SQLAlchemy Related knowledge

1 #!/usr/bin/env python3.52 #-*-Coding:utf8-*-3 #Many-to-many associations4  fromSQLAlchemyImportTable, Column, Integer, Foreignkey,string,create_engine,and_,or_,func5  fromSqlalchemy.ormImportRelationship,sessionmaker6  fromSqlalchemy.ext.declarativeImportDeclarative_base7Base = Declarative_base ()#generates a Sqlorm base class8Engine = Create_engine ("Mysql+pymysql://python:[email Protected]:3306/python", echo=True)9 #1. Create an association table that associates two groups of objects and hostsTenHost2group = Table ('Host_2_group', Base.metadata, OneColumn ('host_id', ForeignKey ('hosts.id'), primary_key=True), AColumn ('group_id', ForeignKey ('group.id'), primary_key=True), -                     ) -  the classHost (Base): -     __tablename__='hosts' -id = Column (integer,primary_key=true,autoincrement=True) -hostname = Column (String), unique=true,nullable=False) +IP_ADDR = Column (String), unique=true,nullable=False) -Port = Column (integer,default=22) +Groups = Relationship ("Group", ASecondary=host2group,#specifying an instance of an intermediate table atBackref ='host_list')#The backref parameter provides a declaration of a reverse reference to the relationship.  -     def __repr__(self): -          return "<id =%s,hostname=%s,ip_addr =%s>"% - (Self.id, - Self.hostname, - self.ip_addr) in classGroup (Base): -     __tablename__="Group" toid = Column (integer,primary_key=True) +Name = Column (String), unique=true,nullable=False) -     def __repr__(self): the         return "<group_id =%s,group_name=%s>"% * (Self.id, $ self.name)Panax Notoginseng  -  theBase.metadata.create_all (Engine)#Create all table Structures + # A if __name__=='__main__': theSessioncls = Sessionmaker (bind=engine)#create a session with the database sessions class, note that this is a class that is returned to the session, not an instance +Session = SESSIONCLS ()#This is the instance of the connection. -     #G1 = Group (name = "G1") $     #g2 = Group (name = "G2") $     #g3 = Group (name = "G3") -     #G4 = Group (name = "G4") -     " " the H1 = Host (hostname= ' H1 ', ip_addr= ' 192.168.2.242 ', port = $) - h2 = Host (hostname= ' H2 ', ip_addr= ' 192.168.2.243 ', port=20000)Wuyi h3 = Host (hostname= ' H3 ', ip_addr= ' 192.168.2.244 ', port=20000) the Session.add_all ([h1,h2,h3]) -     " " Wu     #Associated host -     #Find a group AboutG1 =session.query (Group). First () $     #groups = Session.query (Group). All () -     #H1 = Session.query (Host). Filter (Host.hostname = = "H1"). First () -     #Find a host -H2 = Session.query (Host). Filter (Host.hostname = ="H2"). First () A     #h3 = Session.query (Host). Filter (Host.hostname = = "H3"). First () +     ## h1.groups = Groups the     ## H1.groups.pop () -     #Association to make a host belong to more than one group $     #h2.groups = groups[1:-1] the     #Enquiry the     Print("======>", h2.groups) the     Print("=====>", G1.host_list) the     #Update -     #obj = session.query (Host). Filter (Host.hostname = = "Test_localhost"). First () in     #print ("++>", obj) the     ##obj. hostname = "Test_localhost" # change the     #session.delete (obj) About     #Objs = Session.query (Host). Filter (And_ (Host.hostname.like ("ubun%"), Host.port >). All () the     #print ("+++>", Objs) the  the  +Session.commit ()

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SQLAlchemy Related knowledge