def most_common_used_element(L):
    """From a giver sequence L, return the most common used element with
    it percentage of use. If there is more than one most commin used element,
    only one of them will be returned.

    :param L: a list of elements

    :type L: list(int)

    :return: a couple, the most common used element in the list and its 
    percentage of use.
    :rtype: tuple(int, float)
    """
    v = max(set(L), key=L.count)
    return v, L.count(v) / float(len(L))