Python opencv drawContours does not show anything

Question

I followed the tutorial at this page but nothing seems to happen when the line cv2.drawContours(im,contours,-1,(0,255,0),3) is executed. I was expecting to see

Answer 1

You have to do something to the effect of:

cv2.drawContours(im,contours,-1,(255,255,0),3)
cv2.imshow("Keypoints", im)
cv2.waitKey(0)