Question

我想创建一个能够在访问时用任意对象替换自身的对象;如下所示：

class stand_in_object(object):
    def __init__(self,obj_ref):
        self.obj_ref

    def __getattr__(self,key):
        pass
        #somehow make calling reference now refer to self.obj_ref
        #Consider: setattr(ref,name,self.obj_ref) - how do I get ref,name?
        #Or perhaps something that replaces the object located at "location"
        #so that all references id(self) are "pointing" to
        #a new object. Maybe ctypes.memmove?

#------------------------Example use----------------------
class x(object):
    def __init__(self):
        self.y=stand_in_object(int(5))

a=x()
print a.x.f #calls a.x.__getattr__('f') which sets a.x = int(5)

我以为我可以尝试memmove，或者替换所有引用方法，发现这篇文章：https://benkurtovic.com/2015/01/28/python-object-replacement.html

我正在尝试使用cPickle制作OODB。我希望有一些尚未加载的持久对象，在访问它们之前由一个替代对象引用。如下所示：

loaded = {}
class stand_in(object):
    def __init__(self,id,src): 
        self.id,self.src = id,src
    def __getattr__(self,key):
        loaded[self.id] = cust_unpickle(self.src)
    #Some function to replace reference of standin_obj with loaded object

def persistent_load(id):
    if id in loaded: return loaded[id]
    else: return stand_in(id,src)

#--------------------------Example-------------------------------
#consider database stores objects a and c, and a.c = c.
a = unpickle(a.id,src) #loaded = {a.id:a}, a.c = stand_in(c.id,c.src)
print a.c.x  #calls a.c.__gettattr__ which has the effect:
             #c = unpickle(c.id,src)
             #and loads = {a.id:a,c.id:c}

自我替换对象python

0 个答案: