earwax.promises.threaded_promise module

Provides the ThreadedPromise class.

class earwax.promises.threaded_promise.ThreadedPromise(thread_pool: concurrent.futures._base.Executor, func: Optional[Callable[[...], T]] = None, future: Optional[concurrent.futures._base.Future] = None)

Bases: earwax.promises.base.Promise

A promise that a value will be available in the future.

Uses an Executor subclass (like ThreadPoolExecutor, or ProcessPoolExecutor for threading).

You can create this class directly, or by using decorators.

Here is an example of the decorator syntax:

from concurrent.futures import ThreadPoolExecutor

promise: ThreadedPromise = ThreadedPromise(ThreadPoolExecutor())

@promise.register_func
def func() -> None:
    # Long-running task...
    return 5

@promise.event
def on_done(value: int) -> None:
    # Do something with the return value.

@promise.event
def on_error(e: Exception) -> None:
    # Do something with an error.

@promise.event
def on_finally():
    print('Done.')

promise.run()

Or you could create the promise manually:

promise = ThreadedPromise(
    ThreadPoolExecutor(), func=predefined_function
)
promise.event('on_done')(print)
promise.run()

Note the use of Pyglet’s own event system.

Variables:

• thread_pool – The thread pool to use.
• func – The function to submit to the thread pool.
• future – The future that is running, or None if the run() method has not yet been called.

cancel() → None

Try to cancel self.future.

If There is no future, RuntimeError will be raised.

check(dt: float) → None

Check state and react accordingly.

Checks to see if self.future has finished or not.

If it has, dispatch the on_done() event with the resulting value.

If an error has been raised, dispatch the on_error() event with the resulting error.

If either of these things have happened, dispatch the on_finally() event.

Parameters:dt –

The time since the last run.

This argument is required by pyglet.clock.schedule.

register_func(func: Callable[[...], T]) → Callable[[...], T]

Register promise function.

Registers the function to be called by the run() method.

Parameters:func – The function to use. Will be stored in self.func.

run(*args, **kwargs) → None

Start this promise running.

The result of calling submit on self.thread_pool will be stored on self.future.

If this instance does not have a function registered yet, RuntimeError will be raised.

Parameters:

• args – The extra positional arguments to pass along to submit.
• kwargs – The extra keyword arguments to pass along to submit.