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

[Ian Bicking]

Ian Bicking wrote:
> Coming back around to the idea of implementing __getitem__ and such, I 
> suppose a list-like iterator wrapper could be useful.  That would 
> consume and retain the results of the iterator lazily to satisfy the 
> things done to the object.  That would be kind of interesting; I 
> implemented several such methods on the select result object in 
> SQLObject for that purpose, and that aspect actually works pretty well. 
>   There's some predictability problems, though.  bool(obj) would only 
> have to consume one item, but len(obj) would consume the entire thing, 
> and usually len() is a pretty innocuous function to use.
> 
> If this was done, it would be nice if an iterator could give hints, like 
> a faster implementation of __len__ than the fallback behavior that only 
> can use .next().

BTW, I actually like the view idea better, though in some ways they are 
similar -- listish(iterator) is kind of like a list-like view on an 
iterator, like dict.keys() would be a multiset-like view of a 
dictionary's keys.

As a generalized concepts views could be pretty neat and expansive.

A downside is mistranslations of old code will lead to very hard bugs, 
as .keys() currently makes a copy.  Though if the new objects aren't 
quite the same as lists -- e.g., implementing .add() instead of 
.append() -- then maybe that won't be so bad.

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