title: lambda *args, **kwargs: None
body: <p>consider:</p>
  
  <pre><code>blank_fn = lambda *args, **kwargs: None
  
  def callback(x, y, z=''):
      print x, y, z
  
  def perform_task(callback=blank_fn):
      print 'doing stuff'
      callback('x', 'y', z='z' )
  </code></pre>
  
  <p>The motivation for doing it this way is I don't have to put in logic to check if callback has been assigned because it defaults to blank_fn which just does nothing.</p>
  
  <p>This works, but is there some reason I shouldn't do it? Is it pythonic? Is there a better way to do it? Is there a built-in for:</p>
  
  <pre><code>lambda *args, **kwargs: None
  </code></pre>