Found here: https://goo.gl/aYwEaV
The proper way to install OpenCV is by building the source: https://opencv.org/releases.html
For today, you can just install it via a pip package. Only do this if you don't already have OpenCV, multiple installations will conflict.
Important, use pip3 if you use multiple Python versions
pip3 install opencv-contrib-python
Troubleshooting: https://pypi.org/project/opencv-contrib-python/
Anaconda: https://conda.io/docs/user-guide/install/index.html OpenCV through Anaconda here: https://www.geeksforgeeks.org/set-opencv-anaconda-environm…/
On Mac, via Homebrew: https://www.pyimagesearch.com/…/install-opencv-3-on-macos-…/
On Linux, build from source: https://docs.opencv.org/…/d7/d9f/tutorial_linux_install.html