title: Add plot to a given figure in matplotlib
body: <p>I have created a figure in one part of the code as follows:</p>
  
  <pre><code>n = arange(51)
  fig3 = plt.figure()
  plt.semilogy(n,a1mag,'ro')
  </code></pre>
  
  <p>Now, i want to add another plot to this figure at a later part of the code. Is there some way to access fig3 while plotting?</p>