SQLAlchemy在循环中生成包含条件的查询

Question

我正在用Flask搭建一个网页应用，里面用到了SQLAlchemy。我有一个叫“get_team()”的函数，让我头疼不已。

    def get_team(playerlist)
        cond = and_(*[Team.users.contains(p) for p in playerlist ])
        q = Team.query.filter(cond)
         ...

我总是收到一个错误信息：“AttributeError: 'unicode' object has no attribute '_sa_instance_state'”。这是我的模型长什么样：

class Team(db.Model):                                                            
    __tablename__ = 'teams'                                                      

    id = db.Column(db.Integer, primary_key=True)                                 
    users = association_proxy("user_associations", "user", creator=lambda u: Teaming(user=u))

    def __repr__(self):                                                          
        s = ""                                                                   
        for u in self.users:                                                     
            s = s + u.username + ", "                                            

        return "Team {tid}: {users_string}".format(tid = self.id, users_string=s)

class Teaming(db.Model):                                                         
    __tablename__ = 'teaming'                                                    

    team_id = db.Column(db.Integer, db.ForeignKey('teams.id'), primary_key=True) 
    user_id = db.Column(db.Integer, db.ForeignKey('users.id'), primary_key=True) 

    user = db.relationship("User", backref="team_associations")                  
    team = db.relationship("Team", backref="user_associations")                  

    def __repr__(self):                                                          
        return "".format(uid = self.user_id, tid = self.team_id)

class User(UserMixin, db.Model):                                                 
    __tablename__ = 'users'                                                      

    id = db.Column(db.Integer, primary_key=True)                                 

    email = db.Column(db.String(64), unique=True, index=True)                    
    username = db.Column(db.String(64), unique=True, index=True)                 
    password_hash = db.Column(db.String(128))                                    
    confirmed = db.Column(db.Boolean, default=False)                             

    teams = association_proxy("team_associations", "team", creator = lambda t: Teaming(team=t))

如果能给点建议，我会非常感激！

Answer 1

最可能的原因是，playerlist 不是一个包含 User 实例的列表，而是一些字符串（可能是名字）。contains 这个方法只能在模型实例上使用。如果你想处理其他属性，可以使用 any。

def get_team_of_players(playerlist):
    cond = and_(*[Team.users.contains(p) for p in playerlist])
    q = Team.query.filter(cond)
    return q

p1, p2 = db.session.query(User).get(1), db.session.query(User).get(2)
q = get_team_of_players([p1, p2]).all()


def get_team_of_usernames(usernames):
    cond = and_(*[Team.users.any(User.username == p) for p in usernames])
    q = Team.query.filter(cond)
    return q

p1, p2 = 'user1', 'user2'
q = get_team_of_usernames([p1, p2]).all()