eine Liste von Tupeln von Datenbank-Datensatz mit Python und postgresql

Question

Hallo Ich versuche, eine harte Zeit, um diese Funktion zu machen, in dem ich muß:

"""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 
""" 

zur Zeit habe ich diese Funktion, um zu versuchen zu lösen, dass

Traceback (most recent call last): File "tournament_test.py", line 152, in testStandingsBeforeMatches() File "tournament_test.py", line 61, in testStandingsBeforeMatches raise ValueError("Each playerStandings row should have four columns.") ValueError: Each playerStandings row should have four columns.

Linie 152 in Turnier:: ich erhalte diesen Fehler msg

def playerStandings(): 
    conn = connect() 
    c = conn.cursor() 
    c.execute("SELECT id, name \ 
      FROM players LEFT JOIN matches \ 
      ON players.id = matches.id_winner \ 
      ORDER BY players.id") 
    result = c.fetchall() 
    conn.close() 
    return result 

und wenn ich den Code ausführen _test.py ist:

testStandingsBeforeMatches() 

und die Leitung 61 ist:

if len(standings[0]) != 4: 
    raise ValueError("Each playerStandings row should have four columns.") 
[(id1, name1, wins1, matches1), (id2, name2, wins2, matches2)] = standings 

und schließlich Variable "Tabellen" ist ein Aufruf an meine Funktion playerStandings() in Zeile 54

standings = playerStandings() 

Diese ist mein SQL-Skript zum Erstellen der Datenbank und der Tabellen:

CREATE DATABASE tournament; 
\c tournament; 
CREATE TABLE players (id SERIAL, name TEXT, PRIMARY KEY (id)); 
CREATE TABLE matches (
    id_match SERIAL, 
    id_winner SERIAL REFERENCES players(id), 
    id_looser SERIAL REFERENCES players(id), 
    PRIMARY KEY (id_match) 
); 

was kann ich tun, um das zu lösen? Ich bin wirklich neu mit Python, so verstehe ich es nicht sehr gut

Answer 1

Ich verwende nicht postgresql, kann der Code nicht in Ihrer Routine direkt verwenden, so dass Sie auf dieser Basis ändern müssen, damit es funktioniert. Ich gebe Ihnen nur ein paar Hinweise, wie Sie das Problem beheben können.

def playerStandings(): 
    conn = connect() 
    c = conn.cursor() 
    c.execute("SELECT id, name \ 
      FROM players LEFT JOIN matches \ 
      ON players.id = matches.id_winner \ 
      ORDER BY players.id") 
    result = c.fetchall()#get all id and name, I don't know the type of result, assume its a list of dicts. 

    for row in result: 
     #sql to get wins 
     c.execute("SELECT COUNT(*) AS wins FROM WHERE id_winner = row['id']"); 
     win_data = c.fetch() 
     row['wins'] = win_data['wins'] 
     #sql to get matches 
     c.execute("SELECT COUNT(*) AS matches FROM WHERE id_winner = row['id']" OR id_looser = row['id']) 
     match_data = c.fetch() 
     row['matches'] = match_data['matches'] 

    conn.close() 
    return result