[PyQt] Advices on embedding python in Qt/C++ application

[Alexis Barbot]

Thanks Phil,

I recompiled PyQt5.13 against Qt5.12 mingw32. I had to modify the qmake
generated .pro to add "QMAKE_CXXFLAGE += "-D_hypot=hypot", and add
"-lpython" to "LIBS" to every sub project, but it finally compiled. Now I'm
trying to run an exemple as you said, but it crashes without explainations.
Here is the code sample:

#include <sip.h>
#include <Python.h>
#include <QDateTime>

...

Py_Initialize();
PyImport_ImportModule("sip");
auto sipAPI_QtCore = reinterpret_cast<const
sipAPIDef*>(PyCapsule_Import("PyQt5.sip._C_API", 0));
PyImport_ImportModule("PyQt5.QtCore");
auto type = sipAPI_QtCore->api_find_type("QDateTime");

Could someone confirm me this example should work, please?
Thanks

Alexis

Le jeu. 29 août 2019 à 18:48, Phil Thompson <phil at riverbankcomputing.com> a
écrit :

> On 29/08/2019 17:21, Alexis Barbot wrote:
> > I looked at it, but it seems I didn't catch the point (or possibly the
> > moment I read it I did not figure out it could be what I needed...). I
> > now
> > understand that it explains I should get the c api dynamically to call
> > it,
> > whereas I was trying to call static method. I could get something
> > roughtly
> > working this way, with pyqt compiled in static (see code below). I'm
> > currently trying to clean everythind, but I realized I had to upgrade
> > Qt
> > for that, as I can't find a PyQt package for Qt5.9 (sad, as it's a
> > LTS). So
> > I'll keep you updated on my progress.
>
> See...
>
>
> https://www.riverbankcomputing.com/static/Docs/PyQt5/installation.html#understanding-the-correct-version-to-install
>
> > In my tests I realized something: is there some special care to do with
> > containers while passing from C++/python? In my first attemp to pass a
> > QVariantMap the items added after SetItem to python are not visible
> > from
> > python? (and items modified in python are not modified in c++). Any
> > special
> > thoughts about this?
>
> Impossible to say without example code.
>
> > Thanks for all your help
> >
> > Alexis
> >
> > ```
> > Py_Initialize();
> > PyEval_InitThreads();
>
> The following code...
>
> > auto sipModule = PyImport_ImportModule("sip");
> > PyImport_ImportModule("PyQt5.sip");
> > auto sipAPI = (const sipAPIDef*)PyCapsule_Import("sip._C_API", 0);
> > PyCapsule_Import("PyQt5.QtCore._C_API", 0);
> > auto sipModuleDict = PyModule_GetDict(sipModule);
> > auto sip_sipmod = PyImport_ImportModule("PyQt5.sip");
> > auto sip_capiobj = PyDict_GetItemString(PyModule_GetDict(sip_sipmod),
> > "_C_API");
> >
> > sipAPI_QtCore = reinterpret_cast<const
> > sipAPIDef*>(PyCapsule_GetPointer(sip_capiobj, "PyQt5.sip._C_API"));
> > qpycore_init();
> > sipExportModule(&sipModuleAPI_QtCore, SIP_API_MAJOR_NR,
> > SIP_API,MINOR_NR,
> > 0);
>
> ...only needs to be...
>
> sipAPI_QtCore = reinterpret_cast<const
> sipAPIDef*>(PyCapsule_Import("PyQt5.sip._C_API", 0));
> PyImport_ImportModule("PyQt5.QtCore")
>
> ...but I haven't actually tested it.
>
> > auto m = PyImport_AddModule("__main__");
> > auto g = PyModule_GetDict(m);
> > auto d = PyDictNew();
> >
> > auto test = std::make_unique<QDateTIme>(QDateTIme::currentDateTime);
> > auto type = sipAPI_QtCore->api_find_type("QDateTime);
> > auto pyTest = sipAPI_QtCore->api_convert_from_type(test.get(), type,
> > nullptr);
> > // Ici je visualise l'objet C++ en python
> > PyDict_SetItem(d, PyUnicode_FromString("testdate"), Py_file_input, g,
> > d);
> > PyRun_String("print(testdate.toString())", Py_file_input, g, d);
> > test->setDate(QDate{2000,02,03});
> > // Ici je visualise en python que l'objet a été modifié en c++
> > PyDict_SetItem(d, PyUnicode_FromString("testdate"), Py_file_input, g,
> > d);
> > Py_FinalizeEx();
> > ```
>
> Make sure you aren't #including sipAPIQtCore.h. Those files are internal
> and contain nothing public.
>
> Phil
>
>
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