如何使用SQLAlchemy在表之間建立關係？

Question

使用SQLAlchemy的，給定的表，如這些：

locations_table = Table('locations', metadata, 
    Column('id',  Integer, primary_key=True), 
    Column('name', Text), 
) 

players_table = Table('players', metadata, 
    Column('id',     Integer, primary_key=True), 
    Column('email',   Text), 
    Column('password', Text), 
    Column('location_id', ForeignKey('locations.id')) 
) 

和類如這些：

class Location(object): 
    def __init__(self, name): 
     self.name = name 

    def __repr__(self): 
     return '<Location: %s, %s>' % (self.name) 

mapper(Location, locations_table) 

class Player(object): 
    def __init__(self, email, password, location_id): 
     self.email = email 
     self.password = password 
     self.location_id = location_id 

    def __repr__(self): 
     return '<Player: %s>' % self.email 

mapper(Player, players_table) 

和這樣的代碼：

location = session.query(Location).first() 
player = session.query(Player).first() 

（簡化的）。

我怎麼會去修改，以支持行動，像這樣的：

# assign location to player using a Location object, as opposed to an ID 
player.location = location 
# access the Location object associated with the player directly 
print player.location.name 

如果SQLAlchemy的許可：

# print all players having a certain location 
print location.players 

？

Answer 1

這應該爲你工作：

映射器（播放器，players_table，性能= { '位置'=關係（位置，uselist =假backref = backref（'players'））}）

這樣你就可以直接訪問該位置，因爲你不會得到一個列表。除此之外，你可以做location.players，它會給你一個InstrumentedList，所以你可以通過球員

Answer 2

使用SQLAlchemy的關係特點：

http://www.sqlalchemy.org/docs/ormtutorial.html#building-a-relation