[Tutor] How to replace instances

[Steve Collins]

On 9/25/08, Kent Johnson <kent37 at tds.net> wrote:
> On Thu, Sep 25, 2008 at 4:24 AM, Steve Collins <emperor.ghaz at gmail.com>
> wrote:
>
>> 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
>
> 'self' is just another parameter passed to the method, so this just
> rebinds a local name.
>

That makes sense. At least I understand why it doesn't work now.

> This example doesn't seem to illustrate the situation you describe.
> You can replace the 'y' attribute of a Z object by assigning to it.
>
> One solution might be to make all your objects pickleable. Pickle
> tracks object references and handles embedded references correctly.
>
>> That doesn't raise any errors, but it also doesn't work:
>>
>>>>> a = X(10)
>>>>> b = X(20)
>
> Presumably this should be Z(10), Z(20) ?
>>>>> print a.y
>> 10
>>>>> print b.y
>> 20
>>>>> b.replaceZ(a)
>>>>> print b.y
>> 20
>
> If you want 'b' to refer to the same thing as 'a', just assign
> b = a

that's what I was trying (incorrectly) to achieve the above example.
but how can I do this for an arbitrary number of objects in a list?

I have a list x = [a,b,c] and a list y = [d,e,f], both filled with
instance objects. I want the instance at x[n] to reference the
instance at y[n]

n = 0
while n < range(len(x))
x[n] = y[n]
n+=1

given the contents of your link, I understand why x == [d,e,f] and not
a == d etc., but how can I make a == d by iterating through two lists?

>
> I think you have some common misconceptions about the nature of
> variables and assignment in Python. This may help:
> http://personalpages.tds.net/~kent37/kk/00012.html
>
> Kent
>
I should note that I am very much a novice programmer, and really
appreciate the feedback.

Thanks,
Steve