>>> class C:
    ...     def __len__(self):
    ...             return 10
    ...     def __getitem__(self, i):
    ...             if i >= 10:
    ...                     raise IndexError('out of range')
    ...             return i+1
    ... 
    >>> c = C()
    >>> import bisect
    >>> bisect.bisect_left(c, 1)
    0
    >>> bisect.bisect_left(c, 4)
    3