fz.py

def f(z):
    '''
    >>> f(0)
    -1j

    >>> type(_)
    <type 'complex'>
    '''
    return z**2 - 1j


def f_range(z=0, r=0):
    '''
    >>> f_range()
    {}

    >>> f_range(0, 10)
    {0: -1j, 1: (-1-1j), 2: 1j, 3: (-1-1j), 4: 1j, 5: (-1-1j), 6: 1j, 7: (-1-1j), 8: 1j, 9: (-1-1j)}

    >>> f_range(7, 2)
    {0: (49-1j), 1: (2400-99j)}

    >>> f7 = f_range(7, 8)

    >>> f7[5]
    (9.705883633403057e+53-7.526991236086837e+53j)

    >>> f_range(7, 9)
    Traceback (most recent call last):
        ...
    OverflowError: complex exponentiation
    '''
    results = dict()
    for i in range(r):
        ret = f(z)
        results[i] = ret
        z = ret
    return results


if __name__ == '__main__':
    import doctest
    doctest.testmod()