class alphatwirl.concurrently.CommunicationChannel(dropbox)[source]

A communication channel with workers in other processes.

(This docstring is outdated.)

You can send tasks to workers through this channel. The workers, running in other processes, execute the tasks in the background. You can receive the results of the tasks also through this channel.

An instance of this class can be created with two optional arguments: nprocesses, the number of workers to be created, and progressMonitor:

progressBar = ProgressBar()
progressMonitor = BProgressMonitor(progressBar)
channel = CommunicationChannel(nprocesses=10, progressMonitor=progressMonitor)

Workers will be created when begin() is called:


In begin(), this class gives each worker a progressReporter, which is created by the progressMonitor.

Now, you are ready to send a task. A task is a function or any object which is callable and picklable. A task can take any number of arguments. If a task takes a named argument progressReporter, the worker will give the progressReporter to the task. A value that a task returns is the result of the task and must be picklable. For example, an instance of EventLoop can be a task. You can send a task with the method put:

channel.put(task1, 10, 20, A=30)

Here, 10, 20, A=30 are the arguments to the task.

This class sends the task to a worker. The worker which receives the task will first try to call the task with the progressReporter in addition to the arguments. If the task doesn’t take the progressReporter, it calls only with the arguments.

You can send multiple tasks:

channel.put(task3, 100, 200)
channel.put(task4, A='abc')

They will be executed by workers.

You can receive the results of the tasks with the method receive():

results = channel.receive()

This method will wait until all tasks are finished. If a task gives a progressReport to the progressReporter, the report will be used, for example, to update progress bars on the screen.

When all tasks end, results will be returned. The return value results is a list of results of the tasks. They are sorted in the order in which the tasks are originally put.

After receiving the results, you can put more tasks:


And you can receive the results of them:

results = channel.receive()

If there are no more tasks to be done, you should call the method end:


This will end all background processes.



put(task, *args, **kwargs)