Raymond Hettinger added the comment:
Sorry, I'm going to reject this one.
Looking at implementations in other languages,
I see that this is almost never needed.
It is not worth complicating the API which
is currently very simple.
Also, there is an issue in that the semantics
are not self-evid
New submission from ipatrol :
Yes, I know, this was proposed with builtin lists years before. But I can't
help but think that at least for pop-append oriented deques, a popping analogue
to extend would make use of deques in iterators easier. It should ideally
return an iterator, possibly with