[Tutor] creating pop method for stack class

[Martin Walsh]

Christopher Spears wrote:
> I see what you mean.  I have tested it, and I have gotten a weird result:
>>>> def shorten(lst):
> ...     lst = lst[:-1]
> ...
>>>> lista = [1,2,3,4]
>>>> shorten(lista)
>>>> print lista
> [1, 2, 3, 4]
>>>> lista = [1,2,3,4]
>>>> lista = lista[:-1]
>>>> print lista
> [1, 2, 3]
> 
> Strange...why does it work outside of the function but not in it?  Let me try something else:
> 
>>>> def shorten(lst):
> ...     lst = lst[:-1]

Perhaps it would be helpful to consider the following...

def shorten1(lst):
     lst[:] = lst[:-1]

... or ...

def shorten2(lst):
     lst.pop()

Why might these exhibit different behavior?

HTH,
Marty