pip install SQLAlchemy

# 导入:from sqlalchemy import Column, String, create_engine,ForeignKeyfrom sqlalchemy.orm import sessionmaker,relationshipfrom sqlalchemy.ext.declarative import declarative_base# 创建对象的基类:Base = declarative_base()# 初始化数据库连接(postgresql默认使用psycopg2驱动，可省略):engine = create_engine(‘postgresql+psycopg2://username:password@host:post/dbname‘)# 创建DBSession类型:DBSession = sessionmaker(bind=engine)# 定义User对象:class User(Base):    # 表的名字:    __tablename__ = ‘test2‘    # 表的结构:    id = Column(String(20), primary_key=True)    name = Column(String(20))    # 一对多:    books=relationship(‘Book‘)class Book(Base):    # 表的名字:    __tablename__ = ‘test3‘    # 表的结构:    id = Column(String(20), primary_key=True)    name = Column(String(20))    # “多”的一方的book表是通过外键关联到user表的:    user_id=Column(String(20),ForeignKey(‘test2.id‘))    session=DBSession()new_user=User(id=‘5‘,name=‘Bob‘)session.add(new_user)new_book=Book(id=‘1‘,name=‘linux‘,user_id=‘5‘)session.add(new_book)new_book=Book(id=‘2‘,name=‘python‘,user_id=‘5‘)session.add(new_book)session.commit()session.close()session=DBSession()user=session.query(User).filter(User.id==‘5‘).one()print ‘type:‘,type(user)print ‘name:‘,user.nameprint ‘books:‘,user.bookssession.close()