Python: sampling for top referrers to a type

sampler.py

def teardown(self):
    # other stuff...
    gc.collect()
    parents = {}
    for o in gc.get_objects():
        if not isinstance(o, list):
            continue

        c = c + 1
        if c % 1000 == 0:
            print("c", c)

        p = random.randint(1, 10)
        if p != 1:
            continue

        for p in gc.get_referrers(o):
            t = str(type(p))
            parents[t] = parents.get(t, 0) + 1

    import operator
    off = sorted(parents.items(), key=operator.itemgetter(1), reverse=True)