Return the median of the list of numbers.
    see: http://mail.python.org/pipermail/python-list/2004-December/294990.html

def median(numbers):
    """
    Return the median of the list of numbers.
    see: http://mail.python.org/pipermail/python-list/2004-December/294990.html
    """

    # Sort the list and take the middle element.
    n = len(numbers)
    copy = sorted(numbers)
    if n & 1:  # There is an odd number of elements
        return copy[n // 2]
    else:
        return (copy[n // 2 - 1] + copy[n // 2]) / 2.0