There is a simple way to do it.
In the Run menu, you can see options like "Lunch in firefox" and more.
These options are written in a file called shortcuts.xml, located in the folder where you installed NP++.
Open this file, and inside <UserDefinedCommands> you'll find this row:
- <Command name="launch in Firefox" Ctrl="yes" Alt="yes" Shift="yes" Key="88">firefox "$(FULL_CURRENT_PATH)"</Command>
All you need to do is copy this line and change some things. Then you'll have something like this:
- <Command name="Run with Python" Ctrl="no" Alt="no" Shift="yes" Key="112">python "$(FULL_CURRENT_PATH)"</Command>
(I chose Shift+F1, but you can choose any keys you like.)
Reopen NP++, and now it's easy and nice to run any python file strait from the editor.
More information on things like this in NP++: http://notepad-plus.wiki.sourceforge.net/Run