[PySide] using QProcess to run python function
Frank Rueter | OHUfx
frank at ohufx.com
Fri Jan 24 04:39:37 CET 2014
I might have lead you on a wild goose chase:
I have working python code that calls external process (using
subprocess.Popen) and now I am writing a UI for it.
To get started I wrote a simple UI that connected to one of those
external programs directly to establish the frame work for the new code
and figure out how to properly handle the external programs stdout and
stderr, be able to display things and cancel it from within my UI.
After getting all that to work I thought all I have to do is connect to
my actual python code rather than directly to the external program, and
that is where I assumed QProcess to be able to do this, when instead I
shuold simlpy switch to use QThread and reire that to give me access to
stdout, be able to cancel it etc.
So what I am trying to do is simply this:
PySide UI --- calls --> pure python --- calls --> pure python --- calls
--> external program
With the stdout of external program and the pure python apps being piped
into the PySide UI for processing.
Sorry if I wasted your time :/
frank
On 24/01/14 16:22, Sean Fisk wrote:
>
> Are you wanting to use |QProcess| or |QThread| because your GUI is
> blocked (aka frozen, not responding)?
>
>
>
> --
> Sean Fisk
>
>
> On Thu, Jan 23, 2014 at 10:06 PM, Frank Rueter | OHUfx
> <frank at ohufx.com <mailto:frank at ohufx.com>> wrote:
>
> Actually, it's dawning on me that QProcess may be the wrong thing
> to use here, I guess I should consider using QThread instead,
> seeing all the code I need to run is Python anyway!?
> I was just experimented with QProcess running the external
> programs directly for testing so I kinda got stuck in thinking
> this is the way to go (since I got it all wired up to my UI already).
>
>
>
>
>
> On 24/01/14 15:42, Frank Rueter | OHUfx wrote:
>> Thanks Sean and Ryan,
>>
>> I'm still not quite clear on how this ties into QProcess.start()
>> 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'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
>>> <frank at ohufx.com <mailto:frank at 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
>>>> <frank at ohufx.com <mailto:frank at 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
>>>>
>>>> _______________________________________________
>>>> PySide mailing list
>>>> PySide at qt-project.org <mailto:PySide at qt-project.org>
>>>> http://lists.qt-project.org/mailman/listinfo/pyside
>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> 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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>>>
>>
>>
>>
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