import bisect

class ListyBoom(list):
    def boom(*args, **kw):
        assert False
    append = insert = __setitem__ = __setslice__ = boom

l = ListyBoom()
try:
    l.insert(-1, 'data')
    assert False
except AssertionError:
    pass

# oops
bisect.insort(l, 'data')
assert l == ['data']

class DuckList(object):
    def __init__(self):
        self.bucket = []
    def insert(self, index, item):
        self.bucket.insert(index, item)
    def __getitem__(self, index):
        return self.bucket[index]
    def __len__(self):
        return len(self.bucket)

ok = DuckList()
ok.insert(-1, 'data')
assert ok.bucket == ['data']
bisect.insort(ok, 'insorted')
assert ok.bucket == ['data', 'insorted']