Python threading/multiprocessing issue.

Lee Harr missive at
Fri Jul 15 16:55:14 EDT 2011

> I'm working on a tool that runs a number of process is separate thread.
> I've, up to this point, been using threading.Thread, but from what I
> read multiprocess will allow multiple processors to be used
>  From the python docs on multiprocessing.
><Due to this, the multiprocessing module allows the programmer to fully
>         leverage multiple processors on a given machine.>
> I have run into an issue when modifying the thread object from the run
> method. Threading.thread allows me to change an attribute in the run
> method and it hold while multiprocessing.Process loses it.

I am not a multiprocessing expert, but I think the problem you
are having is that Process is running your code in a separate
process, so there is no way you could see those object changes
in your main line code.

In other words, Process is not an exact replacement for Thread.
If you need to communicate between the different parts, you
would want to use the abstractions provided by Queue or Pipe.

Keep reading down the multiprocessing page in the docs until
you get to "Exchanging objects between processes":

"Sharing state between processes" seems like it will be especially
relevant to what you are doing:

Basically, it says "don't do that"  :o)

> Here is an example illustrating the inconsistency that I've seen.

One thing that would help here is a sample of what output
you get from your code, and what you were hoping to get.


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