CS50 lab6世界杯simulate_tournament功能问题

Question

我的tournament.py 程序似乎工作正常，但通过 check50 运行它会出现一些错误，特别是使用simulate_tournament 函数时，表示它无法正确返回获胜者的姓名。这是我的代码：

# 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")

    teams = []
    # TODO: Read teams into memory from file
    f = open(sys.argv[1], "r")
    handle = csv.DictReader(f)
    for item in handle:
        item['rating'] = int(item['rating'])
        teams.append(item)

    counts = {}
    # TODO: Simulate N tournaments and keep track of win counts
    for i in range(N):
        winner = simulate_tournament(teams)
        if winner['team'] in counts:
            counts[winner['team']] += 1
        else:
            counts[winner['team']] = 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."""
    # TODO
    while len(teams) != 1:
        teams = simulate_round(teams)
    return teams[0]


if __name__ == "__main__":
    main()

和输出：

Brazil: 22.3% chance of winning
Belgium: 20.8% chance of winning
Portugal: 15.0% chance of winning
Switzerland: 10.8% chance of winning
Spain: 10.2% chance of winning
Argentina: 6.6% chance of winning
England: 3.4% chance of winning
France: 3.4% chance of winning
Denmark: 2.8% chance of winning
Croatia: 1.4% chance of winning
Colombia: 1.4% chance of winning
Mexico: 1.1% chance of winning
Sweden: 0.6% chance of winning
Uruguay: 0.2% chance of winning

可能是什么原因造成的？我仍然不太熟悉 python 中的列表和字典，或者一般的 python。

这是 check50 的结果：

:) tournament.py exists
:) tournament.py imports
:( simulate_tournament handles a bracket of size 2
    simulate_tournament fails to return the name of 1 winning team
:( simulate_tournament handles a bracket of size 4
    simulate_tournament fails to return the name of 1 winning team
:( simulate_tournament handles a bracket of size 8
    simulate_tournament fails to return the name of 1 winning team
:( simulate_tournament handles a bracket of size 16
    simulate_tournament fails to return the name of 1 winning team
:) correctly keeps track of wins
:) correctly reports team information for Men's World Cup
:) correctly reports team information for Women's World Cup

Answer 1

感谢您的回答 Gennaro，这给了我一个想法来定义 simulate_tournament 函数，如下所示，它也起作用了：

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

看到获胜者成为一个字典，它具有与关键“团队”相关的值，这个值就是获胜者的名字。

Answer 2

simulate_tournament(teams) 必须返回一个字符串（而不是列表）。这是一个测试要求。

Answer 3

返回获胜团队的名称就足够了：

def simulate_tournament(teams):
    while len(teams) != 1:
        teams = simulate_round(teams)

    return teams[0]["team"]

Answer 4

我不知道为什么，但 check50 无法识别“名称”，我使用以下代码解决了问题：

def simulate_tournament(teams):
# Simulate a tournament. Return name of winning team.
teamleft =list()
teamsLeft = teams
while len(teamsLeft) != 1:
    teamsLeft = simulate_round(teamsLeft)
winner=teamsLeft[0]
winnerValues = list(winner.values())
return winnerValues[0]

我创建了一个列表，其中包含获胜国家/地区的名称及其排名，然后我返回列表 [0]，因此名称，这有效。