def unique_tuples(df, columns):
    """
    Return the set of unique tuples from a dataframe for the specified
    columns.
    Parameters
    ----------
    df : pandas.DataFrame
        Dataframe with the columns of data to be considered.
    columns : list-like
        A list of column names in the dataframe from which to
        construct the tuples.
    """
    return set(zip(*[df[_] for _ in columns]))