Python装饰器演示

本文是对上文转载文章的代码实现，尽管文章讲解的很详细了，但还是要实现以下滴。

# 第一步，最简单的函数，准备附加额外功能# 示例1: 最简单的函数,表示调用了两次def myfunc():    print("myfun() called")myfun()myfun()# 第二步，使用装饰函数在函数执行前和执行后分别附加额外功能# 示例2: 替换函数(装饰)装饰函数的参数是被装饰的函数对象，返回原函数对象# 装饰的实质语句: myfunc = deco(myfunc)def deco(func):    print('before myfunc() called')    func()    print('after myfunc() called')    return funcmyfunc = deco(myfunc)myfunc()myfunc()# before myfunc() called# myfun() called# after myfunc() called# myfun() called# myfun() called# 第三步：使用语法糖@来装饰函数# 示例3: 使用语法糖@来装饰函数，相当于“myfunc = deco(myfunc)”# 但发现新函数只在第一次被调用，且原函数多调用了一次@decodef myfunc():    print("myfun() called")myfunc()myfunc()# before myfunc() called# myfun() called# after myfunc() called# myfun() called# myfun() called# 第四步：使用内嵌包装函数来确保每次新函数都被调用# 示例4: 使用内嵌包装函数来确保每次新函数都被调用，内嵌包装函数的形参# 和返回值与原函数相同，装饰函数返回内嵌包装函数对象def deco(func):    def _deco():        print("before myfunc() called.")        func()        print("  after myfunc() called.")        # 不需要返回func，实际上应返回原函数的返回值    return _deco@decodef myfunc():    print(" myfunc() called.")    return 'ok'myfunc()myfunc()# before myfunc() called.#  myfunc() called.#   after myfunc() called.# before myfunc() called.#  myfunc() called.#   after myfunc() called.# 第五步：对带参数的函数进行装饰# 示例5: 对带参数的函数进行装饰，内嵌包装函数的形参和返回值与原# 函数相同，装饰函数返回内嵌包装函数对象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)# before myfunc() called.#  myfunc(1,2) called.#   after myfunc() called. result: 3# before myfunc() called.#  myfunc(3,4) called.#   after myfunc() called. result: 7# 第六步：对参数数量不确定的函数进行装饰# 示例6: 对参数数量不确定的函数进行装饰，参数用(*args, **kwargs)，自动适应变参和命名参数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)# before myfunc called.#  myfunc(1,2) called.#   after myfunc called. result: 3# before myfunc called.#  myfunc(3,4) called.#   after myfunc called. result: 7# before myfunc2 called.#  myfunc2(1,2,3) called.#   after myfunc2 called. result: 6# before myfunc2 called.#  myfunc2(3,4,5) called.#   after myfunc2 called. result: 12# 第七步：让装饰器带参数# 示例7: 在示例4的基础上，让装饰器带参数，和上一示例相比在外层多了一层包装。# 装饰函数名实际上应更有意义些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    return _deco@deco("mymodule")def myfunc():    print(" myfunc() called.")@deco("module2")def myfunc2():    print(" myfunc2() called.")myfunc()myfunc2()# before myfunc called [mymodule].#  myfunc() called.#   after myfunc called [mymodule].# before myfunc2 called [module2].#  myfunc2() called.#   after myfunc2 called [module2].# 第八步：让装饰器带类参数# 示例8: 装饰器带类参数class locker:    def __init__(self):        print("locker.__init__() should be not called.")    @staticmethod    def acquire():        print("locker.acquire() called.（这是静态方法）")    @staticmethod    def release():        print("  locker.release() called.（不需要对象实例）")def deco(cls):    '''cls 必须实现acquire和release静态方法'''    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()# before myfunc called [<class '__main__.locker'>].# locker.acquire() called.（这是静态方法）#  myfunc() called.#   locker.release() called.（不需要对象实例）# before myfunc called [<class '__main__.locker'>].# locker.acquire() called.（这是静态方法）#  myfunc() called.#   locker.release() called.（不需要对象实例）# 第九步：装饰器带类参数，并分拆公共类到其他py文件中，同时演示了对一个函数应用多个装饰器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 必须实现acquire和release静态方法'''    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 _decoclass 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()    a.myfunc()    print(a.myfunc())    print(a.myfunc2(1, 2))    print(a.myfunc2(3, 4))# before myfunc called.# mylocker.acquire() called.#  myfunc() called.#   mylocker.unlock() called.# before myfunc called.# mylocker.acquire() called.#  myfunc() called.#   mylocker.unlock() called.# None# before __deco called.# mylocker.acquire() called.# before myfunc2 called.# lockerex.acquire() called.#  myfunc2() called.#   lockerex.unlock() called.#   mylocker.unlock() called.# 3# before __deco called.# mylocker.acquire() called.# before myfunc2 called.# lockerex.acquire() called.#  myfunc2() called.#   lockerex.unlock() called.#   mylocker.unlock() called.# 7