sqlalchemy相关知识

#!/usr/bin/env python3.5
# -*- coding:utf8 -*-
# 多对多关联
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() #生成一个SqlORM 基类
engine = create_engine("mysql+pymysql://python:123456@192.168.1.190:3306/python",echo=True)
# 1、创建一个关联表，关联两个对象 组和主机
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, # 指定中间表的实例
                          backref ='host_list') # backref参数则对关系提供反向引用的声明。
    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) #创建所有表结构
#
if __name__ == '__main__':
    SessionCls = sessionmaker(bind=engine) #创建与数据库的会话session class ,注意,这里返回给session的是个class,不是实例
    session = SessionCls()  # 这才是连接的实例
    # 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])
    '''
    # 关联主机
    # 找组
    g1 = session.query(Group).first()
    # groups = session.query(Group).all()
    # h1 = session.query(Host).filter(Host.hostname == "h1").first()
    # 找主机
    h2 = session.query(Host).filter(Host.hostname == "h2").first()
    # h3 = session.query(Host).filter(Host.hostname == "h3").first()
    # # h1.groups = groups
    # # h1.groups.pop()
    # 关联，使一个主机属于多个组
    # h2.groups = groups[1:-1]
    # 查询
    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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