In [18]: %timeit nested_contains(3, where)
1000000 loops, best of 3: 909 ns per loop

In [19]: %timeit nested_contains(4, where)
100000 loops, best of 3: 9.62 µs per loop

In [20]: %timeit nested_contains(9, where)
100000 loops, best of 3: 11.8 µs per loop