qt python development - pyside2

hrs1 · wrote on 26 Jul 2018, 20:15

Trying to run Qt in Python using PySide2.
But I am getting the following error:

qt.qpa.plugin: Could not load the Qt platform plugin "windows" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: minimal, offscreen, windows.

My configuration is Windows 10 with Anaconda and python 3.6 (all latest versions).
I have Qt installed and working (c:\qt) but it is not in the path environment variable so it shouldn't be causing problems.
I noticed that qt library files (.dll) are present both in:

C:\Users\user\Anaconda3\Lib\site-packages\PySide2
C:\Users\user\Anaconda3\Library\bin
I am running from within the Anaconda Prompt and the path environment variable starts with:

C:\Users\user\Anaconda3
C:\Users\user\Anaconda3\Library\mingw-w64\bin
C:\Users\user\Anaconda3\Library\usr\bin
C:\Users\user\Anaconda3\Library\bin
C:\Users\user\Anaconda3\Scripts
C:\Users\user\Anaconda3\bin

I've searched various forums with similar problems, all pointing to path problems, but I haven't been able to find a solution

SGaist · wrote on 26 Jul 2018, 21:41

Hi,

Since you are using conda, why are you trying to use your own installation of Qt ?
You should rather use the dependencies that came with conda.

hrs1 · wrote on 26 Jul 2018, 22:14

I am using conda's files.
I just mentioned that the additional qt installation (used for c++ development) does not "clash" as its path is not present in the path environment variable.

from the various posts online it seems that conda and qt don't "get along" too well.
btw, I'm experiencing the same difficulties on another computer (again win-10 and conda)

SGaist · wrote on 27 Jul 2018, 16:56

Just in case, did you check that all your packages are coming from the same conda channel ?

giumas · wrote on 27 Jul 2018, 22:52

Try to first set QT_DEBUG_PLUGINS=1 to get more info on what is failing: https://stackoverflow.com/a/51563781/2741329

hrs1 · wrote on 29 Jul 2018, 00:31

Thanks for the feedback.
After setting the QT_DEBUG_PLUGINS environment flag, I get the following:

QFactoryLoader::QFactoryLoader() checking directory path "C:/Users/user/Anaconda3/Library/plugins/platforms" ...
QFactoryLoader::QFactoryLoader() looking at "C:/Users/user/Anaconda3/Library/plugins/platforms/qminimal.dll"
Found metadata in lib C:/Users/user/Anaconda3/Library/plugins/platforms/qminimal.dll, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "minimal"
        ]
    },
    "className": "QMinimalIntegrationPlugin",
    "debug": false,
    "version": 329218
}


Got keys from plugin meta data ("minimal")
QFactoryLoader::QFactoryLoader() looking at "C:/Users/user/Anaconda3/Library/plugins/platforms/qoffscreen.dll"
Found metadata in lib C:/Users/user/Anaconda3/Library/plugins/platforms/qoffscreen.dll, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "offscreen"
        ]
    },
    "className": "QOffscreenIntegrationPlugin",
    "debug": false,
    "version": 329218
}


Got keys from plugin meta data ("offscreen")
QFactoryLoader::QFactoryLoader() looking at "C:/Users/user/Anaconda3/Library/plugins/platforms/qwindows.dll"
Found metadata in lib C:/Users/user/Anaconda3/Library/plugins/platforms/qwindows.dll, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "windows"
        ]
    },
    "className": "QWindowsIntegrationPlugin",
    "debug": false,
    "version": 329218
}


Got keys from plugin meta data ("windows")
QFactoryLoader::QFactoryLoader() checking directory path "C:/Users/user/Anaconda3/platforms" ...
Cannot load library C:\Users\user\Anaconda3\Library\plugins\platforms\qwindows.dll: The specified procedure could not be found.
QLibraryPrivate::loadPlugin failed on "C:/Users/user/Anaconda3/Library/plugins/platforms/qwindows.dll" : "Cannot load library C:\\Users\\user\\Anaconda3\\Library\\plugins\\platforms\\qwindows.dll: The specified procedure could not be found."
qt.qpa.plugin: Could not load the Qt platform plugin "windows" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: minimal, offscreen, windows.

regarding conda channels, the following is a partial output of conda list (with qt related packages, and a few other packages):

# Name                    Version                   Build  Channel
pillow                    5.1.0            py36h0738816_0
pip                       10.0.1                   py36_0
pkginfo                   1.4.2                    py36_1
pluggy                    0.6.0                    py36_0
ply                       3.11                     py36_0
progress                  1.4                      py36_0
prometheus_client         0.3.0                    py36_0
prompt_toolkit            1.0.15           py36h60b8f86_0
protobuf                  3.5.2            py36h6538335_0
psutil                    5.4.6            py36hfa6e2cd_0
py                        1.5.4                    py36_0
pyasn1                    0.4.3                    py36_0
pyasn1-modules            0.2.2                    py36_0
pycodestyle               2.4.0                    py36_0
pycosat                   0.6.3            py36h413d8a4_0
pycparser                 2.18                     py36_1
pycrypto                  2.6.1            py36hfa6e2cd_9
pycurl                    7.43.0.2         py36h74b6da3_0
pyflakes                  2.0.0                    py36_0
pygments                  2.2.0            py36hb010967_0
pylint                    1.9.2                    py36_0
pyodbc                    4.0.23           py36h6538335_0
pyopenssl                 18.0.0                   py36_0
pyparsing                 2.2.0                    py36_1
pyqt                      5.6.0            py36hb5ed885_5
PySide2                   5.11.0                    <pip>
pysocks                   1.6.8                    py36_0
pytables                  3.4.4            py36he6f6034_0
pytest                    3.6.3                    py36_0
pytest-arraydiff          0.2              py36h39e3cac_0
pytest-astropy            0.4.0                    py36_0
pytest-doctestplus        0.1.3                    py36_0
pytest-openfiles          0.3.0                    py36_0
pytest-remotedata         0.3.0                    py36_0
python                    3.6.6                hea74fb7_0
python-dateutil           2.7.3                    py36_0
pytorch                   0.3.0                py36_0.3.0    peterjc123
pytz                      2018.5                   py36_0
pywin32                   223              py36hfa6e2cd_1
pywinpty                  0.5.4                    py36_0
pyyaml                    3.13             py36hfa6e2cd_0
pyzmq                     17.0.0           py36hfa6e2cd_3
qt                        5.6.2           vc14h6f8c307_12
qtawesome                 0.4.4            py36h5aa48f6_0
qtconsole                 4.3.1            py36h99a29a9_0
qtpy                      1.4.2                    py36_0
vc                        14.1                 h0510ff6_3
vs2015_runtime            15.5.2                        3
vs2017_runtime            15.5.2                        1

hrs1 · 3 May 2019, 19:17

Update:
I uninstalled the pip version of PySide2
and installed the conda-forge version

now things seem to be working (at least a qt window opened...)

thanks

metalshreds · 5 Mar 2019, 19:18

I just ran into this problem and had the exact same output. From my troubleshooting it seems like qwindows.dll in Anaconda Library (C:/Users/user/Anaconda3/Library/plugins/platforms/qwindows.dll) is not the same as the one in the pyside2 folder, therefore it finds a qwindows.dll but it's not the correct one so it can't load it. I had to uninstall and reinstall Anaconda and then install pyside2 within the environment (creating an anaconda env in pycharm and installing pyside2 also through pycharm, but not using conda). Correct location for my qwindow.dll was C:/ProgramData/Anaconda3/envs/my_project/lib/site-packages/PySide2/plugins/platforms/qwindows.dll"

abdufarag · wrote on 9 Jun 2020, 04:17

I have the same issue and fixed in this way
In Anaconda installation folder I went to : (change it to your installed path):

C:\ProgramData\Anaconda3\Lib\site-packages\PySide2

Edit this file by adding the following code lines :

# below the line 23 type.__signature__
    pyside_package_dir =  os.path.abspath(os.path.dirname(__file__))
    dirname = os.path.dirname(__file__)
    plugin_path = os.path.join(dirname, 'plugins', 'platforms')
    os.environ['QT_QPA_PLATFORM_PLUGIN_PATH'] = plugin_path

save this file and try again and the issue should be gone :)