多对多关系烧瓶sqlalchemy

from sqlalchemy import create_engine, Column, Integer, String, Table, ForeignKey
from sqlalchemy.orm import relationship, sessionmaker
from sqlalchemy.ext.declarative import declarative_base

# 创建数据库连接
engine = create_engine('数据库连接字符串')

# 创建会话工厂
Session = sessionmaker(bind=engine)

# 创建基类
Base = declarative_base()

# 定义中间表
association_table = Table('association', Base.metadata,
    Column('left_id', Integer, ForeignKey('left_table.id')),
    Column('right_id', Integer, ForeignKey('right_table.id'))
)

# 定义左表
class LeftTable(Base):
    __tablename__ = 'left_table'
    id = Column(Integer, primary_key=True)
    name = Column(String)
    right_tables = relationship('RightTable', secondary=association_table, back_populates='left_tables')

# 定义右表
class RightTable(Base):
    __tablename__ = 'right_table'
    id = Column(Integer, primary_key=True)
    name = Column(String)
    left_tables = relationship('LeftTable', secondary=association_table, back_populates='right_tables')

# 创建表格
Base.metadata.create_all(engine)

# 创建会话
session = Session()

# 创建实例
left_table1 = LeftTable(name='LeftTable 1')
left_table2 = LeftTable(name='LeftTable 2')
right_table1 = RightTable(name='RightTable 1')
right_table2 = RightTable(name='RightTable 2')

# 建立关联关系
left_table1.right_tables.append(right_table1)
left_table1.right_tables.append(right_table2)
left_table2.right_tables.append(right_table1)

# 提交到数据库
session.add_all([left_table1, left_table2, right_table1, right_table2])
session.commit()

# 查询关联关系
left_table = session.query(LeftTable).filter_by(name='LeftTable 1').first()
print(left_table.right_tables)