[PyQt] Problems building PyQt with Python 3.8.1 on Windows

[Phil Thompson]

On 04/02/2020 10:48, Boudewijn Rempt wrote:
> Hi,
> 
> I embed Python and PyQt in my C++ application, Krita. Since I updated 
> the
> version of Python from 3.6 to 3.8.1, PyQt doesn't get built correctly
> anymore. My version of Qt is 5.12.5 and I build Qt myself because it 
> needs
> a lot of patching. The whole build system for the dependencies is setup
> using cmake external projects. I build using mingw 7.3.
> 
> I build sip 4.19.21 with the following options ($PREFIX_ext_sip points 
> to
> c:\dev\i_deps, the place where I install all dependencies when 
> building):
> 
>         --platform win32-g++
>         -b ${PREFIX_ext_sip}/bin
>         -d ${PREFIX_ext_sip}/lib/krita-python-libs
>         -e ${PREFIX_ext_sip}/include
>         --sipdir ${PREFIX_ext_sip}/share/sip
>         --target-py-version 3.8
>         --sip-module PyQt5.sip
> 
> I build PyQt 5.13.2 with the following options ($PREFIX_ext_pyqt also
> points to c:\dev\i_deps) :
> 
>         --confirm-license
>         --target-py-version 3.8
>         --bindir ${PREFIX_ext_pyqt}/bin
>         --qt ${PREFIX_ext_pyqt}
>         --qmake ${PREFIX_ext_pyqt}/bin/qmake.exe
>         --sip ${PREFIX_ext_pyqt}/bin/sip.exe
>         --sip-incdir ${PREFIX_ext_pyqt}/include
>         --spec win32-g++
>         --verbose
>         --sipdir ${PREFIX_ext_pyqt}/share/sip
>         --destdir ${PREFIX_ext_pyqt}/lib/krita-python-libs
>         --stubsdir ${PREFIX_ext_pyqt}/lib/krita-python-libs/PyQt5
>         --no-qml-plugin --no-python-dbus --no-qsci-api --no-tools
>         --disable QtSql --disable QtTest --disable QtWinExtras 
> --disable
> QtHelp
>         --qmake ${PREFIX_ext_pyqt}/bin/qmake.exe
> 
> I tried adding
> 
>         --assume-shared
>         --link-full-dll
> 
> But that doesn't make a difference.
> 
> When I add the installation location of PyQt5 to PYTHONPATH and the
> location of the Qt dll's to PATH, and start Python manually and try to
> import PyQt5, PyQt5.Qt or PyQt5.sip, python doesn't complain. If I try 
> to
> import any of the other modules, like QtCore or QtGui, python says it
> cannot find the module:
> 
> c:\dev\krita>python
> Python 3.8.1 (tags/v3.8.1:1b293b6, Dec 18 2019, 23:11:46) [MSC v.1916 
> 64
> bit (AMD64)] on win32
> Type "help", "copyright", "credits" or "license" for more information.
>>>> import PyQt5
>>>> import PyQt5.Qt
>>>> import PyQt5.QtCore
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
> ImportError: DLL load failed while importing QtCore: The specified 
> module
> could not be found.
> 
> However, the PyQt5 folder does contain all pyd and pyi files:
> 
> c:\dev\b\ext_pyqt>explorer c:\dev\i_deps\bin
> 
> c:\dev\b\ext_pyqt>dir c:\dev\i_deps\lib\krita-python-libs\PyQt5
>  Volume in drive C is Windows
>  Volume Serial Number is D4C3-2B56
> 
>  Directory of c:\dev\i_deps\lib\krita-python-libs\PyQt5
> 
> 02/04/2020  10:08 AM    <DIR>          .
> 02/04/2020  10:08 AM    <DIR>          ..
> 02/04/2020  10:08 AM            15,872 Qt.pyd
> 02/04/2020  09:58 AM         3,244,544 QtCore.pyd
> 02/04/2020  09:55 AM           399,711 QtCore.pyi
> 02/04/2020  10:02 AM         3,274,240 QtGui.pyd
> 02/04/2020  09:55 AM           404,714 QtGui.pyi
> 02/04/2020  10:02 AM           735,232 QtMultimedia.pyd
> 02/04/2020  09:55 AM            86,315 QtMultimedia.pyi
> 02/04/2020  10:03 AM           154,624 QtMultimediaWidgets.pyd
> 02/04/2020  09:55 AM             4,672 QtMultimediaWidgets.pyi
> 02/04/2020  10:03 AM           935,936 QtNetwork.pyd
> 02/04/2020  09:55 AM           101,531 QtNetwork.pyi
> 02/04/2020  10:03 AM           158,208 QtOpenGL.pyd
> 02/04/2020  09:56 AM            15,984 QtOpenGL.pyi
> 02/04/2020  10:03 AM           340,992 QtPrintSupport.pyd
> 02/04/2020  09:56 AM            20,347 QtPrintSupport.pyi
> 02/04/2020  10:04 AM           808,448 QtQml.pyd
> 02/04/2020  09:56 AM            28,079 QtQml.pyi
> 02/04/2020  10:05 AM         1,534,976 QtQuick.pyd
> 02/04/2020  09:56 AM            63,260 QtQuick.pyi
> 02/04/2020  10:08 AM            75,776 QtQuickWidgets.pyd
> 02/04/2020  09:56 AM             4,790 QtQuickWidgets.pyi
> 02/04/2020  10:05 AM           140,800 QtSvg.pyd
> 02/04/2020  09:56 AM             6,053 QtSvg.pyi
> 02/04/2020  10:07 AM         6,849,024 QtWidgets.pyd
> 02/04/2020  09:56 AM           513,480 QtWidgets.pyi
> 02/04/2020  10:08 AM           293,376 QtXml.pyd
> 02/04/2020  09:56 AM            28,207 QtXml.pyi
> 02/03/2020  12:20 PM           116,736 sip.pyd
> 03/19/2019  02:25 PM             2,801 sip.pyi
> 02/04/2020  10:08 AM    <DIR>          uic
> 02/04/2020  10:08 AM           260,608 _QOpenGLFunctions_2_0.pyd
> 02/04/2020  10:08 AM           262,144 _QOpenGLFunctions_2_1.pyd
> 02/04/2020  10:08 AM           139,264 _QOpenGLFunctions_4_1_Core.pyd
> 03/19/2019  02:43 PM               826 __init__.py
> 02/04/2020  10:09 AM    <DIR>          __pycache__
>               33 File(s)     21,021,570 bytes
>                4 Dir(s)  65,477,173,248 bytes free
> 
> I'm not sure what's going -- the way I build PyQt hasn't changed for 
> ages
> and it used to work...

I'd start by using the standard DLL inspection tools (like Dependency 
Walker) on QtCore.pyd to see what's missing.

Is the only change the version of Python?

Phil