46 lines
1.7 KiB
ReStructuredText
46 lines
1.7 KiB
ReStructuredText
``tornado.concurrent`` --- Work with threads and futures
|
|
========================================================
|
|
|
|
.. automodule:: tornado.concurrent
|
|
:members:
|
|
|
|
.. py:class:: Future
|
|
|
|
A ``Future`` encapsulates the result of an asynchronous
|
|
operation. In synchronous applications ``Futures`` are used
|
|
to wait for the result from a thread or process pool; in
|
|
Tornado they are normally used with `.IOLoop.add_future` or by
|
|
yielding them in a `.gen.coroutine`.
|
|
|
|
If the `concurrent.futures` package is available,
|
|
`tornado.concurrent.Future` is simply an alias for
|
|
`concurrent.futures.Future`. Otherwise, we support the same
|
|
interface with a few limitations:
|
|
|
|
* It is an error to call `result` or `exception` before the
|
|
``Future`` has completed.
|
|
* Cancellation is not supported.
|
|
|
|
.. py:method:: result()
|
|
|
|
If the operation succeeded, return its result. If it failed,
|
|
re-raise its exception.
|
|
|
|
.. py:method:: exception()
|
|
|
|
If the operation raised an exception, return the `Exception`
|
|
object. Otherwise returns None.
|
|
|
|
.. py:method:: add_done_callback(fn)
|
|
|
|
Attaches the given callback to the `Future`. It will be invoked
|
|
with the `Future` as its argument when it has finished running
|
|
and its result is available. In Tornado consider using
|
|
`.IOLoop.add_future` instead of calling `add_done_callback`
|
|
directly.
|
|
|
|
.. py:method:: done()
|
|
|
|
Returns True if the future has finished running and its
|
|
`result` and `exception` methods are available.
|