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

So let's take a look at a simple decorator: the ability to calculate the execution time of each function

1 Import Time2 defWrapper (func):3         definner ():4start=time.time ()5 func ()6End=time.time ()7               Print(end-start)8         returnInner9     Ten defhahaha (): OneTime.sleep (1) A         Print('AAAAA') -Hahaha=Wrapper (hahaha) -Hahaha ()

a simple decorator

The above function is somewhat not brief, imperfect, the following introduced the grammar sugar.

1 Import Time2 defWrapper (func):3         definner ():4start=time.time ()5 func ()6End=time.time ()7                Print(end-start)8         returnInner9 @wrapperTen defKKK ():#equivalent to Kkk=wrapper (KKK) One     Print('AAAAA') AKKK ()

decorator-------Grammar sugar

The above adorner is a function without parameters, now decorate a parameter with what to do?

1 Import Time2 defTimmer (func):3     defInner (a):4start=time.time ()5 func (a)6End=time.time ()7         Print(end-start)8     returnInner9 Ten @timmer One defhahaha (a): ATime.sleep (1) -     Print(a) -  the  -Hahaha (5)

adorner with one parameter

1 Import Time2 defTimer (func):3     defInner (*args,**Kwargs):4Start =time.time ()5Re = func (*args,**Kwargs)6End=time.time ()7         Print(end-start)8         returnRe9     returnInnerTen  One@timer#==> func1 = Timer (func1) A defFunc1 (A, b): -     Print('In func1') -     Print(A, b) the  -@timer#==> func1 = Timer (func1) - defFunc2 (a): -     Print('In Func2 and get a:%s'%(a)) +     return 'fun2 over' -  +Func1 () A Print(Func2 ('aaaaaa'))

the original function adorner with multiple parameters

1 Import Time2 defTimer (func):3     defInner (*args,**Kwargs):4Start =time.time ()5Re = func (*args,**Kwargs)6End=time.time ()7         Print(End-start)8         returnRe9     returnInnerTen  One@timer#==> func1 = Timer (func1) A defJJJ (a): -     Print('In jjj and get a:%s'%(a)) -     return 'fun2 over' the  -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

1 Import Time2 defWrapper (func):#Decorative Device3     defInner (*args, * *Kwargs):4         " "content extension prior to function execution" "5ret = func (*args, * *Kwargs)6          " "content extension prior to function execution" "7         returnret8     returnInner9 Ten@wrapper#=====>aaa=timmer (AAA) One defaaa (): ATime.sleep (1) -     Print('FDFGDG') -AAA ()

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Python-------Decorator