Example for producing a contour plot and also plotting the points outside the outer contour

plotoutside.py

import numpy as np
from matplotlib import pyplot as pl

x = np.random.randn(5000)
y = 0.2*np.random.randn(5000) + 3

xbins = 20
ybins = 20
H, xedges, yedges = np.histogram2d(x, y, bins=(xbins, ybins))

# set levels as in IDL djs_contourpts https://searchcode.com/codesearch/view/84370/
nlevels = 3
levels = ((np.arange(nlevels)+1) * np.max(H[:])) / float(nlevels)

C = pl.contour(H.T, extent=[xedges[0], xedges[-1], yedges[0], yedges[-1]], levels=levels)
p = C.collections[0].get_paths()[0]

poutside = ~p.contains_points(np.vstack((x,y)).T)
pl.plot(x[poutside], y[poutside], '.')

This example stems from this facebook post.

Following another comment on that post my example seems to be similar to what is done in the astroML scatter_contour function