chicks.py

import random
from collections import defaultdict


class circle(list):
    '''Circular list, i.e.
    >>> c = circle([1,2,3])
    >>> c[0], c[3], c[7]
    (1, 1, 2)
    '''
    def __getitem__(self, i):
        return list.__getitem__(self, i % len(self))


def invert_mapping(dct):
    inv = defaultdict(list)
    for k, v in dct.items():
        inv[v].append(k)
    return dict(inv)


def choose_targets(items):
    items = circle(items)
    targets = {source: random.choice((items[i-1], items[i+1]))
               for i, source in enumerate(items)}
    return targets


def count_unpecked(peckers):
    chicks = peckers.keys()
    peckees = invert_mapping(peckers).keys()
    return len(chicks - peckees)


def simulate_chicks(nchicks=100):
    chicks = range(nchicks)
    peckers = choose_targets(chicks)
    return count_unpecked(peckers)


def simulate_fn(fn, nsims=1000, *args, **kwargs):
    return sum(fn(*args, **kwargs) for i in range(nsims))/nsims