ranking_app.py

import sys
import json
from trueskill import Rating, rate_1vs1, rate

"""
Python cli ranking

sudo pip install trueskill

To test:
echo '[{"name": "davm","mu": 25.0,"sigma": 8.55,"rank": 1},{"name": "thom","mu": 25.0,"sigma": 8.55,"rank": 2}]' \
| python ranking_app.py

Echoes back the same json but with updated mu and sigma.
"""
def create_players(res_list):
    """
    Creates a dict of {'player_name': player_rating} for each list items
    """
    return {p['name']: Rating(mu=p['mu'], sigma=p['sigma']) for p in res_list}

def create_teams(res_list):
    """
    Creates a dict of {'team_number': ['player_name1', 'player_name2']}
    for each list items
    """
    v = {}
    ranks = list(set([l['rank'] for l in res_list]))

    for line in res_list:
        # winner if has the minimum rank
        key = 0 if line['rank'] == min(ranks) else 1
        value = line['name']
        if key in v.keys():
            v[key].append(value)
        else:
            v[key] = [value]
    return v


def get_new_ratings(players, teams):
    """
    Affect new ratings to players from teams results
    """
    nb_players_team0 = len(teams[0])
    nb_players_team1 = len(teams[1])
    winner = players[teams[0][0]]
    loser = players[teams[1][0]]
    if nb_players_team0 == 1 and nb_players_team1 == 1:
        new_r1, new_r3 = rate_1vs1(winner,loser)
    elif nb_players_team0 == 1 and nb_players_team1 > 1:
        team_loser = [loser, players[teams[1][1]]]
        (new_r1), (new_r3, new_r4) = rate([winner, team_loser], ranks=[0, 1])  
    elif nb_players_team0 > 1 and nb_players_team1 == 1:
        team_winner = [winner, players[teams[0][1]]]
        (new_r1, new_r2), (new_r3) = rate([team_winner, loser], ranks=[0, 1])  
    else:
        team_loser = [loser, players[teams[1][1]]]
        team_winner = [winner, players[teams[0][1]]]
        (new_r1, new_r2), (new_r3, new_r4) = rate([team_winner, team_loser], ranks=[0, 1])  
    player1 = {'name': teams[0][0], 'mu': new_r1.mu, 'sigma': new_r1.sigma}
    player3 = {'name': teams[1][0], 'mu': new_r3.mu, 'sigma': new_r3.sigma}
    if nb_players_team0 > 1:
        player2 = {'name': teams[0][1], 'mu': new_r2.mu, 'sigma': new_r2.sigma}
    if nb_players_team1 > 1:
        player4 = {'name': teams[1][1], 'mu': new_r4.mu, 'sigma': new_r4.sigma}
        if nb_players_team0 > 1:
            return [player1, player2, player3, player4]
        return [player1, player2, player4]
    return [player1, player3]

jsonData = sys.stdin.readline()
data = json.loads(jsonData)
players = create_players(data)
teams = create_teams(data)
print json.dumps(get_new_ratings(players, teams))