title: Default parameter value in this __init__() method's definition?
body: <p>I am looking at some python code to control a camera and having some trouble understanding it due to being new at python.  I see that the <code>src</code> parameter is set to <code>0</code>.  Does this mean that if a <code>src</code> is not given <code>0</code> will be used otherwise the given <code>src</code> will be used?</p>
  
  <pre><code>class WebcamVideoStream:
  
      def __init__(self, src=0):
          # initialize the video camera stream and read the first frame
          # from the stream
          self.stream = cv2.VideoCapture(src)
  </code></pre>
  
  <p>so if I do something like this </p>
  
  <pre><code>vs = WebcamVideoStream(3)
  </code></pre>
  
  <p>then the <code>src</code> will be <code>3</code>?
  and if I do this </p>
  
  <pre><code>vs = WebcamVideoStream()
  </code></pre>
  
  <p>then <code>src</code> will be <code>0</code>?</p>