My tournament.py program seems to work fine but running it through check50 gives a few errors, specifically with the simulate\_tournament function, saying it doesn't correctly return the name of the winner. Here's my code:

```
# 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()

```

and the output:

```
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

```

What could be causing this? I'm still not very familiar with lists and dicts in python, or python in general for that matter.

here is check50's results:

```
:) 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

```