Author: R Oudkerk

# Python processing

Author: | R Oudkerk
Contact: | roudkerk at users.berlios.de
Url: | http://developer.berlios.de/projects/pyprocessing
Version: | 0.52
Licence: | BSD Licence

`processing` is a package for the Python language which supports the spawning of processes using the API of the standard library's `threading` module. It runs on both Unix and Windows.

Features:

- Objects can be transferred between processes using pipes or multi-producer/multi-consumer queues.
- Objects can be shared between processes using a server process or (for simple data) shared memory.
- Equivalents of all the synchronization primitives in `threading` are available.
- A `Pool` class makes it easy to submit tasks to a pool of worker processes.

# Links

- Documentation
- Installation instructions
- Changelog
- Acknowledgments
- BSD Licence

The project is hosted at

- http://developer.berlios.de/projects/pyprocessing

The package can be downloaded from

- http://developer.berlios.de/project/filelist.php?group_id=9001 or
- http://pypi.python.org/pypi/processing

# Examples

The `processing.Process` class follows the API of `threading.Thread`. For example

    from processing import Process, Queue

    def f(q):
        q.put('hello world')

    if __name__ == '__main__':
        q = Queue()
        p = Process(target=f, args=[q])
        p.start()
        print q.get()
        p.join()

Synchronization primitives like locks, semaphores and conditions are available, for example

    >>> from processing import Condition
    >>> c = Condition()
    >>> print c
    <Condition(<RLock(None, 0)>), 0>
    >>> c.acquire()
    True
    >>> print c
    <Condition(<RLock(MainProcess, 1)>), 0>

One can also use a manager to create shared objects either in shared memory or in a server process, for example

    >>> from processing import Manager
    >>> manager = Manager()
    >>> l = manager.list(range(10))
    >>> l.reverse()
    >>> print l
    [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
    >>> print repr(l)
    <Proxy[list] object at 0x00E1B3B0>

Tasks can be offloaded to a pool of worker processes in various ways, for example

    >>> from processing import Pool
    >>> def f(x): return x*x
    ...
    >>> p = Pool(4)
    >>> result = p.mapAsync(f, range(10))
    >>> print result.get(timeout=1)
    [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]