[Python-3000] Spooky behavior of dict.items() and friends

[Mike Klaas]

On 2-Apr-08, at 3:33 PM, Jason Orendorff wrote:
> On Wed, Apr 2, 2008 at 5:08 PM, Mike Klaas <mike.klaas at gmail.com>  
> wrote:
>> ...and the majority of these cases would work fine with views (input
>> to sorted(), etc).
>
> Suppose "the majority" here means 36 of the 46 cases.  Then what
> you're saying is, if I write .items() without thinking, there's about
> a 3% chance it won't work (10 out of 339 cases).  Forgive me:  the
> fact that you've gotten it down to 3%, e.g. by making items() return a
> view instead of an iterator, doesn't make me terrifically happy.

I apologize: I wasn't trying to make the point that programmers used  
to the old behaviour can continue willy-nilly using it without  
worrying about the consequences.

Yes, programmers will have to learn the new behaviour; these are among  
the subtleties of the new language.  I suspect that it will be  
mentioned prominently in every "python 3k for 2.X programmers"  
tutorial, and 2to3 can handle this translation safely.

I suspect that most cases will not fail quietly, either:

l = d.keys()
l.sort() # exception
l[0] # exception
etc. (there may be other examples, too, like sliceability)

-Mike