executing multiple functions in background simultaneously

Michele Simionato michele.simionato at gmail.com
Wed Jan 14 06:29:29 CET 2009


On Jan 14, 2:02 am, Catherine Moroney
<Catherine.M.Moro... at jpl.nasa.gov> wrote:
> Hello everybody,
>
> I know how to spawn a sub-process and then wait until it
> completes.  I'm wondering if I can do the same thing with
> a Python function.
>
> I would like to spawn off multiple instances of a function
> and run them simultaneously and then wait until they all complete.
> Currently I'm doing this by calling them as sub-processes
> executable from the command-line.  Is there a way of accomplishing
> the same thing without having to make command-line executables
> of the function call?
>
> I'm primarily concerned about code readability and ease of
> programming.  The code would look a lot prettier and be shorter
> to boot if I could spawn off function calls rather than
> subprocesses.
>
> Thanks for any advice,
>
> Catherine

There is an example explaining how to implement exactly
this use case in the documentation of my decorator module:
http://pypi.python.org/pypi/decorator/3.0.0#async
The Async decorator works both with threads and with multiprocessing.
Here is an example of printing from multiple processes
(it assumes you downloaded the tarball of the decorator
module, documentation.py is the file containing the documentation
and the Async decorator; it also assumes you have the multiprocessing
module):

$ cat example.py
import os, multiprocessing
from documentation import Async

async = Async(multiprocessing.Process)

@async
def print_msg():
  print 'hello from process %d' % os.getpid()

for i in range(3):
    print_msg()

$ python example.py
hello from process 5903
hello from process 5904
hello from process 5905



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