1) .py file must be in same path with descriptor.xml .
2)Boxee creates a .pyo file after it compiled the code. .pyo file is used in the application. So if you change a piece of code in your .py file. It will not affect your application unless you delete existing .pyo file and restart the application.
3).pyo files can be created if python codes are syntactically correct.
4)Compiling .py files requires some time. So, if your python code is not large enough, just call from your xml file.
5)Your pyhton file need not to be named same as your project.
6)There is only a few application that are using .py files.
7)You need to import your .py file in order to use its content.