tournament.py

#!/usr/bin/env python
#
# tournament.py -- implementation of a Swiss-system tournament
#

import psycopg2


def connect():
    """Connect to the PostgreSQL database.  Returns a database connection."""
    return psycopg2.connect("dbname=tournament")


def deleteMatches():
    """Remove all the match records from the database."""
    conn = connect()
    c = conn.cursor()
    c.execute('''DELETE FROM match_rec;''')
    conn.commit()
    conn.close()



def deletePlayers():
    """Remove all the player records from the database."""
    conn = connect()
    c = conn.cursor()
    c.execute('''DELETE FROM player_rec;''')
    conn.commit()
    conn.close()


def countPlayers():
    """Returns the number of players currently registered."""
    conn = connect()
    c = conn.cursor()
    c.execute('''SELECT COUNT(*) FROM player_rec;''')
    result = c.fetchone()
    conn.close()
    return result[0]


def registerPlayer(name):
    """Adds a player to the tournament database.

    The database assigns a unique serial id number for the player.  (This
    should be handled by your SQL database schema, not in your Python code.)

    Args:
      name: the player's full name (need not be unique).
    """
    conn = connect()
    c = conn.cursor()
    c.execute('''INSERT INTO player_rec (name)
                 VALUES (%s);''', (name,))
    conn.commit()
    conn.close()


def playerStandings():
    """Returns a list of the players and their win records, sorted by wins.

    The first entry in the list should be the player in first place, or a player
    tied for first place if there is currently a tie.

    Returns:
      A list of tuples, each of which contains (id, name, wins, matches):
        id: the player's unique id (assigned by the database)
        name: the player's full name (as registered)
        wins: the number of matches the player has won
        matches: the number of matches the player has played
    """
    conn = connect()
    c = conn.cursor()
    c.execute('''SELECT * FROM standings_view ORDER BY wins DESC''')
    result = c.fetchall()
    conn.close()
    return result


def reportMatch(winner, loser):
    """Records the outcome of a single match between two players.

    Args:
      winner:  the id number of the player who won
      loser:  the id number of the player who lost
    """
    conn = connect()
    c = conn.cursor()
    c.execute('''INSERT INTO match_rec (winner, loser)
                 VALUES (%s,%s);''', [(winner,),(loser,)])
    conn.commit()
    conn.close()


def swissPairings():
    """Returns a list of pairs of players for the next round of a match.

    Assuming that there are an even number of players registered, each player
    appears exactly once in the pairings.  Each player is paired with another
    player with an equal or nearly-equal win record, that is, a player adjacent
    to him or her in the standings.

    Returns:
      A list of tuples, each of which contains (id1, name1, id2, name2)
        id1: the first player's unique id
        name1: the first player's name
        id2: the second player's unique id
        name2: the second player's name
    """
    conn = connect()
    c = conn.cursor()
    c.execute('''SELECT id FROM standings_view ORDER BY wins DESC;''')
    ids = c.fetchall()

    c.execute('''SELECT name FROM standings_view ORDER BY wins DESC;''')
    names = c.fetchall()

    player_list = []
    id_count = 0
    name_count = 0

    for i in range(len(ids) / 2):
        player_list.extend(zip(ids[id_count],
                           names[name_count],
                           ids[id_count + 1],
                           names[name_count + 1]))
        id_count += 2
        name_count += 2

    conn.close()
    return player_list