title: AttributeError: module 'cv2.cv2' has no attribute 'SIFT'
body: <p>I work in Windows 10 and use python 3.6 and install with pip a opencv-python</p>
  
  <p>after then install opencv_python‑3.3.1+contrib‑cp36‑cp36m‑win_amd64.whl
  Opencv test cod is:</p>
  
  <pre><code>from time import time
  from numpy import uint8
  from numpy.random import rand
  import cv2
  
  xy=(512,512)
  Nf = 500
  
  def fpsopencv(dat):
      tic = time()
      for i in dat:
          cv2.imshow('test',i)
          cv2.waitKey(1) #integer milliseconds, 0 makes wait forever
      cv2.destroyAllWindows()
      return Nf / (time()-tic)
  
  
  imgs = (rand(Nf,xy[0],xy[1])*255).astype(uint8)
  fps = fpsopencv(imgs)
  
  print(fps,'fps')
  </code></pre>
  
  <p>It's work well.</p>
  
  <p>But if a want to use a SIFT in my code:</p>
  
  <pre><code>sift = cv2.SIFT()
  </code></pre>
  
  <p>I always get this error:</p>
  
  <pre><code>AttributeError: module 'cv2.cv2' has no attribute 'SIFT'
  </code></pre>
  
  <p>I don't know what is a solution. Somebody can help me? (Sorry for my bad english)</p>