>>> """
=========================
Frontpage contour example
=========================

This example reproduces the frontpage contour example.
"""
... 
... import matplotlib.pyplot as plt
... import numpy as np
... from matplotlib import cm
... 
... extent = (-3, 3, -3, 3)
... 
... delta = 0.5
... x = np.arange(-3.0, 4.001, delta)
... y = np.arange(-4.0, 3.001, delta)
... X, Y = np.meshgrid(x, y)
... Z1 = np.exp(-X**2 - Y**2)
... Z2 = np.exp(-(X - 1)**2 - (Y - 1)**2)
... Z = Z1 - Z2
... 
... norm = cm.colors.Normalize(vmax=abs(Z).max(), vmin=-abs(Z).max())
... 
... fig, ax = plt.subplots()
... cset1 = ax.contourf(
...     X, Y, Z, 40,
...     norm=norm)
... ax.set_xlim(-2, 2)
... ax.set_ylim(-2, 2)
... ax.set_xticks([])
... ax.set_yticks([])
... fig.savefig("contour_frontpage.png", dpi=25)  # results in 160x120 px image
... plt.show()
...