I was able to use openCV for 32-bit python however I had to switch to 64-bit to use tensorflow.
I did follow the instructions of from the opencv page here.
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I thought had the same problem after I upgraded to python 3.6.2 64bit architecture. But it turned out that I was installing by..
pip install cv2
... on python 3.6.2 x64 instead of..
pip install opencv-python