Optical Flow Farneback - doubt in tutorial

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So i was trying to understand the python code for optical flow using Farneback method. But I had a doubt about expressions like this-

1.hsv[...,1] = 255

2.hsv[...,0] = ang*180/np.pi/2

I do not understand what the 3 dots in the square brackets represent. This is the first time I'm seeing such notation in python.

I need to understand this so that I can write the equivalent program in C++ as I can't find any decent tutorial or documentation on Farnebeck method in C++.

Link to tutorial(2nd program)- http://opencv-python-tutroals.readthe...