copy.deepcopy(): is it bug or intended behavior?

Benjamin Han bhan at andrew.cmu.edu
Thu Aug 1 05:59:47 CEST 2002


Curiously if I added __deepcopy__ to class Bar (replace Bar with the following 
class def):

class Bar (list):
    def __deepcopy__ (self,memo):
        obj=Bar()
        memo[id(self)]=obj
        for e in self: obj.append(copy.deepcopy(e,memo))
            
        for k,v in self.__dict__.iteritems():
            obj.__dict__[k]=copy.deepcopy(v,memo)
            
        return obj


then the result is correct:

[[1]] 135743596
[[2]] 135787484
----------------------------------------------------------------------
[[1]] 135760188
[[2]] 135626380


Ben

On Wednesday 31 July 2002 07:59 pm, you wrote:
> This is an abstract of the actual code:
>
> --- cut here ---
> import copy
>
> class Foo:
>     def clone (self):
>         return copy.deepcopy(self)
>
> class Bar (list):
>     pass
>
> class Const:
>     def __init__ (self, data):
>         self.data=data
>     def __repr__ (self):
>         return str(self.data)
>
> n1=Foo()
> n1.t=[]
> c=Bar()
> c.append(Const('1'))
> n1.t.append(c)
>
> n2=Foo()
> n2.t=[]
> c=Bar()
> c.append(Const('2'))
> n2.t.append(c)
>
> g=Foo()
> g.hd=[]
> g.hd.append(n1)
> g.hd.append(n2)
>
> print g.hd[0].t,id(g.hd[0].t)
> print g.hd[1].t,id(g.hd[1].t)
>
> print
> '----------------------------------------------------------------------'
>
> h=g.clone()
>
> print h.hd[0].t,id(h.hd[0].t)
> print h.hd[1].t,id(h.hd[1].t)
>
> --- cut here ---
>
>
> Running on Python 2.2.1 gave the following output:
>
> [[1]] 135743596
> [[2]] 135759124
> ----------------------------------------------------------------------
> [[1]] 135505252
> [[1]] 135793916
>
>
> But the last line should have "[[2]]...". Am I missing something here?
>
> Thanks,
>
> Ben




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