content: #!/usr/bin/env python
  
  """Matplotlib 3D plotting example
  
  Demonstrates plotting with matplotlib.
  """
  
  import sys
  
  from sample import sample
  
  from sympy import sin, Symbol
  from sympy.external import import_module
  
  
  def mplot3d(f, var1, var2, show=True):
      """
      Plot a 3d function using matplotlib/Tk.
      """
  
      import warnings
      warnings.filterwarnings("ignore", "Could not match \S")
  
      p = import_module('pylab')
      # Try newer version first
      p3 = import_module('mpl_toolkits.mplot3d',
          __import__kwargs={'fromlist': ['something']}) or import_module('matplotlib.axes3d')
      if not p or not p3:
          sys.exit("Matplotlib is required to use mplot3d.")
  
      x, y, z = sample(f, var1, var2)
  
      fig = p.figure()
      ax = p3.Axes3D(fig)
  
      # ax.plot_surface(x,y,z) #seems to be a bug in matplotlib
      ax.plot_wireframe(x, y, z)
  
      ax.set_xlabel('X')
      ax.set_ylabel('Y')
      ax.set_zlabel('Z')
  
      if show:
          p.show()
  
  
  def main():
      x = Symbol('x')
      y = Symbol('y')
  
      mplot3d(x**2 - y**2, (x, -10.0, 10.0, 20), (y, -10.0, 10.0, 20))
      # mplot3d(x**2+y**2, (x, -10.0, 10.0, 20), (y, -10.0, 10.0, 20))
      # mplot3d(sin(x)+sin(y), (x, -3.14, 3.14, 10), (y, -3.14, 3.14, 10))
  
  if __name__ == "__main__":
      main()
  