Source code for traits_futures.background_iteration

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"""
Background task that sends results from an iteration.
"""

from traits.api import Callable, Dict, Event, HasStrictTraits, Str, Tuple

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

#: Message sent whenever the iteration yields a result.
#: The message argument is the result generated.
GENERATED = "generated"


[docs] class IterationTask(BaseTask): """ Iteration to be executed in the background. """ def __init__(self, callable, args, kwargs): self.callable = callable self.args = args self.kwargs = kwargs
[docs] def run(self): iterable = iter(self.callable(*self.args, **self.kwargs)) while True: if self.cancelled(): return None try: result = next(iterable) except StopIteration as e: # If the iteration returned a value, the StopIteration # exception carries that value. Return it. return e.value self.send(GENERATED, result) # Don't keep a reference around until the next iteration. del result
[docs] class IterationFuture(BaseFuture): """ Foreground representation of an iteration executing in the background. """ #: Event fired whenever a result arrives from the background #: iteration. result_event = Event() # Private methods ######################################################### def _process_generated(self, result): self.result_event = result
[docs] @ITaskSpecification.register class BackgroundIteration(HasStrictTraits): """ Object representing the background iteration to be executed. """ #: The callable to be executed. This should return something iterable. callable = Callable() #: Positional arguments to be passed to the callable. args = Tuple() #: Named arguments to be passed to the callable. kwargs = Dict(Str())
[docs] 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 : IterationFuture Future object that can be used to monitor the status of the background task. """ return IterationFuture(_cancel=cancel)
[docs] def task(self): """ Return a background callable for this task specification. Returns ------- task : IterationTask Callable accepting arguments ``send`` and ``cancelled``. The callable can use ``send`` to send messages and ``cancelled`` to check whether cancellation has been requested. """ return IterationTask( callable=self.callable, args=self.args, kwargs=self.kwargs, )
[docs] def submit_iteration(executor, callable, *args, **kwargs): """ Submit an iteration 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 returning an iterator when called with the given arguments. 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 : IterationFuture Object representing the state of the background iteration. """ task = BackgroundIteration(callable=callable, args=args, kwargs=kwargs) return executor.submit(task)