从多对多Sql表构造dict / json对象

Question

继续我的last问题。我在3个表之间定义了结构良好的多对多关系。我可以简单地添加一个这样的用户关联

def setUserAssociation(**kwargs):
    associations = {}
    assoc = UserDevices() #Table object that stores all associations (see my last question)
    try:
        for table in kwargs:
            validTables = ["Site", "User", "Device", "Role"]
            if table not in validTables:
                raise ValueError("Unknown table `" + table + "` must be " + str(validTables))
            associations[table] = db.session.query(eval(k)).filter(eval(table).name==kwargs[table]).first()
            if associations[table] is None:
                raise ValueError("No " + table + " found with name `" + str(kwargs[table]) + "`")
            setattr(assoc, table .lower(), associations[table])
        db.session.add(assoc)
        db.session.commit()
        return SqlResponse(200, "Success")
    except Exception as e:
        print(e)
        return SqlResponse(500, str(e))

最后在站点Anum上添加用户myHome并在设备owner上为其分配角色myPlug

response = setUserAssociation(Site="myHome", User="Anum", Device="myPlug", Role="owner")

足够好！现在说我有一个结构如下的复杂表；

我想将此表构造​​为Json或Dict对象。调用getUserAssociation时，我可以获取（UserDevice对象类型的用户关联列表）

def getUserAssociation(userName):
    user = db.session.query(User).filter(User.name == userName).first()
    return user.user_devices

userAssoc = getUserAssociation("Anum")
for u in userAssoc:
    print ("data: ", u.user.name, u.site.name, u.device.name, u.role.name)

这给了我UserDevice对象的列表（每行）。当然，我可以使用上面的数据创建自己的wild方法来创建json（如下所示），但是...还有其他简便的方法吗？也许SqlAlchemy已经提供了一个？

{
    "sites": [
        {
            "site": "myHome",
            "devices": [
                {
                    "device": "plug",
                    "users": [
                        "{'user': 'John', 'role': 'owner'}",
                        "{'user': 'Steve', 'role': 'writer'}"
                    ]
                },
                {
                    "device": "fan",
                    "users": [
                        "{'user': 'Henry', 'role': 'manager'}",
                        "{'user': 'John', 'role': 'owner'}"
                    ]
                }
            ]
        }
    ]
}