This is Windows only (see the Python documentation at http://www.python.org).

Other systems may not allow something like this (for security reasons).
If you know whitch program should handle your datafile, perhaps you can use a system call to exec the application.

If you want to show something that a webbrowser can handle, look into the Python docu. There is a "webbrowser" module that runs on any OS where Python is available.

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