python - Opening file - Performing a function

Question

I was wondering if someone could give me a direction on how to give functions to a file... This is a bit hard to explain, so I'll try my best.
Let's say I have an application (using wxPython) and let's say that I have a file. Now this file is assigned to open with the application. So, I double-click the file and it opens the application. Now my question is, what would have to be written on the file to, for example, open up a dialog? So we double-click the file and it opens a dialog on the application?

PS: I know that I have first to associate the program with a certain file type to double-click it, but thats not the question.

Answer 1

AFAIK most platforms just call the helper app with the file you clicked on as an argument, so your filepath will be in sys.argv[1]