[Python-3000] Iterators for dict keys, values, and items == annoying :)

[Ian Bicking]

Robert Brewer wrote:
> Guido van Rossum:
> 
>>>I've read and re-read Jim's message, and I'm not
>>>sure I understand it. It seems he's working in
>>>an interactive session but I'm not sure I
>>>understand the problem he has with adding list()
>>>around an expression
> 
> 
> Jim Fulton wrote:
> 
>>It's a hassle.
>>...
>>I'd be interested to hear if other people who have experience working
>>with ZODB BTrees have been as annoyed as I've been.
> 
> 
> It is a hassle. I recently changed my ORM's API from returning iterators
> to lists based on similar user feedback (and I could have sworn I
> already made this comment on this issue, but I can't find it now). That
> experience hints to me that any interface that prefers iterators over
> lists is going to be resisted; builtins doubly so.

This has been my personal experience with the iterators in SQLObject as 
well.  The fact that an empty iterator is true tends to cause particular 
problems in that case, though I notice iterkeys() acts properly in this 
case; maybe part of the issue is that I'm actually using iterables 
instead of iterators, where I can't actually test the truthfulness.

Another issue I have with generators (and hence iterators) is the 
uselessness of repr() on them.  This causes a lot of list() invocations 
as well, which works with interactive testing, but fails badly with 
print statements (where you have to do another run with list() around it 
-- but that itself causes problems when exhausting the iterator 
introduces a new bug).

-- 
Ian Bicking  /  ianb at colorstudy.com  /  http://blog.ianbicking.org