argmax function: return the entry from list X where the argument arg is at a maximum.

argmax.py

def argmax(arg, X):
    """
    >>> zee = [{"cool":{"stuff":1,"things":0.5}},{"cool":{"stuff":2,"things":0.25}}]
    >>> argmax("cool.stuff",zee)
    {'cool': {'things': 0.25, 'stuff': 2}}
    >>> argmax("cool.things",zee)
    {'cool': {'things': 0.5, 'stuff': 1}}
    """
    ranked = sorted(X, key=lambda x: -getByDot(x,arg))
    leader = filter(lambda x: getByDot(x,arg) == reduce(max,[getByDot(r, arg) for r in ranked]),ranked)[0]
    return(leader)