_,cont,hei = cv2.findContours(d_img,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE) ValueError: not enough values to unpack (expected 3, got 2)
#The problem is in this line:
_, contours, hierarchy = cv2.findContours(thresh, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE) # fails with error "not enough values to unpack (expected 3, got 2)"
#Change it to:
contours, hierarchy = cv2.findContours(thresh, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)
#Restart the kernel and run. Your problem should be fixed