I agree, you could learn so much just looking at how he defines functions.. see this for example:

    def pdist(counter):
        "Make a probability distribution, given evidence from a Counter."
        N = sum(counter.values())
        return lambda x: counter[x]/N

    P = pdist(COUNTS)

from http://nbviewer.jupyter.org/url/norvig.com/ipython/How%20to%...