assignment statements: lists vs. strings

[Dan Bishop]

klaus_neuner82 at yahoo.de (Klaus Neuner) wrote in message news:<3e96ebd7.0402020750.3b0b9b82 at posting.google.com>...
> Hello,
> 
> I would like to understand the reason for the following difference
> between dealing with lists and dealing with strings: What is this
> difference good for? How it is accounted for in Python slang?
> 
> Klaus
> 
> >>> string1 = "bla"
> >>> string2 = string1
> >>> string1 = string1 + "bla"
> >>> string1
>  'blabla'
> >>> string2
>  'bla'
> >>> 
>  
> >>> list1 = [1,2]
> >>> list2 = list1
> >>> list1.append(1)

This is *not* equivalent to the string code.  Notice that

  >>> list1 = list1 + [1]
  >>> list1
   [1, 2, 1]
  >>> list2
   [1, 2]

*does* behave like your string example.

> >>> list1
>  [1, 2, 1]
> >>> list2
>  [1, 2, 1]

Unlike string1, the name "list1" hasn't been rebound since the
assignment "list2 = list1", and therefore they still refer to the same
object.