python---ORM之SQLAlchemy（4）relationship多对多练习

练习一：朋友

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

engine = create_engine("mysql+pymysql://root:root@127.0.0.1/t2?charset=utf8")

Base = declarative_base()


class Men_to_Wemon(Base):
    __tablename__ = "men_to_women"

    nid = Column(Integer, primary_key=True)
    men_id = Column(Integer, ForeignKey('men.id'))
    women_id = Column(Integer, ForeignKey('women.id'))

class Men(Base):
    __tablename__ = 'men'

    id = Column(Integer, primary_key=True)
    name = Column(String(40))
    age = Column(String(10))
    #gf = relationship("Women", secondary=Men_to_Wemon.__table__)

class Women(Base):
    __tablename__ = "women"

    id = Column(Integer, primary_key=True)
    name = Column(String(40))
    age = Column(String(10))

    bf = relationship("Men",secondary=Men_to_Wemon.__table__,backref='gf') 
    #backref相当于在men表中加了一个关于women的对象叫gf
　　 #secondary是第三张表，用于多对多
    #bf = relationship("Men",secondary=Men_to_Wemon.__table__)
Base.metadata.create_all(engine)

MySession = sessionmaker(bind=engine)
session = MySession()

m1 = session.query(Men).filter_by(id=2).first()
#所有女
w1 = session.query(Women).all()
m1.gf = w1

session.add(m1)
session.commit()

练习二：主机和分组

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

engine = create_engine("mysql+pymysql://root:root@127.0.0.1/t2?charset=utf8")
Base = declarative_base()

class HostToGroup(Base):
    __tablename__ = 'host_2_group'
    nid = Column(Integer,primary_key=True)
    host_id = Column(Integer,ForeignKey('host.id'))
    group_id = Column(Integer,ForeignKey('group.id'))

class Group(Base):
    __tablename__ = 'group'
    id = Column(Integer,primary_key=True)
    name = Column(String(40),unique=True)

class Host(Base):
    __tablename__ = 'host'
    id = Column(Integer,primary_key=True)
    hostname = Column(String(40),unique=True)
    ip_addr = Column(String(40))
    port = Column(String(10),default=22)
    group = relationship('Group',secondary=HostToGroup.__table__,backref="host_list")

Base.metadata.create_all(engine)

MySession = sessionmaker(bind=engine)
session = MySession()

# g1 = Group(name='g1')
# g2 = Group(name='g2')
# g3 = Group(name='g3')
# g4 = Group(name='g4')
#
# session.add_all([g1,g2,g3,g4])
# session.commit()
#
# h1 = Host(hostname='h1',ip_addr='192.168.0.0.1')
# h2 = Host(hostname='h2',ip_addr='192.168.0.0.2',port=10)
# h3 = Host(hostname='h.',ip_addr='192.168.0.0.3',port=1000)

# h1.group=[g2,g4]
# session.add_all([h1,h2,h3])
# session.commit()

# groups = session.query(Group).all()
# h2 = session.query(Host).filter(Host.hostname=='h2').first()
# h2.group=groups[:-1]
#
# session.add(h2)
# session.commit()

g4 = session.query(Group).filter(Group.name=='g4').first()

obj1 = session.query(Host).filter(Host.hostname=='h2').update({'port':4214})
obj2 = session.query(Host).filter(Host.hostname=='h2').first()

g4.host_list.append(obj2)

session.add(g4)
session.commit()