Source code for traits_futures.background_call

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#
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# license included in LICENSE.txt and may be redistributed only under
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"""
Background task consisting of a simple callable.
"""
from traits.api import Callable, Dict, HasStrictTraits, Str, Tuple

from traits_futures.base_future import BaseFuture, BaseTask
from traits_futures.i_task_specification import ITaskSpecification


class CallTask(BaseTask):
    """
    Wrapper around the actual callable to be run. This wrapper provides the
    task that will be submitted to the concurrent.futures executor
    """

    def __init__(self, callable, args, kwargs):
        self.callable = callable
        self.args = args
        self.kwargs = kwargs

    def run(self):
        return self.callable(*self.args, **self.kwargs)


class CallFuture(BaseFuture):
    """
    Object representing the front-end handle to a background call.
    """


@ITaskSpecification.register
class BackgroundCall(HasStrictTraits):
    """
    Object representing the background call to be executed.
    """

    #: The callable to be executed.
    callable = Callable()

    #: Positional arguments to be passed to the callable.
    args = Tuple()

    #: Named arguments to be passed to the callable.
    kwargs = Dict(Str())

    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 : CallFuture
            Future object that can be used to monitor the status of the
            background task.
        """
        return CallFuture(_cancel=cancel)

    def task(self):
        """
        Return a background callable for this task specification.

        Returns
        -------
        CallTask
            Callable accepting arguments ``send`` and ``cancelled``. The
            callable can use ``send`` to send messages and ``cancelled`` to
            check whether cancellation has been requested.
        """
        return CallTask(
            callable=self.callable,
            args=self.args,
            kwargs=self.kwargs,
        )


def submit_call(executor, callable, *args, **kwargs):
    """
    Submit a simple call to an executor.

    Parameters
    ----------
    executor : TraitsExecutor
        Executor to submit the task to. This argument should always be passed
        by position rather than by name. Future versions of the library may
        enforce this restriction.
    callable
        Callable to execute in the background. This argument should always be
        passed by position rather than by name. Future versions of the library
        may enforce this restriction.
    *args
        Positional arguments to pass to the callable.
    **kwargs
        Named arguments to pass to the callable.

    Returns
    -------
    future : CallFuture
        Object representing the state of the background call.
    """
    task = BackgroundCall(callable=callable, args=args, kwargs=kwargs)
    return executor.submit(task)