Re: Pickle based workflow - looking for advice

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Date	Tue, 14 Apr 2015 23:45:41 +1000
Subject	Re: Pickle based workflow - looking for advice
From	Chris Angelico <rosuav@gmail.com>
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On Tue, Apr 14, 2015 at 11:08 PM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> On Tue, 14 Apr 2015 05:58 pm, Fabien wrote:
>
>> On 14.04.2015 06:05, Chris Angelico wrote:
>>> Not sure what you mean, here. Any given file will be written by
>>> exactly one process? No possible problem. Multiprocessing within one
>>> application doesn't change that.
>>
>> yes that's what I meant. Thanks!
>
> It's not that simple though. If you require files to be written in precisely
> a certain order, then parallel processing requires synchronisation.
>
> Suppose you write A, then B, then C, then D, each in it's own process (or
> thread). So the B process has to wait for A to finish, the C process has to
> wait for B to finish, and so on. Otherwise you could find yourself with C
> reading the data from B before B is finished writing it.

Sure, which is a matter of writer/reader conflicts on a single file -
nothing to do with "writing multiple files simultaneously" which was
the question raised.

ChrisA

Thread

Pickle based workflow - looking for advice Fabien <fabien.maussion@gmail.com> - 2015-04-13 16:58 +0200
  Re: Pickle based workflow - looking for advice Devin Jeanpierre <jeanpierreda@gmail.com> - 2015-04-13 11:45 -0400
    Re: Pickle based workflow - looking for advice Fabien <fabien.maussion@gmail.com> - 2015-04-13 19:39 +0200
  Re: Pickle based workflow - looking for advice Robin Becker <robin@reportlab.com> - 2015-04-13 16:53 +0100
  Re: Pickle based workflow - looking for advice Dave Angel <davea@davea.name> - 2015-04-13 12:25 -0400
    Re: Pickle based workflow - looking for advice Fabien <fabien.maussion@gmail.com> - 2015-04-13 19:30 +0200
  Re: Pickle based workflow - looking for advice Peter Otten <__peter__@web.de> - 2015-04-13 19:08 +0200
    Re: Pickle based workflow - looking for advice Fabien <fabien.maussion@gmail.com> - 2015-04-13 19:35 +0200
      Re: Pickle based workflow - looking for advice Chris Angelico <rosuav@gmail.com> - 2015-04-14 14:05 +1000
        Re: Pickle based workflow - looking for advice Fabien <fabien.maussion@gmail.com> - 2015-04-14 09:58 +0200
          Re: Pickle based workflow - looking for advice Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-14 23:08 +1000
            Re: Pickle based workflow - looking for advice Chris Angelico <rosuav@gmail.com> - 2015-04-14 23:45 +1000
              Re: Pickle based workflow - looking for advice Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-15 00:14 +1000
                Re: Pickle based workflow - looking for advice Chris Angelico <rosuav@gmail.com> - 2015-04-15 00:30 +1000

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