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[Python-Dev] a feature i'd like to see in python #1: betteriteration control

Raymond Hettinger python at rcn.com
Tue Dec 5 18:30:46 CET 2006 
[Ben Wing ]
>> many times writing somewhat complex loops over lists i've found the need
>> to sometimes delete an item from the list.  currently there's no easy
>> way to do so; basically, you have to write something like

[Adam Olsen]
> As I don't believe there's any need for a language extension, I've
> posted my approach to this on comp.lang.python:
>
> http://groups.google.com/group/comp.lang.python/browse_thread/thread/724aa6bcf021cfad/c4c629bd1bacc12b#c4c629bd1bacc12b
>
> Note that deleting from the list as you iterate over it tends to have
> very poor performance for larger lists.  My post includes some
> timings, demonstrating this.


Well said.  And even if performance considerations could be addressed, it would 
be a crummy idea , leading people into knotty code.  When looping over a 
structure, the act of actively inserting and deleting entries, can introduce 
unexpected feedback between loop control and the loop body.  This is a recipe 
for bugs and hard-to-maintain code.

Overall, feature #1 is a non-starter and hopefully this thread will die quickly 
or move off-list.


Raymond
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