On Tue, Dec 10, 2019 at 03:50:19PM -0600, Tim Peters wrote:
> For me, most of the time, it's to have an obvious, uniform way to
> spell "non-destructively pick an object from a container (set, dict,
> list, deque, heap, tuple, custom tree class, ...)". I don't even have
> iterators in mind then, except as an implementation detail.
You can't *non-destructively* pick the first (or next, or any) element
of an iterator. Doing so changes the state of the iterator and consumes
the element you just retrieved.
Given a container, we have:
assert first(container) is first(container)
but the same doesn't apply to iterators.
It sounds to me that what you actually want is an analogue to
Mapping.get that applies to all containers and sequences and leaves
iterators completely out of it.
a = [2, 4, 8, 16]
a.get(0) # returns 2
a.get(100) # returns None by default
I could completely get behind this idea! The only tricky part is the
"index" isn't well-defined for mappings and sets, or tree-like
containers.
--
Steven
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