[Tutor] How to replace instances

[Richard Lovely]

Hi, I'm not going to guess at why this doesn't work, but I've got a
potential solution for you:

class Z(object):
    def __init__(self,y):
        self.y = y
    def replaceZ (self,withWhat):
        self.__dict__ = withWhat.__dict__

Is there a reason you can't use a simple assignment (x=y) outside of the class?

On 9/25/08, tutor-request at python.org <tutor-request at python.org> wrote:
> Date: Thu, 25 Sep 2008 04:24:31 -0400
> From: "Steve Collins" <emperor.ghaz at gmail.com>
> Subject: [Tutor] How to replace instances
> To: tutor at python.org
> Message-ID:
>        <63e3a6e10809250124x3307122erb524bb2e2f303342 at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> I've written a save/load function for a simple program using cPickle. Upon
> saving, a master list, to which all instances are added in their __init__,
> is pickled. when the program starts, if the user wishes to load, a variable
> "load" is set to one, and the pickled list is loaded. All the classes either
> A) initialize using the arguments provided or B) using the the attributes of
> the instances in the un-pickled list. This seems a little clunky to me, but
> it basically works.
> However, some of the instances refer explicitly to other instances
> instances. It's obvious why this causes problems. It occurred to me to
> simply replace the instances with the ones in the un-pickled list, but I
> don't know how.
>
> I tried using the following approach:
>
> class Z:
>    def __init__(self,y):
>        self.y = y
>    def replaceZ (self,withWhat):
>        self = withWhat
>
>
> That doesn't raise any errors, but it also doesn't work:
>
> >>> a = X(10)
> >>> b = X(20)
> >>> print a.y
> 10
> >>> print b.y
> 20
> >>> b.replaceZ(a)
> >>> print b.y
> 20
> >>> a
> <__main__.X instance at 0x00D4AE18>
> >>> b
> <__main__.X instance at 0x00D54328>
> >>>
>
> Can anyone tell me how to achieve this?
> -------------- next part --------------
> An HTML attachment was scrubbed...
> URL: <http://mail.python.org/pipermail/tutor/attachments/20080925/bb74e9f7/attachment-0001.htm>
>

-- 
Richard "Roadie Rich" Lovely, part of the JNP|UK Famile
www.theJNP.com