Python装饰器进阶-白红宇

Python装饰器进阶

阅读量：7153 次

发布时间：2019-06-29

本文共 3547 字，大约阅读时间需要 11 分钟。

对带参数的函数进行装饰

'''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 + b myfunc(1, 2)myfunc(3, 4)

对参数数量不确定的函数进行装饰

'''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+c myfunc(1, 2)myfunc(3, 4)myfunc2(1, 2, 3)myfunc2(3, 4, 5)

让装饰器带参数

'''让装饰器带参数，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()

让装饰器带类参数

'''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()

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 _deco

'''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''' 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))