0
我有两个表,并且定义了一个一对多的关系。与sqlalchemy的关系的动态行为
from sqlalchemy import Column, Integer, ForeignKey
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship
Base = declarative_base()
class Parent(Base):
__tablename__ = 'parent'
id = Column(Integer, primary_key=True)
children = relationship("Child", backref="parent")
class Child(Base):
__tablename__ = 'child'
id = Column(Integer, primary_key=True)
parent_id = Column(Integer, ForeignKey('parent.id'))
如果我尝试访问Child.parent,我得到一个错误。 但是,如果我初始化一个孩子的实例错误消失。
我想初始化一个Child实例修改Child类,但我不明白如何。 如何在不创建Child实例的情况下访问Child.parent?
In [1]: Child.parent
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
<ipython-input-2-8b757eeb36c4> in <module>()
----> 1 Child.parent
AttributeError: type object 'Child' has no attribute 'parent'
In [2]: Child()
Out[2]: <etl.es_utils.test_to_rm.Child at 0x7f38caf42c50>
In [3]: Child.parent