PyQt5 on WinPython with mingw

Getting PyQt5 running on WinPython required a lot of tweaking. WinPython (32 bit) 2.7.10.2 comes with mingw. This is installed in E:\WinPython-32bit-2.7.10.2\python-2.7.10\share\mingwpy. Following the instructions on the PyQt5 download page I first downloaded SIP from this page. I downloaded the zip file for windows. Following these instructions I configured sip for mingw by running

python configure.py --platform win32-g++

The next step then is to run make. However if you start a WinPython Command Prompt you do not have make. I fixed this by copying an old msys installation, from an older (not connected to WinPython) mingw installation, to the mingw folder in the WinPython folder (as noted above). Then by changing the fstab file in msys/1.0/etc to this e:/WinPython-32bit-2.7.10.2/python-2.7.10/share/mingwpy/ /mingw I have a msys system setup for working with the mingw from the WinPython distribution. From a msys shell I can then run make and make install for sip.

Next step is to do the same for PyQt5 download. However, there the configure.py script does not recognize the --platform switch. Use the --spec=win32-g++ switch is also not good enough. The problem is that it somehow still puts "windows" commands in the Makefiles it generates for rename, deleting files folders etc. I could only fix this by changing some code in the configure.py script. In the function run_qmake I added the lines

args.append('-spec')
args.append('win32-g++')

(do this before the "if recursive:" statement). While you are busy editing the configure.py file you can also follow the advice in this forum post to handle any issues with mismatching licenses. Somehow configure.py was detecting a different Qt version. This version was actually located in the site-packages/PyQt4 folder (in WinPython-32bit-2.7.10.2/python-2.7.10). By temporarily renaming this PyQt4 folder you can fix this issue.

After this. If you run

python configure.py --spec=win32-g++

from a msys shell should create the right Makefile (note that this means you have to put WinPython in your system path (environment variables in control panel from advanced system settings in the control panel of windows) because otherwise you have no python in your msys shell. Then you can run make and make install from the msys shell.

Then you are almost done. If at this stage you run a PyQt5 python script it will probably complain that it 'Failed to load platform plugin "windows"'. This was a tricky one to solve. For c++ qt applications it is usually enough to copy the plugins folder to the location of your executable (+ any other needed qt dll's), but what is the location of your executable in this case? I only managed to get it running by adding a new environment variable:

QT_QPA_PLATFORM_PLUGIN_PATH='E:\Qt\5.5\mingw492_32\plugins'

UI not updating in Qt Creator

After not having opened a project for while in QtCreator it often happens that changes made to the user interface in QtCreator are not coming through in the application after recompiling. This is then caused because I am now using a new version of QtCreator or I used to work on the project under Linux instead of Windows (or something like that). The problem is that QtCreator keeps changing where it puts the output of compiling the .ui file. Sometimes it is in the main project folder, sometimes where the .ui file is located and now it was changed into the folder with the impossible name yourProject-build-desktop-Qt_4_8_1_for_Desktop_-_MinGW__Qt_SDK__Release/Release (where it also puts the object files). And because previously it was stored in the project folder it will first find that old version. I guess removing the old version could work but I liked the solution I found here better: in the project file you can specify where the ui compilation output is stored:

UI_DIR = c:\YourLocation

cx_freeze issues with scipy

When using Cx_freeze with a script that uses an interpolation function from scipy I was getting import errors. More specifically the error was "ImportError: No module named _ufuncs_cxx"

This can be solved by explicitly adding two scipy modules:
cxfreeze --include-modules=scipy.special._ufuncs_cxx,scipy.sparse.csgraph._validation your_script.py --target-dir your_target_dir

This solution is based on information from this website.