bpo-35118: Improve docs regarding indexing (GH-10265)

Doc/library/collections.rst

@@ -531,9 +531,9 @@ or subtracting from an empty counter.
 
 In addition to the above, deques support iteration, pickling, ``len(d)``,
 ``reversed(d)``, ``copy.copy(d)``, ``copy.deepcopy(d)``, membership testing with
-the :keyword:`in` operator, and subscript references such as ``d[-1]``.  Indexed
-access is O(1) at both ends but slows to O(n) in the middle.  For fast random
-access, use lists instead.
+the :keyword:`in` operator, and subscript references such as ``d[0]`` to access
+the first element.  Indexed access is O(1) at both ends but slows to O(n) in
+the middle.  For fast random access, use lists instead.
 
 Starting in version 3.5, deques support ``__add__()``, ``__mul__()``,
 and ``__imul__()``.

Doc/library/queue.rst

@@ -275,4 +275,5 @@ SimpleQueue Objects
 
    :class:`collections.deque` is an alternative implementation of unbounded
    queues with fast atomic :meth:`~collections.deque.append` and
-   :meth:`~collections.deque.popleft` operations that do not require locking.
+   :meth:`~collections.deque.popleft` operations that do not require locking
+   and also support indexing.