When convert two sets with the same elements to lists, are the lists always going to be the same?

[Terry Reedy]

On 5/3/2012 8:36 PM, Peng Yu wrote:
> Hi,
>
> list(a_set)
>
> When convert two sets with the same elements to two lists, are the
> lists always going to be the same (i.e., the elements in each list are
> ordered the same)? Is it documented anywhere?

"A set object is an unordered collection of distinct hashable objects".
If you create a set from unequal objects with equal hashes, the 
iteration order may (should, will) depend on the insertion order as the 
first object added with a colliding hash will be at its 'natural 
position in the hash table while succeeding objects will be elsewhere.

Python 3.3.0a3 (default, May  1 2012, 16:46:00)
 >>> hash('a')
-292766495615408879
 >>> hash(-292766495615408879)
-292766495615408879
 >>> a = {'a', -292766495615408879}
 >>> b = {-292766495615408879, 'a'}
 >>> list(a)
[-292766495615408879, 'a']
 >>> list(b)
['a', -292766495615408879]

-- 
Terry Jan Reedy