return myapp.exec_()

DialogoImprimir.py

#!/usr/bin/python
# -*- coding: utf-8 -*-

MainModule = "__init__"

import sys
import imp
import os

from PyQt5 import QtCore, QtGui, QtWidgets

class DialogoImprimir(QtWidgets.QDialog):
    def __init__(self):
        QtWidgets.QDialog.__init__(self)        
        self.GeneraUI()     

    def GeneraUI(self):
        self.setObjectName("Dialog")
        self.resize(200, 293)       
        self.buttonBox = QtWidgets.QDialogButtonBox(self)
        self.buttonBox.setOrientation(QtCore.Qt.Horizontal)
        self.buttonBox.setStandardButtons(QtWidgets.QDialogButtonBox.Cancel|QtWidgets.QDialogButtonBox.Ok)
        self.buttonBox.setObjectName("buttonBox")       
        self.retranslateUi()
        #acciones       
        self.buttonBox.accepted.connect(self.accept)
        self.buttonBox.rejected.connect(self.reject)
        QtCore.QMetaObject.connectSlotsByName(self)

    def retranslateUi(self):
        _translate = QtCore.QCoreApplication.translate

main.cpp

#include "mainwindow.h"    
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

mainwindows.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private:
    Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H

mainwindows.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "./pyrun.h"
#include <QDebug>
#include <QDir>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    QString pathPython = "/.pruebapython";
    QString pRuta = QDir::homePath()+pathPython;
    QString pModulo = "plugin_loader";
    QString pFuncion = "iniciar";
    QStringList pArgumentos;
    pArgumentos<<"1"<<"2"<<"3"<<"4";
    int res = ::PyRun::loadModule(QDir::home().absoluteFilePath(pRuta),pModulo, pFuncion, pArgumentos);
    qDebug()<<"Resultado: "<<res;
}

MainWindow::~MainWindow()
{
    delete ui;
}

pyrun.h

#ifndef PYRUN_H
#define PYRUN_H


//se crea un entorno para cargar modulos en python

#include <QString>
#include <QStringList>

namespace PyRun
{
enum State
{
    PythonUninitialized,
    PythonInitialized,
    AppModuleLoaded
};
enum Resultado
{
    CannotLoadModule,
    CannotConvertArgument,
    CallFailed,
    CannotFindFunction,
    FailedToLoad,
    Success
};

int loadModule(const QString &modulePath, const QString &moduleName, const QString &functionName, const QStringList &args);
State init();
}
#endif // PYRUN_H

pyrun.cpp

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

#include <QByteArray>
#include <QCoreApplication>
#include <QDebug>

namespace PyRun
{
static State state = PythonUninitialized;

static void cleanup()
{
    if (state > PythonUninitialized) {
        Py_Finalize();
        state = PythonUninitialized;
    }
}

int loadModule(const QString &modulePath, const QString &moduleName, const QString &functionName, const QStringList& args)
{
    qDebug()<<"modulepath"<<modulePath;
    qputenv("PYTHONPATH", modulePath.toLocal8Bit());
    if (init() != AppModuleLoaded)
        //return false;
        return CannotLoadModule;
    PyObject *pName, *pModule, *pFunc;
    PyObject *pArgs, *pValue;
    pName = PyUnicode_DecodeFSDefault(moduleName.toLocal8Bit().constData());
    /* Error checking of pName left out */
    pModule = PyImport_Import(pName);
    Py_DECREF(pName);
    if (pModule)
    {
        pFunc = PyObject_GetAttrString(pModule, functionName.toLocal8Bit().constData());
        /* pFunc is a new reference */
        if (pFunc && PyCallable_Check(pFunc))
        {
            /* pValue reference stolen here: */
            pArgs = PyTuple_New(args.size());
            for (int i = 0;i<args.size();i++)
            {
                PyObject* arg_valor = Py_BuildValue("s",args.at(i).toLocal8Bit().constData());
                if (!arg_valor)
                {
                    Py_DECREF(pArgs);
                    Py_DECREF(pModule);
                    qWarning("Cannot convert argument\n");
                    //return false;
                    return  CannotConvertArgument;
                }
                PyTuple_SetItem(pArgs, i, arg_valor);//meto los datos de conexion
            }
            pValue = PyObject_CallObject(pFunc, pArgs);
            Py_DECREF(pArgs);
            if (pValue){
                qWarning("Result of call: %ld\n", PyLong_AsLong(pValue));
                Py_DECREF(pValue);
            }
            else
            {
                Py_DECREF(pFunc);
                Py_DECREF(pModule);
                PyErr_Print();
                qWarning("Call failed\n");
                //return false;
                return  CallFailed;
            }
        }
        else
        {
            if (PyErr_Occurred())
                PyErr_Print();
            qWarning("Cannot find function \"%s\"\n", functionName.toLocal8Bit().constData());
        }
        Py_XDECREF(pFunc);
        Py_DECREF(pModule);
    }
    else
    {
        PyErr_Print();
        qWarning("Failed to load \"%s\"\n", moduleName.toLocal8Bit().constData());        
        //return false;
        return FailedToLoad;
    }
    //return true;
    return Success;
}

State init()
{
    if (state > PythonUninitialized)
        return state;
    QByteArray virtualEnvPath = qgetenv("VIRTUAL_ENV");
    if (!virtualEnvPath.isEmpty())
        qputenv("PYTHONHOME", virtualEnvPath);
    Py_Initialize();
    qAddPostRoutine(cleanup);
    state = PythonInitialized;
    const bool pyErrorOccurred = PyErr_Occurred() != nullptr;
    if (!pyErrorOccurred) {
        state = AppModuleLoaded;
    } else {
        if (pyErrorOccurred)
            PyErr_Print();
        qWarning("Failed to initialize the module.");
    }
    return state;
}
}

More things....the *.pro file has these lines (in my case):

unix {
    INCLUDEPATH += /usr/include/python3.6m
    LIBS += -L /usr/local/lib/python3.6 -lpython3.6m
    DEPENDPATH +=  /usr/include/python3.6m
}

win32 {
    INCLUDEPATH += C:\Python\Python37\include
    LIBS += -L C:\Python\Python37\libs -lpython37
    DEPENDPATH += C:\Python\Python37\include
}

Actually, it is my clumsy version of the answer of this

Well, running the script under linux there aren't any error, but under windows I have a white windows, without buttons or information on. Then the applicatios fails, and I must to force for close it.
I have this message:

QApplication::regClass: Registering window class 'Qt5ClipboardView' failed. (Esta clase ya existe.)

And if I move the mouse over the white window I have these messages:

windowsProc: No Qt Window found for event 0x20 (WM_SETCURSOR), hwnd=0x0xf0470.
windowsProc: No Qt Window found for event 0x200 (WM_MOUSEMOVE), hwnd=0x0xf0470.
windowsProc: No Qt Window found for event 0x84 (WM_NCHITTEST), hwnd=0x0xf0470.
windowsProc: No Qt Window found for event 0x20 (WM_SETCURSOR), hwnd=0x0xf0470.
windowsProc: No Qt Window found for event 0x200 (WM_MOUSEMOVE), hwnd=0x0xf0470.
windowsProc: No Qt Window found for event 0x84 (WM_NCHITTEST), hwnd=0x0xf0470.
windowsProc: No Qt Window found for event 0x20 (WM_SETCURSOR), hwnd=0x0xf0470.
windowsProc: No Qt Window found for event 0x200 (WM_MOUSEMOVE), hwnd=0x0xf0470.
windowsProc: No Qt Window found for event 0x84 (WM_NCHITTEST), hwnd=0x0xf0470.
windowsProc: No Qt Window found for event 0x20 (WM_SETCURSOR), hwnd=0x0xf0470.
windowsProc: No Qt Window found for event 0x200 (WM_MOUSEMOVE), hwnd=0x0xf0470.
windowsProc: No Qt Window found for event 0x6 (WM_ACTIVATE), hwnd=0x0xf0470.
windowsProc: No Qt Window found for event 0x1c (WM_ACTIVATEAPP), hwnd=0x0xf0470.
windowsProc: No Qt Window found for event 0x8 (WM_KILLFOCUS), hwnd=0x0xf0470.

Sorry about my poor english.
Thank you!