title: How to check the values in a instance with Python?
body: <p>I have a python class/object as follows.</p>
  
  <pre><code>class Hello:
      def __init__(self):
          self.x = None
          self.y = None
          self.z = None
  
  
  h = Hello()
  h.x = 10
  h.y = 20
  # h.z is not set
  </code></pre>
  
  <p>I need to check if all the member variables are set (not None). How can I do that automatically? </p>
  
  <pre><code>for value in ??memeber variables in h??:
      if value == None:
          print 'value is not set'
  </code></pre>