import numpy as n
import matplotlib.pyplot as pl

# create data
x = n.random.normal(size=50000)
y = x * 3 + n.random.normal(size=50000)
# construct histogram 2D: data, nbins, color_map
pl.hist2d(x, y, bins=(100, 100), cmap=pl.cm.jet)
# show z-scale
pl.colorbar()
pl.show()