title: How can plot Artists be reused (Line2D)?
body: <p>How can the plot lines from <code>.plot</code> be reused in subsequent plots?</p>
  <p>I'd like to make plots on 4 axes, first three individual plot on each axes, and the last all 3 plots on last axes.
  Here is the code:</p>
  <pre><code>from numpy import *
  from matplotlib.pyplot import *
  fig=figure()
  data=arange(0,10,0.01)
  ax1=fig.add_subplot(2,2,1)
  ax2=fig.add_subplot(2,2,2)
  ax3=fig.add_subplot(2,2,3)
  ax4=fig.add_subplot(2,2,4)
  
  line1=ax1.plot(data,data)
  line2=ax2.plot(data, data**2/10, ls='--', color='green')
  line3=ax3.plot(data, np.sin(data), color='red')
  #could I somehow use previous plots, instead recreating them all?
  line4=ax4.plot(data,data)
  line4=ax4.plot(data, data**2/10, ls='--', color='green')
  line4=ax4.plot(data, np.sin(data), color='red')
  show()
  </code></pre>
  <p>The resulting picture is:<br><img src="https://i.stack.imgur.com/3vWwg.png" alt="enter image description here" /><br>
  Is there a way to define plots first and then add them to axes, and then plot them? Here is the logic I had in mind:</p>
  <pre><code>#this is just an example, implementation can be different
  line1=plot(data, data)
  line2=plot(data, data**2/10, ls='--', color='green')
  line3=plot(data, np.sin(data), color='red')
  line4=[line1, line2, line3]
  </code></pre>
  <p>Now plot line1 on ax1, line2 on ax2, line3 on ax3 and line4 on ax4.</p>