def display_col_dp(dp_list, attr_name):
    """
    show a value assocciated with an attribute for each
    DataProperty instance in the dp_list
    """

    print()
    print("---------- {:s} ----------".format(attr_name))
    print([getattr(dp, attr_name) for dp in dp_list])
show a value assocciated with an attribute for each
    DataProperty instance in the dp_list