Using PySP from script

[JolleG]

Hi,

I'm starting to use PySP and so far I have only made runs from the command window. Now I'd like to use PySP from a script, so that I can afterwards process the solution. How would I do this?

Best,
Jonatan

[David Woodruff]

Hi Jonatan,

 If you want to process the solution, then you could write your own "solution writer." There is an example in

pyomo/src/pyomo/pyomo/pysp/plugins/csvsolutionwriter.py

the method for using it (i.e. calling it) is documented in the Getting Started online document.

   Best,

     Dave

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[Jonatan Rantzer]

Hi David and all,

I checked out the CSV soution writer and I guess it would be a possibility either to use it as it is, or to modify it for my purposes. But my follow up question would be: how can I then use it inside a script. I guess it would be something like:

instanceWriter = CSVSolutionWriter(?)

instanceWriter.write(myScenarioTree, myResult)

This question is a part of my more general question: how do I solve a stochastic programming problem from a script and process the solution? I guess I could somehow find out from studying the source code, but I'm hoping to get some guidance, since for the ordinary deterministic optimization problems there was some documentation on how to solve them using own-written scripts.

Thanks for the help,

Jonatan

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[David Woodruff]

Hi Jonatan,

   There is no documentation because the APIs for scripting pysp are not yet stable enough (beyond creating your own output plugin).  Let's take this conversation off-line and see if there is something we can do to help you.

Dave

[Christopher Hagmann]

This is not supported, but the way I do scripting with PySP is to run it in the command line via the script using the `os` module. My code is below:

def command_line(command, tee=False):

    '''

    Run command line commands in Python Script and return stdout as list.

    '''

    stdin,stdout = os.popen2(command)

    stdin.close()

    lines = stdout.readlines()

    stdout.close()

    lines = [line.strip('\n') for line in lines]

    if tee:

        print '\n'.join(lines)

    return lines

EXAMPLE:

>>> command_line('chdir')
['C:\\User\\Chris']

After you get the output, you can write whatever you like to parse the output.

[Jonatan Rantzer]

Thank you for this idea Christopher, it seems like a practical strategy.

Jonatan

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/ Jonatan Rantzer