sqlalchemy相關知識

 #!/usr/bin/env python3.5

 # -*- coding:utf8 -*-

 # 多對多關聯

 from sqlalchemy import Table, Column, Integer, ForeignKey,String,create_engine,and_,or_,func

 from sqlalchemy.orm import relationship,sessionmaker

 from sqlalchemy.ext.declarative import declarative_base

 Base = declarative_base() #生成一個SqlORM 基類

 engine = create_engine("mysql+pymysql://python:[email protected]:3306/python",echo=True)

 # 1、建立一個關聯表，關聯兩個物件 組和主機

 Host2Group = Table('host_2_group',Base.metadata,

                     Column('host_id',ForeignKey('hosts.id'),primary_key=True),

                     Column('group_id',ForeignKey('group.id'),primary_key=True),

                     )

 class Host(Base):

     __tablename__ = 'hosts'

     id = Column(Integer,primary_key=True,autoincrement=True)

     hostname = Column(String(64),unique=True,nullable=False)

     ip_addr = Column(String(128),unique=True,nullable=False)

     port = Column(Integer,default=22)

     groups = relationship("Group",

                           secondary=Host2Group, # 指定中間表的例項

                           backref ='host_list') # backref引數則對關係提供反向引用的宣告。

     def __repr__(self):

          return "<id =%s,hostname=%s,ip_addr =%s>"%\

                (self.id,

                 self.hostname,

                 self.ip_addr)

 class Group(Base):

     __tablename__ ="group"

     id = Column(Integer,primary_key=True)

     name = Column(String(64),unique=True,nullable=False)

     def __repr__(self):

         return "<group_id =%s,group_name=%s>"%\

                 (self.id,

                 self.name)

 Base.metadata.create_all(engine) #建立所有表結構

 #

 if __name__ == '__main__':

     SessionCls = sessionmaker(bind=engine) #建立與資料庫的會話session class ,注意,這裡返回給session的是個class,不是例項

     session = SessionCls()  # 這才是連線的例項

     # g1 = Group(name = "g1")

     # g2 = Group(name = "g2")

     # g3 = Group(name = "g3")

     # g4 = Group(name = "g4")

     '''

     h1 = Host(hostname='h1',ip_addr='192.168.2.242',port = 2000)

     h2 = Host(hostname='h2',ip_addr='192.168.2.243',port=20000)

     h3 = Host(hostname='h3',ip_addr='192.168.2.244',port=20000)

     session.add_all([h1,h2,h3])

     '''

     # 關聯主機

     # 找組

     g1 = session.query(Group).first()

     # groups = session.query(Group).all()

     # h1 = session.query(Host).filter(Host.hostname == "h1").first()

     # 找主機

     h2 = session.query(Host).filter(Host.hostname == "h2").first()

     # h3 = session.query(Host).filter(Host.hostname == "h3").first()

     # # h1.groups = groups

     # # h1.groups.pop()

     # 關聯，使一個主機屬於多個組

     # h2.groups = groups[1:-1]

     # 查詢

     print("======>",h2.groups)

     print("=====>",g1.host_list)

     # update

     # obj = session.query(Host).filter(Host.hostname == "test_localhost").first()

     # print("++>",obj)

     # #obj.hostname = "test_localhost"  # 更改

     # session.delete(obj)

     # objs = session.query(Host).filter(and_(Host.hostname.like("ubun%"),Host.port > 20)).all()

     # print("+++>",objs)

     session.commit()

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