packing unpacking depends on order.

[Antoon Pardon]

>>> a = [1, 2, 3, 4, 5]
>>> b = 1
>>> b, a[b] = a[b], b
>>> a
[1, 2, 1, 4, 5]
>>> a = [1, 2, 3, 4, 5]
>>> b = 1
>>> a[b], b = b, a[b]
>>> a
[1, 1, 3, 4, 5]

I think I understand how it gets these results
but I'm not really happy with them. I think python
should give the second result in both cases.

-- 
Antoon Pardon