This program produces a filled contour plot of a function, labels the contours and provides some custom styling for their colours.
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.cm as cm
X = np.linspace(0,1,100)
Y = X.copy()
X, Y = np.meshgrid(X, Y)
alpha = np.radians(25)
cX, cY = 0.5, 0.5
sigX, sigY = 0.2, 0.3
rX = np.cos(alpha) * (X-cX) - np.sin(alpha) * (Y-cY) + cX
rY = np.sin(alpha) * (X-cX) + np.cos(alpha) * (Y-cY) + cY
Z = (rX-cX)*np.exp(-((rX-cX)/sigX)**2) * np.exp(- ((rY-cY)/sigY)**2)
fig = plt.figure()
ax = fig.add_subplot(111)
# Reversed Greys colourmap for filled contours
cpf = ax.contourf(X,Y,Z, 20, cmap=cm.Greys_r)
# Set the colours of the contours and labels so they're white where the
# contour fill is dark (Z < 0) and black where it's light (Z >= 0)
colours = ['w' if level<0 else 'k' for level in cpf.levels]
cp = ax.contour(X, Y, Z, 20, colors=colours)
ax.clabel(cp, fontsize=12, colors=colours)
plt.show()
