packing unpacking depends on order.

Sven R. Kunze srkunze at mail.de
Wed Sep 2 22:14:27 CEST 2015


On 02.09.2015 19:42, Terry Reedy wrote:
> On 9/2/2015 6:01 AM, Antoon Pardon wrote:
>>
>>>>> 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.
>
> I do not want the choice taken away from me.
>
I do as readability and maintainability comes first for me.

Btw. you would still be able to perform your choice but more explicitly.


However, I fear this would be a very hard break of backwards 
compatibility. :/

So, what I take away from this thread right now is that one should avoid 
this type of construction whenever possible as long as Python handles it 
that way.

Best,
Sven


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