Frequently Asked Questions

1. Why are plots not showing up? (Qt core dumped error)

If you get an error similar to this:

QObject::moveToThread: Current thread (0x5632706342d0) is not the object's thread (0x5632
706194c0).
Cannot move to target thread (0x5632706342d0)

qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "/home/USERNAME/.local/lib/p
ython/site-packages/cv2/qt/plugins" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Rein
stalling the application may fix this problem.

Available platform plugins are: xcb, eglfs, linuxfb, minimal, minimalegl, offscreen, vnc,
 wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl.

[1]    1498499 IOT instruction (core dumped)  python example.py

it’s proably because you have PyQt5 and opencv-python packages installed in the same python enviroment. This is due to a known incompatibility between PyQt5 and opencv-python in Linux systems.

Solutions

Removing PyQt5

If you don’t need PyQt5 in the current enviroment (globally by default) you can remove it by simply running:

$ pip uninstall PyQt5

Runing yupi in a separated virtual enviroment

If you don’t want to remove PyQt5 globally, you can create a separated enviroment with yupi. This can be achieved in an easy way by using the venv tool provided by python. You can visit here the section dedicated to this tool in the Python Docs which contains a guide for the enviroment creation and activation.

Once the enviroment is created and activated you can install yupi (and all the dependencies you might need) using the pip command.

$ pip install yupi

Note

The last solutions assume that PyQt5 is not required for your project. If PyQt5 is one of your project dependencies the next solution shows a way to use it along with yupi.

Install opencv from a linux repository

If PyQt5 is also needed along with yupi a known solution is to install opencv from a linux repository. First you need to remove the current opencv instalation with pip:

$ pip uninstall opencv-python

Then install opencv from a linux repository using your current package manager. For example, if you are using apt (for Debian/Ubuntu based systems) you can install it by running:

$ sudo apt install python3-opencv

Note

The name of the package may vary. For example, in Arch repositories it is called python-opencv.