Fibonnaci Series List

fib.py

class FibSeries(list):
    def __init__(self):
        bare_self = super(FibSeries, self)
        bare_self.__setslice__(0, bare_self.__len__(), (1, 1,))

    def __getitem__(self, i):
        bare_self = super(FibSeries, self)
        bare_len = bare_self.__len__()
        if not i < bare_len:
            self._fill_fib(bare_len, i)
        return bare_self.__getitem__(i)

    def _fill_fib(self, start, end):
        bare_self = super(FibSeries, self)
        bare_get = bare_self.__getitem__
        bare_append = bare_self.append
        assert start > 1
        a, b = None, bare_get(start - 2)
        for i in range(start, end + 1):
            a, b = b, bare_get(i - 1)
            bare_append(a + b)

    def __repr__(self):
        return '<FibSeries(0..{})>'.format(super(FibSeries, self).__len__() - 1)

    def __setitem__(*args, **kwargs): raise RuntimeError('FibSeries are immutable')
    def __setslice__(*args, **kwargs): raise RuntimeError('FibSeries are immutable')
    def __delitem__(*args, **kwargs): raise RuntimeError('FibSeries are immutable')
    def __delslice__(*args, **kwargs): raise RuntimeError('FibSeries are immutable')
    def __len__(*args, **kwargs): raise RuntimeError('FibSeries are (effectively) infinite')
    def insert(*args, **kwargs): raise RuntimeError('FibSeries are immutable')
    def append(*args, **kwargs): raise RuntimeError('FibSeries are immutable')
    def pop(*args, **kwargs): raise RuntimeError('FibSeries are immutable')
    def remove(*args, **kwargs): raise RuntimeError('FibSeries are immutable')
    def reverse(*args, **kwargs): raise RuntimeError('FibSeries are immutable')
    def sort(*args, **kwargs): raise RuntimeError('FibSeries are immutable')

if __name__ == '__main__':
    f = FibSeries()
    assert f[0] == 1
    assert f[1] == 1
    assert f[2] == 2
    assert f[3] == 3
    assert f[4] == 5
    assert f[5] == 8
    assert f[6] == 13
    assert f[7] == 21
    assert f[268] == 73822750993122698578207436143903804565580923764844306069