plt.show()
    fig.savefig('./result.png',bbox_inches='tight')  # save the figure to file
    plt.close(fig)  # close the figure

fig.savefig('./result.png',bbox_inches='tight')  # save the figure to file
  File "/usr/local/lib/python2.7/dist-packages/matplotlib/figure.py", line 1834, in savefig
    self.canvas.print_figure(fname, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/matplotlib/backend_bases.py", line 2188, in print_figure
    self.figure.dpi = dpi
  File "/usr/local/lib/python2.7/dist-packages/matplotlib/figure.py", line 436, in _set_dpi
    self.set_size_inches(w, h, forward=forward)
  File "/usr/local/lib/python2.7/dist-packages/matplotlib/figure.py", line 745, in set_size_inches
    manager.resize(int(canvasw), int(canvash))
  File "/usr/local/lib/python2.7/dist-packages/matplotlib/backends/backend_tkagg.py", line 540, in resize
    self.canvas._tkcanvas.master.geometry("%dx%d" % (width, height))
  File "/usr/lib/python2.7/lib-tk/Tkinter.py", line 1667, in wm_geometry
    return self.tk.call('wm', 'geometry', self._w, newGeometry)
_tkinter.TclError: can't invoke "wm" command: application has been destroyed