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

[Taro Ogawa]

[Originally misposted to python-dev]
Nick Coghlan <ncoghlan <at> gmail.com> writes:
> There are three big use cases:
>    dict.keys
>    dict.values
>    dict.items
> Currently these all return lists, which may be expensive in terms of copying.
> They all have iter* variants which while memory efficient, are far less 
> convenient to work with.
<delurk>
Is there any reason why they can't be view objects - a dictionary has keys, 
has values, has items - rather than methods returning view objects:
    for k in mydict.keys:
        ...
    for v in mydict.values:
        ...
    for k, v in mydict.items:
        ...
For backward compatibility with Py2.x, calling them would raise a 
DeprecationWarning and return a list.  This could even be introduced in 2.x 
(with a PendingDeprecationWarning instead?).

Cheers, -T.