Path: csiph.com!usenet.pasdenom.info!weretis.net!feeder4.news.weretis.net!rt.uk.eu.org!newsfeed.xs4all.nl!newsfeed2.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
MIME-Version: 1.0
Sender: zachary.ware@gmail.com
In-Reply-To: <5208EB7E.6030907@Gmail.com>
References: <5206F4AB.8050204@Gmail.com> <mailman.452.1376188442.1251.python-list@python.org> <roy-4A9C13.22431010082013@news.panix.com> <CAPTjJmoA+r3ABByjgMNC-23H0tB95r6S+d04T-KF-3xgbCNSOQ@mail.gmail.com> <5208D625.2000103@Gmail.com> <CAKJDb-P-TEqmGV45dbayaLdqh2nXE_FyLbd4dk7CPpcTsFWciQ@mail.gmail.com> <5208EB7E.6030907@Gmail.com>
From: Zachary Ware <zachary.ware+pylist@gmail.com>
Date: Mon, 12 Aug 2013 10:37:21 -0500
Subject: Re: Am I not seeing the Error?
To: Devyn Collier Johnson <devyncjohnson@gmail.com>
Content-Type: text/plain; charset=UTF-8
Cc: Python Mailing List <python-list@python.org>
Precedence: list
Newsgroups: comp.lang.python
Message-ID: <mailman.502.1376322196.1251.python-list@python.org>
Lines: 72
NNTP-Posting-Host: 2001:888:2000:d::a6
Xref: csiph.com comp.lang.python:52419

On Mon, Aug 12, 2013 at 9:04 AM, Devyn Collier Johnson
<devyncjohnson@gmail.com> wrote:
>
> Zachary, are you, Ned, and Terry trying to say the syntax should be
>
> job = multiprocessing.Process(func1(), func2())
>
> not
>
> job = multiprocessing.Process(func1(); func2())
>

Basically, yes.  The first option there is equivalent to this:

    func_returns = (func1(), func2())

    job = multiprocessing.Process(*func_returns)

The second option is equivalent to this:

    job = multiprocessing.Process(func1()

    func2())

...which is actually several different syntax errors, depending on how
you look at it.  Semi-colon is only ever used in Python as a
substitute for \n-plus-some-spaces.  And, since in your original
example, your semi-colons are inside parenthesis, they really have no
effect at all due to implicit line continuation within parens.  So
your original line:

JOB_WRITEURGFILES =
multiprocessing.Process(write2file('./mem/ENGINE_PID', ENGINEPID);
write2file(SENTEMPPATH, ''); write2file(INPUTMEM, ''));
JOB_WRITEURGFILES.start()

is really:

    JOB_WRITEURGFILES =
multiprocessing.Process(write2file('./mem/ENGINE_PID', ENGINEPID)
write2file(SENTEMPPATH, '') write2file(INPUTMEM, ''))

    JOB_WRITEURGFILES.start()

It should be obvious now that the syntax error comes from not
separating the arguments to Process.

Trying to read between the lines a little here, I don't think you have
quite figured out how multiprocessing.Process works; that first option
above will only work if func1 returns None and func2 returns a
callable object and the second has no hope.  I think this is more
along the lines of what you're really after:

    def process_func():
        func1()
        func2()

    if __name__ == '__main__':
        job = multiprocessing.Process(target=process_func) # note: no
() after process_func!
        job.start()

I'd suggest giving the multiprocessing.Process docs [0] a good
read-through.  Keep in mind that Process is just a type like any other
(str, int, list, etc.), and calling its constructor is subject to the
same rules as any other function call.


-- 
Zach

[0] http://docs.python.org/3/library/multiprocessing#the-process-class