Convert a list of ranges to a set of numbers::

    >>> ranges = [(1,3), (5,6)]
    >>> sorted(list(ranges_to_set(ranges)))
    [1, 2, 3, 5, 6]

def ranges_to_set(lst):
    """
    Convert a list of ranges to a set of numbers::

    >>> ranges = [(1,3), (5,6)]
    >>> sorted(list(ranges_to_set(ranges)))
    [1, 2, 3, 5, 6]

    """
    return set(itertools.chain(*(range(x[0], x[1]+1) for x in lst)))