python装饰器和方法

新来的.我也是(非常)新的python并试图了解以下行为.有人可以向我解释为什么这个例子中的两个方法有不同的输出？

def map_children(method):
    def wrapper(self,*args,**kwargs):
        res = method(self,*args,**kwargs)
        for child in self._children:
            method(child,*args,**kwargs)            
        return res
    return wrapper

class Node(object):

    def __init__(self,name,parent=None):
        self._namestring = name
        if parent:
            self._parent = parent

        self._children = []

    @map_children
    def decorated(self):
        if hasattr(self,'_parent'):
            print '%s (child of %s)'%(self._namestring,self._parent._namestring)
        else:
            print '%s'% self._namestring

    def undecorated(self):
        if hasattr(self,'_parent'):
            print '%s (child of %s)'%(self._namestring,self._parent._namestring)
        else:
            print '%s'% self._namestring

        for child in self._children:
            child.undecorated()


def runme():
    parent = Node('parent')

    child1 = Node('child1',parent)
    child2 = Node('child2',parent)
    grandchild = Node('grandchild',child1)
    child1._children.append(grandchild)
    parent._children.append(child1)
    parent._children.append(child2)

    print '**********result from decorator**********'
    parent.decorated()

    print '**********result by hand**********'
    parent.undecorated()

这是我系统上的输出:

In[]:testcase.runme()
**********result from decorator**********
parent
child1 (child of parent)
child2 (child of parent)
**********result by hand**********
parent
child1 (child of parent)
grandchild (child of child1)
child2 (child of parent)

那么为什么装饰的调用永远不会下降到孙子节点？我显然错过了一些关于语法的东西......

在装饰,你遍历节点的孩子和调用原始,非递归method他们

method(child, *args, **kwargs)

所以你只会深入一层.尝试用.替换该行

map_children(method)(child, *args, **kwargs)

并且您将获得与手动递归版本相同的输出.