text: #!/usr/bin/env python
  # -*- coding: utf-8 -*-
  
  import numpy
  from matplotlib import mlab
  from matplotlib import pyplot
  
  
  def main():
      # Part of the example at 
      # http://matplotlib.sourceforge.net/plot_directive/mpl_examples/pylab_examples/contour_demo.py
      delta = 0.025
      x = numpy.arange(-3.0, 3.0, delta)
      y = numpy.arange(-2.0, 2.0, delta)
      X, Y = numpy.meshgrid(x, y)
      Z1 = mlab.bivariate_normal(X, Y, 1.0, 1.0, 0.0, 0.0)
      Z2 = mlab.bivariate_normal(X, Y, 1.5, 0.5, 1, 1)
      Z = 10.0 * (Z2 - Z1)
      pyplot.figure()
      CS = pyplot.contour(X, Y, Z)
      pyplot.show()
  
  
  if __name__ == "__main__":
      main()
  