title: variable increment in python beginner error
body: <p>I am trying to increment the counter each time it detects an object.</p>
  
  <pre><code>count=0
  
  def detect_and_draw(img, cascade):
      # allocate temporary images
      gray = cv.CreateImage((img.width,img.height), 8, 1)
      small_img = cv.CreateImage((cv.Round(img.width / image_scale),
                     cv.Round (img.height / image_scale)), 8, 1)
  
      # convert color input image to grayscale
  cv.CvtColor(img, gray, cv.CV_BGR2GRAY)
  
  # scale input image for faster processing
  cv.Resize(gray, small_img, cv.CV_INTER_LINEAR)
  cv.EqualizeHist(small_img, small_img)
  
  if(cascade):
      t = cv.GetTickCount()
      faces = cv.HaarDetectObjects(small_img, cascade, cv.CreateMemStorage(0),
                                   haar_scale, min_neighbors, haar_flags, min_size)
      t = cv.GetTickCount() - t
      print "time taken for detection = %gms" % (t/(cv.GetTickFrequency()*1000.))
      if faces:
  
          for ((x, y, w, h), n) in faces:
              # the input to cv.HaarDetectObjects was resized, so scale the
              # bounding box of each face and convert it to two CvPoints
              pt1 = (int(x * image_scale), int(y * image_scale))
              pt2 = (int((x + w) * image_scale), int((y + h) * image_scale))
              cv.Rectangle(img, pt1, pt2, cv.RGB(255, 0, 0), 3, 8, 0) 
              count += 1
              print count
  </code></pre>
  
  <p>But I can't get why it has this error .I tried to do the increment just after if but still same error. It's the first time to use python so I can't get the scoping rules. what should I modify?</p>
  
  <pre><code> File "detect.py", line 42, in detect_and_draw
      count +=1
  UnboundLocalError: local variable 'count' referenced before assignment
  </code></pre>