[Articles] function decorator

Decorator role:

　　You do not want to modify the function is called, add functionality before and after the function

The simplest decorator:

DEF warpper (F):
     DEF inner ():
         Pass 
        F ()     # execution is decorated function 
        Pass 
    return inner   # returns the inner address to to FUNC 

@wrapper    # syntactic sugar @ equal FUNC = warpper (FANC) 
DEF FUNC ():   # decorated function 
    Pass 
# FUNC = warpper (FANC) 
FUNC ()         # perform the function of inner
       

 

 

The order of execution:

 

 When the decorated function returns a value, due to the implementation of that inner, it is necessary to get the decorated function return value of a function in the inner lining, and back out through the inner:

DEF warpper (F):
     DEF Inner ():
         Pass 
        RET = F ()   # receiving the return value of the function to be decorated 
        Pass 
        return RET # returns the return value of the received 
    return Inner 

@wrapper 
DEF func ():
     return None # Return value 
func ( )

 

 

When the decorative function at the same time the need for traditional values, and then only can be received in the inner function, upon receiving the called function also need to be decorated in vivo function, * args and ** kwargs used simultaneously, you may receive parameter types :

def wrapper(f):
    def inner(*args,**kwargs):
        pass
        ret = f(*args,**kwargs)
        pass
        return ret
    return inner

@wrapper
def func(a,b,c,d = 1):
    return None
func(1,2,3,4)

 

So, this is a complete decorator, namely fixed pattern decorator

 

Note:

Syntactic sugar:

　　Expression: @ decorator function

For example in the code above @wrapper, equivalent to func = wrapper (func) This code