Source code for traits_futures.i_task_specification

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"""
Interface for a job specification. The job specification is the object
that the TraitsExecutor knows how to deal with.
"""

import abc


[docs]class IFuture(abc.ABC): """ Interface for futures returned by the executor. This interface can be used to implement new background task types. It represents the knowledge that the executor needs to interact with futures. """
[docs] @abc.abstractmethod def cancel(self): """ Request cancellation of the background task. For a future that has not yet completed and has not previously been cancelled, this method requests cancellation of the associated background task and returns ``True``. For a future that has already completed, or that has previously been cancelled, this method does nothing, and returns ``False``. Returns ------- cancelled : bool True if the task was cancellable and this call requested cancellation, False if the task was not cancellable (in which case this call did nothing). """
[docs] @abc.abstractmethod def receive(self, message): """ Receive and process a message from the task associated to this future. This method is primarily for use by the executors, but may also be of use in testing. Parameters ---------- message : object The message received from the associated task. Returns ------- final : bool True if the received message should be the last one ever received from the paired task. """
[docs]class ITaskSpecification(abc.ABC): """ Specify background task callable and foreground future for a task. An object implementing the ITaskSpecification interface describes how to create a background task and a corresponding foreground future to execute a particular type of background task. It's consumed by the TraitsExecutor when submitting background tasks, and implemented by BackgroundCall, BackgroundIteration and others. """
[docs] @abc.abstractmethod def task(self): """ Return the callable that will be invoked as the background task. This callable should be pickleable and should have the signature task(send, cancelled) Any exception raised while executing the callable, or result returned by the callable, will be recorded in the corresponding future. The ``send`` argument can be used by the background task to send messages back to the main thread of execution. It's a callable that should be called as ``send(message)``, where ``message`` is an arbitrary Python object. The argument to ``send`` should typically be both immutable and pickleable. ``send`` returns no useful result. The ``cancelled`` argument may be used by the background task to check whether cancellation has been requested. When called with no arguments, it returns either ``True`` to indicate that cancellation has been requested, or ``False``. Note that there's no obligation for the background task to check the cancellation status. Returns ------- task : object Callable accepting arguments ``send`` and ``cancelled``. The callable can use ``send`` to send messages and ``cancelled`` to check whether cancellation has been requested. """
[docs] @abc.abstractmethod def future(self, cancel): """ Return a Future for the background task. Parameters ---------- cancel Zero-argument callable, returning no useful result. The returned future's ``cancel`` method should call this to request cancellation of the associated background task. Returns ------- future : IFuture Future object that can be used to monitor the status of the background task. """