Scope troubles with a swap function

[Hans Nowak]

>===== Original Message From "Matthew D. Wood" <woodm at equire.com> =====
>Ok, I've been banging my head against this for a sufficiently long time
>that I feel justified in presenting this personal challenge to the list.
>
>How do you make a swap function?

You don't need to. :)  Use:

  a, b = b, a

>How do you make a function or a callable object instance that will do
>what the following code intends to do:
>
>   def swap (heaven, hell) :
>           purgatory = heaven
>           heaven = hell
>           hell = purgatory

Python's internal workings are very different from languages like C and 
Pascal. A Python "variable" is not a location in memory that you can fill with 
arbitrary data. This Pascal code:

  X := 3;
  X := 42;

changes the value of X, which resides at a certain location in memory. But the 
equivalent Python code

  x = 3
  x = 42

does not do exactly the same; rather, it binds the name 'x' to the value 3, 
then rebinds that name to the value 42. Other people explain this better than 
me; see

  http://w1.132.telia.com/~u13212494/guides/python-objects.htm

HTH,

--Hans Nowak