##. Python's Path to self-study: Reflection (very important programming ideas)

The meaning of reflection: Gets the memory address of a method of a class through a string, and calls the method.

Format: If hasattr(self, ' anattr ')

Func = getattr(self, ' anattr ') #获取内存地址

Func () # calls the method, equivalent to Anattr ()

setattr(x, ' Y ', v　　　　　)

　　　　　delattr (x, ' Y ')

Look at the following example

version One : Inefficient, if the method in the class webserver more than hundred, then the main function of the IF statement will be judged hundreds of times.

ImportSYSclassWebServer (object):def __init__(self,host,port): Self.host=host Self.port=PortdefStart (self):Print("Server is starting ...")    defStop (self):Print("Server is stopping ...")    defRestart (self): Self.stop () Self.start ()if __name__=="__main__": Server= WebServer ('localhost', 333)    Print(Sys.argv[1])#the first parameter when executing a script    ifSYS.ARGV[1] = ='Start': Server.start ()elifSYS.ARGV[1] = ='Stop': Server.stop ()elifSYS.ARGV[1] = ='Restart': Server.restart ()

version Two : the idea of introducing a dictionary, but there is the phenomenon of code reuse, you can continue to improve

ImportSYSclassWebServer (object):def __init__(self,host,port): Self.host=host Self.port=PortdefStart (self):Print("Server is starting ...")    defStop (self):Print("Server is stopping ...")    defRestart (self): Self.stop () Self.start ()if __name__=="__main__": Server= WebServer ('localhost', 333)    Print(sys.argv[1]) Cmd_dic= {        'Start': Server.start,'Stop': Server.stop,}ifSYS.ARGV[1]inchcmd_dic:cmd_dic[sys.argv[1]] ()

version Three : Introducing Reflection

ImportSYSclassWebServer (object):def __init__(self,host,port): Self.host=host Self.port=PortdefStart (self):Print("Server is starting ...")    defStop (self):Print("Server is stopping ...")    defRestart (self): Self.stop () Self.start ()if __name__=="__main__": Server= WebServer ('localhost', 333)    Print(sys.argv[1])    ifHasattr (server, sys.argv[1]): Func= GetAttr (server, sys.argv[1])#Gets the memory address of the Server.startFunc ()#equivalent to Server.start ()

The SetAttr of Reflection method

ImportSYSclassWebServer (object):def __init__(self,host,port): Self.host=host Self.port=PortdefStart (self):Print("Server is starting ...")    defStop (self):Print("Server is stopping ...")    defRestart (self): Self.stop () Self.start ()defTestRun (INS, name):#This method is not a method of class, but it can be bound to an instance using set    Print("running ....", Name,ins.host)#ins equals selfif __name__=="__main__": Server= WebServer ('localhost', 333) Server1= WebServer ('Localhost1', 666)    Print(sys.argv[1])    #setattr (x, ' Y ', V) is equivalent to x.y = vSetAttr (Server,'Run', TestRun)#TestRun is bound to instance server and renamed to runServer.run (Server,'Wuwen')#Passing server to INS (instance)Server1.run (Server,'Wuwen')

The Delattr of Reflection method

classWebServer (object):def __init__(self,host,port): Self.host=host Self.port=PortdefStart (self):Print("Server is starting ...")    defStop (self):Print("Server is stopping ...")    defRestart (self): Self.stop () Self.start ()if __name__=="__main__": Server= WebServer ('localhost', 333) delattr (server,'Stop')#error notation, instance cannot method in parameter class    Print(server.host) delattr (server,'Host')#删除property in the argument instance host    Print(server.host) delattr (WebServer,'Restart')#删除The restart method in the parameter class    Print(Server.restart ())

##. Python's Path to self-study: Reflection (very important programming ideas)