[Baypiggies] Fwd: nested list help

[Aahz]

On Tue, Jul 27, 2010, Robert Zuber wrote:
>
> I too find myself wishing that list methods returned a reference
> to the list so that I could chain those calls or use them in list
> comprehensions.  Look forward to anyone's input on why they don't.

It's a signal.  Here's a fake example for why they don't:

>>> a = [2, 7, 3, 0]
>>> b = a.sort()
>>> a
[0, 2, 3, 7]   # WTF?!?!?!?!

IOW, it's too easy to forget about shared references, so mutating methods
return None.  However, Python does provide (at least in this case) a
simple solution:

>>> a = [2, 7, 3, 0]
>>> b = sorted(a)
>>> a
[2, 7, 3, 0]
>>> b
[0, 2, 3, 7]

See also

http://docs.python.org/faq/design.html#why-doesn-t-list-sort-return-the-sorted-list
-- 
Aahz (aahz at pythoncraft.com)           <*>         http://www.pythoncraft.com/

"....Normal is what cuts off your sixth finger and your tail..."  --Siobhan