def normalize(iterable):
    """
    Normalize an iterable of numbers in a series that sums up to 1.

    Arguments:
        iterable(numbers): an iterable containing numbers
            (either `int` or `float`) to normalize.

    Returns:
        list: Normalized float values, in the same order as the one provided.

    Example:
        >> > normalize([3, 2, 1])
        [0.5, 0.333333, 0.166667]

    """
    tot = sum(iterable)
    return [float(v) / tot for v in iterable]