python basis XXIII: decorator

Decorator

Decorator: essentially a function, a function to add functionality without changing the original function code

Decorator is actually a closure function

Commonly used in: rights verification, user login register

Decorator Category: General decorator

　　　　　　With a decorative function parameters (fixed length, variable length)

　　　　　　With a decorative function returns a value of

　　　　　　Decorator with parameters (different functions of different effects)

　　　　　　The class as a decorator (hereinafter speaking)

　　　　　　Decorative (talk back)

Common decorator Method 1

def xdl (func): # decorator 
    def inner (): # is the next function after a decorative 
        print ( 'school punch') 
        FUNC () #func original function, the function is bj_work, sh_work function 
        print ( 'school punch') 
    Inner return 
# Beijing's punch function (original function) 
DEF bj_work (): 
    Print ( 'Beijing beginning of a day of learning') 
bj_work = XDL (bj_work) #bi_work function == inner function 
bj_work ()

# Shanghai's punches 
DEF sh_work (): 
    Print ( 'Shanghai day began learning') 
sh_work = XDL (sh_work) 
sh_work ()

Outputs:

Punch school
begin learning Beijing day
after school punch
school punch
to start in Shanghai a day of learning
after school punch

Common methods decorator 2
 @ Syntax: @ system will automatically add the following parameters are passed to the function as a decorator, from the lower to the
@ character is also known as syntactic sugar

def xdl (func): # decorator 
    def inner (): # is the next function after a decorative 
        print ( 'school punch') 
        FUNC () #func original function, the function is hz_work 
        print ( 'school punch') 
    return Inner

@xdl 
DEF hz_work (): 
    Print ( 'Hangzhou day start learning') 
hz_work () 
will output:

Punch school
start Hangzhou day learning
school punch

@ The system will automatically add the following parameters to function as a decorator, from bottom to top

DEF out_1 (FUNC): 
    DEF Inner (): 
        Print ( 'start clocking. 1') 
        FUNC () 
        Print ( 'school punch. 1') 
    return Inner 

DEF OUT_2 (FUNC): 
    DEF Inner (): 
        Print ( 'start punch 2' ) 
        FUNC () 
        Print ( 'school punch 2') 
    return Inner 
@ out_1 
@ OUT_2 
DEF xqgz (): 
    Print ( 'beginning of each study day cells') 
xqgz () 
will output:

Punch 1 Start
Start punch 2
beginning of each study day cell
school punch 2
school punch 1

Inner # decorator with parameters (fixed length) parameter () must be in the parameters () in the same func, it may not be the same with parameters () in sz_work
 DEF XDL (func):
    DEF Inner (n-, S ):
        Print ( 'school punch')
        FUNC (n-, S)
        Print ( 'school punch')
    return Inner
@xdl
DEF sz_work (name, Sex):
    Print ( 'learning start day Shenzhen')
sz_work ( 'Shenzhen', 'city')

will output:

Punch school
start learning Shenzhen day
after school punch

Decorator inner # with parameters (variable length) of () the parameters must be parameter () in the same func, can not with parameters () in sz_work as
 DEF XDL (func):
    DEF Inner (* A, K **):
        Print ( 'school punch')
        FUNC (A *, ** K)
        Print ( 'school punch')
    return Inner
@xdl
DEF sz_work (Arge *, ** kwargs):
    Print (Arge, kwargs, ' Shenzhen day began learning ')
sz_work (' Shenzhen ',' city ', waihao =' Windows of the World ')
will output:

School punch
( 'Shenzhen', 'City') { 'waihao': 'Window of the World'} Shenzhen day start learning
after school punch

 

# Decorator with a return value
 DEF XDL (FUNC):
    DEF Inner ():
        Print ( 'start punch')
        zhuangtai = FUNC ()
        Print ( 'school punch')
        return zhuangtai
    return Inner

@xdl
DEF Work ():
    Print ( 'start work')
    return 'work ending'
RES = work ()
Print (RES)
will output:

Punch began
to work
after school punch
end of the work

Decorator with parameters (different functions have different effects)

def wai_out (city): # is just a shell 
    def out (func): # real decorator 
        DEF Inner (): 
            IF City == 'Shanghai': 
                Print ( 'start clocking') 
                FUNC () 
                Print ( 'school punch ') 
            elif City ==' Beijing ': 
                Print (' Beijing not in class ') 
        return Inner 
    return OUT 
@wai_out (' Shanghai ') 
DEF sh_work (): 
    Print (' Shanghai began a day of learning ') 
sh_work () 
Print (' =============== ') 
@wai_out (' Beijing ') 
DEF bj_work (): 
    Print (' Beijing began a day of learning ') 
bj_work ()