def build_match_lengths(self):
        match_lengths = self._null_results_matrix

        for rep in range(self.nrepetitions):

            for player_pair_index, interactions in self.interactions[rep].items():
                player, opponent = player_pair_index
                match_lengths[rep][player][opponent] = len(interactions)

                if player != opponent:  # Match lengths are symmetric
                    match_lengths[rep][opponent][player] = len(interactions)

        return match_lengths
Returns:
dataset/ETHPy150Open Axelrod-Python/Axelrod/axelrod/result_set.py/ResultSet.build_match_lengths