import random
from enum import Enum


class CoinSide(Enum):
    HEADS = 0
    TAILS = 1


class InterviewTallyByDay():
    def __init__(self):
        self.monday = InterviewTally()
        self.tuesday = InterviewTally()


class InterviewTally():
    def __init__(self, heads=0, tails=0):
        self.heads = heads
        self.tails = tails

    def __add__(self, other):
        return InterviewTally(
            heads=self.heads + other.heads,
            tails=self.tails + other.tails,
        )

    def __iadd__(self, other):
        self.heads += other.heads
        self.tails += other.tails
        return self


def toss_coin():
    return random.choice(list(CoinSide))


interview_tallies_by_day = InterviewTallyByDay()
for trial in range(int(1e6)):
    coin_side = toss_coin()

    if coin_side == CoinSide.HEADS:
        interview_tallies_by_day.monday += InterviewTally(heads=1)
        # Not interviewed on Tuesday
    elif coin_side == CoinSide.TAILS:
        interview_tallies_by_day.monday += InterviewTally(tails=1)
        interview_tallies_by_day.tuesday += InterviewTally(tails=1)

interview_tallies = interview_tallies_by_day.monday + \
                    interview_tallies_by_day.tuesday
print 'What your credence now for the proposition that the coin landed heads?'
print interview_tallies.heads / float(interview_tallies.heads + interview_tallies.tails)