from otree.api import *
c = Currency
doc = """
In a common value auction game, players simultaneously bid on the item being
auctioned.
Prior to bidding, they are given an estimate of the actual value of the item.
This actual value is revealed after the bidding.
Bids are private. The player with the highest bid wins the auction, but
payoff depends on the bid amount and the actual value.
"""
class Constants(BaseConstants):
name_in_url = 'second_price_auction'
players_per_group = 2
num_rounds = 10
instructions_template = 'second_price_auction/instructions.html'
min_allowable_bid = c(0)
max_allowable_bid = c(10)
# Error margin for the value estimates shown to the players
estimate_error_margin = c(1)
class Subsession(BaseSubsession):
pass
class Group(BaseGroup):
item_value = models.CurrencyField(
doc="""Common value of the item to be auctioned, random for treatment"""
)
highest_bid = models.CurrencyField()
second_highest_bid = models.CurrencyField()
class Player(BasePlayer):
item_value_estimate = models.CurrencyField(
doc="""Estimate of the common value, may be different for each player"""
)
bid_amount = models.CurrencyField(
min=Constants.min_allowable_bid,
max=Constants.max_allowable_bid,
doc="""Amount bidded by the player""",
label="Bid amount",
)
is_winner = models.BooleanField(
initial=False, doc="""Indicates whether the player is the winner"""
)
# FUNCTIONS
def creating_session(subsession: Subsession):
for g in subsession.get_groups():
import random
item_value = random.uniform(
Constants.min_allowable_bid, Constants.max_allowable_bid
)
g.item_value = round(item_value, 1)
def set_winner(group: Group):
import random
players = group.get_players()
group.highest_bid = max([p.bid_amount for p in players])
players_with_highest_bid = [p for p in players if p.bid_amount == group.highest_bid]
losers = [p for p in players if p.bid_amount < group.highest_bid]
if len(losers)>0:
group.second_highest_bid = max([p.bid_amount for p in losers])
else:
group.second_highest_bid = group.highest_bid
winner = random.choice(
players_with_highest_bid
) # if tie, winner is chosen at random
winner.is_winner = True
for p in players:
set_payoff(p)
def generate_value_estimate(group: Group):
import random
minimum = group.item_value - Constants.estimate_error_margin
maximum = group.item_value + Constants.estimate_error_margin
estimate = random.uniform(minimum, maximum)
estimate = round(estimate, 1)
if estimate < Constants.min_allowable_bid:
estimate = Constants.min_allowable_bid
if estimate > Constants.max_allowable_bid:
estimate = Constants.max_allowable_bid
return estimate
def set_payoff(player: Player):
group = player.group
if player.is_winner:
player.payoff = group.item_value - group.second_highest_bid
if player.payoff < 0:
player.payoff = 0
else:
player.payoff = 0
# PAGES
class Introduction(Page):
@staticmethod
def before_next_page(player: Player, timeout_happened):
group = player.group
player.item_value_estimate = generate_value_estimate(group)
class Bid(Page):
form_model = 'player'
form_fields = ['bid_amount']
class ResultsWaitPage(WaitPage):
after_all_players_arrive = 'set_winner'
class Results(Page):
@staticmethod
def vars_for_template(player: Player):
group = player.group
return dict(is_greedy=group.item_value - player.bid_amount < 0)
page_sequence = [Introduction, Bid, ResultsWaitPage, Results]