no module named cv2 error in python code example

Example 1: ModuleNotFoundError: No module named 'cv2'

To solve this run the following
# main opencv
pip install opencv-python
# contrib package for the extra features
pip install opencv-contrib-python

The official installation instructions are on the opencv website.
More info can be found here: 
https://www.pyimagesearch.com/opencv-tutorials-resources-guides/

Example 2: cv2 not found

python -m pip install opencv-python

Example 3: ModuleNotFoundError: No module named 'cv2'

sudo apt-get install python-opencv libopencv-dev python-numpy python-dev