title: How to update OpenCV 3.4.2 to OpenCV 4 or latest stable version?
body: <p>I have installed OpenCV 3.4.2 successfully by following the tutorial given here:</p>
  
  <p><a href="https://www.pyimagesearch.com/2015/07/20/install-opencv-3-0-and-python-3-4-on-ubuntu/" rel="nofollow noreferrer">https://www.pyimagesearch.com/2015/07/20/install-opencv-3-0-and-python-3-4-on-ubuntu/</a></p>
  
  <p>Now, I would like to update to openCV 4 or the latest stable version. </p>
  
  <p>Do I need to uninstall 3.4.2 first? 
  If so, how should I uninstall it. </p>
  
  <p>I am afraid to creating another virtual environment and installing version 4 or master package from github by following the same steps might create conflicts. Please advice.</p>
  
  <p>Working on Ubuntu 16.04 LTS, python 3.5</p>