How to integrate a standalone Python script into a Rails application?

Your index method does not work because python --version outputs its version to STDERR, not STDOUT. If you don't need to separate these streams, you may just redirect STDERR to STDOUT:

value = %x(python --version 2>&1)

This call is synchronous, so after running the script (python do_work.py foo bar 2>&1), you should be able to read the files produced by it.

If the script is not able to create the files for some reason, you will now see the exception in the value variable because error messages are usually sent to STDERR.

If you want to separate STDERR from STDOUT, use the Open3 module.

Beware that the script takes some time to run, so the calls may overlap. I would use a queue here to prevent this.

And don't forget to check the data the user enters. Never pass it directly to the script.

It partly depends on the format of the data. If it's not too long and can be rendered directly in the browser, you can just do something like this in a rails controller:

result = `python do_work.py foo bar`render :text => result

And assuming that result is plain ASCII text, the result will go straight to their browser. If the params to do_work.py come from the user you MUST validate them first though, so you don't wind up creating a nasty vulnerability for yourself. Using the system() call would probably be safer in that case.

If you want to send the results back as a file, look at ruby's Tempfile class for creating the file (in a way that won't stick around forever), and rails' send_file and send_data commands for some different options to send back the results that way.

The answer from utapyngo is cover almost all you need to know. I'll answer this part:

incidentally, trying this in irb: %x(python) Brings up the python terminal INSIDE of irb. It will not take params for whatever reason however.

To pass parameters to your python script, simply pass it. Example:

[fotanus@thing ~]$ python a.py args:['a.py'][fotanus@thing ~]$ irb1.8.7 :001 > %x(python a.py foo bar) => "args:\n['a.py', 'foo', 'bar']\n" 

This works on ruby 1.8, 1.9 and 2.0.