In [1]: import os
   ...: import sys
   ...: import numpy as np
   ...: import matplotlib.pyplot as plt

In [2]: plt.plot(np.sin(np.linspace(0.,np.pi,100)))
   ...: plt.show()
<ipython-input-2-4bf852e4e6b7>:2: UserWarning: FigureCanvasAgg is non-interactive, and thus cannot be shown
  plt.show()