Python 装饰器 : how to use parent class decorators in a child class

Question

这个问题在这里已经有了答案:





Accessing a decorator in a parent class from the child in Python

(2 个回答)


6年前关闭。




备注 :

另一个问题的已接受答案显示了如何使用父装饰器。

这个问题的公认答案显示将装饰器移动到模块范围。

编辑:使用前面的例子是个坏主意。希望这更清楚:

class A:
    def deco( func ):
        print repr(func)
        def wrapper( self, *args ):
            val = func( *args )
            self.do_something()
            return val
        return wrapper

    def do_something( self ):
        # Do something
        print 'A: Doing something generic for decoration'

    @deco
    def do_some_A_thing ( self ):
        # Do something 
        print 'A: Doing something generic'

class B ( A ):

    @deco
    def do_some_B_thing( self ):
        # Do something
        print "B: Doing something specific"

a = A()
b = B()
a.do_some_A_thing()
b.do_some_B_thing()

#Expected Output:
    #A: Doing something generic
    #A: Doing something generic for decoration
    #B: Doing something specific
    #A: Doing something generic for decoration

此代码生成 NameError: name 'deco' is not defined inside B.
装饰器需要在类范围内，因为我需要访问存储的状态。

第三次编辑:根据斯文的建议，我尝试了这个:

class A:
    def deco( func ):
        def wrapper( self, *args ):
            val = func( *args )
            self.do_something(*args)
            return val
        return wrapper

    def do_something( self ):
        # Do something
        print 'A: Doing something generic for decoration'

    @deco
    def do_some_A_thing ( self ):
        # Do something 
        print 'A: Doing something generic'

    deco = staticmethod(deco)

class B ( A ):

    @A.deco
    def do_some_B_thing( self ):
        # Do something
        print "B: Doing something specific"



a = A()
b = B()
a.do_some_A_thing()
b.do_some_B_thing()

#Expected Output:
    #A: Doing something generic
    #A: Doing something generic for decoration
    #B: Doing something specific
    #A: Doing something generic for decoration

我现在有 TypeError: do_some_A_thing() 只需要 1 个参数(给定 0)。任何指针？

Answer 1

问题是继承适用于实例属性查找，而不适用于类定义。所以当你尝试在 B 中用 A.deco 进行装饰时，它找不到它。解决方法是移动deco超出模块范围，因为名称 self 没有任何魔力，您可以继续使用它。您还需要显式传递 self至func , 你会做 不是 需要传入self.do_something() .这是更新的代码:

def deco( func ):
    print repr( func )
    def wrapper( self, *args ):
        val = func( self, *args )
        self.do_something()
        return val
    return wrapper

class A:
    def do_something( self ):
        # Do something
        print 'A: Doing something generic for decoration'

    @deco
    def do_some_A_thing ( self ):
        # Do something 
        print 'A: Doing something generic'

class B ( A ):

    @deco
    def do_some_B_thing( self ):
        # Do something
        print "B: Doing something specific"

a = A()
b = B()
a.do_some_A_thing()
b.do_some_B_thing()