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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