sort_by_second_row

def save(seq, fname):
    with open(fname, 'w') as fd:
        data = sorted(seq, key=operator.itemgetter(1))
        data = itertools.groupby(data, operator.itemgetter(1))
        data = [(e, l) for (l, g) in data for e, l in sorted(g, key=operator.itemgetter(0))]
        fd.writelines('{};{};\n'.format(email, land) for email, land in data)
        return data


def get_double(data):
    seen = set()
    for email, land in data:
        if email in seen:
            yield (email, land)
        seen.add(email)