Overview: python decorator belong to advanced will learn, a lot of people just learning it is difficult to understand, this is easier to understand with a simple way to talk about :( Note: This function requires basic knowledge of)
first step:
We have a function, such as a sum of functions:
def sum_test(): sum=12+20 print(sum)
If we need to re-start function before and after printing with the added end for debugging, conventional approaches may be treated to modify this function, as follows:
sum_test DEF ():
Print ( "Start calculation ----- -----")
SUM = 12 is + 20 is
Print (SUM)
Print ( "Calculation ----- ----- End")
Before and after the input print () to process
Step two:
If I have more functions need to debug it, you have to modify the original packaged function? One by one to join print, then will be very slow, is there a better way? Yes, you can then define a debugging function, and then go to the function to call is debugging function, as follows:
sum_test DEF ():
SUM = 12 is + 20 is
Print (SUM)
DEF pr_test (FUNC):
Print ( "Start calculation ----- -----")
FUNC ()
Print ( "End Calculation ----- ----- ")
IF the __name__ == '__main__':
pr_test (sum_test)
The above method pr_test () calls the function sum (), can be modified to avoid duplication, but we pr_test () each pass parameters to give, and this is an easy living, ah, this time to debut a decorator , first came to pr_test () packaged as a decorator:
pr_test DEF (FUNC):
DEF out_test ():
Print ( "----- counted -----")
FUNC ()
Print ( "----- end computing -----")
return out_test
sum_test DEF ():
SUM = 16 + 12 is
Print (SUM)
IF the __name__ == '__main__':
RES = pr_test (sum_test)
RES ()
Such a simple decorator to do the work, we just need to call before sum_test defined later sum_test, plus res = pr_test (sum_test), you can achieve the purpose of timing;
This is the concept of decorators, looks like sum_test is pr_test decorated (there is no function has been renovated feeling that I was a stucco walls, stucco strong ability ah)!
Our Python provides a syntactic sugar to reduce the amount of input characters. Is @pr_test, used as follows:
pr_test DEF (FUNC):
DEF out_test ():
Print ( "----- counted -----")
FUNC ()
Print ( "----- end computing -----")
return out_test
@pr_test
DEF sum_test ():
SUM = 16 + 12 is
Print (SUM)
IF the __name__ == '__main__':
sum_test ()
By @pr_test, we completed a decorator function, after any necessary function, you need to add debugging code (can be any public function), then we add this @func in front (corresponding to the function name) on it , they have not grasped the concept of what python decorator?
Substantial hair is sent to