title: How to extract velocity vectors of pixels from OpenCV calcOpticalFlowFarneback - Python version)
body: <p>I want to extract the optical flow velocity vectors of every pixels between two frames. I am using the OpenCV function as follow:</p>
  
  <pre><code>flow = calcOpticalFlowFarneback(Previous_Gray, Current_Gray, Optical_Flow, 0.5, 3, 15, 3, 5, 1.2, 0);
  
  Previous_Gray = previous frame 
  Current_Gray = current frame 
  </code></pre>
  
  <p>I would like to know what is the format of  <code>flow</code> and how to extract it.</p>
  
  <p>Thanks ahead for any help! :-)</p>
  
  <p>P.S. I know my question is almost identical to this one: <a href="https://stackoverflow.com/questions/16672003/how-to-extract-velocity-vectors-of-a-pixels-from-calcopticalflowfarneback">How to extract velocity vectors of a pixels from calcOpticalFlowFarneback</a> . However, I am coding in Python, and would like a solution in Python, please.</p>