from otree.api import * c = Currency doc = """ A demo of how rounds work in oTree, in the context of 'matching pennies' """ class Constants(BaseConstants): name_in_url = 'matching_pennies' players_per_group = 2 num_rounds = 4 stakes = c(100) matcher_role = 'Matcher' mismatcher_role = 'Mismatcher' class Subsession(BaseSubsession): pass class Group(BaseGroup): pass class Player(BasePlayer): penny_side = models.StringField( choices=[['Heads', 'Heads'], ['Tails', 'Tails']], widget=widgets.RadioSelect, label="I choose:", ) is_winner = models.BooleanField() opponent_choice = models.StringField() # FUNCTIONS def creating_session(subsession: Subsession): session = subsession.session import random if subsession.round_number == 1: paying_round = random.randint(1, Constants.num_rounds) session.vars['paying_round'] = paying_round if subsession.round_number == 3: # reverse the roles matrix = subsession.get_group_matrix() for row in matrix: row.reverse() subsession.set_group_matrix(matrix) if subsession.round_number > 3: subsession.group_like_round(3) def set_payoffs(group: Group): subsession = group.subsession session = group.session p1 = group.get_player_by_id(1) p2 = group.get_player_by_id(2) for p in [p1, p2]: is_matcher = p.role == Constants.matcher_role p.is_winner = (p1.penny_side == p2.penny_side) == is_matcher if subsession.round_number == session.vars['paying_round'] and p.is_winner: p.payoff = Constants.stakes else: p.payoff = c(0) # PAGES class Choice(Page): form_model = 'player' form_fields = ['penny_side'] @staticmethod def vars_for_template(player: Player): return dict(player_in_previous_rounds=player.in_previous_rounds()) class ResultsWaitPage(WaitPage): after_all_players_arrive = set_payoffs class ResultsSummary(Page): @staticmethod def is_displayed(player: Player): return player.round_number == Constants.num_rounds @staticmethod def vars_for_template(player: Player): session = player.session player_in_all_rounds = player.in_all_rounds() return dict( total_payoff=sum([p.payoff for p in player_in_all_rounds]), player_in_all_rounds=player_in_all_rounds, ) page_sequence = [Choice, ResultsWaitPage, ResultsSummary]