米ハーバード大学 CS50：課題「どの国がワールドカップで優勝するかをシミュレーションする」の回答例（Harvard CS50 Week 6 Python − Lab 6: World Cup） 

team,rating
Uruguay,976
Portugal,1306
France,1166
Argentina,1254
Brazil,1384
Mexico,1008
Belgium,1346
Japan,528
Spain,1162
Russia,493
Croatia,975
Denmark,1054
Sweden,889
Switzerland,1179
Colombia,989
England,1040

team,rating
Norway,1915
Australia,2003
England,2049
Cameroon,1499
France,2043
Brazil,1944
Spain,1913
United States,2101
Italy,1868
China PR,1866
Netherlands,1967
Japan,1991
Germany,2072
Nigeria,1599
Sweden,1962
Canada,2006

# Simulate a sports tournament

import csv
import sys
import random

# Number of simluations to run
N = 1000


def main():

    # Ensure correct usage
    if len(sys.argv) != 2:
        sys.exit("Usage: python tournament.py FILENAME")

    # Read teams into memory
    teams = []
    filename = sys.argv[1]
    with open(filename) as f:
        reader = csv.DictReader(f)
        for team in reader:
            team["rating"] = int(team["rating"])
            teams.append(team)

    # Keep track of number of wins for each team
    counts = {}
    for i in range(N):
        winner = simulate_tournament(teams)
        if winner in counts:
            counts[winner] += 1
        else:
            counts[winner] = 1

    # Print each team's chances of winning, according to simulation
    for team in sorted(counts, key=lambda team: counts[team], reverse=True):
        print(f"{team}: {counts[team] * 100 / N:.1f}% chance of winning")


def simulate_game(team1, team2):
    """Simulate a game. Return True if team1 wins, False otherwise."""
    rating1 = team1["rating"]
    rating2 = team2["rating"]
    probability = 1 / (1 + 10 ** ((rating2 - rating1) / 600))
    return random.random() < probability


def simulate_round(teams):
    """Simulate a round. Return a list of winning teams."""
    winners = []

    # Simulate games for all pairs of teams
    for i in range(0, len(teams), 2):
        if simulate_game(teams[i], teams[i + 1]):
            winners.append(teams[i])
        else:
            winners.append(teams[i + 1])

    return winners


def simulate_tournament(teams):
    """Simulate a tournament. Return name of winning team."""
    while len(teams) > 1:
        teams = simulate_round(teams)
    return teams[0]["team"]


if __name__ == "__main__":
    main()