At the very least PythonLauncher should not be the default for opening 
python files, and should actively warn against being the default 
(basicly reversing the current default).

When PythonLauncher is the default application for .py files double-
clicking a .py file, or opening it from Mail.app will run the script. 
This is not what I'd expect when opening a source file and is risky when 
this happens accidently.

There are several ways for running python scripts by double-clicking on 
them. Two examples:

* Use py2app to create an .app bundle

* Give the script a ".command" suffix and a '#!/usr/bin/python' prefix.

Both result in "files" where it is clear that opening them will result 
in code execution.