Qt platform plugin "windows"

[mottosso]

Cannot instantiate a QApplication.

import sys
from PyQt5 import QtWidgets

app = QtWidgets.QApplication(sys.argv)

Results in:

This application failed to start because it could not find or load the Qt platfo
rm plugin "windows".

Available platform plugins are: minimal (from C:\Python27\lib\site-packages\PyQt
5\plugins\platforms), offscreen (from C:\Python27\lib\site-packages\PyQt5\plugin
s\platforms), windows (from C:\Python27\lib\site-packages\PyQt5\plugins\platform
s).

Reinstalling the application may fix this problem.

Having encountered the problem in the past, I could solve it by appending the plugins by hand like this:

import os
import sys

import PyQt5

dirname = os.path.dirname(PyQt5.__file__)
plugin_path = os.path.join(dirname, 'plugins', 'platforms')
os.environ['QT_QPA_PLATFORM_PLUGIN_PATH'] = plugin_path

from PyQt5 import QtWidgets
app = QtWidgets.QApplication(sys.argv)

However this produces the same error. The odd thing is that it says it can't load the plugin, and then lists the plugin as one of the available ones. Maybe a permission issue? Yet permissions on the files are unlocked and even replacing it with the source original from the Qt installation yields the same results. Removing the plugin from the directory correctly removes it from plugins found.

depends.exe

Running depends on qwindows.dll yields a few interesting results.

However each of these are available directly within the PyQt5 Python package directory.

It works

If keeping the original installation of Qt on the PATH, PyQt5 seems to work. From a terminal:

# Keeping C:\Qt\Qt5.3.0\5.3\msvc2013_64\bin on the PATH

import os
import sys

from PyQt5 import QtWidgets
app = QtWidgets.QApplication(sys.argv)
button = QtWidgets.QPushButton("Hello World")
button.show()

So there must be something within this directory which is requited by PyQt5. But copying the entire contents into the PyQt5 Python library directory yields no better results.

[The-Compiler]

I've had the same issue with cx_Freeze - there for me it helped to copy libEGL.dll to the frozen package.

Maybe that helps in some way?

[mottosso]

Thanks @The-Compiler, I'll have a look at that tonight. You're thinking of just putting it in the root PyQt5 Python library directory?

[The-Compiler]

I'm afraid I have no idea what to do with it (and I don't know anything about putting C projects on PyPI at all), but that's where I remember the message from (with windows being listed in the available platforms as well).

[mottosso]

I'm afraid I have no idea what to do with it

No problem, it does help to narrow down the dependencies and this seems to be one of them.

(and I don't know anything about putting C projects on PyPI at all

Though I'm sure there are practices for doing this more gracefully, the way I'll handle it initially is the same as with any Python package with package data; to simply include all non-Python files in the package_data argument of setup().

• https://github.com/pyqt/pyqt5/blob/master/setup.py

[mottosso]

Seems to work now.

Here are the changes:

• Compiled using Qt 5.3.1 rather than 5.3.2 as it isn't yet supported
• Binaries was coming from the Python 3 binaries supplied via Riverbank's website but are now coming directly from the Qt distribution.
• __init__.py now initialises PATH and QT_QPA_PLATFORM_PLUGIN_PATH

Platform plug-ins

The Riverbank distribution ships with a qt.conf which initialises the PATH and platform plugin path, this release instead initialises these via the __init__.py so as to not need to provide the qt.conf file.

Pre-requisities

To run this VS2013 compiled release of PyQt5, you'll need the VS2013 redistributables.

[mottosso]

This problem re-surfaces in certain situations that I am unable to re-produce.

The above was reported by @davidmartinezanim on a Windows 7 machine, running Python 2.7.9 x64 with Visual C++ 2013 re-distributable installed.

[emmatyping]

I am having the same error with Python 2.7.9 x64 on Windows 8. I just freshly installed. Looking through the qt forums this is a problem for qt apps too. I have read that the app needs to have qt.conf and the platforms folder in its path. I'll check this later today or tomorrow.

[emmatyping]

Well, I have a similar but slightly different problem. The windows platform option (or any option for that matter) doesn't show up at all. Interestingly, your above method of adding the os.environ value worked. The weird part is that setx QT_QPA_PLATFORM_PLUGIN_PATH "C:\Python27\lib\site-packages\PyQt 5\plugins\platforms" didn't work at all. I couldn't call the variable from cmd like PATH, and it didn't work with a Python script. Very weird.

[mottosso]

If you are installing from GitHub, and not PyPI, then you should have 5.4. If you do, have a go with this to see if it changes anything.

https://github.com/pyqt/python-qt5/wiki/Installation#install

It will create a qt.conf for you with the appropriate settings for your system.

To check the version of PyQt, try this.

>>> import PyQt5
>>> PyQt5.pyqt_version
'5.3.2'

[emmatyping]

I installed from Github. I actually followed the steps you are pointing to, and I still got the error. Interesting. I just ran it again from the downloaded directory, and that might have fixed it. So maybe an extra step of running it again? Or just running it after install?

Well, I just re-installed from Github, and it worked if I ran the qt.conf generator after running python setup.py install. Very strange.