python--Decorator

A simple decorative device

1. Why use adorners

The function of the adorner: the function of the original function is extended without modifying the original function and its calling mode

The essence of adorners: a closure function

look at a simple decorator: the ability to calculate the execution time of each function

Import TimedefWrapper (func):definner (): Start=time.time () func () End=time.time ()Print(end-start)returnInnerdefhahaha (): Time.sleep (1)        Print('AAAAA') hahaha=wrapper (hahaha) hahaha ()

calculate the execution time of a function

2. Grammar Sugar

 import   time  def   wrapper (func):  def   inner (): Start  =time.time () F UNC () End  =time.time ()   Print  (End-start)  return   inner@wrapper  def  KKK (): #      print  ( " aaaaa  "  ) KKK ()  

Decorator-Grammar sugar

Adorner with Parameters

Import TimedefTimer (func):defInner (*args,**Kwargs): Start=time.time () re= Func (*args,**Kwargs) End=time.time ()Print(end-start)returnRereturnInner@timer#==> func1 = Timer (func1)defFunc1 (A, b):Print('In func1')    Print(A, b) @timer#==> func1 = Timer (func1)defFunc2 (a):Print('In Func2 and get a:%s'%(a))return 'fun2 over'Func1 (The)Print(Func2 ('aaaaaa'))

the original function adorner with multiple parameters

Adorner with return value

Import TimedefTimer (func):defInner (*args,**Kwargs): Start=time.time () re= Func (*args,**Kwargs) End=time.time ()Print(End-start)returnRereturnInner@timer#==> func1 = Timer (func1)defJJJ (a):Print('In jjj and get a:%s'%(a))return 'fun2 over'JJJ ('aaaaaa')Print(JJJ ('aaaaaa'))

adorner with return value

Ii. the principle of open closure

1. Open for expansion

2. The modification is closed

Three, the fixed structure of the adorner

Import TimedefWrapper (func):#Decorative Device    defInner (*args, * *Kwargs):" "content extension prior to function execution" "ret= Func (*args, * *Kwargs)" "content extension prior to function execution" "        returnretreturnInner@wrapper#=====>aaa=timmer (AAA)defaaa (): Time.sleep (1)    Print('FDFGDG') AAA ()

Fixed Format

Four, with parameters of the adorner

Adorner with parameters: it is to pass the parameter to the adorner

Function: is when added a lot of decorations, and now suddenly do not want to add a decorator, want to remove the adorner, but so much code, a trouble to go idle, then, we can use the adorner with parameters to decorate it, which he is like a switch, when it is called, It is removed when not in use. Give a parameter to the adorner, then the grammatical sugar should also be enclosed in parentheses. The parentheses in the syntactic sugar incoming the argument. Here, we can use three layers of nesting, get a logo to go to identify.

#Adorner with parameters: (equivalent to a switch) in order to pass a parameter to the adorner#when f=true# is True, the decorator is added.F=false#when False, the decorator is removed.defouter (flag):defWrapper (func):defInner (*args,**Kwargs):ifflag:Print('before') ret=func (*args,**Kwargs)Print(' After')            Else: Ret= Func (*args, * *Kwargs)returnretreturnInnerreturnWrapper@outer (F)#@wrapperdefhahaha ():Print('hahaha') @outer (F)defShuangwaiwai ():Print('Shuangwaiwai') hahaha () Shuangwaiwai ()

adding parameters to the adorner

Five or more adorners decorate a function

defqqqxing (fun):defInner (*args,**Kwargs):Print('In Qqxing:before') ret= Fun (*args,**Kwargs)Print('In qqxing:after')        returnretreturnInnerdefPipixia (fun):defInner (*args,**Kwargs):Print('In Qqxing:before') ret= Fun (*args,**Kwargs)Print('In qqxing:after')        returnretreturnInner@qqqxing@pipixiadefDapangxie ():Print('are you hungry?') Dapangxie ()" "execution order of the @qqqxing and @pipixia: First execute the print (' in Qqxing:before ') inside the qqqxing and then jump to the print (' in Qqxing:before ') inside the Pipixia ret = Fun (*args,**kwargs) print (' in Qqxing:after '), finished and returned to the qqqxing inside the print (' in Qqxing:after '). So just like the results of the following Operation" "

multiple adorners decorate a function

VI. statistics How many functions have been decorated for small applications

count How many functions I've decorated l=[]defWrapper (Fun): L.append (Fun)#statistics the number of functions in the current program is decorated    defInner (*args,**Kwargs):#l.append (fun) #统计本次程序执行有多少个带装饰器的函数被调用了ret = Fun (*args,**Kwargs)returnretreturnInner@wrapperdefF1 ():Print('In F1') @wrapperdefF2 ():Print('In F2') @wrapperdeff3 ():Print('In F3')Print(l)

statistics How many functions are decorated

python--Decorator