title: Hold is not working for pyplot
body: <p>I have a problem using pyplot. I am new to Python so sorry if I am doing some obvious mistake.</p>
  
  <p>After I have plotted something using pyplot it shows the graph, but when I then try and add e.g. ylabel it will not update the current graph. It results in a new graph with only the ylabel, not previously entered information. So to me it seems to be a problem with recognizing the current graph/axis, but the ishold delivers a True statement.</p>
  
  <p>My setup is Python 2.7 in Python(x,y). The problem occurs both in the Spyder IDE and the IPython Qt Console. It does however not occur in the regular IPython console (which, by constrast, is not interactive, but everything is included when using show(). When I turn off interactive in Spyder/Qt console it does not show anything after using the show() command).</p>
  
  <pre><code>import matplotlib.pyplot as plt
  
  plt.plot([1,2,3,4])
  Out[2]: [&lt;matplotlib.lines.Line2D at 0x78ca370&gt;]
  ￼
  
  plt.ylabel('test')
  Out[3]: &lt;matplotlib.text.Text at 0x5bd5990&gt;
  ￼
  
  plt.ishold()
  Out[4]: True
  
  
  matplotlib.get_backend()
  Out[6]: 'module://IPython.kernel.zmq.pylab.backend_inline'
  </code></pre>
  
  <p>Hope any of you have some input. Thanks.</p>