And of course I ran into trouble :-D
Here is my test code trying to ustilise QThread:
http://pastebin.com/Q26Q9M1M

The basic structure seems to work (the extra thread and the main thread are running at the same time), but my UI does not update according to the signal connections, e.g.: When the thread starts the progress bar is supposed to be shown, the "Do Work" button should be disabled, the "Cancel" button disabled.
etc.

I tried calling self.update() in the MainUI when the thread starts but to no avail.
I'm sure I'm missing something obvious as usual.

I tried to adhere to what I learnt on this list about threading and avoid sub-classing QThread.

Cheers,
frank

On 24/01/14 17:41, Frank Rueter | OHUfx wrote:
Great, thanks. I shall adjust my code.
I am interested in seeing how you would go about it, but let me have a go from scratch, I will be able to understand things much better afterwards :)

Cheers,
frank


On 24/01/14 17:38, Sean Fisk wrote:
On Thu, Jan 23, 2014 at 10:44 PM, Frank Rueter | OHUfx <fr...@ohufx.com <mailto:fr...@ohufx.com>> wrote:

    Much appreciated but as I mentioned, I think I jumped the gun
    with my post and should be using QThread to hook the python code
    to my QProgressBar and debug output window (QTextEdit).

That would be a correct way to use |QProgressBar|. Also, for subprocess output, I would consider using |QPlainTextEdit| instead of |QTextEdit| as is is more performant with high amounts of text.

If you are interested, I just wrote an asynchronous module for PySide for the project on which I am currently working. It is based on Python's futures <http://pythonhosted.org/futures/> module and works great with Qt's signals/slots. Although the project is primarily closed-source, I would be happy to share the async implementation with you. I don't know if would fit your needs, but for us it's much easier than manually spawning |QThread|s and even easier than |QThreadPool|.

Good luck!

    I will investigate that now



    On 24/01/14 16:08, Sean Fisk wrote:
    On Thu, Jan 23, 2014 at 9:42 PM, Frank Rueter | OHUfx
    <fr...@ohufx.com <mailto:fr...@ohufx.com>> wrote:

        Thanks Sean and Ryan,

        I'm still not quite clear on how this ties into QProcess.start()


    It doesn't tie in with |QProcess| at all. We're advising to
    avoid using that :)

        I do have a if __name__ ... block in the script in question.
        An example would certainly be awesome, but if it's less
        hassle, explaining how your and Ryan's advise helps use
        QProcess on a python module might already suffice. Maybe a
        simlpe example says it all though?!


    I will whip up a simple example for you, but it might take a few
    hours (lots of stuff to do right now).

        I'm not using python 3 btw

        Thanks guys for your help!!

        frank


        On 24/01/14 15:33, Sean Fisk wrote:

        Hi Frank,

        You should definitely avoid calling Python as a subprocess
        if you can. As far as Ryan's example, I agree with the |if
        __name__...| but I think that using the |imp| module is a
        bit overkill. I would recommend using Setuptool's
        |entry_points| keyword
        
<http://pythonhosted.org/setuptools/setuptools.html#automatic-script-creation>.
        Or distutils' |scripts| keyword
        
<http://docs.python.org/2/distutils/setupscript.html#installing-scripts>,
        if you must.

        An example of a well-known Python package which does this
        is Pygments
        <https://bitbucket.org/birkenfeld/pygments-main>, which has
        a large "library" component but also comes with the
        |pygmentize| command-line script. The Pygments codebase is
        pretty large, so if you would like me to whip up a simpler
        example I'd be glad to do so.

        Cheers,

        --
        Sean Fisk


        On Thu, Jan 23, 2014 at 9:17 PM, Frank Rueter | OHUfx
        <fr...@ohufx.com <mailto:fr...@ohufx.com>> wrote:

            Sorry if I'm being thick, but I'm not quite
            understanding how this helps to connect a python
            function to qprocess?! All your code does is execute
            the script, right?!
            I can already call myscript.main() straight up, but
            maybe I'm missing the point as I'm unfamiliar with the
            imp module.

            Let me elaborate a little bit more:
            myscript.main() calls a bunch of other python scripts
            that (directly or through other scripts again) execute
            external programs to do some conversion work. Those
            external programs spit out their progress to stdout
            which I can see fine when I run myscript.main()
            manually in a python terminal.

            Now I need run myscript.main() via QProcess and grab
            stdout to do be able to show a progress bar as well as
            show stdout and stderr in a debug window inside my QT code.


            Cheers,
            frank




            On 24/01/14 14:58, Ryan Gonzalez wrote:
            If you put an "if __name__ == '__main__'" and a main
            functions, you could always import the script from the
            GUI frontend. Example:

            myscript.py

            def main(argv):
            do_cool_stuff()
                return 0

            if __name__ == '__main__':
            sys.exit(main(sys.argv))

            mygui.py(Python 2):

            import imp

            ...

            main = imp.load_module('myscript',
            *imp.find_module('myscript'))

            main.main(my_argv)

            mygui.py(Python 3):

            import importlib.machinery

            main =
            importlib.machinery.SourceFileLoader('myscript',
            'myscript.py').load_module('myscript')

            main.main(my_argv)


            On Thu, Jan 23, 2014 at 7:48 PM, Frank Rueter | OHUfx
            <fr...@ohufx.com <mailto:fr...@ohufx.com>> wrote:

                Hi all,

                I got a little code design question:

                I have a python script that does a lot of file
                processing/converting/uploading etc and I'd like
                to write a decent
                interface for it now.
                The main goal is to be able to show the user
                detailed info about the
                current step and progress as well as clean up
                properly in case the whole
                thing is cancelled.

                My existing python code needs to stay independent
                of QT so any
                application that supports python can use it.
                I am wondering now how to best connect the python
                script and the PySide
                code. Should I just run the script as an argument
                to the python
                interpreter like I would with any other program? E.g.:

                process = QtCore.QProcess(self)
                process.start(<path_to_python>,
                <path_to_python_script>)

                As simple as this seems, it feels odd to use
                python to call itself as an
                external program.


                I'm happy to go that way but am curious how others
                are doing this?!

                Cheers,
                frank

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-- Ryan
            If anybody ever asks me why I prefer C++ to C, my
            answer will be simple: "It's
            becauseslejfp23(@#Q*(E*EIdc-SEGFAULT. Wait, I don't
            think that was nul-terminated."



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