Learn Python decorators in Step 9 and python Decoration in Step 9

Learn Python decorators in Step 9 and python Decoration in Step 9

This example describes the Python decorator. Share it with you for your reference. The specific analysis is as follows:

This is the content introduced in the Python Learning Group. It is a good way to learn and practice more.
Step 1: Prepare the simplest function and add additional functions.

#-*-Coding: gbk-*-''' Example 1: The simplest function, indicating that two '''def myfunc (): print ("myfunc () called. ") myfunc ()

Step 2: Use the decoration function to add additional functions before and after function execution

#-*-Coding: gbk-*-''' Example 2: The parameter used to replace the function (decoration) decoration function is the decorated function object. The actual statement of the decoration of the original function object is returned: myfunc = deco (myfunc) ''' def deco (func): print ("before myfunc () called. ") func () print (" after myfunc () called. ") return funcdef myfunc (): print (" myfunc () called. ") myfunc = deco (myfunc) myfunc ()

Step 3: Use the syntax sugar @ to describe the function

#-*-Coding: gbk-*-''' Example 3: Use the syntax sugar @ to decorate the function, which is equivalent to "myfunc = deco (myfunc) but we found that the new function was called only for the first time, and the original function called '''def deco (func): print ("before myfunc () called. ") func () print (" after myfunc () called. ") return func @ decodef myfunc (): print (" myfunc () called. ") myfunc ()

Step 4: Use nested packaging functions to ensure that each new function is called

#-*-Coding: gbk-*-''' Example 4: Use nested function packaging to ensure that each new function is called. The parameters and return values of nested function packaging are the same as those of the original function, the decoration function returns the nested packaging function object '''def deco (func): def _ deco (): print ("before myfunc () called. ") func () print (" after myfunc () called. ") # You do not need to return func. Actually, you should return the return value of the original function: return _ deco @ decodef myfunc (): print (" myfunc () called. ") return 'OK' myfunc ()

Step 5: Describe the functions with Parameters

#-*-Coding: gbk-*-''' Example 5: Describe the function with parameters. The parameters and return values of the nested function are the same as those of the original function, the decoration function returns the nested packaging function object '''def deco (func): def _ deco (a, B): print ("before myfunc () called. ") ret = func (a, B) print (" after myfunc () called. result: % s "% ret) return ret return _ deco @ decodef myfunc (a, B): print (" myfunc (% s, % s) called. "% (a, B) return a + bmyfunc (1, 2) myfunc (3, 4)

Step 6: Describe functions with uncertain number of parameters

#-*-Coding: gbk-*-''' Example 6: decorate a function with an uncertain number of parameters. Use the parameter (* args, ** kwargs ), automatically adapt to variable parameters and named parameters ''' def deco (func): def _ deco (* args, ** kwargs): print ("before % s called. "% func. _ name _) ret = func (* args, ** kwargs) print ("after % s called. result: % s "% (func. _ name __, ret) return ret return _ deco @ decodef myfunc (a, B): print ("myfunc (% s, % s) called. "% (a, B) return a + B @ decodef myfunc2 (a, B, c): print (" myfunc2 (% s, % s, % s) called. "% (a, B, c) return a + B + cmyfunc (1, 2) myfunc (3, 4) myfunc2 (1, 2, 3) myfunc2 (3, 4, 5)

Step 7: Bring parameters to the decorator

#-*-Coding: gbk-*-''' Example 7: On the basis of example 4, let the ornament carry parameters. Compared with the previous example, there is an additional layer of packaging in the outer layer. The decoration function name should actually be more meaningful ''' def deco (arg): def _ deco (func): def _ deco (): print ("before % s called [% s]. "% (func. _ name __, arg) func () print ("after % s called [% s]. "% (func. _ name __, arg) return _ deco @ deco ("mymodule") def myfunc (): print ("myfunc () called. ") @ deco (" module2 ") def myfunc2 (): print (" myfunc2 () called. ") myfunc () myfunc2 ()

Step 8: Let the ornament carry Class Parameters

#-*-Coding: gbk-*-''' Example 8: The modifier has the class parameter '''class locker: def _ init _ (self ): print ("locker. _ init _ () shoshould be not called. ") @ staticmethod def acquire (): print (" locker. acquire () called. (This is a static method) ") @ staticmethod def release (): print (" locker. release () called. (object instance not required) ") def deco (cls): ''' cls must implement the acquire and release static method ''' def _ deco (func ): def _ deco (): print ("before % s called [% s]. "% (func. _ name __, cls) cls. acquire () try: return func () finally: cls. release () return _ deco @ deco (locker) def myfunc (): print ("myfunc () called. ") myfunc ()

Step 9: decorator includes class parameters and splits public classes into other py files. It also demonstrates how to apply multiple decorator to a function.

#-*-Coding: gbk-*-''' mylocker. py: public class for example 9. py '''class mylocker: def _ init _ (self): print ("mylocker. _ init _ () called. ") @ staticmethod def acquire (): print (" mylocker. acquire () called. ") @ staticmethod def unlock (): print (" mylocker. unlock () called. ") class lockerex (mylocker): @ staticmethod def acquire (): print (" lockerex. acquire () called. ") @ staticmethod def unlock (): print (" lockerex. unlock () called. ") def lockhelper (cls): ''' cls must implement the acquire and release static methods ''' def _ deco (func): def _ deco (* args, ** kwargs): print ("before % s called. "% func. _ name _) cls. acquire () try: return func (* args, ** kwargs) finally: cls. unlock () return _ deco

#-*-Coding: gbk-*-''' Example 9: The decorator has class parameters, the splitting of public classes to other py files also demonstrates how to apply multiple decorators to a function ''' from mylocker import * class example: @ lockhelper (mylocker) def myfunc (self): print ("myfunc () called. ") @ lockhelper (mylocker) @ lockhelper (lockerex) def myfunc2 (self, a, B): print (" myfunc2 () called. ") return a + bif _ name __= =" _ main _ ": a = example (). myfunc () print (. myfunc () print (. myfunc2 (1, 2) print (. myfunc2 (3, 4 ))

I hope this article will help you with Python programming.