from random import random

def choose_random_predicate(things, pred):
    best_score = -1.0
    best_thing = None
    for thing in things:
        score = random()
        if pred(thing) and (score > best_score):
            best_thing = thing
            best_score = score
    return best_thing

is_even = lambda x : x % 2 == 0;

things = list(range(100))

print( choose_random_predicate(things, is_even) )