title: Is it possible to set higher z-index of the axis labels?
body: <p>In the following code labels of the axis get hidden behind the graph lines:</p>
  
  <pre><code>import numpy as np
  import matplotlib.pyplot as plt
  
  X = np.linspace(-np.pi, np.pi, 256, endpoint=True)
  C,S = np.cos(X), np.sin(X)
  
  plt.plot(X,C)
  plt.plot(X,S)
  
  plt.xticks([-np.pi, -np.pi/2, 0, np.pi/2, np.pi],
             [r'$-\pi$', r'$-\pi/2$', r'$0$', r'$+\pi/2$', r'$+\pi$'])
  
  plt.yticks([-1, 0, +1],
             [r'$-1$', r'$0$', r'$+1$'])
  
  ax = plt.gca()
  ax.spines['right'].set_color('none')
  ax.spines['top'].set_color('none')
  ax.xaxis.set_ticks_position('bottom')
  ax.spines['bottom'].set_position(('data',0))
  ax.yaxis.set_ticks_position('left')
  ax.spines['left'].set_position(('data',0))
  
  for label in ax.get_xticklabels() + ax.get_yticklabels():
      label.set_fontsize(14)
      label.set_bbox(dict(facecolor='white', edgecolor='None', alpha=0.75 ))
  
  plt.show()
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/Pq032.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Pq032.png" alt="cos/sin"></a></p>
  
  <p>You can see that for instance <code>-pi</code> is hard to see. Is there a way to put axis labels up front?</p>