from otree.api import *
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 C(BaseConstants):
NAME_IN_URL = 'common_value_auction'
PLAYERS_PER_GROUP = None
NUM_ROUNDS = 1
INSTRUCTIONS_TEMPLATE = 'common_value_auction/instructions.html'
BID_MIN = cu(0)
BID_MAX = cu(10)
# Error margin for the value estimates shown to the players
BID_NOISE = cu(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()
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=C.BID_MIN,
max=C.BID_MAX,
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(C.BID_MIN, C.BID_MAX)
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]
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
estimate = group.item_value + random.uniform(-C.BID_NOISE, C.BID_NOISE)
estimate = round(estimate, 1)
if estimate < C.BID_MIN:
estimate = C.BID_MIN
if estimate > C.BID_MAX:
estimate = C.BID_MAX
return estimate
def set_payoff(player: Player):
group = player.group
if player.is_winner:
player.payoff = group.item_value - player.bid_amount
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]