decorator and API

[Lee Harr]

I have a class with certain methods from which I want to select
one at random, with weighting.

The way I have done it is this ....



import random

def weight(value):
    def set_weight(method):
        method.weight = value
        return method
    return set_weight

class A(object):
    def actions(self):
        'return a list of possible actions'

        return [getattr(self, method)
                    for method in dir(self)
                    if method.startswith('action_')]

    def action(self):
        'Select a possible action using weighted choice'

        actions = self.actions()
        weights = [method.weight for method in actions]
        total = sum(weights)

        choice = random.randrange(total)

        while choice> weights[0]:
            choice -= weights[0]
            weights.pop(0)
            actions.pop(0)

        return actions[0]


    @weight(10)
    def action_1(self):
        print "A.action_1"

    @weight(20)
    def action_2(self):
        print "A.action_2"


a = A()
a.action()()




The problem I have now is that if I subclass A and want to
change the weighting of one of the methods, I am not sure
how to do that.

One idea I had was to override the method using the new
weight in the decorator, and then call the original method:

class B(A):
    @weight(50)
    def action_1(self):
        A.action_1(self)


That works, but it feels messy.


Another idea was to store the weightings as a dictionary
on each instance, but I could not see how to update that
from a decorator.

I like the idea of having the weights in a dictionary, so I
am looking for a better API, or a way to re-weight the
methods using a decorator.

Any suggestions appreciated.

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