5

I am setting up a python3 virtual environment for my development, so I am staying away from the package manager apt-install

$ python3 -m venv . # create my environment in my working directory

I then activated the venv and installed pyqt5

$ source bin/activate
$ pip install PyQt5

I am notified of a successful installation and PyQt5 and PyQt5-Sip shows up in my pip list

When I build a sample application I receive the error:

qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "/path/to/venv/lib/python3.8/site-packages/PyQt5/Qt/plugins" 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: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl, xcb.


Aborted (core dumped)

I exported the environment variable for debugging

export QT_DEBUG_PLUGINS=1

I try running my application again and here is the specific error I get in the linker

QFactoryLoader::QFactoryLoader() looking at "/path/to/venv/lib/python3.8/site-packages/PyQt5/Qt/plugins/platforms/libqxcb.so"
Found metadata in lib /path/to/venv/lib/python3.8/site-packages/PyQt5/Qt/plugins/platforms/libqxcb.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "xcb"
        ]
    },
    "archreq": 0,
    "className": "QXcbIntegrationPlugin",
    "debug": false,
    "version": 331520
}

Got keys from plugin meta data ("xcb")
QFactoryLoader::QFactoryLoader() checking directory path "/usr/bin/platforms" ...
Cannot load library /path/to/venv/lib/python3.8/site-packages/PyQt5/Qt/plugins/platforms/libqxcb.so: (libxcb-xinerama.so.0: cannot open shared object file: No such file or directory)

The important error here is

libxcb-xinerama.so.0: cannot open shared object file: No such file or directory

So I dig deeper. I decide to use the ldd command to parse the shared library dependencies.

$ ldd /path/to/venv/lib/python3.8/site-packages/PyQt5/Qt/plugins/platforms/libqxcb.so

and lo-and behold:

libxcb-xinerama.so.0 => not found
libxcb-xinerama.so.0 => not found

These shared libraries are missing from the libqxcb shared library dependencies list. I would hope pip's installation would have this included but it is not. I have not found a solution to this problem anywhere, and the small amount of sources I have found mentioned using apt-install to solve these issues. I don't want to change my system, I prefer keeping things sandboxed.

What can I do to fix this dependency?

Asicc
  • 51

3 Answers3

4

The exact same issue occurred when I installed pyqt5 and matplotlib on Ubuntu 20.04, using pipenv (which also creates a venv).

On my system this was easily solved by installing the missing libxcb-xinerama0, using apt:

sudo apt install libxcb-xinerama0
djvg
  • 386
1

I'm on Ubuntu 18.04.3 and encountered the same issue. Here is what I resolved this problem.

Uninstall PyQt by using pip3

pip3 uninstall pyqt5

And install it via apt-get

sudo apt-get install python3-pyqt5
Nga Nga
  • 11
0

I didn't find them with pip either. I think you're stuck either compiling this from source (https://xorg.freedesktop.org/archive/individual/lib/libxcb-1.14.tar.xz) and linking to it, or installing libxcb-xinerama0.

ajgringo619
  • 1,243