SQLAlchemy：不确定DB设置是否正确

Question

我尝试使用SQLAlchemy在Python中设置我的数据库。我有一个像这样的Player类：

class Player:
    def __init__(self,  rating, college, ranking = None, firstName = None, lastName = None):
        self.rating = rating
        self.college = college
        self.ranking = ranking
        self.firstName = firstName
        self.lastName = lastName

然后我在一个名为databaseFunctions.py的模块中有一些特定于数据库的方法：

#if player exists, update his rating and ranking; otherwise, add new object to DB
def updateSpecificDBEntry(playerObject, session):
    #find player in DB with firstName and lastName
    currentPlayer = session.query(Player).filter(firstName == playerObject.firstName).filter(playerObject.lastName == lastName).first()
    #set rating = newRating
    if currentPlayer.count():
        currentPlayer.rating = playerObject.rating
        currentPlayer.ranking = playerObject.ranking
    else:
        addEntryToDB(playerObject, session)

def updateEntireDB(arrayOfPlayerObjects, session):
    for player in arrayOfPlayerObjects:
        updateSpecificDBEntry(player, session)

我的主要方法非常基础：

def main():
    #create engine (for use by base and session)
    engine = databaseFunctions.createEngine()
    #create session
    session = databaseFunctions.createSession(engine)
    #get all players from CSA website
    allPlayers = getSortedGender(constants.mainURL, constants.menTeams)
    databaseFunctions.updateEntireDB(allPlayers, session)
    databaseFunctions.findPlayerWithRanking(100, session)

几个问题：

1）我在最后一次函数调用时遇到错误。这是错误消息：

  File "helpfulFunctions.py", line 116, in <module>
    main()
  File "helpfulFunctions.py", line 108, in main
    databaseFunctions.updateEntireDB(allPlayers, session)
  File "/Users/benjaminclayman/Desktop/SquashScraper/databaseFunctions.py", line 42, in updateEntireDB
    updateSpecificDBEntry(player, session)
  File "/Users/benjaminclayman/Desktop/SquashScraper/databaseFunctions.py", line 34, in updateSpecificDBEntry
    if currentPlayer.count():
AttributeError: 'NoneType' object has no attribute 'count'

SQLAlchemy不喜欢我使用if currentPlayer.count()，其中currentPlayer是从我的SQLAlchemy查询返回的对象。我很困惑，因为我查看了文档，而SQLAlchemy 有count()方法：

2）我试图在我的DB中找到排名为100的玩家对象。但看起来我的查询返回None对象（如currentPlayer），这是非常令人惊讶的。我显然做错了什么。

我基本上刮掉所有玩家，将它们变成玩家对象，对它们进行排序，然后循环并给出正确的排名。然后我使用以下方法将所有这些添加到数据库中。所以 应该是数据库中排名为100的玩家（有大约650名玩家被刮掉）。

知道这里发生了什么吗？

感谢您的帮助， bclayman

编辑以显示由我的代码生成的SQL示例：

2015-06-16 20:05:33,664 INFO sqlalchemy.engine.base.Engine ('Lilliian A.', 'Wacker', 1, 0)
2015-06-16 20:05:33,666 INFO sqlalchemy.engine.base.Engine INSERT INTO players ("firstName", "lastName", college, ranking, rating) VALUES (?, ?, ?, ?, ?)
2015-06-16 20:05:33,666 INFO sqlalchemy.engine.base.Engine (652, 'Lilliian A.', 'Boston University', 'Wacker', 2.51)
2015-06-16 20:05:33,667 INFO sqlalchemy.engine.base.Engine COMMIT
2015-06-16 20:05:33,669 INFO sqlalchemy.engine.base.Engine BEGIN (implicit)
2015-06-16 20:05:33,670 INFO sqlalchemy.engine.base.Engine SELECT players.id AS players_id, players."firstName" AS "players_firstName", players."lastName" AS "players_lastName", players.college AS players_college, players.ranking AS players_ranking, players.rating AS players_rating
FROM players
WHERE players."firstName" = ? AND players."lastName" = ?
 LIMIT ? OFFSET ?

看起来像这部分：

2015-06-16 20：05：33,666 INFO sqlalchemy.engine.base.Engine INSERT INTO玩家（＆＃34; firstName＆＃34;，＆＃34; lastName＆＃34;，大学，排名，评级）VALUES （？，？，？，？，？）

可能没有在玩家表中插入任何内容...

想法？