python 裝飾器

1.在執行目標函數前附加一些內容或者功能：

def demo(func):
    print('before exec %s '%func.__name__)
    func()
    print('after exec %s '%func.__name__)
    return func
def func():
    print('hello world')

func = demo(func)
func()

2.使用語法糖@來裝飾函數

def demo(func):
    print('before exec %s '%func.__name__)
    func()
    print('after exec %s '%func.__name__)
    return func
@demo
def func():
    print('hello world')
func()

3.使用內嵌包裝飾函數保證每次新函數都被調用

def demo(func):
    def inner():
        print('before exec %s '%func.__name__)
        func()
        print('after exec %s '%func.__name__)
    return inner
@demo
def func():
    print('hello world')
func()

4.對帶參數的函數進行裝飾

def demo(func):
    def inner(a,b):
        print('before exec %s '%func.__name__)
        ret = func(a,b)
        print('after exec %s '%func.__name__)
        return ret
    return inner
@demo
def func(a,b):
    print('hello world')
    return a+b
print(func(1,2))

5.對參數數量不肯定的函數進行裝飾

def demo(func):
    def inner(*args,**kwargs):
        print('before exec %s '%func.__name__)
        ret = func(*args,**kwargs)
        print('after exec %s '%func.__name__)
        return ret
    return inner
@demo
def func(a,b):
    print('hello world func')
    return a+b
@demo
def func1(a,b,c):
    print('hello world func1')
    return a+b+c
print(func(1,2))
print(func1(1,2,3))

6.裝飾器帶參數

def demo(arg):
    def warper(func):
        def inner(*args,**kwargs):
            print('before exec %s %s'%(func.__name__,arg))
            ret = func(*args,**kwargs)
            print('after exec %s %s '%(func.__name__,arg))
            return ret
        return inner
    return warper
@demo('qq')
def func(a,b):
    print('hello world func')
    return a+b
@demo('wechat')
def func1(a,b,c):
    print('hello world func1')
    return a+b+c
print(func(1,2))
print(func1(1,2,3))

7.多個裝飾器裝飾一個函數

def wrapper1(func):
    def inner():
        print('wrapper1 ,before func')
        func()
        print('wrapper1 ,after func')
    return inner

def wrapper2(func):
    def inner():
        print('wrapper2 ,before func')
        func()
        print('wrapper2 ,after func')
    return inner

@wrapper2
@wrapper1
def f():
    print('in f')

f()

8.裝飾器帶類參數

'''''示例: 裝飾器帶類參數'''  
  
class locker:  
    def __init__(self):  
        print("locker.__init__() should be not called.")  
         
    @staticmethod  
    def acquire():  
        print("locker.acquire() called.（這是靜態方法）")  
         
    @staticmethod  
    def release():  
        print("  locker.release() called.（不須要對象實例）")  
  
def deco(cls):  
    '''''cls 必須實現acquire和release靜態方法'''  
    def _deco(func):  
        def __deco():  
            print("before %s called [%s]." % (func.__name__, cls))  
            cls.acquire()  
            try:  
                return func()  
            finally:  
                cls.release()  
        return __deco  
    return _deco  
 
@deco(locker)  
def myfunc():  
    print(" myfunc() called.")  
  
myfunc()  
myfunc()  

9.裝飾器帶類參數，並分拆公共類到其餘py文件中，同時演示了對一個函數應用多個裝飾器

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 必須實現acquire和release靜態方法'''  
    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  
    return _deco  

　　

'''''裝飾器帶類參數，並分拆公共類到其餘py文件中 
同時演示了對一個函數應用多個裝飾器'''  
  
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 + b  
  
if __name__=="__main__":  
    a = example()  
    a.myfunc()  
    print(a.myfunc())  
    print(a.myfunc2(1, 2))  
    print(a.myfunc2(3, 4))