Eclipse plugin that just runs a python script
You can already create an External Launch config from Run>External Tools>External Tools Configurations.  You are basically calling the program from eclipse.  Any output should then show up in the eclipse Console view.  External launch configs can also be turned into External Builders and attached to projects.
If you are looking to run your python script within your JVM then you need a implementation of python in java ... is that what you are looking for?
I want to generate an Eclipse plugin that just runs an existing Python script with parameters.
While this sounds very simple, I don't think it's easy to implement. I can generate a Eclipse plugin. My issue is not how to use PDE. But:

can I call the existing Python script from Java, from an Eclipse plugin?
it needs to run from the embedded console with some parameters

Is this reasonably easy to do? And I don't plan to reimplement it in any way. Calling it from command-line works very well. My question is: can Eclipse perform this, too?
Best,
Marius