.. class:: Future

    ``tornado.concurrent.Future`` is an alias for `asyncio.Future`.

    In Tornado, the main way in which applications interact with
    ``Future`` objects is by ``awaiting`` or ``yielding`` them in
    coroutines, instead of calling methods on the ``Future`` objects
    themselves. For more information on the available methods, see
    the `asyncio.Future` docs.

    .. versionchanged:: 5.0

       Tornado's implementation of ``Future`` has been replaced by
       the version from `asyncio` when available.

       - ``Future`` objects can only be created while there is a
         current `.IOLoop`
       - The timing of callbacks scheduled with
         ``Future.add_done_callback`` has changed.
       - Cancellation is now partially supported (only on Python 3)
       - The ``exc_info`` and ``set_exc_info`` methods are no longer
         available on Python 3.